Human astronauts are such a bother when it comes to space exploration. The space environment is pretty much the opposite of the conditions that humans evolved for, to the point where an unprotected human exposed to space will die horribly in about ninety seconds flat. Even given oxygen to breath, the human organism is quite insistent on a whole host of demands: food, water, comfortable temperature, gravity, absence of deadly radiation; the list goes on and on.

This is why NASA is so fond of robot space probes. Not only do robots not have any of those requirements, but there also is no problem with sending the probes on suicide one-way missions. Human astronauts would tend to complain about that.

But given organic non-cyborg astronauts, your spacecraft design is going to need a habitat module for the crew to live in, and all sorts of supplies to keep them alive. Since Every Gram Counts, it will be important to use every trick in the book to try and miminize the mass cost of all this.

In NASA-speak:

Environmental Control And Life Support System. The part of your spacecraft or space station that makes a livable environment so the astronauts don't all die horribly in ninety seconds flat.
Controlled (or Closed) Ecological Life Support System. A life support system that recycles air, water, and food indefinitely (given input energy). It can vastly cut down on the payload mass "wasted" on food (given the CELSS penalty mass). Drawback is that it can be tricky to maintain the balance.
Primary (or Portable or Personal) Life Support System. A life support system for a space suit, generally contained in the back-pack.

A useful document with nitty-gritty details about life support Human Integration Design Handbook (warning: 40 MB file). This include info on the minimum volume needed for such tasks as exercise and hygiene, range of safe breathing mixes, temperature, humidity, acceleration limits, fire extinguishers, and related matter.

A useful accounting device for consumables is the "man-day" or "person-day".

If your ship has 30 person-days of food and oxygen, it can support:

  • 30 persons for 1 day (30 / 30 = 1)

  • 15 persons for 2 days (30 / 15 = 2)

  • 3 persons for 10 days (30 / 3 = 10)

  • one person for 30 days (30 / 1 = 30)

...or any other division of 30.

By the same math, a ship with 30 person-days of supplies facing a 10 day mission could support 3 persons (30 / 10 = 3).

So if the exploration ship Arrow-Back becomes marooned in the trackless wastes of unexplored space and is listed as having 20 person-weeks of life support, it makes it really easy for Mr. Selfish to do the arithmetic and figure that he will survive for twenty weeks instead of one if he murders the other 19 crew members. More democratically, if the rescue ship will arrive in 8 days (1.14 weeks), one can calculate that the supplies will stretch for an extra day with 17 crew members (20 / 1.14 = 17.5, round down to 17). The crew draws straws, and the unlucky two who get the short straws have the opportunity to heroically sacrifice themselves so that the rest of the crew may live.

Naturally the kind way to do the math is when initially planning the mission. Multiply the number of crew members by the duration of the mission in days to get the required number of person-days of consumables (and if you are wise you'll add an additional safety margin). Then you can calculate the mass and volume for each vital life-support consumable.

For instance, a 250 day mission with 5 crew would need 1,250 person-days. If food takes up 2.3 kg and 0.0058 m3 per person-day, you multiply by 1,250 to calculate the spacecraft needs to accommodate 2,875 kg and 7.25 m3 for the food supply.


      Human spaceflight is challenging and calls on great personal resources even from professional astronauts. This has always been true, and its truth is not diminished by the fact that we now “routinely” send people into space for six months (or even a year) at a time on the International Space Station (ISS). A sense of the challenges in maintaining human presence in space can be gleaned from a glimpse at the physiological and psychological procedures (countermeasures) in place to maintain health and performance in this demanding environment. We will discuss those in a moment. When people venture further out, in distance and duration—to the Moon, to Mars (in the foreseeable future), and eventually beyond, these countermeasures will be taxed, in some cases beyond their limits. New interventions and conceptualizations will be needed: the enabling of the crew to deal, on its own, with issues that have not been identified before the mission begins. In other words, it is not the countermeasures themselves that will be as important as the mission structure that is put in place to create countermeasures “as needed” when new unexpected circumstances arise. We will discuss how this might be accomplished.

     All of this is challenging enough, but when we then consider journeys not of exploration but of settlement or colonization to destinations that make Mars seem like a close neighbor, we enter a whole new realm of thinking. We assume that human physiology and psychology will be the same, and thus some of the same approaches to maintaining their integrity will still be relevant. However, the range of physical, mental, and emotional stressors will take on a new magnitude, leading to new problems that require new solutions. Extrapolations of solutions from today’s flights will be stretched, hopefully not to the breaking point, but it is clear that new ways of thinking about health and performance will be needed. This will be made especially compelling because many of the foundational aspects of our lives here on Earth—things that we have learned to rely on to the point of taking them for granted—will be left behind forever.

     Explorers on Earth, no matter how difficult the journey, can at least be comforted in being able to breathe fresh air, to experience the sights, sounds, and smells of nature, and even be reassured by the familiar tug of gravity. Extraplanetary settlers will have no such assurance of familiarity, and the resulting stress can have widespread negative consequences if not understood and controlled. This will be exacerbated by the fact that space journeys of today—and in the near future—are undertaken by small groups of select and very highly trained professional astronauts. High standards of motivation, discipline, dedication to duty, and expertise are accepted facts. Larger groups of people that will be needed for journeys of colonization will almost certainly exhibit a much wider range of variability in all these traits. Such diversity can be beneficial in many ways, but in the initial flights of these more ambitious undertakings it is not clear how to balance such diversity with the known successful approach to assembling an astronaut team.

     Let us begin our journey out to the planets of the future with a look at current thinking for astronaut well-being followed by some informed conjectures as to where that might lead us.


To go about systematically addressing the major risks to human health and performance in long-duration spaceflight, it is useful first to delineate these risks. The approach that NASA currently takes is to identify the main spaceflight hazards (environmental conditions) and then determine the specific human risks associated with each hazard (Francisco and Romero 2016).
  1. Hazard: Altered gravity level (in space or on a planet other than Earth)
    1. Spaceflight-induced intracranial hypertension/vision alterations
    2. Renal stone formation
    3. Impaired control of spacecraft/associated systems and decreased mobility due to vestibular/sensorimotor alterations
    4. Bone fracture due to spaceflight-induced changes
    5. Impaired performance due to reduced muscle mass, strength, and endurance
    6. Reduced physical performance capabilities due to reduced aerobic capacity
    7. Adverse health effects due to host-microorganism interactions
  2. Hazard: Hostile and closed environment
    1. Acute and chronic carbon dioxide exposure
    2. Performance decrement and crew illness due to inadequate food/nutrition
    3. Injury from dynamic loads
    4. Injury and compromised performance due to EVA operations
    5. Adverse health and performance effects of celestial dust exposure
    6. Adverse health event due to altered immune response
    7. Reduced crew performance due to hypobaric hypoxia
    8. Performance decrements and adverse health outcomes resulting from sleep loss, circadian desynchronization, and work overload
    9. Reduced crew performance due to inadequate human-system interaction design
    10. Decompression sickness
  3. Hazard: Isolation and confinement
    1. Adverse cognitive or behavioral conditions and psychiatric disorders
    2. Performance and behavioral health decrements due to inadequate cooperation, coordination, communication, and psychosocial adaptation within a team
  4. Hazard: Distance from Earth
    1. Adverse health outcomes and decrements in performance due to in-flight medical conditions
    2. Ineffective or toxic medications due to long-term storage
  5. Hazard: Deep-space radiation
    1. Risk of space radiation exposure on human health


     It is easy to see from this list that almost every system in the body is potentially impacted by long-duration spaceflight. Note that these risks also include psychological and interpersonal issues that might arise due to the confines of any practical spacecraft for the foreseeable future.

     NASA and its Human Research Program work to mitigate the major risks shown in the list. Some are more critical than others, and their criticality and priority depend on the type of mission. For example, the likelihood of a medical problem or a teamwork issue will be higher with a Mars mission simply due to the longer mission duration and the need to deal with in-flight problems without help from the ground. In fact, the majority of the problems are worse with longer and farther missions such as one to Mars. On the other hand, an issue such as sleep impairment might be less critical on a longer mission. Sleep is disrupted on the ISS because of a high workload and operational pace, occasional emergency procedures, and altered light-dark cycles. On a deep-space mission lasting months or years, it might be that a normal operational pace could be achieved during the journey itself, enabling a more normal sleep pattern. This is critical because of the key role that sleep plays in so many other systems, not to mention its effects on performance.

     The most ambitious mission scenario now in the planning stages is a three-year mission to Mars, which would entail up to eighteen months on or near the planet. The most important risks in that mission fall out easily from the list above, given the duration, distance, and high degree of crew autonomy. This issue of crew autonomy is an especially important one to which we will return later. The key risks for Mars are the following:

     Radiation. Galactic cosmic rays and solar particle events are the two main categories of radiation in deep space, and their levels are higher there than on Earth or in low-Earth orbit. There is a long-term increase in the lifetime risk of acquiring cancer from this radiation. This is not a major operational concern for a mission that might last just a few years, but it can lead to significant burdens on healthcare systems in longer-duration flights of many years unless proper shielding is in place or other countermeasures implemented. Of more immediate concern during a mission itself are its degenerative and cognitive effects, which are not yet fully characterized, but may occur with chronic exposure at lower radiation levels than the known cancer risks (Parihar et al. 2016). Nevertheless, the prospect of a crew being exposed to a solar event that induces radiation sickness and immediate cognitive decline is sobering. This is especially true when it is recognized that a deep-space crew must have a high level of autonomy due to remoteness from Earth. The radiation-related risks are a major concern with both short-term and long-term consequences.

     Cognitive and behavioral issues. Isolation and confinement for long periods of time with a small group of people are challenging even for small, highly trained and dedicated crews. Obvious problems include disagreements with other crew members. But potentially more dangerous are difficulties with teamwork that can arise from these interpersonal issues that can have a direct negative effect on the success of the mission and the survival of the crew. This is an issue of particular import because teamwork problems can be exacerbated by cultural differences and misunderstandings about individual roles on the crew. Given the desirability of personnel diversity, these will undoubtedly be major factors in future expeditionary and colonization crews. Related to these are effects on cognitive function, which is negatively impacted on long flights for reasons that are not fully understood. This is sometimes referred to as “space fog” and it is a general perceived slowing of mental processes. Space fog may be related to high workload, elevated CO2 level, altered sleep cycles, and other stressors inherent to current spaceflights. Awareness of this issue is a key aspect of minimizing its impact, and professional astronauts are so highly screened that even with a decrease in cognitive function they are still high achievers. Nevertheless, the prospect of a crew undertaking a demanding mission at less than full cognitive capability must be considered.

     Gravity (or the lack thereof). Due to the lack of gravity (more properly, the lack of a net gravity or inertial force vector), astronauts experience a shift of body fluids toward the head. This has been recognized for decades, and results in sinus congestion, puffy faces, and spindly legs, among other more serious issues. One of these is the relatively recent finding of changes in visual acuity after extended stays on the ISS. This is, as current thinking goes, due to the small but constant elevation of fluid pressure inside the head, which finds its relief by moving fluid down the optic nerve toward the back of the eye. This pushes on the back of the eye and distorts its shape, changing its optical properties. This is serious enough when dealing with high-performing individuals in demanding situations, but the prospect that it might be just an early indicator of lasting neural damage that accrues over longer periods of time in space is especially troubling.

     Altered (reduced) gravity loading on the body also leads to a host of other problems. Constantly fighting against gravity while on Earth, so as to maintain upright posture and sufficient blood flow to the brain, provides a natural continuous form of exercise. This helps to maintain muscle strength, bone integrity, and cardiovascular function. In space, these physiological functions deteriorate unless measures are taken to protect them. Among the most effective measures is exercise, as discussed below. With proper exercise, astronauts can now return to Earth with sufficient muscle tone, cardiac function, and bone density. There is a caveat, however: While bone-mineral density is currently well preserved, it is not clear that bone strength (fracture resistance) is preserved, since bone is a complicated entity whose strength depends on its internal structure, not just its density.

     Food. The ability to provide nutritious and enjoyable food is also a concern. The shelf life of foods is limited by storage technology, processing, and inherent chemical processes. The food problem is more, however, than simply making sure that caloric content and balanced nutrition are achieved, particularly since packaging for preservation and storage often sacrifices palatability. Food is one of the very few pleasures that crews can enjoy during flights. It is a familiar and comforting reminder of home and the strong social ties attached to group dining are important for crew cohesion. Thus, a variety of healthy and pleasurable foods must be provided or grown in the spacecraft or habitat.

     Medicine. The likely occurrence of a significant medical condition is another major concern. The crew will consist of a small number of people who are highly fit, maintain healthy lifestyles, and are provided with opportunities for exercise and proper nutrition. Nevertheless, over the course of a three-year mission during which they will be exposed to a dangerous environment and called upon to be very active in new and unusual tasks, it is likely that medical concerns will develop. These might be as conventional as abrasions, sprains, and related simple injuries, or as complex as systemic changes initiated by fluctuations in the gut microbiome due to altered gravity and diet, and medication use. Head and back pain is common even on shorter flights to the ISS due to headward fluid shift and decompression of the spine. Rashes and minor injuries from floating debris are common. Particularly troubling is the increased possibility of kidney stones, either in space or on reaching a planetary setting, since the calcium lost from bones is excreted in urine and may form stones. These are just some of the issues that are known, as are many others which so far have been treatable and have not required a medical evacuation from the ISS. Simply due to increased time in mission and the challenges of going to Mars, however, it is likely that medical issues will arise and so a systematic and realistic approach must be taken. As one example of the tradeoffs involved, consider in-flight surgery. Current NASA thinking is that the amount of supplies and apparatus needed to perform even minimal surgery in space—not to mention problems of maintaining a sterile field and controlling blood and other fluids—will preclude surgery for the foreseeable future. This may change as noninvasive procedures are refined and the feasibility of surgery in resource-limited settings increases, but a realistic appraisal demands that consideration be given to the possibility that one or more crew members will not survive an entire mission because of the limitations of practical medical care.

     A comparison might be made to other cases of medicine in austere environments, such as Antarctic bases and nuclear submarines. This comparison can be instructive, but there are limitations. In extreme cases, medical evacuations can take place from each of those settings, although this is quite challenging for Antarctica. The diagnostic equipment and medical supplies available on each site, while limited, are more plentiful than on a spacecraft. Perhaps of most concern, communication delay due to distance from Earth will preclude most forms of medical support from the ground, especially in an emergency. Thus, the crew will need to have the onboard resources to not only treat medical conditions, but also to diagnose and anticipate them, and to make complicated clinical decisions based on the latest information without contact with Earth.

     Information. Finally, crews will need access to a great amount and variety of information while on their journey: personnel, vehicle, and mission status, for example. Many complicated systems will need to be monitored and maintenance performed in a timely fashion. For all of this, an intuitive set of human-system interfaces will be needed. These will have to provide crews with necessary information that is easy to digest in a timely manner and that helps guide them to proper actions. Too much or too little information is not helpful and can lead to burnout or a dangerous lack of situational awareness. Anyone who has dealt with current information technology and tried to make sense of the seemingly haphazard information in an internet search, which is easy to obtain but difficult to process and understand, will know that this area still requires significant work.

     There remain other considerations, but this brief survey should give an idea of the range of concerns for humans on deep-space missions that are in the current planning stages. Countermeasures are in place or in development for each of these issues. We note just two here. Exercise is a very powerful and successful countermeasure and is in regular use on the ISS (approximately two hours per day per person). Not only are there obvious physiological benefits for bone, muscle, and cardiovascular fitness, but exercise provides a sense of well-being as a psychological countermeasure. “Runner’s high” is well known, but also the exercise schedule provides “protected time” during which other tasks are secondary, allowing a mental break. (Astronaut time is the single most valuable quantity during a spaceflight, and their time is often scheduled to the minute. This can lead to timeline pressure and constant stress.) Nutrition is the other main countermeasure now in place and it too has wide-ranging benefits. Again, not only are there obvious physiological benefits, but food provides something familiar and comforting in an environment that is largely devoid of the normal human pleasures. It is also a socializing aspect, which crews find to be very important when the demanding schedules on the ISS can inhibit regular social interactions.

     Note that in the area of psychological function, including teamwork, the countermeasures are not so highly developed. Education and awareness are perhaps the most useful current approaches. It is worth noting that one very important psychological countermeasure, however, will not be available to crews on Mars missions: the ability to speak to someone on Earth at any time about any issue. This includes family and friends, but also physicians and psychologists. The communication delay on a Mars mission will preclude most meaningful conversations of this nature.

     (More information on these risks and countermeasures can be obtained from the series of Evidence Reports that the NASA Human Research Program maintains on its web site:


     Thus, we come to the issue of crew autonomy. This is not a major concern with missions to low-Earth orbit, where home is just a few hours away and there is constant communication with mission control. In an emergency, the crew knows it can get instant and expert assistance. For missions farther out into deep space, autonomy will be a critical issue for Mars and even more so for missions beyond that. The need for autonomy increases with distance and duration to the point where it will be almost beyond our current comprehension for missions in the next century that might settle and colonize other planets.

     The main feature of autonomy is that the crew must be able to function on its own under nominal and emergency operations. The ability to recover from the unexpected and maintain mission success is closely related to resilience. It would be nice, then, if resilience could be characterized and even measured, so that crews would know when it is being compromised. Let us consider how this might be done.


     From the previous discussion, it would appear that things are under control for humans in missions to LEO and maybe even to the Moon and Mars. NASA’s ambitious but feasible plans call for the mitigation of each major risk described above through extensive research and proper mission design before undertaking a lunar or Martian journey. Consider, however, the following scenario on the way to Mars:

     There is a solar flare or coronal mass ejection—a solar particle event (SPE) that emits a storm of high-energy protons. There is an undetected microorganism hiding, deeply embedded, in the spacecraft water supply, or the food supply, or the air-filtration system. The spike in radiation induces a mutation in the microorganism. At the same time, for reasons not completely understood, the astronauts’ immune systems are undergoing alterations that make them less effective in fending off some pathogens. Also, at the same time, one person is on a course of antibiotics that has caused a significant change in his gut microbiome, which modulates many body functions. This has seriously depleted the on-board medical stores. As if this weren’t enough, the exercise equipment breaks. At first glance none of this is particularly troublesome because, as we know, each of the individual risks has been sufficiently mitigated: radiation, food supply, immune function, microbiome, medical supplies, and exercise countermeasures. So, there is no problem, right?

     Wrong. Two days later the entire crew is dead or debilitated to such an extent that the mission is compromised. What went wrong? The radiation spike induced a mutation, which impacted the nutritional status of the crew (food or water supply). The human immune system is altered in space, as are some pathogens, with some becoming more virulent and others less so. If a mutated organism invades a compromised immune system, the outcome is not likely to be pleasant. The gut microbiome—the many microorganisms that live in the intestinal tract—exhibits some alterations when in space, and medications like antibiotics can also have a devastating (hopefully temporary) effect on the quantity and diversity of these microorganisms. The microbiome has been implicated in a wide variety of physiological functions, including even cognitive status. Exercise, in maintaining general systemic health, could help overcome the changes in immune, microbiome, and cognitive function. When these events transpire together (and they might be related to each other, as for example a radiation event might adversely affect instrumentation that runs the exercise device), unanticipated consequences can ensue.

     Thus, a crazy interaction of factors has conspired to bring about a devastating outcome. But this is not as crazy as it sounds. Aviation and aerospace “mishaps” and incidents are rarely caused by a single precipitating factor; they are almost always the consequence of an interacting series of events. In our example, the interactions have not been understood, characterized, and tracked properly over the course of the mission. Early recognition of changes in these factors, and how they might be connected to each other, might have led to an early intervention to stave off the devastating result.

     How can we do this? How can we systematically track all the of the relevant factors and their interactions and predict when the overall system (mission) is approaching an undesired state from which recovery might not be possible? How can we use this knowledge, in other words, to increase mission resilience?


     Imagine now a situation in which the on-board computer contains a mathematical model of the main factors that can be measured and tracked over the course of a mission: environmental and physiological parameters, interpersonal interactions, sleep quantity and quality, mood, exercise, and many others. Sensors for many of these quantities exist, as do “wearables” to make individual personal measurements continuously and nonintrusively; additional new sensors are being developed all the time. The mathematical model also contains information about expected interactions between parameters. For example, a change in CO2 level can be expected to have some specific effects on the crew, and that corresponds to an interaction or link between atmosphere and psychology, mood, depression, and team cohesion, in addition to performance on standard tasks. If CO2 level changes for some reason, the computer can compare the effects that actually occur to the expected effects. The actual effects might not be pleasant or desirable, but if they are at least understood, then the mission is still on track: The actual mission falls within the range of the model. If there are unexpected interactions, such as an unusual physiological response on the part of some of the crew to a change in CO2 level, then this can indicate that a crucial interaction has changed, and the underlying model of interactions is no longer accurate. If this happens with enough interactions, a problem might be in the offing. This is because, recall, it is unanticipated and little-understood interactions that lead to bad outcomes. (The model and algorithm described here are beyond the current state of the art. They might be based on complexity theory and network concepts, with AI and machine-learning components, some of which have yet to be developed.)

     With this sensor-model system in place on a spacecraft to assist the crew, now consider the following scenario. The level of CO2 goes up for reasons that can’t be helped (perhaps the scrubber is down and there is a need to conserve consumables and power). As expected from elevated CO2, two crewmembers get into arguments and have difficulty working together, but one other crewmember exhibits no change in behavior when she typically becomes irritable and sleeps longer. This is a change in interactions—in cause and effect. The cabin CO2 might still be within normal limits, and the individual crew behaviors might be within normal acceptable ranges. The interactions, however, tell a different and subtler story. Is the third person already maxed out with other stresses such that elevated CO2 no longer has much effect? Is there some other change in metabolism that has altered the response to CO2? Whatever the cause, this altered interaction should be tracked, and if similar unusual changes occur soon after, then some type of intervention might be needed to fend off an undesired developing situation. Perhaps the computer algorithm recommends a change in the schedule to separate the two who are fighting, and additional rest and relaxation for the third, and then monitors the situation to see if these changes improve crew conditions and interactions.

     Resilience and performance have now been enhanced. We have provided this crew the tools to be resilient and they have maintained mission resilience independent of mission control. This is a microcosm of what will be necessary on a much larger scale for the much more ambitious journeys of colonization.


     Considerable thought and effort have gone into defining and developing countermeasures, as noted previously. There is a rigorous—if sometimes contentious—process for determining what areas need to be addressed and what the best countermeasures are. We can learn from this process in extrapolating to future missions what the major problems might be and how they might be mitigated.

     Consider a journey to an outer planet (or its moon), or even to another solar system, possibly taking several decades.

     If there is no artificial gravity (AG), then the physiological degradations can be substantial and dangerous—a serious concern once the crew reaches its destination. Given current knowledge and a set of reasonable conjectures on the design of such a mission (crew makeup, spacecraft capabilities), it is likely that crews would land in such a debilitated state that their very survival would be jeopardized. Consider first that on the ISS exercise is a major countermeasure for an array of deficits, but in current implementations requires approximately two hours a day. Let’s allow that sophisticated methods are developed to augment the potency of exercise, such as ketogenic diets, blood restriction, and muscle cooling. Even with these in place to reduce the actual exercise requirement, it is likely that compliance will be an issue. Further considering the psychological difficulties of such a journey, motivation will flag, and the drive to maintain health could in turn diminish.

     One has only to observe astronaut crews returning from ISS missions of six months to see the possible consequences of the problem. Even in these groups of elite, highly trained and motivated professionals, with excellent countermeasure compliance, there is need for assistance for the crew in leaving the spacecraft and making its way to the medical tent. The ability to walk in any meaningful way is impaired for hours to days, and full recovery can take weeks or months. This is the current best-case scenario. A possible solution to this is to allow the first planetary settlers a significant period of rest, recovery, and rehabilitation upon landing. The spacecraft would essentially become a rehab facility for physical therapy while the occupants once again learn to walk and maneuver in a gravity field and regain muscle strength and aerobic capacity. This is a reasonable approach but requires a much larger habitat on the surface than would be needed simply for landing a group of people.

     Even in this optimistic view, there are physiological issues such as loss of bone density and strength that will remain significant and dangerous. (Landing on a body with less than a one-gee field will ease these concerns since the likelihood of a fall, and the intensity of a fall, would be reduced and hence the possibility of breaking a bone would be reduced.) Added to this is the chronic shift of fluids to the upper body and head, which might not only induce vision problems as seen in some ISS astronauts, but could be causing low-level neural damage. The prospect of a large number of slightly demented individuals stumbling around on a new planet, tripping and breaking bones, is not one that most planners would find desirable or acceptable. They would be like the first settlers in a foreign land who encounter a bacterium or virus for which they have no natural immunity, only in this case the scythe is wielded by gravity and not by an organism.

     Artificial gravity is therefore a compelling option for such a journey (Young 1999; Clément and Bukley 2007). The longer the journey, the more compelling the case. When we consider journeys of decades or more, it is almost unconscionable not to consider AG as a requirement. Indeed, many of the practical issues that inhibit its ready acceptance in current planning should have been solved by the time these journeys of colonization become a reality. But AG is not a panacea, nor is it obvious how best to implement it. One appealing method entails constant linear acceleration of the spacecraft for half of the journey, and then constant deceleration (technically, acceleration in the other direction) for the other half of the journey. This creates a linear acceleration force, which is indistinguishable from gravity itself. The change from acceleration to deceleration at the halfway point would be quite an event. Other than that, this would be a benign method to produce some level of AG in the entire craft. The propulsion requirements for this are currently prohibitive. Better to think along more conventional lines: a rotating craft that produces centripetal force proportional to radius (distance from the axis of rotation) and to the square of the rate of rotation. Larger and faster spinning produces more AG.

     Rotation of an entire spacecraft in this manner is daunting. It also raises the question of what happens when the craft reaches its destination and rotation stops or the crew departs the rotating craft and experiences zero-gee for the first time, at exactly the time they must prepare for a challenging planetary descent. Perhaps there is a better way. Much thought has been given to alternate approaches, such as rotating just a part of the spacecraft. If the sleeping quarters are rotated, the crew will experience eight hours of AG each night, while enjoying the pleasures of zero-gee the rest of the time. A spacecraft might also contain a small exercise chamber in the form of a cycle ergometer (exercise bicycle) that moves in a tight head-over-heels circle when pedaled, supplying exercise and providing AG at the same time. Each of these approaches has its problems, but some combination of them could almost certainly be made available to a large crew.

     Even with some combination of these implementations, however, some problems remain. We don’t yet know how much AG—what level and for how long—is needed to counteract the deconditioning effects. With research this can be determined along with the engineering solutions. The benefits would appear to be significant. AG would be almost ideal for bone and muscle effects, and most especially for the problems attendant to headward fluid shifts, which cannot be countered by exercise. For some other areas, there are unfortunately undesired side effects. The vestibular system, for example—the balance organs in the inner ear—can adapt well to a zero-gee environment but is used to orient within inertial reference frames. In other words, rotating environments are not kind to the balance system. Anyone who has spun around a few times on a bar stool (sober or otherwise) and then tried to stand and walk understands the problem viscerally. Several playground devices have similar effects. Humans can adapt to these challenging settings (Lackner and DiZio 2003), but the transition to and from an AG situation could be difficult.

     But wait—are we missing something here? Is it possible that there are salutary effects of zero-gee itself—effects that would be missing if AG were implemented? Consider that spaceflight itself and the spacecraft environment with its close quarters, strenuous workload, and imminent danger are demanding enough in and of themselves. Is it possible—just possible—that the experience of weightlessness in this setting provides one of the few pleasures that helps make it tolerable? Would the imposition of AG in such an already stressful situation actually make things worse? We do not know, and the idea might be far-fetched, but it is worth considering. There are pleasurable effects from unusual patterns of vestibular stimulation—witness the popularity of roller coasters and other semi-nauseating escapades. Likewise, the experience of short periods of zero-gee in parabolic flight has been described as the most fun one can have in public—at least short of actual spaceflight. The Apollo astronauts remarked that they could each find their little bit of personal space in the cramped spacecraft, since they were free to explore all three dimensions in zero-gee and could inhabit nooks that were otherwise inaccessible. How much of the famous “overview effect” is due to seeing Earth from above, how much from the experience of 0g, and how much from their interaction? (The overview effect is the vivid realization reported by many astronauts of the fragility and isolation of the Earth in space, the invisibility of political boundaries, and the sense of union among the people on the planet (White 1998).) These are open questions and although it might be small it is too soon to dismiss the possible beneficial effects of zero-gee itself on psychological well-being. Without it, a spaceflight journey of decades might become mere drudgery rather than an adventure—one may need a reminder that the environment, and hence the journey, is unique, and the constant reminder of zero-gee could do that very effectively (despite the problems that it also creates).

     Let us return to the more practical aspects of artificial gravity. As noted, AG can address in a natural manner many of the physiological concerns of extended spaceflight. However, even with AG there will be problems. Currently the biggest risks identified by NASA are related to radiation exposure and adverse effects of spaceflight stressors on cognitive function and behavior. AG will not help these. Radiation might be addressed with clever shielding and maybe even radio-protectant pharmaceuticals. But make no mistake: Psychological maladjustment is the potential killer and this problem will not be solved with AG.


     Consider the psychological issues arising during a decades-long journey (Manzey 2004). Some will be inherently mitigated relative to even the first Mars missions, because of a larger spacecraft with more people on board. Thus, the problems related to confinement might be lessened, although it’s still likely that the minimum tolerable amount of volume per person will be implemented—it is just that that volume will be used to better effect: It will be reconfigurable for the changing needs of the crew, allow group interactions or individual solitude as needed, and provide for some individual psychological needs. The presence of many people can reduce the problem of small groups becoming tired of each other and getting on each other’s nerves; of course, other problems are raised through the greater diversity of skills, motivations, and dedication. Teamwork might be aided by the ability to rearrange teams for some tasks through cross-training of individuals so that the same small group does not have to work together all the time.

     However, remoteness and isolation will continue to be significant issues. There were dire predictions in the early days of human spaceflight, to the effect that astronauts might experience a dramatic detachment or breakaway phenomenon, being physically separated from Earth to an extent never before experienced—beyond the atmosphere. This concern turned out to be misplaced, even overblown. Instead, it turned out approximately six decades later that astronauts take great pleasure in viewing Earth from the cupola of the International Space Station. Many have commented over the years, even before the ISS, that watching Earth was a great treat, possibly even therapeutic (not in so many words). This consoling aspect will not be available to those on long-distance missions. Even in going to Mars, the image presented of Earth will be that of just another star in the heavens. The psychological impact of this is impossible to determine. Add to that the realization that there is no return if the journey is one of long-term exploration or colonization, and some form of separation anxiety might well occur. There will be the need to change one’s loyalties and sense of identity to a wholly new place.

     Until this mental transition fully takes place, there may be some erosion of resilience—a relative deficit in performance and in dealing with problems—at least in the middle term of the voyage as memories and longing for Earth and what it represents remain strong. Certainly, in a generation or two this reminiscence will remain but perhaps it can be modified and infused with feelings of attachment for the new celestial home. This is not a “mere” psychological factor—it has an impact on several factors which, as we have seen, are tightly connected. Thus, in the mid-term, it may be necessary to have Earthlike reminders that gradually shift in a weaning process. It has been proposed, for example, that deep-space missions now on the horizon include a virtual-reality arrangement that mimics the traveler’s home—his or her favorite room, settings, people, plants, animals, and so on. One cannot help wondering if this is wise. Would not a “clean break” be better? For early missions there might be no alternative, but later it might be better to break this connection with Earth as soon as possible. (NASA and other space agencies use a variety of Earth-based analog facilities in an attempt to mimic and mitigate these psychological concerns. They all, however, fall short in some way from reproducing the full range of effects: The missions are not long enough, the setting is not inherently dangerous, and the facility is not truly remote, or it is so large that the crew is not confined in the same sense as in a spacecraft. In this critical issue we will not truly know until we go.)

     How will we track if these measures are effective, even the psychological measures? These aspects have implications for physiology and performance through stress pathways. So, just as proposed above for shorter missions, the continuous monitoring of physiology and performance, including psychology and interpersonal relations, will be one key to tracking the effectiveness of breaking one’s loyalties from one planet to a new one.


     The psychological issues are bad enough. But all this discussion does not even touch the real issue. The likely worst case is that there will be a confluence of circumstances that is unforeseen: a set of events in which several risks come under attack, each of which was considered to be adequately mitigated. Examples have been given previously in the context of a mission to Mars, but this will take on increased importance in the case of longer and farther missions in which the crew will be on its own. Reliance on Earth might be realistic for the first few weeks, after which it will be a rueful wish and then nothing but a quaint memory. Crews and colonists will need the ability to maintain resilience—mission success in the face of unknown perturbations—apart from the assistance of anyone on Earth. And as we have seen, this will be in large part a consequence of paying due attention to interactions among factors (Shelhamer 2016; Mindock et al. 2017).

     This takes on a whole new meaning in the context of colonization, when the travelers will truly separate themselves from Earth and its support mechanisms (Bell and Morris 2009).

     Faced with the prospect of never returning to Earth, psychological issues will loom large, especially on the first of such missions. As noted, this has widespread effects since stress is a major factor with many connections. There will also be physiological and psychological changes that occur once ensconced on another planet or moon. These might impair the ability to return to Earth, which would be another reminder that that is no longer a viable option. The question then becomes whether to allow these adaptive alterations to proceed or to attempt to slow or inhibit them. The answer is not a simple one. Adaptive evolutionary changes take place on Earth over long timescales, partly because the environment is relatively stable (certainly as far as gravity is concerned). Faced with a dramatically different environment—altered gravity level, unfamiliar atmospheric pressure and composition, different magnetic field, to name a few—evolutionary processes in the human organism might be accelerated. Under such circumstances, epigenetic alterations might take on a larger role in the heritability of acquired traits. Whatever the mechanism, settlers will likely be faced with the problems inherent in rapid change—only this will involve changes to the humans themselves. The possibility that some of these changes will be undesired—and could interact with other changes to the overall detriment of the person—should not be ignored. To the extent that these adaptive alterations proceed, some monitoring might be in order so that undesired and unanticipated interactions can be identified.

     It is almost certain that some adaptive changes will prevent the person from ever returning to Earth, or even to a planet with a different gravity. Consider landing, settling, and evolving on a planet with considerably less than the one-gee of Earth: This might eventually lead to taller and thinner humans, since maintenance of blood flow to the head would not be as challenging. Cardiac capacity would change for the same reason. The long, weight-bearing bones would also become thinner and weaker, as would the supporting musculature. In short, organisms are good at shedding unnecessary metabolic costs to make efficient use of resources such as nutrients, and these are all appropriately adaptive changes for the environment in question. But these people would then not be able to function normally on Earth, where they would be highly prone to injuries. It would be unrealistic and unethical to even consider sending them (or their offspring) to Earth or other locations where the gravity level is significantly higher. Thus, humans might indeed become a multi-planetary species in this way, but each subpopulation of humans would be forever tied to just one or a small subset of planetary bodies: No single individual would be truly multi-planetary.

     But also consider less dramatic effects. Taller people could be problematic in habitats designed with small dimensions to preserve resources. It would be well to track and predict these types of interactions between physiology and engineering.

     On the other end of the spectrum, there might be a temptation to enhance or accelerate adaptations to specific environments. Or to simply make immediate alterations for expediency. This raises the specter of genetic modifications, or surgical ones. One might argue that many space settings would call for the shortening or removal of the legs. In a constant zero-gee setting such as a permanently orbiting station, legs are unnecessary for locomotion. In fact, they can be a hindrance by banging into things, especially as proprioceptive sense of leg position decays from lack of use. The resulting reduction in body mass and fluid reservoir would be beneficial in reducing radiation exposure and in combatting headward fluid shift. On the other extreme, on a planet with a very high gravity, metabolic costs could be diminished by reducing the hydrostatic gradient—that is, by making people significantly shorter.

     As intriguing and tempting as these concepts might be, society best tread lightly in any such endeavor at the risk of introducing new complications or overlooking crucial interactions. The introduction of new species to an isolated environmental niche is a historical example: Where there is no natural predator the new species overtakes the available resources. This is one simple form of unintended consequence. There are many others, and in a space-settler setting where there is precious little backup capability (you can’t go home again), even subtle second-order effects can take on outsized significance.


     Thus, the key in all these situations of long journeys of settlement or colonization is to recognize that we might—just might—be smart enough to mitigate the major known risks for long-duration spaceflight on an individual basis for a relatively short Mars exploration mission (three years), but we are unlikely to be smart enough to determine in advance the countermeasures that will be needed on journeys of colonization. It is almost a certainty that unexpected and unanticipated problems will arise—perhaps a new form of psychological syndrome caused by an unusually strong attachment to an artificial habitat that takes on undue importance in the absence of a familiar Earth and a viable atmosphere, displacing emotions and bonding with other humans. This is pure conjecture of course. More likely, perhaps, would be a novel combination of radiation that interacts with an organism in the soil and revives a dormant species (we see viral shedding on the ISS) for which the weakened immune system is no match, while at the same time the medical supplies have been depleted in treating more conventional problems.

     So, how do we give crews the tools to deal with these larger problems—the unknown unknowns? What would these tools be? Some are tangible and, while not trivial, are at least easy to delineate in principle: 3-D printers, DNA sequencers, medical instrumentation and diagnostic equipment, a vast database of information and the ability to acquire updates (not a trivial matter when communication with Earth is challenged by time lag), and information systems that provide the crew useful and important information in a timely manner without saturating them.

     But more fundamentally we need to provide the conceptual tools for dealing with the unknown. These are the same as described previously but at a higher level of complexity. This essentially entails a mathematical model that encompasses a deep understanding of the many factors that impact survival and mission success. These are, as noted, not only medical, physiological, and psychological, but also encompass interpersonal interactions, habitat configuration, task planning and design, scheduling, and many others. Sensors for these key variables can track the most important of these factors, continuously feeding data to the model, which would monitor each individual parameter for problematic deviations but also track interactions between parameters and compare them to what is expected from its stored database. Adding to this complexity is the fact that this model must adapt as the people adapt to their new setting and understand when significant changes are part of a beneficial adaptation process versus a detrimental maladaptation or dysfunction.

     Thus, we must provide crews of the future the tools for solving problems and not the answers to the problems per se. We can teach a crew to fish and it may survive for a year, but if we give the crew the tools to make rods and reels and find fish and adapt in order to metabolize other types of fish, then they can survive and thrive for generations.


     Many of the issues raised here transcend those of engineering and operations, the typical realm of advanced spaceflight discussions. They become issues that the larger society should address. As a society, are we willing to do what it takes to enable these voyages of colonization and settlement? The concern is not just the financial cost or the opportunity cost, but the larger cost to society in terms of resource allocation and even more so in terms of perspective. Being audacious enough to give people a fighting chance of surviving and thriving on other planets might mean, as indicated here, that changes in human psychology, and perhaps even physiology, might be needed. New structures of governance and civic cohesion might also be needed. All these changes might in fact occur on their own as a natural adaptive response to a new environment, whether we like it or not. Yet we retain the right to decide whether to put our fellow humans into that situation. How might the attendant physiological and psychological changes in turn change our view of what it means to be human, when it no longer explicitly means “Earth-dweller”? Will we recognize governing structures that are designed to accommodate small populations and environmental stressors on an alien world, and will we be comfortable with them as representative of the civic decisions that have guided our institutions on Earth? Are we ready for such a change in how we see ourselves?

     It is one thing for government space agencies, or private companies like Blue Origin and SpaceX, or futurists, to ponder these issues—even to make pronouncements as to preferred policies (as we do in this volume). However, if humans are truly to colonize and settle elsewhere in the solar system as a species and not just as a small group of rugged individualists, then society must ponder these issues in an open forum and attempt to reach some consensus. To not do this will leave the decisions to those organizations—public or private—that first have the means to undertake the journeys.

     Consider a microcosm of this larger issue. Spaceflight is a risky endeavor. It often results in the loss of life, and there is a general acceptance of this fact as a society. We have decided to accept that risk. It is important to recognize that this is not just a set of individual choices made by individual astronauts (Kahn et al. 2014). Astronauts might, for example, be willing to accept a large potential increase in lifetime cancer likelihood in exchange for trips into deep space. As a society, on the other hand, we might not accept this risk (through the decisions made by the space agency as dictated by law and regulation).

     If people want to risk their lives on spectacular feats such as space travel, do we, as a society, have a right to stop them? Do we have a right, or even an obligation, to withhold resources that might aid in their success? Does it matter if the people involved are normal citizens like us, and not those specifically trained to recognize and evaluate the risks? What makes an astronaut remarkable and commendable is the willingness to undertake a great risk while fully understanding the nature of the risk; that is part of their job and we respect them not for being reckless but for being aware.

     These are not moot questions. Society benefits from great feats successfully accomplished. Society suffers the consequences of a spectacular and fatal failure—especially if it impacts future policies and hinders further progress through risk-aversion. Even beyond this, if the decision to support these endeavors is made as a society, then a great number and variety of societal institutions can marshal themselves to the cause: educational, civic, research, and financial. In this way, the resilience of the endeavor is enhanced through multiple institutions and societal structures contemplating and developing multiple simultaneous solutions and approaches (rather than a more constrained and narrow approach that would be feasible under the auspices of a small group without that broader societal support).

     Fortunately, we are in a position to take incremental steps in this direction, and they are taking place now. Commercial suborbital space flight will be a reality soon. Passengers will be able to pay for a suborbital rocket hop that takes them into space (above about one hundred kilometers) for a few minutes of weightlessness. These trips will, especially at first, entail significant risk, regardless of the great amount of engineering and due diligence now being invested in making them safe. The decision in the United States, at least for now, appears to be that the less oversight and regulation for this new industry, the better. The concern, once the spacecraft have been tested and the passengers informed as to risk, is the safety of those on the ground who have not elected to be participants. This is an approach that places great responsibility on the flight operators and their customers, and implicitly asks society to accept the attendant risks. It remains to be seen if this approach holds up in the face of disasters, near-misses, or mishaps that are inevitable in this new venture. The decisions made at those times will tell us much about whether we are ready to face the greater challenges of planetary colonization.


     Bell, Sherry, and Langdon Morris, ed. 2009. Living in Space: Cultural and Social Dynamics, Opportunities, and Challenges in Permanent Space Habitats. Aerospace Technology Working Group.

     Clément Gilles, and Angeli Bukley, ed. 2007. “Artificial gravity.” Springer Science+Business Media.

     Francisco Dave, and Elkin Romero. 2016. “NASA’s Human System Assessment Process.” Presentation at Human Research Program Investigators’ Workshop (8–11 Feb). Galveston, TX.

     Kahn, J. P., C. T. Liverman, et al., ed. 2014. Health Standards for Long Duration and Exploration Spaceflight: Ethics Principles, Responsibilities, and Decision Framework. National Academies Press.

     Lackner, JR, Paul DiZio. 2003. “Adaptation to rotating artificial gravity environments.” Journal of Vestibular Research 13, no. 4–6 (February):321–30.

     Manzey, Dietrich. 2004. “Human missions to Mars: new psychological challenges and research issues.” Acta Astronautica 55, no. 3-9 (August–November):781–90.

     Mindock, Jennifer, Sarah Lumpkins, et al. 2017. “Integrating spaceflight human system risk research.” Acta Astronautica 139 (October):306–12.

     Parihar, Vipan K, Barrett D. Allen BD, et al. 2016. “Cosmic radiation exposure and persistent cognitive dysfunction.” Scientific Reports 6 (October):34774.

     Shelhamer, Mark. 2016. “A call for research to assess and promote functional resilience in astronaut crews.” Journal of Applied Physiology 120, no. 4 (February):471–2.

     White, Frank. 1998. The Overview Effect: Space Exploration and Human Evolution. AIAA.

     Young, LR. 1999. “Artificial gravity considerations for a Mars exploration mission.” Annals of the New York Academy of Sciences 871 (May):367–78.


The basic requirements for life support are:

  • Breathing Mix: an atmosphere to breath, or the crew will rapidly suffocate. Oxygen must be added as it is consumed and carbon dioxide removed as it is exhaled. Humidity must be maintained at a confortable level. An alarm should be triggered if dangerous contaminants are detected, or the signature of a fire.
  • Water: for drinking and hygiene, or the crew will die of thirst (though probably not die of filth).
  • Food: for eating, or the last surviving cannibal crew member will starve to death.
  • Waste Disposal: or the crew will perish in a sea of sewage.
  • Temperature Regulation: or the crew will either freeze or roast to death, probably the latter.
  • Radiation Shielding: or deadly radiation will take its toll.
  • Artificial Gravity: Need a replacement for gravity or limited duration tours in microgravity or it is death by Old Astronaut Syndrome.

The first three requirements are called "consumables", since they are gradually used up by the crew. In Greg Bear's War Dogs, the Space Marines call them "gasps," "sips," and "lunch".

Each of those three can be controlled by either an "open" system or a "closed" system.

Open systems are ones where a supply of the consumable in question is lugged along as cargo, enough to last the for the planned duration of the mission. It is renewed by "resupply", by obtaining new supply from a resupply spacecraft, a base, or an orbital supply depot. Things can get ugly if the mission duration becomes unexpectedly prolonged, for instance by a meteor scragging the spacecraft's engine.

Closed systems are ones where the supply of the consumable in question are renewed by some kind of closed ecological life support system. Generally this takes the form of some sort of plants, who use sunlight to turn astronaut sewage and exhaled carbon dioxide into food plants and oxygen.

Note that requirements for consumables can be drastically reduced if some of the crew is placed into suspended animation.

If you want more data on life support than you know what to do with, try reading this NASA document. Otherwise, read on.

For some great notes on spacecraft life support, read Rick Robinson's Rocketpunk Manifesto essay.

As a very rough general rule: one human will need an amount of mass/volume equal to his berthing space for three months of consumables (water, air, food). This was figured with data from submarines, ISS, and Biosphere II. Of course this can be reduced a bit with hydroponics and a closed ecological system. This also makes an attractive option out of freezing one's passengers in cryogenic suspended animation.

Eric Rozier has an on-line calculator that will assist with calculating consumables.


Many of the settlers of Talentar, who would later become dirt farmers and ecopoetic line techs, were drawn from rural areas of Eliéra, seeing an opportunity to apply their sophisticated knowledge of modern agriculture and silviculture to the problems of making this new world blossom.

It is from these settlers that a local variation in the rights and customs of hospitality has become ubiquitous. Many of the foresters and line techs of the Delzhía Terra region in particular were drawn from the wooded upland valleys of the Vintiver region. An age-old custom there was the “traveler’s bite”; a traveler riding through could stop at any farmstead and rap at the kitchen window, receiving in exchange for a few taltis a fill of working-man’s beer for their mug, a handwheel of cheese, a pocket-loaf, and perhaps some trimmings of the day’s roast.

On Talentar, this evolved into the custom of the “traveler’s charge”. A traveler by foot or rover can stop at any of the small domes or prefabs dotting the dusty plains, signal at the service hatch, and receive a charge for their powercells, a fresh oxygen tank for an expended one, and a packed handmeal of the local produce – an invaluable service for traveling light, or in a pinch.

– “Sophontology of the Talentar Settlers”
Mirial Quendocius

Breathing Mix


N2 79%, O2 21%
< 25.1 kPa: Anoxia
101.3 kPa: Normal
> 254.0 kPa: O2 toxicity
> 400 kPa: N2 narcosis

O2 100%
< 5.3 kPa: Anoxia
32.4 kPa: Normal
> 53.3 kPa: O2 toxicity

10 secs until unconscious
90 secs until fatal damage
maybe Ebullism
The Bends

< 6.3 kPa w/bare skin
     (Armstrong Limit)
     (Kittinger Syndrome)
< 2.0 kPa w/Pumpkin Suit
Never w/space suit

< 3/5 kPa can safely open ISS outside airlock hatch without damaging the hinges

According to NASA, each astronaut consumes approximately 0.835 kilograms (0.560 cubic meters) of oxygen per day. They breath out 0.998 kilograms of carbon dioxide per day.

For reasons explained below, NASA and other space agencies use two types of atmosphere: space suits use Low Pressure (pure oxygen at 32.4 kiloPascals [kPa]) and habitat modules use High Pressure (breathing mix at 101.3 kPa).

As a point of reference, a SCUBA tank is pressurized to about 250 bar i.e., 250 times atmospheric pressure. At that pressure, one person day of oxygen takes up about 0.00224 cubic meters.

Stored as liquid oxygen, 0.8 kilograms would take up about 0.0007 cubic meters. This requires extra mass for the cryogenic equipment to keep the oxygen liquid, but the volume savings are impressive.

So as far as pure oxygen goes, you take 0.8 kg for one person-day of oxygen, muliply it by the number of crewbeings on the ship, and then muliply it by the number of days in a standard mission (i.e., desired "endurance time" or time between supply stops) to discover the total oxygen mass requirement. Repeat with the volume figure for the total oxygen volume requirement.You'd be wise to add an additional reserve of about 25% to take account of pressurization of the hull, loss due to various mishaps, and general military paranoia.

However, this is just pure oxygen. This is insanely dangerous to use as the ship's atmosphere, the accident that killed the Apollo 1 crew proved that. In practice one uses a "breathing mix" of oxygen and another gas.

Generally the other gas is nitrogen. The technical term is "nitrox". Terra's normal atmosphere is 78% nitrogen, 21% oxygen, plus various other trace gases. People can suffocate if the level of carbon dioxide rises to 7% to 10%.

The Space Shuttle uses a 79% nitrogen/21% oxygen mix at atmospheric pressure (14.7 psi or 760 mm Hg). The shuttle space suits use 4.3 psi of pure oxygen, which means they have to prebreath pure oxygen while suiting up, or the bends will strike. Setting up the optimal breathable atmosphere is complicated.

The amount of oxygen must be kept under strict limits or oxygen toxicity will harm the crew.

At pressures higher than normal atmospheric pressure nitrogen becomes dangerous to breath. Generally spacecraft do not have to worry about that, unless they are diving into Saturns atmosphere or something similarly extreme. The colloquial term is "rapture of the deep", the technical term is "nitrogen narcosis." Pretty much any other inert gas you replaced nitrogen with will still have a narcosis effect, with the exception of helium. This is the heliox mix used by deep divers. A side effect of heliox is it makes all sounds more high pitched. In particular it makes the human voice sound like Donald Duck. Radios can be outfitted with a "helium de-scrambler" which electronically lowers the pitch of whatever is transmitted.

The Bono Mars Glider uses a heliox atmosphere, but I cannot figure out why.


Research stations in Jupiter’s atmosphere must be adapted for ultra-high-pressure conditions. For example, to avoid nitrogen narcosis, station air supplies are mixtures of oxygen and helium rather than oxygen and nitrogen. This means that regular station residents speak with the squeaky cartoonlike voices that result when human larynxes vibrate in a helium environment.

Those who live in such stations say they quickly become accustomed to the phenomenon. Psychological tests prove otherwise. Extended exposure to high-pitched helium voices causes severe subconscious stress, leading to a variety of mental disorders—from general anxiety and mood swings to clinical depression and outbursts of rage. The reason is simple: Homo sapiens evolved as social animals, and they have a deep-seated need to hear voices that are recognizably human.

To satisfy this need, each station has at least one man and one woman with their laiynxes surgically altered to sound “normal” in helium. These people are not researchers: their job is simply to walk around the station, letting their voices be heard. Sometimes they tell stories or jokes; sometimes they share gossip they’ve picked up from other people in the station; sometimes they sing, recite poetry, or just ramble on about nothing. The content of their words isn’t as important as the sound—the soothing timbre of a human voice. Wherever these people go, they ease tension and make it possible for others to concentrate on their work.

Outsiders sometimes ask why all people on these stations don’t have their voices altered. Unfortunately, a larynx that works normally in an oxygen-helium atmosphere doesn’t work at all in conventional air. Therefore, researchers who want to go home again can’t have the surgery … and the people so treasured for their voices on Jupiter station are utterly mute on Earth.


(ed note: back in the 1950s, the Sunday newspaper supplements were full of breathless articles speculating about life on the planet Mars. Most of them contained remarkably silly extrapolations. Clarke's article is satirizing such articles. It is a breathless article written by a Martian, cluelessly speculating about planet Terra. Needless to say, Terra is the only planet in the solar system with an oxygen atmosphere that will support fire

And all you kids, "newspapers" were news blogs printed on paper and if you subscribed they would be delivered daily to the front door of your house. Yes, by that time all the "news" in the paper would be obsolete. On Sundays they would include additional non-news articles of the golly-gee-whiz type.)

      The second result of the high oxygen concentration is even more catastrophic. It involves a terryifying phenomenon, fortunately known only in the laboratory, which scientists have christened “fire.”

     Many ordinary substances, when immersed in an atmosphere like that of Earth's and heated to quite moderate temperatures, begin a violent and continuous chemical reaction which does not cease until they are completely consumed. During the process, intolerable quantities of heat and light are generated, together with clouds of noxious gases. Those who have witnessed this phenomenon under controlled laboratory conditions describe it as quite awe-inspiring; it is certainly fortunate for us that it can never occur on Mars.

     Yet it must be quite common on Earth—and no possible form of life could exist in its presence. Obeservations of the night side of Earth have often revealed bright glowing areas where fire is raging; though some students of the planet have tried, optimistically, to explain these glows as the lights of cities, this theory must be rejected. The glowing regions are much too variable; with few exceptions, they are quite short-lived, and they are not fixed in location.

[These observations were doubtless due to forest fires and volcanoes—the latter unknown on Mars. It is a tragic irony of fate that had the Martian astronomers survived a few more thousand years, they would have seen the lights of man’s cities. We missed each other in time by less than a millionth of the age of our planets. —TRANSLATOR.]

From REPORT ON PLANET THREE by Arthur C. Clarke (1959)

(ed note: Warning: Spoilers for Asimov's "The Dust of Death"

organic chemist. He is know as that because the asshat regularly steals the ideas of his underlings and pretends that he invented them. Edmund Farley is one of those underlings, back after spending months on Saturn's moon Titan, working on an improved hydrogenation procedure. He is incandescent with rage when Llewes steals his idea. Farley decides to murder Llewes, but wants to make it seem like an accident.)

      Then what about the atmosphere room? Llewes’ routine of testing, his almost infinite caution, left nothing to chance. Any tampering with the equipment itself, unless it were unusually subtle, would certainly be detected.
     Fire then? The atmosphere room contained inflammable materials and to spare, but Llewes didn’t smoke and was perfectly aware of the danger of fires. No one took greater precautions against one.
     All those little tanks of gas; each its own color; each a synthetic atmosphere. Hydrogen gas in red cylinders and methane in striped red and white, a mixture of the two representing the atmosphere of the outer planets. Nitrogen in brown cylinders and carbon dioxide in silver for the atmosphere of Venus. The yellow cylinders of compressed air and the green cylinders of oxygen, where Earthly chemistry was good enough. A parade of the rainbow, each color dating back through centuries of convention.
     Then he had the drought. It was not born painfully, but came ail at once. In one moment, it had all crystallized in Farley’s mind and he knew what he had to do.

     Farley entered Central Organic Laboratories (to use its official tide) that night, certain he was unobserved. The labs weren’t banks or museums. They were not subject to thievery and such night-watchmen as there were had a generally easy-going attitude toward their jobs.
     Farley closed the main door carefully behind him and moved slowly down the darkened corridors toward the atmosphere room. His equipment consisted of a flashlight, a small vial of black powder, and a thin brush he had bought in an art-supply store at the other end of town three weeks before. He wore gloves.
     He cupped the flashlight and found the cylinder without hesitation. His heart was beating so as almost to deafen him, while his breath came quickly and his hand trembled.
     He tucked the flash under his arm, then dipped the tip of the artist’s brush into the black dust. Grains of it adhered to the brush and Farley pointed it into the nozzle of the gauge attached to the cylinder. It took eons-long seconds for that trembling tip to enter the nozzle.
     Farley moved it about delicately, dipped it into the black dust again and inserted it once more in the nozzle. He repeated it over and over, almost hypnotized by the intensity of his own concentration. Finally, using a bit of facial-tissue, dampened with saliva, he began to wipe off the outer rim of the nozzle, enormously relieved that the job was done and he’d soon be out.
     It was then his hand froze, and the sick uncertainty of fear surged through him. The flashlight dropped clattering to the floor.
     Fool! Incredible and miserable fool! He hadn’t been thinking!
     Under the stress of his emotion and anxiety, he had ended at the wrong cylinder!
     He snatched up the flash, put it out, and, his heart thumping alarmingly, listened for any noise.
     In the continuing dead silence, he regained a portion of his self-control, and screwed himself to the realization that what could be done once could be done again. If the wrong cylinder had been tampered with, then the right one would take two minutes more.
     Once again, the brush and the black dust came into play. At least, he had not dropped the vial of dust; the deadly, burning dust. This time, the cylinder was the right one.
     He finished, wiping the nozzle again, with a badly trembling hand. His flash then played about quickly and rested upon a reagent bottle of toluene. That would do. He unscrewed the plastic cap, splashed some of the toluene on the floor and left the bottle open.
     He then stumbled out of the building as in a dream, made his way to his rooming house and the safety of his own room. As nearly as he could tell, he was unobserved throughout.
     He disposed of the facial tissue he had used to wipe the nozzles of the gas cylinders by cramming it into the cigarette-ash disposal unit. It vanished into molecular dispersion. So did the artist's brush that followed.

     Now that it had all been done, would it work? Llewes might ignore the smell of toluene. Why not? The odor was unpleasant, but not disgusting. Organic chemists were used to it.
     Then, if Llewes were still hot on the trail of the hydrogenation procedures Farley had brought back from Titan, the gas cylinder would be put into use at once. It would have to be. With a day of holiday behind him, Llewes would be more than usually anxious to get back to work.
     Then, as soon as the gauge-cock was turned, a bit of gas would spurt out and turn into a sheet of flame. If there were the proper quantity of toluene in the air, it would turn as quickly into an explosion—
     So intent was Farley in his reverie, that he accepted the dull boom in the distance as the creation of his own mind, a counterpoint to his own thoughts, until footsteps thudded by.

(ed note: Llewes is killed in the explosion. Farley is happy now: the chemical process he discovered will remain in his name, everybody thinks that Llewes died in an accident, and even if foul play is suspected, how can they possibly trace it back to him? All of Llewes other employees want to kill him as well.

Unfortunately for Farley, H. Seton Davenport of the Terrestrial Bureau of Investigation is on the case. Dr. Gorham, Llewes's assistant, is quite sure this was no accident. Llewes was a fanatic about safety measures, this was murder.)

     "And now you want to find someone to punish?” said Davenport. "You want to make up to the dead Llewes your crime against the live one?”
     "No! Leave psychiatry out of this. I tell you it is murder. It’s got to be. You don’t know Llewes. The man was a monomaniac on safety. No explosion could possibly have happened anywhere near him unless it were carefully arranged."
     Davenport shrugged. "What exploded, Dr. Gorham?”
     “It could have been almost anything. He handled organic compounds of all sorts: benzene, ether, pyridine. All of them inflammable.”
     "I studied chemistry once, Dr. Gorham, and none of those liquids are explosive at room temperature as I remember. There has to be some sort of heat; a spark, a flame.”
     "There was fire all right."
     "How did that happen?”
     "I can’t imagine. There were no burners in the place and no matches. Electrical equipment of all sorts was heavily shielded. Even little ordinary things like clamps were specially manufactured out of beryllium-copper or other non-sparking alloys. Llewes didn't smoke and would have fired on the spot anyone who approached within a hundred feet of the room with a lighted cigarette.”
     "What was the last thing he handled, then?”
     "Hard to tell. The place was a shambles.”
     "I suppose it has been straightened out by now, though.”
     The chemist said with instant eagerness, "No, it hasn’t. I took care of that. I said we had to investigate the cause of the accident to prove it wasn’t neglect. You know, to avoid bad publicity. So the room hasn't been touched.”
     Davenport nodded. "All right. Let’s take a look at it.”
     In the blackened, dishevelled room, Davenport said, "What’s the most dangerous piece of equipment in the place?”
     Gorham looked about. "The compressed oxygen tanks,” he said, pointing.
     Davenport looked at the variously colored cylinders standing against the wall cradled in a binding chain. Some leaned heavily against the chain, tipped by the force of the explosion.
     Davenport said, “How about this one?” He toed a red cylinder which lay flat on the ground in the middle of the room. It was heavy and didn’t budge.
     "That one’s hydrogen,” said Gorham.
     “Hydrogen is explosive, isn’t it?”
     “That's right—when heated."
     Davenport said, “Then why do you say the compressed oxygen is the most dangerous. Oxygen doesn’t explode, does it?”
     "No. It doesn’t even burn, but it supports combustion, see. Things burn in it."
     “Well, look here.” A certain vivacity entered Gorham’s voice; he was the scientist explaining something simple to the intelligent layman. “Sometimes a person might accidentally put some lubricant on the valve before tightening it onto the cylinder, to make a tighter seal, you know. Or he might get something inflammable smeared on it by mistake. When he opens the valve then, the oxygen rushes out, and whatever goo is on the valve explodes, wrenching off the valve. Then the rest of the oxygen blows out of the cylinder which would then take off like a miniature jet and go through a wall; the heat of the explosion would fire other inflammable liquids nearby."
     "Are the oxygen tanks in this place intact?”
     “Yes, they are,"
     Davenport kicked the hydrogen cylinder at his feet. "The gauge on this cylinder reads zero. I suppose that means it was in use at the time of explosion and has emptied itself since then.”
     Gorham nodded. "I suppose so.”
     “Could you explode hydrogen by smearing oil on the gauge?”
     "Definitely not."
     Davenport rubbed his chin. "Is there anything that would make hydrogen burst into flame outside of a spark of some sort?"
     Gorham muttered, “A catalyst, I suppose. Platinum black is the best. That’s powdered platinum.”
     Davenport looked astonished. "Do you have such a thing?”
     “Of course. It’s expensive, but there’s nothing better for catalyzing hydrogenations.” He fell silent and stared down at the hydrogen cylinder for a long moment. "Platinum black,” he finally whispered. “I wonder—”
     Davenport said, “Platinum black would make hydrogen burn, then?”
     "Oh, yes. It brings about the combination of hydrogen and oxygen at room temperature. No heat necessary. The explosion would be just as though it were caused by heat, just the same."
     Excitement was building up in Gorham's voice and he fell to his knees beside the hydrogen cylinder. He passed his finger over the blackened tip. It might be just soot and it might be—”
     He got to his feet, “Sir, that must be the way it was done. I’m going to get every speck of foreign material off that nozzle and run a spectrographic analysis.”

(ed note: Gorham finds very faint traces of platinum black on the nozzle. Davenport has a forensic chemist from the Bureau of Investigation check everything in the entire lab.)

     The next morning, Gorham was in Davenport’s office again. This time, he had been summoned.
     Davenport said, “It’s murder, all right. A second cylinder had been tampered with.”
     "You see!"
     "An oxygen cylinder. There was platinum black inside the tip of the nozzle. Quite a bit of it.”
     “Platinum black? On the oxygen cylinder?”
     Davenport nodded. "Right. Now why do you suppose that would be?”
     Gorham shook his head. "Oxygen won’t burn and nothing will make it burn. Not even platinum black.”
     “So the murderer must have put it on the oxygen cylinder by mistake in the tension of the moment. Presumably he corrected himself and tampered with the right cylinder, but meanwhile he left final evidence that this is murder and not accident.”
     "Yes. Now it’s only a matter of finding the person.”

(ed note: They try to narrow it down by expertise and alibis, but it is hopeless. They will have to deduce the murderer by other means.)

     Davenport said, "The only point of attack, it seems to me, is the platinum black on the oxygen cylinder. It’s an irrational point and the explanation may hold the solution. But I’m no chemist and you are, so if the answer is anywhere it’s inside you. Could it have been a mistake—could the murderer have confused the oxygen with the hydrogen?”
     Gorham shook his head at once. “No. You know’ about the colors. A green tank is oxygen; a red tank is hydrogen.”
     "What if he were color-blind?" asked Davenport.
     This time Gorham took more time. Finally, he said, "No. Colorblind people don’t generally go in for chemistry. Detection of color in chemical reactions is too Important. And if anybody in this organization were color-blind, he’d have enough trouble with one thing or another so that the rest of us would know about it.”
     Davenport nodded. He fingered the scar on his cheek absently. "All right. If the oxygen cylinder wasn’t smeared by ignorance or accident, could it have been done on purpose? Deliberately?"
     "I don’t understand you."
     "Perhaps the murderer had a logical plan in mind when he smeared the oxygen cylinder, then changed his mind. Are there any conditions where platinum black would be dangerous in the presence of oxygen? Any conditions at all? You’re the chemist, Dr. Gorham.”

     There was a puzzled frown on the chemist’s face. He shook his head. "No, none. There can’t be. Unless—”
     "Well, this is ridiculous, but if you stuck the oxygen jet into a container of hydrogen gas, platinum black on the gas cylinder could be dangerous. Naturally, you’d need a big container to make a satisfactory explosion.”
     "Suppose,” said Davenport, "our murderer had counted on filling the room with hydrogen and then having the oxygen tank turned on.”
     Gorham said, with a half-smile, "But why bother with the hydrogen atmosphere when—” The half-smile vanished completely while a complete pallor took its place. He cried, “Farley! Edmund Farley!”
     "What’s that?”
     "Farley just returned from six months on Titan,” said Gorham, in gathering excitement. "Titan has a hydrogen-methane atmosphere. He is the only man here to have had experience in such an atmosphere and it all makes sense now. On Titan, a jet of oxygen will combine with the surrounding hydrogen if heated, or treated with platinum black. A jet of hydrogen won’t. The situation is exactly the reverse of what it is here on Earth. It must have been Farley. When he entered Llewes' lab to arrange an explosion, he put the platinum black on the oxygen, out of recent habit. By the time he recalled that the situation was the other way round on Earth, the damage was done.”

From THE DUST OF DEATH by Isaac Asimov (1957)

      The view from Grandma’s picture window was famous—but by reputation only, since few indeed had been privileged to see it with their own eyes. Her home was partly countersunk into a ledge overlooking the dried-up bed of Loch Hellbrew and the canyon that led into it, so it presented her with a 180-degree panorama of Titan’s most picturesque landscape. Sometimes, when storms raged through the mountains, the view disappeared for hours behind clouds of ammonia crystals. But today the weather was clear and Duncan could see for at least twenty kilometers.

     “What’s happening over there?” he asked.
     At first, he had thought it was one of the fire fountains that sometimes erupted in unstable areas; but in that case the city would have been in danger, and he would have heard of it long ago. Then he realized that the brilliant yet smoky column of light burning steadily on the hill crest three or four kilometers away could only be man-made.
     “There’s a fusor running over at Huygens. I don’t know what they’re doing, but that’s the oxygen burn-off.”
     “Oh, one of Armand’s projects. Doesn’t it annoy you?”
     “No—I think it’s beautiful. Besides, we need the water. Look at those rain clouds… real rain. And I think there’s something growing over there. I’ve noticed a change in color on the rocks since that flame started burning.”
     “That’s quite possible—the bioengineering people will know all about it. One day you may have a forest to look at, instead of all this bare rock.”
     He was joking, of course, and she knew it. Except in very restricted areas, no vegetation could grow here in the open. But experiments like this were a beginning, and one day…
     Over there in the mountain, a hydrogen fusion plant was at work, melting down the crust of Titan to release all the elements needed for the industries of the little world. And as half that crust consisted of oxygen, now needed only in very small quantities in the closed-cycle economies of the cities, it was simply allowed to burn off.

     “Do you realize, Duncan,” said Grandma suddenly, “how neatly that flame symbolizes the difference between Titan and Earth?”
     “Well, they don’t have to melt rocks there to get everything they need.”
     “I was thinking of something much more fundamental. If a Terran wants a fire, he ignites a jet of hydrocarbons and lets it burn. We do exactly the opposite. We set fire to a jet of oxygen, and let it burn in our hydromethane atmosphere.”

     This was such an elementary fact of life—indeed an ecological platitude—that Duncan felt disappointed; he had hoped for some more startling revelation. His face must have reflected his thoughts, for Grandma gave him no chance to comment.
     “What I’m trying to tell you,” she said, “is that it may not be as easy for you to adjust to Earth as you imagine. You may know—or think you know—what conditions are like there, but that knowledge isn’t based on experience. When you need it in a hurry, it won’t be there. Your Titan instincts may give the wrong answers. So act slowly, and always think twice before you move.”

From IMPERIAL EARTH by Arthur C. Clarke (1975)

Making Oxygen

There are two methods of cracking CO2 into C and O2: low energy and high energy.

Low energy requires huge amounts of biomass in plants. Data from Biosphere II indicate roughly seven tons of plant life per person per day, with a need for roughly 4 days for a complete plant aspiration cycle, so call it 25 to 30 tons of plant per crewman. With an average density of 0.5, each ton of greenhouse takes up about 2 cubic meters (m3).

High energy methods take up much less space, but (as the name implies) requires inconveniently large amounts of energy. It also results in lots of messy by-products and waste heat.

Practically, it is easier to flush the CO2 instead of cracking it, and instead bringing along an extra supply of water to crack for oxygen. Water is universally useful with a multitude of handy applications, and takes less energy to crack than CO2.

For future Mars missions, it has been suggested that the life support system should utilize the Sabatier Reaction. This takes in CO2 and hydrogen, and produces water and methane. The water can split by electrolysis into oxygen and hydrogen, with the oxygen used for breathing and the hydrogen used for another batch of CO2. Unfortunately the methane accumulates, and its production eventually uses up all the hydrogen. The reaction does require one atmosphere of pressure, a temperature of about 300°, and a catalyst of nickel or ruthenium on alumina.

For emergency use, it would be wise to pack away a few Oxygen Candles. These are composed of a compound of sodium chlorate and iron. When ignited, they smolder at about 600°C, producing iron oxide (rust), sodium chloride (salt), and approximately 6.5 man-hours of oxygen per kilogram of candle. Molecular Product's Chlorate Candle 33 masses 12.2 kilos, cylindrical can dimensions of 16 cm diameter x 29 height, burns for 50 minutes, and produces 3400 liters of oxygen. On the ISS they use Vika (aka TGK) oxygen candles (NASA name Solid-Fuel Oxygen Generator or "SFOG"). Each has one liter of lithium perchlorate and can provide oxygen for one person for 24 hours. Each Vika burns for 5–20 minutes at 450–500 °C and produces 600 litres of oxygen.

Removing Carbon Dioxide

It is not enough to supply oxygen to breath, you also have to remove the carbon dixoide. Bad things happen if the CO2 levels rise too high. NASA says that each astronaut exhales 0.998 kilograms of carbon dioxide per day.

  • 0.04 percent - Typical level in Terra's atmosphere
  • At 1 percent - drowsiness
  • At 3 percent - impaired hearing, increased heart rate and blood pressure, stupor
  • At 5 percent - shortness of breath, headache, dizziness, confusion
  • At 8 percent - unconsciousness, muscle tremors, sweating
  • Above 8 percent - death

NASA uses Carbon Dioxide Scrubbers. In the Apollo program spacecraft, NASA used lithium hydroxide based scrubbers, which fill up and have to be replaced. Oxygen tanks have enough to last for the duration of the mission, and is gradually used up. Actually it is converted into carbon dioxide and is absorbed into the scrubbers, where it cannot be used any more.

You may remember all the excitement during the Apollo 13 disaster, when NASA learned the life-threatening dangers of non-standardization. The crew had to use the Command Modules' scrubber cartridges to replace the ones in the Lunar module. Unfortunately, due to lack of standardization, the CM cartridges would not fit into the LM life support system (CM's were square, LM were cylindrical). They had to rig an adaptor out of duct tape and whatever else was on-board.

In the Space Shuttle, NASA moved to a Regenerative carbon dioxide removal system. Metal-oxide scrubbers remove the CO2 as before. But when they get full, instead of being replaced, they can have the CO2 flushed out by running hot air through it for ten hours. Then they can be reused.

In the TransHab design, they use a fancier system to remove carbon dioxide and replace it with oxygen. Actually it recycles the oxygen, plucking it out of the carbon dioxide molecules and returning it to the atmosphere to be breathed once again.

Note that the system does not affect the nitrogen inert gas, so it stays at the proper level.

In the following specifications, the mass (kg), volume (m3), and electrical power requirements (W) is for equipment sized to handle a six person crew.

First the stale air is pumped through a 4-Bed Molecular Sieve (217.7 kg, 0.6 m3, 733.9 W). It initially removes the water from the air (and sends it to be added to the life support water supply), then it removes the carbon dioxide.

The carbon dioxide and some hydrogen (from a source to be explained shortly) are fed into a Sabatier Reactor (26 kg, 0.01 m3, 227.4 W). They react producing methane and water: CO2 + 4 H2 → CH4 + 2 H2O + energy.

The methane is vented into space. The water is fed into an electrolyser to be split into hydrogen and oxygen. Specifically a Solid Polymer Electrolysis (SPE) Oxygen Generation Subsystem (OGS) (501 kg, 2.36 m3, 2004 W).

The hydrogen is sent back to the Sabatier Reactor to take care of the next batch of carbon dioxide. The oxygen is added to the breathing mix and released into the habitat module's atmosphere.

The TransHab starts out with a tank of high pressure oxygen (20.4 kg, 0.78 m3, 6W, 30 MPa) and a tank of high pressure nitrogen (94.4 kg, 3.6 m3, 6W, 30 MPa). The oxygen tank has three days worth of breathing for six crew, enough to give the Sabatier Reactor time to get started. The nitrogen tank has enough to establish the proper ratio for the breathing mix, and some extra to compensate for any atmosphere leaking into space.


(ed note: the cargo ship suffered an impact with a with a coronal mass ejection. Though the ship's electrical system has protection, the EMP surge inexplicably shorts out several systems. While damage control tries to put the ship back to rights, protagonist Ishmael reports back to his post in the Environmental life support room. Instantly he notices that something is very wrong...)

      I felt almost chipper when I stepped back through the hatch into Environmental. The smell hit me the moment I entered.
     “What’s the matter?” I asked as I opened the hatch.
     Brill, Diane and Francis stood gathered around the console. They looked up when I spoke and Brill said, “What do you mean? The ship’s had EMP damage.”
     “No, what smells?” I asked.
     Diane laughed. “It’s Environmental. It’s supposed to smell.”
     Brill frowned and straightened up, testing the air with her nose. “He’s right. The smell is off.”
     Diane said, “Can’t be. Most of the smell comes from the scrubbers, and I checked them when I first got here.”
     “Check them again,” Brill ordered.
     While Diane and Brill went off to check the scrubber cabinets, I looked at the diagnostics running on the console. “Something wrong with it?”
     Francis shook his head. “Nothing. Just waiting for ShipNet.”
     “ShipNet is up. I just came from the bridge.”
     He looked startled and punched the reset to kill the diagnostic run. The console came up with the standard displays. Water was good. Air was good. CO2 was climbing. Not a lot but definitely on the rise.
     “Brill?” Francis called.
     I heard Diane say, “Uh, oh.”
     Francis and I looked at each other and bolted for the scrubber cabinets.

     When we got there, Brill was already on the radio to (First Officer) Mr. Kelley. “Yes, sar (gender-neutral substitute for "sir"),” she said, “all four scrubbers are contaminated (scrubbers contain photosyntheic bacteria which consume CO2 and produce O2). I don’t know by what, but the matrices are already showing deterioration.”
     “CO2 levels okay?” His voice sounded tinny on the little radio.
     Brill looked at Francis who nodded but pointed upwards. “Yes, sar, for now, but they’re climbing.” She watched Francis to confirm what she was saying and he nodded.
     “Do what you can, B,” he said. “Lemme know if it gets worse.”
     “Aye, aye, sar. Environmental, out.” She turned to Diane. “What have we got?”
     “Dunno. Never seen anything like this. It’s like they’ve been poisoned by something.” Her face pressed close to the matrix. “Seems like the phycoerythrin is breaking down in the cells.”
     Phycoerythrin was the pigment tracer that identified the photosynthesis receptors in the bacteria. No phycoerythrin meant no photosynthesis and no carbon dioxide scrubbing. Normally the algae was a reddish-brown, but presently they were turning a kind of blue.

     “Would particulates do that?” I asked.
     “What kind of particulates?” Brill said.
     “Smoke, burned circuits, melting plastic? I don’t know. When I was on the bridge I checked levels, we were okay on O2 and CO2 but the particulates were high. I bipped it to you, remember?”
     “I do, but that shouldn’t cause this. That’s what the field plates are for. They pull all that junk out of the air mixture before it hits the matrix.”
     “True. If they’re running,” I said. I crossed to the panels for the field plates on the number two scrubber. I opened the inspection door and looked inside. “Brill? Shouldn’t there be a plate in here?” I asked knowing the answer myself, but not really believing my eyes.
     “What are you talking about?” she asked, coming around the scrubber and crouching down to look in beside me.
     “The plate’s gone,” I said. “There’s nothing but empty mounting brackets.”
     Francis and Diane came to look over our shoulders. “Pixies?” Francis asked.
     “Too heavy for a pixie,” Diane said. “Those things mass a good five kilos.”
     “Well if they were fast pixies maybe they stole the plate while the gravity was out.”
     “That’s it!” I said.
     They all looked at me. “Ish,” Diane said, “we were kidding about the pixies.”
     I grinned. “I’m not.” I got down and stuck my head in the door so I could look up to where the other half of the field mechanism ran across the top of the intake vent. “Yup. Pixies.” My voice echoed weirdly inside the cabinet.
     Brill nudged me so she could get a look. “Damn it!” she said.

     When she pulled her head out, I could see she was already calculating. “How fast can we change out all four scrubbers?”
     “With all of us working it would take four stans (standard hours). But it’ll take more than half a day before they begin working again.” Diane confirmed what we already knew.
     When I had first come aboard, this practice of stating and restating the obvious confused me. Now I recognized it as a kind of mutual reality check for the group to make sure everyone had an idea of what the other person was thinking.
     “Francis,” Brill said, “go run the numbers. How much time do we have? Diane, Ish, start on number three. Pull the frames and strip ’em out as fast as you can.”
     He bolted for the console and Brill called Mr. Kelley. “Environmental reporting, you’ll need to see this, sar. It’s serious and won’t take long.”
     Diane and I had done this as a team for so long we had three of the matrix frames out before she finished speaking.

     Mr. Kelley showed up in two ticks (minutes). “Whatcha got, Brill?” he asked.
     She took him back to the scrubber and showed him where the field plate was supposed to be. “What the—?” he said as he dragged his head out of the cabinet. “How’d it get up there and what’s holding it?”
     “Magnetism,” she said. “Francis, would you kill the power to number two scrubber please?”
     “Securing power to number two now.”
     When he said “now” the missing scrubber plate dropped with a clank and bounced out of the inspection hatch at Mr. Kelley’s feet.
     “How are they normally connected to the base?” Mr. Kelley asked. Brill answered, “They just sit in those sockets. While the power is flowing, they’re locked down magnetically.”
     “So, when we lost power, we lost the lock, grav failed long enough for it to unseat, and when the power came back on, the field kicked in with the plate out of position.”
     “No field plate, dirty matrices, dead bacteria,” Brill finished. “How much time, Francis? I need to know now.”
     “Ten hours until CO2 reaches critical,” he called back.
     “Oh, sh*t,” Mr. Kelley said.

     Francis came in to help me and Diane while Brill conferred with Mr. Kelley. “Can you get me somebody to fix these plates while we clear the matrices? I don’t wanna put good matrix back in a dirty stream.”
     He pulled out his comm and started making calls.
     With Brill and Francis helping, we got number three stripped down and restarted within a stan. Mr. Kelley fixed number three’s field plate himself and tested it for us to make sure it worked. While he was working, his back up team including Bert Benson, Janice Ivanov, and Arvid Xia came in. He set them to work on the other field collector plates and by the time we’d finished with number three’s frames and had them reloaded, the other ones were ready for us.
     Francis, Diane, and I started on number one scrubber while Brill consulted with Mr. Kelley. “We’re going to be desperately close, Fred,” she said. I didn’t like that she was calling him Fred. It meant things were really as bad as I had thought.

     “I know, B. We can add more oxygen, but we have to get rid of the CO2. How much calcium hydroxide do we have?
     “About eight tons but how do we get enough air over it?”
     Calcium hydroxide was a natural CO2 absorbent. We kept a supply on board but I hadn’t been sure what we used it for. Now it all made sense. The problem was surface area.
     I kept slopping frames as fast as I could. Diane was pulling them out and handing them to Francis and I. We were pulling dying matrix out as fast as we could split the frames and we were darn fast.
     Brill was asking, “Can we rig up some kind of canister filter with it in it? Like they use on the little ships?”
     Mr. Kelley had his tablet out now and was running figures. “Too much air, the canisters would calcify into limestone too quickly. We need some way to expose as much surface as we can.”
     I finished stripping out the latest matrix and bent to stretch my back. “Spine!” I shouted.
     Diane handed me the next frame and I kept working as I talked. “The spine. It’s like a big straw.” I finished stripping matrix and tossed the empty frame into the wash me pile. Diane handed me the next one. “It’s only about two meters wide, but it’s two hundred meters long. Spread the calcium hydroxide on the floor, CO2 is heavier than oxygen and it’ll pool between the hatch combings. If the powder calcifies, we can scrape it up, put down more powder, and drop the limestone out the lock.” Diane handed me another frame.
     Mr. Kelley pulled out a tablet and punched numbers.
     We finished stripping down number one and broke out the hoses to wash it all down before breaking out fresh matrix. We started laying down cleaned frames. Francis and I made them up, Diane sprayed them with new bacteria, and Brill hung them before he stopped running numbers.

     “It’s gonna get stuffy in here, but it might work. We need to increase flow or the CO2 will pool in the lower parts of the fore and aft sections.”
     Brill said, “Run a long exhaust duct from the lifeboat deck to the after section. Pull everybody you can out of there. Blow the air from the boat deck into the after section and let the pressure differentials bring the fresh air back. You can set up a little bit of circulation and keep the highest levels of CO2 running across the surface.”
     He added that to his calculations as we finished with number one. The problem was not in getting them rebuilt, it was the time it would take for the algae to bloom and begin scrubbing. We were shaving off a few valuable minutes by working quickly, but we were short by too many to make much difference if we couldn’t manage to control the overall CO2 levels.
     “Better,” he said. “Might be enough.” He pulled out his comm, headed for the hatch, and was lining up people and equipment before he left the section.

     We kept building frames. Diane latched the lid back down on number one and I looked at the chrono, 2200. If I were still alive at 0900, we’d probably make it.
     We started on number four and nobody talked. We just worked.
     By 2330 we had all the scrubbers rebuilt, and settled down to check the numbers. CO2 was still climbing, but the engineering crew hadn’t finished rigging the duct work. Some of the Deck gang had been put to work spreading the calcium hydroxide on the deck along the spine. They were shooting for two, five-centimeter-deep strips along either side of the spine with about a half meter open area in the middle to walk on. It would take almost all the powder we had to cover that much space but it gave us a large surface area to stream the CO2 laden air across.
     By 0200 the CO2 was almost at alarm critical levels and the crew had started up the blowers to push the heavy air all the way down the spine. As the pressure differential between the bow and stern sections built up, the air they pumped aft began working forward through the spine and across the absorbent powder.
     By 0400 the CO2 levels had stopped rising but just moving around was difficult. Everybody was yawning. Of course, that might have had something to do with everybody being exhausted, too. The air felt even heavier than normal in Environmental.

     By 0500 the CO2 levels started rising again. The engineering crew found that the powder had formed a crust preventing additional absorption where the calcium hydroxide had reached its capacity. We all went out with brooms and broke the crust to expose the powder underneath to the air. It was hard to move and the brooms grew heavy.
     By 0800 the CO2 levels began falling again. The scrubbers came online a bit faster than we had expected. It was still hard to breathe and I had a pounding headache, but I began to see smiles.
     By 0900 we knew we had it beaten. Two of the four scrubbers were stripping out CO2 at maximum capacity, the third was running at about fifty percent and the last was kicking in about twenty percent.

     At 0930 the overheads piped and the captain’s voice came over the speakers. “This is the captain speaking. Full power should be restored within the hour. The CO2 and O2 levels are getting back to normal range. The sail generators should be back online this afternoon. We’ll be a couple of days late, but we’ll arrive thanks to your hard work, dedication, and ingenuity. You make me proud. That is all.”

From FULL SHARE by Nathan Lowell (2011)

     ..."That puts me in mind of something that happened to me when I was 'farmer' in the old Percival Lowell — the one before the present one," Yancey went on. "We had touched at Venus South Pole and had managed somehow to get a virus infection, a sort of rust, into the 'farm' — don't look so superior, Mr. Jensen; someday you'll come a cropper with a planet that is new to you!"
     "Me, sir? I wasn't looking superior."
     "No? Smiling at the pansies, no doubt?"
     "Yes, sir."
     "Hmmph! As I was saying, we got this rust infection about ten days out. I didn't have any more farm than an Eskimo. I cleaned the place out, sterilized, and reseeded. Same story. The infection was all through the ship and I couldn't chase it down. We finished that trip on preserved foods and short rations and I wasn't allowed to eat at the table the rest of the trip."

     "Yes, Dodson?"
     "What did you do about air-conditioning?"
     "Well. Mister, what would you have done?"
     Matt studied it. "Well, sir, I would have jury-rigged something to take the Cee-Oh-Two out of the air."
     "Precisely. I exhausted the air from an empty compartment, suited up, and drilled a couple of holes to the outside. Then I did a piping job to carry foul air out of the dark side of the ship in a fractional still arrangement — freeze out the water first, then freeze out the carbon dioxide. Pesky thing was always freezing up solid and forcing me to tinker with it. But it worked well enough to get us home."

From SPACE CADET by Robert Heinlein (1948)

"Check the oxygen supplies first," the voice of Thorndyke, the head engineer, suggested.

Bart and Dan went off to do that, and Jim followed behind them. But from their faces, he could tell that their hopes weren't too high. Obviously, most of the oxygen had been put into the new extension, since there was more room there for the big containers of liquid oxygen. They had been in the shadow, below the main part of the hull, where they could stay liquid; but the heat of the fire had bent and twisted them, and some had even exploded violently.

"Takes three pounds of oxygen a day for a man," Dan said. "You'll find the amount on the outside of the tanks. Gauge will tell you what per cent has been used." He went back into the rear extension, leaving Bart and Jim to count the amount in the original hut. It was a lot less than they would have liked.

"According to those figures, we've got just enough air left for all the men here for about thirty hours! And we don't have chemicals to soak up the carbon dioxide they breathe out for even that long."

"The big problem's in getting rid of the carbon dioxide," Thorndyke said flatly. "If we could handle that, we might just barely survive until the storm had let up enough for another ship to try.

In a vague way, Jim still felt responsible for the trouble. He should have checked on his assistant. He'd been beating his head, trying to remember what he'd learned in high school about the behavior of the gas. His father had always maintained that a man could accomplish almost anything by reducing things down to the basic characteristics, and then finding out what was done in other fields.

"It's a heavy gas," someone said suddenly. "If we all climb up to the top where the lighter oxygen is . . ."

He realized his mistake before the others swung on him. Thorndyke chuckled grimly. "It's the same here as anything else—neither light nor heavy," he pointed out. "But all the same, you're moving in the right direction. What are the basic characteristics of carbon dioxide?"

The young man who'd studied chemistry piped up again. "It's a heavy gas, composed of one atom of carbon and two of oxygen. Animals breathe it out, and plants breathe it in, releasing the oxygen again. It freezes directly to a solid, without any real liquid state, and is then known as dry ice. It evaporates . . ."

"It freezes at a higher temperature than air!" Jim shouted. "That's how they make dry ice—they lower the temperature enough for carbon dioxide to freeze, but the rest of the atmosphere stays a gas. What about the cold side—does it get cold enough to freeze it out?"

"How cold?" Thorndyke asked. "Never mind." He reached over for a copy of the Handbook of Chemistry and Physics and ran through it. "If we didn't pass it through too fast, our air would probably lose most of the gas from the cold. Dan, any way to get a gastight pan . . ."

"You've got the pipes under the solar mirror trough," Dan pointed out. "They're all coupled up. We could blow it through there slowly enough—trial and error should tell us how slowly."

From STEP TO THE STARS by Lester Del Rey (1954)


In most space program, they use two different breathing mixes for the atmosphere inside space suits and habitat modules. Space suits use Low Pressure (pure oxygen at 32.4 kiloPascals [kPa]) and habitat modules use High Pressure (breathing mix at 101.3 kPa). High pressure breathing mix is pretty close to ordinary Terran air at sea level.

Breathing Mix
32.4 kPa
(4.7 psi)
5.3 kPa
(0.77 psi)
53.3 kPa
(7.73 psi)
32.4 kPa
(4.7 psi)
70.7° C
101.3 kPa
(14.5 psi)
25.2 kPa
(3.7 psi)
254.0 kPa
(36.8 psi)
21.3 kPa
(3.1 psi)
100° C
  • Mix: Name of breathing Mix
  • Pressure: Normal atmospheric pressure of breathing mix
  • Oxygen Percent: Percentage of the gas that is oxygen
  • Anoxia Below Pressure: Death by anoxia if atmospheric pressure drop below this
  • Oxygen Toxicity Above Pressure: Death by oxygen toxicity of atmospheric pressure rises above this
  • Oxygen Partial Pressure: Pressure of the oxygen component
  • Water Boiling Point: Temperature at which water boils at this pressure

The important thing to note is that for a low pressure breathing mix (space suit), the crew will die of anoxia if the atmospheric pressure falls below 5.3 kPa and the crew will die of oxygen toxicity if the pressure rises above 53.3 kPa.

For a high pressure breathing mix (habitat module), anoxia lies below 25.2 kPa and oxygen toxicity is above 254.0 kPa.

How do you calculate safe breathing mixes for yourself?

The basic limit is anoxia ocurrs when the Partial Pressure of oxygen drops below 5.3 kPa and oxygen toxicity ocurrs when the partial pressure of oxygen rises above 53.3 kPa.

How do you calculate the partial pressure of oxygen?

pO2 = pMix * O%

pMix = pO2 / O%


  • pO2 = partial pressure of oxygen (kPa)
  • pMix = pressure of the atmosphere (kPa)
  • O% = percentage of breathing mix that is oxygen (0.0 to 1.0)

High pressure breathing mix is 21% oxygen (0.21). Anoxia will hit the crew when the atmospheric pressure drops to what pressure? (anoxia pO2 = 5.3 kPa)

pMix = pO2 / O%
pMix = 5.3 / 0.21
pMix = 25.2 mPa

Low pressure is attractive; since it uses less mass and the atmosphere will escape more slowly through a meteor hole. Unfortunately the required higher oxygen level make living in such an environment as hazardous as chain-smoking inside a napalm factory. NASA found that out the hard way in the Apollo 1 tragedy. Since then NASA always uses high pressure, they use low pressure in space suits only because they cannot avoid it.

This does raise a new problem. There is a chance that the high-oxygen atmosphere will allow a meteor to ignite a fire inside the suit. There isn't a lot of research on this, but NASA seems to think that the main hazard is a fire enlarging the diameter of the breach, not an astronaut-shaped ball of flame.

The increased fire risk is one reason why NASA isn't fond of low-pressure/high oxygen atmospheres in the spacecraft proper. There are other problems as well, the impossibility of air-cooling electronic components and the risk of long-term health problems being two. Setting up the optimal breathable atmosphere is complicated.

A more annoying than serious problem with low pressure atmospheres is the fact that they preclude hot beverages and soups. It is impossible to heat water to a temperature higher than the local boiling point. And the lower the pressure, the lower the boiling point. You may have seen references to this in the directions on certain packaged foods, the "high altitude" directions.

At the 32.4 kPa low pressure and pure oxygen used in space suits, water boils at 70.7° C. This is a tepid 160° F.

At 101.3 kPa 20% oxygen used in habitat modules, water boils at pretty much the same temperature as at sea level on Terra: 100° C.

At the zero kPa which we find in the vacuum of space, any heat at all will cause water to boil. In vacuum tests, astronauts reported that the saliva on their tongue would start to boil.

The temperature can be increased if one uses a pressure cooker, but safety inspectors might ask if it is worth having a potentially explosive device onboard a spacecraft just so you can have hot coffee.


The travelers paused here to open a few food packs and make some coffee in the pressure kettle. One of the minor discomforts of life on the Moon is that really hot drinks are an impossibility—water boils at about seventy degrees centigrade in the oxygen-rich, low-pressure atmosphere universally employed. After a while, however, one grows used to lukewarm beverages.

(ed note: at 32.4 kPa low pressure and pure oxygen, water boils at 70.7° C)

From EARTHLIGHT by Arthur C. Clarke (1955)

The Bends

Decompression sickness (also known as DCS, divers' disease, the bends or caisson disease) is one of the more hideous dangers of living in space.

It occurs when a person has been breathing an atmosphere containing inert gases (generally nitrogen or helium) and they move into an environment with lower pressure. This is commonly when they put on a soft space suit and open the airlock door. Or the room suffers an explosive decompression.

Note this does NOT happen if the person moves into an area with higher pressure or the same pressure (unless the new area has a different ratio of breathing mix).

DCS has all sorts of nasty effects, ranging from joint pain and rashes to paralysis and death. The large joints can suffer deep pain from mild to excruciating. Skin can itch, feel like tiny insects are crawling all over, mottling or marbling, swell, and/or suffer pitting edema. The brain can have sudden mood or behavior changes, confusion, memory loss, hallucinations, seizures, and unconsciousness. The legs can become paralyzed. Headache, fatigue, malaise, loss of balance, vertigo, dizziness, nausea, vomiting, hearing loss, shortness of breath, and urinary or fecal incontinence: the list just goes on and on.

During the construction of the Brooklyn Bridge in 1870, the workers constructing the bridge's pressurized caissons would sometimes be stricken by the horror of DCS. In a fit of gallows humor, the affliction was nicknamed "the Bends" after the "Grecian Bend". The Grecian kind was a stooped posture and scandalous dance move from 1820. The pressure kind characteristically caused its sufferers to agonizingly arched their backs in a manner vaguely similar to the Grecian kind. Oh, what cruel jests they practiced in the 1800s.

Why does DCS happen? Well, imagine a can of your favorite carbonated soda beverage. Shake it up, and nothing happens. But when you open it, the soda explodes into foam and sprays everywhere. When you open the container of shaken soda, you lower the pressure on the soda fluid. This allows all the dissolved carbon dioxide in the soda to un-dissolve, creating zillions of carbon dioxide bubbles, forming a foam.

Now imagine that the carbon dioxide is nitrogen, the drink is the poor astronaut's blood in their circulatory system, and the foam is the deadly arterial gas embolisms. That's what causes the bends.

This is also why DCS does not happen if you go into a higher pressure area. That makes the foam vanish, not appear. If you open a bottle of soda with a twist-top lid and it starts to foam, you can stop the foaming by screwing the lid back on. And you can make the foam vanish if you had some way of repressurizing the bottle.

Please note that sometimes the bends can occur if one moves from one habitat to another that has the same pressure, but a different ratio of breathing mix (the technical term is "Isobaric counterdiffusion"). Spacecraft of different nations or models might use different breathing mixes, beware or be bent. In fact, rival astromilitaries might deliberately utilize odd-ball breathing mixes, to make life difficult for enemy boarding parties invading their ships. I'm sure the defending Espatiers will be more than happy to put the invading boarding party members out of their misery as they writhe in torment on the deck with arched backs. I'm sure the espatiers will have some sarcastic term for such a maneuver, something along the lines of making a Grecian dance party.

The bends can be prevented by slow decompression, and by prebreathing. Or by breathing an atmosphere containing no inert gases. Slow decompression works great for deep-sea divers but NASA does not favor it for space flight. An atmosphere with no inert gases (pure oxygen) is an insane fire risk. NASA does not allow a pure oxygen atmosphere in spacecraft and space stations, at least not after the Apollo 1 tragedy. On the other hand, NASA will allow it in space suit, in a desperate attempt to lower the suit pressure to the point where the astronaut can move their limbs instead of being trapped into a posture like a star-fish or Saint Andrew's Cross.


So NASA astronauts do a lot of prebreathing when getting ready to do a spacewalk. This flushes nitrogen out of the blood stream and keeps the bends away. NASA uses Terra-normal pressure (14.7 psi) inside the Space Shuttle, but only 0.29 pressure (4.5 psi) with pure oxygen in the space suits. The prebreathing is officially called the In Suit Light Exercise (ISLE) Prebreath Protocol, and unofficially called the "Slow Motion Hokey Pokey".

The astronaut(s) enter the airlock, and the airlock pressure is reduced to 10.2 psi. They breath pure oxygen through masks for 60 minutes (because the air in the airlock contains nitrogen). They then put on their space suits and do an EMU purge (i.e., flush out all the airlock-air that got into the suit while they were putting it on, to get rid of stray nitrogen). The air inside their suits is now also pure oxygen. The airlock pressure is then brought back up to the normal 14.7 psi. They then do 100 minutes of in-suit prebreath. Of those 100 minutes, 50 of them are light-exercise minutes and 50 of them are resting minutes. "Light exercise" is defined as: flex your knees for 4 minutes, rest 1 minute, repeat until 50 minutes has passed. Thus "Slow Motion Hokey Pokey". Now they are ready to open the airlock and step into space with no nasty attack of the bends.

The innovation was the 50 minutes of exercise. Without it, the entire protocol takes twelve hours instead of one hour and fifty minutes.

If the habitat module's pressure was 12 psi an astronaut could use an 8 psi space suit with no prebreathing required (a pity such suits are currently beyond the state of the art), and for a 4.5 psi suit the prebreathing time would be cut in half.

In case of emergency, when there is no time for prebreathing, NASA helpfully directs the astronauts to gulp aspirin, so they can work in spite of the agonizing pain.

Please note that most of the problem is due to the fact that soft space suits have a lower atmospheric pressure than the habitat module. So DCS can be avoided by using a hard space suit or space pod.


All of the atmospheric controls will be on the life support deck.

On a related note, forced ventilation in the spacecraft's lifesystem is not optional. In free fall, the warm exhaled carbon dioxide will not rise away from your face. It will just collect in a cloud around your head until you pass out or suffocate. In Arthur C. Clarke's ISLANDS IN THE SKY the apprentices play a practical joke on the main character using this fact and a common match. In the image above the blue dome shaped flame is an actual candle burning in free fall. And in Clarke's "Feathered Friend", he talks about the wisdom of using an animal sentinel to monitor atmospheric quality. Specifically by using the tried and true "canary in a coal mine" technique.

And yes, on Skylab, the area around the the air vent got pretty disgusting quite quickly, as all the floating food particles and assorted dirt from the entire space station got sucked in. In some SF novels the slang name for the air vents is "The Lost and Found Department."


They're wind chimes. I know most people like to tie little prayer flags and scarves and stuff to the air-vent to make sure it's working, but back home we use wind chimes. You don't have to be looking at 'em to know they're working.

They're not like the chimes they have back on Earth; these only have one note. Most habs around Saturn do it that way — each compartment has a single note. That way, you can tell location of a faulty blower just by the change in the sound. And let me tell you, they are not optional. If you take a set down for anything other than maintenance on the air-vent in question, you can get arrested.

Of course they're loud! That's how you know they're working. But I know what you mean — when I first moved out to Titan, it took me a good month to get used to 'em. I was up all night most nights hearing chimes all over the hab ringing. It was like this constant drone with a few off notes every now and then to make sure you didn't relax. I complained to anybody who'd listen, which was nobody. All I did was get myself a rep as another dumb groundhog fresh off the boat

The chimes didn't just bother me at night, either. They are everywhere. In public spaces they make quiet conversation just about impossible. And I just about failed my first semester in school from being distracted. I tried to use noise-canceling ear buds during study hall one time and almost got expelled for “negligence and reckless endangerment”. Seriously, if I hadn't still been under Immigrant's Probation, I would have had to do a public service sentence. I thought that was crazy — or some kind of bullsh*t hazing for the Earthworms or something. As it was, I did have to take the Habitat Orientation class again — listening to the damned wind chimes the whole time.

But let me tell you — They were absolutely right to bust me. They confiscated my ear buds when I got caught so I didn't have them during a weekend maintenance cycle on the hab. We were living in a retired Trans-Chronian, the kind they used to have before the River-class came out. The counter-spinning rings were always breaking down or getting fatigued or some damn thing, so we only had gravity maybe five days a week. My little sisters loved it — I'd play catch with them, with the toddler standing in as the ball. Anyway, the apartment had only pair of rooms, and my parents got one and the girls the other. I slept in a bag in the living room and lived out of a foot locker. One night I woke up from a dead sleep with the uncontrollable feeling that something was wrong. I couldn't put my finger out what it was, but the effect was disturbing. I figured that I was just having trouble sleeping from the wind chimes when I realized that was what was wrong — I wasn't hearing the chimes.

A glance up told me that the chimes in the living room were still going, but I really didn't need it. The sound of all the chimes in our apartment had gotten so far under my skin over the weeks we'd been living there that I pretty much figured out immediately which chimes had stopped. You guessed it — the girls' room. By the time I got in there they were both awake and holding hands while spinning like they teach you. My parents were in there a couple seconds after me, but only because they had farther to go.

Anyway, it was nothing much as vent problems go. A stuffed rabbit toy had gotten jammed into the fan — so the girls got grounded and had to do extra chores for a week. They whined about it, and kids do, and then we all went back to bed. It took a me good while to go back to sleep after that. For all I my complaining about those annoying, distracting, aggravating wind chimes, if we didn't have 'em up that night my sisters would have never have woken up. Ever again.

So, you don't mind me hanging these up, do you?


      There were also, I'd discovered, some interesting tricks and practical jokes that could be played in space. One of the best involved nothing more complicated than an ordinary match. We were in the classroom one afternoon when Norman suddenly turned to me and said: 'Do you know how to test the air to see if it's breathable?'
     'If it wasn't, I suppose you'd soon know,' I replied.
     'Not at all — you might be knocked out too quickly to do anything about it. But there's a simple test which has been used on Earth for ages, in mines and caves. You just carry a flame ahead of you, and if it goes out — well, you go out too, as quickly as you can!' He fumbled in his pocket and extracted a box of matches. I was mildly surprised to see something so old-fashioned aboard the Station.
     'In here, of course,' Norman continued, 'a flame will burn properly. But if the air were bad it would go out at once.' He absent-mindedly stroked the match on the box and it burst into light. A flame formed around the head — and I leaned forward to look at it closely. It was a very odd flame, not long and pointed but quite spherical. Even as I watched it dwindled and died.
     It's funny how the mind works, for up to that moment I'd been breathing perfectly comfortably, yet now I seemed to be suffocating. I looked at Norman, and said nervously: 'Try it again — there must be something wrong with the match.'
     Obediently he struck another, which expired as quickly as the first.
     'Let's get out of here,' I gasped. 'The air-purifier must have packed up.' Then I saw that the others were grinning at me.
     'Don't panic, Roy,' said Tim. 'There's a simple answer.' He grabbed the match-box from Norman. 'The air's perfectly O.K. but if you think about it, you'll see that it's impossible for a flame to burn out here. Since there's no gravity and everything stays put, the smoke doesn't rise and the flame just chokes itself. The only way it will keep burning is if you do this.'
     He struck another match, but instead of holding it still, kept it moving slowly through the air. It left a trail of smoke behind it, and kept on burning until only the stump was left.
     'It was entering fresh air all the time, so it didn't choke itself with burnt gases. And if you think this is just an amusing trick of no practical importance, you're wrong. It means we've got to keep the air in the Station on the move, otherwise we'd soon go the same way as that flame. Norman, will you switch on the ventilators again, now that you've had your little joke?'

From ISLANDS IN THE SKY by Sir Arthur C. Clarke (1954)
RocketCat sez

Yeah, Fireproof is another absolute classic from grand-master Hal Clement. And it hammers home a hard truth you can find in Lazarus Long's notebooks.

On Terra, being ignorant shortens your lifespan. Being willfully ignorant is just asking for it. And being willfully ignorant in space means you are doing your darnedest to cop a Darwin Award. You don't just need a good education to get a job in space, you need so you don't die.

Read how that moron saboteur Hart thinks education is a waste of time. Up to when his flaming body gets splattered all over the wall because he thinks he's so smart. He thinks Nah, I don't need no stinkin' physics and chemistry! That's the last thing that goes through his brain, besides the bulkhead.

If Igno-Spy had ever had a high-school Science 101 class he might have realized he was turning the inside of his jail cell into a freaking free-fall thermobaric weapon. With him flicking his Bic at the fuse like Wile E. Coyote.


(ed note: in this chipper little story every nation on Terra has at least one space station with a supply of nuclear bombs to keep everybody honest by virtue of Mutual Assured Destruction. Hart, a sinister agent of one of the evil Eastern nations, has been smuggled into one of the stations belonging to the virtuous Western Alliance. His mission is to sabotage the station. Unfortunately for him his knowledge of physics and free fall are sadly lacking. Also unfortunate is the fact that he is out-classed. The station crew was alerted to the agent's presence almost immediately, and they let him get cocky before capturing him.

The crew watch the agent's progress by closed-circuit TV, speculating on how the agent plans to destroy the station. There is a security team hiding nearby ready to seize the agent.)

      “A fire could be quite embarrassing, even if it weren’t an explosion,” pointed out his assistant, particularly since the whole joint is nearly pure magnesium. I know it’s sinfully expensive to transport mass away from Earth, but I wish they had built this place out of something a little less responsive to heat and oxygen.”
     “I shouldn’t worry about that,” replied Mayhew. “He won’t get a fire started.”

     Nearly half of the outer level was thus unified when (enemy agent) Hart reached a section of corridor bearing valve handles and hose connections instead of doors, and knew there must be liquids behind the walls. There were code indexes stenciled over the valves, which meant nothing to the spy; but he carefully manipulated one of the two handles to let a little fluid into the corridor, and sniffed at it cautiously through the gingerly cracked face plate of his helmet. He was satisfied with the results; the liquid was one of the low-volatility hydrocarbons used with liquid oxygen as a fuel to provide the moderate acceleration demanded by space launched torpedoes. They were, cheap, fairly dense, and their low vapor pressure simplified the storage problem in open-space stations.
     All that Hart really knew about it was that the stuff would burn as long as there was oxygen. Well—he grinned again at the thought—there would be oxygen for a while; until the compressed, blazing combustion gases blew the heat-softened metal of the outer wall into space. After that there would be none, except perhaps in the central core, where the heavy concentration of radioactive matter made it certain there would be no one to breathe it.
     At present, of course, the second level and any other intermediate ones were still sealed; but that could and would be remedied. In any case, the blast of the liberated fuel would probably take care of the. relatively flimsy inner walls. He did not at the time realize that these were of magnesium, or he would have felt even more sure of the results.
     He looked along the corridor. As far as the curvature of the outer shell permitted him to see, the valves projected from the wall at intervals of a few yards. Each valve had a small electric pump, designed to force air into the tank behind it to drive the liquid out by pressure, since there was no gravity. Hart did not consider this point at all; a brief test showed him that the liquid did flow when the valve was on, and that was enough for him. Hanging poised beside the first handle, he took an object from still another pocket of his spacesuit, and checked it carefully, finally clipping it to an outside belt where it could easily be reached.

     At the sight of this item of apparatus, Floyd almost suffered a stroke.
     “That’s an incendiary bomb !” he gasped aloud. “We can’t possibly take him in time to stop his setting it off—which he’ll do the instant he sees our men! And he already has free fuel in the corridor!”
     He was perfectly correct; the agent was proceeding from valve to valve in long glides, pausing at each just long enough to turn it full on and to scatter the balloon-like mass of escaping liquid with a sweep of his arm. Gobbets and droplets of the inflammable stuff sailed lazily hither and yon through the air in his wake.
     Mayhew calmly lighted a cigarette, unmindful of the weird appearance of the match flame driven toward his feet by the draft from the ceiling ventilators, and declined to move otherwise. “Decidedly, no physicist,” he murmured. “I suppose that’s just as well—it’s the military information the army likes anyway. They certainly wouldn’t have risked a researcher on this sort of job, so I never really did have a chance to get anything I wanted from him.”
     “But what are we going to do?” Floyd was almost frantic. “There’s enough available energy loose in that corridor now to blast the whole outer shell off—and gallons more coming every second. I know you’ve been here a lot longer than I, but unless you can tell me how you expect to keep him from lighting that stuff up. I’m getting into a suit right now!”
     “If it blows, a suit won’t help you,” pointed out the older man.
     “I know that!” almost screamed Floyd, “but what other chance is there? Why did you let him get so far?”
     “There is still no danger,” Mayhew said flatly, “whether you believe it or not. However, the fuel does cost money, and there’ll be some work recovering it, so I don’t see why he should be allowed to empty all the torpedo tanks. He’s excited enough now, anyway.” He turned languidly to the appropriate microphone and gave the word to the action squad. “Take him now. He seems to be without hand weapons, but don’t count on it. He certainly has at least one incendiary bomb.” As an afterthought, he reached for another switch, and made sure the ventilators in the outer level were not operating; then he relaxed again and gave his attention to the scanner that showed the agent’s activity. Floyd had switched to another pickup that covered a longer section of corridor, and the watchers saw the spacesuited attackers almost as soon as did Haft himself.

     The European reacted to the sight at once—too rapidly, in fact, for the shift in his attention caused him to miss his grasp on the valve handle he sought and flounder helplessly through the air until he reached the next. Once anchored, however, he acted as he had planned, ignoring with commendable self-control the four armored figures converging on him. A sharp twist turned the fuel valve full on, sending a stream of oil mushrooming into the corridor; his left hand flashed to his belt, seized the tiny cylinder he had snapped there, jammed its end hard against the adjacent wall, and tossed the bomb gently back down the corridor. In one way his lack of weightless experience betrayed him; he allowed for a gravity pull that was not there. The bomb, in consequence, struck the “ceiling” a few yards from his hand, and rebounded with a popping noise and a shower of sparks. It drifted on down the corridor toward the floating globules of hydrocarbon, and the glow of the sparks' was suddenly replaced by the eye-hurting radiance of thermite.
     Floyd winced at the sight, and expected the attacking men to make futile plunges after the blazing thing; but though all were within reach of walls, not one swerved from his course. Hart made no effort to escape or fight; he watched the course of the drifting bomb with satisfaction, and, like Floyd, expected in the next few seconds to be engulfed in a sea of flame that would remove the most powerful of the Western torpedo stations from his country’s path of conquest. Unlike Floyd, he was calm about it, even when the men seized him firmly and began removing equipment from his pockets. One unclamped and removed the face plate of his helmet; and even to that he made no resistance— just watched in triumph as his missile drifted toward the nearest globes of fuel.
     It did not actually strike the first. It did not have to; while the quantity of heat radiated by burning thermite is relatively small, the temperature of the reaction is notoriously high— and the temperature six inches from the bomb was well above the flash point of the rocket fuel, comparatively non-volatile as it was. Floyd saw the flash as its surface ignited, and closed his eyes.
     Mayhew gave him four or five seconds before speaking, judging that that was probably about all the suspense the younger man could stand.
     “All right, ostrich,” he finally said quietly. “I’m not an angel, in case you were wondering. Why not use your eyes, and the brain behind them?”
     Floyd was far too disturbed to take offense at the last remark, but he did cautiously follow Mayhew’s advice about looking. He found difficulty, however, in believing what his eyes and the scanner showed him.
     The group of five men was unchanged, except for the expression on the, captive’s now visible face. All were looking down the corridor toward the point where the bomb was still burning; Lang’s crew bore expressions of amusement on their faces, while Hart wore a look of utter disbelief. Floyd, seeing what he saw, shared the expression.
     The bomb had by now passed close to several of the floating spheres. Each had caught fire, as Floyd had seen—for a moment only. Now each was surrounded by a spherical, nearly opaque layer of some grayish substance that looked like a mixture of smoke and kerosene vapor; a layer that could not have been half an inch thick, as Floyd recalled the sizes of the original spheres. None was burning; each had effectively smothered itself out, and the young observer slowly realized just how and why as the bomb at last made a direct hit on a drop of fuel fully a foot in diameter.
     Like the others, the globe flamed momentarily, and went out; but this time the sphere that appeared and grew around it was lighter in color, and continued to grow for several seconds. Then there was a little, sputtering explosion, and a number of fragments of still burning thermite emerged from the surface of the sphere in several directions, traveled a few feet, and went out. All activity died down, except in the faces of Hart and Floyd.

     The saboteur was utterly at a loss, and seemed likely to remain that way; but in the watch room Floyd was already kicking himself mentally for his needless worry. Mayhew, watching the expression on his assistant’s face, chuckled quietly.
     “Of course you get it now,” he said at last.
     “I do now, certainly,” replied Floyd. “I should have seen it earlier—I’ve certainly noticed you light enough cigarettes, and watched the behavior of the match's flame. Apparently our friend is not yet enlightened, though,” he nodded toward the screen as he spoke.
     He was right; Hart was certainly not enlightened. He belonged to a service in which unpleasant surprises were neither unexpected nor unusual, but he had never in his life been so completely disorganized. The stuff looked like fuel; it smelled like fuel; it had even started to burn—but it refused to carry on with the process. Hart simply relaxed in the grip of the guards, and tried to find something in the situation to serve as an anchor for his whirling thoughts. A spaceman would have understood the situation without thinking, a high school student of reasonable intelligence could probably have worked the matter out in time; but Hart’s education had been that of a spy, in a country which considered general education a waste of time. He simply did not have the background to cope with his present environment.
     That, at least, was the idea Mayhew acquired after a careful questioning of the prisoner. Not much was learned about his intended mission, though there was little doubt about it under the circumstances. The presence of an alien agent aboard any of the free-floating torpedo launchers of the various national governments bore only one interpretation; and since the destruction of one such station would do little good to anyone, Mayhew at once radioed all other launchers to be on the alert for similar intruders—all others, regardless of nationality. Knowledge by Hart’s superiors of his capture might prevent their acting on the assumption that he had succeeded, which would inevitably lead to some highly regrettable incidents. Mayhew’s business was to prevent a war, not win one. Hart had not actually admitted the identity of his superiors, but his accent left the matter in little doubt; and since no action was intended, Mayhew did not need proof.
     There remained, of course, the problem of what to do with Hart. The structure had no ready-made prison, and it was unlikely that the Western government would indulge in the gesture of a special rocket to take the man off. Personal watch would be tedious, but it was unthinkable merely to deprive a man with the training Hart must have received of his equipment, and then assume he would not have to be watched every second.
     The solution, finally suggested by one of the guards, was a small storeroom in the outer shell. It had no locks, but there were welding torches in the machine shops. There was no ventilator either, but an alga tank would take care of that. After consideration, Mayhew decided that this was the best plan, and it was promptly put into effect.

     Hart was thoroughly searched, even his clothing being replaced as a precautionary measure. He asked for his cigarettes and lighter, with a half smile, Mayhew supplied the man with some of his own, and marked those of the spy for special investigation. Hart said nothing more after that, and was incarcerated without further ceremony. Mayhew was chuckling once more as the guards disappeared with their charge.
     “I hope he gets more good than I out of that lighter,” he remarked. “It’s a wick-type my kid sent me as a present, and the ventilator draft doesn’t usually keep it going. Maybe our friend will learn something, if he fools with it long enough. He has a pint of lighter fluid to experiment with—the kid had large ideas.”
     “I was a little surprised— I thought for a moment you were giving him a pocket flask,” laughed Floyd. “I suppose that’s why you always use matches—they’re easier to wave than that thing. I guess I save myself a lot of trouble not smoking at all. I suppose you have to put potassium nitrate in your cigarettes to keep ’em going when you’re not pulling on them.” Floyd ducked as he spoke, but Mayhew didn’t throw anything. Hart, of course, was out of hearing by this time, and would not have profited from the remark in any case.
     He probably, in fact, would not have paid much attention. He knew, of course, that the sciences of physics and chemistry are important; but bethought of them in connection with great laboratories and factories. The idea that knowledge of either could be of immediate use to anyone not a chemist or physicist would have been fantastic to him. While his current plans for escape were based largely on chemistry, the connection did not occur to him. The only link between those plans and Mayhew’s words or actions gave the spy some grim amusement; it was the fact that he did not smoke.
     The cell, when he finally reached it, was perfectly satisfactory; there were no peepholes which could serve as shot-holes, no way in which the door could be unsealed quickly—as Mayhew had said, not even a ventilator. Once he was in, Hart would not be interrupted without plenty of notice. Since the place was a storeroom, there was no reason to expect even a scanner, though, he told himself, there was no reason to assume there was none, either. He simply disregarded that possibility, and went to work the moment he heard the torch start to seal his door.
     His first idea did not get far. He spent half an hour trying to make Mayhew’s lighter work, without noticeable success. Each spin of the “flint” brought a satisfactory shower of sparks, and about every fourth or fifth try produced a faint “pop” and a flash of blue fire; but he was completely unable to make a flame last. He closed the cover at last, and for the first time made an honest effort to think. The situation had got beyond the scope of his training.
     He dismissed almost at once the matter of the rocket fuel that had not been ignited by his bomb. Evidently the Westerners stored it with some inhibiting chemical, probably as a precaution more against accident than sabotage. Such a chemical would have to be easily removable, but he had no means of knowing the method, and that line of attack would have to be abandoned.
     But why wouldn’t the lighter fuel burn? The more he thought the matter out, the more Hart felt that Mayhew must have doctored it deliberately, as a gesture of contempt. Such an act he could easily understand; and the thought of it roused again the wolfish hate that was such a prominent part of his personality. He would show that smart Westerner! There was certainly some way!
     Powerful hands, and a fingernail deliberately hardened long since to act as a passable screw-driver blade, had the lighter disassembled in the space of a few minutes. The parts were disappointingly small in number and variety; but Hart considered each at length.
     The fuel, already evaporating as it was, appeared useless—he was no chemist, and had satisfied himself the stuff was incombustible. The case was of magnalium, apparently, and might be useful as a heat source if it could be lighted; its use in a cigarette lighter did not encourage pursuit of that thought. The wick might be combustible, if thoroughly dried. The flint and wheel mechanism was promising—at least one part would be hard enough to cut or wear most metals, and the spring might be decidedly useful.
     Elsewhere in the room there was very little. The light was a gas tube, and, since the chamber had no opening whatever, would probably be most useful as a light. The alga tank, of course, had a minute motor and pump which forced air through its liquid, and an ingenious valve and trap system which recovered the air even in the present weightless situation; but Hart, considering the small size of the room, decided that any attempt to dismantle his only source of fresh air would have to be very much of a last resort.

     After much thought, and with a grimace of distaste, he took the tiny striker of the lighter and began slowly to abrade a circular area around the latch of the door, using the inside handle for anchorage.
     He did not, of course, have any expectation of final escape; he was not in the least worried about his chances of recovering his spacesuit. He expected only to get out of the cell and complete his mission; and if he succeeded, no possible armor would do him any good.
     As it happened, there was a scanner in his compartment; but Mayhew had long since grown tired of watching the spy try to ignite the lighter fuel, and had turned his attention elsewhere, so that Hart’s actions were unobserved for some time. The door metal was thin and not particularly hard; and he was able without interference and with no worse trouble than severe finger cramp to work out a hole large enough to show him another obstacle—instead of welding the door frame itself, his captors had placed a rectangular steel bar across the portal and fastened it at points well to each side of the frame, out of the prisoner’s reach. Hart stopped scraping as soon as he realized the extent of this barrier, and gave his mind to the new situation.
     He might, conceivably, work a large enough hole through the door to pass his body without actually opening the portal; but his fingers were already stiff and cramped from the use made of the tiny striker, and it was beyond reason to expect that he would be left alone long enough to accomplish any such feat. Presumably they intended to feed him occasionally.
     There was another reason for haste, as well, though he was forgetting it as his nose became accustomed to the taint in the air. The fluid, which he had permitted to escape while disassembling the lighter, was evaporating with fair speed, as it was far more volatile than the rocket fuel; and it was diffusing through the air of the little room. The alga tank removed only carbon dioxide, so that the air of the cell was acquiring an ever greater concentration of hydrocarbon molecules. Prolonged breathing of such vapors is far from healthy, as Hart well knew; and escape from the room was literally the only way to avoid breathing the stuff.
     What would eliminate a metal door—quickly? Brute force? He hadn’t enough of it. Chemicals? He had none. Heat? The thought was intriguing and discouraging at the same time, after his recent experience with heat sources. Still, even if liquid fuels would not burn perhaps other things would: there was the wicking from the lighter; a little floating cloud of metal particles around the scene of his work on the magnesium door; and the striking mechanism of the lighter. He plucked the wicking out of the air where it had been floating, and began to unravel it—without fuel, as he realized, it would need every advantage in catching the sparks of the striker.
     Then he wadded as much of the metallic dust as he could collect —which was not too much—into the wick, concentrating it heavily at one end and letting it thin out toward the more completely raveled part.
     Then he inspected the edges of the hole he had ground in the door, and with the striker roughened them even more on one side, so that a few more shavings of metal projected. To these he pressed the fuse, wedging it between the door and the steel bar just outside the hole, with the "lighting" end projecting into the room. He inspected the work carefully, nodded in satisfaction, and began to reassemble the striker mechanism.
     He did not, of course, expect that the steel bar would be melted or seriously weakened by an ounce or so of magnesium, but he did hope that the thin metal of the door itself would ignite.

     Hart had the spark mechanism almost ready when his attention was distracted abruptly. Since the hole had been made, a very gentle current of air had been set up in the cell by the corridor ventilators beyond—a current in the nature of an eddy which tended to carry loose objects quite close to the hole. One of the loose objects in the room was a sphere comprised of the remaining lighter fluid, which had not yet evaporated. When Hart noticed the shimmering globe, it was scarcely a foot from his fuse, and drifting steadily nearer.
     To him, that sphere of liquid was death to his plan; it would not burn itself, it probably would not let anything else burn either. If it touched and soaked his fuse, he would have to wait until it evaporated; and there might not be time for that. He released the striker with a curse, and swung his open hand at the drop, trying to drive it to one side. He succeeded only partly. It spattered on his hand, breaking up into scores of smaller drops, some of which moved obediently away, while others just drifted, and still others vanished in vapor. None drifted far; and the gentle current had them in control almost at once, and began to bear many of them back toward the hole—and Hart’s fuse.
     For just a moment the saboteur hung there in agonized indecision, and then his training reasserted itself. With another curse he snatched at the striker, made sure it was ready for action, and turned to the hole in the door. It was at this moment that Mayhew chose to take another look at his captive.
     As it happened, the lens of his scanner was so located that Hart’s body covered the hole in the door; and since the spy’s back was toward him, the watcher could not tell precisely what he was doing. The air of purposefulness about the captive was so outstanding and so impressive, however, that Mayhew was reaching for a microphone to order a direct check on the cell when Hart spun the striker wheel.
     Mayhew' could not, of course, see just what the man had done, but the consequences were plain enough. The saboteur’s body was flung away from the door and toward the scanner lens like a rag doll kicked by a mule. An orange blossom of flame outlined him for an instant; and in practically the same instant the screen went blank as a heavy shock wave shattered its pickup lens.
     Mayhew, accustomed as he was to weightless maneuvering, never in his life traveled so rapidly as he did then. Floyd and several other crewmen, who saw him on the way, tried to follow; but he outstripped them all, and when they reached the site of Hart’s prison Mayhew was hanging poised outside, staring at the door.
     There was no need of removing the welded bar. The thin metal of the door had been split and curled outward fantastically; an opening quite large enough for any man’s body yawned in it, though there was nothing more certain than the fact that Hart had not made use of this avenue of escape. His body was still in the cell, against the far wall; and even now the relatively strong, currents from the hall ventilators did not move it. Floyd had a pretty good idea of what held it there, and did not care to look closely. He might be right.

     Mayhew’s voice broke the prolonged silence.
     “He never did figure it out.”
     “Just what let go, anyway?” asked Floyd.
     "Well, the only combustible we know of in the cell was the lighter fluid. To blast like that, though, it must have been almost completely vaporized, and mixed with just the right amount of air—possible, I suppose, in a room like this. I don’t understand why he let it all out, though.”
     “He seems to have been using pieces of the lighter,” Floyd pointed out. “The loose fuel was probably just a by-product of his activities. He was even duller than I, though. It took me long enough to realize that a fire needs air to burn—and can’t set up convection currents to keep itself supplied with oxygen, when there is no gravity.
     “More accurately, when there is no weight,” interjected Mayhew. “We are well within Earth’s gravity field, but in free fall. Convection currents occur because the heated gas is lighter per unit volume than the rest, and rises. With no. weight, and no ‘up’ such currents are impossible.”
     “In any case, he must have decided we were fooling him with noncombustible liquids.”
     Mayhew replied slowly: “People are born and brought up in a steady gravity field, and come to take all its manifestations for granted. It’s extremely hard to foresee all the consequences which will arise when you dispense with it. I’ve been here for years, practically constantly, and still get caught sometimes when I’m tired or just waking up.”
     “They should have sent a spaceman to do this fellow’s job, I should think.”
     “How would he have entered the station? A man is either a spy of a spaceman—to be both would mean he was too old for action at all, I should say. Both professions demand years of rigorous training, since habits rather than knowledge are required—habits like the one of always stopping within reach of a wall or other massive object.”

From FIREPROOF by Hal Clement (1949)

The Avenger had long since disappeared and Tom was left alone in space in the tiny jet boat.

To conserve his oxygen supply, the curly-haired cadet had set the controls of his boat on a steady orbit around one of the larger asteroids and lay down quietly on the deck. One of the first lessons he had learned at Space Academy was, during an emergency in space when oxygen was low, to lie down and breath as slowly as possible.

And, if possible, to go to sleep. Sleep, under such conditions, served two purposes. While relaxed in sleep, the body used less oxygen and should help fail to arrive, the victim would slip into a suffocating unconsciousness, not knowing if and when death took the place of life.

From ON THE TRAIL OF SPACE PIRATES by Carey Rockwell (1953)
a Tom Corbett Space Cadet book


Unpleasant odors in the air is a problem, but there is not much one can do about it. After all, you can't just open up a window to let in some fresh air, not in the vacuum of space. NASA carefully screens all materials, sealants, foods, and everything else to ensure that they do not emit noticeable odor in the pressurized habitat sections of spacecraft and space stations. Such odors can quickly become overpowering in such tight quarters.


INTERVIEWER: I used to ride submarines for the Navy, and some of the experiences you describe reminded me of being locked away underwater. Occasionally I’m someplace where the right combination of smells—amine, diesel, farts—triggers a memory. Does the same thing happen to you?

ASTRONAUT SCOTT KELLY: I was touring the Harris County Jail, and there’s this room that smells like space station—combination of antiseptic, garbage, and body odor. You know how on Earth, with gravity, stuff tends to rise or fall depending on its weight compared to air? On the ISS, that doesn’t happen, so smells can kind of linger.


(ed note: the topic is old non-nuclear diesel-electric submarines)

OK…so why…you might ask…were they called "Pig Boats"?

Well sir…put between 70 and 100 men into a tube containing four huge diesel engines burning…what else…diesel fuel, God only knows how many other types of chemicals…and two(2) Fresh Water Distilling pieces of equiment that only worked some of the time.

Now…on the USS Piper SS409…we were lucky if one "Still" was working at any one time…and of course the distilled water that was produced was to be used for cooking, drinking and showers…but since only one still was functionin most of the time…what do you think the fresh water was used fer…NOT fer showers…that's fer sure.

Now sir…we then coup all those men up in this tube fer periods of time ranging frum one week to as long as five or six months…get'n the picture yet? If yur cruise was a Caribbean or Med cruise…on certain occasions the Skipper would stop the boat in the middle of the ocean or sea and have "Swim Call"…jump over the side and have a ball…as well as cleanin up a bit. This however was a mixed blessing…because although you got clean and refreshed…you were now covered with SALT…and no way to wash it off. Try sleeping on a hot night in a hot submarine with salt all over yur body mate…

OK…so not only do you have all the persperation odors of all those men…but all their other bodily odors…I think ya know what I mean. And then sometimes the Sanitary Tanks ( held all the sub's sewage for periods of time) would have problems with a sticking external valve needed to expell the sewage over-board…and you can only imagine the lovely aroma circulating throughout your environment…

So…put it all together and you have the life of a bubblehead on a "Guppy" fleet submarine in the 50's and 60's…and you now know why they were affectionately called "Pig Boats".


     A glossed over aspect of interstellar society is the difficulty of accommodating humans (let alone aliens) comfortably on the same ships. I'll just deal with humans for this post.

     Atmosphere is the first thing passengers will notice aboard a ship. Not being able to breathe trumps decor and cuisine. While passengers will be assured of a breathable mix, humidity, pressure, temperature and such will be for the crew (or captain's) norm and not theirs. This is because having your pilot or engineer become light headed at the wrong time may lead to inevitable and infinite delays in reaching your destination. Note that crew will usually forgo any atmospheric contaminants they grew up with (and acclimated to).

     Passengers could have atmospheres set to their comfort zone in their staterooms. In some extreme cases filter masks or compressors might be worn. Contaminants can still become an issue. Consider most free traders and subsidized merchants travel to a number of worlds. The ship and the crew are exposed to all manner of dusts, pollens and pollutants which they then carry onboard. Decorative foliage is usually not a feature on most ships for this reason. Some pollens will send some offworlders to the hospital. But crew will bring back these various ticking allergens back onboard in their hair and clothes. This dust will accumulate despite air filtration systems if the ship is not scrupulously cleaned and your average crew will already be working two jobs on a tramp freighter. They probably won't get the corners or under the fridge.

     Besides this consider that cargo is liable to bring allergens onboard or cause allergic reactions itself. Add to this gases emitted by plastics in a plethora of manufactured products from a multitude of worlds with different health codes written for variant humans with a variety of tolerances. You start to wonder how humans will survive their first trip without sneezing themselves to death.

     An allergic reaction from a passenger or new recruit is almost inevitable. Hopefuly your steward has done a good job researching the passenger's files, identifying common allergens for their human substype and testing for such contaminants before they ever set foot on deck. And you thought your steward was great because he made awesome grilled cheese sandwiches.

From SPECIAL ACCOMMODATIONS by Rob Garitta (2016)

There's a fortune awaiting the man who invents a really good deodorizer for a spaceship. That's the one thing you can't fail to notice.

Oh, they try, I grant them that. The air goes through precipitators each time it is cycled; it is washed, it is perfumed, a precise fraction of ozone is added, and the new oxygen that is put in after the carbon dioxide is distilled out is as pure as a baby's mind; it has to be, for it is newly released as a by-product of the photosynthesis of living plants. That air is so pure that it really ought to be voted a medal by the Society for the Suppression of Evil Thoughts.

Besides that, a simply amazing amount of the crew's time is put into cleaning, polishing, washing, sterilizing - oh, they try!

But nevertheless, even a new, extra-fare luxury liner like the Tricorn simply reeks of human sweat and ancient sin, with undefinable overtones of organic decay and unfortunate accidents and matters best forgotten. Once I was with Daddy when a Martian tomb was being unsealed - and I found out why xenoarchaeologists always have gas masks handy. But a spaceship smells even worse than that tomb.

It does no good to complain to the purser. He'll listen with professional sympathy and send a crewman around to spray your stateroom with something which (I suspect) merely deadens your nose for a while. But his sympathy is not real, because the poor man simply cannot smell anything wrong himself. He has lived in ships for years; it is literally impossible for him to smell the unmistakable reek of a ship that has been lived in - and, besides, he knows that the air is pure; the ship's instruments show it. None of the professional spacers can smell it.

But the purser and all of them are quite used to having passengers complain about the "unbearable stench" - so they pretend sympathy and go through the motions of correcting the matter.

Not that I complained. I was looking forward to having this ship eating out of my hand, and you don't accomplish that sort of coup by becoming known first thing as a complainer. But other first-timers did, and I certainly understood why - in fact I began to have a glimmer of a doubt about my ambitions to become skipper of an explorer ship.

But - Well, in about two days it seemed to me that they had managed to clean up the ship quite a bit, and shortly thereafter I stopped thinking about it. I began to understand why the ship's crew can't smell the things the passengers complain about. Their nervous systems simply cancel out the old familiar stinks - like a cybernetic skywatch canceling out and ignoring any object whose predicted orbit has previously been programmed into the machine.

But the odor is still there. I suspect that it sinks right into polished metal and can never be removed, short of scrapping the ship and melting it down. Thank goodness the human nervous system is endlessly adaptable.

From PODKAYNE OF MARS by Robert Heinlein

(ed note: US captain John Fitzthomas and Chinese captain June Tran are talking)

     (June Tran said) "Take all the politicians, and draft them into the space navies. Make them spend a year cooped up on a spaceship. Don't let them out. Don't even let them go to astrogation and look through the telescope at the stars. Just them and the metal on all sides of them. Food that tastes like plastic. Air that smells like sweat and farts."
     "I know, I know. I'm sorry. It's just, well, we don't have the last problem anymore."

     "No. I want to see the lake. I have heard all their stories anyway. And you haven't told me the secret of how you keep your spaceship from stinking."
     "Oh, it's not a secret. We have a Gadget. It's standard issue."
     "A Gadget?"
     "Yes. Tell me you've never heard of a Gadget."
     "I'm afraid I have not."
     "It's wonderful. It's a little machine you place right at the out vent of your gas exchanger, right where the oxygenated air gets pumped back into the ventilation system. It has some kind of filter that neutralizes all the smells that usually build up; it learns what your ship smells like so it can clean the air more efficiently. Then it perfumes the outgoing air with whatever you want."
     "You're kidding."
     "I'm not kidding at all. It's a godsend. The guy who invented it was this California nisei named Takumi Maeda. He made a fortune selling them. He has a company now that makes all kinds of stuff."
     "I have never heard of this man or his miraculous invention."
     "You mean to tell me you've never heard of International Gadgets?"
     "We don't see many American products in Oz."
     "Apparently not, because you don't have a Gadget."
     "What does yours smell like?"
     "Cinnamon rolls now. The crew votes every week on a new one so we don't get tired of any one smell. Last week it was baby powder."
     Tran laughed and clapped her hands together. "I shall inform my superiors of this miracle invention. Perhaps an exception to the embargo can be found."
     "Maybe they'd be more willing to listen if you had a demo model."
     "Where would I get one of those?"
     "I have two spares. I could loan you one in the name of international peace and understanding."
     "That would be wonderful, John. Assuming, of course, it actually works as advertised."
     "It will. It comes with adapters for different vents, too, so it should fit yours fine even if you don't use the same size we do."

From THE LAST GREAT WAR by Matthew Lineberger (not yet published)

His hole was on the eighth level, off a residential tunnel a hundred meters wide with fifty meters of carefully cultivated green park running down the center. The main corridor's vaulted ceiling was lit by recessed lights and painted a blue that Havelock assured him matched the Earth's summer sky. Living on the surface of a planet, mass sucking at every bone and muscle, and nothing but gravity to keep your air close, seemed like a fast path to crazy. The blue was nice, though.

Some people followed Captain Shaddid's lead by perfuming their air. Not always with coffee and cinnamon scents, of course. Havelock's hole smelled of baking bread. Others opted for floral scents or semipheromones. Candace, Miller's ex-wife, had preferred something called EarthLily, which had always made him think of the waste recycling levels. These days, he left it at the vaguely astringent smell of the station itself. Recycled air that had passed through a million lungs. Water from the tap so clean it could be used for lab work, but it had been p**s and sh*t and tears and blood and would be again. The circle of life on Ceres was so small you could see the curve. He liked it that way.

From LEVIATHAN WAKES by "James S.A. Corey" (Daniel Abraham and Ty Franck) 2011.
First novel of The Expanse

Atmospheric Contaminants

Infinitely more serious than annoying odors are harmful atmospheric contaminants. They share the same problem that a spacecraft cannot open the windows to bring in some fresh air. But unlike odors, these can harm or kill.

Basic atmospheric monitors will keep an eye on the breathing mix inside the habitat module for oxygen and carbon dioxide levels. But prudent spacecraft will have monitors for carbon monoxide, fire smoke, and other deadly gases hooked up to strident alarms.


(ed note: Walter Curnow and Max Brailovsky enter the derelict spacecraft Discovery)

      (Max Brailovsky thought)Even his familiar spacesuit felt wrong, now that there was pressure outside as well as in. All the forces acting on its joints were subtly altered, and he could no longer judge his movements accurately. I'm a beginner, starting my training all over again, he told himself angrily. Time to break the mood by some decisive action.
     'Walter — I'd like to test the atmosphere.'
     'Pressure's okay; temperature — phew — it's one hundred five below zero.'
     'A nice bracing Russian winter. Anyway, the air in my suit will keep out the worst of the cold.'
     'Well, go ahead. But let me shine my light on your face, so I can see if you start to turn blue. And keep talking.'
     Brailovsky unsealed his visor and swung the faceplate upward. He flinched momentarily as icy fingers seemed to caress his cheeks, then took a cautious sniff, followed by a deeper breath.
     'Chilly — but my lungs aren't freezing. There's a funny smell, though. Stale, rotten — as if something's — oh no!'

     Looking suddenly pale, Brailovsky quickly snapped the faceplate shut.
     'What's the trouble, Max?' Curnow asked with sudden and now perfectly genuine anxiety. Brailovsky did not reply; he looked as if he was still trying to regain control of himself. Indeed, he seemed in real danger of that always horrible and sometimes fatal disaster — vomiting in a spacesuit.
          There was a long silence; then Curnow said reassuringly: 'I get it. But I'm sure you're wrong. We know that Poole was lost in space. Bowman reported that he… ejected the others after they died in hibernation — and we can be sure that he did. There can't be anyone here. Besides, it's so cold.' He almost added 'like a morgue' but checked himself in time.
     'But' suppose,' whispered Brailovsky, 'just suppose Bowman managed to get back to the ship — and died here.'

     There was an even longer silence before Curnow deliberately and slowly opened his own faceplate. He winced as the freezing air bit into his lungs, then wrinkled his nose in disgust.
     'I see what you mean. But you're letting your imagination run away with you. I'll bet you ten to one that smell comes from the galley. Probably some meat went bad, before the ship froze up. And Bowman must have been too busy to be a good housekeeper. I've known bachelor apartments that smelled as bad as this.'
     'Maybe you're right. I hope you are.'
     'Of course I am. And even if I'm not — dammit, what difference does it make? We've got a job to do, Max. If Dave Bowman's still here, that's not our department — is it, Katerina?'

     There was no reply from the Surgeon-Commander; they had gone too far inside the ship for radio to penetrate. They were indeed on their own, but Max's spirits were rapidly reviving. It was a privilege, he decided, to work with Walter. The American engineer sometimes appeared soft and easygoing. But he was totally competent — and, when necessary, as hard as nails.
     Together, they would bring Discovery back to life; and, perhaps, back to Earth.

     'Hello, Leonov,' said Curnow at last. 'Sorry to keep you waiting, but we've been rather busy.
     'Here's a quick assessment, judging from what we've seen so far. The ship's in much better shape than I feared. Hull's intact, leakage negligible — air pressure eighty-five per cent nominal. Quite breathable, but we'll have to do a major recycling job because it stinks to high heaven.

     Once power had been restored, the next problem was the air; even the most thorough housecleaning operations had failed to remove the stink. Curnow had been right in identifying its source as food spoiled when refrigeration had failed; he also claimed, with mock seriousness, that it was quite romantic. 'I've only got to close my eyes,' he asserted, 'and I feel I'm back on an old-time whaling ship. Can you imagine what the Pequod must have smelled like?'
     It was unanimously agreed that, after a visit to Discovery, very little effort of the imagination was required. The problem was finally solved — or at least reduced to manageable proportions — by dumping the ship's atmosphere. Fortunately, there was still enough air in the reserve tanks to replace it.

From 2010 ODYSSEY TWO by Arthur C. Clarke (1982)

(ed note: The crew of the good ship Tinker are sent to investigate a derelict tramp cargo starship. Apparently the tramp ship had been desperately cutting corners for too long. The results were horrifying. )

      (First Officer Wang said) “Salvage party now on the hangar deck, Captain. We are commencing our sweep.”
     (Captain Fredi back on the Tinker said) “Carry on, Mr. Wang.”

     What followed was a nightmare. We found the crew. Most of them were where one might expect to find crew. Or at least where they’d have fallen. After the first few swollen corpses, we learned not to look too closely. There was nothing we could do for them. Even cleanup needed to wait until the forensics team arrived.
     In the meantime, we did what we could to regain stability in the ship. It was a challenge. The ship looked like it hadn’t been cleaned in a stanyer (standard year). The watch standing consoles were smeared with dirt and grease in the engineering spaces. There were empty and near empty coffee cups, mess trays, and more odd bits of cloth and clothing than I had ever seen aboard a ship.
     We used standby consoles and the emergency bridge connections in Engineering to stabilize the ship and begin a preliminary investigation. We needed to know what killed them before we could take off our suits and the clock was ticking. I led Mr. Udan and Mr. Belnus forward to survey the bridge while Ms. Strauss and Mr. Marks started up the extra consoles in engineering and began looking at the ship’s physical status.

     The trip through the spine was difficult. I tried not to look too closely at what I had to walk around on the way Hanging wires, broken ductwork, and the swollen body I had to step over didn’t make it easy to ignore my surroundings.
     When we got to the bridge, I fired up an extra console at the forward end. We used that to establish a control link to engineering. It gave us a look at ship’s status and provided access to the logs and autopilot. In a matter of half a dozen ticks, automated station keeping jets damped down the bobbing and yawing so we didn’t have to worry quite as much about losing balance and falling on or in something unfortunate.
     I sent Mr. Belnus to survey below decks and put Mr. Udan on bridge watch. While we were on ballistic trajectory–and while a corpse occupied the helm–there wasn’t much we could do except keep an eye open.

     Ms. Strauss called on the working channel. “I think I found it, Mr. Wang. Scroll back in the gas mixture logs, sar.” ("sar" is the gender-neutral version of "sir")
     I pulled up the environmental logs and started scrolling back. The levels of methane and other gaseous by products of decomposing bodies showed clearly but I scrolled back almost to the point where the ship had gotten underway.
     I saw the reading on the screen but I couldn’t believe it. “Carbon monoxide?
     “That’s what it looks like, sar. It’s gone now, but it’s in the record.”
     I traced back more and followed the history forward. Shortly after getting underway, carbon monoxide spiked in the ship’s atmosphere. The levels were in the fatal range and the physical evidence around us reinforced the record.
     “Why didn’t any of the alarms go off, sar?”
     My fingers tapped the keys awkwardly in the heavy gloves but I persevered and brought up the alarm status. They were all red. “Sar? The environmental alarms are all shut off.”
     “I see that, Ms. Strauss.”
     Mr. Udan watched over my shoulder and saw the list. “How is that even possible, sar?”
     “I don’t know, Mr. Udan. It’s like the sensor control unit is gone. The sensors are there. The system is recording, but the alarm circuits are not active." I thought about it for half a tick. “That’s a general systems module. See if you can find what caused the spike in carbon monoxide, Ms. Strauss. I’ll go check the systems closet.”
     “Aye, aye, sar.” Her voice sounded distracted over the radio. “Maybe I can find the lead sensor in the data stream.”
     The data closet on Barbells was tucked under the bridge ladder. I left Mr. Udan on lookout and made my way down. It was the twin to the one on the Tinker and it took me only a moment to find the correct cabinet. When I pulled out the drawer, the gap in components was obvious. The slot that should have held the subsystem for managing alarm routings was empty. In its place was the red maintenance card required whenever a component was pulled for maintenance. Scrawled on the face was a date–July 21, 2371–and some initials. They’d been flying without alarms for almost two months. The sensors all worked. The systems recorded the readings, but when the readings reached critical stages, the interface that should trigger the ship’s alarm system wasn’t there to respond to the signal.
     It was an appalling breach of safety protocols.

     On a hunch I went down the passage to the spares closet and pulled open the door. It wasn’t completely empty, but very nearly so. On the Tinker we had a spare for every single component in the data closet, along with some spare racks and odd bits. I had never tried to do it, but when I’d been systems officer, I’d made sure we had all the parts we needed to rebuild the closet from the bulkheads out in case of emergency.
     The nearly empty closet in front of me was frightening.

     I opened the general communications channel and called to Ms. Strauss. “Find the source yet, Ms. Strauss?”
     “Yes, sar. A smoldering burn in a pile of castoffs in a corner of the engine room. Looks like an electrical spark from a broken lamp. The timing is consistent with kicker burn on their push out of Breakall.”
     “Check the fire detection systems, please?”
     “Doing it now, sar.” There was a pause. “Yes, they detected the smoke, but the heat signature was below threshold.”
     “Any indication of how long it burned, Ms. Strauss?”
     “Looks like about three days, sar. Fire system reset then and that’s consistent with the peak carbon monoxide readings.” There was another pause. “Their systems detected it. Why didn’t they respond?”
     “There were no alarms.”
     “Yes, sar, but the watch standers should have seen the readings.”
     “Which watch standers, Ms. Strauss?”
     “Environmental and engineering both registered it on the logs, sar.”
     “How long between the time the fire started and the carbon monoxide reached critical levels, Ms. Strauss?”
     I waited for her to check the logs. “Looks like about eight or nine stans (standard hours), sar.”
     “Check the watch logs. They had to have had a change in duty during that time. Did they note anything?” I headed up to the bridge and crossed to where Mr. Udan had the extra console running. He had heard the exchange on the working channel, of course, and stepped back so I could access the terminal.
     “Looks like the first signs showed up just before they secured from navigation stations, sar. The readings were elevated but there’s no note in the logs.”
     I scrolled back in the OD logs and found the bridge records. “None up here, either, Ms. Strauss. Was there anything at the watch change?” I scrolled forward and saw only routine entries.
     “Found it, sar. ‘Elevated CO noted. Sensors flagged for malfunction.’”
     I shook my head to myself. “There’s nothing in the bridge logs. If they notified the bridge, it didn’t get noted.”
     The circuit got quiet. I don’t know what the others were thinking but I was imagining what must have followed. Around the ship, crew would have started falling into a final sleep as the carbon-monoxide gas built up in their bodies. Some of them probably had headaches. They might have noticed some blurry vision. Given the number of people we’d found in their bunks, only the few watch standers might have been in a position to make a difference. Environmental and Engineering watch standers would have been the first to succumb as the heavy gas pooled in the stern nacelle. It wouldn’t have taken long for the environmental systems to pump the forward section full of deadly gas as well. I wondered if the body in the ship’s spine might have been the messenger sent aft to find out why nobody back there was responding.
     I shook off the images and fired up the command circuit. I needed to let (captain) Fredi know what I’d found. I stood at the front of the bridge facing forward.
     The coldness of the Deep Dark seemed clean.

     The forensics team asked us to chill the ship down to just above freezing to “help preserve the evidence.” Enough time had elapsed that the "evidence" was pretty far beyond “preserving” so we lived in our suits when aboard. We also used the thrusters to turn the ship. While we were still on a ballistic trajectory, the course curved inward and toward the investigative team racing out to meet us.
     Four days after turning the ship, we rendezvoused. Their ship was a fast packet in the twenty metric kiloton range and they boarded by the simple expedient of docking with us nose-to-nose. That allowed us to use the main locks on both ships and walk between them. I was at the brow to meet the team when we cycled the locks. Both ships had breathable air, but we didn’t want to contaminate theirs with what we knew ours must smell like.
     When the lock opened a team of six professional looking individuals wearing black softsuits stepped out. The suits had the Confederated Planets logo on the breast and the letters TIC across the back.
     I was impressed. The Trade Investigation Commission was the big dog in the enforcement arm. More often than not it was the TIC that sent in the marines. They looked like salvation to me. These folks did not mess about, brooked no hanky-panky, and knew their business–and everybody else’s–inside and out.

     The leader of the TIC Team waited patiently for me to track onto his face. “You are Acting-Captain Ishmael Wang?”
     “I am.”
     “I’m Field Agent James Waters representing the CPJCT Investigatory Commission. We request permission to come aboard to offer aid and assistance to you and your crew under the terms of the Emergency Relief Clause of Title Twelve and also to begin securing available evidence pursuant to our investigation of the death of the crew. We further stipulate that we recognize that you and your crew are operating in good faith to safeguard the vessel and that evidence to the best of your abilities–pending any evidence to the contrary which we may uncover–and that you have successfully consummated a claim of salvage against this vessel, its cargo, and relevant appurtenances pending adjudication by the appropriate legal authorities.”
     Obviously this guy practiced the speech. I couldn’t imagine that he did it often enough that he’d be able to just rattle it off like that.
     “Permission granted, Agent Waters. Welcome aboard and I’m glad to have you.”
     “Thank you, Mr. Wang. We’ll begin with a survey of the ship, dump out the computer data cores, and begin retrieval of the remains. This is likely to be uncomfortable and unpleasant. If you’d like to send your people over to the Pertwee, you’re welcome to use our facilities.”
     “Thanks. We’ve been shuttling crew between here and the Tinker, but it’s still been a long and trying few days.”
     He nodded before giving a hand signal and the whole, black-suited lot of them tromped into the ship.

     It took them a surprisingly short time to clean up the bodies. One of the Pertwee’s holds was turned into a morgue and their team included two coroners. Within a day, they’d removed the bodies, copied the computer cores, taken photographs of much of the ship, and even cleaned up a lot of the more unfortunate by-products. We all gave depositions about what we’d found and walked a team of examiners through our boarding process–explaining what we’d touched, where we’d looked, and what we’d found.
     When it was over Agent Waters invited me to the Pertwee and we shared a cup of coffee on their mess deck. It felt good to peel back the softsuit a bit and breath real air. I’d had a few hours out of the suit back on the Tinker over the previous couple of days but I was feeling a bit worse for wear and had some ‘suit chafe’ in places it didn’t bear to think too long about.
     “You’ve done well, Mr. Wang. Are you going to be able to take the ship in from here?”
     “I think so. The Tinker has a crate of spares for us. We know what mistakes the previous crew made. We won’t be making them.”
     “We cleaned up what we could, but that’s not going to be a pleasant ship to ride in,” he said with a rueful smile.
     I sighed. “Yes, I’m sure. Is there anything you need us to safeguard?”
     He shook his head. “We took samples and swabs of everything. This really looks like a simple case of carelessness. Everything on this ship is held together with baling wire and spit. Even their food stores are barely up to regulation. There's no sign of foul play beyond their own negligence.
     “We noted that, too. There’s plenty to get the few of us back to Breakall, but I wouldn’t have wanted to be heading out into the Deep Dark with so little food.
     Agent Waters snorted.“Or spares, or tankage, or anything else.”
     “Were they that broke?” I asked.
     He shrugged. “If I knew, I wouldn’t be able to tell you, but it looks like a shoestring operation that just ran out of string.

     We sat there for a moment and then he stood. “Well, Mr. Wang, I’ll let you get back to your ship. I need to follow up with the investigative staff.” He grimaced. “If it’s any consolation to you, I’ll be filling out reports all the way back.”
     I grinned and stood up myself. “I’d almost be willing to trade you, Agent Waters. This is going to be a long three weeks.”
     I pulled my suit back around me and buttoned it up.
     Agent Waters looked at me strangely. “The air is breathable in there.
     “Yes, but we’re going to change out the air and reload it to try to purge some of the smell.”
     “Good luck with that. It’ll help some, and I’d recommend you keep the ambient temperature way down. It’ll help control the smell.

     I nodded my thanks and headed back to the locks. It took only a couple of ticks to cycle through to the Chernyakova. We released the latches and the Pertwee used her maneuvering thrusters to pull back and fall off to starboard. We set about clearing as much of the smell as we could.
     Fredi sent over a replacement circuit board so we were able to get alarms back online. With just the five of us as a skeleton crew, we were going to be relying on automated systems a good deal. We vented the tainted air and refilled the ship with a clean mixture that was clear of methane and the other gaseous byproducts of decomposition. We used the depressurization process to test the alarm circuits. They triggered correctly when the hull pressure dropped. They also put up a proximity alarm because we were sailing so close to the Tinker.
     I was on the bridge with Mr. Belnus and Mr. Marks when the hull pressure stabilized. We looked at each other, nobody wanting to be the first to take off the helmet and breath ship’s air. As ranking officer, I did the only thing I could do and pulled the seal on my suit. The cold ship air rushed in carrying a whiffy carrion odor that I won’t try to describe. It wasn’t enough to make me retch, but I had to swallow a couple of times.
     Mr. Belnus and Mr. Marks followed my lead. They both made faces but kept control.
     “Let’s get some cleaning gear up here and scrub down the bridge with something strong and chemical smelling, gentlemen.” I blinked my eyes against the odor. “And maybe we should do that first.”
     Mr. Belnus headed for the cleaning locker below decks and returned shortly with sponges and buckets of hot water with a resinous smelling soap so strong that it pinched the lining of my nose. We all leaned close to the buckets and took lungs full of the moist air. It helped a little. After a fast hour’s washdown of the bridge, the smell wasn’t entirely gone, but the resin soap gave it a run for its money.
     I left the deck ratings to finish putting away the cleaning gear, and made my way aft to check on engineering. By the time I got there, the odor didn’t bother me so much. Perhaps the proximity to the scrubbers made a difference, or perhaps my nose got numbed to the stimulation.

     I found Strauss and Marks working in the engineroom.
     “This place is filthy, sar.”
     I looked around and had to agree. “The bridge was a little better but obviously they didn’t place much value in cleanliness, Ms. Strauss.”
     Mr. Marks sighed. “It was worth their lives, sar. Too bad they valued that so little.”
     That was a sobering thought. Like we needed any more somber thoughts. He had the right of it. If the pile of rubbish hadn’t been there, it couldn’t have caught fire. Of course, if they hadn’t shorted themselves on the spares, the ship would have alerted them to their danger.


In space no one can hear you scream, but in the habitat module's atmosphere everybody can hear that high-pitched squeaky wheel in the ventilator. And there may be permanent hearing loss from loud noises, say, from rocket engines.

But you will get used to the wind chimes.

As a point of reference, the normal ambient noise level on the International Space Station is 60 db.



     Acoustic criteria are specified in terms of A-weighted sound level (LA) or equivalent A-weighted sound level (Leq), where it is a specified time period, usually 8 or 24 hours. The equivalent A-weighted sound level is defined as the constant sound level that, in a given situation and time period, conveys the same sound energy as the actual time varying A-weighted sound. The basic unit for these measurements is the decibel.


     1. Space station laboratory modules should have A-weighted sound levels not exceeding 55 dB (a noise criterion curve of approximately 50) and reverberation times not exceeding 1.0 s. These values should permit 95 percent intelligibility for sentences under conditions of normal vocal effort with the talker and the listener visible to each other. Communication performance could be lower in the absence of visual cues or with artificial or synthesized speech or with the use of “squawk boxes.”

     2. Environments with A-weighted sound levels above 55 dB will require assistance for adequate speech communication. Designers of audiecommunication systems should recognize that the systems will amplify and distribute noise as well as speech signals to both intended and unintended listeners. Therefore, their use should be carefully controlled.


     1. Sleep disturbance due to noise depends on the physical characteristics of the noise, its meaning, and the affected persons’ stage of sleep, as well as their motivation, gender, and age.

     2. For sleeping areas, background A-weighted sound levels below 45 dB are preferred, while levels up to 60 dB(A) are acceptable.

     3. Brief noises or transients during continuous noise backgrounds are particularly disturbing to sleep. The probability of full behavioral awakening increases with increasing sound level of the transient. For transients with an LA of 60 dB, the probability of full behavioral awakening is about 0.2, while for a level of 75 dB, the probability increases to approximately 0.3.


     1. The risk for producing significant hearing loss is negligible in noise exposures to an Leq24 of 80 dB.

     2. A hearing conservation program similar to that described by the Occupational Safety and Health Administration should be initiated for exposures to an Leq8 of 85 dB or more.


     If acoustic requirements for acceptable speech communication, sleep, and hearing conservation are met, problems of annoyance and task disruption will be minimal.


     Vibration criteria are specified for linear vibration in the 1-100 Hz frequency range.


     1. Vibration criteria for acceptable long-term habitability should fall in the range of 1 to 5 × 10-2m/sec2 rms acceleration for the frequencies between 1 and 8 Hz and follow a constant velocity function from 8 to 100 Hz.

     2. Below 0.5 Hz, motion sickness symptoms must be considered, although individual susceptibility, several environmental factors, and the weightless condition make the establishing of general criteria difficult. To reduce the probability of motion sickness, it is recommended that acceleration not exceed 2.5 × 10-2m/sec2 at 0.2 Hz.


     1. Specific tasks requiring more stringent vibrational criteria should be analyzed on an individual basis. In the absence of appropriate information, these tasks should be simulated on earth to determine vibration sensitivity and required accuracy.

     2. If head or finger control is required to an accuracy of 5mm rms or 2.5 Newtons rms, the weighted acceleration magnitude in any axis should not exceed 5 × 10-3m/sec2 rms.

     3. For visual tasks that require observation of details that subtend less than 2 minutes of arc at the eye, the weighted acceleration magnitude should not exceed 5 × 10-3m/sec2 rms with a doubling of vibration magnitude for every √2 increase in the size of the detail.


“Space may be silent, but it’s easy to tell how the ship’s maneuvering from the noise inside. Cold-gas thrusters hiss. Hypergolics hiss too, with a harsher metallic note, bangs and pings. Hydroxy rockets, they roar. Solid packs are similar, but rougher, with underlying stutters and clicks. Fusion torches purr like giant cats – unless they’re Nucleodyne-made and running at hard burn1, when the afterburner resonance mode makes ’em howl like damned souls. Mass-driver launch is eerily silent, nothing but air whispering over the hull until the lasers cut in, and then it’s endlessly rolling thunder, dwindling behind you.”

Nuclear pulse-drive? You don’t hear a pulse-drive, not with your ears and live t’talk about it. You hear it with your bones.”

1. Hard burn, in the jargon, refers to the practice of injecting (a limited supply of) antiprotons into the exhaust of a fusion torch for short, high-power bursts.


Six years after launch, the International Space Station’s living quarters are still noisier than they should be. Now Russian news reports say that astronaut Bill McArthur and cosmonaut Valery Tokarev returned from their six-month stay aboard the ISS in April 2006 with some hearing loss.

NASA will not discuss the health of individual astronauts, but spokesperson Kylie Clem told New Scientist: “It’s not an impedance to operations or crew health or safety. It’s more of a comfort level issue.”

Former astronaut Jay Buckey, now at Dartmouth Medical School in Hanover, New Hampshire, US, says that both temporary and permanent hearing loss were recorded after flights on the Soviet and Russian Salyut and Mir stations, even for stays as short as seven days. The lost hearing was usually at higher frequencies.

The living quarters of the ISS are the Russian Zvezda module, which is the noisiest module on the station. NASA says the goal is for the working area to have noise levels at or below 60 decibels (dB) and sleep bunks to be 50dB. At their peak several years ago, noise levels reached 72 to 78dB in the working area and 65 dB in the sleep stations. Decibels are measured on a logarithmic scale, meaning, for example, that 60dB is 10 times louder than 50dB.

NASA has worked to reduce the noise and its effect on the crew. By November 2005, noise levels had been lowered to between 62 to 69dB in the work area and 55 to 60dB in the sleep compartments. Astronauts on the ISS used to have to wear ear plugs all day but are now only wear them for 2 to 3 hours per work day.

Intracranial pressure

According to the US National Institutes of Health, however, noise levels below 80dB are unlikely to lead to hearing loss, even with prolonged exposure.

But while the primary cause of hearing loss in general is high noise levels, Buckey suggested in a 2001 paper in Aviation Space and Environmental Medicine that several other factors might contribute to the problem in space.

Elevated intracranial pressure, higher carbon dioxide levels and atmospheric contaminants may make the inner ear more sensitive to noise, he says. But there have been no studies yet to test these ideas.

Buckey had designed a device to measure hearing loss of astronauts on the ISS, but his project was cancelled around the start of 2006 when NASA reduced funding for life sciences.

NASA has already done much of what it can to reduce noise on the ISS. Crews have installed fan vibration isolators and mufflers on fan outlets, and acoustic padding to wall panels.

The current crew, Russian cosmonaut Pavel Vinogradov and US astronaut Jeff Williams, installed a sound-insulating cover on the Russian carbon dioxide removal system. They also started adding acoustic padding near the Russian air conditioner. Future crews will swap out 30 to 40 fans with quieter versions.

Meteor Punctures

Meteors are probably nothing to worry about. On average a spacecraft will have to wait for a couple of million years to be hit by a meteor larger than a grain of sand (unless you are in low orbit around a planet with too many satellites). But if you insist, there are a couple of precautions one can take.

Whipple Shield

First one can sheath the ship in a thin shell with a few inches of separation from the hull. This "meteor bumper" (aka "Whipple shield") will vaporize the smaller guys.


      31 August 2016 ESA engineers have discovered that a solar panel on the Copernicus Sentinel-1A satellite was hit by a millimetre-size particle in orbit on 23 August. Thanks to onboard cameras, ground controllers were able to identify the affected area. So far, there has been no effect on the satellite’s routine operations.
     A sudden small power reduction was observed in a solar array of Sentinel-1A, orbiting at 700 km altitude, at 17:07 GMT on 23 August. Slight changes in the orientation and the orbit of the satellite were also measured at the same time.
     Following a preliminary investigation, the operations team at ESA’s control centre in Darmstadt, Germany suspected a possible impact by space debris or micrometeoroid on the solar wing.
     Detailed analyses of the satellite’s status were performed to understand the cause of this power loss. In addition, the engineers decided to activate the board cameras to acquire pictures of the array. These cameras were originally carried to monitor the deployment of the solar wings, which occurred just a few hours after launch in April 2014, and were not intended to be used afterwards.
     Following their switch-on, one camera provided a picture that clearly shows the strike on the solar panel.
     The power reduction is relatively small compared to the overall power generated by the solar wing, which remains much higher than what the satellite requires for routine operations.
     “Such hits, caused by particles of millimetre size, are not unexpected,” notes Holger Krag, Head of the Space Debris Office at ESA’s establishment in Darmstadt, Germany.
     “These very small objects are not trackable from the ground, because only objects greater than about 5 cm can usually be tracked and, thus, avoided by manoeuvring the satellites.
     “In this case, assuming the change in attitude and the orbit of the satellite at impact, the typical speed of such a fragment, plus additional parameters, our first estimates indicate that the size of the particle was of a few millimetres.
     “Analysis continues to obtain indications on whether the origin of the object was natural or man-made. The pictures of the affected area show a diameter of roughly 40 cm created on the solar array structure, confirming an impact from the back side, as suggested by the satellite’s attitude rate readings.”
     This event has no effect on the satellite’s routine operations, which continue normally.
     The Sentinel-1 satellites, part of the European Union’s Copernicus Programme, are operated by ESA on behalf of the European Commission.


For larger ones, use radar. It is surprisingly simple. For complicated reasons that I'm sure you can figure out for yourself, a meteor on a collision course will maintain a constant bearing (it's a geometric matter of similar triangles). So if the radar sees an object whose bearing doesn't change, but whose range is decreasing, it knows that You Have A Problem. (This happens on Earth as well. If you are racing a freight train to cross an intersection, and the image of the front of the train stays on one spot on your windshield, you know that you and the engine will reach the intersection simultaneously. This example was from Heinlein's ROCKET SHIP GALILEO.)

(Ken Burnside used this concept in his starship combat game Attack Vector: Tactical. From the point-of-view of the target, the incoming missile will hit if it stays on one bearing and does not move laterally. So a game aid called a ShellStar is used to detect the presence of lateral motion.)

The solution is simple as well, burn the engine a second or two in any direction (That was from Heinlein's SPACE CADET). One can make an hard-wired link between the radar and the engines, but it might be a good idea to have it sound an alarm first. This will give the crew a second to grab a hand-hold. You did install hand-holds on all the walls, didn't you? And require the crew to strap themselves into their bunks while sleeping.

Having said that, Samuel Birchenough points out that anybody who has played the game Kerbal Space Program know that an object that is not on a fixed bearing can still hit you. If your spacecraft and the other object are in orbit around a planet, the object's bearing will be constantly changing up to the last few kilometers before the collision.


The moon, now visibly larger and almost painfully beautiful, hung in the same position in the sky, such that he had to let his gaze drop as he lay in the chair in order to return its stare. This bothered him for a moment -- how were they ever to reach the moon if the moon did not draw toward the point where they were aiming?

It would not have bothered Morrie, trained as he was in a pilot's knowledge of collision bearings, interception courses, and the like. But, since it appeared to run contrary to common sense, Art worried about it until he managed to visualize the situation somewhat thus: if a car is speeding for a railroad crossing and a train is approaching from the left, so that their combined speeds will bring about a wreck, then the bearing of the locomotive from the automobile will not change, right up to the moment of the collision.

It was a simple matter of similar triangles, easy to see with a diagram but hard to keep straight in the head. The moon was speeding to their meeting place at about 2000 miles an hour, yet she would never change direction; she would simply grow and grow and grow until she filled the whole sky.

From ROCKET SHIP GALILEO by Robert Heinlein. 1947.

To guard against larger stuff Captain Yancey set up a meteor-watch much tighter than is usual in most parts of space. Eight radars scanned all space through a global 360°. The only condition necessary for collision is that the other object hold a steady bearing-no fancy calculation is involved. The only action necessary then to avoid collision is to change your own speed, any direction, any amount. This is perhaps the only case where theory of piloting is simple.

Commander Miller put the cadets and the sublieutenants on a continuous heel-and-toe watch, scanning the meteor-guard 'scopes. Even if the human being failed to note a steady bearing the radars would "see" it, for they were so rigged that, if a "blip" burned in at one spot on the screen, thereby showing a steady bearing, an alarm would sound- and the watch officer would cut in the jet, fast!...

From SPACE CADET by Robert Heinlein. 1948.

He said casually, “There were a lot of tall stories back in the Early Twentieth Century about spacecraft filled with course-computing gear that measured the course of meteorites, then directed the spacecraft. A more practical study of any such device shows that any extraneous object that does not change its aspect angle is necessarily on a collision course. Ergo, any target that does not move causes the alarm to ring, and the autopilot to swerve aside.” He grinned and added in a low voice, “We’re as safe as if we were all in bed.”

From SPACEMEN LOST by George O. Smith (1954)

Hull Patching

If the habitat module or space suit is punctured, all the air will start rushing out. Unless you and the other occupants want to experience first-hand all the many horrible ways that space kills you, you'd better patch that hole stat!


An instrument called a Manometer will register a sudden loss of pressure and trigger an alarm. Life support will start high-pressure flood of oxygen, and release some bubbles. The bubbles will rush to the breach, pointing them out to the crew.

The crew will grab an emergency hull patch (thoughtfully affixed near all external hull walls) and seal the breach. The emergency hull patches are metal discs. They look like saucepan covers with a rubber flange around the edge. They will handle a breach up to fifteen centimeters in diameter. Never slap them over the breach, place it on the hull next to the breach and slide it over. Once over the breach, air pressure will hold it in place until you can make more permanent repairs.

A more advanced alternative to bubbles are "plug-ups" or "tag-alongs". These are plastic bubbles full of helium and liquid sealing plastic. The helium is enough to give them neutral buoyancy, so they have no strong tendency to rise or sink. They fly to the breach, pop, and plug it with quick setting goo. Much to the relief of the crew caught in the same room with the breach when the automatic bulkheads slammed shut.

Now you have some breathing space to break out the arc welder and apply a proper patch.


      If you ever wondered what a spacraft leak repair kit looks like, Pratley epoxy putty was carried in the Apollo modules as it was a high-temperature epoxy. Due to apartheid South Africa being the only country who had developed it, some creative loopholes were used to get it for use by NASA. But it's still the same stuff you find on hardware store shelves here.

     It consists of two wads of clay-like material that you mash together and mix, hardening to rock hardness in a couple of hours.

     Presumably a similar epoxy is used today on the International Space Station.


      “Three …" Jeff looked back at the crawling needle. “Two …”


     At first he thought the motors had fired wrong again. But the old motors could not have made the hot red flash that surprised him, or the sharp blast that left a ringing in his ears. Air was roaring, when he could hear again. He blinked and found a hole torn in the hull just over Ty’s head.
     Their air was howling out into empty space.
     “We’ve been hit!” The thought struck him like a blow.

     But he knew what to do. He grabbed the orange-painted sealing gun off the wall beside his seat, aimed at the black hole, and fired. A fat black balloon of sealing foam popped out and flew into the hole.
     “Oh-oh!” His lips moved stiflly. “Hole’s too big — ”
     But the foam ball caught on the torn metal edges. Air pressure squeezed it wider. In a second the roaring stopped. The hole was sealed.

From TRAPPED IN SPACE by Jack Williamson (1968)

(ed note: Our Heroes are sitting inside a compartment in the Martian Congressional Republic Navy flagship Donnager. A railgun round shoots through the compartment, puncturing it to vacuum. Unfortunately the round also decapitates poor Shed.)

Holden froze, watching the blood pump from Shed's neck, then whip away like smoke into an exhaust fan. The sounds of combat began to fade as the air was sucked out of the room. His ears throbbed and then hurt like someone had put ice picks in them. As he fought with his couch restraints, he glanced over at Alex. The pilot was yelling something, but it didn't carry through the thin air. Naomi and Amos had gotten out of their couches already, kicked off, and were flying across the room to the two holes. Amos had a plastic dinner tray in one hand. Naomi, a white three-ring binder. Holden stared at them for the half second it took to understand what they were doing. The world narrowed, his peripheral vision all stars and darkness.

By the time he'd gotten free, Amos and Naomi had already covered the holes with their makeshift patches. The room was filled with a high-pitched whistle as the air tried to force its way out through the imperfect seals. Holden's sight began to return as the air pressure started to rise. He was panting hard, gasping for breath. Someone slowly turned the room's volume knob back up and Naomi's yells for help became audible.

"Jim, open the emergency locker!" she screamed.

She was pointing at a small red-and-yellow panel on the bulkhead near his crash couch. Years of shipboard training made a path through the anoxia and depressurization. and he yanked the tab on the locker's seal and pulled the door open. Inside were a white first aid kit marked with the ancient red-cross symbol, half a dozen oxygen masks, and a sealed bag of hardened plastic disks attached to a glue gun. The emergency-seal kit. He snatched it.

"Just the gun." Naomi yelled at him. He wasn't sure if her voice sounded distant because of the thin air or because the pressure drop had blown his eardrums.

Holden yanked the gun free from the bag of patches and threw it at her. She ran a bead of instant sealing glue around the edge of her three-ring binder. She tossed the gun to Amos, who caught it with an effortless backhand motion and put a seal around his dinner tray. The whistling stopped, replaced by the hiss of the atmosphere system as it labored to bring the pressure back up to normal. Fifteen seconds.

     "Gauss round," Alex said. "Those ships have rail guns."
     "Belt ships with rail guns?" Amos said. "Did they get a f*****g navy and no one told me?"
     "Jim, the hallway outside and the cabin on the other side are both in vacuum," Naomi said. "The ship's compromised."
     Holden started to respond, then caught a good look at the binder Naomi had glued over the breach. The white cover was stamped with black letters that read MCRN EMERGENCY PROCEDURES (Martian Congressional Republic Navy). He had to suppress a laugh that would almost certainly go manic on him.
     "Jim," Naomi said, her voice worried.
     "I'm okay, Naomi," Holden replied, then took a deep breath. "How long do those patches hold?"
     Naomi shrugged with her hands, then started pulling her hair behind her head and tying it up with a red elastic band.
     "Longer than the air will last. If everything around us is in vacuum, that means the cabin's running on emergency bottles. No recycling. I don't know how much each room has, but it won't be more than a couple hours."
     "Kinda makes you wish we'd worn our f*****g suits, don't it?" Amos asked.
     "Wouldn't have mattered," Alex said. "We'd come over here in our enviro suits, they'd just have taken 'em away."

From LEVIATHAN WAKES by "James S.A. Corey" (Daniel Abraham and Ty Franck) 2011.
First novel of The Expanse

"Where're the plug-ups?" the Commander demands. "Damn it, where the hell are the plug-ups?"

"Oh." The man doing the relay talking hits a switch. Little gas-filled plastic balls swarm into the compartment. They range from golf-ball to tennis-ball size.

"Enough. Enough," Nicastro growls. "We've got to be able to see."

A new man, I decide. He's heard about the Commander. He's too anxious to look good. He's concentrating too much. Doing his job one part at a time, with such thoroughness that he muffs the whole.

The plug-ups will drift aimlessly throughout the patrol, and will soon fade into the background environment. No one will think about them unless the hull is breached. Then our lives could depend on them. They'll rush to the hole, carried by the escaping atmosphere. If the breach is small, they'll break trying to get through. A quick-setting, oxygen-sensitive goo coats their insides.

The cat scrambles after the nearest ball. He bats it around. It survives his attentions. He pretends a towering indifference. He's a master of that talent of the feline breed, of adopting a regal dignity in the face of failure, just in case somebody is watching.

Breaches too big for the plug-ups probably wouldn't matter. We would be dead before we noticed them.

From PASSAGE AT ARMS by Glen Cook (1985)

(ed note: a reporter is touring some Lunar tunnels being drilled to expand the colony)

     "Yes and no. The airlocks would limit an accident all right, if there was one—which there won't be—this place is safe. Primarily they let us work on a section of the tunnel at no pressure without disturbing the rest of it. But they are more than that; each one is a temporary expansion joint. You can tie a compact structure together and let it ride out a quake, but a thing as long as this tunnel has to give, or it will spring a leak. A flexible seal is hard to accomplish in the Moon."
     "What's wrong with rubber?" I demanded. I was feeling jumpy enough to be argumentative. "I've got a ground-car back home with two hundred thousand miles on it, yet I've never touched the tires since they were sealed up in Detroit."
     Knowles sighed. "I should have brought one of the engineers along, Jack. The volatiles that keep rubbers soft tend to boil away in vacuum and the stuff gets stiff. Same for the flexible plastics. When you expose them to low temperature as well they get brittle as eggshells."

     There were perhaps a dozen bladder-like objects in the tunnel, the size and shape of toy balloons. They seemed to displace exactly their own weight of air; they floated without displaying much tendency to rise or settle. Konski batted one out of his way and answered me before I could ask. "This piece of tunnel was pressurized today," he told me. "These tag-alongs search out stray leaks. They're sticky inside. They get sucked up against a leak, break, and the goo gets sucked in, freezes and seals the leak."
     "Is that a permanent repair?" I wanted to know.
     "Are you kidding? It just shows the follow-up man where to weld."
     "Show him a flexible joint," Knowles directed.
     "Coming up." We paused half-way down the tunnel and Konski pointed to a ring segment that ran completely around the tubular tunnel. "We put in a flex joint every hundred feet. It's glass cloth, gasketed onto the two steel sections it joins. Gives the tunnel a certain amount of springiness."
     "Glass cloth? To make an airtight seal?" I objected.
     "The cloth doesn't seal; it's for strength. You got ten layers of cloth, with a silicone grease spread between the layers. It gradually goes bad, from the outside in, but it'll hold five years or more before you have to put on another coat."

(ed note: then the accident happens)

     "Looks tight, but I hear—Oh, oh! Sister!" His beam was focused on a part of the flexible joint, near the floor.
     The "tag-along" balloons were gathering at this spot. Three were already there; others were drifting in slowly. As we watched, one of them burst and collapsed in a sticky mass that marked the leak.
     The hole sucked up the burst balloon and began to hiss. Another rolled onto the spot, joggled about a bit, then it, too, burst. It took a little longer this time for the leak to absorb and swallow the gummy mass.
     Konski passed me the light. "Keep pumping it, kid." He shrugged his right arm out of the suit and placed his bare hand over the spot where, at that moment, a third bladder burst.
     "How about it, Fats?" Mr. Knowles demanded.
     "Couldn't say. Feels like a hole as big as my thumb. Sucks like the devil."
     "You got the leak checked?"
     "I think so. Go back and check the gage. Jack, give him the light."
     Knowles trotted back to the airlock. Presently he sang out, "Pressure steady!"
     "Can you read the vernier?" Konski called to him.
     "Sure. Steady by the vernier."
     "How much we lose?"
     "Not more than a pound or two. What was the pressure before?"
     "Lost a pound four tenths, then."
     "Not bad. Keep on going, Mr. Knowles. There's a tool kit just beyond the lock in the next section. Bring me back a number three patch, or bigger."
     "Right." We heard the door open and clang shut, and we were again in total darkness. I must have made some sound for Konski told me to keep my chin up.
     Presently we heard the door, and the blessed light shone out again. "Got it?" said Konski.
     "No, Fatso. No..." Knowles' voice was shaking. "There's no air on the other side. The other door wouldn't open."
     "Jammed, maybe?"
     "No, I checked the manometer. There's no pressure in the next section."
     Konski whistled again. "Looks like we'll wait till they come for us. In that case — Keep the light on me, Mr. Knowles. Jack, help me out of this suit."
     "What are you planning to do?"
     "If I can't get a patch, I got to make one, Mr. Knowles. This suit is the only thing around." I started to help him—a clumsy job since he had to keep his hand on the leak.
     "You can stuff my shirt in the hole," Knowles suggested.
     "I'd as soon bail water with a fork. It's got to be the suit; there's nothing else around that will hold the pressure." When he was free of the suit, he had me smooth out a portion of the back, then, as he snatched his hand away, I slapped the suit down over the leak. Konski promptly sat on it. "There," he said happily, "we've got it corked. Nothing to do but wait."
     I started to ask him why he hadn't just sat down on the leak while wearing the suit; then I realized that the seat of the suit was corrugated with insulation—he needed a smooth piece to seal on to the sticky stuff left by the balloons.
     "Let me see your hand," Knowles demanded.
     "It's nothing much." But Knowles examined it anyway. I looked at it and got a little sick. He had a mark like a stigma on the palm, a bloody, oozing wound. Knowles made a compress of his handkerchief and then used mine to tie it in place.

From GENTLEMEN, BE SEATED! by Robert Heinlein (1948)
How Long Til Air Is Gone?

Once a pressurized habitat module or space suit springs a leak in the vacuum of space, all the air starts howling out the hole escaping into the void. Since people generally need air to breath or they die, there is an intense interest in how long it will take the air to go bye-bye.

Assuming Terra-normal pressure and density inside, and zero pressure outside, the effective speed of the air whistling out the breach works out to a smidgen under 400 m/sec. Veteran rocketeers, vacationing on Terra, tend to have a momentary panic if they feel the wind. Their instincts tell them there is a hull breach.

You probably won't use this equation, but to calculate an approximate time it will take for all the air to totally escape:

dm/dt = A * sqrt[ 2 * P0 * rho ]


  • dm/dt = the rate (mass per unit time) at which air leaks into vacuum (in rocket engines they call it mDot or ṁ)
  • A = area of the hole it's leaking through
  • P0 = stagnation pressure in room (far from the hole)
  • rho = air density inside the room far from the hole
  • sqrt[x] = square root of x

If you want to get fancy and take the atmospheric temperature into account, use Fliegner's Formula (equation from quote below):

dm/dt = 0.04042 * ((A * P0) / sqrt[ T0 ])


  • dm/dt = the rate at which air leaks into vacuum (kg/sec)
  • P0 = stagnation pressure in room (far from the hole) (Pascals Pa)
  • A = area of the hole (m2)
  • T0 = stagnation temperature in room (far from the hole) (Kelvin, about 293 K for room temperature 20°C)


However, what we (and the hapless people inside the breached compartment) are more interested in is how long it takes the pressure to drop to the deadly level of anoxia, i.e., how long the hapless people have to live before dying of suffocation (equation from quote below).

t = 0.086 * (V / A) * ( ln[ P0/Pƒ ] / sqrt[ T ])

tcabin = 0.00699 * (V / A)

tspacesuit = 0.00910 * (0.06 / A)


  • t = time for the pressure to drop to anoxia (seconds)
  • tcabin = time for the pressure to drop to anoxia in a habitat module cabin with high pressure (seconds)
  • tspacesuit = time for the pressure to drop to anoxia in a spacesuit with low pressure (seconds)
  • V = volume of compartment (m3)
  • A = Area of the hole (m2)
  • P0 = stagnation pressure in room (far from the hole) (Pascals) (cabin normal = 101,300; spacesuit normal 32,400)
  • Pƒ = final pressure in room (Pascals) (cabin anoxia = 25,200; spacesuit anoxia = 5,300)
  • T = Stagnation temperature in room (far from the hole) (Kelvin) (about 293 K for room temperature ~20°C; note √293 ~ 17.12)
  • sqrt[x] = square root of x
  • ln[x] = natural logarithm of x
  • 0.00699 = 0.086 * ln[ 101,300/25,200 ] / sqrt[ 293 ] (cabin normal to cabin anoxia)
  • 0.00910 = 0.086 * ln[ 32,400/5,300 ] / sqrt[ 293 ] (spacesuit normal to spacesuit anoxia)
  • 0.04 to 0.06 = approximate volume of air in a space suit between inner suit and astronaut's body (m3)

Remember if the compartment is using high pressure (101.3 kPa) breathing mix anoxia strikes when Pƒ = 25.2 kPa, and with a low pressure (32.4 kPa) breathing mix at Pƒ = 5.3 kPa.

So if a posh passenger cabin of 15 cubic meters with high pressure has a 3 centimeter (one inch) diameter hole (area 7.07×10-4 m2) blown in the bulkhead by a wayward meteor, the inhabitants have an entire 148 seconds (about two and a half minutes) before anoxia strikes.

A .45 calibre ACP bullet has a diameter of .451 inches or 11.5 mm. So if it punches a perfect hole the same diameter as the bullet the hole will have a radius of 0.00575 meters and an area of 0.000104 square meters. This will bring the 15 m3 cabin down to anoxia in about 1008 seconds or 16.8 minutes. The time will drop if the hole is more ragged or if there are multiple holes. Obviously each additional hole cuts the time in half.

Somebody in a space suit doesn't have that kind of time. Dimitri SIyde tells me that according to the NASA EMU LSS/SSA Data Book the “free volume” inside a space suit is from 0.04 to 0.06 cubic meters (the gas volume of the anthropometric clearance between the crewmember and the inside of the suit including the PLSS oxygen ventilating circuit). The space suit uses low pressure. A hole a half-centimeter in diameter has a hole area of 1.96×10-5 square meters. As long as the suit's air tanks can keep up the loss the pressure won't drop. But once the tanks are empty, the pressure will drop to anoxia levels in a mere 27.9 seconds.

Does this mean that crewpeople in a combat spacecraft will do their fighting in space suits? Probably not, for the same reason that crewpeople in combat submarines do not do their fighting while wearing scuba gear. The gear is bulky, confining, and tiring to wear. They will not wear it even though in both cases the vessel is surrounded by stuff you cannot breath. They may, however, wear partial-pressure suits or have emergency space suits handy. Those suits will only protect you for ten minutes or so, but in exchange you won't be hampered like you were wearing three sets of snow-suits simultaneously.

Instead, the ship's pressurized inhabitable section will be divided into individual sections by bulkheads, and the connecting airtight hatches will be shut. The air pressure might be lowered a bit.



All manned spacecraft have a life support section that is pressurised with a suitable gas, usually air, to ensure the survival of its occupants. When the integrity of this region is breached, through impact or other cause, the gas escapes from within the spacecraft out into space. The rate of escape is dependent on the size of the breach, the volume of the pressurised space, the initial pressure and the nature of the gas. This note explores the depressurisation time with respect to these parameters. Spaceship depressurisation


There are two laws of basic physics that we need to explore the problem of gas escaping through a hole from a pressurised volume into the vacuum of space. One is the ideal gas equation and the other is Bernoulli's law of fluid dynamics.

The Ideal Gas Equation

p V = M R T / μ


p is the pressure of the gas
V is the volume which the gas occupies
M is the mass of the gas R is the Universal Gas Constant ( = 8.31 in SI units )
T is the absolute temperature of the gas
μ is the molecular mass of the gas

Bernoulli's Law

p + ½ρv2 + ρgh = constant along a streamline


p is the pressure of the gas
ρ is the density of the gas
v is the velocity of the gas
g is the gravitational acceleration
h is the height above a gravitational datum
Note: In zero gravity the last term is zero.


The schematic diagram at left shows the situation and variables to which we shall apply the above laws. The life support volume may be only a fraction of the total spacecraft volume. It is that part of the craft that is pressurised for the sustainability of its crew and any passengers it may carry.

We consider a streamline that passes through the hole, and apply Bernoulli's law to a point just inside the hole and second point just outside the hole. We assume that in this short distance the gas density remains constant. This gives us the equation:

pi + ½ρvi2 = po + ½ρve2

Noting that the pressure in space (po) is essentially zero, and that the gas velocity (vi) inside the spacecraft is a lot less than the escape velocity (ve) of the gas outside the craft (and thus can be neglected with respect to it), we have that:

pi = ½ρve2

giving an expression for the escape velocity of:

ve = √( 2 pi / ρ )

We can consider the volume of gas escaping each second as having a cylindrical volume with a diameter equal to the diameter of the hole and a length equal to the distance travelled by the gas in one second. The mass of the gas escaping in one second is then this volume times the gas density. This is the rate of mass loss per unit time, and may be written as:

dm/dt = ρ Ah ve

Substituting in the previous expression for exhaust velocity we find:

dm/dt = Ah √(2 pi ρ ) ...[eq.1]

We note that density ρ = M / V ...[eq.2]

and we use the Ideal Gas Equation to find the relation between pi and ρ :

pi = ρ R T / μ ...[eq.3]

We can now use the last three numbered equations to iteratively solve for the time variation of cabin pressure, mass and/or density.


An algorithm to calculate the time variation of cabin atmospheric parameters is specified as follows:

  • Step 1 - Specify initial pressure
  • Step 2 - Compute initial density (eq.3), inital mass (eq.2)
  • Step 3 - Compute mass loss per unit time (eq.1)
  • Step 4 - Compute new mass at new time (Mnew = Mold - massloss)
  • Step 5 - Compute new density (eq.2), new pressure (eq.3)
  • Step 6 - Repeat from step 3 as required

The following table contains the code for a simple program in Quick Basic that implements the above algorithm, displaying a table of gas pressure, mass and density every 100 seconds.


CLS             'clear screen
mw = .029       'molecular weight of gas (kg/mole)  - air=0.029
temp = 293      'temp in kelvin (=20 Celcius)
Rg = 8.314      'Universal Gas Constant (J / mole-K)
press = 100000  'pressure in Pascal (Earth atmospheric = 101,300 Pa)
press0 = press  'keep record of initial pressure
vol = 30        'spacecraft cabin volume cubic metres
Ah = .0001      'impact hole in square metres
tm = 0          'start time (seconds)
PRINT USING "Spacecraft depressurisation - Hole size = #####.## sq
 cm"; Ah * 10000
PRINT "Time(sec/min)  Mass(kg)  Density(kg/m^3)  Pressure(kPa)"
f1$ = " ####/###.#     ###.#        ##.##           ###.##"
'compute initial mass and density of gas
mass = press * vol * mw / Rg / temp	'initial mass of gas
rho = mass / vol	'initial density
'now advance in time
'print out parameters every 100 seconds
IF tm MOD 100 = 0 THEN
  PRINT USING f1$; tm; tm / 60; mass; rho; press / 1000
tm = tm + 1			'advance time by one second
massloss = Ah * SQR(2 * press * rho)	'compute mass loss in 1 sec
mass = mass - massloss		'compute new mass
rho = mass / vol		'compute new density
press = rho * Rg * temp / mw	.compute new pressure
LOOP WHILE press > press0 / 10  'do while pressure>10% initial

The next table presents the output of the above program with the parameters as specified.

 Spacecraft depressurisation - Hole size = 1.00 sq cm

Time(sec/min)  Mass(kg)  Density(kg/m^3)  Pressure(kPa)
    0/  0.0      35.7         1.19           100.00
  100/  1.7      31.2         1.04            87.22
  200/  3.3      27.2         0.91            76.08
  300/  5.0      23.7         0.79            66.35
  400/  6.7      20.7         0.69            57.88
  500/  8.3      18.0         0.60            50.48
  600/ 10.0      15.7         0.52            44.03
  700/ 11.7      13.7         0.46            38.40
  800/ 13.3      12.0         0.40            33.50
  900/ 15.0      10.4         0.35            29.22
 1000/ 16.7       9.1         0.30            25.48
 1100/ 18.3       7.9         0.26            22.23
 1200/ 20.0       6.9         0.23            19.39
 1300/ 21.7       6.0         0.20            16.91
 1400/ 23.3       5.3         0.18            14.75
 1500/ 25.0       4.6         0.15            12.86
 1600/ 26.7       4.0         0.13            11.22


The following graph shows how cabin pressure decreases with time. The different curves indicate different hole sizes (in terms of the hole area). In these graphs the cabin volume is assumed to be 30 cubic metres and the initial pressure 100 kilopascals of air (20% oxygen and 80% nitrogen). The mean atmospheric pressure on the Earth's surface is 101.3 kPa.

We can see that a one square centimetre hole will reduce cabin pressure by 50% in 500 seconds (8.3 minutes). This value scales in inverse proportion to hole area. Thus a 10 sq cm hole will only take 50 seconds to halve the pressure, whereas a 0.1 sq cm hole (10 square millimetres) will take 5000 seconds.

Cabin pressure vs hole size

The next graph assumes a hole of one square centimetre and plots how the cabin pressure varies with time for a range of cabin volumes. The smallest volume (3 m3) might correspond to a personal escape pod, the next (30 m3) to a multiperson reentry capsule, and the last two to small and large space stations respectively.

In this case the time to reduce the pressure by half scales linearly with the cabin size. Thus while a 30 cubic metre cabin will depressurise by 50% in 500 sceonds, a 300 cubic metre space station will take 5000 seconds for a 50% reduction in pressure.

Cabin pressure vs hole size

Now we show how different gases and initial pressures affect the depressurisation time. Again we assume a fixed hole size of one square centimetre. Gases with a higher molecular weight than air will show a longer time to depressurise and gases with a lower molecular weight a shorter time. Pure oxygen (MW=0.032 kg/mole) takes slighly longer to leave the cabin than does air (MW=0.029). A helium-oxygen mix (MW=0.0.10) takes less time. The depressurisation time scales linearly with the gas molecular weight.

If pure oxygen was used as a cabin atmosphere it would normally be present at a lower initial pressure anyway. At an inital pressure of 20 kPa (which corresponds to the partial pressure it has in 100 kPa air) the 50% depressurisation time is identical to that of pure oxygen at 100 kPa. Thus we see that initial pressure does not affect the depressurisation time.

Cabin pressure vs hole size

All three graphs above have assumed that the depressurisation process is isothermal (constant temeperature) with a cabin temperature of 293 K. This is a reasonably valid assumption as the cabin and surroundings will have a much greater thermal mass than the air within. The specified temperature will also be close to that necessary to keep humans comfortable. However, it is interesting to investigate how temperature affects the time to depressure. The following graph plots time versus cabin pressure for temperatures of 293 K (20 C) and 29 K (-244 C). This latter value might be the temperature of a derelict craft that has been abandoned in the outer solar system for some time before suffering an impact that produces a 1 sq cm hole.

Cabin pressure vs hole size

Two more factors must be mentioned that may affect the depressurisation time. First we note that a gas cannot expand at a velocity greater than its speed of sound. This may in some cases decrease the rate at which gas escapes and thus lengthen the depressurisation time. Secondly, if the hole size is smaller than the wall thickness there will be a resistance to flow through the resultant non-zero length pipe due to a slower boundary layer at the edges of the hole. This will also serve to limit the escape rate and increase the time to depressure. The times shown in the graphs above should thus be regarded as minimum times.


Most humans live in an atmosphere of 20% oxygen and 80% inert gas (mostly nitrogen) at a total pressure of around 100 kilopascal (kPa). The nominal pressure at sea-level on the Earth is 101.3 kPa and this decreases with altitude by roughly ten kPa for every kilometre, at least for the first few kilometres.

For a person accustomed to living on Earth at sea-level the first symptoms of hypoxia (lack of oxygen) appear around an altitude of 3000 m. The visual system at low light levels is impaired (pilots of light aircraft without supplemental oxygen are advised not to fly above 3000 m (10,000 feet) at night). Breathlessness will occur under exertion, and it may be more difficult to sleep. On the island of Hawaii there are many large optical telescopes on the peak of Mauna Kea, which is 4,200 m high. Astronomers who work on this mountain do not spend large amounts of time at the peak, but are accommodated at a lower level around 2,700 m. There is also a visitor's centre at this height, and anyone who wants to ascend to the summit to see the telescopes and do a little stargazing is advised to spend a few hours at this level to acclimatise before going on to the peak.

It is of course, possible to acclimatise to high altitudes, and small populations of people do live above 3,000 m. People are also diverse and different people experience hypoxia at different partial pressures of oxygen.

However, as a rule of thumb, a person accustomed to breathing air at sea-level pressure (100 kPa) tends to lose consciousness at about 30 kPa, and the ability to perform useful work will occur before this pressure is reached.

If we use a value of 30 kPa as the lowest pressure of air that can possibly sustain human consciousness, and note that this pressure is reached in about 30 seconds when a cabin of one cubic metre pressurised to 100 kPa is breached by a 1 square centimetre hole, we can use the scaling rules noted above to give a quick formula:

Lifetime(secs) = 30 * Cabin_Volume(m3) / Hole_Size(cm2)

Once again we note that this is a minimum time. Other factors may literally provide more breathing time, and of course a person does not die immediately after losing consciousness. However, if no remedial action occurs (e.g., from an outside source or another astronaut in a space suit), this time is effectively the useful lifetime of the individual.

From SPACECRAFT DEPRESSURISATION by Australian Space Academy

Uncontrolled decompression is an unplanned drop in the pressure of a sealed system, such as an aircraft cabin or hyperbaric chamber, and typically results from human error, material fatigue, engineering failure, or impact, causing a pressure vessel to vent into its lower-pressure surroundings or fail to pressurize at all.

Such decompression may be classed as Explosive, Rapid, or Slow:

  • Explosive decompression (ED) is violent, the decompression being too fast for air to safely escape from the lungs.
  • Rapid decompression, while still fast, is slow enough to allow the lungs to vent.
  • Slow or gradual decompression occurs so slowly that it may not be sensed before hypoxia sets in.


The term uncontrolled decompression here refers to the unplanned depressurisation of vessels that are occupied by people; for example, a pressurised aircraft cabin at high altitude, a spacecraft, or a hyperbaric chamber. For the catastrophic failure of other pressure vessels used to contain gas, liquids, or reactants under pressure, the term explosion is more commonly used, or other specialised terms such as BLEVE may apply to particular situations.

Decompression can occur due to structural failure of the pressure vessel, or failure of the compression system itself. The speed and violence of the decompression is affected by the size of the pressure vessel, the differential pressure between the inside and outside of the vessel, and the size of the leak hole.

The US Federal Aviation Administration recognizes three distinct types of decompression events in aircraft:

  • Explosive decompression
  • Rapid decompression
  • Gradual decompression

Explosive decompression

Explosive decompression occurs at a rate swifter than that at which air can escape from the lungs, typically in less than 0.1 to 0.5 seconds. The risk of lung trauma is very high, as is the danger from any unsecured objects that can become projectiles because of the explosive force, which may be likened to a bomb detonation.

After an explosive decompression within an aircraft, a heavy fog may immediately fill the interior as the relative humidity of cabin air rapidly changes as the air cools and condenses. Military pilots with oxygen masks have to pressure-breathe, whereby the lungs fill with air when relaxed, and effort has to be exerted to expel the air again.

Rapid decompression

Rapid decompression typically takes more than 0.1 to 0.5 seconds, allowing the lungs to decompress more quickly than the cabin. The risk of lung damage is still present, but significantly reduced compared with explosive decompression.

Gradual decompression

Slow, or gradual, decompression occurs slowly enough to go unnoticed and might only be detected by instruments. This type of decompression may also come about from a failure to pressurize as an aircraft climbs to altitude. An example of this is the 2005 Helios Airways Flight 522 crash, in which the pilots failed to check the aircraft was pressurising automatically and then to react to the warnings that the aircraft was depressurising, eventually losing consciousness (along with most of the passengers and crew) from hypoxia.

Decompression injuries

The following physical injuries may be associated with decompression incidents:

From the Wikipedia entry for UNCONTROLLED DECOMPRESSION

Continuous Decompression: Averted in exactly the hard-SFnal ways one might expect it to be. Specifically, among other things:

(a) Explosive decompression be explosive, yo. Specifically, the air doesn’t hang around producing wind and blowing things around; it leaves. But also:

(b) Most decompression is not explosive. Mostly, the air just leaks out the hole until the hole is plugged, and does not in fact lead to immediate inability to breathe (although the pressure is continuously dropping) or air currents big enough to such everything through a hole smaller than it is. It just sets off alarms and makes unpleasant shrieking sounds while people get patch kits and close spacetight doors.

Especially if it’s, say, a bullet hole in the window of a cylinder habitat, which even if left untended with all the doors open would lead to complete depressurization in, y’know, a few days. At the fastest.


(ed note: Mr. Latchman is discussing The Expanse Season 1, Episode 4 "CQB". Our Heroes are sitting inside a compartment in the Martian Congressional Republic Navy flagship Donnager. A railgun round shoots through the compartment, puncturing it to vacuum. Unfortunately the round also decapitates poor Shed.)

The Physics Of Decompression And Constricted Airflows

We do not see the room explosively decompress when the railgun projectile shoots through the Donnager's hull and wall. Except for the fact that air is being sucked out into "hard vacuum," everyone manages to stay in their seats. This happens for a few reasons. The first is the hole, or constriction, is too small for all the air in the room to explosively leave the room. The second deals with the fact that air is made of atoms. Air escaping the hole in the hull to the vacuum of space leaves at approximately the speed of sound. As air molecules exit the hole, the remaining molecules have to "catch up." Think what happens in a traffic jam. All cars do not move together. One car slowly inches forward and then everyone follows. This means there is no explosive decompression unless the entire wall is suddenly removed. While the crew has some time to act, that time is very limited.

Scientists and engineers have looked at the physics of constricted airflow for some time with regard to aircraft. It is a very good idea to know what happens to an aircraft if a hole forms while in flight. A. Fliegner was one of the first engineers to look at this problem and was able to work out how much air leaves depending on the pressure inside a cabin and the size of a hole. We know this as Fliegner's Formula:

where dm/dt is the mass flow, A is the area of the hole, P0 is the pressure inside the cabin, and T0 is the room temperature.

As we expect, the air flow depends on the hole's area, cabin pressure and temperature. Of course, Fliegner's Formula is not that accurate. As the leak progresses, the pressure in the cabin drops and this also affects air flow through the hole. Have no fear, we can use the equation and a little physics to figure out the time it takes the pressure to drop to a certain level. We get:

We have some new variables: V is the volume of the room they are in and Pƒ is the final pressure. Now that we have figured out the equation, we can model what happens inside the cabin and how much time the Canterbury crew have to act.

The Human Race Needs To Breathe To Survive

Air is approximately 20% oxygen. If that level falls to approximately 10% or half atmospheric pressure, you will not have enough oxygen to function and become hypoxic. While you would not necessarily die, you can fall unconscious. We assume that the Canterbury crew can not help themselves and will eventually die as the cabin pressure decreases until all the air is sucked out to the vacuum. Basically, everyone dies when the pressure falls to 50%. Maybe Shed is the lucky one here.

(ed note: actually the documentation I've seen suggests that hypoxia will hit when the pressure falls to 24.8%, or 25.2 kPa, corresponding to an oxygen partial pressure of 5.3 kPa. But the mathematics are the important thing.)

Graph shows the time for the cabin pressure to fall until no air is left.

While we do not have the exact dimensions of the room, we can make a few assumptions. Based on the body sizes of the crew, I assume the room is 10 meters by 10 meters by 5 meters or 500 cubic meters in size. The temperature of the room is about 27°C (80°F or 293K). If we plot the graph over time we see that the pressure drops to half its value where everyone has a little over a minute to plug up the holes.

Does "The Expanse" Get It Right?

Assuming that everything happens in real-time, from the moment Sed loses his head to the second the holes are sealed, the crew manages to do seal the holes with some seconds to spare. While the estimated size of the room may be larger than it really is, the point is... They survive! The show definitely gets the science right and the urgency the crew must act to save their lives.


It was just after reveille, "A" deck time, and I was standing by my bunk, making it up. I had my Scout uniform in my hands and was about to fold it up and put it under my pillow. I still didn't wear it. None of the others had uniforms to wear to Scout meetings so I didn't wear mine. But I still kept it tucked away in my bunk.

Suddenly I heard the goldarnest noise I ever heard in my life. It sounded like a rifle going off right by my ear, it sounded like a steel door being slammed, and it sounded like a giant tearing yards and yards of cloth, all at once.

Then I couldn't hear anything but a ringing in my ears and I was dazed. I shook my head and looked down and I was staring at a raw hole in the ship, almost between my feet and nearly as big as my fist. There was scorched insulation around it and in the middle of the hole I could see blackness—then a star whipped past and I realized that I was staring right out into space.

There was a hissing noise.

I don't remember thinking at all. I just wadded up my uniform, squatted down, and stuffed it in the hole. For a moment it seemed as if the suction would pull it on through the hole, then it jammed and stuck and didn't go any further. But we were still losing air. I think that was the point at which I first realized that we were losing air and that we might be suffocated in vacuum.

There was somebody yelling and screaming behind me that he was killed and alarm bells were going off all over the place. You couldn't hear yourself think. The air-tight door to our bunk room slid across automatically and settled into its gaskets and we were locked in.

That scared me to death.

I know it has to be done. I know that it is better to seal off one compartment and kill the people who are in it than to let a whole ship die—but, you see, I was in that compartment, personally. I guess I'm just not the hero type.

I could feel the pressure sucking away at the plug my uniform made. With one part of my mind I was recalling that it had been advertised as "tropical weave, self ventilating" and wishing that it had been a solid plastic rain coat instead. I was afraid to stuff it in any harder, for fear it would go all the way through and leave us sitting there, chewing vacuum. I would have passed up desserts for the next ten years for just one rubber patch, the size of my hand.

     The screaming had stopped; now it started up again. It was Noisy Edwards, beating on the air-tight door and yelling, "Let me out of here! Get me out of here!"
     On top of that I could hear Captain Harkness's voice coming through the bull horn. He was saying, "H-twelve! Report! H-twelve! Can you hear me?"
     On top of that everybody was talking at once.
     I yelled: "Quiet!" at the top of my voice—and for a second or so there was quiet.
     Peewee Brunn, one of my Cubs, was standing in front of me, looking big-eyed. "What happened, Billy?" he said.
     I said, "Grab me a pillow off one of the bunks. Jump!"
     He gulped and did it. I said, "Peel off the cover, quick!"
     He did, making quite a mess of it, and handed it to me—but I didn't have a hand free. I said, "Put it down on top of my hands."

It was the ordinary sort of pillow, soft foam rubber. I snatched one hand out and then the other, and then I was kneeling on it and pressing down with the heels of my hands. It dimpled a little in the middle and I was scared we were going to have a blowout right through the pillow. But it held. Noisy was screaming again and Captain Harkness was still asking for somebody, anybody, in compartment H-12 to tell him what was going on. I yelled "Quiet!" again, and added, "Somebody slug Noisy and shut him up."

That was a popular idea. About three of them jumped to it. Noisy got clipped in the side of the neck, then somebody poked him in the pit of his stomach and they swarmed over him. "Now everybody keep quiet," I said, "and keep on keeping quiet. If Noisy lets out a peep, slug him again." I gasped and tried to take a deep breath and said, "H-twelve, reporting!"

     The Captain's voice answered, "What is the situation there?"
     "There is a hole in the ship, Captain, but we got it corked up."
     "How? And how big a hole?"

I told him and that is about all there was to it. They took a while to get to us because—I found this out afterward—they isolated that stretch of corridor first, with the air-tight doors, and that meant they had to get everybody out of the rooms on each side of us and across the passageway. But presently two men in space suits opened the door and chased all the kids out, all but me. Then they came back. One of them was Mr. Ortega. "You can get up now, kid," he said, his voice sounding strange and far away through his helmet. The other man squatted down and took over holding the pillow in place.

Mr. Ortega had a big metal patch under one arm. It had sticky padding on one side. I wanted to stay and watch him put it on but he chased me out and closed the door. The corridor outside was empty but I banged on the air-tight door and they let me through to where the rest were waiting. They wanted to know what was happening but I didn't have any news for them because I had been chased out.

After a while we started feeling light and Captain Harkness announced that spin would be off the ship for a short time. Mr. Ortega and the other man came back and went on up to the control room. Spin was off entirely soon after that and I got very sick. Captain Harkness kept the ship's speaker circuits cut in on his conversations with the men who had gone outside to repair the hole, but I didn't listen. I defy anybody to be interested in anything when he is drop sick.

Then spin came back on and everything was all right and we were allowed to go back into our bunkroom. It looked just the same except that there was a plate welded over the place where the meteorite had come in.

Breakfast was two hours late and we didn't have school that morning.

That was how I happened to go up to Captain's mast for the second time. George was there and Molly and Peggy and Dr. Archibald, the Scoutmaster of our deck, and all the fellows from my bunk room and all the ship's officers. The rest of the ship was cut in by visiplate. I wanted to wear my uniform but it was a mess—torn and covered with sticky stuff. I finally cut off the merit badges and put it in the ship's incinerator.

The First Officer shouted, "Captain's Mast for punishments and rewards!" Everybody sort of straightened up and Captain Harkness walked out and faced us. Dad shoved me forward.

The Captain looked at me. "William Lermer?" he said.

I said, "Yessir."

He said, "I will read from yesterday's log: 'On twenty-one August at oh-seven-oh-four system standard, while cruising in free fall according to plan, the ship was broached by a small meteorite. Safety interlocks worked satisfactorily and the punctured volume, compartment H-twelve, was isolated with no serious drop in pressure elsewhere in the ship.

"'Compartment H-twelve is a bunk room and was occupied at the time of the emergency by twenty passengers. One of the passengers, William J. Lermer, contrived a makeshift patch with materials at hand and succeeded in holding sufficient pressure for breathing until a repair party could take over.

"'His quick thinking and immediate action unquestionably saved the lives of all persons in compartment H-twelve.'"

The Captain looked up from the log and went on, "A certified copy of this entry, along with depositions of witnesses, will be sent to Interplanetary Red Cross with recommendation for appropriate action. Another copy will be furnished you. I have no way to reward you except to say that you have my heart-felt gratitude. I know that I speak not only for the officers but for all the passengers and most especially for the parents of your bunk mates."

     He paused and waggled a finger for me to come closer. He went on in a low voice, to me alone, "That really was a slick piece of work. You were on your toes. You have a right to feel proud."
     I said I guessed I had been lucky.
     He said, "Maybe. But that sort of luck comes to the man who is prepared for it."
     He waited a moment, then said, "Lermer, have you ever thought of putting in for space training?"
     I said I suppose I had but I hadn't thought about it very seriously. He said, "Well, Lermer, if you ever do decide to, let me know. You can reach me care of the Pilots' Association, Luna City."

From FARMER IN THE SKY by Robert Heinlein. 1950.
Emergency Space Suit

This section has been moved here

Blown Out The Airlock


(ed note: TL;DR: you get explosive decompression strong enough to suck a person across the room and out the hole only when the area of the hole is large relative to the cross-sectional area of the chamber. If the hole is tiny, like a bullet hole, you will only get the weak draft of a gentle decompression.

Understand that even with a tiny hole, if you get your body right up against it, the pressure will do its best to squeeze you out the hole like a tooth paste out of a tube.)

Recently, a discussion on ejecting people from airlocks or airplanes had inadequate math, and there's much confusion about the variables at play. It took a long time to work out the calculations correctly, but this post has the high-level intuition. I put all the gritty derivations and analysis notes in this addendum below.

Anyway, in the following, we have (constants):

"va" is the absolute velocity of the air (sonic, so ≈343.15 m s-¹)

Object (human) parameters:

"A" is your cross-sectional area: ≈0.7 m²
"C_D" is your drag coefficient (dimensionless): ≈1.2 (plausible: 1.0–1.3)
"m" is your mass: ≈65.57 kg (average: ≈61.14 kg female, ≈70.00 kg male)

Chamber parameters:

"h" is hole area (m²)
"H" is ratio of hole area to chamber cross-sectional area (dimensionless)
"ρ₀" is initial air density: ≈1.225 kg m-3
"T" is temperature: ≈293.15 °K (= 20 °C+273.15))
"V" is volume of chamber (m³)

(ed note: 1.225 kg m-3 is mathematical shorthand for 1.225 kg/m3 where the superscripted minus sign implies the division sign. In English it is pronounced "1.225 kilograms per cubic meter")

Derived/calculated quantities:

"f(t)" is force (N)
"M(t)" is mass of air remaining in chamber (kg)
"ρ(t)" is density of air at a given time (kg m-³). By definition, ρ(0)=ρ₀.
"v(t)" is your absolute velocity (initially 0 m s-¹)
"vr(t)=va-v(t)" is relative velocity of the air.

If you want to change these constants, or calculate yourself, the script I wrote is here:

SCENARIO 1: You're in a corridor. One end has an infinite supply of air; the other is fully exposed to vacuum at t = 0 s (hole has same area as cross-sectional area of chamber).

Applicable equations:

f(t) = m c (c t + va-¹)-², where c := (ρ₀ C_D A) (2 m)-¹
v(t) = (c va t) (c t + va-¹)-¹, where c is as above
a(t) = c (c t + va-¹)-², where c is as above

Values at t = 0 s (3 figures):

f(0) ≈ 60.6 kN
v(0) = 0.00 m s-¹
a(0) ≈ 924 m s-² ≈ 94.2 gravities

Values at t = 1 s (3 figures):

f(1) ≈ 4.44 kN
v(1) ≈ 250 m s-¹
a(1) ≈ 67.8 m s-² ≈ 6.91 gravities

Analysis: That's explosive decompression. In fact, it's in the regime where your peak acceleration into the great beyond might just kill you outright. Note that the acceleration is mostly over a few seconds, and that your speed asymptotically increases to va (that is, your ∆v tends toward va).

SCENARIO 2: You're in a corridor. One end has an infinite supply of air; the other is partially exposed to vacuum through a hole of h = 10 cm diameter (H = 0.25% of the area of a 2 m diameter corridor) at t = 0 s.

Applicable equations:

f(t) = m c (c t + (H va)-¹)-², where c := (ρ₀ C_D A) (2 m)-¹
v(t) = (c H va t) (c t + (H va)-¹)-¹, where c is as above
a(t) = c (c t + (H va)-¹)-², where c is as above

Values at t = 0 s (3 figures):

f(0) ≈ 0.379 N
v(0) = 0.00 m s-¹
a(0) ≈ 5.77 mm s-² ≈ 0.589 milli-gravities

Values at t = 1 s (3 figures):

f(1) ≈ 0.374 N
v(1) ≈ 5.74 mm s-¹
a(1) ≈ 5.70 mm s-² ≈ 0.581 milli-gravities

Analysis: Gentle decompression. Area scales quadratically, which can decrease the ratio H counterintuitively. Then, the force imparted by the outrushing air scales quadratically again (the -¹ with -² in the calculation of f(t)). Hence, small reductions in dimension result in high reduction in area, which results in an even higher reduction in force. Consequently, even fairly large holes can produce almost negligible pulls. Of course, if you got right up against the hole, the air pressure inside would act over your body instead (something like 796 N trying to slam you through that 10 cm hole).

SCENARIO 3: You're in an airlock, volume V = 30.0 m³ and 2 m in diameter. One end is fully exposed to vacuum at t = 0 s (hole has same area as cross-sectional area of chamber).

Applicable equations:

f(t) = m (c₁ exp(c₂ t)) ( (c₁/c₂) (exp(c₂ t) - 1) + va-¹ )-², where
c₁ := (ρ₀ C_D A) (2 m)-¹
c₂ := -h va / V
v(t) = va - ( (c₁/c₂) (exp(c₂ t) - 1) + va-¹ )-¹, where c₁ and c₂ are as above
a(t) = (c₁ exp(c₂ t)) ( (c₁/c₂) (exp(c₂ t) - 1) + va-¹ )-², where c₁ and c₂ are as above
M(t) = V ρ₀ exp(c₂ t), where c₂ is as above
ρ(t) = ρ₀ exp(c₂ t), where c₂ is as above
∆v = va - ( 1/va - a/b )-¹, where c is as above

Values at t = 0 s (3 figures):

f(0) ≈ 60.6 kN
v(0) = 0.00 m s-¹
a(0) ≈ 924 m s-² ≈ 94.2 gravities
M(0) ≈ 36.8 kg
ρ(0) ≈ 1.23 kg m-³

Values at t = 1 s (3 figures):

f(1) ≈ 1.30e-11 N
v(1) ≈ 23.9 m s-¹
a(1) ≈ 1.98e-13 m s-² ≈ 2.02e-14 gravities
M(1) ≈ 9.10e-15 kg
ρ(1) ≈ 3.03e-16 kg m-³

Analysis: Initial conditions are the same as in scenario 1 (as makes sense), but as the precious, life-giving air rushes away to oblivion, the force and density rapidly decrease. Therefore, the acceleration quickly drops to zero. Total ∆v is ≈23.9 m s-¹, which is 50% achieved in the first 18.3 ms, 90% achieved in the first 62.2 ms, and 99% achieved in the first 126 ms. This is still explosive decompression, but the initial jolt is basically a tenth of a second, which you might conceivably survive. Note that your final velocity is much slower than va.

SCENARIO 4: You're in an airlock, volume V = 30.0 m³ and 2 m in diameter. One end is partially exposed to vacuum through a hole of h = 10 cm diameter (H = 0.25%) at t = 0 s.

Applicable equations:

f(t) = m (c₁ exp(c₂ t)) ( (c₁/c₂) (exp(c₂ t) - 1) + (H va)-¹ )-², where
c₁ := (ρ₀ C_D A) (2 m)-¹
c₂ := -h va / V
v(t) = H va - ( (c₁/c₂) (exp(c₂ t) - 1) + (H va)-¹ )-¹, where c₁ and c₂ are as above
a(t) = (c₁ exp(c₂ t)) ( (c₁/c₂) (exp(c₂ t) - 1) + (H va)-¹ )-², where c₁ and c₂ are as above
M(t) = V ρ₀ exp(c₂ t), where c₂ is as above
ρ(t) = ρ₀ exp(c₂ t), where c₂ is as above
∆v = H va - ( 1/(H va) - a/b )-¹, where c is as above

Values at t = 0 s (3 figures):

f(0) ≈ 0.379 N
v(0) = 0.00 m s-¹
a(0) ≈ 5.77 mm s-² ≈ 0.589 milli-gravities
M(0) ≈ 36.8 kg
ρ(0) ≈ 1.23 kg m-³

Values at t = 1 s (3 figures):

f(1) ≈ 0.342 N
v(1) ≈ 5.49 mm s-¹
a(1) ≈ 5.21 mm s-² ≈ 0.531 milli-gravities
M(1) ≈ 33.6 kg
ρ(1) ≈ 1.12 kg m-³

Analysis: Gentle decompression. Again, quadratic scaling can be counterintuitive. In the first second, 3.18 kg of air blasts out, but over the whole room, this produces only a weak draft. Total ∆v is ≈5.98 cm s-¹.

SCENARIO 5: You're in an airplane, when a huge section of the roof rips off.

Analysis: Two important things to notice: (1) The hole is large relative to the volume of the chamber (cabin). As the previous scenarios might have hinted, this is therefore an explosive decompression event. (2) The low-pressure, but still high-velocity, wind is blasted into the cabin. This combines with the rapid pressure drop to throw things out of the airplane. No hard numbers, but I'd estimate that either force would be sufficient to do this alone.

SCENARIO 6: You're in an airplane, when a small hole gets punched in the side somehow.

Analysis: The hole is small relative to the cabin volume. This is therefore not an explosive decompression event. This was also apparently confirmed experimentally by Mythbusters (eps. 10 and 38).


Explosive decompression is real, but it requires the area of the hole to be large relative to the volume of the chamber. Even apparently large holes (like, size of your opened hand (10 cm)) won't explosively decompress a typical room. The equations given above should be reasonably accurate, assuming I didn't screw up copying them from my notes and program. You can check the math itself (here and again use the program (here:


A lot of computations and math went into my explosive decompression article above, and yet it is only essentially a high-level presentation of the equations and some example numbers. Here, I'll elaborate on the equations and the assumptions made in deriving them. For symbols used, please refer to the parent article.

The equation everything I did is based on is the drag equation:

f(t) = ½ ρ(t) vr(t)² C_D A

There are extremely complex adjustments that people use in industry to improve on this, but to really do fundamentally better, we'd need to write an actual fluid simulator. I've done this, mind you, and it's no fun—especially for trans-/hyper-sonic flows. You'd also have to run simulations and interpret them. Happily, all that is overkill. The drag equation works well at high fluid velocities (such as we have here) and gives plausible answers for the general cases under consideration.

The main practical limitation of this analysis is that additional effects (mainly compressibility, adiabatic changes, and temperature) are not considered. They'd only matter in scenarios 3 and 4, and in these cases the air rushes out so quickly, and the accelerations are so much greater in the initial part of the calculation where such corrections are zero, that I don't think they matter. Moreover, engineering texts are frankly so badly written as to be incomprehensible on this point, and resolving that by going for a BS in MechEng is overkill just for solving a stupid thought experiment on the Internet.

The next key fact is that flow is "sonic" (that is, va = Mach 1). Intuitively, this is because air molecules can only flow into a vacuum as fast as they can "find out" about it. This happens at the speed of sound, because air molecules bump into each other (or don't, because they've escaped to vacuum), and this is how sound is transmitted. For more discussion, see e.g. my discussion on cold gas thrusters.

For scenario 1, we simply use Newton's Second Law to find a(t) from the drag equation. Since the source has an infinite supply of air and the outward flow is sonic (which means that, by definition, information about pressure cannot propagate "upstream"), the density in the chamber

p(t) is a constant ρ₀=ρ(0):
a(t) = ½ ρ₀ vr(t)² C_D A / m

From here, we try to integrate to get v(t). However, we run into a problem, because vr(t) itself depends on v(t). So this is a recursive integral. But happily, we can just differentiate the whole mess to get the Riccati differential equation:

d/dt v(t) = c (va - v(t))², where c := (ρ₀ C_D A) (2 m)-¹

Which has a simple solution (use v(0)=0):

v(t) = (c va t) (c t + va-¹)-¹, where c is as above

Which is the formula I presented. To get the other equations, you differentiate to get a(t), and then scale by m to get f(t) (because Newton's Second, again).

For scenario 2, we assume the air is pulled evenly out the hole (so if the air is flowing out the hole at va = 343.15 m s-¹, then if the room has a cross section 100 times bigger, the air flows through the room at H va = 3.4315 m s-¹). In the Riccardi equation, this basically multiplying vₐ by H, and then working through again.

For scenario 3, we're considering the diminishing effects of the reducing pressure in the chamber. I found inspiring. Unfortunately, their use of Bernoulli's Law is erroneous; they assume density is constant, but it isn't. In any case, the result is greater than Mach 1 for reasonable values, which is not possible. The volumetric flow rate should instead be calculated as:

d/dt M(t) = -ρ(t) h va

This can be integrated to get the mass of air in the chamber M(t), and therefore the density in the chamber ρ(t):

M(t) = V ρ₀ exp(c₂ t), where c₂ := -h va / V
ρ(t) = ρ₀ exp(c₂ t), where c₂ is as above

Then, we simply redo the same analysis we did for scenario 1, but without the assumption that ρ(t)=ρ₀. The Riccardi obtained is:

d/dt v(t) = c₁ exp(c₂ t) (va - v(t))², where
c₁ := (ρ₀ C_D A) (2 m)-¹
c₂ := -h va / V

Because I'm lazy, I tried solving this with WolframAlpha. Yet, the result it gave back was strange, and the c₁s end up canceling (I knew at once that this was very wrong, since c₁ is how we know about our mass m). AFAICT WolframAlpha is just wrong, and I wasted a lot of time verifying that and the previous steps of the derivation. Anyway, the equation is separable, so it's nearly as easy to solve by hand:

v(t) = va - ( (c₁/c₂) (exp(c₂ t) - 1) + va-¹ )-¹, where c₁ and c₂ are as above

You calculate a(t) and f(t) as before. To get the ∆v, you simply take the limit of v(t) as t -> ∞.

Scenario 4 is to scenario 3 similarly as scenario 2 was to scenario 1. Here, the differential equation for M(t) is unchanged, because it is already parametrized on the hole area. Hence, M(t) and ρ(t) are identical forms to in scenario 3 (though you of course get different values because h is smaller). The first change is in the Riccardi equation, where we need to multiply va by H in the final term, yielding a final v(t) of:

v(t) = H va - ( (c₁/c₂) (exp(c₂ t) - 1) + (H va)-¹ )-¹, where c₁ and c₂ are as in scenario 3

Note that c₂ does not have the scaling by H, but the other terms in v(t) do.

Scenarios 5 and 6 are just extrapolations and generalizations of the previous four.

If you'd like to tweak the numbers, or you don't want to enter in all this garbage into your calculator, the Python script I used for this analysis can be found here:


(ed note: this more or less comes to the same conclusion as Ian Mallett's analysis above)

Brian Davis

This came up in a different newsgroup, and upon trying to answer it I blew it badly. I’m not sure the original group really cares, but folks here might, and it’s kind of interesting to me, so…

Let’s say you have a person (named, let’s say, “Callie”) standing in the middle of a large airlock (10 [m] long by 3[m] by 3[m]). The bad girl opens the large doors at the end, “blowing the lock” (it starts at 1 [Atm]). What happens to the helpless heroine? I understand decompression, but I’m trying to figure out how fast (if at all) they “exit” the airlock. For a first cut, I assumed the doors instantly crack open 10 [cm] along their entire 3 [m] length, forming a “breach” with an area of 0.3 [m2] through which the air starts rushing at roughly Mach 1 (I know it would be less, but ballpark). Back by Callie, the cross-sectional area is about 9 [m2], so conservation of mass (assuming uniform density) says the airspeed by her is a gusty 11.1 [m/s]… which is pretty much trivial. I assumed she is accelerated “breachward” by the stagnation pressure of this flow against the front of her body (frontal surface area 0.36 [m2, mass of 45 [kg]), but the result is a really trivial acceleration. Running it through Excel (to keep track of the rapid density/pressure drop, which reduces the stagnation pressure all the more), I get her hitting the breach after a little over 8.5 [sec], and the leisurely pace of about 0.67 [m/s] (a slow walk). She really only accelerates for the first couple seconds, after that the lock is at such a low pressure that the remaining “wind” just doesn’t have enough force to do anything.

OK, so what did I screw up? I realize approximating the exit velocity as 333 [m/s] isn’t good, and I’m ignoring the question of adiabatic vs. nonadiabatic effects, etc. I do take into account the increased airspeed as she gets very close to the breach (closer than 2 [m] or so). But anything major? Or does Callie really fully decompress in the airlock, and gently drift out about 10 seconds later? One interesting artifact of my calculation is that Callie takes a sharp jump up in velocity during the brief time she “wedges” in the breach, but I’m not as worried about that because in the real situation, the doors would have been fully opened by then.

PS- I’d love to take the rate of the doors opening (i.e., breach area increasing) into account, but it makes things more difficult, and in particular makes the assumption of sonicly-limited flow questionable (if the “breach” is one entire side of your airlock, I think I have to worry about the force required to accelerate the mass of air in addition to everything else, yes?).

(in Robert Heinlein's Starman Jones they have to do burial in space. They pressurize the airlock to ten atmospheres in order to have enough pressure to blow the body out the airlock)

John Park

I haven't verified your numbers, but for a quick sanity check, there's about 100 kg of air in the lock, but only half of that is behind her—her own body weight—and most of that will escape past her. If you really want the damsel to experience dramatic accelerations, I think you should start her closer to the opening, or have the inner door open, or maybe use a longer, thinner lock that she almost blocks with her body.

Tim Little

(Brian Davis: She really only accelerates for the first couple seconds, after that the lock is at such a low pressure that the remaining 'wind' just doesn't have enough force to do anything.)

Yes, that's about right, if the door opens outward and sticks at a 10 cm gap. Though actually I'd be very surprised to see an airlock with a door that opened outward at all.

If it did open outward, and was free to swing open wider, consider that it has 100 kPa pressure acting on the inner surface. It will accelerate open very rapidly indeed — probably on the order of tens of milliseconds.

Though even in that situation, I'd guess Callie would exit the airlock with only on the order of 1-3 m/s velocity, long after the air is gone.

(Brian Davis: Or does Callie really fully decompress in the airlock, and gently drift out about 10 seconds later?)


(Brian Davis: if the breach is one entire side of your airlock, I think I have to worry about the force required to accelerate the mass of air in addition to everything else, yes?)

Sort of. The rarefaction front will propagate inward at the speed of sound, with the air accelerated nearly instantaneously as the front passes. The temperature behind the front will be some fraction of the starting temperature — I'd guess about 4/5 from one thermal degree of freedom out of five being converted to kinetic energy.

The relation for adiabatic expansion then gives a pressure behind the front of about 46% of the initial pressure, and an exit speed of about 250 m/s.

That will exert a lot of force on Callie, but only for about 20-30 ms.

Dr J. R. Stockton

(Brian Davis: Let’s say you have a person (named, let’s say, “Callie”) standing in the middle of a large airlock (10 [m] long by 3[m] by 3[m]). The bad girl opens the large doors at the end, “blowing the lock” (it starts at 1 [Atm]). What happens to the helpless heroine?)

At worst, approximately, and assuming a heroine of only moderate size (i.e., not a plug) : since the molecular speed is about the speed of sound, the energy can only accelerate the gas to about the speed of sound, 330 m/s. The heroine, being around a thousand times more dense than air, will be accelerated to about a thousandth of that, around a foot per second.

A worst case approximation is that a transition between 105 Pa and 0 Pa propagates past her at 330 m/s. So, per square metre, she gets 105 N for a duration of T/330 s, where T is her thickness in metres. Her mean density will be, of course, 1000 in SI units, so per square metre her mass is 1000×T; so her change in speed will be 105 × T/330 / 1000×T, which is about 0.3 m/s.

One cannot recommend, for the usual purposes, a heroine who obstructs a substantial proportion of nine square metres.

Tim Little

(Dr J R Stockton: A worst case approximation is that a transition between 105 Pa and 0 Pa propagates past her at 330 m/s. So, per square metre, she gets 105 N for a duration of T/330 s, where T is her thickness in metres.)

The duration is much longer than that, since she is still in the path of the air escaping from further back in the airlock. Even though the static pressure is at 0 Pa, it still has significant density.

In particular, if c is the usual speed of sound, and v is the speed to which the rarefaction wave accelerates the air, simple conservation of mass puts the density ratio at c/(c+v).

So the air rushing past her from further in the airlock will exert pressure as it escapes past her. So for a long airlock, her velocity would asymptotically approach the free outflow speed.

This is a fairly short airlock, but certainly longer than her average thickness.

John Schilling

(Dr J R Stockton: At worst, approximately, and assuming a heroine of only moderate size (i.e. not a plug) : since the molecular speed is about the speed of sound, the energy can only accelerate the gas to about the speed of sound, 330 m/s. The heroine, being around a thousand times more dense than air, will be accelerated to about a thousandth of that, around a foot per second.

A worst case approximation is that a transition between 105 Pa and 0 Pa propagates past her at 330 m/s. So, per square metre, she gets 105 N for a duration of T/330 s, where T is her thickness in metres. Her mean density will be, of course, 1000 in SI units, so per square metre her mass is 1000×T; so her change in speed will be 105 × T/330 / 1000×T, which is about 0.3 m/s.)

Ah, so if I hang a sheet of tissue paper just inside the airlock of an O'Neill habitat, and open the door, it won't go anywhere, right? Because all it will experience is an infinitesimal moment of acceleration as the transition between atmosphere and vacuum propagates past its negligible thickness?

I'm thinking that's not right. I'm also thinking that a propagating transition between atmosphere and vacuum would represent a violation of the law of conservation of mass.

What actually propagates, is a transition between air at 105 Pa, and air at 5.28×104 Pa moving outwards at 310.42 m/s. And that transonic wind condition, remains even after the transition has passed — for as long as it takes for the transition wave to reach the farthest wall of the chamber behind our heroine, and as long beyond that as it takes for the wind to actually empty the chamber.

If the geometry is cylindrical, I get for a standard heroine in a standard atmosphere, a net velocity of 1.8 m/s per meter length of air-filled volume behind her. That's in the low-velocity limit; as she herself approaches transonic velocity downstream, the force will decrease and her own velocity will asymptotically approach 310.42 m/s.

If the geometry is not cylindrical, it gets rather more complicated of course.

Erik Max Francis

(Brian Davis: OK, so what did I screw up?)

Nothing, I'd say. The ability for explosive decompression to push people around is usually exaggerated. Your results sound qualitatively like I'd expect — it'd budge her a little at first but very rapidly the ambient air pressure would drop to the point that it wouldn't have much of an effect.

Russell Wallace

That's interesting, because it appears to conflict with the usual description of explosive decompression on aircraft: even a fairly small hole in e.g., an airliner at altitude, will cause everything that isn't nailed down — including people who aren't strapped into their seats — to be quickly sucked out the hole. Is that description simply inaccurate, or is there a difference in the cases that I'm missing?

Wayne Throop

It's inaccurate. I seem to recall there was a Mythbusters that concluded "busted".

Tim Little

(Russell Wallace: an airliner at altitude, will cause everything that isn't nailed down — including people who aren't strapped into their seats — to be quickly sucked out the hole. Is that description simply inaccurate, or is there a difference in the cases that I'm missing?)

It is simply inaccurate. Yes, decompression is dangerous, and if a significant hole opens up the winds can be extreme. But they're not caused by the decompression!

It should be noted that an airliner at altitude is usually moving at a significant fraction of the speed of sound through the air. The air doesn't just simply leave as it would in a vacuum, or if it were a zeppelin cabin.

From the point of view of the aircraft, the air outside has kinetic energy greater than any hurricane. If a large hole opens up, part of that can get in.

Erik Max Francis

It depends on how much air is in the vessel, how big the hole is, and how close the victim is to the breach. Sure, there are some cases where the victim will likely be forced out of the breach. But probably not in the case Brian was talking about. Not that really helps her chances, since she's exposed to vacuum with no way to get back in.

Michael Ash

The image of everything that's not nailed down flying out the door may be inaccurate, but the earlier estimate of 0.3m/s would appear to be inaccurate as well. Perhaps the most famous explosive decompression incident is Aloha Airlines 243 which suddenly lost a large section of skin but managed to land safely. One flight attendant was thrown to the floor and another one was thrown out of the plane altogether, never to be seen again. A 737 isn't particularly large but it would require substantially more imparted velocity than that to throw somebody out. A spacecraft pressurized to 1 atmosphere should be a bit worse as well, since the accident in question occurred at 24,000ft where the outside air pressure is still about 0.4 atmospheres.

It should be noted that a small hole doesn't do this, because a small hole doesn't result in explosive decompression in the first place. A small hole will leak, not cause a bang, and there would just be some wind. Thus the fears of instant death due to a gunfight piercing the hull are completely overblown, and I believe this is what Mythbusters investigated. But this is an entirely different scenario from opening a large airlock door or the case of the poor Aloha Airlines flight attendant.

Wayne Throop

Sure, but that's what being exposed to 300+mph winds will get you. Just the decompression, not so much. It's the fact that so much of the hull was peeled away.

The Mythbusters bit (iirc) was concerned with two aspects of a fairly small hole. First, will it suck everything inside towards it, and second, will it rip the hull open and expose the interior to the airstream (that is, will any small break in the skin necessarily spread very far). And they concluded, no and no. Of course, they were talking about a bullethole (again iirc). But I doubt things would be much different for anybody at a reasonable distance from, say, a hatch-sized hole. An upper-half-of-the-hull-peels-away-in-a-section-tens-of-feet-long sized hole is another matter entirely, and I doubt anybody will notice the decompression, given the brisk breeze outside.

Robert Martinu

(Wayne Throop: And they concluded, no and no. Of course, they were talking about a bullethole (again iirc). But I doubt things would be much different for anybody at a reasonable distance from, say, a hatch-sized hole.)

Later the episode they tested what a moderate amount of explosives would do to the pressurized hull. The result was iirc a seat cusion sucked out, but the dummy still in its seat. Again its not the decompression you have to fear.

From Explosive decompression - how fast? thread in 4/26/2008


NASA assumes that each astronaut consumes per day 0.617 kilograms of dry food and 3.909 kilograms of potable water (some mixed in with the food). Astronauts also use 26 kilograms of water per day for personal hygiene.

NASA also assumes that each astronaut excretes 4.254 kg of water per day due to various metabolic processes. For details see below. Some of this water can be reclaimed.

Ken Burnsides and Eric Henry figured that each person has a reserve of 10 liters of water, and requires somewhere between 0.1 and 0.25 liters of water per day to make up for reclamation losses. (Eric used 0.1, Ken used 0.25 mostly due to having worked in a sewage treatment plant)

In the TransHab design, they use a water management subsystem to recover potable water from waste water.

In the following specifications, the mass (kg), volume (m3), and electrical power requirements (W) is for equipment sized to handle a six person crew.

An aluminum potable water storage tank (145.9 kg, 0.54 m3, 5 W) initially contains a three day supply of water for the six crew members. Waste water is sent through a Vapor Phase Catalytic Ammonia Removal (VPCAR) system (1119 kg, 5.5 m3, 6090.7 W). The VPCAR process is a wastewater treatment technology that combines distillation with high-temperature catalytic oxidation of volatile impurities such as ammonia and organic compounds.

The report mentioned that the VPCAR system was selected over a rival system since it had a lower mass, volume, and turnaround time. The VPCAR's drawback was the larger power requirements.

Of course there is the problem of recycling disgust, but that has to be fixed by psychologists, not engineers.


NASA assumes that each astronaut consumes per day 0.617 kilograms of dry food and 3.909 kilograms of potable water.

The food is to have an energy content of 11.82 MJ per astronaut per day, about 2,800 food calories. More precisely:

FemaleAstronautDailyCalories = 655 + (9.6 × W) + (1.7 × H) - (4.7 × A)

MaleAstronautDailyCalories = 66 + (13.7 × W) + (5 × H) - (6.8 × A)


  • W = weight (kg)
  • H = height (cm)
  • A = age (years)

NASA has a variety of space foods. Preparing food for prolonged space missions is always a challenge. Cooking food from raw ingredients is even more of a challenge. NASA space food is preprepared, more like heat-and-serve than it is like cooking beef bourguignon from scratch.

See the page Closed Ecological Life Support System.

The always worth reading Future War Stories has a good article on Military Field Rations and Space Food.

For food, Eric and Ken ran numbers from the USS Wyoming.

TL;DR: 1 person-day of food is 2.3 kg and 0.0058 m3, food storage space is about 0.012 m3. Food supply is 29% frozen, 57% dry, 14% fresh. If you are not interested in how these numbers were derived, skip to the next section.

150 man crew, 90 day cruise (13,500 person-days), 31,500 kg of food (9,000 kg frozen, 18,000 kg dry, 4,500 kg fresh). This is about 2.3 kg of food per man per day.

Frozen meat has a density of about 0.35 kg/liter (which Ken determined experimentally with a kilo of frozen meat in a 2 liter pitcher in his sink). Frozen veggies were less (0.4 kg/liter), so split the difference and use 0.375 kg/liter. 9,000 kg takes up 24,000 liters (24 m3).

Fresh foods have a density of roughly 0.25 kg/liter, due to air packed around the food by the packaging. 4,500 kg takes up 18,000 liters (18 m3).

Dry and canned goods range from densities of 0.25 kg/liter for flour and bread and 1.0 kg/liters for canned goods. Split the difference and use 0.5 kg/liter. 18,000 kilos takes up 36,000 liters (36 m3).

Total volume is 78,000 liters, or 78 cubic meters of food (1000 liters = 1 m3). Assume that we're off on our calculations and round up to 80 m3 as a reserve.

Storage, including refrigeration wastage is usually three times the space, but the Navy has a tradition of doing things in amazingly tight quarters. So we will merely double it, for 160 m3 to store our food.

Add about 13,500 liters of water (1 liter of water per person-day, for 150 crew and 90 days or 13,500 person-days) which of course masses 13,500 kg (actually that's pretty spartan. NASA recommends 3.09 liters per man per day. And it is prudent to add a reserve).

Add about 3,500 liters of compressed air (0.2 liters per person per day for 90 days, plus a reserve for general pressurization and a 20% safety margin) which masses 1050 kg.

Together air and water add about 17 m3.

There are alternate figures on life support in this document. It specifies the daily requirements of consumables per person as: 0.83 kg Oxygen, 0.62 kg freeze dried food (which would increase to 2.48 kg when the water was added), 3.56 kg water for drinking and food preparation, and 26.0 kg water for hygiene, flushing, laundry, dishes, and related matters. Note that the value for hygiene water is somewhat dependent on technology — if you have sonic showers and the like the requirements may be less.

William Seney notes that the NC State document specify oxygen consumption figures differ considerably from Eric and Ken's estimate. If we assume their value should be 48L per HOUR instead of per DAY (1.38 kg / day) it is much closer.

When the body uses glucose the reaction is:

C6H12O6 + 6 O2 => 6 CO2 + 6 H2O

so a slight excess of water is produced. According to the NC State document this works out to about 0.39L per person per day, which may be enough to replace losses.


      There was no space to spare in space. Every cubic centimeter inside the hull must work. Yet persons intelligent and sensitive enough to adventure out here would have gone crazy in a “functional” environment. Thus far the bulkheads were bare metal and plastic. But the artistically talented had plans. Reymont noticed Emma Glassgold, molecular biologist, in a corridor, sketching out a mural that would show forest around a sunlit lake. And from the start, the residential and recreational decks were covered with a material green and springy as grass.

     The air gusting from the ventilators was more than purified by the plants of the hydroponic section and the colloids of the Darrell balancer. It went through changes of temperature, ionization, odor. At present it smelted like fresh clover — with an appetizing whiff added if you passed the galley, since gourmet food compensates for many deprivations.

From TAU ZERO by Poul Anderson (1970)

Eeking Out

For a real Spartan bare-minimum cruise, you can probably use a figure of one m3 per person per day. But this would not be recommended for a cruise of longer than 20 to 30 days. Morale will suffer. And don't even think about feeding your crew food pills.

The bare-minimum of consumables mass looks like 0.98 kg water, 2.3 kg food, and 0.0576 kg air per person per day. About 3.3 kg total, round it up to 4. People actually need 2.72 kg of water, but since food is 75% water, it contains an additional 1.72 kgs.

Our 90 day cruise now has about 165 m3 of bare essentials. Put in niceties like better cooking gear, spare clothing, toilet paper, video games, soda, luxury goods, and you are probably getting close to 240 m3. That will fit in a sphere 8 meters in diameter (about 25 feet).

If the spacecraft has no artificial gravity, you'd better include lots of spices and hot sauce. As the body's internal fluids change their balance, crewmembers will get the equivalent of stuffy noses. This will decrease the sense of taste. Food will taste bland like it does when you have a head cold, and for the same reason.

You'll need more space if you want to include hydroponics for fresh veggies. Roughly 800 liters of hydroponics per person per 'green meal' per week. This also helps CO2 scrubbing and crew morale. About 20 m3 per 25 men, or 120 m3 for our 150 man crew. 3 green meals per week takes about 600 m3.

Pre-Packaged Meals

On NASA shuttle and ISS missions, the astronauts have conventional knives, forks, and spoons; a hot/cold water injector, a warming oven, and scissor to cut open plastic seals. Because food on NASA vessels is more like heating premade TV dinners than it is cooking a recipe from scratch.

When the water injector is set to "hot water" the temperature is between 68° and 74° C. The injector can be set to dispense water in one-half ounce increments up to 8 ounces.

Dehydrated food containers have a "septum adapter", i.e., a little airlock to insert the water injector nozzle. Otherwise when you removed the water injector the container would become a water weenie and drench you. For beverages you would then insert into the septum adapter a drinking straw. The straw has a built-in clamp to prevent the drink from spraying all over your face when you take the straw out of your mouth. For foods you wait until it rehydrates, then use the scissors to cut the container open. You make an X-shaped cut, creating four large flaps to help keep the food from escaping (a "spoon-bowl" package).

The warming oven is a forced air convection oven with internal hot plate. Its tepid internal temperature is from 71° to 77° C (170° F) because NASA is paranoid about the astronauts burning themselves. It can hold up to 14 food containers at a time: rehydratable packages, thermostabilized pouches or beverage packages.

NASA's space shuttle used fuel cells for power, which create plenty of water usable to rehydrate food. The shuttle meals were mostly dehydrated to save on mass.

The International Space Station on the other hand uses solar panel for power, which do not produce water. While there is some water available from recycling there is not enough for rehydrating food (there is barely enough for powdered drinks). Therefore the ISS uses no dehydrated food, instead is uses frozen and thermostabilized food which already has the water in it.

You can thank Napoleon Bonaparte for the invention of thermostabilized food in foil containers.

Back in the 1800's, it was tough to get food to armies on the move (the age-old problem of Logistics). An army would have to split up and spread out in order to ransack all the villages and farms in the area for food. Napoleon almost lost the war and his life at the Battle of Marengo because of this. While his army was split up, Napoleon's small army segment got ambushed by the entire Austrian army. If the other French groups had not returned in time, Napoleon might not have even been mentioned in the history books.

Determined not to get caught like that again, Napoleon offered a reward of 12,000 francs to the inventor who could preserve food for army rations in large quantities. The prize was won by Nicolas Appert, who basically invented thermostabilizing (your grandmother calls it "home canning" using Mason jars). He had stumbled upon Louis Pasteur's pasteurization process 50 years before Pasteur. The press went wild, waxing poetically on how Appert had established the art of fixing the seasons, so seasonal foods could be enjoyed year round. The French army was pleased as well.

Appert used glass bottles to hold the food. A short time later, Peter Durand figured out how to thermostabilize food inside tin-plated cans. A couple of decades later artists figured out how to make their studios portable by storing their oil paints in tin tubes. Decades later NASA stored thermostabilized foods inside tin tubes for the Mercury mission (but later abandoned them because the mass of the tube was more than the mass of the food it held). Currently NASA supplies thermostabilized food inside foil pouches for the astronauts of the International Space Station.

NASA packages food in single-service disposable containers to avoid the ugly payload mass requirements of a dishwasher. Eating utensils and food trays are cleaned at the hygiene station with premoistened towelettes.

The containers are in one of five standardized dimensions so they will fit the holes in the "dinner table" and the slots in the oven. All five sizes have the same width. They often have build-in velcro pads on the bottom.

Non-Crumby Food

In free-fall, you want food that is as crumbless as possible. Under gravity the crumbs drop into the plate, the table, or the floor. In free-fall the blasted stuff floats everywhere: jamming machinery, shorting out electronics, and clogging up the Lost-and-Found department. No toast for the poor crew, examine the bottom of your toaster and you'll see why.

The same goes for larger pieces of food. You do not want your steak to take flight from your plate and go sailing across the habitat module. There was an impractical suggestion of some sort of suction plate with spikes to immobilize your steak.

Hard-shell tacos are forbidden. One bite and those things will shatter like a bagfull of tortilla chips hit by a brick. Taco shrapnel everywhere. Flaky pastry is a bad idea as well.

Fluids are a challenge, especially if they are hot (coffee or soup). Special drinking containers will be used.


On a Friday while the ship crossed the Wolf 359 system, Captain Thorne invited the ship’s junior officers to dinner. Some of Neil’s older colleagues commented it was about time; most captains had their officers to dinner within the first three or four days of a cruise. But Thorne was not a social captain, and Neil had the feeling the invitation was distinctly pro forma.

It was a surprise, then, to find Donovan and Rafe Sato in attendance. Neil saw Donovan daily, but Sato only rarely. Neil had the feeling Donovan’s technical aide didn’t like him very much; in any event, the NSS officer spent a lot of free time down in the enlisted women’s area.

The meal was stuffed burritos; they and their foreign equivalents were popular with cooks in space, because biting into a wrapped tortilla in freefall didn’t send little pieces of food flying in all directions, as it would with a sandwich. Still, Neil found a way, and he watched a small cube of diced tomato spin toward the ceiling, where it was caught in an air current and pushed slowly toward a ventilation grate.

From THROUGH STRUGGLE, THE STARS by John Lumpkin (2011)

      They snaked their way through endless passages, by guide line across compartment after compartment, through hatches, around corners. Matt was quite lost. Presently the man just head of him stopped. Matt closed in and found the squad gathered just inside another compartment. "Soup's on," announced Lopez. "This is your messroom. Lunch in a few minutes."
     Behind Lopez, secured firmly to the far wall, were mess tables and benches. The table tops faced Matt—under him, over him, or across from him—what you will. It seemed an impractical arrangement. "I'm not very hungry," one youngster said faintly.
     "You ought to be," Lopez answered reasonably. "It's been five hours or more since you had breakfast. We're on the same time schedule here as Hayworth Hall, zone plus eight, Terra. Why aren't you hungry?"
     "Uh, I don't know, sir. I'm just not."
     Lopez grinned and suddenly looked as young as his charges. "I was just pulling your leg, kiddo. The chief engineer will have some spin on us in no time, as soon as we break loose from the Bolivar. Then you can sit down on your soft, round fanny and console your tender stomach in peace. You'll have an appetite. In the meantime, take it easy."

     Very slowly they drifted against a side wall, bumped against it, and started sliding slowly toward the outboard wall, the one to which the mess tables were fastened. By the time they reached it there was enough spin on the ship to enable them to stand up and the mess tables now assumed their proper relationship, upright on the floor, while the hatch through which they had lately floated was a hole in the ceiling above.
     Matt found that there was no sensation of dizziness; the effect was purely one of increasing weight. He still felt light, but he weighed enough to sit down at a mess table and stay in contact with his seat; minute by minute, imperceptibly, he grew heavier.

     He looked over his place at the table, seeking controls that would permit him to order his meal. There were clips and locking holes which he guessed were intended for use in free flight, but nothing else.
     "Over there" was a door which concealed a delivery conveyor. Cadets from other tables were gathering around it. The two cadets designated as waiters went over and returned shortly with a large metal rack containing twenty rations, each packed in its service platter and still steaming hot. Clipped to each were knife, fork, and spoons—and sipping tubes.
     Matt found that the solid foods were covered by lids that snapped back over the food unless clipped up out of the way, while the liquids were in covered containers fitted with valves through which sipping tubes might be slipped. He had never before seen table utensils adapted for free-fall conditions in space. They delighted him, even though Earth-side equipment would have served as long as the ship was under spin.
     Lunch was hot roast beef sandwiches with potatoes, green salad, lime sherbert, and tea. Twenty minutes later the metal tray in front of Matt was polished almost as well as the sterilizer would achieve. He sat back, feeling that the Patrol was a good outfit and the Randolph a fine place to be.

From SPACE CADET by Robert Heinlein (1948)

Meanwhile, it was time to eat, though he did not feel particularly hungry. One used little physical energy in space, and it was easy to forget about food. Easy — and dangerous; for when an emergency arose, you might not have the reserves needed to deal with it.

He broke open the first of the meal packets, and inspected it without enthusiasm. The name on the label — SPACETASTIES — was enough to put him off. And he had grave doubts about the promise printed underneath: “Guaranteed crumbless.” It had been said that crumbs were a greater danger to space vehicles than meteorites; they could drift into the most unlikely places, causing short circuits, blocking vital jets, and getting into instruments that were supposed to be hermetically sealed.

Still, the liverwurst went down pleasantly enough; so did the chocolate and the pineapple puree. The plastic coffee bulb was warming on the electric heater when the outside world broke in upon his solitude, as the radio operator on the Commodore’s launch routed a call to him.

From THE WIND FROM THE SUN by Sir Arthur C. Clarke (1964)

In the galley the girls set about making dainty sandwiches, but the going was very hard indeed. Margaret was particularly inept. Slices of bread went one way, bits of butter another, ham and sausage in several others. She seized two trays and tried to trap the escaping food between them — but in the attempt she released her hold and floated helplessly into the air.

'Oh, Dot, what'll we do anyway?' she wailed. 'Everything wants to fly all over the place!'

'I don't quite know — I wish we had a bird-cage, so we could reach in and grab anything before it could escape. We'd better tie everything down, I guess, and let everybody come in and cut off a chunk of anything they want. But what I'm wondering about is drinking. I'm simply dying of thirst and I'm afraid to open this bottle.' She had a bottle of ginger ale clutched in her left hand, an opener in her right; one leg was hooked around a vertical rail. 'I'm afraid it'll go into a million drops and Dick says if you breathe them in you're apt to choke to death.'

'Seaton was right — as usual.' Dorothy whirled around. DuQuesne was surveying the room, a glint of amusement in his one sound eye. 'I wouldn't recommend playing with charged drinks while weightless. Just a minute — I'll get the net.'

He got it; and while he was deftly clearing the air of floating items of food he went on. 'Charged stuff could be murderous unless you're wearing a mask. Plain liquids you can drink through a straw after you learn how. Your swallowing has got to be conscious, and all muscular with no gravity. But what I came here for was to tell you I'm ready to put on one G of acceleration so we'll have normal gravity. I'll put it on easy, but watch it'

'What a heavenly relief!' Margaret cried, when everything again stayed put. 'I never thought I'd ever be grateful for just being able to stand still in one place, did you?'

From THE SKYLARK OF SPACE by E. E. "Doc" Smith (1928)

The stewards, it appeared, were determined to make him eat for the whole twenty-five hours of the trip, and he was continually fending off unwanted meals. Eating in zero gravity was no real problem, contrary to the dark forebodings of the early astronauts. He sat at an ordinary table, to which the plates were clipped, as aboard ship in a rough sea. All the courses had some element of stickiness, so that they would not take off and go wandering round the cabin. Thus a chop would be glued to the plate by a thick sauce, and a salad kept under control by an adhesive dressing. With a little skill and care there were few items that could not be tackled safely; the only things banned were hot soups and excessively crumbly pastries. Drinks of course, were a different matter; all liquids simply had to be kept in plastic squeeze tubes.

From 2001 A SPACE ODYSSEY by Sir Arthur C. Clarke (1969)
Fast Food

Quick cold or hot food exists now in the real world. Granola bars, cup-of-noodles (just add hot water), and frozen dinners you heat in the microwave.

There does exist "flameless ration heaters" when you do not have access to electricity. The heating element is a package of finely-divided magnesium metal, alloyed with a small amount of iron, and table salt. Just add water and it can raise the food to 38 °C in twelve minutes flat. But not recommended for use in a spacecraft because the blasted thing releases hydrogen gas. You do not want your habitat module catching on fire.


      They are interrupted by a bellow from Cookie. "Hey, Panyovsky! Come and get it —or I'll feed it to the hogs!"
     The medical officer grins. " 'Scuse me a sec." He crosses to the other side of the galley, where a plastipak of scrambled eggs waits for him, steaming on the counter. Korie forces himself to relax, is even grinning when the big medical officer returns and slides into his seat. There is an antiseptic cleanliness about him that Korie finds refreshing.
     "Y'know," Panyovsky says. "Sometimes I think the real captain of this ship is Cookie. Other times, I know it." He cracks open the pack, begins pouring ketchup over the eggs.

     "The whole galley is an anachronism," says Korie, "I'd give a nickel for an honest 'mat unit."
     "Well, this is a second-generation cruiser," explains the other. "And they weren't building them that way then. They thought that with artificial gravity, they could get away from the free-fall packs and return to a more traditional kind of food preparation — allowing, of course, for all the modern technical advances that have since come to the art and science of cooking." He cocks an eye at Korie. "So you see, my friend, what we have is something that is neither this nor that —but a little bit of each. We have a cook —whose main duty is to flash plastipaks. However," he adds thoughtfully, "I will admit his shish kebab isn't bad." He shovels a forkful of ketchup-covered eggs into his mouth.
     "Besides," Panyovsky adds, "there are certain advantages to having a cook instead of a 'mat unit. For one thing you have more flexibility in your choice of meals. Look, no matter what kind of a galley you've got, the food is kept in stasis boxes and flashed by microwave. All you've got with a 'mat unit is portion control; big deal, nobody complains about getting more or less than anybody else—but on the other hand, there's no second helpings. At least not without heating up a whole new pack. Now, with a cook, you know there's always something cooking, and you have the back stop of the plastipaks anyway."

From YESTERDAY'S CHILDREN by David Gerrold (1972)

      "Emergency rations! This's better stuff than we've been eating for three months." I pull the heat tab. A minute later, I peel the foil and — lo! — a steaming meal.
     It's no gourmet delight. Something like potato hash including gristly gray chopped meat, a couple of unidentifiable vegetables, and a dessert that might be chocolate cake in disguise. The frosting on the cake has melted into the hash. I polish the tray, belch. "Damn, that was good!"

From PASSAGE AT ARMS by Glen Cook (1985)

      Once inside, however, he switched on a whole bank of instruments and trained them on the girl. “Sit tight while they check you over.”
     The instruments cleared her dispassionately. “Radiation count normal—no tetramoluene contamination—micro-organism and virus count, negative.”
     Craig produced cups and saucers. “I know you don’t drink—tea or coffee?”
     “Coffee, please, Mike—darling.”
     He said: “Damn you, stop looking at me like that,” and took her in his arms.
     Several minutes later, slightly breathless, Craig dropped a brown cube into a cup of cold water. The cube not only contained coffee extract and milk but generated its own heat. He handed the steaming liquid to the girl. “Let’s hear this from the beginning.”
     She sipped the steaming coffee gratefully and tried to smile. “Somehow, as soon as I got here, I felt unhappy, I think you know what I mean.”
     He nodded quickly. He knew exactly what she meant. The curious feeling of unease when danger was present although not apparent to the normal senses.

From INVADER ON MY BACK by Philip E. High (1968)

      He had no idea what comprised her usual diet, but be bought a can of New York roast beef and one of Venusian frog-broth and a dozen fresh canal-apples and two pounds of that Earth lettuce that grows so vigorously in the fertile canal-soil of Mars. He felt that she must surely find something to her liking in this broad variety of edibles.
     She must have had some of the food concentrate after all, he decided, prying up the thermos lid of the inner container to release the long-sealed savor of the hot meat inside.
     "Well, if you won't eat you won't," he observed philosophically as he poured hot broth and diced beef into the dish-like lid of the thermos can and extracted the spoon from its hiding-place between the inner and outer receptacles. She turned a little to watch him as he pulled up a rickety chair and sat down to the food, and after a while the realization that her green gaze was fixed so unwinkingly upon him made the man nervous, and he said between bites of creamy canal-apple, "Why don't you try a little of this? It's good."
     He said nothing more until the meat was finished and another canal-apple had followed the first, and he had cleared away the meal by the simple expedient of tossing the empty can out of the window.

From SHAMBLEAU by C. L. Moore (1933)

      Stooping in the narrow capsule, I inspected his cargo. I had been prepared for the loot of some crime as fantastic as his tale of immortality. I was prepared for smuggled weapons—perhaps for a plot to seize the station for a base of Scabbard's pirates. I was even prepared to find medical equipment and supplies for a legitimate longevity experiment.

     What I found was caviar and wine.

     "A mortal small reward for all my desperate years of service with the Legion," his plaintive wail followed me. "But don't you doubt it's real! The best black caviar, packed in permachill for interstellar shipment all the way from Earth—every can cost a fearful fortune. Selected wines from old Earth—the choicest vintages of the last hundred years. Don't you damage it, in some fool search for stolen jewels or nuclear devices!"

From NOWHERE NEAR by Jack Williamson (1963)

Drinking Utensils

Emergency Rations

The always worth reading Future War Stories has a good article on Military Field Rations and Space Food.

Emergency or Survival food is typically found in emergency re-entry capsules and spacecraft lifeboats (although in reality lifeboats are a really stupid concept).

They also may or may not be stored in the ship proper to help deal with a temporary interruption of the food supply (such as a catastrophic malfunction in the CELSS). If all the algae got incinerated by a solar proton storm, the crew will need something to eat while a new crop of algae is grown to harvest. You see this in a couple of episodes of Star Trek: Enterprise, where emergency rations are used when the food replicator is non-functional.

Real-world emergency rations typically are nutrient bars containing about 2,400 calories (enough food for an entire day). Emergency rations are optimized to be portable (low mass + low volume), require no preparation, and stable for prolonged periods (years).

Flavor is not a design consideration, the starving will eat anything. Even if Nutraloaf has been ruled "cruel and unusual punishment". And unlike Humanitarian daily rations, being acceptable to a variety of religious and ethnic groups is also not a design consideration. It is practically impossible to make a food ration which is acceptable to all groups.

In science fiction, emergency rations on re-entry capsules are to help you survive being marooned on an uninhabited planet long enough to figure out what part of the local flora and fauna are edible. In reality, the chance local flora and fauna even existing are remote, edible or otherwise. Especially if you are limited to our Solar System.

The most famous science fiction field ration is the Federation Space Forces Emergency Ration, Extraterrestrial, Type Three (aka 'Extee 3' or 'estefee') from Little Fuzzy by H. Beam Piper. An extraterrestrial miner uses some to make first contact with the native sophonts, the so-called "little fuzzies".

Military field rations are portable easily prepared food issued to soldiers deployed in the field. In the US Army they are called MREs for Meal Ready to Eat. Around World War I these were called "iron rations".

Field Rations are optimized to be portable (low mass + low volume), easy to prepare, and reasonably tasty. You have to sit down to eat them, though. MREs used by the US Army have a mass of 510 to 740 grams, depending on its menu.

The US Army Aviation uses Aircrew Build-to-Order Meal Modules (ABOMM). These are MREs designed so that a pilot can eat them while simultaneously piloting an airplane: without the use of utensils, in a confined space, and needing only one hand. MREs typically require two hands to eat, while it is not recommended for the pilot to take both hands off the control yoke.

First Strike rations are for people on the go. This can range from a First-in scout traveling from their hypothetical starship to explore and evaluate a hypothetical habitable planet to an asteroid miner living for several days in their space suit and subsisting on whatever they can squeeze through their helmet's chow-lock.

First Strike rations are optimized to be ultra-portable (excessively low mass + low volume), need little or no preparation and are easy to eat while walking or during an EVA (eaten out of hand without the use of utensils). A FS ration have about half the mass of an MRE. Strikers gotta move fast, they can't be weighted down by bricks of MREs. Yes, first strike rations have no mass in free fall, but all the inertia will still be there. Which means Every gram counts. Especially if you are an asteroid miner with a Spartan propellant budget.


Luckily the Horde carried their own rations. Natives who themselves depended upon the natural produce of their land could not readily gauge the superior mobility of an army for whom the supply problem consisted of a relatively small amount of condensed food tablets and other concentrated rations, weeks’ needs being carried easily in an individual’s own belt pouch. The ancient “scorched-earth” policy would not be effective against Terrans—unless they could be kept from their base for a period comprising months.

From STAR GUARD by Andre Norton (1955)

     "Nobody home, Commander. Somebody cleaned the place out. Fuel stores zilch. Medical supplies, zip. Ten cases of emergency rations. That's it."

     The First Watch Officer comes through the Weapons hatch. He has a metal case in his arms, a sheet of paper in one hand. The Commander peers into the case. "Pass them around." He snatches the tattered sheet.
     Yanevich hands me a ration packet. I laugh softly.
     "Something wrong with it?" the Old Man asks.
     "Emergency rations! This's better stuff than we've been eating for three months." I pull the heat tab. A minute later, I peel the foil and — lo! — a steaming meal.
     It's no gourmet delight. Something like potato hash including gristly gray chopped meat, a couple of unidentifiable vegetables, and a dessert that might be chocolate cake in disguise. The frosting on the cake has melted into the hash. I polish the tray, belch. "Damn, that was good!"
     Yanevich gives each man a meal, then hands me another pack. They come forty-two to a case. He sets the last aside for the Chief. To my questioning frown, he says, "That's for your buddy."
     Out of nowhere, out of the secret jungles of metal, comes Fearless Fred (the cat), rubbing my shins and purring. I heat his pack, thieve the cake, place the tray on the deckplates. Fred polishes his tray in less time than I did mine.

From PASSAGE AT ARMS by Glen Cook (1985)

At least I was still alive, I was free of the dead ship in a Life Boat, and I had air to breathe even if it was not the air my lungs craved. It would seem my entrance into the projectile had activated its ancient mechanism.

If we were on course for the nearest planet, how long a voyage did we face? And what kind of a landing might we have to endure? I could breathe, but I would need food and water. There might be supplies — E-rations — on board. But could they still be used after all these years — or could a human body be nourished by them?

With my teeth I twisted free the latch which fastened my left glove, scraped that off, and freed my hand. Then I felt along my harness. These suits were meant to be worn planetside as well as for space repairs; they must have a supply of E-rations. My fingers fumbled over some loops of tools and found a seam-sealed pouch. It took me a few moments to pick that open.

I had not felt hunger before; now it was a pain devouring me. I brought the tube I had found up to eye level. It was more than I could manage to sit up or even raise my head higher, but the familiar markings on the tube were heartening. One moment to insert the end between my teeth, bite through, and then the semiliquid contents flooded my mouth and I swallowed greedily. I was close to the end of that bounty when I felt movement against my bared throat and remembered I was not alone. (the alien catlike creature Eet)

It took a great deal of resolution to pinch tight that tube and hold it to the muzzle of the furred one. Its pointed teeth seized upon the container with the same avidity I must have shown, and I squeezed the tube slowly while it sucked with a vigor I could feel through the touching of its small body to mine.

There were three more tubes in my belt pouch. Each one, I knew, was intended to provide a day's rations, perhaps two if a man were hard pushed. Four days — maybe, we could stretch that to eight.

The semiliquid E-ration contained moisture but not really enough to allay thirst.

My fingers closed about a tube of E-ration and I did not have to fake the avidity with which I gripped its tip between my teeth, bit through the stopper, and spit it out, before sucking the semiliquid contents. No meal of my imagination could have topped the flavor of what now filled my mouth, or the satisfaction afforded me as it flowed in gulps down into me. The mixture was meant to sustain a man under working conditions; and it would renew my strength even more than usual food.

From THE ZERO STONE by Andre Norton (1968)

"One thing," Michelle chimed in, "Kelly, take this," , she tossed him a flat metal box, about five centimeters on a side, with a metal chain. "Wear that around your neck at all times from now on. Those are your tracetabs. They contain all the trace elements your body needs. There are about three thousand tabs in that box (8.2 years). If we go on xeno-rations, you'll need them."

Kelly seemed puzzled.

"There are about a thousand planets," Sims explained, "that supply native food edible by humans. On maybe half a dozen of them, all the trace elements necessary for human survival are present in the food."

"If the soil and atmosphere are comparable to Earth's," Michelle continued, "native flora and fauna may give you all the protein, carbohydrates, and vitamins you need, but trace elements can be hard to come by. You'll die just as dead from lack of magnesium, phosphorous, or any number of other elements as from lack of water. If you get stranded on a xenoworld, that box can be your lifeline. Always keep it filled."

From SPACE ANGEL by John Maddox Roberts (1979)

The next day was the sixth we’d been in the fort. We were low on rations. Down at the roadblock we had nothing to eat but a dried meat that the men called “monkey.” It didn’t taste bad, but it had the peculiar property of expanding when you chewed it, so that after a while it seemed as if you had a mouthful of rubber bands. It was said that Line Marines could march a thousand kilometers if they had coffee, wine, and monkey.

James Comer notes:

In the French military, canned meat (spam, sort of) was called 'singe' ('monkey') because one brand showed Madagascar on the label.

As Dr Pournelle modeled the Falkenberg series on European history, the idea of a preserved meat called 'monkey' could have come from there also.

From WEST OF HONOR by Jerry Pournelle (1976)

     Captain Bly watched until the spacelock indicator changed from red to green, then thumbed the takeoff warning. The alarm sounded through the ship like a gargantuan eructation and the crew hurried to buckle in. Bill dropped into a vacant seat and pulled the straps tight just as Captian Bly switched on full power. Gravity sat on their chests with the 11G takeoff. Except for Bill who had a rat sitting on his chest as well as gravity, for it had been hurled from the pipes in the ceiling by the blast. It glared at Bill with gleaming red eyes, its lips pulled back by the drag of takeoff blast to expose its long, yellow incisors. Bill glared back, eyes equally red, his yellow fangs equally exposed. Neither could move and they glared in futile hatred until the engines cut out. Bill grabbed for the rat but it leaped to safety and ran out the door.

     A shrill scream cut through his words, followed by the roar and splat of blaster fire.
     "We're being attacked!" Praktis screeched. "I'm unarmed! Don't fire! I am a doctor, a noncombatant, my rank only an honorable one!"
     Bill, his brain cells still so gummed by sleep and ethyl alcohol, drew his blaster and ran down the dune towards the firing instead of away from it which, normally, he would have done. He picked up speed, could not stop, saw Meta before him, standing and firing, could not turn and ran into her at full gallop.
     They collapsed into an inferno of arms and legs. She recovered first and punched him in the eye with a hard fist.
     "That hurt," he whimpered, holding his hand over it. "I'm going to have a shiner."
     "Move your hand and I'll give you another one to match. Why did you knock me down like that?"
     "What was all the shooting about?"
     "Rats!" She grabbed up her blaster and spun about. "All gone now. Except the ones I blasted into atoms. They were getting at our food. At least we know what lives on this planet. Great big nasty gray rats."
     "No they don't," Praktis said, having recovered from his fit of cowardice and rejoined the party. He kicked a piece of exploded rat with his toe. "Rattus Norvegicus. Mankind's companion to the stars. We must have brought them with us."
     "Sure did," Bill agreed. "They bailed out of the spacer even before you did."
     "Interesting," Praktis mused, rubbing his jaw, nodding, squinting, doing all the things that indicate musing. "With a whole planet to nosh in—I ask you —why do they come creeping back here to eat our food?"
     "They don't like the native chow," Bill suggested.
     "Brilliant but incorrect. It is not that they don't like it—there is none of it. This planet is barren of life as any fool can plainly see."

     Cy did and he snipped off samples as instructed. Meta quickly had enough of this metallurgical horticulture and went back to their camp. And resumed shouting and shooting. The others joined her and the surviving rats fled into the desert. Praktis scowled at the torn open boxes of supplies.
     "You, Third Lieutenant, get to work. I want the food repacked and rat-proofed at once. Issue orders. But not you, Cy. I want your help. Over this way."
     Bill seized up a torn plastic container of compressed nutrient bars. Known jocularly to the troops as Iron Rations. Even the rats hadn't been able to dent them; broken rat teeth were stuck in the wrapper. After boiling for twenty-four hours they could be broken with a hammer. Bill searched for something edible and a little more tender. He found some tubes of emergency space rations labeled Yumee-Gunge. The others were watching him intently so he passed the tubes around and they all squeezed and sucked and made retching noises. The gunge was loathsome but promised to sustain life. Although the quality of life that it sustained was open to question. After this repulsive repast they worked together in harmony since the pitiful pile of supplies was all that stood between them and starvation. Or thirsting to death, which is faster.


Disgusting Expedients

On old wet-navy vessels (age-of-sail or steam) months separate opportunities to re-provision the ship with fresh food. So the crew has to make do with what is on board. Which can lead to some nauseating but necessary protocols.

I remember reading one of my grandfather's US Naval Officer's handbooks. There was a tip about determining if a leg of pork or other large cut of meat hung in the ship's larder was too rotten to eat or not. What you do is take a sharp knife, insert it into the meat until the knife-tip makes contact with the bone, remove the knife, then smell the knife tip. If the tip smelled decayed, throw out the meat.

Science fiction authors should take heed that spacecraft on eight month Hohmann trajectories to Mars are under similar constraints, and may need to resort to analogous solutions. Authors can start with the realization that the water on board the spacecraft is typically recycled urine and find more inspiration in age of sail historical novels.


In Navy jargon, the goat locker is a lounge, sleeping area, and galley on board a naval vessel which is reserved for the exclusive use of chief petty officers. By tradition, all other personnel, including officers and even the commanding officer, must request permission to enter the goat locker.


The term goat locker takes its origins from wooden ship sailing times, when goats were kept aboard ship. The goat was used for its ability to consume nearly all forms of refuse, and produce milk for the crew. The quarters for the goat were traditionally in the Chief Petty Officer mess, which inherited the moniker "goat locker". In modern times, 'goat locker' represents any gathering place, on- or off-ship, where Chief Petty Officers hold private functions.

From the Wikipedia entry for GOAT LOCKER

      “Young carrots!” went on Lord Henry, peering into each vegetable dish in turn. “And what’s this? I can’t believe it!”
     “Spring greens, Lord Henry,” said Pellew. “We still have to wait for peas and beans.”

     “How do you get these chickens so fat, Sir Edward?” asked Grindall.
     “A matter of feeding, merely. Another secret of my chef.”
     “In the public interest you should disclose it,” said Cornwallis. “The life of a seasick chicken rarely conduces to putting on flesh.”
     “Well, sir, since you ask. This ship has a complement of six hundred and fifty men. Every day thirteen fifty-pound bread bags are emptied. The secret lies in the treatment of those bags.”
     “But how?” asked several voices.
     “Tap them, shake them, before emptying. Not enough to make wasteful crumbs, but sharply enough. Then take out the biscuits quickly, and behold! At the bottom of each bag is a mass of weevils and maggots, scared out of their natural habitat and with no time allowed to seek shelter again. Believe me, gentlemen, there is nothing that fattens a chicken so well as a diet of rich biscuit-fed weevils. Hornblower, your plate’s still empty. Help yourself, man.”

     Hornblower had thought of helping himself to chicken, but somehow — and he grinned at himself internally — this last speech diverted him from doing so. Hornblower found himself thinking that if ever he became a post captain, wealthy with prize money, he would have to devote endless thought to the organization of his cabin stores.

From HORNBLOWER AND THE HOTSPUR by C. S. Forester (1962)

And last but not least, there was the ever-present, ever-despised hard-tack or the ‘ship’s biscuit’.

If you’ve ever eaten an ANZAC biscuit, you’ll know how hard and tough it can be. Hard-tack made ANZAC biscuits feel like overcooked pasta. Hard-tack was a special kind of cookie which was baked so that when it came out of the oven, it was literally rock hard. You could drive a nail into a plank of wood with this thing, and it wouldn’t break. Hard-tack was notoriously difficult to eat. But why did they stock it? Because hard-tack is like the cockroach of foodstuffs. It can survive almost anything. Provided that it was sealed properly and kept dry, hard-tack could keep fresh for months, even years at sea. Hard-tack was so damn tough that if you ate it ‘raw’, you’d probably break your teeth off! So instead, sailors would dunk it into their tea or coffee to soften it up a bit before taking a bite out of it. But before you dunked it into the tea, you had to bang it on the table a few times to knock out the beetles and weevils and other nasty little insects that had taken up residence inside your lunch.

You’ll notice that there is a distinct lack of greenery in the shipboard diet. Keeping things like fruits and vegetables fresh onboard a sailing ship with no fridges, was a nearly impossible task. Fruit goes mouldy after a few days, a few weeks if you’re lucky. And greens were important, and still are important, for preventing the horrific disease called scurvy (ordinarily I'd add a link to the Wikipedia entry, but the photos are horrific).

Scurvy was nasty. It caused your joints to ache, it made your gums bleed, it made you go dizzy and faint, and when it was really bad, your teeth rotted and you’d be spitting your pearly-whites all over the floor. To prevent this, sailors drank great quantities of fruit-juice. It’s for this reason that British sailors were called “Limeys”; because they drank gallons and gallons of lime-juice. On the same ticket, German sailors ate pounds and pounds of sauerkraut. It’s for this reason that Germans are called “Krauts”.

Waste Disposal

On the topic of human metabolic waste, NASA assumes:

Waste per astronaut per day
Dry Feces0.032 kg
Fecal Water0.091 kg
Dry Urine0.059 kg
Urine Water1.886 kg
Dry Perspiration0.018 kg
Respiration and
Perspiration Water
2.277 kg

An attempt should be made to reclaim the water. 4.254 kg of water per astronaut per day is too much to just throw away.

Male astronauts will use approximately 28 grams per day of toilet paper, minimum. Female will use 64 grams per day, because unlike their male counterparts, they wipe after urination. There will be about 5.1 grams per day of waste clinging to the toilet paper.

More toilet paper is required than is necessary under one gravity since in microgravity the fecal material has no particular inclination to separate from the body.

Women experience menstruation for 4 to 6 days occurring every 26 to 34 days. The total amount of menses is about 113.4 grams, of which about 28 grams is solids and the rest is water. This is highly variable. Approximately 104 grams of menstrual pads or tampons are consumed each period, again highly variable.

Female crew members on the International Space Station use medication to prevent menstruation for up to six months, but this may not be acceptable for longer missions.

This brings up the question of how to use a space toilet in free fall. The sad fact of the matter is "there ain't no graceful way".

Naoto Kimura mentioned that "Oh-gee Whiz" would be a good brandname for space toilet.


Schweickart: In terms of not in the suit, and in the spacecraft again that's varied. In Apollo, for feces you just stuck a plastic bag on your butt which was 6 inches in diameter' something like that' maybe a little bit less 12 inches or so long and the mouth of it had a flange at the top with an adhesive on it, and you'd peel the coating off the adhesive and literally stick it to your butt. Hopefully centrally located. And if you think you know where your rear end is, you really find out, because you'd paste it on very carefully! So, you stick that to your butt, and then you go ahead and take a c**p. But then the problem comes, because there's no particular reason whatsoever for the feces to separate from your rear end. So as a result the problem is left as an exercise to the student to peel the bag off and make sure everything stays within the bag, and get all wiped off. It's basically a one hour procedure.

Warshall: For each time?

Schweickart: Yeah, from the time you start to peel down to stick the bag on and all that, till the time you have finished cleaning up and have everything wrapped up and stowed and have your clothes back on and everything, it's damn near an hour. And at times it's taken longer. Because when you peel that bag off, you try to take a handful of paper, and you know, lead the way in with that, but by the time you get done, you've got stuff spread all over your backsides, and if you're not careful, your clothes, and everything else.

Warshall: Have you ever had an accident where the stuff got out of the bag?

Schweickart: No, because generally speaking it's fairly sticky so once it's in the bag it doesn't come out, but the problem is making sure it's loose of you when you get the bag off. It just is not a simple procedure, no matter what you do. Well, in any case, that was in Apollo.

In terms of the urine system , that was simple in Apollo. It's just the same as a relief tube in airplanes. It's a tube with a funnel on the end that you urinate into. And, at the other end of the tube is lower pressure than at the business end of it. So there's a differential pressure in the outward direction.

Well, we did exactly the same thing, except you know on the other end of the hose you've got a vacuum instead of a couple of psi down or something. So you just basically urinate into a relief tube. There have been various designs so you can use a roll-on cuff to do it or you can just hang it out there in the air and do it. There are a couple of different variations, but basically you urinated directly overboard through a relief tube. And of course, you didn't lose much cabin air, because while the liquid is in the tube, in the hose, no air is going down. It's differential pressure carrying the liquid. So it's only a matter of designing it for the right flow rate.

Warshall: Do you use any kind of special toilet paper?

Schweickart: No, not that I know of. There may be some flame retardant chemicals put into it just so you don't have any unnecessary flammable materials around, but I'm not sure whether that's the case or not.

Warshall: So it's just like any other toilet paper.

Schweickart: It's basically like any other toilet paper.

Warshall: Is it stuck in the bag and then burned, or . . .?

Schweickart: No, it is in the same bag with the fecal material, and in the early missions that was a plastic bag that you mixed in a disinfectant or actually an anti-gas, oh, what's the word I want, I guess disinfectant would be the best word, which holds down the generation of gas, and you mix that disinfectant liquid all through the fecal material. You mix it in, seal the plastic bag.

Warshall: How do you get it in there?

Schweickart: Well, it's in a small, like a ketchup, a little plastic container like you find ketchup in in restaurants, in a cafeteria or something, it's like that. You tear the slit across the top, being careful not to squeeze it so the stuff comes out, and then you drop that into the fecal container, and then seal the fecal container. Then you squeeze it through the, you know, externally, you know, which forces it out of the container, and then you mix it by massaging the fecal bag. It's really fun when it's still warm.

From "THERE AIN'T NO GRACEFUL WAY" Astronaut RUSSELL SCHWEICKART talking to Peter Warshall, collected in CoEvolution Quarterly Winter 1976-77

The Johnson Space Center "potty cam," as it is more casually known, is an astronaut training aid. It provides a vivid, arresting perspective on something you've had intimate contact with all your life but never really seen. Positioning is critical because the opening to a Space Shuttle toilet is 4 inches across, as opposed to the 18-inch maw we are accustomed to on Earth.

"The camera enables you to see if your butt, your..." Broyan pauses in search of a better word: not more polite, just more precise, "...anus lines up with the center." Without gravity, you can't reliably gauge your position by feel. You are not really sitting on the seat. You are hovering in close proximity. The tendency, says Broyan, is to touch down too far back. Then your angle of approach is off, and you sully the back of the transport tube and plug some of the air holes that encircle the rim. Bad, bad move. Space toilets operate like shop vacs; "contributions," to use Broyan's word, are guided along, or "entrained," by flowing air rather than by water and gravity, two things in short-to-nonexistent supply in an orbiting spacecraft. Plugged air holes can disable the toilet. Additionally, if you gum up the holes, it is then your responsibility to clean them out—a task Broyan understates as "arduous."

Zero-gravity excretion is not entirely a joking matter. The simple act of urination can, without gravity, become a medical emergency requiring catheterization and embarrassing radio consults with flight surgeons. "The urge to go is different in space," says Weinstein. There is no early warning system as there is on Earth. Gravity causes liquid waste to accumulate on the floor of the bladder. As the bladder fills, stretch receptors are stimulated, alerting the bladder's owner to the growing volume and delivering an incrementally more insistent signal to go. In zero gravity, the urine doesn't collect at the bottom of the bladder. Surface tension causes it to adhere to the walls all around the organ. Only when the bladder is almost completely full do the sides begin to stretch and trigger the urge. And by then the bladder may be so full that it's pressing the urethra shut. Weinstein counsels astronauts to schedule regular toilet visits even if they don't feel the urge. "And it's the same with BMs," he adds. "You don't get that same sensation."

(ed note: this is why the Shuttle first aid medical kit included a Foley catheter)

Weinstein says he doubts that many of the astronauts use the potty cam. "I get the sense most of them don't want to see themselves." Weinstein provides an alternate positioning tactic, "the two-joint method." The distance between the anus and the front of the seat should equal the distance between the tip of the middle finger and its big knuckle.

Along the same wall as the Positional Trainer is a fully appointed and functioning Space Shuttle commode. It looks less like a toilet than a high-tech, top-loading washing machine. Though the device itself is a high-fidelity version of the one on board the shuttle, the experience is not. There is gravity down here at Johnson Space Center, and that makes all the difference. Gravity facilitates what is known in aerospace waste collection circles as "separation." In weightlessness, fecal matter never becomes heavy enough to break away and drop down and venture forth on its own. The space toilet's air flow is more than an alternate flushing method. It facilitates the Holy Grail of zero-gravity elimination: good separation. Air drag serves to pull the material away from its source.

A separation strategy courtesy of Weinstein: spread the cheeks. That way, there is less contact between the body and the "bolus" (another in the waste engineer's vast arsenal of euphemisms)—and therefore less surface tension to be broken. The newest seat is designed to function as a "cheek spreader" to facilitate a cleaner break.

A more sensible arrangement might be to adopt the posture favored by much of the rest of the world—and by the human excretory system itself. "The squat tends to spread the cheeks," says Don Rethke, a senior engineer at Hamilton Sundstrand, the contractor on many of the NASA waste collection systems over the years. Rethke suggested to NASA that they add a set of foot restraints higher up, to accommodate those who wish to approximate the squatting posture in zero gravity. No go. When it comes to the astronauts' creature comforts, familiarity wins out over practicality.

In the aftermath of Apollo, where there were fecal bags rather than toilets, bathroom facilities became a charged topic. "When the astronauts came back, they physically and psychologically wanted a sit-down commode," says Rethke.

Understandable. The fecal bag is a clear plastic sack, similar to a vomit bag in its size, holding capacity, and ability to inspire dread and revulsion." A molded adhesive ring at the top of the bag was designed for the average curvature of an astronaut's cheeks. It rarely fit. The adhesive pulled hairs. Worse, without gravity or air flow or anything else to foster separation, the astronaut was obliged to employ his finger. Each bag had a small inset pocket near the top, called a "finger cot".

The fun didn't stop there. Before he could roll up and seal the bag to trap the offending monster, the crew member was further burdened with tearing open a small packet of germicide, squeezing the contents into the bag, and manually kneading the germicide through the feces. Failure to do so would allow fecal bacteria to do their bacterial thing, digesting the waste and expelling the gas that, inside your gut, would become your own gas. Since a sealed plastic fecal bag cannot fart, it could, without the germicide, eventually burst.

Given the complexity of the chore, "escapees," as free-floating fecal material is known in astronautical circles, plagued the crews.

From PACKING FOR MARS by Mary Roach (2010)

Feces and Debris

The objective of the feces and debris collection and transport subsystem is to provide a means for collecting and transporting these wastes to the solid waste management subsystem where treating and processing are performed. Collection and transfer must be accomplished under zero gravity conditions, while the escape of solid waste to the cabin is positively prevented. The principal solid wastes include body wastes, unused food, and food containers.

Feces Collection. There are basically two techniques for collecting feces in a weightless state; namely, manual collection with a glove or bag, and pneumatic collection with the use of forced cabin gas for detachment and transfer. The glove method, as developed for Project Gemini, is a simple, low-weight technique but is psychologically objectionable and does not provide a means for preventing flatus from entering the cabin atmosphere. The technique, however, is desirable for use as an emergency fecal collector or where a pneumatic collector cannot be provided. On missions of durations longer than several days, fecal collection equipment is required to maintain the physiological and psychological well-being of the crew.

Feces can be detached from the anus in a weightless state by gas impingement, and then carried into a collection bag or processing device by the same gas flow (e.g. Des Jardins et al., 1960; Charanian et al., 1965. & Rollo et al., 1967). The gas flow rate required is a function of equipment design; experience has shown that it should be in the range of 2 to 10 cfm. The gas is drawn through the device by a centrifugal blower and passed through a filter with activated carbon before being returned to the cabin. Recent laboratory tests have shown that:

1. Separation of feces from perineal surface was best accomplished by short duration impulse from a 30 to 40 psig air stream aimed at the fecal mass; water or air-water streams are not as effective as air alone.

2. Only small amounts of air are needed to effect separation, e.g. 0.1 to 0.2 std. 3 ft. at 30 to 40 psig, flowing at 6 cfm for 2 seconds.

Many types of fecal collection bags have been devised. None of these bags has all the characteristics desired; namely,

High permeability for gases
Impermeable to liquids
High tear strength
Low weight

The two materials proven to be most successful so far are porous cellulose and a polyethylene; both are fabricated from 10 mil material and treated to prevent passage of liquids with pressure differentials less than 4 inches of water. Recently, these materials have been laminated with cloth to provide the tear strength desired.

Experiments have demonstrated that man can reliably defecate into a 4 inch diameter opening—provided this opening is indexed with respect to the anal perimeter. This is the minimum size recommended for a fecal collection bag or the opening in a fecal storage container.

Pneumatic collection provides for more natural defecation. In addition, it also entrains any flatus excreted. To minimize odors, the fecal collection gas should be passed through a bed of activated charcoal. If a catalytic oxidation unit is used for contamination control, the fecal collection gas should be directed to this unit for removal of any H2, CH4, and H2S. Also pneumatic collection provides a suitable means for collecting vomitus (i.e., "praying at the porcelain altar").

Overboard Dump. Wastes can be disposed of overboard in gaseous or liquid form. Dumping of solids is not permitted to avoid imparting the wastes on the ground and/or the aerospace vehicle. Urine, of course, can be dumped as a liquid directly from a urinal or from a urine-gas separator if it is permissible to contaminate the external environment with microorganisms. Solids, however, should be incinerated or thermally decomposed.

A detailed investigation of waste incineration/decomposition is described in Dodson and Wallman (1964). This study concluded that incineration requires (1) an ignition temperature of 1000°F, (2) an energy input of at least 1 kilowatt-hours per man-day, and (3) an oxygen input of up to 0.2 pounds per man-day. Under these conditions the ash remaining is less than 10 grams per man-day and can be easily blown overboard by venting.

If oxygen is not available for incineration, the wastes can be gasified by thermal decomposition. However, this technique requires approximately 4000 BTU/Ib of wastes at a temperature level of 1200°F. In addition, the overboard vent line must be maintained at this temperature to avoid condensation and plugging.

Incineration and thermal decomposition have not appeared to be practical for aerospace vehicles in the absence of a nuclear heat source (atomic sewage treatment, what a concept!). However, when these heat sources are available, it will most likely be advantageous to recover usable products from wastes.


      217-9963 (BIOWASTE)

     For interstellar freight purposes, biowaste is defined as nonspecific organic matter for disposal: this includes categories as disparate as sewage, grooming fragments (i.e. shed skin, hair clippings, etc.), animal waste, plant matter, spoiled food, medical and surgical waste, corpses, et. sim., and mixed lots of any or all of the above.

     Biowaste is typically shipped locally to skyfarms for sterilization, decomposition, and processing into fertilizer, or to new habitats and worlds undergoing ecopoesis for use in soilbrewing and dirt farming; in the modal case, that of oxygen-breather biowaste, it serves as a rich source of CHON compounds and CHNOPS. It is, however, important to check the subclassifications (if present); organic matter for disposal from or of species other than oxygen-breathers is also properly classified as biowaste, even if from an oxygen-breather perspective it more closely resembles industrial chemicals.

     Note: Due to the potential for infection and ecological cross-contamination, improper disposal (i.e., other than to a sealed biowaste processing facility) of biowaste is classified as a crime against nature under Imperial law, and is subject to severe censure.

     Applicable special handling characteristics: All cargoes classified 217-9963 are considered biohazard cargoes, requiring sealed containers and appropriate handling. Depending upon the precise nature of the biowaste in question (per above), such cargoes may also be classified as flammable (often due to decay products, such as methane), corrosive, or radioactive.

– Merchanter’s Association Handbook, “Trade Categories”

(ed note: in many computer programming languages, the vertical bar character "|" means "or". So the title can be read as "Black Water or Black Gold")


Astronaut hygiene is complicated.

NASA allocates 26 kilograms of water per astronaut per day for personal hygiene. This will be rationed, so use it wisely. It is no fun to go around all day with a head full of shampoo.

Bath and showers are very difficult in free fall. The crew will probably be reduced to sponge-baths or maybe a shower while zipped up in a bag. People who have gone camping are familiar with how surprisingly difficult it is to keep clean in the absence of running water. As do city-folk living in houses near a water main break who have to make do without tap water for a few days. You tend to take for granted the luxury of accessing unlimited amounts of water out of the faucet. In the space environment, water is strictly limited, and what water there is performs poorly as a cleansing agent in free fall.

Crew will probably be required to take showers "navy style", since wet navy ships also have limited water (non-salt water at least). You turn on the shower water to get your body wet. You then turn off the water to conserve it while you lather up with soap. Then you turn the water back on to rinse off.

In Robert Silverberg's 1968 scifi novel World's Fair 1992 he mentions "molecular baths" which use sound waves to remove dirt with no water required. In Babylon 5, only the command and VIPs have the luxury of water showers, the rest have to make do with "vibe showers". The crew of Babylon 5 also use an ultraviolet lamp instead of a sink with running water to sterilize their hands after using the urinal. There is a sonic shower in Star Trek: The Motion Picture, where the robot form of Lieutenant Ilia materializes. And in Andre Norton's space novels, the bathing room is called the "fresher" which presumably is short for "refresher". On spacecraft the freshers are tiny due to the cramped conditions common to starship habitat modules, these are called "pocket freshers". As TV Tropes says: Our Showers Are Different.


Lack of cleanliness

Water is carefully conserved in space because the crew must carry all of their supplies with them on the long journey to Mars, and space (more precisely, mass) is at a premium on such a mission. This makes keeping clean a challenge. Mars-bound astronauts will have moist towelettes for daily scrubbing, but they’ll only be able to shower infrequently. Experienced astronauts say they create a wider buffer of personal space to keep out of odour range of their crew mates.

From THE RACE TO MARS Discovery Channel

(ed note: Bill has won a prize to be a part of the World's Fair 1992, the first to be held in a space station. He meets his room mates and is introduced to the spartan features of their cabin.)

      “First I’ve got to find out if I can get in. And even before that—if you’ll show me where I can grab a shower and spruce up a little—”
     “Right over there,” Antonelli said. He pointed to a short dull-colored nozzle jutting from the wall next to the power ocarinas.
     “There. You never saw a molecular bath before?” Antonelli laughed. “This place is run on an economy basis. They can't afford to import water just to keep mere employees clean. Get your clothes off and I'll show you how it works.”
     Bill peeled down. He had heard of these new devices, but had never actually seen one before. They worked by sound waves—more accurately, ultrasonic waves—which bombarded your skin with vibrations pitched to separate the grime from the skin in one easy process. Stepping over to the nozzle, Bill watched closely as Nick Antonelli showed him how to operate the machine. “The marks on the floor outline the ultrasonic field’s sphere of influence. Go on, step inside the circle there." Bill obeyed. “Now switch the thing on," Antonelli said. Bill thumbed the on-button at the base of the nozzle and heard a faint humming sound. That was all. He felt nothing but as he looked down he saw his skin becoming visibly pinker and cleaner, as though he had scrubbed it with a stiff brush.
     “Okay,” Antonelli said. “That's plenty. How clean do you want to get, anyway?”
     Frowning, Bill said, “I don’t feel clean, somehow. I know I am, but unless I come out dripping wet from a shower, it doesn’t seem right.”
     “Face up to progress, son. That dripping-wet sensation is strictly obsolete."

(ed note: Emily Blackman, the snooty privileged granddaughter of Senator Blackman, drags Bill along on a secret impromptu tour of the forbidden maintenance sections of the Worlds Fair. Including the nuclear interceptor missiles used to defend the fair from angry third world nations who have issues with a playland for the rich and powerful orbiting overhead. Emily doesn't care because she has that entitled feeling which comes from having a senator for a grandfather. Emily and Bill's tour has gotten them both covered in dust and grease.)

     (Emily said) “And you have grease an inch deep everywhere.”
     (Bill said) “So do you.”
     “It looks incriminating, doesn't it? But we can fix ourselves fast. In here.”
     She led him into a low, squat building near the place where they had entered the Satellite wall. Tools of all sorts were stacked on the floor. “It’s the maintenance shack,” Emily explained. “For the workmen who take care of the machinery behind the wall. And over here is a molecular bath that they use when it’s time to clean up." She shut the door and stationed him beside it. “The door doesn’t lock, so you’ll have to stand guard. Nobody’s likely to come prowling around here at this hour, but even so we don’t want to take the chance, so lean against the door and make it seem locked to anybody who might try to come in.” Her hands went to the magnetic catches of her tunic, and as she slipped out of the garment she added casually, “And keep your back turned. Peeking’s no fair.”
     He pressed against the door and waited. In a moment he heard the hum of the molecular bath. Time ticked away slowly until finally Emily said, “All right. I’m decent.”
     Bill turned. She was more than decent: she was radiant, as shiningly clean as though she were on her way to her senior prom. She nodded toward the nozzle of the molecular bath. As he crossed the room to take his turn under it she said, “You really didn’t peek!” She seemed surprised.
     “How can you be so sure?”
     “Because I was watching you all the time,” she said.
     He stood facing away from her, letting the ultrasonic waves go to work first on his bare skin and then on his grimy clothes, and wishing vaguely that he had never let himself get mixed up with Emily in the first place.
     He slipped back into his clothes and turned around. Emily was virtuously facing the door.

From WORLD'S FAIR, 1992 by Robert Silverberg (1970)

She felt a bit guilty about implying that she had some kind of important errand to run before the transport docked. In fact, she wanted to take a shower and change clothes. Zero-g showers amused her. The water skimmed over her, pulled across her body by a mild suction at one side of the compartment. When she was wet, she turned off the water and lathered herself with soap, scraped olf most of the suds with an implement like the sweat-scraper of an ancient Greek athlete—or a racehorse—and turned the water on again till the last of the soap washed away. It felt like standing in a warm windy rain. When she finished, she was covered all over with a thin skin of water. She scraped herself off again, got out of the shower and closed the door, and turned the vacuum on high to vent the last of the water out of the compartment and into the recycler. Her whole body felt tingly and refreshed.

As she dressed in her favorite new fancies, the warning signal sounded softly through the ship. A few minutes later, microgravity replaced zero—g as the transport decelerated.

From STARFARERS by Vonda McIntyre (1989)

He levered himself out of bed, sucked down some painkillers and rehydration goo, stalked to the shower, and burned a day and a half’s ration of hot water just standing there, watching his legs get pink. He dressed in his last set of clean clothes. Breakfast was a bar of pressed yeast and grape sweetener. He dropped the bourbon from the bedside table into the recycler without finishing it, just to prove to himself that he still could.

From Leviathan Wakes by James Corey (2011)

For a longer period nothing more notable took place than the incident in which Roger Stone lost his breathing mask while taking a shower and almost drowned (so he claimed) before he could find the water cut-off valve. There are very few tasks easier to do in a gravity field than in free fall, but bathing is one of them.

From THE ROLLING STONES by Robert Heinlein (1952)

The primary hygiene component of a standard shipboard ‘fresher is a cylindrical translucent compartment, resembling a drug capsule set on its end, with a watertight sealing door. At top and bottom, gratings conceal powerful counter-rotating fan/turbine units.

In dynamic mode, these fan/turbines are engaged to blow (at the nominal “top”) and suck (at the nominal “bottom”) a water/air colloid past and over the bather at configurable velocities ranging from strong breeze to hurricane-strength wind, providing the water with a functional simulation of gravitic flow – a “shower”. To conserve water where necessary, many ‘freshers recirculate filtered water while in operation, requiring fresh water input only for the initial fill and the final rinse cycle.

In static mode, the gratings close and the capsule itself fills entirely with water – a microgravity “bath”.

In the former mode, breathing while bathing is, at best, difficult; in the latter, it is downright impossible. Early-model ‘freshers included a built-in breathing mask connected to ship’s life support to ameliorate this problem; in these days of respiratory hemocules which enable the modal transsoph to hold their breath for over an hour, ‘fresher designers tend to assume that this will not be a problem. Those without such hemocules must, therefore, remember to take a portable breather with them when bathing.

– The Starship Handbook, 155th ed.


(ed note: The time agents are trapped on an alien spacecraft traveling to an unknown location, and they have no idea what anything is or how it works. But one of the techs knows how to work the alien shower)

     “I’d guess we’ll have to try a lot of things before this trip is over—if it ever is. Right now I’d like to try a bath, or at least a wash.” Ross surveyed his own scratched, half-naked, and very dirty body with disfavor.
     “That you can have. Come on.”
     Again Renfry played guide, bringing them to a small cubbyhole beyond the mess cabin. “You stand on that—maybe you can hold yourself in place with those.” He pointed to some rods set in the wall (they are in free fall). “But get your feet down on that round plate and then press the circle in the wall.”
     “Then what happens? You roast or broil?” Travis inquired suspiciously.
     “No—this really works. We tried it on a guinea pig yesterday. Then Harvey Bush used it after he upset a can of oil all over him. It’s rather like a shower.”
     Ross jerked at the ties of his disreputable kilt and kicked off his sandals, his movements sending him skidding from wall to wall. “All right. I’m willing to try.” He got his feet on the plate, holding himself in position by the rods, and then pressed the circle. Mist curled from under the edge of the floor plate, enveloped his legs, rose steadily. Renfry pushed shut the door.
     “Hey!” protested Travis, “he’s being gassed!”
     “It’s okay!” Ross’s disembodied voice came from beyond. “In fact—it’s better than okay!”
     When he came out of the fogged cubby a few minutes later, the grime and much of the stain were gone from his body. Moreover, scratches that had been raw and red were now only faint pinkish lines. Ross was smiling.
     “All the comforts of home. I don’t know what that stuff is, but it peels you right down to your second layer of hide and makes you like it. The first good thing we’ve found in this mousetrap.”
     Travis shucked his kilt a little more slowly. He didn’t relish being shut into that box, but neither did he enjoy the present state of his person. Gingerly he stepped onto the floor disk, got his feet flattened on its surface, and pressed the circle. He held his breath as the gassy substance puffed up to enfold him.
     The stuff was not altogether a gas, he discovered, for it was thicker than any vapor. It was as if he were immersed in a flood of frothy bubbles that rubbed and slicked across his skin with the effect of vigorous toweling. Grinning, he relaxed and, closing his eyes, ducked his head under the surface. He felt the smooth swish across his face, drawing the sting out of scratches and the ache out of his bruises and bumps.

From GALACTIC DERELICT by Andre Norton (1959)

Suspended nude in the air, she reached into her padded wall locker, braced a leg, opened the sliding panel and removed a plastic package from a box secured to an overhead shelf with velcro. She peeled away the wrapper, stuffing the plastic in the ever-ready disposal container, and opened a neatly folded, lightly scented towelette. Slowly and luxuriantly she removed the oily perspiration from her body. She smiled as the scent hovered about her. No Soviet quartermaster had ever issued these to the women cosmonauts who left the Earth behind! What she carried with her among her personal belongings were gifts from Susan Foster...

...Whatever their technical prowess, and Tanya knew it was most formidable, it was in the science of personal touch that the Americans were absolutely incredible. They were light years ahead of anything that emerged from Mother Russia. In the packages Susan gave her, concealed within a box supposedly filled with computer disks, were these sealed towels and their lightly scented fragrance, just enough to detect, and moist enough to clean and freshen her skin. It dried within seconds of its application and then you simply disposed of the towelette. She had hundreds of them. Some of the other women learned of her treasure and Tanya shared with them.

It made life infinitely more bearable after weeks and months in weightless orbit. It rendered personal hygiene a pleasure in a complicated, clanging, ear-stabbing vessel that reeked of oil, plastic, garlic and scallions and all manner of unpleasant body odors that soaked into the very "floors" and "walls" of station cubicles. The Americans, Tanya smiled, demanded their little luxuries wherever they went, and their woman cosmonauts were even more fiercely demanding than their men. Hooray for you, Tanya thought generously of the Americans. Long voyages into space with ships that stank left much to be desired, and if nothing else, the Americans were able to make of space adventure a mission that did not permanently wrinkle the nose...

     ...Susan slipped a personal package to Tanya...
     ..."How many are in here?"
     "Four hundred."
     "Tanya's eyes widened. "Four hundred?"
     "We're the miracle workers of folded fragrance."

From EXIT EARTH by Martin Caidin (1987)

      Attlebish was shaving. The small abrasive pencil gave out its spray of fine particles that swept over cheek and chin, biting off the hair neatly and then disintegrating into impalpable dust.
     Baley recognized the instrument through hearsay but had never seen one used before.
     “You the Earthman?” asked Attlebish slurringly through barely cracked lips, as the abrasive dust passed under his nose.
     Baley said, “I’m Elijah Baley, Plainclothesman C-7. I’m from Earth.”
     “You’re early.” Attlebish snapped his shaver shut and tossed it somewhere outside Baley’s range of vision. “What’s on your mind, Earthman?”

From THE NAKED SUN by Issac Asimov (1957)

      Biron looked up briefly. He was shaving, and handling the Tyranni erosive spray with finicky care.

     ‘No,’ he said, ‘they’re not moving. Why should they? They’re watching us, and they’ll keep on watching us.’

     He concentrated upon the difficult area of the upper lip, and frowned impatiently as he felt the slightly sour taste of the spray upon his tongue. A Tyrannian could handle the spray with a grace that was almost poetic. It was undoubtedly the quickest and closest non-permanent shaving method in existence, in the hands of an expert. In essence, it was an extremely fine air-blown abrasive that scoured off the hairs without harming the skin. Certainly the skin felt like nothing more than the gentle pressure of what might have been an air stream.

     However, Biron felt queasy about it. There was the well-known legend, or story, or fact (whatever it was), about the incidence of face cancer being higher among the Tyranni than among other cultural groups, and some attributed this to the Tyranni shave spray. Biron wondered for the first time if it might not be better to have his face completely depilated. It was done in some parts of the Galaxy, as a matter of course. He rejected the thought. Depilation was permanent. The fashion might always shift to mustaches or cheek curls.

From THE STARS, LIKE DUST by Isaac Asimov (1951)

(ed note: Captain Randall has been in suspended animation for about a thousand years. After being recalled to life, he is given a room complete with a house robot to serve him.)

      When he awoke it was barely dawn, but a steaming cup of tea appeared on a small table by the bed before he had finished rubbing the sleep out of his eyes.
     ‘Good morning, sir. You slept well?’
     ‘Very well, thank you.’ He looked at the tea. ‘Do you drink this stuff now?’
     ‘You mean mankind, sir? No, the laboratories had to build that up from basics. Is it to your liking?’
     Randall sipped cautiously. ‘Not bad. Can you do the same with coffee?’
     ‘Oh, yes, sir. Mankind still drinks coffee.’
     Randall finished the tea and put the cup down. ‘Can I get a shave anywhere?’
     ‘Shave? Yes, sir, if you’ll lie still … excellent. There we are, sir.’
     Randall ran his hand over a perfectly smooth chin and scowled. ‘Just how?’
     ‘Growth inhibitor, sir. I understand it’s some sort of high frequency sonic device which not only causes the bristles to break off, sir, but also inhibits root growth. Should last you about six months, sir. After-shave?’

From THE TIME MERCENARIES by Philip E. High (1968)

Thus at thirty—Avalonian reckoning—Christopher Holm was tall, slender, but wide-shouldered. In features as well as build, he took after his mother: long head, narrow face, thin nose and lips, blue eyes, mahogany hair (worn short in the style of those who do much gravbelt flying), and as yet not enough beard to be worth anything except regular applications of antigrowth enzyme. His complexion, naturally fair, was darkened by exposure. Laura, a G5 star, has only 72 percent the luminosity of Sol and less ultraviolet light in proportion; but Avalon, orbiting at a mean distance of 0.81 astronomical unit in a period of 0.724 Terran, gets 10 percent more total irradiation than man evolved under.

From THE PEOPLE OF THE WIND by Poul Anderson (1973)

Cleaning Hab Interior

Keeping the habitat module clean is also a challenge. Water is limited, water does not clean things very well in free fall, and the limited atmosphere prevents one from using any alternate cleanser that it toxic or has a disagreeable odor.

Last time I checked on the International Space Station they clean surfaces by swabbing them with a biocide based on an iodine solution. They are looking into a biocide based on a silver ion solution.

And as mentioned elsewhere, any free floating garbage tends to accumulate on the air-intake vents. The vents on the Skylab space station quickly became quite disgusting with random bits of rotting food and dust particles.



The crews of any aerospace vehicle will generate particulate matter from their bodies and their clothing. Equipment also releases particulates. In a weightless state this debris will float in the cabin until it is entrained by the ventilation gas or is separated and captured by a surface (such as a crewman's lungs). Of course, the ventilation gas and filters will remove most of the debris; however, some spaces in the cabin will tend to accumulate floating debris due to a lack of sufficient ventilation. Therefore, on long duration missions (of one or more weeks) a vacuum cleaner should be provided to collect this material—which may include viable microorganisms and the media necessary for growth.

If the vehicle is provided with a pneumatic collection system for urine and/or feces, the fan used for this purpose can also be used to draw gas into a small debris collection bag. This bag can be made from the same material as the fecal collection bag. A gas flow rate of 5 ft3/min is adequate for this purpose.

A personal grooming device-vacuum cleaner is provided on a branch of the control air circuit of the waste management unit. This collects hair, nail clippings, shaving clippings, etc. Collection bags are provided to dry and store the wastes.


(ed note: The Christmas Bush is a Fractal Robot. Tiny parts can be separated to be small robots "sub-motiles")

Now, let me show you some of its other tricks." He reached into his shirt pocket and pulled out a pressurized ball-point pen. He then unbuttoned his shirt front and used the pen to push out a bit of lint from behind a button-hole. He kicked over to a nearby wall and deliberately made an ink mark on the wall. As he kicked back, he let loose the bit of lint into the air. As he came to a halt back with the group, they watched as two tiny segments of the Christmas Branch detached from one of the arms. The smaller one, a minuscule cluster of cilia not much bigger than the bit of lint, flew rapidly through the air with a humming sound like that of a mosquito, captured the floating ball, and flew out the door to another part of the ship, zig-zagging as it went.

"It's picking up other bits of dust on its way to the dust-bin," explained David. "They're too small for us to see, but its little laser radars picked them up from their backscatter."

The larger sub-motile jumped from the Christmas Branch to the wall, and like a spider, used its fine cilia to cling to the wall and walk over to the ink smudge. The cilia scraped the ink out of the wall pores and formed it into a drying ball. The wall now clean, a sub-section of the spider detached and swam off through the low gravity, while the remainder of the spider jumped back to the Christmas Branch where it resumed its normal place.

"Yet housekeeping is a continual chore, so don't be surprised if you see a mosquito flying through the air or a spider walking across the ceiling. They will just be collecting all the dirt and dust you've made that day."

The Christmas Bush was busy weaving cloth using a bright green artificial thread that it had reconstituted from the lint fibers it had collected over the past years.

From ROCHEWORLD by Robert Forward (1982)

One of the shipboard roaches woke Lindsay by nibbling his eyelashes. With a start of disgust, Lindsay punched it and it scuttled away.

... He shook another roach out of his red-and-silver jumpsuit, where it feasted on flakes of dead skin.

He got into his clothes and looked about the gym room. Two of the Senators were still asleep, their velcro-soled shoes stuck to the walls, their tattooed bodies curled fetally. A roach was sipping sweat from the female senator's neck.

If it weren't for the roaches, the (spacecraft) Red Consensus would eventually smother in a moldy detritus of cast-off skin and built-up layers of sweated and exhaled effluvia. Lysine, alanine, methionine, carbamino compounds, lactic acid, sex pheromones: a constant stream of organic vapors poured invisibly, day and night, from the human body. Roaches were a vital part of the spacecraft ecosystem, cleaning up crumbs of food, licking up grease.

Roaches had haunted spacecraft almost from the beginning, too tough and adaptable to kill. At least now they were well-trained. They were even housebroken, obedient to the chemical lures and controls of the Second Representative. Lindsay still hated them, though, and couldn't watch their grisly swarming and free-fall leaps and clattering flights without a deep conviction that he ought to be somewhere else. Anywhere else.

(ed note: Alistair Young calls those "cleaning roaches")

From SCHISMATRIX PLUS by Bruce Sterling (1996)

      Tivk: I require your assistance immediately.
     Chief: What's the problem?
     Tivk: There is a creature in my quarters.
     Chief: What kind of critter? Why didn't ya call security? Sound an alert!
     Tivk: It is not an exceptionally large creature. Be careful!
     Chief: I don't see no …

     Nok: This is going to be good.
     Mukh: And how.

     Chief: Are you outta your alien skull?
     Tivk: Medically impossible.
     Chief: That's a Chinch. It's supposed to be there. It keeps yer digs clean.
     Tivk: I do not desire a Terran symbiote. Please dispose of it.
     Chief: We use the critters to keep our quarters clean. The little fella won't hurt you.

     Mukh: And they look delicious!!
     Chief: Don't be eating the symbiote, froggy. Listen here, beanpole, deal with the critter yourself or let him be. Cuz I ain't hurting a little Chinch. Why don't you ask your entourage here to chase him out?
     Tivk: They are being spectacularly unhelpful.
     Nok: You thought I'd miss this?
     Mukh: Not very likely.

     Spacecraft of any tech level eventually become filthy. An enclosed environment with a bunch of humans will soon develop a funk all its own. Most household dust is 70% human skin flakes so dusting is still required. Add to this all the effluvia of eating and living and the many crawlspaces, ventilator shafts and heating ducts and you're talking about a gigantic petri dish capable of space travel.
     Enter the Chinch. The Chinch comes from Chinchilla stock with a minor bit of genetic tweaking to produce a lower birthrate and greater resistance to toxins and radiation. Chinch's retain the heavy fur coats of their wild forebears. Crew can install prefab Chinch houses in various out of the way places and let a family of Chinches lose. The creatures will crawl all over the place eating anything remotely edible. The creatures were bred to have a strong aversion to the taste of plastics and other insulating materials. Chewing through wires is not an issue.
     Chinches operate unseen during sleep periods on most ships. Moving around they tireless lap up liquids and eat crumbs while their fur whisks away dust and grime. Back in the Chinch hole the creatures groom each other removing the detritus.
     Although they were intended as a cheap maintenance solution many crews name their Chinches, create elaborate Chinch housing and otherwise treat the animals like pampered pets.

     Chief: All I'm saying is I'm a graduate of Advanced Tactics school. I completed EVA Ops training with honors. I'm trained on servicing and flying shuttles. You get what I'm driving at here?
     Tivk: I am quite sure your training will prove adequate … It is attacking! Is it venomous?
     Chief: Oh fer … here. I got the big ole alien monster.

     Mukh: You going to eat that all by yourself?

     Chief: … I don't understand why you're so freaked out by it. They keep the ship spic and span. They're harmless. Some crew even make pets of them. I think Jenn has one.
     Tivk: They have waste. They eliminate like all animals, possibly where I may come into contact with said wastes.
     Chief: Oh why didn't you say so? No worries.
     Tivk: Oh?
     Chief: Nah. We got little robots programmed to follow them around and clean their crap up.

     Tivk: … I hate you all.

From INFESTATION! by Rob Garitta (2015)

Vermin Control

Once space travel matures to the point where spacecraft are regularly traveling between locations with habitable environments, the ships will tend to become infested with vermin. Rats and cockroaches invaded seagoing vessels about five minutes after ships were invented. And after thousands of years they are still a problem. Spacecraft are highly unlikely to be free of the problem, unless ships are single-use items and only travel to airless worlds.

And we all know how indestructible roaches and rats are. Atomic radiation just slows them up a little. Only slightly less invulnerable are bed bugs.

Possible solutions include fanatical cleaning of the habitat module, periodic temporary removal of the hab module's breathable atmosphere to create vacuum, Ship's cat or other animals, and tiny hunter-killer robots.

If vacuum doesn't finish them off you have a real problem. You might have to go to the next level and flood the place with poison gas/insecticide. The trouble with that is purging the module of the poison afterwards so it doesn't kill the crew. And how tense things will get if an emergency crops up right in the middle of the gassing.

But if radiation mutates the vermin to the point where they actually become intelligent, well you are truly up sewage pulsar with no gravity generator.


Star Trek: Mission to Horatius
In this incredibly tedious Star Trek novel the starship Enterprise has been on such a prolonged mission that Dr. McCoy is worried that the crew is starting to suffer from "space cafard", a future version of the cafard which was endemic to the old French Foreign Legion. The crew is heading for shore leave at Starbase 12, when to their disgust they are abruptly ordered to check out a distress call in a boondocks solar system.

About this time Lieutenant Sulu's pet rat Mickey escapes. Later a random crew member chuckles that he just saw Mickey in the corridor, and the funny rat looked like it was dancing. Both McCoy and Sulu turn the color of library paste (white with fear). McCoy bolts back to Sick Bay while Sulu explains that dancing was a symptom of a rat who had Bubonic Plague. Egads.

The rat leads the crew on a merry chase over the next few weeks, while McCoy worriedly tells Captain Kirk that Bubonic Plague is so ancient that the medical records do not list the cure. Finally they give up on half measures, put the entire crew in space suits, and flood the Enterprise with poison gas. Lieutenant Uhuru writes "The Ballad of Mickey the Space Rat" and performs it for the crew.

The valiant crew then successfuly completes the mission. Space cafard starts setting in again. And suddenly Mickey reappears, dancing away.

The crew freaks out, grimly determined that they are not going to spend their shore leave quarantined on board. A level by level search finally corners Mickey, who is shot by about thirteen phaser-bolts simultaneously. His body is vaporized.

Privately, Dr. McCoy comes clean to Captain Kirk. Mickey did not have the plague, this was all a ruse to fight space cafard. McCoy taught Mickey how to dance, and held him in an oxygen tent while the ship was being gassed. And yes, the medical records do contain the cure for Bubonic Plague, you fell for it Captain.
Plague Ship by Andre Norton
This is the second novel of Norton's Solar Queen series about the dangerous uncertain life of an interstellar free trader, living in the shadows of the megacorporation trade companies in an hand-to-mouth existence.

Due to events recounted in the prior Solar Queen novel, the free traders were given compensation in the form of another (late) free trader's trade rights to the planet Sargol. The cat-people there have a few odd types of perfume for trade. Not very profitable, certainly nothing to attract the attention of the megacorporations.

However, the dear departed free trader had discovered on his last trip something called Koros gemstones. A small pouch of these beauties had almost caused a riot among the bidding gem merchants at an inner planet trading mart. Incredibly valuable. And more than enough to bring the megacorporations sniffing around.

The traders of the Solar Queen finally manage to obtain some Koros stones, after they discover the cat-people of Sargol love catnip even more that the ship's cat. A representative of the Inter-Solar megacorporation appears, becoming very annoyed to find the Solar Queen. Inter-Solar was hoping to poach some stones before the Queen showed up. The crew of the Queen is suspicious, the I-S man seems to be up to something nefarious.

A few days on the trip back home to Terra, the crew starts falling sick. Headaches, then falling into a coma. They fear it is some sort of plague, but then the medic notices small puncture wounds. The ship's cat does not catch anything, but the captain has a weird pet called a Hoobat (a nightmare combination of crab, parrot and toad). It manages to lure out of hiding some Sargolian chameleon insects with coma-inducing stingers. The Hoobat can make a hypnotic noise (by rubbing its claws together) which attracts the insects. It seems that the last load of perfume wood from Sargol had been seeded with the bugs by the I-S man.

When the Solar Queen leaves hyperspace and approaches Terra, they find that I-S has spread the word far and wide that the free trader is a plague ship, and should be quarantined. At least long enough for I-S to clean Sargol out of all its Koros stones. Hilarity ensues but our heroes manage to triumph over the evil megacoporations.

(ed note: The crew of the commercial freighter starship Tinker rescues another ship imperiled by malfunctioning carbon-dioxide scrubbers. They rescue the crew and the passengers, but it would make repairs so much easier if they could replace the deadly CO2 poisoned air with breathable air.)

Chief Gerheart turned to her counterpart. “How long would it take you to vent and replenish your air?”

“Three or four stans (standard hours). As long as we’re suited up, we can flush it with nitrogen and keep hull pressure without having to worry about vacuum damage.”

Greta grinned. “The Verminator Protocol.”

Green grinned back. “Exactly.”

Periodically ships needed to do a complete fumigation to rid themselves of the odd stowaway vermin that had followed man into space. That was usually done by flushing all the breathable air from the ship and filling it with nitrogen gas, sometimes laced with a fungicide. It was usually done with the ship docked and the crew safely ashore. There wasn’t anything that would prevent it from being used in this situation, so long as the people aboard were suited and supplied with oxygen. The nitrogen would push all the carbon dioxide laden air out and would, in turn, be replaced with a clean mixture.


      A recent run to Zaonia resulted in a tet crab female coming onboard and laying a clutch of eggs. She died at the pincers and palps of her voracious children since she’d already eaten their father. At that point the young went into hiding and began maturing or being eaten by their siblings.

     Luch the steward’s cat, Rockit was in charge of vermin control. Being a young cat he assumed the Profit Rockit was his ship. It was named after him after all. Since the humans had their uses he let them remain. At the moment the situation was developing he entered the lower hold, which was nearly empty. That was why he spotted the tet crab so easily. The other reason was she was an arrogant young crab that considered the ship her property and ate whoever disputed it.
     Rockit attempted a pouncing maneuver, but came up short when four pincers began snapping in his face. The two began circling, Rockit hissing, the crab whistling. The commotion brought Luna, the ship’s dog.

     Luna was an anomaly. The ship already had a cat for pest control and anti-hijacking apps for security. She was really not needed. But, when was a dog ever really needed unless you were herding or hunting? All that mattered was that Skipper the deckhand wanted her and after a great deal of fuss she was allowed to keep Luna.
     Luna still had a lot of puppy in her but was an exceptional dog, even in Rockit’s opinion, considering she’d learned to use the ladders on the ship by herself. Rockit still didn’t think much of her of course since he was a cat.
     Luna saw Rockit and the pinchy thing with many legs circling and went for it. Dogs have an innate loyalty but even their biggest fans admit they have no sportsmanship. Luna came at the thing from the side hoping for a quick kill but the crab had several more eyes and very good peripheral vision and Luna got a pincer clamped onto her muzzle. Her fur saved her from laceration but it still hurt like blazes. She tried shaking the tet crab off and the crab’s pincer caught Rockit by the tail as the cat turned to get out of the way.

     Canine, crustacean, and feline did a sad and painful dance on the deck, like a small tornado with pincers and fur. The commotion brought Skipper and Luch. Luch immediately ran to his cat’s aid and stomped the alien intruder.
     The crab latched onto Luch’s slipper-clad foot with a free pincer. Skipper fled as the steward joined the dance. At this point Captain and Sandoval arrived. Sandoval was the first to climb the ladder to the deck and found herself at floor level with a whirling ball of feet and pincers. She did what any good spacer would do, screamed like a little girl and got the hell out of their way. Captain was next up the ladder and he dodged the falling Second Tier Navigator.

     Captain was a Zaonian and Zaonians don’t knuckle under. This one almost did. Then he heaved himself up onto the deck and began seeking a weapon. That was when Skipper came down the ladder from the upper with Captain’s revolver sidearm. She took careful aim fired and missed completely, the bullet burying itself in a deckplate. Captain grabbed the revolver from her before she could ruin another gravity generator, gripped it by the barrel and attempted to pistol whip the tet crab.

     Tet crabs also don’t knuckle.

(ed note: I will note in passing that holding a sidearm by the barrel and using it as a hammer is an outstanding way to shoot yourself)

     Vermin on ocean going ships is a given. The same will most likely be true of space going ships. Both afford plenty of small dark places to hide and edibles. Unlike terrestrial ocean going rats and roaches any SF pests may have to adapt to the environment and diet of the ship's crew. there's not going to be any fluorine or levo-protein based life on a human ship for example. But then most SF settings ave a lot of planets with compatible environments and biologies. And the player characters thought this was for their convenience. Heh heh.

     On the other hand vermin breed rapidly, otherwise they aren't vermin. A bear rummaging in your pantry isn't vermin, it's an animal encounter. Rapid breeders may adapt quickly as subsequent generations grow in unusual conditions. A good example of this is the flea. Fleas could cover the earth in a month unchecked and breed so rapidly using the same toxins against them for more than a couple of months can result in them becoming immune. Your crew's referred methods of dealing with pests may become useless at the worst time.

     A bear is probably less destructive to a ship than most vermin. Roaches, rats and such can not only make your galley fail a health inspections, they can destroy wiring, including warning sensors. As for fouling a galley think of telling a high-passenger that you all have to eat prepackaged rations on your next trip out because you failed a health inspection.

     There are many and numerous methods of pest control. The Tech Level 0 solution is a cat. Cats are pound for pound very efficient little killers (just ask one). Dogs generally speaking come in a far second, unless your crew is savvy enough to get breeds that were bred for ratting, like terriers. Then again some aliens pests might make a ship's mascot earn hazard pay. Genemodded cats and dogs are also possible. I wouldn't get any pets cybernetic enhancements. I wouldn't trust a cat with laser eyes and a dog wth laser eyes would take its begging to a whole new level. Just step away from the pot roast.

     There are many and numerous poisons and traps doing a web search for pest control can give all manner of devices. Checking out an exterminator's web page could give plenty of ideas and they generally give you cogent reasons why you should leave the pest control to professionals.

     Some starports, of course, will seal and bug bomb your ships for a reasonable rate. Reasonable to the folks who sell you a ton of the most common element in the universe for 500 cr. that is.

     Of course space is not an ocean. One resource spacecraft al have easy access to is vacuum (sometimes the access is too easy but by then the pests are very far down your list of concerns!) Lifting a ship and opening the airlocks is pretty cheap. Of course it requires the crew and any passengers have spacesuits or survival bubbles. Remember you can shove two middle passengers in a survival bubble but high passengers get their own. this also will not likely win you repeat business but in the example above, tet crabs might make a few minutes in a bubble time well spent.

     Vacuum will also get into places poison will not and it pretty much kills everything outright, unless you have some really hardcore pests. Just make sure the cats and dogs are safe as well as any fresh foods or other commodities that will not react well to vacuum, like bottled wine. Also make sure there are no pests hiding out in the pressurized cages and cargo pods.

     A far future sort of pest might be destructive nanites. Heinlein help you. Immune to vacuum, breeds like mad and might have a go at eating everything. You might have to shut everything down and drop an EMP bomb or buy some hunter killer nanites.

     Uncharitable type may note many of these ideas apply to stowaways.

From ALL CREATURES BITEY AND SMALL by Rob Garitta (2017)


Be that as it may, the real peril may not be from macroscopic pests at all. Microorganisms could be much more serious. Even if they were not being carried by plague rats.

If you are lucky the mutant germs are just a new kind of plague.

If you ain't, you might be dealing with the functional equivalent of the Andromeda Strain or Mutant 59: The Plastic Eaters (i.e., a plague capable of destroying all life or all technology on a planet). The medical service may order your spacecraft intercepted with a nuclear warhead, which may or may not help matters.


Gerald was an exobiologist, a student of life off the planet Earth. The flaw, of course, was that there wasn’t any life beyond Earth. Except, of course, such Earth-evolved life that continued to evolve even off planet. Every human being, every plant, every animal brought along to the Settlements carried microscopic life-forms by the billions.

Anywhere humans went, viruses, bacteria, and other microbes, disease-causing and benign, traveled as well. Normal medical practice was enough to keep most of the nasties at bay inside the sealed colonies—but some microbes escaped the domes, tunnels, ships and habitats to the outside environments. Virtually all of them died the moment they left the controlled environment. But a few survived. And of those survivors, a very few managed to reproduce, and evolve, often at a ferocious rate.

Earth-derived microbes lurked in the soil around Martian cities, living off dome leakages of air, moisture and organics; lived inside the rock of mining asteroids, dining on a witches’ brew diet of complex hydrocarbons; lived as mildew-like patches in airlocks all over the Solar System, absorbing air, moisture and bits of organic matter whenever the locks were pressurized, encysting when they went into vacuum.

A divine hand that worked in mysterious and sometimes horrifying ways. For a few, a terrifying few, of the outsider organisms came back inside the domes and the spacecraft. Most such Returnees were wiped out by the drastically different environment, but some readapted to life back inside. That was when terror struck. Hardened by their generations outside air, light and pressure, some Returnee organisms bred hellaciously back inside, carrying in their genes the ability to digest unlikely things. Plastics, metal, resin compounds, semiorganic superconductors. And some of them, ancestors of disease organisms, retained the ability to infect the human body.

There were microorganisms that could cause disease in humans and also eat through pressure suits and air domes from the inside. Or dissolve the superconducting wires of power grids. Or jam valves in fusion systems.

From THE RING OF CHARON by Roger MacBride Allen (1990)


If the dire dice of destiny land on you with both sixes down, your vermin infestation might turn out to be a super-vermin infestation. The classic example is the xenomorph from the Alien movie. But in novels, it usually takes the form of rats or something have have mutated to the extent that they actually become intelligent.

With super-vermin, the ship's captain tends to stop thinking about venting the ship to vacuum and more about initiating self-destruct.

The Imperial Starships Lenin and MacArthur travel on a first contact mission to the alien Motie planet. Cruiser MacArthur will do the contacting, the battleship Lenin will allow no aliens anywhere near it and has orders to destroy the MacArthur if it is captured. We will take no chances with the existence of the human race, thank you very much.

The Moties have sub-species. One of them is called the "watchmakers", they are semi-intelligent miniature Moties and are used by Motie engineers as sort of mobile tools. They are very clever and breed like rabbits. I think you can see where this is going.

The MacArthur accepts a breeding pair, who promptly escape and disappear into the duct work. The anti-rat ferrets are worthless and the watchmakers are too good at hiding for humans to find. So the crew vents the entire atmosphere to vacuum and figure the problem is solved. The crew does not realize that watchmakers can make their own pressure-tight hab modules.

It isn't until a few weeks later that Captain Blaine realizes they are still infested with the beasties, who are busy reengineering the entire ship. The crew tries to exterminate the watchmakers with a frontal assault with laser handguns, but are defeated by a combination of watchmaker counter-attack and unexpectedly redesigned ship systems that do not operate quite the way they used to.

The crew is evacuated to the Lenin but are only allowed to board after being strip-searched. Especially after they have to fight off a few animated space suits full of watchmakers. The Lenin destroys the MacArthur, which takes an inordinate amount of time since the watchmakers have drastically improved the MacArthur defensive force fields.

The Motie aliens do not have a problem with watchmakers because [A] their watchmakers are not feral so they can order them around to a limited extent and [B] Moties don't care if their ships are redesigned while in flight.

(ed note: The interstellar grain starship has a rat problem. Worse: the rats near the ship's hull have their germ plasm mutated by cosmic radiation. Over the rat-generations they evolve into intelligence. They live in the between-hull areas of the ship, in tribes with spear and knife level of technology.

Shriek has managed to conquer all the tribes and has become the leader of the rats. His wife Wesel is a telepath, and has managed to read the mind of one of the human crew. This was prophesied as "The End", the Ragnarok of the rats. )

      “Shriek!” Wesel’s voice was grave. “We must return at once to the People. We must warn the People. The Giants are making a sorcery to bring the End."
     “The great, hot light ?”
     "No. But wait! First I must tell you of what I learned. Other wise, you would not believe. I have learned what we are, what the world is. And it is strange and wonderful beyond all our beliefs.
     “What is Outside?” She did not wait for his answer, read it in his mind before his lips could frame the words. “The world is but a bubble of emptiness in the midst of a vast piece of metal, greater than the mind can imagine. But it is not so! Outside the metal that lies outside the Outside there is nothing. Nothing! There is no air.” (the "Outside" is the ship's hull. It is a skin of metal lined with insulation. The nothing is deep space.)
     “But there must be air, at least.”
     “No. I tell you. There is nothing.
     “And the world—how can I find words? Their name for the world is—ship, and it seems to mean something big going from one place to another place. And all of us—Giants and People—are inside the ship. The Giants made the ship.”
     “Then it is not alive ?”
     “I cannot say. They seem to think that it is a female. It must have some kind of life that is not life. And it is going from one world to another world.”
     “And these other worlds?”
     “I caught glimpses of them. They are dreadful, dreadful. We find the open spaces of the Inside frightening—but these other worlds are all open space except for one side.”

(ed note: the "Inside" is the area within the hull, the open spaces are rooms. The rats find the rooms frightening because they live in narrow tunnels they made in the hull insulation. Planets are all open spaces except for the ground)

     “But what are we?” In spite of himself, Shriek at least half believed Wesel's fantastic story. Perhaps she possessed, to some slight degree, the power of projecting her own thoughts into the mind of another with whom she was intimate. "What are we?”
     She was silent for the space of many heartbeats. Then: “Their name for us is—mutants. The picture was … not clear at all. It means that we—the People—have changed. And yet their picture of the People before the change was like the Different Ones before we slew them all.
     “Long and long ago—many hands of feedings—the first People, our parents’ parents’ parents, came into the world. They came from that greater world—the world of dreadful, open spaces. They came with the food in the great Cave-of-Food (grain cargo bay)—and that is being carried to another world (the rat ancestors arrived in grain cargo cannisters loaded into the starship for transport to another planet).
     “Now, in the horrid, empty space outside the Outside there is—light that is not light. And this light—changes persons (space radiation causes mutations). No, not the grown person or the child, but the child before the birth (radiation does not mutate you, it mutates your future offspring). Like the dead and gone chiefs of the People, the Giants fear change in themselves. So they have kept the light that is not light from the Inside.
     “And this is how. Between the Barrier (inner hull) and the Far Outside (space) they filled the space with the stuff in which we have made our caves and tunnels (insulation and radiation shielding). The first People left the great Cave-of-Food, they tunneled through the Barrier and into the stuff Outside. It was their nature. And some of them mated in the Far Outside caves. Their children were—Different.”
     “That is true,” said Shriek slowly. “It has always been thought that children born in the Far Outside were never like their parents, and that those born close to the Barrier were—”
     “Now, the Giants always knew that the People were here, but they did not fear them. They did not know our numbers, and they regarded us as beings much lower than themselves. They were content to keep us down with their traps and the food-that-kills (rat poison). Somehow, they found that we had changed. Like the dead chiefs they feared us then—and like the dead chiefs they will try to kill us all before we conquer them.”
     “And the End?”
     “Yes, the End.” She was silent again, her big eyes looking past Shriek at something infinitely terrible. “Yes,” she said again, “the End. They will make it, and They will escape it. They will put on artificial skins that will cover Their whole bodies, even Their heads (spacesuits), and They will open huge doors in the … skin of the ship (airlocks), and all the air will rush out into the terrible empty space outside the Outside. And all the People will die.”
     “I must go," said Shriek. “I must kill the Giants before this comes to pass."
     “No! There was one hand of Giants (five human crew)—now that you have killed Fat-Belly there are four of them left. And they know, now, that they can be killed. They will be watching for you.
     “Do you remember when we buried the People with the sickness? That is what we must do to all the People. And then when the Giants fill the world with air again from their store we can come out.” (the insulating foam will expand in the vacuum and may trap pockets of air that the rats can survive in until pressure is restored)

(ed note: a few rats survive the depressurization, but are later killed by the great, hot light. Shriek manages to kill all but one of the humans. The sole survivor realizes that they have a Rise of the Planet of the Apes situation on their hands, and dives the ship into a nearby sun in order to save humanity)

From GIANT KILLER by A. Bertram Chandler (1945)

      “It’s more than a legend," said Sam Halden, biologist. The reaction was not unexpected — non-humans tended to dismiss the data as convenient speculation and nothing more. “There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel—and yet each planetary race can interbreed with a minimum of ten others! That’s more than a legend—one hell of a lot more!”
     “It is impressive,” admitted Taphetta. “But I find it mildly distasteful to consider mating with someone who does not belong to my species.”
     “That’s because you’re unique,” said Halden. “Outside of your own world, there’s nothing like your species, except superficially, and that’s true of all other creatures, intelligent or not, with the sole exception of mankind. Actually, the four of us here, though it’s accidental, very nearly represent the biological spectrum of human development.
     “Emmer, a Neanderthal type and our archeologist, is around the beginning of the scale. I’m from Earth, near the middle, though on Emmer’s side. Meredith, linguist, is on the other side of the middle. And beyond her, toward the far end, is Kelburn, mathematician. There’s a corresponding span of fertility. Emmer just misses being able to breed with my kind, but there’s a fair chance that I’d be fertile with Meredith and a similar though lesser chance that her fertility may extend to Kelburn.”
     Taphetta rustled his speech ribbons quizzically. “But I thought it was proved that some humans did originate on one planet, that there was an unbroken line of evolution that could be traced back a billion years.”
     “You’re thinking of Earth,” said Halden. “Humans require a certain kind of planet. It’s reasonable to assume that, if men were set down on a hundred such worlds, they’d seem to fit in with native life-forms on a few of them. That’s what happened on Earth; when Man arrived, there was actually a manlike creature there. Naturally our early evolutionists stretched their theories to cover the facts they had.
     “But there are other worlds in which humans who were there before the Stone Age aren’t related to anything else there. We have to conclude that Man didn’t originate on any of the planets on which he is now found. Instead, he evolved elsewhere and later was scattered throughout this section of the Milky Way.”
     “And so, to account for the unique race that can interbreed across thousands of light-years, you’ve brought in the big ancestor,” commented Taphetta dryly. “It seems an unnecessary simplification.”
     “Can you think of a better explanation?” asked Kelburn. “Something had to distribute one species so widely and it’s not the result of parallel evolution not when a hundred human races are involved, and only the human race.”

(ed note: from old Big Ancestor ruins they figure the average height was about forty feet. Which implies that the Big Ancestors used genetic engineering to make themselves into six-foot tall human colonists.)

     “You’ve heard of the adjacency mating principle?” asked Sam Halden.
     “Vaguely. Most people have if they’ve been around men.”
     “We’ve got new data and are able to interpret it better. The theory is that humans who can mate with each other were once physically close. We’ve got a list of all our races arranged in sequence. If planetary race F can mate with race E back to A and forward to M, and race G is fertile only back to B, but forward to O, then we assume that whatever their positions are now, at once time G was actually adjacent to F, but was a little further along. When we project back into time those star systems on which humans existed prior to space travel, we get a certain pattern. Kelburn can explain it to you.”
     Kelburn went to the projector. “It would be easier if we knew all the stars in the Milky Way, but though we’ve explored only a small portion of it, we can reconstruct a fairly accurate representation of the past.”
     He pressed the controls and stars twinkled on the screen. “We’re looking down on the plane of the Galaxy. This is one arm of it as it is today and here are the human systems.” He pressed another control and, for purposes of identification, certain stars became more brilliant. There was no pattern, merely a scattering of stars. “The whole Milky Way is rotating. And while stars in a given region tend to remain together, there’s also a random motion. Here’s what happens when we calculate the positions of stars in the past.”
     Flecks of light shifted and flowed across the screen. Kelburn stopped the motion.
     “Two hundred thousand years ago,” he said.
     There was a pattern of the identified stars. They were spaced at fairly equal intervals along a regular curve, a horseshoe loop that didn’t close, though if the ends were extended, the lines would have crossed.
     Taphetta rustled. “The math is accurate?”
     “As accurate as it can be with a million-plus body problem.”
     “And that’s the hypothetical route of the unknown ancestor?”
     “To the best of our knowledge,” said Kelburn. “And whereas there are humans who are relatively near and not fertile, they can always mate with those they were adjacent to two hundred thousand years ago!”
     “The adjacency mating principle. I’ye never seen it demonstrated,” murmured Taphetta, flexing his ribbons. “Is that the only era that satisfies the calculations?”
     “Plus or minus a hundred thousand years, we can still get something that might be the path of a spaceship attempting to cover a representative section of territory,” said Kelburn. “However, we have other ways of dating it. On some worlds on which there are no other mammals, we’re able to place the first human fossils chronologically. The evidence is sometimes contradictory, but we believe we’ve got the time right.”
     Taphetta waved a ribbon at the chart. “And you think that where the two ends of the curve cross is your original home?”
     “We think so,” said Kelburn. “We’ve narrowed it down to several cubic light-years — then. Now it’s far more. And, of course, if it were a fast-moving star, it might be completely out of the field of our exploration. But we’re certain we’ve got a good chance of finding it this trip."

     “Hydroponics is your job. There’s nothing I can do.” Halden paused thoughtfully. “Is there something wrong with the plants?”
     “In a way, I guess, and yet not really.”
     “What is it, some kind of toxic condition?”
     “The plants are healthy enough, but something’s chewing them down as fast as they grow.”
     “Insects? There shouldn’t be any, but if there are, we’ve got sprays. Use them.”
     “It’s an animal,” said Firmon. “We tried poison and got a few, but now they won’t touch the stuff. I had electronics rig up some traps. The animals seem to know what they are and we’ve never caught one that way.”
     Halden glowered at the man. “How long has this been going on?”
     “About three months. It’s not bad; we can keep up with them.” It was probably nothing to become alarmed at, but an animal on the ship was a nuisance, doubly so because of their pilot.
     “Tell me what you know about it,” said Halden.
     “They’re little things.” Firmon held out his hands to show how small. “I don’t know how they got on, but once they did, there were plenty of places to hide.” He looked up defensively. “This is an old ship with new equipment and they hide under the machinery. There’s nothing we can do except rebuild the ship from the hull inward.”
     Firmon was right. The new equipment had been installed in any place just to get it in and now there were inaccessible corners and crevices everywhere that couldn’t be closed off without rebuilding. They couldn’t set up a continuous watch and shoot the animals down because there weren’t that many men to spare. Besides, the use of weapons in hydroponics would cause more damage to the thing they were trying to protect than to the pest. He’d have to devise other ways.

     He looked from Halden to Emmer and back again. “The hydroponics tech tells me you’re contemplating an experiment. I don’t like it.”
     Halden shrugged. “We’ve got to have better air. It might work.”
     “Pests on the ship? It’s filthy! My people would never tolerate it!”
     “Neither do we.”
     The Ribboneer’s distaste subsided. “What kind of creatures are they?”
     “I have a description, though I’ve never seen one. It’s a small four-legged animal with two antennae at the lower base of its skull. A typical pest.”
     Taphetta rustled. “Have you found out how it got on?”
     “It was probably brought in with the supplies,” said the biologist. “Considering how far we’ve come, it may have been any one of a half a dozen planets. Anyway, it hid, and since most of the places it had access to were near the outer hull, it got an extra dose of hard radiation, or it may have nested near the atomic engines; both are possibilities. Either way, it mutated, became a different animal. It’s developed a tolerance for the poisons we spray on plants. Other things it detects and avoids, even electronic traps.”
     “Then you believe it changed mentally as well as physically, that it’s smarter?”
     “I’d say that, yes. It must be a fairly intelligent creature to be so hard to get rid of. But it can be lured into traps, if the bait’s strong enough.”

(ed note: They finally catch a few of the vermin chewing on the hydroponics plants by using traps baited with tiny knives just the right size for vermin's hands with opposable thumbs. The vermin were not interested in other bait.)

     Clumsy, but because it had a thumb, it could handle such tools as a knife.
     He had made an error there. He had guessed the intelligence, but he hadn’t known it could use the weapon he had put within reach. A tiny thing with an inchlong knife was not much more dangerous than the animal alone, but he didn’t like the idea of it loose on the ship.
     The metal knife would have to be replaced with something else. Technicians could compound a plastic that would take a keen edge for a while and deteriorate to a soft mass in a matter of weeks. Meanwhile, he had actually given the animal a dangerous weapon—the concept df a tool. There was only one way to take that away from them, by extermination. But that would have to wait.
     Fortunately, the creature had a short life and a shorter breeding period. The actual replacement rate was almost neglible. In attaining intelligence, it had been short-changed in fertility and, as a consequence, only in the specialized environment of this particular ship was it any menace at all.
     They were lucky; a slightly higher fertility and the thing could threaten their existence. As it was, the ship would have to be deverminized before it could land on an inhabited planet.

(ed note: They finally find the origin planet of the Big Ancestor. It is deserted, the cities are empty, all the possessions and artifacts are missing. They do find a document. After lots of computer work the document is translated. The crew assembles to listen to the translation.)

     The translator coughed, stuttered and began.
     “We have purposely made access to our records difficult. If you can translate this message, you’ll find, at the end, instructions for reaching the rest of our culture relics. As an advanced race, you’re welcome to them. We’ve provided a surprise for anyone else.
     “For ourselves, there’s nothing left but an orderly retreat to a place where we can expect to live in peace. That means leaving this Galaxy, but because of our life span, we’re capable of it and we won’t be followed.”
     “At the time we left,” the message continued, “we found no other intelligent race, though there were some capable of further evolution. Perhaps our scout ships long ago met your ancestors on some remote planet. We were never very numerous, and because we move and multiply so slowly, we are in danger of being swept out of existence in the foreseeable future. We prefer to leave while we can. The reason we must go developed on our own planet, deep beneath the cities, in the underworks, which we had ceased to inspect because there was no need to. This part was built to last a million generations, which is long even for us.”
     Emmer sat upright, annoyed at himself. “Of course! There are always sewers and I didn’t think of looking there!”
     “In the last several generations, we sent out four expeditions, leisurely trips because we then thought we had time to explore thoroughly. With this planet as base of operations, the successive expeditions fanned out in four directions, to cover the most representative territory.”
     “After long preparation, we sent several ships to settle one of the nearer planets that we’d selected on the first expedition. To our dismay, we found that the plague was there—though it hadn’t been on our first visit!”
     Halden frowned. They were proving themselves less and less expert biologists. And this plague there had to be a reason to leave, and sickness was as good as any—but unless he was mistaken, plague wasn’t used in the strict semantic sense. It might be the fault of the translation.
     “The colonists refused to settle: they came back at once and reported. We sent out our fastest ships, heavily armed. We didn’t have the time to retrace our path completely, for we’d stopped at innumerable places. What we did was to check a few planets, the outward and return parts of all four voyages. In every place, the plague was there, too, and we knew that we were responsible.
     “We did what we could. Exhausting our nuclear armament, we obliterated the nearest planets on each of the four spans of our journeys.”
     “I wondered why the route came to an end,” crinkled Taphetta, but there was no comment, no answer.
     “We reconstructed what had happened. For a long time, the plague had lived in our sewers, subsisting on wastes (much like rats). At night, because they are tiny and move exceedingly fast, they were able to make their way into our ships and were aboard on every journey. We knew they were there, but because they were so small, it was difficult to dislodge them from their nesting places. And so we tolerated their existence.”
     They weren’t so smart,” said Taphetta. “We figured out that angle long ago. True, our ship is an exception, but we havn’t landed anywhere, and won’t until we deverminize it.”
     “We didn’t guess that next to the hull in outer space and consequently exposed to hard radiation,” the message went on, “those tiny creatures would mutate dangerously and escape to populate the planets we landed on. They had always been loathsome little beasts that walked instead of rolling or creeping, but now they became even more vicious, spawning explosively and fighting with the same incessant violence. They had always harbored diseases which spread to us, but now they’ve become hothouses for still smaller parasites that also are able to infect us. Finally, we are now allergic to them, and when they are within miles of us, it is agony to roll or creep.”
     Taphetta looked around. “Who would have thought it? You were completely mistaken as to your origin.” Kelburn was staring vacantly ahead, but didn’t see a thing. Meredith was leaning against Halden; her eyes were closed. “The woman has finally chosen, now that she knows she was once vermin,” clicked the Ribboneer. “But there are tears in her eyes.”
     “The intelligence of the beast has advanced slightly, though there isn’t much difference between the highest and the lowest — and we’ve checked both ends of all four journeys. But before, it was relatively calm and orderly. Now it is malignantly insane.”

(ed note: in other words, the various human races are not descendants of the Big Ancestor. They are descendants of the the vermin plague. Humans are rats.)

From BIG ANCESTOR by F. L. Wallace (1954)

(ed note: A dreaded Qul-En alien scout is one of many searching for a source of a hormone needed by the Qul-En race. It lands on Terra, and quickly determines that the hormone is common in Terran mammals in general, and in human brains in particular. The scout roams a remote area in a vehicle disguised as a mountain lion, killing and dissecting animals. It soon determines that Terra will be a prime spot to harvest human beings to extract the needed hormone from their brains.

Unfortunately for the scout, like an idiot it left the door of its flying saucer open, letting the bugs in...)

For a time it did; there was certainly no disturbance at the ship. The small silvery vessel was safely hidden. There was a tiny, flickering light inside—the size of a pin-point—which wavered and changed color constantly where a sort of tape unroled before it. It was a recording device, making note of everything the roaming pseudo-mountain-lion’s eyes saw and everything its microphonic ears listened to. There was a bank of air-purifying chemical which proceeded to regenerate itself by means of air entering through a small ventilating slot. It got rid of carbon dioxide and stored up oxygen in its place, in readiness for further voyaging.

Of course, ants explored the whole outside of the space-vessel, and some went inside through the ventilator opening. They began to cart off some interesting if novel foodstuff they found within. Some very tiny beetles came exploring, and one variety found the air-purifying chemical refreshing. Numbers of that sort of beetle moved in and began to raise large families. A minuscule moth, too, dropped eggs lavishly in the nest-like space in which the Qul-En explorer normally reposed during space-flight. But nothing really happened.

The Qul-En in the lion shape had been vastly pleased to find the sought-for hormone in another animal besides a mountain lion. The dissection job was a perfect anatomical demonstration; no instructor in anatomy could have done better, and few neuro-surgeons could have done as well with the brain. It was, in fact, a perfect laboratory job done on a flat rock in the middle of a sheep-range, and duly reproduced on tape by a flickering, color-changing light. The reproduction, however, was not as good as it should have been, because the tape was then covered by small ants who had found its coating palatable and were trying to clean it off.

This time it wasn’t a rabbit; it was a coyote. It had been killed and most painstakingly taken apart to provide at a glance all significant information about the genus canis, species latrans, in the person of an adult male coyote. It was a most enlightening exhibit; it proved conclusively that there was a third type of animal, structurally different from both mountain-lions and rabbits, which had the same general type of nervous system, with a mass of nerve tissue in one large mass in a skull, which nerve-tissue contained the same high percentage of the desired hormone as the previous specimens. Had it been recorded by a tiny colored flame in the hidden ship—the flame was now being much admired by small red bugs and tiny spiders—it would have been proof that the Qul-En would find ample supplies on Earth of the complex hormone on which the welfare of their race now depended.

This was dictated to the pin-point flame, and the flame faithfully wavered and changed color to make the record. But the tape did not record it; a rather large beetle had jammed the tape-reel. It was squashed in the process, but it effectively messed up the recording apparatus. Even before the tape stopped moving, though, the record had become defective; tiny spiders had spun webs, earwigs got themselves caught. The flame, actually, throbbed and pulsed restlessly in a cobwebby coating of gossamer and tiny insects. Silverfish were established in the plastic lining of the Qul-En ship; beetles multiplied enormously in the air-refresher chemical; moth-larvae already gorged themselves on the nest-material of the intrepid explorer outside. Ants were busy on the food-stores. Mites crawled into the ship to prey on their larger fellows, and a praying-mantis or so had entered to eat their smaller ones. There was an infinite number of infinitesimal flying things dancing in the dark; larger spiders busily spun webs to snare them, and flies of various sorts were attracted by odors coming out of the ventilator opening, and centipedes rippled sinuously inside...

Then the mountain-lion, which was not a mountain-lion, went bounding through the night toward its hidden ship.

Within an hour, it clawed away the brush from the exit-port, crawled inside, and closed the port after it. As a matter of pure precaution, it touched the “take-off” control before it even came out of its vehicle.

The ventilation-opening closed—very nearly. The ship rose quietly and swiftly toward the skies. Its arrival had not been noted; its departure was quite unsuspected.

It wasn’t until the Qul-En touched the switch for the ship’s system of internal illumination to go on that anything appeared to be wrong. There was a momentary arc, and darkness. There was no interior illumination; ants had stripped insulation from essential wires. The lights were shorted. The Qul-En was bewildered; it climbed back into the mountain-lion shape to use the infrared-sensitive scanning-cells.

The interior of the ship was a crawling mass of insect life. There were ants and earwigs, silverfish and mites, spiders and centipedes, mantises and beetles. There were moths, larvae, grubs, midges, gnats and flies. The recording-instrument was shrouded in cobweb and hooded in dust which was fragments of the bodies of the spiders’ tiny victims. The air-refresher chemicals were riddled with the tunnels of beetles. Crickets devoured plastic parts of the ship and chimed loudly. And the controls—ah! the controls! Insulation stripoed of here; brackets riddled or weakened or turned to powder there. The ship could rise, and it did. But there were no controls at all.

The Qul-En went into a rage deadly enough to destroy the insects of itself. The whole future of its race depended on the discovery of an adequate source of a certain hormone. That source had been found. Only the return of this one small ship fifteen feet in diameter—was needed to secure the future of a hundred-thousand-year-old civilization. And it was impeded by the insect-life of the planet left behind! Insect-life so low in nervous organization that the Qul-En had ignored it!

The ship was twenty thousand miles out from earth when the occupant of the mountain-lion used its ray-beam gun to destroy all the miniature enemies of its race. The killing beam swept about the ship. Mites, spiders, beetles, larvae, silverfish and flies—everything died. Then the Qul-En crawled out and began to make repairs, furiously. The technical skill needed was not lacking; in hours, this same being had made a perfect counterfeit of a mountainiion to serve it as a vehicle. Tracing and replacing gnawed-away insulation would be merely a tedious task. The ship would return to its home planet; the future of the Qul-En race would be secure. Great ships, many times the size of this, would flash through emptiness and come to this planet with instruments specially designed for collecting specimens of the local fauna. The cities of the civilized race would be the simplest and most ample sources of the so desperately needed hormone, no doubt. The inhabitants of even one city would furnish a stop-gap supply. In time—why—it would become systematic. The hormone would be gathered from this continent at this time, and from that continent at that, allowing the animals and the civilized race to breed for a few years in between collections. Yes...

The Qul-En worked feverishly. Presently it felt a vague discomfort; it worked on. The discomfort increased; it could discover no reason for it. It worked on, feverishly...

Out in space, the silvery ship suddenly winked out of existence. Enough of its circuits had been repaired to put it in overdrive. The Qul-En was desperate, by that time. It felt itself growing weaker, and it was utterly necessary to reach its own race and report the salvation it had found for them. The record of the flickering flame was ruined. The Oul-En felt that itself was dying. But if it could get near enough to any of the planetary systems inhabited by its race, it could signal them and all would be well.

Moving ever more feebly, the Qul-En managed to get lights on within the ship again. Then it found what it considered the cause of its increasing weakness and spasmodic, gasping breaths. In using the killing-ray it had swept all the interior of the ship. But not the mountain-lion shape. Naturally! And the mountain-lion shape had killed specimens and carried them about. While its foreleg flamed, it had even rolled on startled, stupid sheep. It had acquired fleas—perhaps some from Salazar—and ticks. The fleas and ticks had not been killed; they now happily inhabited the Qul-En.

The Qul-En tried desperately to remain alive until a message could be given to its people, but it was not possible. There was a slight matter the returning explorer was too much wrought up to perceive, and the instruments that would have reported it were out of action because of destroyed insulation. When the ventilation-slit was closed as the ship took off, it did not close completely; a large beetle was in the way. There was a most tiny but continuous leakage of air past the crushed chitinous armor. The Qul-En in the ship died of oxygen-starvation without realizing what had happened, just as human pilots sometimes black out from the same cause before they know what is the matter. So the little silvery ship never came out of overdrive. It went on forever, or until its source of power failed.

The fleas and ticks, too, died in time; they died very happily, very full of Qul-En body-fluid. And they never had a chance to report to their fellows that the Qul-En were very superior hosts.

From NOBODY SAW THE SHIP by Murray Leinster (1950)

Temperature Regulation

NASA directs that the temperature inside a habitat module should be from 291.5 K to 299.8 K with the nominal temperature 295.2 K. That's 18.4°C ⇒ 22°C ⇒ 26.7°C in metric (and 65°F ⇒ 72°F ⇒ 80°F for those poor benighted folk still using Imperial)

NASA assumes that each astronaut emits 11.82 MJ of heat per day.

This is the job of the Spacecraft Thermal Control Systems.

Temperature inside the habitat module is prevented from getting too cold by hull thermal insulation (to prevent the internal heat from escaping), and by adding heat from sources such as electrical resistance heaters.

Temperature inside the habitat module is prevented from getting too hot by hull thermal insulation (to prevent heat from the sun from entering), and by removing heat using heat radiators. In the TransHab design, it needs approximately 96 kilograms of heat radiators and internal thermal equipment per person.

Radiation Shielding

Radiation shielding has its own separate page.

You want to limit the acute dose of radiation to under 0.1 Grays, and the astronaut career chronic dose to under 4.0 Sieverts.

What this boils down to is supplying the habitat module with a small radiation shielded room called a storm cellar or biowell. It will need radiation shielding to the tune of 500 grams per square centimeter of surface. Since this very expensive in terms of mass, storm cellars will be as small as the designers think they can get away with. With the restriction that all the crew has to physically fit inside, and they might have to shelter there for several days.

If the spacecraft has a fission, fusion, or antimatter power plant or propulsion system, it will require an anti-radiation shadow shield to protect the crew.

If the spacecraft is a combat spacecraft who will have to face radiation from nuclear warheads and particle beam weapons, it is going to require lots of very massy armor.

Artificial Gravity

Supplying artificial gravity has its own separate page.

It is unknown what the minimum amount of artifical gravity is required for health. The only data we have are for 1.0 g on Terra, 437 days in 0.0 g in the ISS, and a few hours at 0.16 g for the Apollo lunar vists. NASA limits astronauts on the International Space Station to 180 day visits.

So, for instance, if the minimum required gravity for health is above 0.4 g, Martian colonists living on the ground will still need regular visits to the centrifuge.

Pretty much all the reports I could find on the subject conclude with something like "I have no idea, more research is needed."

Effects of prolonged microgravity include:

A centrifuge would provide gravity to prevent these dire medical effects, but they are a major pain to attach to a spacecraft.

A possible compromise is the personal centrifuge. This is a centrifuge a few meters long, just big enough for one man to strap in, spin up about 30 RPM, and do some exercises. Yes, this will probably give them severe motion sickness, but it will only be for the duration of the exercise period. This will only help some but not all of the damage done to the body by microgravity.

It is tempting to just forget about spin gravity, and just have everybody float around while the ship is not under thrust. One can be an optimist and assume future medical advances will discovere treatment for all the hideous effects. Marshall Savage suggests electro stimulation therapy of the muscles (Ken Burnside says rocket crewmen will have to wear their "jerk-jammies" when they sleep). One would hope that a medical cure will be found for the nausea induced by free fall, or "drop sickness" (they say that the first six months are the worse).

But the only way to guarantee 100% freedom from all of the nasty medical effects is with full 1 g artificial gravity.

Some of the body’s systems adapt to the environment of space quicker than others. This figure represents how quickly each system adapts to microgravity.

The bottom line is the 1g setpoint, or normal gravity level on Earth for each system. The middle line is called the 0g setpoint, or the level each system obtains once it adapts to microgravity in space. The setpoints for 1g and 0g are different, and so it takes some time to adapt. The top line is called the clinical horizon and it is the point that problems in performance can occur.

As you can see, the neurovestibular system is the first to change. This system is responsible for assessing what direction the body is moving. When this system is not functioning properly, motion sickness can occur. You can see at first, there is a high peak for this system, indicating clinical problems. However, after a few days, this peak disappears, and the system adapts to space travel and has a stable value at the 0g setpoint.

You can see it takes the other systems, such as the muscular system, longer to adapt. On the figure, the muscular system is represented in part by the line labeled “lean body mass”. Lean body mass refers to the mass of the body which is not composed of fat. You can see on the figure that lean body mass eventually reaches a stable value at Og although it does take some time. In addition, the value at Og is less than that at 1g, indicating a loss in lean body mass with space flight.

Some systems, such as bone, don’t adapt to spaceflight. The bone system never reaches a stable value at 0g gravity, but instead continues to climb towards the clinical horizon.

From Marc E. Tischler

Countermeasures thus far have addressed the symptoms in a piecemeal fashion, rather than the underlying cause. For example, high-impact strength training may slow the decline of muscle and bone mass, but it does nothing to mitigate the damage to vision from increased fluid pressure in the eyeballs. Dietary and pharmaceutical countermeasures are fraught with complexity and the risk of unintended side effects — further complicated by the fact that weightlessness itself changes the body’s absorption of and reaction to drugs. Adding calcium to the diet to preserve bone structure is not very effective when the bones are leaching out the calcium they already have due to their lack of mechanical stress. (On Earth, that stress triggers a piezoelectric effect that regulates the growth of bone where it’s needed [Chaffin 1984], [Mohler 1962], [Woodard 1984].) On the contrary, calcium supplements are likely to increase the concentration of calcium in the blood and urinary tract, with a concomitant risk of developing kidney stones.

Artificial gravity via rotation — centrifugation — is the only practical countermeasure that addresses the underlying cause, rather than a subset of symptoms, of the health decline due to gravity deprivation. It’s still not known whether some threshold of gravity less than 1 g would be adequate to stave off the decline. Except for a few hours by a few men on the Lunar surface, there is a dearth of human experience in anything between 0 g and 1 g.

To the extent that a health risk is attributable to gravity deprivation, we don’t need to understand the intricate why’s and how’s to have confidence that restoring gravity will mitigate the risk. Whatever gravity’s effects might be, one can travel from Seattle to Sydney knowing that as long as the gravity in each locale is essentially the same there should be no gravitydeprivation illness or injury.

[Chaffin 1984] Chaffin, Don B.; Andersson, Gunnar B. J. Occupational Biomechanics (p. 25). John Wiley and Sons, Inc.
[Mohler 1962] Mohler, Stanley R. (1962 May). "Aging and Space Travel." In, Aerospace Medicine (vol. 33, p. 594597). Aerospace Medical Association.
[Woodard 1984] Woodard, Daniel; Oberg, Alcestis R. (1984). "The Medical Aspects of a Flight to Mars" (AAS 81239). In P. J. Boston (Ed.), The Case for Mars (AAS Science and Technology Series, vol. 57, p. 173180). American Astronautical Society

(ed note: Sadler is an accountant, temporarily assigned to the observatory on the moon. He is actually also an amateur secret agent, trying to track down an outer planet agent who is leaking info to the other colonies, but we won't get into that. Sadler is taking his first trip to the lunar Central City.)

      Your job's making you cynical, Sadler told himself. Let's see what Central City has in the way of entertainment.
     He'd just missed a tennis tournament in Dome Four, which should have been worth watching. It was played, so someone had told him, with a ball of normal size and mass. But the ball was honeycombed with holes, which increased its air-resistance so much that ranges were no greater than on earth. Without some such subterfuge, a good drive would easily span one of the domes. However the trajectories followed by these doctored balls were most peculiar, and enough to induce a swift nervous breakdown in anyone who had learned to play under normal gravity.
     There was a cyclorama in Dome Three, promising a tour of the Amazon Basin (mosquito bites optional), starting at every alternate hour. Having just come from Earth, Sadler felt no desire to return so promptly. Besides, he felt he had already seen an excellent cyclorama display in the thunderstorm that had now passed out of sight. Presumably it had been produced in the same manner, by batteries of wide-angle projectors.

     The attraction that finally took his fancy was the swimming pool in Dome Two. It was the star feature of the Central City gymnasium, much frequented by the Observatory staff. One of the occupational risks of life on the Moon was lack of exercise and resultant muscular atrophy. Anyone who stayed away from Earth for more than a few weeks felt the change of weight very severely when he came home. What lured Sadler to the gym, however, was the thought that he could practice some fancy dives that he would never dare risk on Earth, where one fell five meters in the first second arid acquired far too much kinetic energy before hitting the water.
     Dome Two was on the other side of the city, and as Sadler felt he should save his energy for his destination he took the subway. But he missed the slow-speed section which led one off the continuously moving belt, and was carried willy-nilly on to Dome Three before he could escape. Rather than circle the city again, he retraced the way on the surface, passing through the short connecting tunnel that linked all the domes together at the points where they touched. There were automatic doors here that opened at a touch—and would seal instantly if air-pressure dropped on either side.
     Half the Observatory staff seemed to be exercising itself in the gym. Dr. Molton was sculling a rowing machine, one eye fixed anxiously on the indicator that was adding up his strokes. The chief engineer, eyes closed tightly as per the warning instructions, was standing in the center of a ring of ultra-violet tubes which gave out an eerie glare as they replenished his tan. One of the M. D.'s from Surgery was attacking a punchbag with such viciousness that Sadler hoped he would never have to meet him professionally. A tough-looking character who Sadler believed came from Maintenance was trying to see if he could lift a clear ton; even if one allowed mentally for the low gravity, it was still awe-inspiring to watch.

     Everybody else was in the swimming pool, and Sadler quickly joined them. He was not sure what he had expected, but somehow he had imagined that swimming on the Moon would differ drastically from the same experience on the Earth. But it was exactly the same, and the only effect of gravity was the abnormal height of the waves, and the slowness with which they moved across the pool.
     The diving went well as long as Sadler attempted nothing ambitious. It was wonderful to know just what was going on, and to have time to admire the surroundings during one's leisurely descent. Then, greatly daring, Sadler tried a somersault from five meters. After all, this was equivalent to less than a meter on Earth.
     Unfortunately, he completely misjudged his time of fall, and made half a turn too many—or too few. He landed on his shoulders, and remembered too late just what a crack one could give oneself even from a low height if things went wrong. Limping slightly, and feeling that he had been flayed alive, he crawled out of the pool. As the slow ripples ebbed languidly away, Sadler decided to leave this sort of exhibitionism to younger men.

From EARTHLIGHT by Arthur C. Clarke (1955)

Dianne Steiger sucked on her bulb of coffee and considered just how much she hated zero gee. Not for herself, mind. After an adult lifetime spent in spacecraft of one sort or another, a shift from this gravity to that meant little to her. The medical problems caused by zero gee were no great challenge, either, if people paid attention and took care of themselves—and she made quite certain that everybody on a ship of hers took care of themselves. Zero-gee debilitation was to spaceflight as scurvy had been to sea travel five or six hundred years before—completely preventable, and fatal all the same, for anyone fool enough not to take precautions.

It was the headaches that zero gee caused in managing the ship. Terra Nova had been designed for operation either in zero gee or in roll mode, rotating along her long axis to produce artificial gravity via the centrifugal effect. The TN could function either way, but roll mode was preferred for almost everything on board, from drinking coffee to flushing the toilets, from pumping coolant to controlling the ship’s thermal load. There were ways to do everything in no-grav, but most of them were awkward and inconvenient, work-arounds rather than straightforward procedures.

From THE SHATTERED SPHERE by Roger MacBride Allen (1994)

Deadly Dust

Lunar dust is ubiquitous and insidious. And it will kill you.


Harmful effects of lunar dust

A 2005 NASA study listed 20 risks that required further study before humans should commit to a human Mars expedition, and ranked "dust" as the #1 challenge. The report urged study of its mechanical properties, corrosiveness, grittiness, and effect on electrical systems. Most scientists think the only way to answer the questions definitively is by returning samples of Martian soil and rock to Earth well before launching any astronauts.

Although that report addressed Martian dust, the concerns are equally valid concerning lunar dust. The dust found on the lunar surface could cause harmful effects on any human outpost technology and crew members:

  • Darkening of surfaces, leading to a considerable increase in radiative heat transfer;
  • Abrasive nature of the dust particles may rub and wear down surfaces through friction;
  • Negative effect on coatings used on gaskets to seal equipment from space, optical lenses, solar panels, and windows as well as wiring;
  • Possible damage to an astronaut's lungs, nervous, and cardiovascular systems.

The principles of astronautical hygiene should be used to assess the risks of exposure to lunar dust during exploration on the Moon's surface and thereby determine the most appropriate measures to control exposure. These may include removing the spacesuit in a three-stage airlock, "vacuuming" the suit with a magnet before removal, and using local exhaust ventilation with a high–efficiency particulate filter to remove dust from the spacecraft's atmosphere.

The harmful properties of lunar dust are not well known. However, based on studies of dust found on Earth, it is expected that exposure to lunar dust will result in greater risks to health both from direct exposure (acute) and if exposure is over time (chronic). This is because lunar dust is more chemically reactive and has larger surface areas composed of sharper jagged edges than Earth dust. If the chemical reactive particles are deposited in the lungs, they may cause respiratory disease. Long-term exposure to the dust may cause a more serious respiratory disease similar to silicosis. During lunar exploration, the astronauts' spacesuits will become contaminated with lunar dust. The dust will be released into the atmosphere when the suits are removed. The methods used to mitigate exposure will include providing high air recirculation rates in the airlock, the use of a "Double Shell Spacesuit", the use of dust shields, the use of high–grade magnetic separation, and the use of solar flux to sinter and melt the regolith.

From the Wikipedia entry for LUNAR SOIL

      The Apollo Moon missions of 1969-1972 all share a dirty secret. “The major issue the Apollo astronauts pointed out was dust, dust, dust,” says Professor Larry Taylor, Director of the Planetary Geosciences Institute at the University of Tennessee. Fine as flour and rough as sandpaper, Moon dust caused ‘lunar hay fever,’ problems with space suits, and dust storms in the crew cabin upon returning to space.

     The trouble with moon dust stems from the strange properties of lunar soil. The powdery grey dirt is formed by micrometeorite impacts which pulverize local rocks into fine particles. The energy from these collisions melts the dirt into vapor that cools and condenses on soil particles, coating them in a glassy shell.

     These particles can wreak havoc on space suits and other equipment. During the Apollo 17 mission, for example, crewmembers Harrison “Jack” Schmitt and Gene Cernan had trouble moving their arms during moonwalks because dust had gummed up the joints. “The dust was so abrasive that it actually wore through three layers of Kevlar-like material on Jack’s boot,” Taylor says.

     To make matters worse, lunar dust suffers from a terrible case of static cling. UV rays drive electrons out of lunar dust by day, while the solar wind bombards it with electrons by night. Cleaning the resulting charged particles with wet-wipes only makes them cling harder to camera lenses and helmet visors. Mian Abbas of the National Space Science and Technology Center in Huntsville, Alabama, will discuss electrostatic charging on the moon and how dust circulates in lunar skies.

     Luckily, lunar dust is also susceptible to magnets. Tiny specks of metallic iron (Fe0) are embedded in each dust particle’s glassy shell. Taylor has designed a magnetic filter to pull dust from the air, as well as a “dust sucker” that uses magnets in place of a vacuum. He has also discovered that microwaves melt lunar soil in less time than it takes to boil a cup of tea. He envisions a vehicle that could microwave lunar surfaces into roads and landing pads as it drives, and a device to melt soil over lunar modules to provide insulation against space radiation. The heating process can also produce oxygen for breathing.

     But the same specks of iron that could make moon dust manageable also pose a potential threat to human health, according to Bonnie Cooper at NASA’s Johnson Space Center. “Those tiny blebs of pure iron we see on the surface of lunar grains are likely to be released from the outside edges of the particle in the lungs and enter the bloodstream,” she says. Preliminary studies suggest that the inhalation of lunar dust may pose a health hazard, possibly including iron toxicity. Members of NASA’s Lunar Airborne Dust Toxicity Advisory Group, Cooper, Taylor, and colleagues are studying how moon dust affects the respiratory system. They plan to set a lunar dust exposure standard by 2010, in time for NASA engineers to design a safer and cleaner trip to the Moon.


In space, they say, no one can hear you sneeze. But Apollo 17 astronaut Harrison Schmitt was doing a lot of that inside the Challenger command module when he visited the moon in 1972.

One day, after a lunar walk, Schmitt accidentally breathed in some of the abundant moon dust that he and his commander had tracked back in to the Challenger living quarters. For a full day, Schmitt suffered from what he described as "lunar hay fever." His eyes watered, his throat throbbed, and he broke into a sneezing fit.

No, Schmitt wasn't allergic to the moon. NASA scientists now understand that pieces of moon dust — especially the smallest, sharpest particles — pose clear health risks to astronauts. A recent study published in the April issue of the journal GeoHealth examined exactly how dangerous that dust can be on a cellular level — and the results are as ominous as the dark side of the moon. In several lab tests, a single scoop of replica moon dust proved toxic enough to kill up to 90 percent of the lung and brain cells exposed to it.

A dusty dilemma

Dust on the moon behaves a little differently than dust on Earth. For starters, it's sharp. Because there's no wind on the moon, the dust never erodes. Instead, grains of moon dust — which are largely the products of micrometeorite impacts — remain sharp and abrasive and can easily slice into an astronaut's lung cells if breathed in too deeply.

On top of this, moon dust can float. With no atmosphere to protect the moon from constant bombardment by solar winds and the charged particles they carry, lunar soil can become electrostatically charged like clothing with static cling.

"This charge can be so strong that the soil particles actually levitate above the lunar surface," the authors wrote in the new study.

From there, it's easy enough for dust to cling in the nooks and crannies of an astronaut's spacesuit and follow him or her back inside living quarters. These loose particles can clog sensitive equipment, jam zippers, ruin clothing and — as Schmitt discovered — wreak havoc on the human body if accidentally ingested by astronauts.

Making moon dust

In their new study, a team of researchers from Stony Brook University in New York wanted to find out just how dangerous a lungful of moon dust could really be. Because actual lunar soil is hard to come by on Earth, the team used five Earth-sourced simulants to represent the dust found on various parts of the moon's terrain. The simulants included volcanic ash from Arizona, dust skimmed from a Colorado lava flow and a glassy, lab-made powder designed by the U.S. Geological Survey for use in lunar soil studies like these.

The team gauged the effects of moon dust on human organs by mixing their soil samples directly with human lung cells and mouse brain cells grown in their lab. The scientists ground each soil sample to three different degrees of graininess, the finest of which was just a few micrometers wide (smaller than the width of a human hair) and easily capable of being sucked up into human lungs.

When the team took stock of their cells 24 hours later, they found that every soil type had caused some degree of brain and lung cell death. The finest-grain samples proved most lethal, killing up to 90 percent of the cells that had been exposed to them. Cells that weren't decimated outright showed signs of DNA damage that could lead to cancer or neurodegenerative diseases if not repaired, the researchers wrote.

"Clearly, avoidance of lunar dust inhalation will be important for future explorers," the authors wrote.

But as humans explore the moon in future decades, chance exposures are likely, the researchers wrote.

Fortunately, NASA has taken this problem seriously for a long time and is developing several dust-mitigation methods. One promising strategy: Cover sensitive surfaces with an Electrodynamic Dust Shield — essentially, electrically charged panels that shoot currents through thin wires to zap dust away. Early lab tests have shown that the shields work well, and some sample panels are currently being tested on the International Space Station. Whether the panels could be incorporated into astronauts' spacesuits remain to be seen.


When Neil Armstrong and Buzz Aldrin returned from the moon, their cargo included nearly fifty pounds of rock and soil, which were packed in an aluminum box with seals designed to maintain the lunar surface’s low-pressure environment. But back at Johnson Space Center, in Houston, scientists discovered that the seals had been destroyed—by moon dust.

Lunar dust is fine, like a powder, but it cuts like glass. It’s formed when meteoroids crash on the moon’s surface, heating and pulverizing rocks and dirt, which contain silica and metals such as iron. Since there’s no wind or water to smooth rough edges, the tiny grains are sharp and jagged, and cling to nearly everything.

“The invasive nature of lunar dust represents a more challenging engineering design issue, as well as a health issue for settlers, than does radiation,” wrote Harrison (Jack) Schmitt, an Apollo 17 astronaut, in his 2006 book, “Return to the Moon.” The dust sullied spacesuits and ate away layers of moon boots. Over the course of six Apollo missions, not one rock box maintained its vacuum seal. Dust followed the astronauts back into their ships, too. According to Schmitt, it smelled like gunpowder and made breathing difficult. No one knows precisely what the microscopic particles do to human lungs.

The dust not only coats the moon’s surface, but floats up to sixty miles above it—as part of its exosphere, where particles are bound to the moon by gravity, but are so sparse that they rarely collide. In the nineteen-sixties, Surveyor probes filmed a glowing cloud floating just above the lunar surface during sunrise. Later, Apollo 17 astronaut Gene Cernan, while orbiting the moon, recorded a similar phenomenon at the sharp line where lunar day meets night, called the terminator. Cernan sketched a series of pictures illustrating the changing dustscape; streams of particles popped off the ground and levitated, and the resulting cloud came into sharper focus as the astronauts’ orbiter approached daylight. Since there’s no wind to form and sustain the clouds, their origin is something of a mystery. It’s presumed that they’re made of dust, but no one fully understands how or why they do their thing.

It’s possible that an electrical field forms at the terminator line—where sunlight meets shadow—that could knock dust particles aloft. Mihály Horányi, a physicist at the University of Colorado, in Boulder, has demonstrated that moon dust can indeed respond to such electric fields. But he suspects that the mechanism isn’t strong enough to create and sustain the mysterious, glowing clouds.

From THE MYSTERY OF MOON DUST by Kate Greene (2013)

The instructor made a circular gesture, and two assistants swiveled the EMU on the axis trainer so its back now faced the trainees. The suit’s primary life support pack was surrounded by a rectangular docking collar. One of the assistants opened the pack like a hatchway, revealing the suit’s interior.

“In microgravity, you climb in and out of the EMU while it is docked to the side of the spacecraft. You then close and seal the hatch before undocking from the ship.” (a suitport) He studied the faces of the trainees. “Can anyone tell me why this design is necessary for asteroid-mining operations?”

By now the trainees knew better than to raise their hands.

After a pause the instructor answered for them. “Because asteroid dust is an extreme biohazard. It must never get inside your ship. Asteroid regolith is five times finer than talcum powder, with particles as sharp as broken glass. If breathed in, they can enter your bloodstream directly—resulting in death. If taken into the lungs, they can penetrate deep enough to cause silicosis—stone grinder’s disease—resulting in death. Regolith also sticks to and shorts out circuit boards and jams valves and seals—causing equipment failures that can also lead to death.”

From DELTA-V by Daniel Suarez (2019)

They were called the “dusty dozen” for good reason. The 12 Apollo astronauts who walked on the lunar surface between 1969 and 1972 kicked up so much moondust that the powdery sediment got lodged in every nook and cranny of their space suits. Caked in the stuff, the astronauts inadvertently tracked the toxic dust into their spacecraft and even back down to Earth upon landing.

These NASA astronauts complained of a “lunar hay fever” that irritated their eyes, lungs, and nostrils. A doctor who helped the Apollo 11 crew members emerge from their dust-scattered space module following its ocean splashdown experienced allergic reactions of his own. “Dust is probably one of our greatest inhibitors to a nominal operation on the moon,” Apollo 17 astronaut Gene Cernan, the last man to walk on the moon, said during a postflight debriefing. “I think we can overcome other physiological or physical or mechanical problems, except dust.”

Billowing clouds of dust particles—jagged and abrasive for want of weathering and atmospheric reactions—are hardly the only health hazards posed by a lunar mission, though. Galactic cosmic rays would bombard lunar inhabitants with a steady stream of high-energy radiation. The level of gravity on the moon—about 17 percent that of Earth’s—could wreak havoc on bones, muscles, and other organs. And then there are the psychological aspects of what one NASA astronaut described as the “vast loneliness” of the moon.

As humanity prepares to return to the moon and eventually colonize it, scientists are now actively probing these risks and beginning to devise medical countermeasures. Yet solid evidence on the health consequences of lunar living is extremely limited. “Except for the Apollo experience, we really have no data,” says Laurence Young, a space medicine scientist in MIT’s department of aeronautics and astronautics—and those Apollo missions were never designed with biomedical research goals in mind.

In contrast, the International Space Station (ISS) was established as a giant floating laboratory from the get-go, and nearly two decades of experiments from the continuously inhabited station do offer some clues about what it might be like for people to live on the moon for extended durations. But a zero-gravity space station orbiting within the protective halo of the Earth’s magnetic field is hardly analogous to the moon’s surface, with its partial gravity and harsher radiation.

Researchers therefore have to settle for approximations of lunar conditions. They study proxy dust instead of the real thing, because moondust collected by Apollo astronauts remains scarce. (And even those precious Apollo samples became less reactive after coming into contact with the Earth’s moist, oxygen-rich air.) The researchers simulate galactic radiation by using particle accelerators to create the kinds of energetic heavy ions found in deep space. And they have a variety of tricks to fudge one-sixth gravity: They take parabolic flights that induce short bursts of moonlike conditions; use harnesses and other body-weight support systems to mimic the biomechanics expected in reduced gravity environments; and place subjects in tilted beds for weeks on end to model the effects of lunar gravity on heart function.

The imitations are never perfect, but they are informative. Last year, an interdisciplinary team from Stony Brook University, in New York, exposed human lung cells and mouse brain cells to dust samples that resemble the regolith found in the lunar highlands and on the moon’s volcanic plains. Compared with less-reactive particulate materials, the toxic dust caused more genetic mutations and cell death, raising the specter of moondust triggering neurodegeneration and cancer in future lunar explorers. “The DNA is being damaged, so there is a risk of those types of things happening,” says Rachel Caston, a molecular biologist who led the research. (She’s now at Indiana University–Purdue University Indianapolis.)

But will the same damage happen inside the human body? And if so, would ensuring the safety of future moon settlers require the equivalent of a mudroom, an expensive and logistically challenging piece of equipment to haul over to our celestial neighbor? And just how clean would that mudroom have to be to keep astronauts safe?

“We just don’t know, and therein lies the current conundrum,” says Kim Prisk, a pulmonary physiologist at the University of California, San Diego. “Is this just a nuisance dust, or something potentially very toxic?”

None of the Apollo astronauts suffered any long-term ill effects from dust exposure, only acute respiratory problems—which suggests the lunar schmutz might not be too nasty. But the longest stay on the moon so far was the Apollo 17 astronauts’ 75-hour mission, the equivalent of a long weekend getaway. Plus, with only 12 human data points to draw from, many uncertainties remain. To be on the safe side, when it comes to lunar dust, “a mitigation strategy must be in place before we establish habitats on the lunar surface,” says Andrea Hanson, an aerospace engineer at NASA who previously managed the Exercise Physiology & Countermeasures Lab at Johnson Space Center.


Lunar explorers will have to battle an insidious enemy—dust.

ANOTHER LUNAR DAWN, and the powdery dust on the moon’s surface begins to stir. Without a breath of wind, the finest motes swirl across the ancient landscape as electrostatically charged dust grains repel one another. Larger grains join the dance in a line that stretches more than 3,000 miles from the lunar north pole to the south pole, along the edge of advancing daylight.
Within hours the dance has become frenzied and vertical, with microscopic grains hurtling miles overhead, the tiniest ones flying the farthest, until the weak lunar gravity stops their rise and pulls them back to the dusty surface. Instead of resting there, many jump up to begin the dance anew, surrounding the moon with a veritable atmosphere of dust—glassy, abrasive, toxic grit that could spell “No Trespassing” to future explorers.

Under a cloudless blue Colorado sky, I accompanied seven scientists, a graduate student, and an education specialist as they toiled up the shifting sands of the tallest dunes in North America. At 8,200 feet above sea level, the intense sunlight scorched our skin even though it was October, and in the thin air, the exertion left us panting. The incessant wind quickly smoothed away our footprints. We were in the Great Sand Dunes National Park and Preserve, but it felt as though we were alone on Mars.

And that was the idea.

We were there to study the problems awaiting NASA engineers planning the next generation of lunar outposts and Mars expeditions. Four of the scientists carried miniature Mars rovers that looked like the kind of radio-controlled toy you might find at RadioShack. They had thought about bringing NASA’s one spare of the Sojourner rover from the 1997 Mars Pathfinder expedition, “but the commercial truck chassis were far cheaper,” explained team leader Masami Nakagawa, an associate professor of mining engineering at the Colorado School of Mines in Golden. Each of the model trucks had been modified for this expedition: transmissions geared down, engines souped up, the body of one turned into a rotating auger for digging in the sand.

For two eight-hour days under the broiling sun, scarcely breaking for granola bars or water, the scientists took turns at the radio controls to put the rovers through their paces. The vehicles were sent climbing the steep dunes until half-buried by avalanches, while cameras and a crude duct-tape tape measure (the real thing had disappeared in the soft sand) documented their progress, or lack thereof. “Hey, I think sand and dust finally jammed the transmission!” exulted grad student Jared Reese, holding aloft the auger vehicle, which had finally refused to budge, even with a freshly charged battery.

Celebrating when the equipment stops working? That was in fact the purpose of this NASA-sponsored “Dust-Off”: to court Murphy’s Law. “Over the next two days, our interdisciplinary team can get a direct feel for how invasive dust is,” explained Nakagawa over the first night’s dinner, at the Great Sand Dunes Oasis restaurant. “We want to look at lunar and Martian dust mitigation from a systems engineering viewpoint.”
By “dust,” Nakagawa doesn’t mean house dust. Most of the stuff that collects on furniture is actually organic material like dead human skin cells, pet dander, and pollen grains. For the most part, it’s soft: Wipe it off with a cloth and it won’t scratch polished wood. And it’s usually not thick. Even an attic corner that hasn’t been swept in years can accumulate less than an eighth of an inch.

On Earth, the closest equivalents to lunar and Martian dust are the choking storms that sometimes blow west from the Gobi Desert to blanket Beijing with millions of tons of ultrafine particles. In 1980 powdery volcanic ash fell an inch deep hundreds of miles from Washington’s Mount St. Helens, and “white outs” of alkali gypsum dust swept the Nevada playa just after the 2002 Burning Man arts festival. But even these aren’t good analogs. In terrestrial deserts the atmosphere is too dense, the soils too humid, the plants too numerous, and the weathering from wind and water too prevalent to match conditions on the moon or Mars.

Lunar dust is razor-sharp grit made of inorganic stone and powdered glass. It was formed over hundreds of millions of years by micrometeorites slamming into the moon at high velocities, fracturing lunar rocks into shards and melting the sand into glass. The Apollo astronauts who trod the inches-deep regolith (the preferred term for extraterrestrial dirt) discovered what a nuisance it could be. Wipe a spacesuit’s sun visor, and it scratched the protective layer of gold. Get dust into the spacesuit’s joints, and it fouled the attachments and seals. Try to brush the grit off a spacesuit before reentering the lunar lander, and its sharp edges dug into the fabric. Track it inside the habitat, and it became airborne. Breathe it in and mucous membranes swelled shut (“I didn’t know I had lunar dust hay fever,” commented Apollo 17 geologist-astronaut Jack Schmitt at the time). Go back out, and the graphite-black dust had so darkened the white spacesuits (“Looks like you guys have been playing in a coal bin,” quipped mission control during the Apollo 16 mission) that the fabric absorbed rather than reflected the murderous sunlight, overheating the astronauts’ life support systems.

And that’s just the moon.
On Mars, the dust may be corrosive and poisonous too. Martian soil is expected to be a strong oxidizer (think of powdered bleach or lye) laced with heavy metals such as hexavalent chromium, the carcinogen in the movie Erin Brockovich. It’s also, as engineers operating NASA’s Mars rovers have learned, magnetic. Photographs taken by Spirit and Opportunity show Martian dirt, reddish with oxides of iron, coating magnets on the vehicles. On the moon, glass in the regolith is filled with microscopic beads of pure iron—so-called nanophase iron. In both places the dirt is likely to stick to anything with an electromagnet, including motors and electronics.

A mere two days in the Colorado dunes was enough to convince me of the insidious mechanical challenges that dust will present to future astronauts and their machines. The windborne grit scoured our skin raw, sifted into hair and zippers and shoes, messed up the transmissions of all four rovers, and jammed the buttons of cellular phones.

Even on the airless moon, the dirt doesn’t lie still. Astronauts in lunar orbit aboard the Apollo 8, 10, 15, and 17 spacecraft repeatedly observed and sketched what they variously called “bands,” “streamers,” or “twilight rays” for about 10 seconds before lunar sunrise or sunset. The drawings are reminiscent of the slanting rays that filter up through clouds during sunsets on Earth. Some scientists chalked the phenomenon up to light reflecting from dust suspended above the lunar surface, but others remained unconvinced: Without an atmosphere, how could dust be suspended above the moon? Even if the particles were kicked up by, say, a meteorite impact, they would quickly settle back to the surface.

It wasn’t until last year that Timothy Stubbs and his colleagues at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, came up with an explanation, which they called the “dynamic fountain” model. In a drinking fountain, the arc of water from the spout appears suspended in one position, but the water molecules are constantly in motion. Similarly, according to Stubbs, microscopic grains of lunar dust are constantly leaping from the surface and falling back again due to a weird phenomenon unknown on Earth: electrostatic lofting.

Just as rubbing a balloon against your shirt creates a static charge that can levitate the hair on your head, lunar dust particles with opposite charges will attract each other, and like-charged particles will repel. How does the dust become charged? On the moon’s sunlit side, solar ultraviolet and X-ray radiation beats down relentlessly, knocking electrons from atoms in the lunar soil. The electrons escape into space, and positive charges build up on the lunar surface. The tiniest motes of dust—just a few hundred-thousandths of an inch in size—are repelled from the rest and launched upward, some reaching miles above the surface. Lunar gravity eventually pulls them back down, but electrostatic repulsion kicks them off again. The process is repeated over and over to form a tenuous “atmosphere” of moving dust particles.

The same happens on the lunar far side, which is bombarded by solar wind particles flowing around the moon—except that the net charge is negative since the solar wind is mostly electrons. Data from the 1998 Lunar Prospector mission suggests that the electrical potential might amount to hundreds of volts on the night side, even higher than on the day side, possibly launching dust particles to higher velocities and altitudes.
Evidence supporting the dynamic fountain model may be buried in old data from the Lunar Ejecta and Meteorites experiment, left on the moon by Apollo 17 in 1972. LEAM had three sensors that could record the speed, energy, and direction of tiny particles. The experiment was designed to look for fallout from lunar meteorite impacts, as well as material raining down from comets or interstellar space. But in a classic case of serendipity, “LEAM recorded a high number of particles every lunar sunrise,” recounts Gary Olhoeft, professor of geophysics at the Colorado School of Mines, “mostly from east or west rather than from above, and mostly much slower than expected.” Even stranger, a few hours after every lunar sunrise, LEAM’s temperature rocketed up so high—near that of boiling water—that the instrument had to be turned off because it was overheating. Olhoeft and others now suspect that dust lofted from the moon covered the LEAM, darkening its surface so the experiment package absorbed sunlight rather than reflected it. But nobody knows for sure. LEAM operated only briefly before the Apollo program ended.

Then there are the puzzling rays seen by the Apollo astronauts. Because the specks of dust bouncing around on the moon would be too small to see with the naked eye, explorers on the surface wouldn’t likely notice them. But astronauts on the night side around sunrise might see the moving dust causing the sunlight to scatter, looking like “a weird, shifting glow extending along the horizon, almost like a dancing curtain of light,” according to Stubbs. And at certain times during the lunar cycle, when the moon passes through an active part of Earth’s magnetosphere, Stubbs speculates that “dust would start flying at high velocities”—not at densities that could be seen from Earth, but perhaps in large enough amounts to get into unprotected machinery on the moon.

Last year, in a 77-page report listing 20 risks that required further study before we should commit to a human Mars expedition, NASA’s Mars Exploration Program Analysis Group ranked dust number one. The report urged study of its mechanical properties, corrosiveness, grittiness, and effect on electrical systems. Most scientists think the only way to answer the questions definitively is by returning samples of Martian soil and rock to Earth well before launching any astronauts.

Many also believe a lunar sample return will be necessary. True, the Apollo astronauts brought back some 800 pounds of lunar rocks from six landing sites. But the dust played a dirty trick: The gritty particles deteriorated the knife-edge indium seals of the bottles that were intended to isolate the rocks in a lunar-like vacuum. Air has slowly leaked in over the past 35 years. “Every sample brought back from the moon has been contaminated by Earth’s air and humidity,” Olhoeft says. The dust has acquired a patina of rust, and, as a result of bonding with terrestrial water and oxygen molecules, its chemical reactivity is long gone. The chemical and electrostatic properties of the soil no longer match what future astronauts will encounter on the moon.

To better understand lunar dust, Olhoeft is trying to undo the damage. During the Apollo program six steel vacuum chambers were built, each 10 feet long, that could be pumped down to 10-12 torr—one- trillionth the atmospheric pressure of sea level on Earth—to duplicate the vacuum on the moon. After the Apollo program shut down, five of the giant tanks were scrapped. The remaining chamber, recently refurbished, is in Olhoeft’s laboratory at the Colorado School of Mines. He plans to insert a sample of real lunar dust, pump the pressure down to lunar vacuum, cycle the chamber’s temperature to duplicate the harsh lunar day and night, and bombard the contents with radiation and electrons to try to resuscitate some of its original properties.

At NASA’s Marshall Space Flight Center in Huntsville, Alabama, in a smaller basketball-size vacuum chamber located inside the Dusty Plasma Laboratory, researcher Mian Abbas is running a positively Zen-like experiment. Each morning, he enters the lab and sits down to examine a single speck of lunar dust. For as long as 10 or 12 days at a stretch, he shines an ultraviolet laser onto the particle and painstakingly controls the strength of electric fields until the speck levitates. “Experiments on single grains are helping us understand how lunar dust on the moon can be given an electric charge and lofted to high altitudes,” Abbas explains.

Olhoeft, Stubbs, and others are also mining original Apollo data, such as that from LEAM, in the hope that the unread tapes might yield information useful in designing lunar spacesuits and equipment. It’s easier said than done: Many original computer tapes from Apollo experiments, including ones that were never analyzed, can no longer be read. Not only are some of the data formats obsolete, many of the tapes have degraded due to less-than-optimum storage. Some of the data may be permanently lost. So the dust researchers do what they can. They pore over frame after frame of footage taken by the Apollo astronauts, measuring the trajectory of dust particles kicked up by boots and rover wheels, hoping to better understand the physics. Others, like Bruce Damer of Digital Space in Santa Cruz, California, are building computer models of the dust so that design engineers can test-drive hypothetical digging machines and see what gets clogged.

While these scientists study the dust itself, engineers are coming up with prototype systems for combating it. At the Kennedy Space Center in Cape Canaveral, Florida, Carlos Calle and colleagues in the Electrostatics and Surface Physics Laboratory have demonstrated a device they think can be embedded in spacesuit fabrics to create oscillating electric fields. The rapid shifting of the fields would cause dust particles to hop from electrode to electrode until they get thrown off the suit altogether. An even more imaginative dust-busting concept comes from Lawrence Taylor, a planetary scientist at the University of Tennessee at Knoxville, who describes himself as “one of those weird people who like to stick things in kitchen microwave ovens to see what happens.” When he tried it with a small pile of lunar soil, he found that it melted “lickety split”—within 30 seconds—at only 250 watts of power. The nanophase iron in the dirt concentrated the microwave energy to sinter, or fuse, the loose soil into large clumps. Taylor’s experiment has inspired him to propose machinery for turning bothersome lunar dust into useful solids: rocket landing pads, bricks for habitats, radiation shielding, even roads and radio antenna dishes.

That’s the other thing about dust: It isn’t always bad. On Mars, dust might actually help clean up its own mess. The solar panels on the twin rovers currently on Mars were expected to have been coated long ago with dust that would degrade their power output and bring the mission to a halt. More than once, though, tornado-like dust devils have scoured the panels clean and given the rovers new life.

But that’s the rare bit of good news. Dust storms on Mars will be a serious, continual worry. During Martian summer, daytime highs peak at 68 degrees Fahrenheit, and on these balmy afternoons the planet’s dust devils come alive. These are no little Arizona desert whirlwinds, a few yards across, that pass by in seconds. Martian dust devils are monster columns reaching miles into the sky and nearly half a mile across, 10 times larger than any tornado on Earth. When they pass by, the reddish sand and dust whips around faster than 70 mph, dropping the local visibility to zero for minutes at a time. And they’re everywhere. The Mars rover cameras have filmed them in action, and orbiting spacecraft have spotted their dark tracks all over the planet. “If you were standing next to the Spirit rover midday during Martian summer, you’d see half a dozen [dust devils] at any instant,” says Mark Lemmon, a Mars atmosphere specialist at Texas A & M University in College Station.

The sand in the lower part of a Martian dust devil would be a major hazard. Because the atmospheric pressure on Mars is only one percent of that at sea level on Earth, astronauts won’t feel much wind. But their spacesuits and faceplates would be pinged by high-speed material that would collect in every fold and crevice. Worse, the swirling dust and sand may be electrically charged, to the point of “possibly inducing arcing to a spacesuit or vehicle, and creating electromagnetic interference,” according to William Farrell, one of Stubbs’ colleagues at NASA’s Goddard center.
Farrell has chased dust devils across Arizona deserts and measured their electrical currents. Like levitating lunar dust, the grains of sand and dust become charged as a result of constantly banging into one another. On Mars as well as on Earth, the dust, which can blow in from anywhere, may be quite different from the local sand. When unlike materials rub together (like party balloon and shirt sleeve), one material gives up some of its electrons to the other in what’s known as triboelectric charging (“tribo” means “rubbing”). The smaller dust particles tend to take on a negative charge, having robbed electrons from the larger sand grains.
Triboelectric charging is known to occur on Mars. It came to the attention of NASA engineers building the Sojourner rover for the Mars Pathfinder even before the spacecraft left Earth. When the engineers ran the wheels for a prototype Sojourner over simulated Martian dust in a simulated Martian atmosphere, the model built up a charge of hundreds of volts. That discovery inspired the scientists to add ultrathin half-inch-long tungsten needles at the base of the rover’s radio antennas, to drain any excess charge into the thin Martian air.

Dust devils could even lead to lightning on Mars. All dust devils are powered by a rising central column of hot air, which carries the negatively charged dust upward and leaves the heavier, positively charged sand swirling near the base. The charges become separated, and the separation creates an electric field. In terrestrial dust devils, Farrell has measured electric fields of up to 20,000 volts per meter—peanuts compared to the fields in thunderstorms, where lightning doesn’t flash until the fields become 100 times stronger, enough to break apart air molecules. But 20,000 volts per meter “is very close to the breakdown of the thin Martian atmosphere,” Farrell points out. And because Martian dust devils are so tall, their stored electrical energy can be greater, possibly strong enough to unleash lightning.

Even if lightning doesn’t occur on Mars, the presence of an astronaut or rover might induce local arcing. “You’d have to watch out for corners, where electric fields can get very strong,” Farrell muses. “You might want to make a vehicle or habitat rounded.” And though dust devils can clean off solar panels, astronauts may still find charged dust clinging electrostatically to spacesuits, vehicles, and habitats.

None of these concerns is especially troubling to Apollo 17 astronaut Schmitt. He agrees that dust will be a nuisance for future lunar explorers. But he also expects that engineers will come up with practical solutions like an airlock—which is already being considered for the next-generation lander—that would let astronauts stow their dirty spacesuits before re-entering their living quarters after a moonwalk. “For scientific reasons, the dust is intriguing,” Schmitt says. “It’s a number-one engineering design problem for long-term habitation and settlement [of the moon]. But you protect yourself with a layered defense. The dust is not a problem that should scare us out of going back.”


Between 1969 and the end of 1972, twelve U.S. astronauts kicked up the powdery regolith, the topside dust and rock of the Moon. They were later dubbed the “dusty dozen.” Along with invaluable lunar samples, Apollo moonwalkers brought back a significant message to Earth: The Moon is a Disneyland of dust.

A team led by the University of Colorado Boulder has come up with a potential solution to the problem: one that makes use of an electron beam, a device that shoots out a focused stream of negatively-charged, low-energy particles.

The research group’s early findings suggest that electron-beam dustbusters could be a fixture of Moon bases in the not-too-distant future.

The research has been published recently in the journal Acta Astronautica.

Dust hazards

“Dust mobilized on the lunar surface due to natural processes and/or human activities can readily stick to spacesuits, optical devices, and mechanical components, for example. This may lead to dust hazards that have been considered as one of the technical challenges for future lunar exploration,” they write.

Furthermore, lunar dust poses a health hazard to Moon crews. Apollo 17 lunar module pilot Harrison Schmitt’s exposure resulted in symptoms he described as “lunar hay fever.”

The research team’s new method utilizes an electron beam to charge fine-sized dust particles and shed them off of various surfaces as a result of electrostatic forces.

Jagged and abrasive

To test the idea, a vacuum chamber was loaded with various materials coated in a NASA-made “lunar simulant” designed to mimic lunar dust. After aiming an electron beam at those particles, the dust poured off, usually in just a few minutes.

In their paper, the team reports that an alternative dust removal method using a short wavelength UV light will be also tested in future work.

“Lunar dust is very jagged and abrasive, like broken shards of glass,” said Xu Wang, a research associate in the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder. The problem with lunar dust, he adds, it isn’t anything like the stuff that builds up on bookshelves on Earth.

Moon dust is constantly bathed in radiation from the Sun, a bombardment that gives the material an electric charge. That charge, in turn, makes the dust extra sticky, almost like a sock that’s just come out of the drier. It also has a distinct structure, Wang noted in a CU Boulder press statement.

By using the new technique, “It literally jumps off,” said lead author Benjamin Farr, who completed the work as an undergraduate student in physics at CU Boulder.

Electron beam shower

Study coauthor Mihály Horányi, a professor in LASP and the Department of Physics at CU Boulder, believes the technology has real potential.

NASA has experimented with other strategies for shedding lunar dust, such as by embedding networks of electrodes into spacesuits. An electron beam, however, might be a lot cheaper and easier to roll out, Horányi explains.

Horányi imagines that one day, lunar astronauts could simply leave their spacesuits hanging up in a special room, or even outside their habitats, and clean them after spending a long day kicking up dust outside. The electrons would do the rest. “You could just walk into an electron beam shower to remove fine dust,” he notes.

Other coauthors on the new research include John Goree of the University of Iowa and Inseob Hahn and Ulf Israelsson of the Jet Propulsion Laboratory.

To read the paper – “Dust mitigation technology for lunar exploration utilizing an electron beam” – go to:

Also, go to this video of jumping motes of Moon dust at:


A suitport or suitlock is an alternative technology to an airlock, designed for use in hazardous environments and in human spaceflight, especially planetary surface exploration. Suitports present advantages over traditional airlocks in terms of mass, volume, and ability to mitigate contamination by—and of—the local environment.


Secondly, suitports can eliminate or minimize the problem of dust migration. During the Apollo program, it was discovered that the lunar soil is electrically charged, and adheres readily to any surface with which it comes into contact, a problem magnified by the sharp, barb-like shapes of the dust particles. Lunar dust may be harmful in several ways:

  • The abrasive nature of the dust particles may rub and wear down surfaces through friction.
  • The dust may damage coatings used on gaskets, optical lenses, solar panels, windows, and wiring.
  • The dust may cause damage to an astronaut's lungs as well as nervous and cardiovascular systems, leading to conditions such as pneumoconiosis.

During the Apollo missions, the astronauts donned their space suits inside the Apollo Lunar Module cabin, which was then depressurized to allow them to exit the vehicle. Upon the end of EVA, the astronauts would re-enter the cabin in their suits, bringing with them a great deal of dust which had adhered to the suits. Several astronauts reported a "gunpowder" smell and respiratory and/or eye irritation upon opening their helmets and being exposed to the dust.

When the suit is attached to the vehicle, any dust which may have adhered to the backpack of the suit is sealed between the outside of the backpack and the vehicle-side hatch. Any dust on the suit that is not on the backpack remains sealed outside the vehicle. Likewise, the suitport prevents contamination of the external environment by microbes carried by the astronaut.

From the Wikipedia entry for SUITPORT

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