RocketCat sez

Listen up, space cadets! Here's the deal:

Spaceship and spacestation cabins have air at full pressure. If you use air at low pressure the blasted atmo is pure oxy, which is like swimming in a pool of gasoline while idly flicking your Zippo.

Soft space suits are only terribly encumbering, like wearing three snow suits at once. This is their advantage. Disadvantages include the fact they can be punctured by a pair of kindergarten safety scissors, causing certain death. Oh, and they can only use low pressure because high pressure will make the suit spread-eagle you like a Saint Andrew's Cross. Low pressure means you have to do a few hours of pre-breathing or the suit will kill you with The Bends. Which is a problem if an emergency strikes and you don't have a few hours.

Hard shell space suits advantages are: they can use high pressure atmo so you can't get the bends, you don't need to pre-breathe, and you'd need a freaking handgun to puncture it. Disadvantage is they are monumentally overwhelmingly hideously encumbering like wearing a suit of medieval plate armor made out of solid lead. Soft space suits are only terribly encumbering.

Semi-rigid space suits are a cross between soft and hard shell suits. Like all attempts to have it both ways, it means they have the draw-backs of both and the advantages of neither.

Skintight suits have the advantage of being about as encumbering as a wearing leotards, they are quick to put on, and puncturing them just gives you a space-hickey instead of certain death. Disadvantage is they have to use low pressure so The Bends once again raises its ugly head. Also people have a problem getting anybody to take it seriously ("Aw, c'mon, gimmie a break! Who the heck is your suit designer, Earle K. Bergey? Where's the brass brassière?)

A space suit is a protective garment that prevents an astronaut from dying horribly when they step into airless space.

Also known as atmosphere suit, vac suit, pressure suit, space armor, environment(al) suit, e-suit, EVA suit.

SF author Sir Arthur C. Clarke said "We seldom stop to think that we are still creatures of the sea, able to leave it only because, from birth to death, we wear the water-filled space suits of our skins." SF author Ken MacLeod said that the specification of a human being is "a space suit for a fish."

Current NASA suits look like baggy inflated coveralls with a large back pack and a spherical fishbowl over the head. Often in old illustrations there are accordion bellows at the joints. The accuracy of space suits in science fiction was very much hit or miss. The low budget show Space Academy had "Life Support Bracelets" and the Star Trek Animated series had force-field based "Life Support Belts" as a cheapskate way to avoid the special effect expense of renting or drawing an actual space suit.

NASA astronaut always put on a transdermal dimenhydrinate anti-nausea patch when suiting up in a space suit, in case of drop sickness. The chances of that are slight, but suffocating inside a helmet full of vomit is a nasty way to die.

Most space suits are Full (Body) Pressure-suits: they offer pressurization of the entire body in space for extended periods. Partial (Body) Pressure-suits only pressurize certain parts of the body for a limited time. They are only used as a precaution, worn inside the habitat module during times when there is danger of it springing a leak (such as during lift-off).

Full-(Body) Pressure-suits can be either Low-Pressure (pure oxygen at 32.4 kPa) or High-Pressure (breathing mix at 101.3 kPa, normal Terran atmospheric pressure).

All NASA spacecraft and space station habitat modules are High-Pressure. At least the ones designed after the Apollo 1 tragedy claimed the lives of three astronauts. Ever since NASA has avoided using pure oxygen atmosphere wherever possible, which means using high-pressure.

The problem is if you go from a high-pressure environment (like a habitat module) into a low-pressure environment (like a low-pressure space suit) you run the risk of the bends. To avoid this the astronaut must do pre-breathing for a couple of hours. If you go from a high-pressure habitat module into a high-pressure space suit the bends does not happen. This is why high-pressure space suits are called "zero-prebreathe" suits.

I suppose some space-faring nation could use low-pressure pure-oxygen habitat modules to avoid pre-breathing with low-pressure space suits, but that would be insanely dangerous. It would be the outer-space equivalent of those stubborn elderly hospital patients who insist on smoking cigarettes while wearing oxygen tanks. A disaster just waiting to happen.

NASA tolerates low-pressure pure-oxygen pressurization in their soft space suits because they have no choice. There is not a lot of research, but NASA seems to think that if an astronaut in such a suit got punctured by a micro-meteor and it caught fire, the main hazard is a fire enlarging the diameter of the breach, not an astronaut-shaped ball of flame.

For what it is worth, the "Apollo Operations Handbook Extravehicular Mobility Unit", Revision 5, Table 2-I quotes the maximum leak rate of 180 cubic centimeters per minute at 25.5 kPa.

Suits can be Soft, Hard-shell, Semi-Rigid/Hybrid or Skintight.

Soft suits have flexible exteriors. This means they cannot be pressurized to the same level as the inside of the habitat module or the space suited person will be forced into a posture like a star-fish and be unable to bend any joints. Lower pressure means the suit uses pure oxygen unlike the habitat module. And pure oxygen means the astronaut has to do hours pre-breathing before wearing the suit or they will be stricken by The Bends.

Soft suits also take forever to put on, they fight your every movement (making EVA work very fatiguing), and if you tear the suit skin you will die horribly in about 90 seconds. When I say "fight your every movement" I mean "raise the energy expenditure to do a task by about 400%".

Currently most of NASA's space suits are soft suits.

Hard-shell suits have rigid exteriors. The advantage is they can be fully pressurized so no pre-breathing is required. They are also much more tear and puncture resistant than soft suits.

The drawback of hard-shell suits is that they make the "forever to put on" and "fight your every movement" problems much worse.

As far as I know there are no hard-shell suits in active use, they are all experimental.

Semi-rigid or Hybrid suits are a cross between soft and hard-shell. For instance, NASA's EMU has a hard-shell upper torso and soft fabric limbs. Current NASA semi-rigid suits are low pressure, but they are working on a high-pressure model.

Skintight suits are a radical concept that is so crazy it just might work. They make the astronaut's skin into the spacesuit, using high-tech spandex to supply pressure instead of using atmosphere. They can be quickly put on, fight your every movement only to the point of a +20% increase in energy, and if the suit is torn the astronaut only gets a bruise instead of certain death. The suits are also much inexpensive than a soft or hard-shell suit. The major draw-back is they require low pressure breathing mix (or the wearer cannot exhale), so astronauts have to pre-breath or face the Bends.

"Planetary suits" are used when there is an atmosphere, but it isn't breathable. They have a slightly different design from space suits.

(ed note: The crew of the Skylark try to use their newly invented space suits, which have never been actually tested in the field)

DuQuesne reported briefly to the two girls. All three put on space-suits and crowded into the tiny airlock. The lock was pumped down. There was a terrific jar as the two ships of space were brought together and held together. Outer valves opened; residual air screamed out into the interstellar void. Moisture condensed upon glass, rendering sight useless.

'Blast!' Seaton's voice came tinnily over the helmet radios. 'I can't see a foot. Can you, DuQuesne?'

'No, and these joints don't move more than a couple of inches.'

'These suits need a lot more work. We'll have to go by feel. Pass 'em along.'

DuQuesne grabbed the girl nearest him and shoved her toward the spot where Seaton would have to be.

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

Partial-Pressure Suits

To recap: Partial Pressure suits only pressurize certain parts of the body for a limited time. They are only used as a precaution, worn inside the habitat module during times when there is danger of it springing a leak, such as during lift-off or if an enemy spacecraft is shooting at you. Partial pressure suits are a trade-off: they only protect you for a short time but in exchange they do not encumber you anywhere near as much as a total pressure suit.

The NASA version is the Launch Entry Suit aka "pumpkin suit." It has ten minutes worth of life support internal to the suit, and can be hooked up to the vehicles life support system for longer duration.

The image above from First Men to the Moon is a partial pressure suit based on an old school Air Force high-altitude suit. If the pressure drops, the pressure regulating tubes along the suit's seams inflate to put the suit under tension. The wearer will then put on the oxygen mask attached to the small tank strapped to their leg.

The crew of a combat spacecraft in battle probably will not wear a soft, hard-shell, or semi-rigid suit during battle. This is for the same reasons that the crew of a military submarine do not wear SCUBA gear in battle even though they too are in a craft surrounded by countless miles of unbreathable stuff while being shot at. It gets in the way.

But they might wear a partial-(body) pressure suit or a skintight pressure suit.

Or a skintight partial-(body) hybrid pressure-suit. This might be so unencumbered that it could be used as everday wear. Then if the habitat module loses pressure all you'd need is an oxygen mask and earplugs to survive for a few hours. Wear it with overalls because such a suit will make you almost as naked as wearing nothing but body paint.


So, space folks, a question has been asked of me regarding that old trope of having everyone fully suited up and dumping the air when your space warships go to general quarters (GQ).

Now, I typically opine (after scribbling some numbers) that there's no point at all to the latter and very little to the former.

On the former point, in the unlikely circumstance that you are tapped gently enough by a munition to just hole your compartment, decompression will generally be slow enough that you have plenty of time to leave the compartment and/or fully don your suit. If, on the other hand, you're fully struck by a munition moving at typical space-intercept velocities, the energies involved are such that it won't matter a damn whether the Charred and Splattered Red Paste Formerly Known As You was suited up or not. And the tiny gap in between these two scenarios is nowhere near wide enough to make it worth giving up the advantages of a shirt-sleeve environment.

On the latter point, the reasons I usually see given for dumping the air include avoiding explosive decompression (about which I think there's no reason to care for the same reasons as above), that it prevents fires, and shockwaves. far as fires go, the first thing that occurs to me is that most of the particularly dangerous things that might burn on a spacecraft are things that have no business being inside the pressure hull in the first place. The second one is that if you're talking about fire caused by, well, incoming fire, then much of the time you're talking about things in the compartment-wrecking open-to-space scenario anyway, in which case the decompression will happen anyway help from you. And the third one is that if you're only dumping the air at GQ, then you need a perfectly functional suite of fire-suppression systems for the rest of the time anyway, so let them do their job.

As for shockwaves — well, again, I would expect that, given the energies involved, whatever damping or transmitting effects the air might have are going to end up lost in the rounding. (High-energy penetrating strikes might include flashover problems from KE ending up in the air, but given all the other things that will kill you in high-energy penetrating strikes, those aren't going to make you any more dead.)

Soft Suits

To recap, Soft Suits:

  • Must have lower pressure than the habitat module or the wearer turns into a starfish and cannot bend their limbs. This means the wearer needs an hour of pre-breathing or they will suffer the Bends.
  • In case of emergency, when there is no time for pre-breathing, NASA helpfully directs the astronauts to gulp aspirin, so they can work in spite of the agonizing pain
  • The breathing mix will be close to pure oxygen, with a higher fire risk.
  • Suit encumbrance increases the energy cost to do various tasks by +400%, with a corresponding increase in wearer fatigue.
  • If the soft skin of the suit is torn or punctured, the wearer will die in about 90 seconds.
  • They take forever to put on

For a list of the parameters for a NASA spec space suit, go here.

The only thing that allows an astronaut to bend their limbs at all is the magic of constant volume joints. These are why most pictures of space suits look like the Michelin Man (i.e., like a stack of donuts).

Dan chuckled, then sobered. "Like that, eh? Okay, you won't get any favors. But you'll still stay here today. Look, Jim, when I first came up, there was a guy named Joe with me. The first day he spotted some cargo drifting off and leaped for it. Put out a hand to grab it—and, naturally, when his arm moved one way his body moved the other. His suit hit a sharp edge of metal. A man dies fast out here when the air runs out of his suit, and it's not a pretty thing to see. You stay inside."

Jim practiced dutifully, gaining some proficiency as he did. He had to learn by experience that the twitch of a foot at the wrong moment could throw him off balance.

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


In The Millennial Project Savage suggests that the helmet will have an outer layer of five millimeters of high density lead crystal. Inside will be two layers of dense borosilicate glass sandwiched between two layers of Lexan. The middle layer of Lexan will add strength and prevent shattering, the inner will act as a reserve helmet. The outer surface will be gold anodized to block glare, ultraviolet, and infra-red. There may be a nested set of telescoping curved armor plates that can be deployed for further protection.

NASA helmets are not quite so grandiose.

NASA helmets are spherical domes, which hits the sweet spot between low mass, pressure compensation, and field of view. All current NASA suits have the astronaut's head is held facing forwards, you have to turn your entire body in order to look sideways. Astronauts call this "alligator head".

The helmet has to be comfortable to wear, and help in controlling the humidity inside the helmet (so it doesn't fog up). Another important part is the radio communication unit, since the lack of air in space prevents the sound of your voice from reaching anybody. The old tagline to the first ALIEN movie was "In Space No One Can Hear You Scream". Well, no one can hear Floyd asking somebody to pass him a socket wrench either. NASA suits use "Snoopy caps" to hold the communciation earphones and microphones (in NASA-speak this is called the Communications Carrier Assembly (CCA)).

Other items might include windshield wipers (inside for condensation, outside for dust), a build-in set of binoculars, headlights for shadowed areas, a mirrored sun-visor to prevent sunlight from burning out your retinas, a water drink dispenser, and maybe a gadget that can supply various medications (pain relievers, anti-nausea, stimulants).

As previously mentioned, NASA astronaut always put on a transdermal dimenhydrinate anti-nausea patch when suiting up in a space suit, in case of drop sickness. The chances of that are slight, but suffocating inside a helmet full of vomit is a nasty way to die.

Some SF novels have a space helmets equipped with a tiny airlock near the mouth, called a "chow-lock." It is used to allow the astronaut to eat and drink without venting the helmet's air to the vacuum of space. I am uncertain how practical this concept is, or how idiot proof it can be made. It would be a bad thing if trying to get a bite of a candy bar accidentally killed you.


Hell, we’ve been sleeping nine hours out of the eighteen! Heim glanced at the others. Their suits had become as familiar to him as the seldom seen faces. Jocelyn was already unconscious. Uthg-a-K’thaq seemed to flow bonelessly across the place where he lay. Vadász and Bragdon sat tailor style, but their backs were bent. And every nerve in Heim carried waves of weariness. “All right,” he said.

He hadn’t much appetite, but forced himself to mix a little powder with water and squeeze the mess through his chowlock. When that was done, he stretched himself as well as his backpack allowed.

From THE STAR FOX by Poul Anderson (1965)

The path towards today’s helmet style grew out of a number of converging interests. Early Spaceflight Initiative helmets required more bulky hardware than modern compact systems, for example, which consumed and obscured much of the rear volume. Later industrial vacuum suits had the disadvantage of holding the wearer’s head in a forward-facing position, due to cushioning and ancillary equipment, restricting the wearer’s field of view. And then, of course, there were the various RFPs from the nascent Imperial Navy, and specifically the requests from the Flight Operations representatives, who were most insistent that while they were willing if reluctant to concede the impracticability of their traditional silk scarves as a vacuum suit accessory, relegating them to the role of dress uniform only, and even to acknowledge the uselessness of their equally traditional aviator goggles, they would not under any circumstances give up their leather-and-fur flight helmets.

(They had, after all, been presented upon graduation of every Pilot Officer since the first foundation of the Imperial Flying Corps. One might as well, in their view, expect a legionary to go into battle without his sword – or, as Military Service slang prefers to put it in either case – ‘stark ruddy naked’.)

And so we come to the modern bubble helmet, a spherical dome of smartglass sandwiched between high-impact sapphiroid. The outermost layer is gold-anodized, to block glare and harmful radiation (while in theory the smartglass could provide this filtration, the gold anodization is fail-safe, functioning even if suit power or data systems are malfunctioning), and designed to intrinsically shed fluids, dust, and electrical charge. The smartglass is capable of acting as an infinitely configurable variable-filter and information display surface, with HUD and augmented reality functions including night-vision and optical zoom. The view provided is unobstructed all around – even beyond the typical 100 degree head rotation – with the exception of two coin-sized spots above the eyeline and to each side where the headlight/camera modules are mounted. A third light/camera module, rear-mounted, provides a projectable rear view. These modules also include miniature trigraphic projectors, enabling the projection of status, communicative, and affective symbols over the wearer’s head.

The helmet is pressurized with the normal canned life support blend of oxygen and inert-mix, to standard ship’s pressure. (Since modern skinsuits incorporate MEMS-based respiration assistance, it is no longer necessary to use high-oxygen breathing mixes.) This is controlled by the systems torc at the base of the helmet, which locks onto the attachment ring/neck dam at the neck of the vacuum suit (itself connected to many fibers running throughout the suit fabric to prevent accidental detachment). Light nanofluid cushioning that surrounds the neck once the helmet is donned provides additional neck protection and stability.

The primary purpose of the systems torc, apart from this connection, is the containment of the suit’s data systems and mesh communications suite. (Its location permits it direct interface with its wearer’s back-neck laser-port, although an auxiliary manual keypad can be connected and mounted on an arm of the suit if desired.) It also contains a miniature high-pressure oxygen tank and rebreather/dehumidifier system as a final hour’s emergency life-support supply. The torc also contains the connectors for the PLSS backpack, including those which permit water, other beverages, food pastes, and pharmaceuticals to be dispensed to the wearer through a deployable pipette, or additionally in the case of pharmaceuticals, through an autoinjector into a neck vein.

Communications can be provided directly by the torc, either via the laser-port interface or via miniaturized microphones and loudspeakers built into the torc surface. Alternately, many wearers prefer the use of a simple headset worn under the helmet, which connects to the torc using local mesh radio.

– A History of Space Hardware, Orbital Education Initiative

From BUBBLE by Alistair Young (2016)


In NASA-speak, the backpack is called the Personal (or Primary or Portable) Life Support System (PLSS). At a minimum, it provides breathing mix, removes carbon dioxide, and regulates the suit's pressure.

Additionally it may remove humidity, odors, and contaminants from the breathing mix; cools the astronaut's body with oxygen or a liquid cooling garment; provides radio communication; displays and/or does telemetry of suit parameters; displays and/or does telementry of astronaut's health; and/or provides propulsion for EVA.

NASA's current design for PLSS is not foolproof, as astronaut Luca Parmitano discovered on July 16, 2013 when he almost died as his helmet filled up with water. The drum holes in the PLSS water separator got clogged, and the PLSS designers had a mistaken understanding of how water acts in microgravity (the designers thought it was impossible for the water to back up into the helmet).

As is usually the case, the reason astronaut Parmitano is alive today is because he did not panic. He had to move to the airlock and re-enter from memory, since he could not see with 1.5 liters of water covering his eyes.


The gloves are especially a problem. Back in the 1950's it was unclear if space suit gloves were even possible. You need to make the various protective layers thin enough to be able to fit between adjacent fingers. And with miniature constant volume cuffs at each finger joint. Some suit designers took a tip from deep sea diving suits and postulated mechanical pincers instead of gloves.

But as we know NASA did manage to design actual space suit gloves. However, they do not work very well. Almost every single NASA astronaut who has performed EVA has complaints about the difficulty of doing any fine work while wearing those gloves.

If you're headed for space, you might rethink that manicure: Astronauts with wider hands are more likely to have their fingernails fall off after working or training in space suit gloves, according to a new study.

In fact, fingernail trauma and other hand injuries—no matter your hand size—are collectively the number one nuisance for spacewalkers, said study co-author Dava Newman, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology.

"The glove in general is just absolutely one of the main engineering challenges," Newman said. "After all, you have almost as many degrees of freedom in your hand as in the rest of your whole body."

The trouble is that the gloves, like the entire space suit, need to simulate the pressure of Earth's atmosphere in the chilly, airless environment of space. The rigid, balloonlike nature of gas-pressurized gloves makes fine motor control a challenge during extravehicular activities (EVAs), aka spacewalks.

A previous study of astronaut injuries sustained during spacewalks had found that about 47 percent of 352 reported symptoms between 2002 and 2004 were hand related. More than half of these hand injuries were due to fingertips and nails making contact with the hard "thimbles" inside the glove fingertips.

In several cases, sustained pressure on the fingertips during EVAs caused intense pain and led to the astronauts' nails detaching from their nailbeds, a condition called fingernail delamination.

While this condition doesn't prevent astronauts from getting their work done, it can become a nuisance if the loose nails gets snagged inside the glove. Also, moisture inside the glove can lead to secondary bacterial or yeast infections in the exposed nailbeds, the study authors say.

If the nail falls off completely, it will eventually grow back, although it might be deformed.

For now, the only solutions are to apply protective dressings, keep nails trimmed short—or do some extreme preventative maintenance.

"I have heard of a couple people who've removed their fingernails in advance of an EVA," Newman said.


Sticky Boots

Many SF novels have magnetized space boots to allow the rocketeers to adhere to the hull, but magnets do not work very well on hulls composed of titanium, aluminum, or magnesium.

If one does have a ferromagnetic hull, it might be best to have magnets just in the boot heels but not the toes, to facilitate walking. The idea is that if a boot is attached to the hull, you can release it by pushing down with your toes and lifing your heel, using a natural walking motion to detach the magnetic heel. Then the boot moves forward, approaching the hull heel-first. This allows the magnet in the heel to attach.

This topic is gone into in more depth here.

Hard-Shell Suits

To recap, Hard-Shell Suits:

  • Can have the same pressure as the habitat module without the wearer turning into a starfish. The Bends are avoided.
  • The breathing mix will be the same or very close to that of the habitat module. No additional fire risk.
  • Suit encumbrance increases the energy cost to do various tasks by many times that of a soft suit, with a incredible increase in wearer fatigue.
  • The hard shell of the suit is very puncture resistant.
  • They take longer to put on than a soft suit.

Hard-shell suits try to fix the tearing problem at the expense of making the first two problems much worse. True, hard suits do solve the depressurization problem, but at such a cost.

The AX-5 hard suit was developed by Hubert Vykukal at NASA Ames Research center in the 1960's. It was based on deep sea diving suit technology created by Phil Nuytten of Nuytco Research. The rotating joints are angled with respect to a limb, with two halves each comprising a thick wedge section and a thin section. When a limb is bent, the joint rotate so that the thin sections come together, allowing the suit limb to bend in a correspoinding fashion. For more details, refer to The Rocket Company.

Semi-Rigid Suits

Semi-rigid Suits are sort of a cross between soft suits and hard-shell suits, typically with the chest or torso hard and the limbs soft.

The ideal design is to have a hard-shell torso allowing the suit to be high-pressure with zero-prebreathing required, coupled with separately pressurized soft limbs to avoid the encumbrance penalty suffered by full-(body) hard-shell pressure-suits.

Which is why NASA's EMU puzzles me, it is a semi-rigid suit that appears to have the disadvantages of both with the advantages of neither. No doubt there were other considerations that I am unaware of.

The company ILC Dover made the Mark III suit as a technology demonstrator in 1992. It actually was a zero prebreathe suit. It is pressurized to 57 kPa, which is close enough to the 101.3 kPa used in NASA habitat modules so that the bends is not an issue. The Mark III had the shell covering the entire torso, not just the chest like the EMU. There is a hard upper torso, a hard lower torso. There are bearings at shoulder, upper arm, hip, waist, and ankles. There are soft fabric joints at elbow, knee, and ankle. I do not know why there are both types of joints at the ankles.

One of its main drawbacks was that the suit could not separate at the waist like other NASA suits, you had to enter the suit from the backpack. As with all hard-shell and semi-rigid suits, it is heavier than a soft suit (59 kilograms).

NASA decided against further development of the Mark III, for whatever reasons.

Skintight Suits

An innovative alternative approach is the Mechanical Counter Pressure (MCP) Suit. Instead of trying to hold your body intact with air pressure, it holds it in with spandex. It sounds crazy but it just might be crazy enough to work.

To recap, Skintight Suits:

  • Must have lower pressure than the habitat module or the wearer cannot empty their lungs. This means the wearer needs an hour of pre-breathing or they will suffer the Bends. Higher pressure also increases the risk of catastrophic failure of the helmet, i.e., shooting off like a champagne cork and killing the wearer.
  • In case of emergency, when there is no time for pre-breathing, NASA helpfully directs the astronauts to gulp aspirin, so they can work in spite of the agonizing pain
  • The breathing mix will be close to pure oxygen, with a higher fire risk.
  • Suit encumbrance only increases the energy cost to do various tasks by +20%, compared to the +400% of soft suits and the astronomical increase of hard-shell suits.
  • Suit punctures result in bruises on the wearer's skin, instead of certain death.
  • Skintight suits are the most inexpensive of all the space suits, about $60,000 US in 2005 dollars.
  • It tends to grab male wearers uncomfortably in the crotch.

The original concept was created by Dr. Paul Webb in 1968. It is currently being developed by Dr. Darva Newman at MIT, under the name "Bio-Suit".

A skin-tight suit of high tech cloth exerts pressure over the rocketeer's body to provide pressure. A bubble helmet with oxygen supply allows one to breathe. Open pores in the suit actually allow the body to be cooled by perspiration. Tears will cause bruising to the skin, but are not as lethal as they are on a conventional suit. The suit can be quickly put on. They do not interfere as much with movement (+20% energy expenditure, compared with +400% for a NASA suit). And you can store them by folding them up and putting them inside the bubble helmet. The back pack is still bulky, though.

They do need some care in design, though. Any concave areas on the body that the suit does not hug will bulge out under internal body pressure until it fills the void (i.e., your armpits will become armhills). Putty or fluid filled bladders will be needed to prevent this. Care must be taken around those nether regions, the small of the back, and in certain locations of the female chest. Male wearers will need a rather sophisticated cup to cover the genitals. Even with the cup, the suit will tend to grab male wearers uncomfortably in the crotch.

And upon entering vacuum, one will have an instant attack of dire flatulence (aka High-altitude flatus expulsion or HAFE). Don't be polite, let it out right away or you may damage your intestines.

There may be a length of tubing added along the seams of the arms, legs, and torso. The suit will be relaxed for easy dressing, then the tubing will be pressurized to put tension on the fabric (This was used in the g-suits worn by early jet pilots). The tubing will automatically pressurize when the helmet is put on and pressured up.

This used to be a standard feature of partial-(body) pressure suits.

A more advanced design uses a strip of "shape metal alloy'. An applied voltage can toggle the metal strip between expanded and contracted.

Unlike other types of space suits, the helmets for skintight suits require something called a "neck dam." This goes around the neck, and tries to keep an air-tight seal. Otherwise the helmet shoots off like a champagne cork and all the air in the helmet will spray out.

I'm sure the neck dam will be the part of the suit that will cause designers the most headaches. I personally would be in favor of straps that go from the neck dam and loop around ones arm around the armpits, but I'm no expert.

In The Millennial Project Savage suggests that light tungsten armor plates be worn over the suit to give some anti-radiation protection (this would only be needed in high radiation areas, like the Van Allen belts).

A minimal version of the skintight suit can be developed for everyday wear inside a spacecraft, i.e., a Partial-(body) Skintight pressure-suit. In cases of emergency air pressure loss, all you'd need is an oxygen mask and earplugs to survive for hours (This was used in Jerry Pournelle's "Tinker". The suit was worn like long johns under a coverall. The coverall is due to the fact that the suit is about as modest as wearing a coat of paint.).

Amusingly, the skintight suit made an appearance in a 1995 novel and anime television series called Rocket Girls. Maybe not so surprisingly, Japanese media in general is noted for its high standards of scientific accuracy. In this case the anime series had JAXA (the Japanese Aerospace eXploration Agency) and real-life Japanese astronaut Naoko Yamazaki as technical advisors.

The fictitious Solomon Space Association is developing the low-mass suits since their anemic one-lung LS-5 rocket can barely lift itself off the launch pad, let alone any payload. In a further desperate attempt to save on mass, they are reduce to using 16 year old girls as astronauts (which is a predictable development for a Japanese anime). They only weigh 38 kilograms, instead of the sixty-odd kilograms of the adult male astronauts. They take up less room in the control cabin as well.

There has even been some serious discussion given to suits more like those worn by the girls on the covers of magazines. We cannot really wear nothing but bathing suits in space, even with a bubble on our heads to supply oxygen to our lungs. (Pressure from the oxygen on the inside of the lungs must be balanced by pressure outside to make breathing possible for any length of time.) For a very short period, the bathing-suit affair might be enough — or even a normal suit of clothes, with an oxygen helmet. This type, though, would be used only as an emergency affair, and might prove very painful in even a few minutes, if not fatal.

Still, it appears that a suit could be designed which would not require that most of it be inflated at all.

The development of the simpler spacesuit almost certainly is not something that will be accomplished on the first trips into space. That type of suit might never work, but it is worth thinking about.

Suppose we keep the plastic helmet and air supply. Let the section around the lungs be the usual inflated tube, puffed out just a trifle beyond the skin, so that air pressure surrounds the lungs. We are still dealing with only 3 pounds pressure of oxygen. Now taper the inflated tube down at the shoulders and waist and change to an elastic fabric that will be skintight over legs, arms and hips. This fabric can be woven or formed so that it will have almost exactly 3 pounds pressure against the skin for every square inch. Yet when we move, there is no change of air pressure at the joints, because the fabric fits against our skin snugly.

We can still cover the material with reflective paint and weave tiny heating wires through it to take care of the temperature. We can even make it just a bit porous, so that perspiration can work through and evaporate into space — as it will do at once. Our bodies naturally cool themselves and maintain an even temperature by controlling the amount of perspiration. The same thing might happen while wearing our spacesuit. If the body became too warm, we would perspire more, and so increase the cooling. Or if we grew too cold, the perspiration would lessen, reducing the cooling. By using some kind of porous underclothing, the perspiration from even the sections inside the pressurized and inflated part of the suit might reach the cooling sections. There would be some loss of oxygen this way, but it could be kept to a level that would not matter for short periods of time.

Perhaps even the part of the suit over the lungs could be devised of similar elastic material, so that there would be oxygen only in the helmet. In that case, instead of huge, bulky suits, we might have something that looked like the tights male ballet dancers wear.

From ROCKETS THROUGH SPACE by Lester Del Rey (1957)

The pressure suit went on like a diver's wet suit, and looked like one only not so thick. It fit very closely; he had to use talcum power to get into it. Gloves dogged onto the ends of the sleeves, and a seal set firmly around his neck. He slipped into the boots, hung the small equipment bag over his shoulder, and reported back to the technicians.

They pulled and pinched, looking for loose spots. They didn't find any in Kevin's, but the next to come up was the girl he'd seen before, and after a moment they handed her a lump of what looked like clay. "Shove that under your breasts," the technician said. "Yeah, right there. Don't leave any gaps."

"But — " She was obviously embarrassed.

"Lady, you're going into vacuum," the man explained. "Your innards will be pressurized to about seven pounds by the air in your helmet. Outside is nothing. Your skin won't hold that. The suit will, but you've got to be flat against the suit, otherwise you'll swell up to fit any empty spaces. It won't do a lot of good for your figure."

"Oh. Thank you," she said. She turned away and used the clay as she'd been told.

From EXILES TO GLORY by Jerry Pournelle (1977).

      "Hullo, laddie. All right in there?"
     Aeneas grabbed for the microphone and pressed the talk switch. "That was one hell of a ride." He fought for control of his voice. "I think I'm all right now."
     "Except that you feel like letting the world's record fart, right?" the voice said. "Go ahead. You'll feel better." (one of the drawbacks of a skintight space suit)
     He tried it. It helped.
     "Hang on there, mate. Be alongside in a minute," the voice said. It took less than that. There were clunks and thuds, and the capsule jarred with some impact. "Righto. You're new in this game, they tell me."
     "Yes, very," Aeneas replied.
     "Right. So we'll start by testing your suit. I've got a bottle attached to the outlet, crack the atmosphere evac valve a half turn, there's a good chap."
     A short moment of panic. The capsule held half an atmosphere. When the capsule was evacuated, only his helmet above the neckseal would contain pressure. The tight garment he wore was supposed to reinforce his own skin so that it would be able to hold the pressure differences, and it had worked in the ground training chamber; but there had been physicians waiting there. Aeneas did as he was told. As the air hissed out, the pressure in his guts returned, but worse.
     "Fart again, lad. How's the breathing?"
     "All right." He carried out the instruction. Again it helped. It was hard work to breathe out, but there didn't seem to be any problems.
     "Good. Open the valve the rest of the way and let's get you out of there." Pumps whirred, and he felt more sensations of internal pressure. The wetsuit was very tight around every part of his body. His heart pounded loudly, and he felt dizzy.
     "Now unstrap and open the hatch."

From HIGH JUSTICE by Jerry Pournelle (1974)

      A blaring horn hammered at his ears and the red emergency light blinked madly. An amplified recording thundered out, replacing the sound of the horn.


     At the moment the horn had been sounded, the emergency locker across the room had crashed open, activated by the same alarms that had sounded the warning.

     ‘Strip and dress,’ Don called out, repeating the drill as he had been taught. At the time it had just been one more thing to learn. He had never thought that he might some day use it.
     His one-piece shipsuit zipped open down the front, and he hopped along on one foot as he tore it off. He kicked off his lightweight sandals at the same time and jumped for the locker.
     The emergency spacesuit was still rocking on the end of the arm that had snapped it out of the storage locker. It was a one-piece suit, almost skintight, cut to an exact fit for him. The helmet dangled forward, away from him, while the entire suit was open down the back.
     ‘Head, right leg, left leg. Right arm, left arm, close,’ he mumbled to himself, repeating the drill.
     Grabbing the handles on the supporting rack, Don bent forward and put his head into the helmet. At the same instant he kicked his right leg into the suit. Automatic valves blew compressed air into the leg so it puffed out like a balloon. As soon as his leg was all the way in, his toes tripped a switch and the air stopped. The suit leg collapsed firmly about his own.
     Then the other leg and his arms, pushing in behind the expanding blast of air. He wriggled his fingers into the glove-like extensions of the arms and, as soon as they were all the way in, he reached out and punched the red knob with the white letters SEAL large upon it.
     The closing device sat on the suit at the base of his spine. It began to suddenly wriggle upwards, like a great insect, pulling the open edges of the suit together and sealing them. When it reached the helmet it dropped off and he was free. And his spacesuit was airtight.

     The entire process, from beginning to end, had taken less than twelve seconds.

     Don’s helmet looked like a round fishbowl with a hole in front of his nose and mouth. A metal cover for this stood open, ready to snap shut if the air pressure fell below five pounds to the square inch. His suit contained only a limited supply of oxygen and this had to be saved until really needed.

From SPACESHIP MEDIC by Harry Harrison (1970)

     On the big screen forward, two men —clad only in T-shirts and tights —are shown in the cramped air lock, struggling with their bright-colored leotard-like space suits, one red and one yellow.
     The material of the suits is lightweight, strong, flexible —but not very elastic. Of necessity, it must be tight fitting; it is a second skin. Two sour-looking crewmen are helping them with the sleeves and leggings.
     A fifth man is cramped against one wall, adjusting the helmets. He snaps a camera onto the left side of one —whatever the man is looking at will be relayed back to the bridge.
     When the men are at last secure in their suits, their helmets are lowered over their heads. The "valets" complete the connections to the mobility and life-support backpack units and check them out. That done, and the units activated, the men snap their face-plates shut, check the helmet seals for security, and lower the appropriate filters into place. They are now bright-colored golems, each with a great dark eye for a face.
     "Radio working?" asks one.
     The other touches his device-studded "chastity belt," a plastic frame around his waist and genitals. "Right."
     A wall panel flashes red —the other crewmen disappear through a hatch which slides impatiently shut after them. A hiss signals that the air is rapidly being drained from the chamber.
     The suits do not puff out; only an occasional bubble of air, trapped under their second skins, reveals that the pressure is quickly decreasing. And then even these too evaporate away. "Bridge, we're ready to go."

From YESTERDAY'S CHILDREN by David Gerrolds (1972)

Latex Space Suit: Yep, these (‘skinsuits’, as opposed to ‘hardsuits’) are in common use – by the civilian spacer, anyway, who has no use for, for example, vacuum-sealed hardshell combat armor – although without the ridiculous semi-Stripperiffic elements (Sheer, you say? Heh. That fabric may contain pores, but it also contains MEMS, computer mesh, wound gel vacuoles…) a lot of media justifies them with, and have been in said use right from the earliest days when the Spaceflight Initiative conducted its feasibility studies for Project Phoenix.

They actually look pretty similar to the prototype of such a spacesuit that Dr. Dava Newman is developing at MIT (illustrated at right), although having smartglass around to provide an infinitely configurable variable filter plus display surface lets them use somethng much more like the classic “clear bubble helmet” *there*. Add a small support/systems backpack, and you’ve got it.

Further information on this general type of spacesuit is, of course, available at Atomic Rocket. In the Imperials’ version, though, I should note further that:

  • Skillful use of smart-fabric (a long way from literal latex) and MEMS for mechanical assistance has got the prebreathing/breathing mix problems down to an irreducible minimum, in modern suits at least.
  • Integrated and self-motile nanofluids have replaced the awkward necessity of stuffing clay into relevant places, at least once you overcome any squeamishness at the way the stuff crawls over you to get there.

Janty Yates, the costume designer for "The Martian," originally looked for inspiration to NASA's prototype Z1 and Z2 spacesuits. She worked with NASA officials and engineers, whom she described as "bend-over-backwards helpful." But in the end, she and her team came up with something new for the main spacesuit in "The Martian".

"We basically had to start from scratch," Yates told "We would've loved to use NASA's designs, but in the end, we just couldn't do it.

"The Martian" director Ridley Scott needed great visuals of Watney's face (as well as the faces of his crewmates) from a variety of angles, and the Z1 and Z2 — which both feature helmets that meld into the shoulder region of the suit — could not meet that requirement, Yates said.

"Ridley needed to see his actors in profile; he needed to see them moving their heads; he needed close-ups on the eyes," said Yates

Aesthetics were also an issue; Scott didn't find the Z-2 spacesuit visually striking enough, Yates said.

Yates worked with concept artists to draw up a variety of basic designs for the suit worn by Watney and his crewmates on the Martian surface, then presented them to Scott for approval. The body-hugging, black-white-and-orange suit showcased in the film emerged by process of elimination. (Interestingly, the movie's suit superficially resembles the Biosuit, a real space garment being developed by researchers at the Massachusetts Institute of Technology.)

So, while NASA didn't come up with the surface suit featured in "The Martian," agency officials did approve the astronaut apparel.

"As we went along, we had to submit the designs for their approval," Yates said. "And they approved along the way, as did the [film's] art department."

"The Martian" features one other spacesuit in addition to the surface suit — a bulky white extravehicular activity (EVA) suit the astronauts wear in space. The film's EVA suit is modeled closely on the one NASA astronauts wear on spacewalks outside the International Space Station, Yates said.

"We kept that very much to NASA style, but we made it a lot more streamlined," she said.


     At least there was no smoke on the bridge. The ventilation system had cleared it. Death by smoke inhalation was almost as bad as death by vacuum. Sandoval fancied she could hear the vacuum on the other side of the hatch scratching to get in and kill them all.
     The Captain and Luch were going over the readings and checking the view on the rest of the deck. Finally the Captain looked up and rubbed his eyes. "Okay. We have a direct hit on this deck which, aside from letting the air out and messing our quarters up did not real harm. But we took that hit right before we went to FTL. Good job on that Sandy. Now we gotta get to the main damage control locker and the space suits there and get them back in here. Then we can see about patching that hole before it lets FTL space in ... that isn't good. And there's ten meters or so of indoor vacuum between us and that locker."
     Sandoval shuddered a bit. FTL entering STL space was never good. As a navigator she knew enough of the theory of FTL to know that. Non-biological entities, jump trauma, flash fever ... the list went on.
     The bridge damage control locker had compressor masks that could be hooked up to a small air tank or air line. No space suits though. In a perfect world they'd be suited up already and at their stations for a hazardous operation. The bridge was too cramped for a locker to hold their suits. It was only designed to keep them alive when things were killing them slowly.
     Using a breathing mask in a vacuum was a good way to kessler your lungs. Absently Sandoval began rooting through the locker, digging through the various odds and ends accumulated over the years. Power bars, lanyards, vacc tape spilled out. What was she looking for? A new hyperdrive to get them to port and a rescue ship?
     "Well I was told this sort of freighter was designed to explode on a direct hit killing us all cleanly," Luch said in mock anger. "I get out of this I'm suing the f*ck*ng shipyard."
     The Captain administered a dopeslap that forced Luchador to adjust the mask he never removed, for no one knew what reason. Sandoval never thought it was polite to ask. "Not the time Luch," the Captain reproved.
     "Sorry sir. A little gallows humor. On the bright side we could hide in the electronics hole and prolong life a few more hours. None of these doors are completely airtight but we could get by."
     "How long till we break out, Sandy?" the Captain asked.
     "At least six days," the small woman answered toying with the materials she'd pulled from the locker. They all knew the air was going to leak out before then. Even with the last refuge of the computer and sensor service crawspace they had maybe a day of air. Air tight doors everywhere was too expensive.
     It wasn't fair. She'd plotted that jump perfectly and in half the time. The ship had ducked missiles and beams like a courier on uppers. They had all performed so well in the face of an invasion and an enemy determined to kill them. It just wasn't good enough. But to die knowing there was a locker full of air tanks not ten meters away was galling.
     Luch grabbed a roll of tape. "We can seal the hatch with this. Buy us a few more hours. We could just say screw it, hit the overrides and open the hatch now. At least it'd be fast. Why do we have so many damn rolls of vacc tape anyway? Your previous quartermaster was a tool, Captain! And this damn ship ... you do everything on the cheap! We're going to die because you didn't spring for some extra spacesuits!"
     The Captain grabbed Luch by the arm and hauled him as far from Sandoval as he could. It wasn't very far. Urgent and harsh whispering followed. The Captain finally ordered the Steward/Mechanic to take a seat and eat a power bar. Sandoval toyed with an old wallet someone had constructed out of tape. Probably an attempt to stave off boredom on a watch during FTL, much like this but without a hole in the hull dooming them all.
     "Hey ... Captain!"
     Adhesive tape was invented in 1845 by Dr. Horace Day. Clear adhesive or tape was made by Richard Drew in 1922 and the Holy Grail: duct tape appeared in 1942. By TL 8 in the year 20-mumblety-rhubarb we have Vacc Tape!
     The salient feature of vacc tape is it works in vacuum. More primitive tapes use adhesives that boil off in vacuum or are destroyed in extreme temperatures. Vacc tape works in extreme temperatures and vacuum ... for a while. By TL 10 synthetic adhesives are able to keep a bond and even strengthen under temperatures extremes to rock hard consistency.
     The other feature of vacc tape is not obvious at first. It changes color in vacuum. A roll of red tape turns a bright blue. Exposure to oxygen turns it red again. Seal a hole with it and air leaking out will turn the tape red making it easy to judge the worth of your damage control. Air bubbles can be spotted and reinforced before they burst. Savvy spacers in an unstable situation or hull will lay strips around the door to the living section. A blue strip around the door indicates vacuum on the other side. Suit up. Some spacers put a strip around the wrist of their space suit as a final check that an airlock that says it is pressurizing is pressurizing.
     Needless to say the stuff also spawns its own craft industry. Spacers make all manner of things, wallets, bags even clothing, slippers and more ...
     "The breathing mask is not ... optimal," Sandoval said. The Captain's voice rattled in her earbud. "Explain?"
     "It's fogging like a sonuvabitch. Also the soft helmet part is inflating. I'm dizzy," she said walking down the corridor. To compound matters, her tape slippers were slippery: a small etymological irony and she was dragging an air line behind her. The journey of ten meters seemed very long.
     She was sure she was starting to feel the bends despite the Captain lowering the bridge's air pressure and switching to a pure oxygen mix.
     It was only logical they use her for a subject. She was the smallest, letting them layer the tape the thickest over her. She was female and needed less oxygen. She thought up the crazy plan.
     She knew her mask was filling with carbon dioxide, or was it monoxide? She always confused the two.  The mask's exhausts were puttied shut. To make maters worse the tape covering every inch of her below the neck constricted like a ... constricting animal thing. that monoxide dioxide was really messing with her.
     Applying the stuff was the most undignified ordeal of her young life. The Captain and Luch applied the tape in rings around her torso and extremities. Luchs made sure the strip ends overlapped a lot. Then they reinforced the rings in the first layer with a layer of vertical strips. That was bad enough. But Luchs wanted to make sure the tape wouldn't peel up from curvy places and had puttied them up but good. It didn't help that Luchs was asexual. She'd blushed down to her toes. It didn't help when Luchs said there were establishments that would pay a few hundred credits to people submitting to such treatment.
     The Captain's dopeslap was perfectly timed and thump on Luch's head was most satisfying. They actually all managed a laugh.
     To make matters worse her nose was itchy. Her nose was itchy. She was having all manner of trouble breathing and now had the figure of a twelve year old boy and her neck felt like it measured 70 centimeters because that pulchtritude had to go somewhere.
     Her goddam nose itched. Was an itchy nose a symptom of suffocation/asphyxiation?
     She was at the damage control locker! The door opened to her frenzied yanking and curses. Cursing helped all manner of things. She grabbed a spacesuit and turned to scramble back to the bridge. The door was open and looked inviting even though the vacuum was as hard on the other side of it. The Captain and Luchs were waiting in the electronics hole and were pretty screwed if she messed up. Lugging the suit and the air hose she slipped and slid back to the bridge. At least they still had gravity. That alone indicated the hull couldn't be that badly holed.
     Sandoval threw the suit into the pilot seat. Her vision was blurring and not from a fogged mask as she reached for the hot key they'd set up. She hit it before she reeled and crashed to the deck.
     She woke up in the deluxe stateroom's master's bed. Usually the captain took the cabin over when he couldn't fill it.
     Luchs was sitting on the bed shaking her foot. "How are ya?" he asked. Sandoval stretched and saw tape still covered her arms. She moved her feet and realized it still covered most of her. She saw a very careful slit was made down her sternum letting her breathe. "I have the best vat steak in the galley cooking for you with your favorite sides. The Captain is still working on damage control but we're holding air. The beam went through the hull at stateroom three. There's a big hole on the outer hull and a nasty on on the hatch. He slapped patches on them and is welding the cabin's hatch shut."
     "Sounds good. Can I get up?" Sandoval said. She really was enjoying the bed though. Much better than a bunk.
     "Sure Sandy ... but here's the bad news: that tape has to come off you before it cuts off circulation."
     "Mmm ..."
     "On three ..." Luchs said.
     He yanked the first strip off on 'one'.
     The Captain heard her scream through one deck and his helmet.

From VACC TAPE by Rob Garitta (2017)

Going Outside

Suiting Up

I had an awful time getting into it - dressing in an upper berth is a cinch by comparison. The photographer said, "Just a minute, kid. I've seen 'em do it at Wright Field. Mind some advice?"

"Uh? No. I mean, yes, tell me."

"You slide in like an Eskimo climbing into a kayak. Then wiggle your right arm in-"

It was fairly easy that way, opening front gaskets wide and sitting down in it, though I almost dislocated a shoulder. There were straps to adjust for size but we didn't bother; he stuffed me into it, zippered the gaskets, helped me to my feet and shut the helmet.

. . .

But I didn't get tired of it; a space suit is a marvelous piece of machinery - a little space station with everything miniaturized. Mine was a chrome-plated helmet and shoulder yoke which merged into a body of silicone, asbestos, and glass-fibre cloth. This hide was stiff except at the joints. They were the same rugged material but were "constant volume" - when you bent a knee a bellows arrangement increased the volume over the knee cap as much as the space back of the knee was squeezed. Without this a man wouldn't be able to move; the pressure inside, which can add up to several tons, would hold him rigid as a statue. These volume compensators were covered with dural armor; even the finger joints had little dural plates over the knuckles.

It had a heavy glass-fibre belt with clips for tools, and there were the straps to adjust for height and weight. There was a back pack, now empty, for air bottles, and zippered pockets inside and out, for batteries and such.

The helmet swung back, taking a bib out of the yoke with it, and the front opened with two gasketed zippers; this left a door you could wiggle into. With helmet clamped and zippers closed it was impossible to open the suit with pressure inside.

Switches were mounted on the shoulder yoke and on the helmet; the helmet was monstrous. It contained a drinking tank, pill dispensers six on each side, a chin plate on the right to switch radio from "receive" to "send," another on the left to increase or decrease flow of air, an automatic polarizer for the face lens, microphone and earphones, space for radio circuits in a bulge back of the head, and an instrument board arched over the head. The instrument dials read backwards because they were reflected in an inside mirror in front of the wearer's forehead at an effective fourteen inches from the eyes.

Above the lens or window there were twin headlights. On top were two antennas, a spike for broadcast and a horn that squirted microwaves like a gun-you aimed it by facing the receiving station. The horn antenna was armored except for its open end.

This sounds as crowded as a lady's purse but everything was beautifully compact; your head didn't touch anything when you looked out the lens. But you could tip your head back and see reflected instruments, or tilt it down and turn it to work chin controls, or simply turn your neck for water nipple or pills. In all remaining space sponge-rubber padding kept you from banging your head no matter what. My suit was like a fine car, its helmet like a Swiss watch. But its air bottles were missing; so was radio gear except for built-in antennas; radar beacon and emergency radar target were gone, pockets inside and out were empty, and there were no tools on the belt. The manual told what it ought to have - it was like a stripped car.

Carry steel bottles on your back; they hold "air" (oxygen and helium) at a hundred and fifty atmospheres, over 2000 pounds per square inch; you draw from them through a reduction valve down to 150 p.s.i. and through still another reduction valve, a "demand" type which keeps pressure in your helmet at three to five pounds per square inch-two pounds of it oxygen. Put a silicone-rubber collar around your neck and put tiny holes in it, so that the pressure in the body of your suit is less, the air movement still faster; then evaporation and cooling will be increased while the effort of bending is decreased. Add exhaust valves, one at each wrist and ankle-these have to pass water as well as gas because you may be ankle deep in sweat.

The bottles are big and clumsy, weighing around sixty pounds apiece, and each holds only about five mass pounds of air even at that enormous pressure; instead of a month's supply you will have only a few hours - my suit was rated at eight hours for the bottles it used to have.

. . .

To make darn sure that you're getting enough (your nose can't tell) you clip a little photoelectric cell to your ear and let it see the color of your blood; the redness of the blood measures the oxygen it carries. Hook this to a galvanometer. If its needle gets into the danger zone, start saying your prayers. (ed. note: in Heinlein's other novels, instead of a galvanometer they use an "anoxia warning light")

. . .

Air sighed softly into the helmet, its flow through the demand valve regulated by the rise and fall of my chest - I could reset it to speed up or slow down by the chin control.

. . .

I didn't bother with a radar target or beacon; the first is childishly simple, the second is fiendishly expensive. But I did want radio for the space-operations band of the spectrum - the antennas suited only those wavelengths.

. . .

The only thing that complicated the rest of the electrical gear was that everything had to be either "fail-safe" or "no-fail"; a man in a space suit can't pull into the next garage if something goes wrong - the stuff has to keep on working or he becomes a vital statistic. That was why the helmet had twin headlights; the second cut in if the first failed - even the peanut lights for the dials over my head were twins. I didn't take short cuts; every duplicate circuit I kept duplicate and tested to make sure that automatic changeover always worked.

Mr. Charton insisted on filling the manual's list on those items a drugstore stocks - maltose and dextrose and amino tablets, vitamins, dexedrine, dramamine, aspirin, antibiotics, antihistamines, codeine, almost any pill a man can take to help him past a hump that might kill him.

. . .

I made it a dress rehearsal - water in the drinking tank, pill dispensers loaded, first-aid kit inside, vacuum-proof duplicate (I hoped it was vacuum-proof) in an outside pocket. All tools on belt, all lanyards tied so that tools wouldn't float away in free fall.

. . .

I ran into a snag. The spare bottles I had filched from those ghouls had screw-thread fittings like mine - but Peewee's bottles had bayonet-and-snap joints. Okay, I guess, for tourists, chaperoned and nursed and who might get panicky while bottles were changed unless it was done fast - but not so good for serious work.

. . .

"Mind your pressure. Kip. You're swelling up too fast." I kicked the chin valve while watching the gauge - and kicking myself for letting a little girl catch me in a greenhorn trick. But she had used a space suit before, while I had merely pretended to.

From HAVE SPACE SUIT - WILL TRAVEL by Robert A. Heinlein, 1958.

(ed note: this is a bit dated since it was written in 1939, but still surprisingly good)

"This is a standard service type, general issue, Mark IV, Modification 2." He grasped the suit by the shoulders and shook it out so that it hung like a suit of long winter underwear with the helmet lolling helplessly between the shoulders of the garment. "It's self-sustaining for eight hours, having an oxygen supply for that period. It also has a nitrogen trim tank and a carbon dioxide water-vapor cartridge filter."

He droned on, repeating practically verbatim the description and instructions given in training regulations. McCoy knew these suits like his tongue knew the roof of his mouth; the knowledge had meant his life on more than one occasion.

"The suit is woven from glass fibre laminated with nonvolatile asbesto-cellutite. The resulting fabric is flexible, very durable; and will turn all rays normal to solar space outside the orbit of Mercury. It is worn over your regular clothing, but notice the wire-braced accordion pleats at the major joints. They are so designed as to keep the internal volume of the suit nearly constant when the arms or legs are bent. Otherwise the gas pressure inside would tend to keep the suit blown up in an erect position and movement while wearing the suit would be very fatiguing.

"The helmet is moulded from a transparent silicone, leaded and polarized against too great ray penetration. It may be equipped with external visors of any needed type. Orders are to wear not less than a number-two amber on this body. In addition, a lead plate covers the cranium and extends on down the back of the suit, completely covering the spinal column.

"The suit is equipped with two-way telephony. If your radio quits, as these have a habit of doing, you can talk by putting your helmets in contact. Any questions?"

"How do you eat and drink during the eight hours?"

"You don't stay in 'em any eight hours. You can carry sugar balls in a gadget in the helmet, but you boys will always eat at the base. As for water, there's a nipple in the helmet near your mouth which you can reach by turning your head to the left. It's hooked to a built-in canteen. But don't drink any more water when you're wearing a suit than you have to. These suits ain't got any plumbing."

Suits were passed out to each lad, and McCoy illustrated how to don one. A suit was spread supine on the deck, the front zipper that stretched from neck to crotch was spread wide and one sat down inside this opening, whereupon the lower part was drawn on like long stockings. Then a wiggle into each sleeve and the heavy flexible gauntlets were smoothed and patted into place. Finally an awkward backward stretch of the neck with shoulders hunched enabled the helmet to be placed over the head.

Libby followed the motions of McCoy and stood up in his suit. He examined the zipper which controlled the suit's only opening. It was backed by two soft gaskets which would be pressed together by the zipper and sealed by internal air pressure. Inside the helmet a composition mouthpiece for exhalation led to the filter.

From MISFIT by Robert Heinlein (1939)

(ed note: The people are using powered-armor spacesuits on planets where the temperature hovers around -270°C, 8 K)

"Now, you didn't get much in-suit training Earthside. We didn't want you to get used to using the thing in a friendly environment. The fighting suit is the deadliest personal weapon ever built, and with no weapon is it easier for the user to kill himself through carelessness. Turn around, Sergeant.

"Case in point." He tapped a large square protuberance between the shoulders. "Exhaust fins. As you know, the suit tries to keep you at a comfortable temperature no matter what the weather's like outside. The material of the suit is as near to a perfect insulator as we could get, consistent with mechanical demands. Therefore, these fins get hot especially hot, compared to darkside temperatures—as they bleed off the body's heat.

"All you have to do is lean up against a boulder of frozen gas; there's lots of it around. The gas will sublime off faster than it can escape from the fins; in escaping, it will push against the surrounding ice, and fracture it … and in about one-hundredth of a second, you have the equivalent of a hand grenade going off right below your neck. You'll never feel a thing.

"Variations on this theme have killed eleven people in the past two months. And they were just building a bunch of huts. (imagine how dangerous it will be when the enemy is shooting at you)

"Now everybody pay close attention. I'm going out to that blue slab of ice"—it was a big one, about twenty meters away—"and show you something that you'd better know if you want to stay alive."

He walked out in a dozen confident steps. "First I have to heat up a rock—filters down." I squeezed the stud under my armpit and the filter slid into place over my image converter. The captain pointed his finger at a black rock the size of a basketball, and gave it a short burst. The glare rolled a long shadow of the captain over us and beyond. The rock shattered into a pile of hazy splinters.

"It doesn't take long for these to cool down." He stopped and picked up a piece. "This one is probably twenty or twenty-five degrees (Kelvin, -248°C). Watch." He tossed the "warm" rock onto the ice slab. It skittered around in a crazy pattern and shot off the side. He tossed another one, and it did the same.

"As you know, you are not quite perfectly insulated. These rocks are about the temperature of the soles of your boots. If you try to stand on a slab of hydrogen, the same thing will happen to you. Except that the rock is already dead.

"The reason for this behavior is that the rock makes a slick interface with the ice—a little puddle of liquid hydrogen—and rides a few molecules above the liquid on a cushion of hydrogen vapor. This makes the rock or you a frictionless bearing as far as the ice is concerned, and you can't stand up without any friction under your boots.

"After you have lived in your suit for a month or so you should be able to survive falling down, but right now you just don't know enough. Watch."

The captain flexed and hopped up onto the slab. His feet shot out from under him and he twisted around in midair, landing on hands and knees. He slipped off and stood on the ground.

"The idea is to keep your exhaust fins from making contact with the frozen gas. Compared to the ice they are as hot as a blast furnace, and contact with any weight behind it will result in an explosion."

From THE FOREVER WAR by Joe Haldeman (1975)

Besides the usual cargo lock we had three Kwikloks. A Kwiklok is an Iron Maiden without spikes; it fits a man in a suit, leaving just a few pints of air to scavenge, and cycles automatically. A big time saver in changing shifts. I passed through the middle-sized one; Tiny, of course, used the big one. Without hesitation the new man pulled himself into the small one.

From Delilah and the Space-Rigger by Robert Heinlein (1949)

Safety Check

First Jamieson, then Wheeler, chanted the alphabetic mnemonic - "A is for air-lines, B is for batteries, C is for couplings, D is for D.F. loop ..." which sounds so childish the first time one hears it, but which so quickly becomes part of the routine of lunar life - and is something nobody ever jokes about.

From EARTHLIGHT by Sir Arthur C. Clarke. 1955.

And in Clarke's "The Haunted Spacesuit" aka "Who's There?" they chant "FORB" for Fuel, Oxygen, Radio, Batteries.

[Steve and Nadia] donned the heavily-insulated, heated suits, and Stevens snapped into their sockets the locking plugs of the drag line.

"Hear me?" he asked. "Sound-disks all x?"

"All x."

"On the radio-all x?"

"All x."

"I tested your tanks and heaters-they're all x. But you'll have to test..."

"I know the ritual by heart, Steve. It's been in every show in the country for the last year, but I didn't know you had to go through it every time you went out-of-doors! Valves, number one all x, two all x, three all x..."

"Quit it!" he snapped. "You aren't testing those valves! That check-up is no joke, guy. These suits are complicated affairs, and some parts are apt to get out of order. You see, a thing to give you fresh air at normal pressure and to keep you warm in absolute space can't be either simple or foolproof. They've worked on them for years, but they're pretty crude yet. They're tricky, and if one goes sour on you out in space it's just too bad-you're lucky to get back alive. A lot of men are out there somewhere yet because of sloppy check-ups."

" 'Scuse it, please-I'll be good," and the careful checking and testing of every vital part of the space-suits went on.

From SPACEHOUNDS OF IPC by E.E. "Doc" Smith, 1931.

The instructor ordered his group to "Suit upl" without preliminary, as it was assumed that they had studied the instruction spool.

The last of the ship's spin had been removed some days before. Matt curled himself into a ball, floating free, and spread open the front of his suit. It was an unhandy process; he found shortly that he was trying to get both legs down one leg of the suit. He backed out and tried again. This time the big fishbowl flopped forward into the opening.

Most of the section were already in their suits. The instructor swam over to Matt and looked at him sharply. "You've passed your free-fall basic?"

"Yes," Matt answered miserably.

"It's hard to believe. You handle yourself like a turtle on its back. Here." The instructor helped Matt to tuck in, much as if he were dressing a baby in a snow suit. Matt blushed.

The instructor ran through the check-off list -- tank pressure, suit pressure, rocket fuel charge, suit oxygen, blood oxygen (measured by a photoelectric gadget clipped to the earlobe) and finally each suit's walky-talky unit. Then he herded them into the airlock.

From SPACE CADET by Robert Heinlein (1948)

In spite of the fail-safe design of the P-suits— so loss of pressure in one part of the suit won't result in a total loss of suit pressure—we lost a rigger yesterday for a stupid reason.

Riggers working in P-suits are required to use the Buddy System—checking each other's gear before cycling to vacuum. But this crew was in a hurry to get on the job. So the buddy didn't check both of the helmet pressurizing lines where the fittings go into the helmet. From what Pratt determined by studying the P-suit later, neither line was inserted in the fitting past the detent. I've got to admit, it's difficult to tell when you've twisted the fitting past the detent, especially if you're already wearing P-suit gloves.

Out in vacuum, the guy snagged one of the lines and pulled it out of the helmet fitting. The check valve closed when the line left the fitting, just as it's supposed to do. But when he heard the line come out of the fitting, he turned, caught the other line on the same beam element, and pulled the second line far enough out of the fitting so it blew most of his back-pack oxygen supply out into space . . . and at the same time failed to come out of the fitting far enough to activate the check valve. He lost helmet pressure in a few seconds. By the time his buddy got to him, he died from what Fred termed "traumatic abaryia," or rapid and terminal loss of pressurization.

Another case was perhaps worse from our point of view because, although the man was alive when we got him, he was too far gone to save. Writers often talk about the "primordial cold of outer space." But we lost this man to hyperpyrexia—overheating.

P-suit backpacks are designed to get rid of the metabolic heat generated by the individual, plus the environmental heat load from outside. There's a limit to the backpack's capability. Everybody's trained to recognize the symptoms of potential overload—a rise in P-suit temperature, hyperventilation, headache, et cetera. When it starts to happen, you slow down, rest, relax— or you're dead very quickly. This poor guy never had a chance, and it was a genuine industrial accident thai finished him.

While a photovoltaic power module's brought up from LEO Base, where it's assembled, it converts sunlight to electricity, which is used to power the electric thrusters which propel it to GEO Base. The structure isn't metal; it's a carbon-reinforced composite plastic.

The riggers had docked the new module to the main array, and Lucky's crew moved in to make the electrical switchover. Supposedly, it's impossible to create an electric arc in a vacuum, but GEO Base is surrounded by a halo of escaped life-support-system gases, outgas-sing products from materials, and other things that make the vacuum less than perfect. This is a construction site, and I've never seen a clean construction site anywhere.

During one of the switchover sequences, part of an insulator failed and an arc jumped across the rest of the insulator to the structure. It vaporized the carbon-composite plastic, which in turn vapor-deposited on everything within fifty feet, including the P-suit of the man who was nearby. It blackened his P-suit within a fraction of a second. He was in full sunlight at the time. Within ten seconds his suit and backpack were too hot for the backpack system to handle. He practically fried in less than thirty seconds.

"Med Unit, Central!" the intercom rasped. "Accident in vacuum! Reported P-suit fire! Location Array Subassembly Module One Zero Seven. Repeat: One Zero Seven!"

One of the P-suited individuals was obviously unconscious. Tom surmised this from the limp, rag-doll posture and random small movements of the limbs of the P-suit. He looked at the faceplate and discovered that the inside surface was covered with a brownish-black deposit, The injured man was no longer being supported by his own backpack. It had been disconnected, and he had been buddy-coupled to another individual's pack.

"What happened?" Tom asked.

"Fire in the backpack," somebody announced on the radio.

"Jed hollered that's what happened before he choked," another voice cut in. "Pete got him hooked up buddy-style (cross-connect) in about twenty seconds."

It didn't take more than thirty seconds to repressurize the Pumpkin (ambulance). Then Tom opened the faceplate of the injured man's P-suit helmet. The man had had a beard that had been singed off. There were first- and second-degree burns on his face. The most severe burns were in the vicinity of the oxygen inlet couplings from the backpack to the helmet. Tom had no way of knowing the nature or extent of possible burns in the lungs or airways.

It didn't take long to determine the source of the fire. Each backpack contains two high-pressure-oxygen storage bottles. A pressure switch valves a full bottle into the system when it senses the on-line bottle's pressure has dropped below a preset limit. The high-pressure oxygen then flows through a regulator that drops the pressure to about five psi absolute. The plastic O-ring that seals the upstream side of the regulator may have had a trace of contamination on it; the culprit seems to be aluminum shaved off the fitting when a maintenance tech over-tightened it. When the pressure sensor switched tanks, a shock wave of high-pressure oxygen hit the upstream side of the regulator fitting and was heated by shock compression. This action ignited whatever was on the O-ring. The aluminum of the regulator body then began to burn in the hot, oxygen-rich atmosphere, and, in turn, sent an oxygen-rich flame right down the breathing pressure lines to the interior of Hobart's helmet.

A fifty-cent O-ring and an uncalibrated torque wrench killed a man. It could also call a halt to a multibillion-dollar project.

Pratt says it's a simple fix. He's got his maintenance techs replacing O-rings and installing a diffuser upstream of the regulator as each backpack comes in from vacuum for refurbishment at the end of each shift.

From SPACE DOCTOR by Lee Correy (G. Harry Stine) 1981

First things first, and the first thing you need in space is a space suit. Apart from its necessity for working on space projects (building space stations, etc.) it is absolutely vital for examining the outside of your ship in case of damage from meteorites, etc. It may even be necessary to abandon ship, in extreme cases, and in this event your very existence depends upon its efficiency. You see me here in a self-contained, total-vacuum, mark-seven suit. Below you will find listed some of its most important features:

  1. Radio mast of ultra short-wave radio.
  2. Compressed air cylinder of closed-circuit air supply.
  3. Jet on universal mounting and chemical-fuel container.
  4. All joints reinforced. A punctured space suit means death!
  5. Reinforced plastic boots with electro-magnetic soles.
  6. Large universal-vision, anti-cosmic "Plastilight" helmet.
  7. Scaling ring to visor, metal with rubber "hose" lining, inflated from air supply.
  8. Miniature tele-view tray (referred to as the "T" tray).
  9. Control stick to jet (3). Twist grip rotates jet for manœuvring in space.
  10. Hydro-ammonal container and feed line to flame gun.
From Ron Turner's SPACE ACE POP UP BOOK (1953).

Buddy System

While wearing a space suit in vacuum, the iron-clad rule is The Buddy System. There are many mishaps that are trivial if you have a companion but fatal if you don't. Imagine that your suit springs a slow leak on your back just where you can't reach it with a repair patch. Oops.

In cases of emergency, two space suited people can "cross-connect" their oxygen supplies. This is generally done when one of them runs out of breathable gas, the other shares their oxygen until they get to shelter.

ed note: Kip (a college student) and Peewee (a little girl) are wearing spacesuits and are engaged in a forced march across the surface of Luna. Unfortunately the spare oxygen bottles the are carrying have connections incompatible with Peewee's suit. Kip uses surgical tape as an adapter to recharge Peewee's bottle. Peewee has tied the spare bottles to Kip's front. Oh, and Kip named his spacesuit "Oscar")

We were about halfway down the outer slope when Peewee slowed and stopped—sank to the ground and sat still.

I hurried to her. “Peewee!”

“Kip,” she said faintly, “could you go get somebody? Please? You know the way now. I’ll wait here. Please, Kip?”

“Peewee!” I said sharply. “Get up! You’ve got to keep moving.”

“I c-c- can’t!” She began to cry. “I’m so thirsty … and my legs—” She passed out.

“Peewee!” I shook her shoulder. “You can’t quit now! Mother Thing! —you tell her!”

Her eyelids fluttered. “Keep telling her, Mother Thing!” I flopped Peewee over and got to work. Hypoxia hits as fast as a jab on the button. I didn’t need to see her blood-color index to know it read DANGER; the gauges on her bottles told me. The oxygen bottles showed empty, the oxy-helium tank was practically so. I closed her exhaust valves, overrode her chin valve with the outside valve and let what was left in the oxy-helium bottle flow into her suit. When it started to swell I cut back the flow and barely cracked one exhaust valve. Not until then did I close stop valves and remove the empty bottle.

I found myself balked by a ridiculous thing.

Peewee had tied me too well; I couldn’t reach the knot! I could feel it with my left hand but couldn’t get my right hand around; the bottle on my front was in the way—and I couldn’t work the knot loose with one hand.

I made myself stop panicking. My knife—of course, my knife! It was an old scout knife with a loop to hang it from a belt, which was where it was. But the map hooks on Oscar’s belt were large for it and I had had to force it on. I twisted it until the loop broke.

Then I couldn’t get the little blade open. Space-suit gauntlets don’t have thumb nails.

I said to myself: Kip, quit running in circles. This is easy. All you have to do is open a knife—and you’ve got to … because Peewee is suffocating. I looked around for a sliver of rock, anything that could pinch-hit for a thumb nail. Then I checked my belt.

The prospector’s hammer did it, the chisel end of the head was sharp enough to open the blade. I cut the clothesline away.

I was still blocked. I wanted very badly to get at a bottle on my back. When I had thrown away that empty and put the last fresh one on my back, I had started feeding from it and saved the almost half-charge in the other one. I meant to save it for a rainy day and split it with Peewee. Now was the time—she was out of air, I was practically so in one bottle but still had that half-charge in the other—plus an eighth of a charge or less in the bottle that contained straight oxygen (the best I could hope for in equalizing pressures), I had planned to surprise her with a one-quarter charge of oxy-helium, which would last longer and give more cooling. A real knight-errant plan, I thought. I didn’t waste two seconds discarding it.

I couldn’t get that bottle off my back!

Maybe if I hadn’t modified the backpack for nonregulation bottles I could have done it. The manual says: “Reach over your shoulder with the opposite arm, close stop valves at bottle and helmet, disconnect the shackle—” My pack didn’t have shackles; I had substituted straps. But I still don’t think you can reach over your shoulder in a pressurized suit and do anything effective. I think that was written by a man at a desk. Maybe he had seen it done under favorable conditions. Maybe he had done it, but was one of those freaks who can dislocate both shoulders. But I’ll bet a full charge of oxygen that the riggers around Space Station Two did it for each other as Peewee and I had, or went inside and deflated.

If I ever get a chance, I’ll change that. Everything you have to do in a space suit should be arranged to do in front — valves, shackles, everything, even if it is to affect something in back. We aren’t like Wormface, with eyes all around and arms that bend in a dozen places; we’re built to work in front of us — that goes triple in a space suit.

You need a chin window to let you see what you’re doing, too! A thing can look fine on paper and be utterly crumby in the field.

From HAVE SPACE SUIT - WILL TRAVEL by Robert Heinlein, 1958



When you gotta go, you gotta go. A sudden urgent need to urinate or defecate when you are in a space suit during an EVA is a major problem.

NASA became aware of the need for space diapers on May 5, 1961. Freedom 7 was about to launch with astronaut Alan Shepard. NASA figured there was no need for a potty break, er, ah, "bladder evac" since the flight was only going to take 15 minutes. Alas there were several delays so poor Alan was on the pad for eight hours. He had to ask ground control for permission to pee in his suit, which was granted. Shorted out some of his medical sensors, though.

For the Gemini and Apollo programs they had a system for urination only. It was functionally equivalent to a condom (a "cuff") attached to a tube. The tube drained into a containment bag through a one-way valve. The cuff fit had to be snug or there would be dangerous leakage. The cuffs came in three sizes.

The space suit designers demonstrated a stunning ignorance of macho astronauts when they labeled the sizes "small", "medium", and "large".

Predictably, when asked which size they needed, all the testosterone-poisoned Right Stuff astronauts answered "Large, of course."

After a few nasty incidents of space suits filling up with urine due to poorly fitting sheaths, the technicians re-named the sizes "large", "gigantic", and "humongous."

Unfortunately the best technology NASA currently has to offer is the "Maximum Absorbency Garment" (MAG). Which is basically a high-tech diaper. The MAG is full of sodium polyacrylate, which can absorb 300 times its weight in water. The MAG can hold about two liters of urine, blood, and/or feces. It was a challenge since conventional incontinence pants require gravity in order to operate.

Astronauts in free fall tend to have lots of urine to void when they finally feel the urge to go. Under normal gravity urine collects at the bottom of the bladder, triggering the urge when the bladder is one-third full. But in zero gee, urine in the bladder is floating around. The urge only comes when the bladder is almost totally full, causing pressure on the sides. Which is a problem since that much urine can press the urethra shut, making it hard to urinate. Astronauts are advised to schedule regualar pee breaks even if they do not feel the need.

Or the doc will have to open the first aid kit and break out the Foley catheter. That is not a threat, it is a promise.

The first time the condom and bag device was used in space was in John Glenn's 1962 orbital flight. He voided a full 27 ounces of urine in one go, which is about seven ounces more than the capacity of the average human bladder.


Schweickart: Yeah, it's not that much. But it's a fairly critical time, you know. When you're in there you don't have much choice, so you've got to design for it. Okay. So in the suit, for urine you use like a motorman's bag, which is basically composed of a bladder that holds about — boy, my numbers are really slipping Peter — but something between a liter and two liters, if I remember. A rubber bladder type of thing that sort of fits around your hips, and a rollon cuff which is essentially a condom with the end cut out that's rolled over a flapper-type valve, you know, just a rubber flapper valve. It forms a one-way check valve.

Warshall: Oh, I see, so you don't have to do anything.

Schweickart: No, you don't do anything. You just roll it on as part of the suit-donning procedure, and then urinate into it through the one-way valve. There are lots of little cute problems and uncertainties Unless you're an extremely unusual person, since the time you were about a year and a half old or so, you probably have not taken a leak laying flat on your back. And if you think that's easy, let me tell you, you've got some built-in psychological or survival programs, or something which you've got to overcome. So that's a tricky little thing. And then there's always the possibility that in maneuvering around in a suit you can end up pulling off the condom, and there's always — we have three sizes you know, small, medium and large — in diameter, and there's always this little ego thing about which one you do pick. of course the smart guy picks the right size, because it's very important. But what happens is, if you get too small a size it effectively pinches off the flow and you just turn yellow because you can't go; and if, on the other hand you've got an ego problem and you decide on a large when you should have a medium, what happens is you take your first leak and you end up with half of the urine outside the bag on you. And that's the last time you make that mistake. So it's a cute little trick there.

In terms of defecation inside the suit, there ain't no graceful way to do it. So what we do is, we wear what's affectionately called a fecal containment system. The good old FCS is essentially like a pair of bermuda shorts with a hole for your penis to stick out of to roll on this other thing, but fairly well sealed around there.

It's a tight fitting elastic type garment, and it fits especially tight around the thighs and around the waist. And it's just like a pair of diapers is what it is. made of material which obviously is non-permeable but still breathes and all it does is contain it. Now, to my knowledge, nobody's ever had to use that. But you wear it, because if you don't wear it, the consequences are rather drastic. Okay. So that sort of takes care of the in-the-suit situation.

Astronaut RUSSELL SCHWEICKART talking to Peter Warshall, collected in CoEvolution Quarterly Winter 1976-77

On Wednesday morning, NASA rewarded five members of the public — two doctors, a dentist, an engineer and a product designer — for their creative ideas for how to poop in a spacesuit.

Yes, it sounds a little bit funny. But unmet toilet needs could have life or death consequences for an astronaut in an emergency situation.

That's why thousands of people spent tens of thousands of hours on the "Space Poop Challenge," brainstorming, modeling, prototyping and number-crunching to come up with a crowd-sourced solution to the problem of human waste in a spacesuit.

Currently, astronauts on spacewalks rely on diapers, which is a feasible solution for only a few hours at a time. As we explained in November, NASA is imagining a situation where an astronaut is stuck in a spacesuit for days — like during an emergency on future Orion missions, which could take astronauts far from Earth.

The super-portable-bathroom solution has to work quickly, easily, in micro-gravity, without impeding movement, for both men and women, for solid and liquid waste. It can either store waste in the suit or expel it. And it has to be comfortable ... for up to six continuous days.

Since the project launched on the HeroX crowdsourcing site in October, nearly 20,000 people, from all over the world, submitted more than 5,000 ideas. They were competing for a total of $30,000 in prizes.

The winning solution came from Thatcher Cardon, an Air Force officer, family practice physician and flight surgeon. He says his design was inspired by minimally invasive surgical techniques — and a strong desire not to store the poop.

"I never thought that keeping the waste in the suit would be any good," he told NPR. "So I thought, 'How can we get in and out of the suit easily?' "

"I thought about what I know regarding less invasive surgeries like laparoscopy or arthroscopy or even endovascular techniques they use in cardiology — they can do some amazing things in very small openings.

"I mean, they can even replace heart valves now through catheters in an artery. So it should be able to handle a little bit of poop!"

He designed a small airlock at the crotch of the suit, with a variety of items — including inflatable bedpans and diapers — that could be passed through the small opening and then expanded. His design even allows an astronaut to change underwear while inside the spacesuit, through the same small opening.

Cardon used an old flight suit to try some physical prototyping, and his kids helped gather supplies. They were "totally excited," he says. "They lost their minds when I told them I won."

Second place went to a trio from Houston (the SPUDs team) — a physician, an engineering professor and a dentist (who also served as the team's illustrator). All three had studied chemical engineering in college.

Stacey Louie, the environmental engineer on the team, said the different areas of expertise on the team were central to their solution. But before they fine-tuned their design, they had to discard a lot of ideas.

For instance, doctor and team leader Jose Gonzales says that he immediately thought of some medicine-inspired strategies that would be effective — but not at all comfortable.

"You have to take into consideration, 'Is the astronaut going to be OK with this design?' " Katherine Kin, the dentist and artist, notes. "You have to have something that's psychologically comfortable."

So internal catheters were out. Instead, Gonzales says, they used an air-powered system to push waste away from the body to store it elsewhere in the suit. "More specifically, that air is created by passive and active normal body movements of the astronaut," Gonzales says.

A product designer from the U.K., Hugo Shelley, placed third. He usually works with electronics and tech products, but he says for this contest, he went in the other direction — and tried to build a solution with as few electronic parts as possible.

"I think we're all aware of the dangers of things going wrong in space," he says. A simple design seemed safer, he says.

"My mother's a textile designer so I think I started off really thinking about materials," he says. "Making something as comfortable as possible I thought was fairly important ... a lot of your mechanism really has to be in, effectively, the first few millimeters away from the skin."

His solution, the "SWIMSuit — Zero Gravity Underwear," disinfects and stores waste inside the suit, like the second-place design does.

Cardon won $15,000, while the trio from Houston took home $10,000 and Shelley netted $5,000.

The next step is for NASA to start prototyping the ideas, and get working versions of a waste-management system up to the International Space Station for testing.

Dustin Gohmert, the Orion crew survival system project manager at NASA, explains that NASA will combine existing ideas with elements of the winning designs to create a solution that will, indeed, go into space.

"Optimistically this will never be used, because it is a contingency scenario that something catastrophic has happened," he said. "But this will be on Orion and should something happen, and should it be called on to save the crew, this will be there and at their disposal."

Shelley, the product designer, notes that research on how to improve waste management inside a spacesuit could also be useful in "earth-bound applications" — for people with incontinence or in high-pressure, critical job situations.

And while it was "kind of odd" to think about poop in space for weeks at a time, he says the project was "quite exciting."

"Yes, it's an amusing thing to think about, but still it's a part of a spacesuit — and there's something incredibly thrilling about the space missions," he says.

And, he notes, "you can't fully appreciate being an interplanetary explorer if you've constantly got to use the bathroom and you can't."


On Earth, Andrew Lear's habits would have been no more than a character trait. In a hurry, he might choose mismatched socks. He might put off using the dishwasher for a day or two if he were involved in something interesting. He would prefer a house that looked "lived in." God help the maid who tried to clean up his study. He'd never be able to find anything afterward.

He was a brilliant but one-sided man. Backpacking or skin diving might have changed his habits — in such pursuits you learn not to forget any least trivial thing — but they would never have tempted him. An expedition to Mars was something he simply could not turn down. A pity, because neatness is worth your life in space.

You don't leave your fly open in a pressure suit.

A month after the landing, Childrey caught Lear doing just that.

The "fly" on a pressure suit is a soft rubber tube over your male member. It leads to a bladder, and there's a spring clamp on it. You open the clamp to use it. Then you close the clamp and open an outside spigot to evacuate the bladder into vacuum.

Similar designs for women involve a catheter, which is hideously uncomfortable. I presume the designers will keep trying. It seems wrong to bar half the human race from our ultimate destiny.

Lear was addicted to long walks. He was coming back from a walk, and he met Childrey coming out. Childrey noticed that the waste spigot on Lear's suit was open, the spring broken. Lear had been out for hours. If he'd had to go, he might have bled to death through flesh ruptured by vacuum.

From THE HOLE MAN by Larry Niven. 1974

Once I had one arm out it was pretty easy; I just crawled forward, putting my feet on the suit’s shoulders, and pulled on his free arm. He (the unconscious man) slid out of the suit like an oyster slipping out of its shell.

I popped the spare suit and after a lot of pulling and pushing, managed to get his legs in. Hooked up the biosensors and the front relief tube. He’d have to do the other one himself; it’s too complicated. For the nth time I was glad not to have been born female; they have to have two of those damned plumber’s friends, instead of just one and a simple hose.

I left his arms out of the sleeves. The suit would be useless for any kind of work, anyhow; waldos have to be tailored to the individual.

From THE FOREVER WAR by Joe Haldeman. 1975

Many people have written in to ask, “What is that silvery, liquescent lining inside the pants of spacesuits we occasionally see on your broadcasts?”

Well, viewers, that’s the sanitary nanopaste. You see, back in what we might call the pointy-stick era of spaceflight, the problem of the crew having to take a ‘fresher break while stuck in their vacuum suits for hours on end was handled by catheterization – it was necessary for astronauts to insert catheters into their urethra, rectum, cloaca, and/or any other excretory or partially-excretory orifices they might have in order to convey waste products to reservoirs for later disposal, and prevent them from contaminating the interior of the suit.

Apart from the occasional technical problems this had with leakage and providing pathways for infection, it was not a solution that was comfortable for anyone, or that anyone was comfortable with.

Fortunately, modern nanotechnology has provided the answer. Sanitary nanopaste selectively infiltrates one’s excretory orifices in a much more gentle manner than gross apparati (the sensation, I am told, being akin to mild tickling that rapidly becomes imperceptible), interfacing with the body’s own systems, and breaking down and compressing the body’s wastes in situ and conveying them directly and continuously, by molecular pass-the-parcel, to the vacuum suit’s recycling apparatus. In short: now, you simply never feel the need to excrete as long as you’re in your suit.

This is a much more elegant solution, obviously, and has satisfied virtually everyone – or at least everyone who isn’t overcome with squeamishness at the thought of microscopic robots roaming around in their bowels.

– Ixril Valenarius, Spaceflight Initiative Public Relations,
“This Week in Orbit”

Visual Identification

Once people are suited up, it does become hard to tell who is who. In Destination Moon, there were four spacemen, and each had a uniquely colored suit. Kind of like colored tooth-brushes. But this won't work if you have more than a few spacemen, er, spacepeople. The person's name stenciled in large letter across the front and back is a possibility.

In Piers Anthony's The Kirlian Quest, he notes that this problem has occurred before: knights in armor are similarly anonymous. The solution is coat of arms and heraldry. The knights wear their coats of arms on their shields, tabards, and horse barding, to identify themselves.

In other words, heraldry was a medieval form of an Identification Friend Or Foe system.

When a proposed heraldic "device" (coat of arms) is submitted to the college of heralds, it is compared with all existing devices. The new device must have at least one major and one minor point of visual difference from those already registered. Otherwise it would be too easy to confuse the two devices in the heat of battle. Mistaking a foe for a friend could be fatal. It is also a good idea if the device can be recognized at a distance.

As an amusing side note, a heraldic device has a "blazon". This is a verbal description of the heraldic device done in heraldic terminology. If you give a herald a blazon, they can reproduce the original device even if they had never seen it before. Just remember that the "blazon" is the verbal description and "to emblazon" means to draw, paint or otherwise make a graphic representation of the device (called an "emblazonment").

Heraldry developed as a way to be seen and identified across a battlefield, in the clash of war. This requires high-contrast designs whose elements are clearly recognizable.

The first step in recognizability is to use the stylized heraldic forms of things. The second is to make your charges as big and bold as possible in the space you have available.

Modern corporate logos usually follow the same rules that heraldic artists used, because they want their product logo to stand out, to be identifiable even at a distance, and to be recognizable. Consider the logos of Shell, Diamond Shamrock, BMW, Dodge, Purina, CBS — all of these follow the styles and rules of heraldry.

In Larry Niven's Protector, the Belters of the asteroid belt spend most of their lives inside their space suit. They have a tendency to paint their suits in extravagant colors. One of the characters had Salvador Dali's Madonna of Port Lligat on the front of their suit. In an interesting psychological quirk, Belters also tend to be nudists when in a pressurized environment.

And if you find any illustrations of the game Warhammer 40,000, you will quickly see that the Space Marines are big fans of heraldry. Even though you can generally idenifty the bad Marines by the tentacles, weeping open sores, and other Marks of Chaos. Otherwise, if the opponents look like skeletons they are Necrons; if they are tall, skinny, and distainful they are Eldar; if they are green with tusks they are Orks; and if they look like Giger's Alien xenomorph on bad LSD and are eating everything they are Tyranids. They are all enemies, so the basic rule is if it does not look like a Space Marine, shoot it with your bolter.

Most Belters decorated their suits. Why not? The interior of his suit was the only place many a Belter could call home, and the one possession he had to keep in perfect condition. But even in the Belt, Nick Sohl's suit was unique.

On an orange background was the painting of a girl. She was short; her head barely reached Nick's neck ring. Her skin was a softly glowing green. Only her lovely back showed across the front of the suit. Her hair was streaming bonfire flames, flickering orange with touches of yellow and white, darkening into red-black smoke as it swept across the girl's left shoulder. She was nude. Her arms were wrapped around the suit's torso, her hands touching the air pac on its back; her legs embraced the suit's thighs, so that her heels touched the backs of the flexible metal knee joints. It was a very beautiful painting, so beautiful that it almost wasn't vulgar. A pity the suit's sanitary outlet wasn't somewhere else.

From PROTECTOR by Larry Niven. 1973

(ed note: In the Cluster novels, the quotation mark symbols denote which species-language is being used. " is for humans, * is for Asts (looks like a mass of coils), / is for Slashes (looks like a living disk harrow, shooting laser beams), and :: is for Quadpointers (looks like a slug with four chisles on its nose). The protagonist Herald the Healer is a Slash.)

Whorl twined to another section of his convolute residence, and Herald followed. Here in the living rock bordering a corkscrew chamber was emblazoned in relief a creature-sized Shield of Arms.

It was beautiful. The outer shield was in the shape of an ellipse set at an angle, representing Galaxy Andromeda, bordered inside by a wreath of intertwining serpents to designate Sphere Ast. Within that were the Family Arms of Precipice, resembling an ornate overhanging cliff. Herald moved his loops across it, savoring its aspects. It had superior form, texture, and color, and was, in its fashion, a genuine work of art. The King of Arms of Ast was certainly a master!

*What do you find?* The query was urgent.

/I find an excellent and flawless emblazon./

*Did you not say 'blazon' before?*

The tedious questions of amateurs! But Herald repressed his annoyance, for courtesy was vital to his profession.

/I did, Whorl. The 'blazon' of a Shield of Arms is the precise linguistic specification of its elements. To 'emblazon' is to render this description into physical actuality./

*I comprehend. The one is the description, the other is the carving. I feared for a moment there was something wrong with it.*

/No, your Achievement is quite in order. Azurine, a cliff of thirty-seven rocks and forty-two rills, alternately thirteen, twelve, thirteen, seven, eleven, twenty-three, pearline, all within a bordure of the Serpents Rampant./

Herald winced inwardly as he communicated, for the old-style heraldic term "rampant" was restricted to certain quadrupedal beasts of prey, standing erect on the left foot raising the right foot in stride, balancing with the left forefoot outthrust, the right raised to strike. It was technically impossible for a legless serpent to be "rampant." But the broadening of the system to include diverse Cluster cultures had forced the fudging of some terms. However, as he had informed Whorl, the local Colleges of Arms defined legitimacy. So he had to accept it, nonsensical as it was in derivation. Regardless, this remained an excellent Shield of Arms, in concept and execution.

In a moment she was back on the subject. ::How did heraldry start?::

/Many species, in their pretechnical phases, wore special apparel to protect them from the attacks of physical weapons. This apparel was called 'armor,' and it was so encompassing that it became impossible to recognize the individual entity within it, the 'knight,' which figure is also represented in the Tarot deck. Therefore it became necessary to decorate his shield with some characteristic design, typical of his household and affiliation, so that friend could be distinguished from enemy. This eliminated the awkwardness of a knight lining up behind the formation of his enemy, supposing he was among friends. Or even attacking his friends, thinking they were enemies. The markings on the shield made everything instantly clear, even when the knights were not personally known to each other. This was the origin of heraldry. Today, all great families of all species in the Cluster have their registered Shields of Arms, even though they may never engage in combat./

::My family has a Shield! I never knew what it meant.::

/Come, I will explain what it means./ Following her directions, Herald located the Metamorphic Shield and placed it against the wall where both could view it. /Note that the shape of this Shield is elliptical, a kind of angled oval that signifies Galaxy Andromeda./

::But Andromeda is a spiral!::

/So it is. But from Milky Way it appears elliptical. (Since Andromeda lost the Wars of Energy, we suffer the additional humiliation of the ellipse. The Milky Way Shield is the fundamental shape, flat across the top, round or partly pointed across the bottom. Other Galaxies have other shapes.) Within this is the band of prints, the little four-point patterns, signifying Sphere Quadpoint. In Milky Way there are two bands, since that Galaxy is organized into segments and Spheres, but it is the same idea. Then the main design, the symbol of Family Metamorphic: a lump of edible rock superimposed on the geologic flowchart of its derivation. A distinctive Achievement—that is what the complete affair is called—recognizable anywhere in the Cluster./

::Can you recognize any Shield of Arms in the whole Cluster?:: she asked, a bit awed.

/Within certain broad categories, yes. It is my business. And this is true generally. Two completely alien sapients could meet on a barren planetoid, perhaps shipwrecked from different vessels, possessing no common language, form or status, and they could recognize each other by their Shields of Arms. That would provide their common experience. Each would know the other was sapient and civilized, and where he was from, and that he honored Cluster conventions of behavior./

From KIRLIAN QUEST by Piers Anthony ()

The tiger stripes on Jim's mask, the war paint on Frank's, and a rainbow motif on Phyllis's made the young people easy to identify. The adults could be told apart only by size, shape, and manner; there were two extras, Doctor MacRae and Father Cleary.

He poked his head inside, seemed about to leave, then came inside. He pointed to their outdoor suits, hanging on hooks by the clothes locker. 'Why haven't you removed those barbaric decorations from your masks?'

The boys looked startled; Howe went on, 'Haven't you looked at the bulletin board this morning?'


1. The practice of painting respirator masks with so-called identification patterns will cease. Masks will be plain and each student will letter his name neatly in letters one inch high across the chest and across the shoulders of his outdoors suit.

(ed note: headmaster Howe is a stupid little power-mad bureaucrat who does not understand the realities of life out on the frontier)

From RED PLANET by Robert Heinlein. 1949

Safety Line

For strict safely, static lines or safety lines are mandatory. The line will have to be made of special materials, since most terrestrial ropes and cables will turn glass-like and shatter in vacuum.

The spacecraft should have plenty of small steel rings bolted at regular intervals over the hull for spacemen to attach their safety lines to. Without a static line, an astronaut who manages to get both magnetic boots separated from the hull will suddenly find themself on a slow impromptu tour of the solar system. If their spouses are real lucky the bodies might actually be eventually recovered for burial.

In the real world NASA generally always insisted that astronauts performing a spacewalk be tethered to the spacecraft or station. The first NASA untethered spacewalk was Bruce McCandless II's little jaunt with NASA MMU in Challenger mission STS-41-B.

Another useful item is a "line throwing gun". This allows one to shoot a safety line from one spacecraft to another.

There was an impressive use of tethers in episode #4 of The Expanse.

Our heroes are in the hangar bay of the Martian battleship Donnager. The ship has been boarded by hostiles, the captain is poised to scuttle, and our heroes had better get into the escape ship fast unless they want to die in the scuttling.

The Donnager is under 1 g acceleration so there is artficial gravity. Our heroes have been instructed to turn off their boot magnets and run as fast as they can across the gantry into the escape ship, while dodging gunfire.

Alas our heroes Naomi and Holden are only half way across the gantry when the Donnager is forced to turn off its engines. They are suddenly in free fall, and float helpessly away from the gantry.

But Holden is a seasoned, cool-thinking, steely-eyed spaceman. He grabs Namoi, attaches a tether connecting the two, then kicks Naomi upwards away from the gantry. Newton's Third Law to the rescue! Holden recoils to the gantry, his magnetic boots latch on, then he uses the tether to haul Naomi down to the gantry.

Brilliant use of a tether, and a astonishing use of real physics in a TV show.

     Holden grabbed for Naomi. He struggled to orient himself as the two of them spun across the bay with nothing to push off of and nothing to arrest their flight. They were in the middle of the room with no cover.
     The blast had hurled Kelly five meters through the air and into the side of a packing crate, where he was floating now, one magnetic boot connected to the side of the container, the other struggling to connect with the deck. Amos had been blown down, and lay flat on the floor, his lower leg stuck out at an impossible angle. Alex crouched at his side.
     Holden craned his neck, looking toward the attackers. There was the boarder with the grenade launcher who had blasted Kelly, lining up on them for the killing shot. We 're dead, Holden thought. Naomi made an obscene gesture.
     The man with the grenade launcher shuddered and dissolved in a spray of blood and small detonations.
     "Get to the ship!" Gomez screamed from the radio. His voice was grating and high, half shrieking pain and half battle ecstasy.
     Holden pulled the tether line off Naomi's suit.
     "What are you...?" she began.
     "Trust me," he said, then put his feet into her stomach and shoved off. Hard. He hit the deck while she spun toward the ceiling. He kicked on his boot mags and then yanked the tether to pull her down to him.
     The room strobed with sustained machine gun fire — Holden said, "Stay low," and ran as quickly as his magnetic boots would allow toward Alex and Amos. The mechanic moved his limbs feebly, so he was still alive. Holden realized he still had the end of Naomi's tether in his hand, so he clipped it on to a loop on his suit. No more getting separated.
From LEVIATHAN WAKES: Book One of The Expanse by James A. Corey (2011)

Fred braced himself in the open hatch and fired the line-throwing gun. The foam plastic projectile sailed slowly across the void, trailing the line it pulled from the container on the gun. A P-suited figure reached out and caught the slow-moving plastic blob as it sailed past. Fred snubbed the line on a cleat inside the hatch as the other person whipped it through and around a beam of the array. Torn had his running safety line snapped around the main line as quickly as it was secured at both ends. He pushed off and sailed down the line. Fred was behind him.

From SPACE DOCTOR by Lee Correy (G. Harry Stine) 1981

     I knew exactly where Mac had gone, but I had a hard time seeing him. The rock slide had carried with it a mixture of small and large fragments, from gravel and pebbles to substantial boulders. His struggles to climb the slope had only managed to embed him deeper in loose materials. Now his suit was three-quarters hidden. His efforts also seemed to have carried him backwards, so with a thirty degree gradient facing him I didn't think he'd ever be able to get out alone. And further down the slope lay a broad fissure in the surface, of indeterminate depth.
     He was facing my way, and he had seen me too. "Jeanie, don't come any closer. You'll slither right down here, the same as I did. There's nothing firm past the ledge you're standing on."
     "Don't worry. This is as far as I'm coming." I backed up a step, nearer to a huge rock that must have weighed many tons, and turned my head so the chest of Mac's suit sat on the crosshairs at the exact center of my display. "Don't move a muscle now. I'm going to use the Walton, and we don't have time for second tries."
     I lifted the crosshairs just a little to allow for the effects of gravity, then intoned the Walton release sequence. The ejection solenoid fired, and the thin filament with its terminal electromagnet shot out from the chest panel on my suit and flashed down towards McAndrew. The laser at the tip measured the distance of the target, and the magnet went on a fraction of a second before contact. Mac and I were joined by a hair-thin bond. I braced myself behind the big rock. "Ready? I'm going to haul you in."
     "Aye, I'm ready. But why didn't I think of using the Walton? Damnation, I didn't need to get you back here, I could have done it for myself."
     I began to reel in the line, slowly so that Mac could help by freeing himself from the stones and gravel. The Izaak Walton has been used for many years, ever since the first big space construction jobs pointed out the need for a way to move around in vacuum without wasting a suit's reaction mass. If all you want is a little linear momentum, the argument went, why not take it from the massive structures around you? That's all that the Waltons do. I'd used them hundreds of times in free fall, shooting the line out to a girder where I wanted to be, connecting, then reeling myself over there. So had Mac, and that's why he was disgusted with himself. But it occurred to me that this was the first time I'd ever heard of a Walton being used on a planetary surface.
     "I don't think you could have done it, Mac," I said. "This big rock's the only solid one you could see from down there, and it doesn't look as though it has a high metal content. You'd have nothing for the magnet to grab hold of up here."
     "Maybe." He snorted. "But I should have had the sense to try. I'm a witless oaf."
     What that made me, I dreaded to think. I went on steadily hauling in the line until he had scrabbled his way up to stand by my side, then switched off the field. The line and magnet automatically ran into their storage reel in my suit, and we carefully turned and headed back to the other two.

From ROGUEWORLD by Charles Sheffield (1983 )

Things get real nasty if the ship is a tumbling pigeon or otherwise rotates to provide artificial gravity. The poor EVA spacemen have to swing from hand-hold to hand-hold like trapezes artists. From their viewpoint, the spacecraft is overhead and below is a long fall to infinity. For details read Heinlein's short story "Ordeal in Space".


Astronauts also have to watch what they say. There is no air in space, so unless you are touching helmets together, you cannot talk with others without a radio. But while speaking on Terra means your voice becomes fainter with distance, over a radio it will be loud and clear out to the limit of the radio's range. This means cursing under your breath or muttering behind somebody's back will not work. There might be several channels to allow a bit of privacy, or if several conversations are going on at once.

"Do you think they're listening to us? Suppose someone's got a watch on this frequency—they'll have heard every word we've said. After all, we're in direct line of sight."

"Who's being melodramatic now? No one except the Observatory would be listening on this frequency, and the folks at home can't hear us as there's rather a lot of mountain in the way. Sounds as if you've got a guilty conscience; anyone would think that you'd been using naughty words again."

This was a reference to an unfortunate episode soon after Wheeler's arrival. Since then he had been very conscious of the fact that privacy of speech, which is taken for granted on Earth, not always available to the wearers of spacesuits, whose every whisper can be heard by anyone within radio range.

From EARTHLIGHT by Sir Arthur C. Clarke (1955)


Sometime people on a space walk want to communicate but do not want to use radio. This can be either due to the sad fact that one or both of the radio sets are out of order, or if the two have a strong motive not to broadcast their conversation to everybody in the universe within radio range.

  • Some SF novels suggest that two space suited people might turn off their raidos, and touch helmets. The theory is that the sound of the conversation will be conducted through the contact between helmets. However, others maintain that the area of contact will be so small (since the helmets are basically spherical) that no audible sound will manage to pass.

  • In Poul Anderson's TAU ZERO, he suggests astronauts will learn how to read lips. In the weaving sheds and cotton mills of Lancashire, workers developed an exaggerated form of speech and gesture called mee-mawing to facilitate lip-reading.

  • They can use a vacuum-rated marker pen to write words or Spacer's Runic.

  • Morse Code is another possibility, via flashlight or a mirror reflecting Sol. If they are connected by something that will transmit vibration (like a girder) they can use tap codes (Morse won't work with percussion because while you can tap a "dot" you cannot tap a "dash").

  • In The Expanse Belters use specialized hand gestures similar to those used by scuba divers and harbor crain longshoremen. These can also be used like Emoticons to supplement radio communication, e.g., using a fist to make a "nod-your-head-yes" gesture (non-verbal so radio doesn't send it, and mostly invisible unless you can see inside their helment). In The Expanse, Belters tend to use hand gestures even when not wearing a space suit, shrugging with their hands instead of their shoulders for instance.

  • In Larry Niven's "Known Space" series, belters do NOT perform any hand gestures at all. This is because Niven's belters fly in very small spacecraft called "singleships". The habitat module is only slightly larger than a coffin.
    "You noticed a habit of mine once. I never make gestures. All Belters have that trait. It's because on a small mining ship you could hit something waving your arms around. Something like the airlock button."
    "Sometimes it's almost eerie. You don't move for minutes at a time."
    The Warriors (1966)

  • Actually, NASA is looking into creating some "official" hand signals. The link shows some proposed signals.

  • One can use deaf sign language or a manually coded oral language. It is difficult to do full blown sign language in a space suit. Sign languages have complicated, nuanced signs that would get lost by the highly restricted motion of the suits. Only big motions would be visible.

  • If the two are connected by a tether, they can use scuba diver rope signals.

  • Sawmill workers had their own specialized hand signal language, because the noise in the mill is too loud for speaking. Something similar is used in steel pipe mills, where even radios are worthless due to the background noise.

      (ed note: the space cadets are on the hull of the spacecraft, being trained by Sergeant Hanako to use the space suit's rocket jets)

     A little more than a minute after cutting his jet, he jack-knifed to bring his boots in front of him and clicked on, about ten feet from the instructor.
     Hanako came over and placed his helmet against Mart’s so he could speak to him privately, with the radio shut off. “A good job, kid, the way you kept your nerve when you swung past. Okay—I’ll post you for advanced training.”
     Matt remembered to cut out his walky-talky. “Gee, thanks!”
     “You did it, not me.” Hanako cut back in the voice circuit. “Okay, there—number four.”
     Matt wanted to chase back to his room, find Tex, and do some boasting. But there were seven more to go. Some did well, some had to be fished out of difficulty.

     The last man outdid himself. He failed to cut off his power in spite of Hanako’s shouts for him to do so. He moved away from the ship in a wide curve and commenced to spin, while the sergeant whipped at the safety line to try to stop the spin and head him back. At the end of a long fifty seconds his power gave out; he was nearly a thousand feet away and still receding rapidly.
     The sergeant played him ike a fisherman fighting a barracuda, then brought him in very, very slowly, for there was no way to check whatever speed the tension on the line placed on him.
     When at last he was in, clicked down, and anchored by static line, Hanako sighed. “Whew!” he said. “I thought I was going to have to go get him.” He went to the cadet and touched helmets, radio off.
     The cadet did not shut off his instrument. “I don’t know,” they heard him reply. “The switch didn’t go bad—I just couldn’t seem to move a muscle. I could hear you shouting but I couldn’t move.”
     Matt went back to the airlock with the group, feeling considerably sobered. He suspected that there would be a vacant place at supper. It was the Commandant’s policy to get a cadet who was to be dropped away from the ship without delay. Matt did not question the practice, but it jarred him when he saw it happening—it brought the cold breath of disaster on his own neck.

From SPACE CADET by Robert Heinlein (1948)

      To the surprise of the twins Hazel did not continue the argument but followed her son docilely into the air lock. Mr Stone started down the rope ladder; Castor pulled his grandmother aside, switched off both her radio and his and pushed his helmet into contact with hers so that he might speak with her in private. ‘Hazel, what was wrong with the power plant? Pol and I went through this ship last week — I didn’t spot anything too bad.’
     Hazel look at him pityingly. ‘You’ve been losing sleep lately? It’s obvious — only four couches.’
     ‘Oh.’ Castor switched on his radio and silently followed his brother and father to the ground.

(ed note: context: Teenagers Castor and Pollux Stone want to buy a spaceship and make their fortunes in the asteroid belt. Mr. Stone thinks the twins are far too young to go gallivanting off by themselves. He decides to go shopping for a used four-accelerator-couch ship so he, his wife, grandmother Hazel, and the baby can go traveling. Castor and Pollux can stay home and go to boarding school.

Wiley grandmother Hazel is manipulating her son Mr. Stone into getting a ship that the entire family can fit in. As they look over a used ship that Mr. Stone favors, Hazel pitches a fit about the state of the ship's power plant. Mr. Stone demurrers to his mother's judgement. The twins know there is nothing wrong with the plant and ask grandmother Hazel what gives?)

From THE ROLLING STONES by Robert Heinlein (1952)

( ed note: on Luna, Kip and Peewee put on spacesuits and make their escape from the alien base)

     "Mind your pressure. Kip. You're swelling up too fast." I kicked the chin valve while watching the gauge—and kicking myself for letting a little girl catch me in a greenhorn trick. But she had used a space suit before, while I had merely pretended to.
     I decided this was no time to be proud. "Peewee? Give me all the tips you can. I'm new to his."
     "I will, Kip."
     The outer door popped silently and swung inward—and I looked out over the bleak bright surface of a lunar plain. For a homesick moment I remembered the trip-to-the-Moon games I had played as a kid and wished I were back in Centerville. Then Peewee touched her helmet to mine. "See anyone?"
     "We're lucky, the door faces away from the other ships. Listen carefully. We won't use radio until we are over the horizon—unless it's a desperate emergency. They listen on our frequencies. I know that for sure. Now see that mountain with the saddle in it? Kip, pay attention!"
     "Yes." I had been staring at Earth. She was beautiful even in that shadow show in the control room—but I just hadn't realized. There she was, so close I could almost touch her … and so far away that we might never get home. You can't believe what a lovely planet we have, until you see her from outside … with clouds girdling her waist and polar cap set jauntily, like a spring hat. "Yes. I see the saddle."
     "We head left of there, where you see a pass. Tim and Jock (thugs working for the aliens) brought me through it in a crawler. Once we pick up its tracks it will be easy. But first we head for those near hills just left of that—that ought to keep this ship between us and the other ships while we get out of sight. I hope."
     It was twelve feet or so to the ground and I was prepared to jump, since it would be nothing much in that gravity. Peewee insisted on lowering me by rope. "You'll fall over your feet. Look, Kip, listen to old Aunt Peewee. You don't have Moon legs yet. It's going to be like your first time on a bicycle."
     So I let her lower me and the Mother Thing while she snubbed the nylon rope around the side of the lock. Then she jumped with no trouble. I started to loop up the line but she stopped me and snapped the other end to her belt, then touched helmets. "I'll lead. If I go too fast or you need me, tug on the rope. I won't be able to see you."

From HAVE SPACE SUIT, WILL TRAVEL by Robert Heinlein (1958)

(ed note: "Tiny" Larsen is the man in charge of buiding Space Station One. Which is an engineering feat bigger than the Panama Canal. His construction crew is stag, all male, by design. He has to fire one of the radiomen when they invent a magnetic way of gambling with dice in free fall, including cheating. The replacement, G. Brooks McNye arrives by rocket. But the rocket departs before Tiny discovers the "G" is for "Gloria".

Tiny figures construction crew moral will tank, and keeps her chaperoned as much as possible. Which isn't much since they need two radiomen to cover all the shifts. Gloria is competent enough, as a matter of fact she trained the current radioman.

Things get testy on the day when they perform the dangerous operation of spinning up the station using JATO units.)

     Men in space suits all look alike; we used numbers and colored armbands. Supervisors had two antennas, one for a gang frequency, one for the supervisors' circuit. With Tiny and me the second antenna hooked back through the radio shack and to all the gang frequencies—a broadcast.
     The supervisors had reported their men clear of the fireworks and I was about to give Tiny the word, when this figure came climbing through the girders, inside the danger zone. No safety line. No armband. One antenna.
     Miss Gloria, of course. Tiny hauled her out of the blast zone, and anchored her with his own safety line. I heard his voice, harsh in my helmet: "Who do you think you are? A sidewalk superintendent?"
     And her voice: "What do you expect me to do? Go park on, a star?"
     "I told you to stay away from the job. If you can't obey orders, I'll lock you up."
     I reached him, switched off my radio and touched helmet. "Boss! Boss!" I said. "You're broadcasting!"
     "Oh—" he says, switches off, and touches helmets with her. We could still hear her; she didn't switch off. "Why, you big baboon, I came outside because you sent a search party to clear everybody out," and, "How would I know about a safety line rule? You've kept me penned up." And finally, "We'll see!"

(ed note: As it turned out, Tiny was wrong. The construction crew moral soared, and construction was actually ahead of schedule.)

From DELILAH AND THE SPACE-RIGGER by Robert Heinlein (1949)

      Something smashed into his back with a force that knocked the breath out of him. For a heart-freezing moment he thought his air-tanks had gone, his suit torn open and that he was already sucking frenziedly at vacuum. But his gasp of pure terror brought air rushing into his lungs. Conway had never known canned air to taste so good.
     The AACL’s tentacle had only caught him a glancing blow—his back wasn’t broken—and the only damage was a wrecked suit radio.
     “Are you all right?” Conway asked anxiously when he had Williamson settled in the compartment above. He had to press his helmet against the other’s—that was the only way he could make himself heard now.
     For several minutes there was no reply, then the weary, pain-wrecked near-whisper returned.
     “My arms hurt. I’m tired,” it said haltingly. “But I’ll be OK when… they take me… inside.” Williamson paused, his voice seemed to gather strength from somewhere and he went on, “That is if there is anybody left alive in the hospital to treat me. If you don’t stop our friend down there…”
     Sudden anger flared in Conway. “Dammit, do you never give up?” he burst out. “Get this, I’m not going to kill an intelligent being! My radio’s gone so I don’t have to listen to Lister and Mannon yammering at me, and all I’ve got to do to shut you up is pull my helmet away from yours.

From HOSPITAL STATION by James White (1962)

Lindgren and Reymont exchanged a look above his bent back. She shaped unspoken words. Once he had taught her the Rescue Corps trick of lip reading when spacesuit radios were unusable. They had practiced it as something that made them more private and more one.

From TAU ZERO by Poul Anderson (1970)

(ed note: This is about working in British weaving sheds in the early 1900s)

     A weaving shed in full song is a noisy animal, the roar would be disconcerting to anyone not used to it. None of the weavers wore ear defenders and many had a low level of hearing loss after years of exposure. Many thousands of pounds were spent on experiments to lessen the noise but all of them failed and right to the end of the industry the Lancashire loom made as much noise as it did when it was first invented.
     There was one small consolation, the noise was low frequency and nowhere near as damaging as modern high speed looms so it wasn’t as bad as some would like to portray it. However, it made communication in the shed by normal speech almost impossible.
     The weavers found a way round this, they used to ‘mee maw’ to each other. This was using exaggerated lip movements With no sound so they can lip-read each other. If a weaver wanted to say something privately to another weaver she would place her mouth very close to her friend’s ear so nobody could see her lip movements. If I wanted to spread a message round the shed, say if I was stopping early for some reason, all I had to do was go to the door of the shed, mee maw my message to the first weaver inside the door and before I had walked back to the engine house everyone in the shed had the message.

From BANCROFT by Stanley Graham (2009)

      They stopped at the Locker Rooms at East Lock and suited up. As usual, (grandmother) Hazel unbelted her gun and strapped it to her vacuum suit. None of the others was armed; aside from civic guards and military police no one went armed in Luna City at this late date except a few of the very old-timers like Hazel herself. Castor said ‘Hazel, why do you bother with that?’
     ‘To assert my right. Besides, I might meet a rattlesnake.’
     ‘Rattlesnakes? On the Moon? Now, Hazel!’
     ‘“Now, Hazel”’ yourself. More rattlesnakes walking around on their hind legs than ever wriggled in the dust. Anyhow, do you remember the reason the White Knight gave Alice for keeping a mouse trap on his horse?
     ‘Uh, not exactly.’
     ‘Look it up when we get home. You kids are ignorant Give me a hand with this helmet.’
     The conversation stopped, as Buster was calling his grandmother and insisting that they start their game. Castor could read her lips through her helmet; when he had his own helmet in place and his suit radio switched on he could hear them arguing about which had the white men last game. Hazel was preoccupied thereafter as Buster, with the chess board in front of him, was intentionally hurrying the moves, whereas Hazel was kept busy visualising the board.

From THE ROLLING STONES by Robert Heinlein (1952)

"We'll already have stopped," Holden said, and McDowell patted at the air with his wide, spidery hands. One of the many Belter gestures that had evolved to be visible when wearing an environment suit.

From LEVIATHAN WAKES by "James S.A. Corey" 2011. First novel of The Expanse

(ed note: Rick is only 15 years old, on his first trip to the moon colony. He is excited about his first lunar excursion with the local scouting troop. Unfortunately he does not understand the 24 hour clock, so arrives at the debarking airlock twelve hours early.)

It was eight forty-five when he reached the recessed doorway that was one of the entrances to the North-Down lock area.

Sensors responded to his arrival, triggering a flashing light—green, since there was safe pressure on the other side of the door. Rick, as he had been taught, flicked the "acknowledge reading" switch located high on the door frame. Then he activated the door switch itself. Despite the need for power economy, doors on the moon that opened into areas even moderately likely to tap vacuum were motor-driven. The chamber Rick entered was not normally exhausted; it was a sort of combined garage and locker-room. However, it did have a large direct exit to the surface for getting out unusually large pieces of equipment. When so used it became an air-lock chamber.

On every moon-dweller's mind there was always the possibility of leakage or outright valve failure in any outer room. Rick was aware of that threat, just as the schoolkids he had met a few days before had been aware of rain and cold on Earth. It was the Big Difference everyone was told about. But awareness was not the same thing as the reflective self-protection of a native.

With the door secured behind him-by a strictly manual latch, activation of which shut off a warning bell—he made his way to the main personnel exits. His fervent hope was that the group might still be there.

"Sir, I seemed to have missed a group going out to Picard G. Could you tell me how long ago they left?"

Montaux shook his head, at the same time making the negative hand-gesture habitual to people who spent much of their time in space suits.

Probably the one biggest mistake, of course, was made when he walked silently to the numbered locker his uncle had told him would contain his suit, and pulled it out. He donned it quickly and correctly under the attendant's eyeand who, Jim Talles. asked the world later, would have foreseen that the earlier training session thus would turn out to be a mistake?

If Rick had been slow or clumsy, if Pierre Montaux had had the slightest grounds for suspecting Rick Suspee never before had ventured into vacuum … But there was nothing to warn Pierre. The suit went on smoothly. It fitted correctly. Rick attached helmet and gauntlets properly, did the proper things to seal them. He made the proper signals to request tightness check, said the right things over the radio for the communications check. He strode over to the inner lock door, deftly operated the cycling switch, and waited until the inner light flashed green before opening the portal. There was nothing to show that he had not done it all a score, even a hundred, times before.

Montaux let him through, checked the manual seal on the inside after the door closed, and gestured a "proceed" through the transparent wall. The outer door's light was now green. Rick operated its plainly labeled opening switch, went through, closed it, and disappeared from the sight of Pierre Montaux. And, for many hours, from the sight of mankind.

From MISTAKEN FOR GRANTED by Hal Clement (1974)

      UN Marines were charging the Martian outpost. The yearlong cold war was going hot. Somewhere deep behind the cool mental habits of training and discipline, she was surprised. She hadn’t really thought this day would come.
     The rest of her platoon were out of the outpost and arranged in a firing line facing the UN position. Someone had driven Yojimbo out onto the line, and the four-meter-tall combat mech towered over the other marines, looking like a headless giant in power armor, its massive cannon moving slowly as it tracked the incoming Earth troops. The UN soldiers were covering the 2,500 meters between the two outposts at a dead run.
     Why isn't anyone talking? she wondered. The silence coming from her platoon was eerie.
     And then, just as her squad got to the firing line, her suit squealed a jamming warning at her. The top-down vanished as she lost contact with the satellite. Her team’s life signs and equipment status reports went dead as her link to their suits was cut off. The faint static of the open comm channel disappeared, leaving an even more unsettling silence.
     She used hand motions to place her team at the right flank, then moved up the line to find Lieutenant Givens, her CO. She spotted his suit right at the center of the line, standing almost directly under Yojimbo. She ran up and placed her helmet against his.
     "What the f**k is going on, El Tee?" she shouted.
     He gave her an irritated look and yelled, “Your guess is as good as mine. We can’t tell them to back off because of the jamming, and visual warnings are being ignored. Before the radio cut out, I got authorization to fire if they come within half a klick of our position."

From CALIBAN'S WAR by "James S.A. Corey" 2012. Second novel of The Expanse

He gave a start as a pair of mittened paws grasped his upper arms and a helmet clinked against his. He found himself staring into the raw red features of the U.S. repair-crew foreman, a likable, plain-spoken man named Grogan. Grogan was being smart enough not to use his suit radio (because this is a joint US-Chinese expedition, the two nations are at "cold-war" status, and the place is swarming with security agents from both nations).

“Beg pardon, sir,” Grogan said, “but what’s going on? We saw the landing leg spring loose through the telescope, but that’s all.”

Jameson pressed his helmet against the other man’s. “Tell you all about it later. For now, just make sure that everything you replace in the locking mechanism is all right. Particularly the bolts.”

From THE JUPITER THEFT by Donald Moffitt (1977)

     In the 1970s, sawmill workers could talk about technical matters or insult each other in their own special sign language.
     When the linguists Martin Meissner and Stuart Philpott first started visiting sawmills in British Columbia in the 1970s, they thought they’d find workers communicating without speaking, probably with some simple gestures that contained technical information. There was a long history of such communication in the face of extreme noise: For centuries, American mill workers had used systems of hand signals to tell each other, across the unending roar of the saws, how to cut wood.
     What they discovered, though, floored them. The researchers witnessed a sign language system complete enough that workers could call each other “you crazy old farmer,” tell a colleague that he was “full of crap,” or tell each other when the foreman was “f*****g around over there.”
     Outside of deaf communities, hearing people sometimes develop what are now often called “alternate sign languages” to communicate when words will not do. In monasteries, monks uses signs to communicate in areas where speech is forbidden, for instance. In industries where machines made speaking impossible—in ships’ engine rooms, in steel mills, textile mills, and sawmills—workers also found ways to communicate with their hands.
     In 1955, when Popular Mechanics covered these industrial sign languages, many were already disappearing. But in the 1970s, Meissner and Philpott found a sign language still used in sawmills. Their research further honed in on the culture of one particular mill where workers had developed a system of 157 signs that they used not just to communicate about their work but to trade small talk, tell crude jokes and tease each other.
     The linguist were struck by the language’s “ingenuity and elegance,” they wrote. It was also a secret hidden in plain sight: the mill workers’ bosses, it seems, had almost no idea what they were saying.
     The core of the sawmill workers’ sign language was a system of numbers, standardized across the industry. Those signs were shared in a technical notebook, and, the linguists wrote,”in the view of the management, that was about all there was to the language.” But it covered much more ground than technical communication. Workers could talk about quitting time, lunch time, and cigarette breaks. They could talk about sports and the bets they placed on games. They could talk about their wives, cars, and colleagues. They could tell jokes and comment on what was going on around them without their bosses ever knowing.

     Compared to a fully developed sign language, which can have thousands of signs, this one was limited in its scope. It did provide these men with a way to cover the basic grounds of collegial small talk, and in at least one case, sawmill sign language also worked in the home. A couple of years after Meissner and Philpott published their research on British Columbia’s mills, another linguist, Robert Johnson, found a retired sawmill worker in Oregon who had lost his hearing and used a variant on sawmill sign language to communicate with his wife and son, who was also deaf. About three-quarters of their corpus of 250 signs overlapped with the British Columbia sawmill signs Meissner and Philpott had collected. There was also significant overlap with American Sign Language.

Hull Sealant


Betty responded smoothly to the control; he let her drift outward for a hundred feet, then checked her forward momentum and spun her round so that he was looking back at the ship. Then he began his tour of the pressure hull.

His first target was a fused area about half an inch across, with a tiny central crater. The particle of dust that had impacted here at over a hundred thousand miles an hour was certainly smaller than a pinhead, and its enormous kinetic energy had vaporized it instantly. As was often the case, the crater looked as if it had been caused by an explosion from inside the ship; at these velocities, materials behaved in strange ways and the laws of common-sense mechanics seldom applied.

Poole examined the area carefully, then sprayed it with sealant from a pressurized container in the pod's general-purpose kit. The white, rubbery fluid spread over the metal skin, hiding the crater from view. The leak blew one large bubble, which burst when it was about six inches across, then a much smaller one, then it subsided as the fast-setting cement did its work. He watched it intently for several minutes, but there was no further sign of activity. However, to make doubly certain, he sprayed on a second layer; then he set off toward the antenna.

From 2001 A SPACE ODYSSEY by Arthur C. Clarke (1968)

      He waved a mechanic over to him. “Mr. Syaloch would like you to explain your outfit,” he said with ponderous sarcasm.
     “Sure. Regular spacesuit here, reinforced at the seams.” The gauntleted hands moved about, pointing. “Heating coils powered from this capacitance battery. Ten-hour air supply in the tanks. These buckles, you snap your tools into them, so they won’t drift around in free fall. This little can at my belt holds paint that I spray out through this nozzle.”
     “Why must spaceships be painted?” asked Syaloch. “There is nothing to corrode the metal.”
     “Well, sir, we just call it paint. It’s really gunk, to seal any leaks in the hull till we can install a new plate, or to mark any other kind of damage. Meteor punctures and so on.” The mechanic pressed a trigger and a thin, almost invisible stream jetted out, solidifying as it hit the ground.
     “But it cannot readily be seen, can it?” objected the Martian. “I, at least, find it difficult to see clearly in airlessness.”
     “That’s right, Light doesn’t diffuse, so…well, anyhow, the stuff is radioactive—not enough to be dangerous, just enough so that the repair crew can spot the place with a Geiger counter.
     “I understand. What is the half-life?”
     “Oh, I’m not sure. Six months, maybe? It’s supposed to remain detectable for a year.”

From THE MARTIAN CROWN JEWELS by Poul Anderson (1958)


RocketCat sez

This, space cadets, is a Radar Gun. Don't roll your eyes at this thing, newbie, I know whatcha thinking and you're dead wrong. Emphasis on "dead."

You think you're some kind of Lensman Kimball Kinnison with a "Look of Eagles" who don't need no stupid kindergarten training-wheels radar gun to tell your closing rate. You think you can just eyeball it.

You also think you're actually going to survive longer than five minutes in your first EVA because you are a clueless newbie with delusions of competence. Do a search in InterPlaNetPedia for the Dunning-Kruger effect and you'll see a picture of you.

Just ask Vasily Tsibliyev.

On 25 June 1997 those bean-counting morons at Roscosmos thought they could save a few rubles by eliminating the Kurs automated docking system and instead do it manually. When the Soviet Union disintegrated in 1991 the Kurs network became the property of the Ukraine, who immediately started price-gouging Roscosmos. So the bean counters figured to heck with the Ukraine, who needs that fancy-smancy Kurs anyway? Our boys in Roscosmos have the Look of Eagles, they can just eyeball it. For free.

Poor Vasily got stuck with the honor of being the first to try it. He was tasked with the job of sitting in the Mir space station and trying to dock the Progress M-34 by remote control. By eyeball, with no Kurs automated docking system for help.

What a smash up!

Vasily couldn't even begin to tell by eye the distance or closing rate. When he suddenly realized that the Progress was up to ramming speed, he floored the braking rockets, but it was too late. Progress clobbered a solar panel then plowed into Mir's Spektr module. It ruined the solar panel, crumpled a radiator, and punched a hole in Spektr’s hull which immediately started spewing vital breathing mix into the depths of space. Oh, and it put the entire station into a tail spin as well, because the ruined solar panel was the one powering the gyros which ordinarily prevented just such an occurrence. The spin made the remaining solar panels not facing the sun anymore, so now there was no solar power at all.

The cosmonauts managed to radio ground control enough info on the station's spin so it could be stopped, which is the only reason they didn't all die. That and their frantic efforts to plug the air leak.

After all the finger pointing and recriminations had died down a bit, Roscosmos did some ground simulations with five veteran cosmonauts to see if the concept would work in theory. Because they really hated being gouged by the Ukraine. And the bean counters really wanted to deflect the blame aimed at them so it would land on poor Vasily.

Unfortunately for the bean-counters, all five cosmonauts crashed their ships in the ground simulators. Now the bean-counters faced awkward questions about "why the flaming frak didn't you idiots try ground simulations first before you tried it live?"

The point is, you newbie, the human eye was not built to judge ranges and closing rates in airless space. It is used to judging distance by how the dusty air obscures things with distance. AND IF YOU HAVEN'T FIGURED IT OUT BY NOW THERE AIN'T NO FREAKING AIR IN SPACE!

Just be sure you have your last will and testament on file at the front office.

Astronauts may also need a "beeper". This is a low powered radar used to locate small objects nearby (like that zero-recoil wrench you let go of "just for a minute" which seems to have run away). You wave it around until is starts beeping (heard over your suit radio). As you approach the object the beep rate increases.

If you are doing space construction work or asteroid mining, you'll need a radar range-and-rate gun. This is similar to the radar guns the highway patrol uses to catch speeders, but it also tells the range. It gives you the precise distance to the object and the current closing rate between you and the object, using radar for range and doppler radar for closing rate.

This is important because it is almost impossible to tell the range to an object by eye in space. And even more impossible to tell how fast it is approaching or receding from you. This is a standard instrument on spacecraft and space taxis but not on a space suit.


'I'll borrow a Beeper from Stores,' replied Peter. 'Joe Evans will let me sign for one.'

A Beeper, I should explain, is a tiny radar set, not much bigger than a hand-torch, which is used to locate objects that have drifted away from the Station. It's got a range of a few miles on anything as large as a space-suit, and could pick up a ship a lot farther away. You wave it around in space and when its beam hits anything you hear a series of 'Beeps'. The closer you get to the reflecting object, the faster the beeps come, and with a little practice you can judge distances pretty accurately.

From ISLANDS IN THE SKY by Arthur C. Clarke, 1952.

(ed note: Coyote Westlake is in a small habitat module attached to the asteroid RA45, with her ship the Vegas Girl parked nearby. When she wakes up, she is startled to discover that the Vegas Girl is now far away from the asteroid.)

How the hell could this have happened? She had left the Vegas Girl in a perfectly matched orbit relative to RA45. There was no way she could have drifted that far while Coyote was asleep.

Unless she had been sleeping for one hell of a long time. She checked her watch and compared it to the time display on the hab shed’s chronometer. She even checked the date, just to be sure she hadn’t slept around the clock. But no, she had been out only a few hours. How far had her ship drifted?

Coyote grabbed the radar range-and-rate gun out of its rack and aimed it through the spaceward viewport, lining up the sights on the Girl. It was a low-power portable unit, not really meant to work at long range. Normally she used it to establish distance from and velocity toward an asteroid, but it could track her ship just as handily. She got the blinking strobe in the sights and pulled the trigger.

The gun pinged cheerfully twice to indicate it had gotten a good range and rate on its target. Coyote checked the gun’s tracking data display.

And her heart nearly stopped. The Vegas Girl was over one hundred kilometers astern, and the ship was moving away at over three hundred meters a second.

But wait a moment. The tracker just showed relative velocity, not which object was doing the moving. She peered out the port again, and spotted the triple-blink beacon she had left on RA46, the last rock she had worked. She swore silently. RA46 was in the wrong part of the sky. She fired a ranging pulse at it and got back virtually the same velocity value. The Girl was stationary relative to RA46. So it wasn’t the ship moving. It was this rock.

From THE RING OF CHARON by Roger MacBride Allen (1990)

spotter (n.): An ancient spacer’s tool, dating back almost as far as the navigator’s sextant, the engineer’s multi, or the medtech’s hand effector, used for locating and profiling distant objects in space: a boon to anyone who has to manage a docking bay, shift cargo in microgravity, perform extravehicular activities in crowded neighborhoods, or engage in the smallest of small-craft operations, which is to say, riding a candle.

The original spotters were no more than handheld radar transceivers with direct audio feedback into the user’s helmet interface. Wave it around, and when you hear beeping, it’s pointing at something. The faster the beeping, the closer that something is to you. Learning what a particular rate meant in terms of range, and keeping an ear on the change of beep rate, were left as skills for the user to develop.

The modern spotter is a rather more sophisticated device, thanks to miniaturization and commercial development. HUD feedback now monitors its position relative to your body to provide a more accurate sense of direction, and even the most basic models provide precise range and closing rate information. More advanced models use a phased-array antenna to sweep the beam across a target once detected, providing a profile for target recognition purposes and an estimate of spin.

Of course, there is in theory very little use for a spotter in the current age of space, since all spacecraft from the largest to the smallest include a transponder, and are further constructed from LOP-compliant hardware which will obligingly disclose its location upon receiving a network request. The Grand Survey has detailed charts of every object in space larger than a child’s ball. All objects within range should therefore, says theory, already be highlighted on your HUD.

It is a sign of the tremendous respect that spacer culture has for theory that there are at least a brace of spotters stored in every airlock and docking bay from the Core to the Rim.

– A Star Traveler’s Dictionary

From PING by Alistair Young (2016)

Signal Flare

A flare is a chemical pyrotechnic that produces a brilliant light without an explosion. As spacesuit gear, they would probably be for purposes of emergency illumination or as a maritime distress signal.


The calculator in his head proceeded with its business. Of those American vessels near the Argonne when first contact was made with the enemy, only the Washington was sufficiently massive to go out in a blast of yonder size and shape. If that was the case Captain Martin Diaz of the United States Astromilitary Corps was a dead man. The other ships of the line were too distant, traveling on vectors too unlike his own, for their scout boats to come anywhere close. On the other hand, it might well have been a Unasian battlewagon. Diaz had small information on the dispositions of the enemy fleet. He’d had his brain full just directing the torp launchers under his immediate command. If that had indeed been a hostile dreadnaught that got clobbered, surely none but the Washington could have delivered the blow, and its boats would be near—


For half a second Diaz was too stiffened by the sight to react. The boat ran black across waning clouds, accelerating on a streak of its own fire. The wings and sharp shape that were needed in atmosphere made him think of a marlin he had once hooked off Florida, blue lightning under the sun—Then a flare was in his hand, he squeezed the igniter and radiance blossomed.

Just an attention-getting device, he thought, and laughed unevenly as he and Bernie Sternthal had done, acting out the standard irreverences of high school students toward the psych course. But Bernie had left his bones on Ganymede, three years ago, and in this hour Diaz’s throat was constricted and his nostrils full of his own stench. He skyhooked the flare and hunkered in its harsh illumination by his radio transmitter. Clumsy in their gauntlets, his fingers adjusted controls, set the revolving beams on SOS. If he had been noticed, and if it was physically possible to make the velocity changes required, a boat would come for him. The Corps looked after its own.

Presently the flare guttered out. The pyre cloud faded to nothing. The raft deck was between Diaz and the shrunken sun. But the stars that crowded on every side gave ample soft light. He allowed his gullet, which felt like sandpaper, a suck from his one water flask. Otherwise he had several air bottles, an oxygen reclaim unit, and a ridiculously large box of Q rations. His raft was a section of inner plating, torn off when the Argonne encountered the ball storm. She was only a pursuit cruiser, unarmored against such weapons. At thirty miles per second, relative (260 Ricks! Each 1kg ball does 50% the damage of a Tomahawk cruise missile), the little steel spheres tossed in her path by some Unasian gun had not left much but junk and corpses. Diaz had found no other survivors. He’d lashed what he could salvage onto this raft, including a shaped torp charge that rocketed him clear of the ruins. This far spaceward he didn’t need screen fields against solar particle radiation. So he had had a small hope of rescue. Maybe bigger than small, now.

Unless an enemy craft spotted him first. His scalp crawled with that thought. His right arm, where the thing he might use in the event of capture lay buried, began to itch (he has an implanted isotopal explosive device, to be detonated when taken aboard a hostile ship). But no, he told himself, don’t be sillier than regulations require. That scoutboat was positively American. The probability of a hostile vessel being in detection range of his flare and radio—or able to change vectors fast enough—or giving a damn about him in any event—approached so close to zero as made no difference.

From KINGS WHO DIE by Poul Anderson (1962)

Cherry Picker

Sometimes astronauts have to repair or service items that are not directly connected to their spacecraft. Breaking contact with the ship is possible by using an MMU, but is always risky. A useful compromise is using the cherry picker concept, having the astronaut's feet attached to a aerial work platform based on the spacecraft, and the platform's arm maneuvers to position the astronaut.

On the International Space Station, this is done with the amazing Canadarm2 (successor to the original Canadarm).

Suit Into Ship

As one adds more gadgets and attachments to a space suit, it gradually morphs into a tiny spaceship. It starts with spring-loaded broomsticks and picks up speed with the addition of tiny attitude jets and maneuvering rockets. As a parallel development, a rocket engine with a skeletal frame to hold astronauts is the first "space taxi". When a space suit is massive enough that one climbs into it instead of putting it on like clothing, equipped with mechanical arms and waldoes, you suddenly have a space pod. Then if the pod grows to the size of a baby spaceship, but with massive over-sized engines, you finally have a space tug.


A broomstick is a spring loaded gizmo used by astronauts to launch themselves from place to place, and to bring themselves to a stop upon arrival.

... This was where the broomsticks came in.

Commander Doyle had invented them, and the name, of course, came from the old idea that once upon a time witches used to ride on broomsticks. We certainly rode around the station on ours. They consisted of one hollow tube, sliding inside another. The two were connected by a powerful spring, one tube ending in a hook, the other in a wide rubber pad. That was all there was to it. If you wanted to move, you put the pad against the nearest wall and shoved. The recoil launched you into space, and when you arrived at your destination you let the spring absorb your velocity and bring you to rest. Trying to stop yourself with your bare hands was liable to result in sprained wrists.

It wasn't quite as easy as it sounds, though, for if you weren't careful you could bounce right back the way you'd come.

From ISLANDS IN THE SKY by Arthur C. Clarke, 1952.

There are some professions which have evolved unique and characteristic tools — the longshoreman's hook, the potter's wheel, the bricklayer's trowel, the geologist's hammer. The men who had to spend much of their time on zero-gravity construction projects had developed the broomstick.

It was very simple — a hollow tube just a metre long, with a footpad at one end and a retaining loop at the other. At the touch of a button, it could telescope out to five or six times its normal length, and the internal shock-absorbing system allowed a skilled operator to perform the most amazing manoeuvres. The footpad could also become a claw or hook if necessary; there were many other refinements, but that was the basic design. It looked deceptively easy to use; it wasn't.

Everything happened in about five seconds. Brailovsky triggered his broomstick, so that it telescoped out to its full length of four metres and made contact with the approaching ship. The broomstick started to collapse, its internal spring absorbing Brailovsky's considerable momentum; but it did not, as Curnow had fully expected, bring him to rest beside the antenna mount. It immediately expanded again, reversing the Russian's velocity so that he was, in effect, reflected away from Discovery just as rapidly as he had approached. He flashed past Curnow, heading out into space again, only a few centimetres away. The startled American just had time to glimpse a large grin before Brailovsky shot past him.

A second later, there was a jerk on the line connecting them, and a quick surge of deceleration as they shared momentum. Their opposing velocities had been neatly cancelled; they were virtually at rest with respect to Discovery. Curnow had merely to reach out to the nearest handhold, and drag them both in.

From 2010: Odyssey Two by Arthur C. Clarke, 1982.

Rocket Pack

While engaging in extra-vehicular activity, our space-suited rocketeers may use a "broomstick", or some kind of small jets (a Manned Maneuvering Unit or MMU). NASA has also developed a nitrogen-gas propelled unit that fits on the backpack, called the Simplified Aid for Extravehicular Activity Rescue (SAFER). The SAFER can help an astronaut return to the shuttle or station in the event that they gets separated from the spacecraft. SAFER has a deltaV capacity of 3 m/s.

Space Cadet by Robert Heinlein (1948)
The training rocket packs have 15 m/s of delta V for a space-suited astronaut of 136 kilograms of mass (standard rocket packs have more).
Destination Moon (1950)
The crew used an industrial tank of oxygen as an impromptu thruster to rescue one of the astronauts who foolishly allowed both of his magnetic boots to detach from the ship's hull.
Lucky Starr and the Pirates of the Asteroids by Issac Asimov (1953)
Astronauts used push-units: a torus-shaped pressurized tank of carbon dioxide around the astronaut's waist, connected by tube to the L-shaped push gun.
Revolt on Alpha C by Robert Silverberg (1955)
Astronauts carried a slugthowing pistol with four bullets as a hand-held maneuvering unit. In reality this is not very efficient. A .45 automatic will give a 68 kg person about 0.088 m/s deltaV per bullet, closer to 0.044 m/s if the person+spacesuit mass is 136 kg.
Comic Book Space 1999 No 6 (1976)
Commander Koenig uses his space suit's oxygen tanks as emergency maneuvering jets to retrieve the space helmet before he suffocates.
2010 The Year We Make Contact (1984)
They retained Brailovsky's shared momentum trick from the novel, but replaced the broomstick with a thruster pack. The broomstick automatically retains the exact velocity, with a thruster you have to be sure to do a precise burn of the same magnitude in the opposite direction.


     "The trick to jetting yourself in space,"—he went on, 'lies in balancing your body on the jet—the thrust has to pass through your center of gravity. If you miss and don't correct it quickly, you start to spin, waste your fuel, and have the devil's own time stopping your spin. "It's no harder than balancing a walking stick on your finger—but the first time you try it, it seems hard.
     "Rig out your sight." He touched a stud at his belt; a light metal gadget snapped up in front of his helmet so that a small metal ring was about a yard in front of his face. "Pick out a bright star, or a target of any sort, lined up in the direction you want to go. Then take the ready position— no, no! Not yet—I'll take it."
     He squatted down, lifted himself on his hands, and very cautiously broke his boots loose from the side, then steadied himself on a cadet within reach. He turned and stretched out, so that he floated with his back to the ship, arms and legs extended. His rocket jet stuck straight back at the ship from the small of his back; his sight stuck out from his helmet in the opposite direction.
     He went on, "Have the firing switch ready in your right hand. Now, have you fellows ever seen a pair of adagio dancers? You know what I mean—a man wears a piece of leopard skin and a girl wearing less than that and they go leaping around the stage, with him catching her?"
     Several voices answered yes. Hanako continued, "Then you know what I'm talking about. There's one stunt they always do—the girl jumps and the man pushes her up and balances her overhead on one hand. He has his hand at the small of her back and she lays there, artistic-like. "That's exactly the way you got to ride a jet. The push comes at the small of your back and you balance on it. Only you have to do the balancing—if the push doesn't pass exactly through your center of gravity, you'll start to turn. You can see yourself starting to turn by watching through your sight. "You have to correct it before it gets away from you. You do this by shifting your center of gravity. Drag in the arm or leg on the side toward which you've started to turn. The trick is—"

     "Just a second, Sarge," someone cut in, "you said that just backwards. You mean; haul in the arm or leg on the other side, don't you?"
     "Who's talking?"
     "Lathrop, number six. Sorry."
     "I meant what I said, Mr. Lathrop."
     "Go ahead, do it your way. The rest of the class will do it my way. Let's not waste time. Any questions? Okay, stand clear of my jet."

     The half circle backed away until stopped by the anchored static lines. A bright orange flame burst from the sergeant's back and he moved straight out or "up," slowly at first, then with increasing speed. His microphone was open; Matt could hear, by radio only, the muted rush of his jet—and could hear the sergeant counting seconds: "And … one! … and … two! … and … three!" With the count of ten, the jet and the counting stopped.
     Their instructor was fifty feet "above" them and moving away, back toward them. He continued to lecture. "No matter how perfectly you've balanced you'll end up with a small amount of spin. When you want to change direction, double up in a ball—" He did so. "—to spin faster—and snap out of it when you've turned as far as you want." He suddenly flattened out and was facing them. "Cut in your jet and balance on it to straighten out on your new course—before you drift past the direction you want."
     He did not cut in his jet, but continued to talk, while moving away from them and slowly turning. "There is always some way to squirm around on your axis of rotation so that you can face the way you need to face for a split second at least. For example, if I wanted to head toward the Station—" Terra Station was almost a right angle away from his course; he went through contortions appropriate to a monkey dying in convulsions and again snapped out in starfish spread, facing the Station—but turning slow cartwheels now, his axis of rotation unchanged.
     "But I don't want to go to the Station; I want to come back to the ship." The monkey died again; when the convulsions ceased, the sergeant was facing them. He cut in his jet and again counted ten seconds. He hung in space, motionless with respect to the ship and his class and about a quarter mile away. "I'm coming in on a jet landing, to save time." The jet blasted for twenty seconds and died; he moved toward them rapidly.
     When he was still a couple of hundred feet away, he flipped over and blasted away from the ship for ten seconds. The sum of his maneuvers was to leave him fifty feet away and approaching at ten feet per second. He curled up in a ball again and came out of it feet toward the ship.

     Five seconds later his boots clicked to steel and he let himself collapse without rebound. "But that is not the way you'll do it," he went on. "My tanks hold more juice than yours do—you've got fifty seconds of power, with each second good for a change of speed on one foot-second—that's for three hundred pounds of mass (15 m/s of delta V for 136 kilograms of mass); some of you skinny guys will go a little faster.
     "Here's your flight plan: ten seconds out, counted. Turn as quick as you can and blast fifteen seconds back. That means you'll click on with five foot-seconds. Even your crippled grandmother ought to be able to do that without bouncing off. Lathrop! Unhook—-you're first."

     As the cadet came up, Hanako anchored himself to the ship with two short lines and took from his belt a very long line. He snapped one end to a hook in the front of the cadet's belt and the other to his own suit. The student looked at it with distaste. "Is the sky hook necessary?"
     Sergeant Hanako stared at him. "Sorry, Commodore—regulations. And shut up. Take the ready position."
     Silently the cadet crouched, then he was moving away, a fiery brush growing out of his back. He moved fairly straight at first, then started to turn.
     He pulled in a leg—and turned completely over.
     "Lathrop—cut off your jet!" snapped Hanako. The flame died out, but the figure in the suit continued to turn and to recede. Hanako paid out his safety line. "Got a big fish here, boys," he said cheerfully. "What do you think he'll weigh?" He tugged on the line, which caused Lathrop to spin the other way, as the line had wound itself around him. When the line was free he hauled the cadet in.
     Lathrop clicked on. "You were right, sergeant. I want to try it again—your way."
     "Sorry. The book says a hundred per cent reserve fuel for this drill; you'd have to recharge." Hanako hesitated. "Sign up for tomorrow morning—I'll take you as an extra."
     "Oh—thanks, Sarge!"
     "Don't mention it. Number one!"

From SPACE CADET by Robert Heinlein (1948)
SPACE 1999 NUM 6

(Click for larger images)

     Koenig's space suit protects him from the worst of the terrible heat and radiation. But the shock of the blast is another matter… Unable to brace himself, Koenig is hurled with stunning force against a bulkhead…

     Not enough to render him fully unconscious, the blow nevertheless leaves him too dazed to properly react to the situation… He has barely the wits about him to grab at a door-frame as the explosive decompression sucks every loose object into the void…

     But, his gloves were not designed for such a grip… The hurricane winds continue to push relentlessly against him…

     Until…His grip fails…

     And John Koenig, Commander of Moonbase Alpha, upon whose survival must ultimately depend the lives of 300 men and women… Is hurled into the airless maw of space…
     There is no sound in space — no scents. Only the numbing cold of the emptiness between the stars…

     At least, this close to a star, Koenig has the small relief of knowing there is enough heat to keep the moisture on his eye from freezing…

     He will not be blind for the rest of his life…

     Although that is a span which can now be meaured in seconds…

     9: A helmet!
     By coincidence, Koenig's own, though any helmet would do—
     If he can reach it, that is…
     And he has already wasted six precious seconds… (Actually time to unconsciousness is more like 10 seconds, not 15. But close enough.)

     8: Falling through space at 100 thousand miles an hour: a dying man, and a slim hope of survival—
     But the force of his expulsion has set Koenig tumbling…

     7: He twists, trying to angle himself for a desperate ploy…
     Knowing that too great a twist will only set him spinning…

     6: Eyes locked on the helment, Koenig finds the control circuit on his wrist by touch…
     Already his fingers are growing numb, his lungs aching…

     5: Now!
     Koenig opens the valve on his left-hand air tank…
     Precious oxygen spews into the void… But Newton's law holds true: "For every action, there is an equal and opposite reaction…"

     4: Koenig moves!
     Slowly…painfully slowly…but he moves!!
     But his improvised thruster is off-center… He begins to twist away from his target…

     3: Joints pop as Koenig strains towards the helmet…
     He will have only one chance…

     2: Got it!
     His skin is drumhead taut…
     Already his extermities are turning purple…

     1: Stay calm!
     Helmet in place…

     0: Connect hose…

From SPACE 1999 No 6 by Nicola Cuti, artwork by John Byrne (1976)

Jim's job turned out to be running a small welder that operated on compressed oxygen and acetylene. "Youll be working on some tricky alloys," Bart told him. "Keep the oxygen supply a little under what you need for the best burning. And before you turn it on, get a good grip. It's a small rocket, and don't forget that!"

They filed out. Some of the men seemed to be fully at home already, and simply dived off into space, kicking themselves toward the work. They carried tiny rocket tubes which could be used to kick themselves back in case they misjudged, but it wasn't something Jim cared to try yet. He was glad to see that others pulled themselves along the girders hand over hand.

Everything seemed to be done by hand power. Men were moving out to the piles of material scattered about, sorting them, and attaching cords before pulling them back by hand. There was no weight, but the inertia of the objects sometimes required the power of several men to overcome it. Once in motion, anything tended to keep that motion, and jockeying the parts into place and holding them there was a tricky business.

The welding proceeded well enough, however. Out here without air, the metals could never tarnish. They were given a brightening before being assembled to remove any corrosion from Earth's atmosphere, and then remained bright until they would be welded. Even aluminum and the titanium alloys were manageable.

Bart came over after a few minutes and inspected his work. "Good enough. But don't sit facing the same way so long. That Sun's hotter than you think. Sit too long in one direction and you'll heat one side of your suit near melting, while the other side freezes stiff. How do you feel?"

Jim had almost stopped thinking about that, under the pressure of the work. A boy who'd collapsed on the previous shift had put the welding behind the assembly, and Jim was driving himself to catch up. Bart clapped him on the shoulder and started to move on. Then he swung back.

"Jim, don't ever let me find you with your belt unfastened on the job again!" He snapped the silicone-plastic strap around the girder and to a hook in the suit. "I told you that torch was a small rocket! Let go, and you'll sail out like a bird if you're not strapped down."

"I guess I forgot this time," Jim admitted. "Sorry, Bart!"

The welding went on for several hours, until he finished what was ready. Part of the time, he'd been within reach by radio of one of the young college boys, and had struck up a conversation, forcing himself to stop being a lone wolf. He'd found that there was a sound reason for using the oxyacetylene welder instead of an electric rig. The compressed gases were lighter than batteries, and the station was still underpowered. They'd put up a sun mirror out of sheets of station walls and had used sections of pipe to make a boiler where the heat converged. It was driving a small steam plant and generator, but there were only about ten kilowatts to power the whole station until they could get the main power plant going much later.

The work went on more easily in the following days. New men came up from Earth, and most of them went back. One of them did almost the same thing Jim had done, but turned his rocket tube on while it was still pointing toward his helmet. Nobody got much work done that day, and there was no conversation at dinner.

From STEP TO THE STARS by Lester Del Rey. 1954


Many early designs of spacesuits for use in free fall were lacking legs. This simplifies the design. This gradually becomes a hard suit which allows an astronaut to work in a pressurized environment and so avoid the bends.

The Haunted Space Suit

At this point, perhaps I should remind you that the suits we use on the station are completely different from the flexible affairs men wear when they want to walk around on the Moon. Ours are really baby space ships, just big enough to hold one man. They are stubby cylinders, about seven feet long, fitted with low-powered propulsion jets, and have a pair of accordion-like sleeves at the upper end for the operator's arms.

As soon as I'd settled down inside my very exclusive space craft, I switched on power and checked the gauges on the tiny instrument panel. All my needles were well in the safety zone, so I gave Tommy a wink for luck, lowered the transparent hemisphere over my head and sealed myself in. For a short trip like this, I did not bother to check the suit's internal lockers, which were used to carry food and special equipment for extended missions.

As the conveyor belt decanted me into the air lock, I felt like an Indian papoose being carried along on its mother's back. Then the pumps brought the pressure down to zero, the outer door opened, and the last traces of air swept me out into the stars, turning very slowly head over heels.

The station was only a dozen feet away, yet I was now an independent planet—a little world of my own. I was sealed up in a tiny, mobile cylinder, with a superb view of the entire universe, but I had practically no freedom of movement inside the suit. The padded seat and safety belts prevented me from turning around, though I could reach all the controls and lockers with my hands or feet.

In space the great enemy is the Sun, which can blast you to blindness in seconds. Very cautiously, I opened up the dark filters on the "night" side of my suit, and turned my head to look out at the stars. At the same time I switched the helmet's external sunshade to automatic, so that whichever way the suit gyrated my eyes would be shielded.

Presently, I found my target—a bright fleck of silver whose metallic glint distinguished it clearly from the surrounding stars. I stamped on the jet control pedal and felt the mild surge of acceleration as the low-powered rockets set me moving away from the station. After ten seconds of steady thrust, I cut off the drive. It would take me five minutes to coast the rest of the way, and not much longer to return with my salvage.

From Who's There? aka The Haunted Space Suit by Sir Arthur C. Clarke (1958)
The Sands of Mars

All his life Gibson had been fascinated by gadgets, and the spacesuit was yet another to add to the collection of mechanisms he had investigated and mastered. Bradley had been detailed to make sure that he understood the drill correctly, to take him out into space, and to see that he didn’t get lost.

Gibson had forgotten that the suits on the Ares had no legs, and that one simply sat inside them. That was sensible enough, since they were built for use under zero gravity, and not for walking on airless planets. The absence of flexible leg-joints greatly simplified the designs of the suits, which were nothing more than perspex-topped cylinders sprouting articulated arms at their upper ends.

Along the sides were mysterious flutings and bulges concerned with the air conditioning, radio, heat regulators, and the low-powered propulsion system. There was considerable freedom of movement inside them: one could withdraw one’s arms to get at the internal controls, and even take a meal without too many acrobatics.

Bradley had spent almost an hour in the airlock, making certain that Gibson understood all the main controls and catechising him on their operation. Gibson appreciated his thoroughness, but began to get a little impatient when the lesson showed no sign of ending. He eventually mutinied when Bradley started to explain the suit’s primitive sanitary arrangements. “Hang it all!” he protested, “we aren’t going to be outside that long!”

Bradley grinned. “You’d be surprised,” he said darkly, “just how many people make that mistake.”

He opened a compartment in the airlock wall and took out two spools of line, for all the world like fishermen’s reels. They locked firmly into mountings on the suits so that they could not be accidentally dislodged.

“Number One safety precaution,” he said. “Always have a lifeline anchoring you to the ship. Rules are made to be broken— — but not this one. To make doubly sure, I’ll tie your suit to mine with another ten metres of cord. Now we’re ready to ascend the Matterhorn.”

The outer door slid aside. Gibson felt the last trace of air tugging at him as it escaped. The feeble impulse set him moving towards the exit, and he drifted slowly out into the stars.

The friction of the reel had checked his momentum when the cord attaching him to Bradley gave a jerk. He had almost forgotten his companion, who was now blasting away from the ship with the little gas jets at the base of his suit, towing Gibson behind him.

Gibson was quite startled when the other’s voice, echoing metallically from the speaker in his suit, shattered the silence.

“Don’t use your jets unless I tell you. We don’t want to build up too much speed, and we must be careful not to get our lines tangled.”

“All right,” said Gibson, vaguely annoyed at the intrusion into his privacy. He looked back at the ship. It was already several hundred metres away, and shrinking rapidly.

“How much line have we got?” he asked anxiously. There was no reply, and he had a moment of mild panic before remembering to press the “TRANSMIT” switch.

“About a kilometre,” Bradley answered when he repeated the question. “That’s enough to make one feel nice and lonely.”

“Suppose it broke?” asked Gibson, only half joking.

“It won’t. It could support your full weight, back on Earth. Even if it did, we could get back perfectly easily with our jets.”

“And if they ran out?”

“This is a very cheerful conversation. I can’t imagine that happening except through gross carelessness or about three simultaneous mechanical failures. Remember, there’s a spare propulsion unit for just such emergencies— — and you’ve got warning indicators in the suit which let you know well before the main tank’s empty.”

“But just supposing,” insisted Gibson.

“In that case the only thing to do would be to switch on the suit’s S.O.S. beacon and wait until someone came out to haul you back. I doubt if they’d hurry, in such circumstances. Anyone who got himself in a mess like that wouldn’t receive much sympathy.”

From The Sands of Mars by Sir Arthur C. Clarke (1951)

Space Taxi

A space taxi is a short ranged orbit to orbit vehicle used to carry astronauts and small amounts of cargo. At its simplest, it is a frame that astronauts attach themselves to, with a rocket engine at one end. More complicated taxis have an enclosed hull which may or may not be pressurized. Do keep in mind that the direction of "down" will appear to be in the same direction the rocket exhaust shoots.

Orion Space Taxi
Specific Impulse450 s
Exhaust Velocity4,500 m/s
Wet Mass1,584 kg
Dry Mass759 kg
Mass Ratio2.0
ΔV3,120 m/s
Payload136 kg (2 people)
Length3 m
Diameter1 m wide
General Dynamics 2-Man Space Taxi
Specific Impulse450 s
Exhaust Velocity4,500 m/s
Wet Mass361 kg
Dry Mass155 kg
Propellant Mass206 kg
Mass Ratio2.3
ΔV3,750 m/s
Height3.5 m

In this document about Orion drive spacecraft, they mention a space taxi. It carries two crew members, has a hardware mass of 623 kilograms, and a propellant mass of 825 kilograms. As near as I can measure from the diagram, it can be approximated as a cylinder with a height of two meters and a radius of 0.5 meters, with a hemisphere of radius 0.5 meters on each end.

This gives it an internal volume of 2 m3. Assuming it has chemical propulsion, the propellant would take up about 0.8 cubic meters, and the two crew would take up 0.14 cubic meters. Carrying two crew, it would have a mass ratio of about 2, and thus a deltaV of about 3,120 m/s.

In Volume 10: "Space Age in Fiscal Year 2001". Proceedings of the Fourth AAS Goddard Memorial Symposium, 15-16 March 1966, Washinton DC Krafft Ehricke has a diagram featuring what appears to be the same space taxi.

General Dynamics had designs for one and two-man space taxis that again appear to be the same ones. The two man version was described to have a dry mass of 155 kg and 206 kg of propellant (probably space storage hpergolic propellants). This would give it a mass ratio of 2.3 and thus a deltaVof about 3,750 m/s. For more details refer to US Spacecraft Projects #01 by Scott Lowther.


candle (n.): A candle, or putt-putt, is the simplest transport spacecraft that can be devised, consisting essentially of a tank of hypergolic rocket fuel powering a thrust motor and a simple reaction-control frame. The pilot, supported by their vacuum suit, rides the candle — the tank itself — in much the same manner as a velocipede.

The additional accoutrements and controls of a candle vary widely by type. Most common are stabilization gyros, to make their handling less temperamental in the face of mass shifts. Commercial models often include a range of accessories: fly-by-wire navigation, Orbital Positioning Systems (space version of GPS), a comfortable saddle and space for passengers, cargo panniers, canned life support reserves, and so forth.

But the virtue of a candle is its simplicity. One can be put together out of parts readily obtainable from even a half-stocked chandler, or for that matter from those lying around any wreckyard, or even crash site. Such a scrap-candle may consist of little more than the tank and motors, with handhold bars and lash-downs for bagged cargo welded on where they might be useful. Some go so far as to strip the navigation system down to a row of firing switches for each motor, requiring the pilot to figure burn times and vectors by eye, or at least by pocket-contents.

Indeed, in many spacer cultures across the Worlds, building one’s first candle from parts, salvaged, scrounged, and where necessary even purchased, is considered a rite of passage for the young. More cynical observers consider the true rite of passage being making one’s first candle flight without having to be ignominiously hauled home by the Orbit Guard.

- A Star Traveller’s Dictionary


(Alistair Young commissioned William Black to do the artist conception of Isif's Candle:

If you ask any spacer what a candle is, they'll tell you it's the simplest spacecraft imaginable, just the thing you need for commuting between nearby habs or spacecraft, playing tourist in the belt, or popping Outside for a quick satellite-servicing run. If you want more than that, there's always the entry in the Star Traveller's Dictionary.

So what Isif Alclair has built from the wreckage of her starship isn't technically what people most spacers would think of as a candle. lt's got an oversized nuclear thermal drive, for one thing, and much too much reaction mass for anything that would usually be attempted on a candle, and other distortions of the standard rigging. But then, it's also got a lot further to go if she wants to see home again.

And anyway, if it works out, no-one's going to quibble with her over nomenclature.)

(ed note: the protagonist is the sole survivor of a spacecraft disaster. They are cobbling together a candle (space taxi) out of usable parts salvaged from the wreck, hoping to fly to a place they can be rescued.)

But it’s true. Sleep well.

Puppet ackles activated. Primary personality execution SUSPENDED.

Warning: Medical alerts require review.
Warning: Life support status requires review.
Warning: Capability plat requires review.

Well, this hurts exactly as much as I remember.

So, let’s review what we have to work with, eigensister-mine (her eigensister is an electronic duplicate of her personality living in the candle's computer). We have most of a candle assembled, main frame, remass tank, a truss up front with navigational controls. I look upon our work and declare it good, partly because I can’t find anything wrong with it, and partly because if there’s anything more subtle wrong with it at this point, there’s nothing I can do about it anyway.

Because I have seven hours of native life-support left in this suit, and that is not even enough time to do the absolutely necessary, unless I want to try working on a pure-LOX tether. Which I really don’t, especially doing engineering work. So it’s going to be chemical overdrive, a wing, and a prayer. Afraid I’m going to have strained a few more tissues by the time I give you back to you.

Rough schedule:

Four hours: rip off the stubs of the old thrust-frame, and assemble a proper truss from structural members I have lying around here to bolt the drives to. I may have enough time to check balance on it; if not, attaching it anyway and counting on the gyros. Make sure I leave enough room in the center to clamp the cutter’s vector control core if I find it; at least it’s modular. Make sure there’s spare cabling back here for it.

One and a half hours: pull an accumulator stack from the battery room up above and maneuver it down here, then mount it above the forward truss. Hook it up to all the power inputs of things. If running ahead of schedule, consider circuit breakers.

Half an hour: Clamp the substrate/FDR box and my scavenged wireless node onto the forward truss. Power them up, run self-test, and while you’re doing that, rig some sort of clamp up there for my scavenged LOX tank.

Then migrate myself onto them, because my primary isn’t going to be able to fly this thing, however much she hopes to.

Last hour: Final steps. Acceleration couch from the cutter – nice as it would be to have the big seat with the hand controls, there’s no time to do a clean disconnect. Yank one of the non-pilot ones, and mount it on the front of the forward truss. Put one of the spare PLSS packs in its mounting, and run the LOX line into that; we’ll have to use its electrical heater rather than running a long line, but we’ve got power to spare if we give it an aux feed off the accumulator.

Using a spare pack means breathing shallow while changing the pack out, but it’s easier than wiring behind my back.

That leaves… no time. So no test, check-out, or proving. Well, okay.

It also leaves no time to do the software hacks necessary to integrate all this stuff, so I’m going to have to fork another me (duplicate yourself as an electronic person inside the candle's computers) to do that while I do the physical work. And since the processors on the candle are going to be pushing it to support one me, it looks like part of us doesn’t get to be rescued. Damn.

(ed note: To read the story from the beginnng, go here, scroll to the very bottom, and read the posts from the bottom to the top in chronological order)


Matt pulled himself along, last in line, and found the scooter loaded. He could not find a place; the passenger racks were filled with space-suited cadets, busy strapping down.

The cadet pilot beckoned to him. Matt picked his way forward and touched helmets. "Mister," said the oldster, "can you read instruments?"

Guessing that he referred only to the simple instrument panel of a scooter, Matt answered, "Yes, sir."

"Then get in the co-pilot's chair. What's your mass?"

"Two eighty-seven, sir," Matt answered, giving the combined mass, in pounds, of himself and his suit with all its equipment. Matt strapped down, then looked around, trying to locate Tex and Oscar. He was feeling very important, even though a scooter requires a co-pilot about as much as a hog needs a spare tail.

The oldster entered Mart's mass on his center-of-gravity and moment-of-inertia chart, stared at it thoughtfully and said to Matt, "Tell Gee-three to swap places with Bee-two."

Matt switched on his walky-talky and gave the order. There was a scramble while a heavy-set youngster changed seats with a smaller cadet. The pilot gave a high sign to the cadet manning the hangar pocket; the scooter and its launching cradle swung out of the pocket, pushed by power-driven lazy tongs.

A scooter is a passenger rocket reduced to its simplest terms and has been described as a hat rack with an outboard motor. It operates only in empty space and does not have to be streamlined.

The rocket motor is unenclosed. Around it is a tier of light metal supports, the passenger rack. There is no "ship" in the sense of a hull, airtight compartments, etc. The passengers just belt themselves to the rack and let the rocket motor scoot them along.

From SPACE CADET by Robert Heinlein. 1948

The taxi looked like a huge, short salami, twenty feet long and eight in diameter. There was a small dome for the pilot to see out, and an air lock at the front, while the rear carried a small rocket motor. They went through the lock. Inside were two seats, fuel tanks, and steering assembly, as well as cargo space.

Jerry blasted off, after cranking a hand gyroscope to turn them. It was a weak, cautious blast that used little fuel. "Better to take your time and not waste fuel," he explained. "Once you get moving, there's nothing to stop you."

They drifted toward the rocket, turning over by the use of the gyroscope, and Jerry brought them to a stop with a single quick blast of the rocket tube. It was precise, beautiful work. They coasted a few feet away, while he turned them over again until the nose pointed to the rocket's lock, which was open.

"Slip your helmet back on, Jim," Jerry ordered. "Go out into the lock and catch that rope."

The man in the ship ahead had already thrown the cord. Jim found the end and fastened it to a bite inside the lock. The taxi was pulled up to the main lock, where it fitted snugly against the silicone-rubber gasket to make an airtight seal.

They took the passengers back, and then began making trips to ferry the supplies. These were dumped out of the big rocket by the pilot and his men. Apparently they put on space suits, evacuated the air from the cargo section and lock, and simply pitched the crates and pieces into space. It was Jim's job to go out of the taxi and secure these with cords to a ring on the back of the taxi, leaving enough distance so the rocket blast wouldn't hurt them.

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

     Captain Stone sighed. "I'm going with you. Will your scooter take three?"
     "Sure, sure! It's got Reynolds saddles; set any balance you need."

     Hazel allotted one-fourth her fuel as safety margin, allotted the working balance for maximum accelerations, figuring the projected mass-ratios in her head.

     Hazel worked the new mass figures over; with Edith, her suit, and the spare bottle subtracted she had spare fuel.
     She lined up on City Hall by flywheel and stereo, spun on that axis to get the sun out of her eyes, clutched her gyros, and gave it the gun. The next thing she knew she was tumbling like a liner in free fall. She remembered from long habit to cut the throttle but only after a period of aimless acceleration, for she had been chucked around in her saddle, thrown against her belts, and could not at first find the throttle.

     Quickly she checked things over. There was not much that could go wrong with the little craft, it being only a rocket motor, an open rack with saddles and safety harness, and a minimum of instruments and controls. It was the gyros, of course; the motor had been sweet and hot. They were hunting the least bit, she found, that being the only evidence that they had just tumbled violently. Delicately she adjusted them by hand, putting her helmet against the case so that she could hear what she was doing.
     Only then did she try to find where they were and where they were going. Let's see—the Sun is over there—and that's Betelgeuse over yonder—so City Hall must be out that way. She ducked her helmet into the hemispherical "eye shade" of the stereo. Yup! there she be!
     The Eakers place was the obvious close-by point on which to measure her vector. She looked around for it, was startled to discover how far away it was. They must have coasted quite a distance while she was fiddling with the gyros. She measured the vector in amount and direction, then whistled. There were, she thought, few grocery shops out that way—darn few neighbors of any sort.
     But she kept trying to call Mrs. Eakers, or anyone else in range of her suit radio while she again lined up the ship for City, with offset to compensate for the new vector. She was cautious and most alert this time—in consequence she wasted only a few seconds of fuel when the gyros again tumbled.
     She unclutched the gyros and put them out of her mind, then took careful measure of the situation. The Eakers dump was now a planetary light in the sky, shrinking almost noticeably, but it was still the proper local reference point. She did not like the vector she got. As always, they seemed to be standing still in the exact center of a starry globe—but her instruments showed them speeding for empty space, headed clear outside the node.

     Carefully she lined up the craft by flywheel; carefully she checked it when it tried to swing past. She aimed both to offset the new and disastrous vector and to create a vector for City Hall. She intentionally left the gyros unclutched. Then she restrapped Lowell in his saddle, checked its position. "Hold still," she warned. "Move your little finger and Grandma will scalp you."
     Just as carefully she positioned herself, considering lever arms, masses, and angular moments in her head. Without gyros the craft must be balanced just so. "Now," she said to herself, "Hazel, we find out whether you are a pilot—or just a Sunday pilot." She ducked her helmet into the eyeshade, picked a distant blip on which to center her crosshairs, and gunned the craft.
     The blip wavered; she tried to rebalance by shifting her body. When the blip suddenly slipped off to one side she cut the throttle quickly. Again she checked her vector. Their situation was somewhat improved. Again she called for help, not stopping to cut the child out of hearing. He said nothing and looked grave.
     She went through the same routine, cutting power again when the craft "fell off its tail." She measured the vector, called for help—and did it all again. A dozen times she tried it. On the last try the thrust stopped with the throttle still wide open.
     With all fuel gone there was no need to be in a hurry. She measured her vector most carefully on the Eakers' ship, now far away, then checked the results against the City Hall blip, all the while calling for help. She ran through the figures again; in a fashion she had been successful. They were now unquestionably headed for City Hall, could not miss it by more than a few miles at most—almost jumping distance. But, while the vector was correct in direction, it was annoyingly small in quantity—six hundred and fifty miles at about forty miles an hour; they would be closest in about sixteen hours.

     Roger Stone explained. The twins looked at each other. "Dad," Castor said painfully, "you mean Hazel took Mother out in our scooter?"
     "Certainly." The twins questioned each other wordlessly again. "Why shouldn't she? Speak up."
     "Well, you see . . . well, it was like this—"
     "Speak up!"
     "There was a bearing wobble, or something, in one of the gyros," Pollux admitted miserably. "We were working on it."
     "You were? In Charlie's place!"
     "Well, we went over there to see what he had in the way of spare parts and, well, we got detained, sort of."
     Their father looked at them for several seconds with no expression of any sort. He then said in a flat voice, "You left a piece of ship's equipment out of commission. You failed to log it. You failed to report it to the Captain." He paused. "Go to your room."
     "But Dad! We want to help!"
     "Stay in your room; you are under arrest."

     Castor thought about it. "That's bad. That could be really bad." He added suddenly, "But quit jittering, just the same. Start thinking instead. What happened? We've got to reconstruct it."
     "'What happened?' Are you kidding? Look, the pesky thing tumbles, then anything can happen. No control."
     "Use your head, I said. What would Hazel do in this situation?"
     They both kept quiet for some moments, then Pollux said, "Cas, that derned thing always tumbled to the left, didn't it? Always."
     "What good does that do us? Left can be any direction."
     "No! You asked what Hazel would do. She'd be along her homing line, of course—and Hazel always oriented around her drive line so as to get the Sun on the back of her neck, if possible. Her eyes aren't too good."
     Castor screwed up his face, trying to visualize it. "Say Eakers' is off that way and City Hall over here; if the Sun is over on this side, then, when it tumbles, she'd vector off that way." He acted it with his hands.
     "Sure, sure! When you put in the right coordinates, that is. But what else would she do? What would you do? You'd vector back—I mean vector home."
     "Huh? How could she? With no gyros?"
     "Think about it. Would you quit? Hazel is a pilot. She'd ride that thing like a broomstick." He shaped the air with his hands. "So she'd be coming back, or trying to, along here—and everybody will be looking for her 'way over here."
     Castor scowled. "Could be."
     "It had better be. They'll be looking for her in a cone with its vertex at Eakers'—and they ought to be looking in a cone with its vertex right here, and along one side of it at that."

     When Charlie had dug his scooter out of the floating junkyard moored to his home they soon saw why he had refused to lend it. It seemed probable that no one else could possibly pilot it. Not only was it of vintage type, repaired with parts from many other sorts, but also the controls were arranged for a man with four hands. Charlie had been in free fall so long that he used his feet almost as readily for grasping and handling as does an ape; his space suit had had the feet thereof modified so that he could grasp things between the big toe and the second, as with Japanese stockings.

     The crate was old but Charlie had exceptionally large tanks on it; it could maintain a thrust for plenty of change-of-motion. Its jet felt as sweet as any. But it had no radar of any sort. "Charlie, how do you tell where you are in this thing?"
     "That" proved to be an antiquated radio compass loop. The twins had never seen one, knew how it worked only by theory. They were radar pilots, not used to conning by the seats of their suits. Seeing their faces Charlie added, "Shucks, if you've got any eye for angle, you don't need fancy gear. Anywhere within twenty miles of the City Hall, I don't even turn on my suit jet—I just jump."
     They cruised out the line that the twins had picked. Once in free fall Charlie taught them how to handle the compass loop. "Just plug it into your suit in place of your regular receiver. If you pick up a signal, swing the loop until it's least loud. That's the direction of the signal—an arrow right through the middle of the loop."
     "But which way? The loop faces both ways."
     "You have to know that. Or guess wrong and go back and try again."

     Charlie, anticipating what would be needed, had swung ship as soon as he had quit accelerating. Now he blasted back as much as he had accelerated, bringing them dead in space relative to City Hall and the node. He gave it a gentle extra bump to send them cruising slowly back the way they had come. Pollux listened, slowly swinging his loop. Castor strained his eyes, trying to see something, anything, other than the cold stars.
     "Got it again!" Pollux pounded his brother.
     Old Charlie killed their relative motion; waited. Pollux cautiously tried for a minimum, then swung the loop, and tried again. He pointed, indicating that it had to be one of two directions, a hundred and eighty degrees apart.
     "Which way?" Castor asked Charlie.
     "Over that way."
     "I can't see anything."
     "Me neither. I got a hunch."
     Castor did not argue. Either direction was equally likely. Charlie gunned it hard in the direction he had picked, roughly toward Vega. He had hardly cut the gun and let it coast in free fall when Pollux was nodding vigorously. They coasted for some minutes, with Pollux reporting the signal stronger and the minimum sharper . . . but still nothing in sight. Castor longed for radar. By now he could hear crying in his own phones. It could be Buster—it must be Buster.
     "There she is!"
     It was Charlie's shout. Castor could not see anything, even though old Charlie pointed it out to him. At last he got it—a point of light, buried in stars. Pollux unplugged from the compass when it was clear that what they saw was a mass, not a star, and in the proper direction. Old Charlie handled his craft as casually as a bicycle, bringing them up to it fast and killing his headway so that they were dead with it. He insisted on making the jump himself.

From THE ROLLING STONES by Robert Heinlein (1952)

(ed note: Cot-Vee = Cargo Orbital Transfer Vehicle {COTV}, Pot-Vee = Personnel Orbital Transfer Vehicle {POTV}, Eff-Mu = Extra Facility Maneuvering Unit {EFMU})

     There were few amenities on the Pot-Vee Edison. But since the transition to GEO Base took several hours, the craft did have a bathroom of sorts—nothing more than a simple adaptation of the proven technology of the SkyLab "waste management system," as the old NASA circumlocution labeled it. The Personnel Orbital Transfer Vehicle itself was just a double-decked cylindrical cabin section eighteen feet in diameter and fifty-five feet long with a control compartment, docking air lock, and tunnel forward. On its aft end was the cylindrical hydrogen-oxygen propulsion module, the common orbital propulsion module used for both Pot-Vees and Cot-Vees.

     "Easy flight today," Jackson remarked. "Three hours, fourteen minutes dock to dock. Relax and enjoy." (ed note: transit from LEO to GEO)
     "Pretty short time for such a high lift, isn't it?" Stan Meredith asked. "Planning on high boost?"
     "Naw! This flying sewer pipe is boost-limited to point-one-five gees because of its structure," Jackson explained. "Besides, we don't need the boost that's required for Earth-to-orbit. You'll hardly notice it now—but, man, it'll feel like a rock dropped on you after you've spent six weeks in weightlessness!"
     The Ancient Astronaut was right. There were some bangs, clanks, muffled clunks, and gentle jolts as the Edison undocked from LEO Base. And when the thrust of the oxygen-hydrogen rocket engines came on, there was the gentlest of accelerations, accompanied by a slight vibration and a damped shaking.
     "Combustion noise being transmitted through the thrust structure, plus a little bit of damped pogo oscillation," Fred Fitzsimmons explained.
     "Why didn't they get the pogo out of these ships before they put them into operation?" Dave Cabot asked. "Didn't pogo oscillations give the engineers all sorts of trouble on Saturn and the Space Shuttles?"
     Fred smiled. "Welcome to private-enterprise astronautics! There's worse vibrations in an airplane. It costs so much to get all pogo oscillations out of a design under all sorts of load conditions—and these Pot-Vees operate with all kinds of loads—that it's more cost-effective to let them shake . . . within reasonable limits, of course."
     "But won't this thing eventually shake apart?" A note of anxiety entered Dave's voice.
     "Nope," Fred replied. "Never had a Pot-Vee crumple yet. The engines are de-rated so much that the pogo doesn't affect them, and the engines themselves are modernized versions of very old, well-proven designs that never gave a bit of trouble."
     "RL-10s," Stan put in.
     There were no cabin windows in the Pot-Vee, so it was a three-hour flight without a view.

     Stan and Fred discovered that it took almost nineteen minutes just to get to Charlie Victor, Mod Four Seven. There were a lot of hatches to go through and a lot of modules to traverse. "Fred, if we don't find some faster way to move around this rabbit warren, a lot of people are going to be dead before we reach them," Stan pointed out, finally opening the hatch to Mod Four Seven.
     Fred was right behind him through the hatch. "I'll ask Doc to see Pratt about getting us an Eff-Mu."
     "What's that?"
     "Extra Facility Maneuvering Unit. A scooter to anybody but these acronym-happy engineers."

     "You want an Eff-Mu so you can get around GEO Base faster."
     "Right. We lost the hyperpyrexia case because we couldn't get there fast enough. It takes forever to go through all the hatches and corridors of GEO Base."
     "Stan, I agree on both counts," Tom replied. "You need an Eff-Mu, and all of us need to be able to get around GEO Base faster in emergencies. But do you think a standard two-man Eff-Mu will really do the job?"
     "Why not?"
     "Why don't Earth-bound paramedics use motorcycles?"
     "I see what you mean. We need room for the patient."
     "Roger. Eventually maybe not, but right now we've got to provide that, too. Is there any Eff-Mu type that'll handle the two of you plus a patient?"

Pratt called him. "Doc, your special ambulance is coming up in the next Cot-Vee supply ship. Should be docking in six hours at Portlock Foxtrot. We're also putting a docking collar module on the free end of your med module, so don't be disturbed when you hear noises. You'll be able to dock right to your sick bay."

(ed note: one hex module is a hexagonal prism, about 3.7 meters wall to wall (12 feet), 15.2 meters long (50 feet), and has a volume of 241 cubic meters (8,500 cubic feet)

     The Pumpkin turned out to be a masterpiece of quick-and-dirty engineering. It was half a hex module outfitted with a StarPacket vernier engine as its main propulsion system and a series of electric thrusters for maneuvering. It had no direct view to the outside universe, only an array of video displays—large windows in space were a constant trouble source because the state of the art couldn't keep them from leaking, and the Pumpkin's life-support consumables were limited to twenty-four man-hours with no recycling. The unit sported a universal docking collar on the end of the hex module opposite the StarPacket vernier engine.
     Tom went with Fred and Stan to take delivery of their new gadget and bring it around to the med module dock. Pratt's men had latched the half hex of a docking port and pressure lock to the med module a few hours earlier in an operation that took only twenty minutes. GEO Base had been designed like an Erector set with plug-in modules; there was no time to build pretty or permanent space facilities on this job.

     He looked over the panel. "Attitude indicator. Four relative velocity indicators linked to eight search radars and three lidars at will. Beacon transponders. You know, this really isn't that much different from flying airplanes on instruments."
     And it wasn't. They returned for their P-suits, loaded another twenty-four man-hours of oxygen aboard, then checked out the Pumpkin—propellant load, battery-charge level, life-support-system consumables level, and the rest of a three-page checklist that someone had managed to put together for the Pumpkin when it was assembled at LEO Base. The controls had been highly simplified and were like those of a helicopter, with two sidearm controllers and two foot pedals to provide control in roll, pitch, yaw, and translation in six degrees of freedom. The StarPacket vernier engine offered enough thrust to get the Pumpkin moving for fast sprints, while the electric thrusters—the same kind used to propel the SPS array modules from LEO Base—permitted the gentlest of velocity changes.

     The Pumpkin's saved a couple of people already. Three of us have learned how to operate it: Stan, Fred, and myself. Now I understand why space pilots are people who are instrument-rated airplane pilots and also own their own boats. "Flying" the Pumpkin is like flying an airplane by instruments; you must believe what those gauges are telling you, and you can't pay any attention to the inputs from your vestibular apparatus or from kinesthetic senses. Docking and undocking the Pumpkin is like bringing the S.S. Patrick Miller alongside and gently docking to a pier; the Pumpkin has far less momentum, however, and is probably more like docking a row boat. There isn't anything difficult about it provided you aren't in a hurry.
     That's going to be the biggest problem with the Pumpkin. When Fred and Stan are on a call, they're in a hurry. I expect to get reports of hard docks. I hope they don't crumple too much stuff until they learn how to handle the Pumpkin under the stress of an emergency. I'm not too worried about them crumpling the Pumpkin; all the stress is column loading on that hex module, and it'd take a big bump to make the structure fail in that mode.

     Together, they went through the power-up checklist. Total time, forty-two seconds. Less than three minutes after the call, Fred retracted the docking latches and backed the Pumpkin away from the med module on thruster power. While Fred was doing that, Tom interfaced the ship's computer with the one in GEO Base via radio link; he called up a three-dimensional display of the current GEO Base configuration and had the computer call out the location of the accident site.
     "Computer has fed course parameters to the guidance system," Tom reported. Fred slued the ship and coupled the autopilot.
     "Roger! Autopilot locked on. Stand by for thrust."
     Tom spoke over the radio. "Traffic, Pumpkin. Emergency. Departing med module under primary thrust for Array Subassembly Module One Zero Seven. Are we clear to boost?"
     Fred held his finger over the abort switch in anticipation of a possible Traffic delay. But it didn't come. "Pumpkin, Traffic. Clear to boost."
     The boost came with a little fishtailing. "Dammit!" Fred swore. "Doc, this autopilot doesn't warm up fast enough. We'll have to go manual follow-up."
     "I'll take it, Fred." Flying the Pumpkin wasn't as hard as flying a light airplane on instruments through an overcast at night. In this case, with the course already plotted by the computer, all Tom had to do was keep the marker bugs centered on the attitude-situation and relative-velocity displays. With the sidearm controller in one hand and the thruster and vernier throttles in the other, Tom didn't let the red Xs of the marker bugs deviate from the center of the display.
     They picked up the group of P-suited figures on video long before the computer called for retros. To keep the thruster and vernier discharges away from the P-suited workers, Tom slued the Pumpkin in yaw and applied retro thrust by vector.

     The paramedic didn't say anything, but reached over and activated Tom's P-suit backpack. Tom did the same for Fred. Only then did they disconnect from the Pumpkin's life-support system.
     "Dump pressure, Fred."
     Tom felt his suit pressurise as the atmosphere of the Pumpkin was dumped into space through spill valves that equalized the thrust produced. Normal procedure wouldn't have permitted dumping of pressure, nitrogen being the one gas that had to be brought up from Earth. In addition, the venting created a gas halo around the ship that might have permitted arcing of electrical equipment on the SPS array. But in an emergency where the Pumpkin had to be depressurized rapidly, there was no alternative.

From SPACE DOCTOR by Lee Correy (G. Harry Stine) 1981

(ed note: Keven, Glenda, and Jacob have been stranded on a tiny asteroid orbiting Ceres by the Bad Guys. They are in a mostly stripped base, trying to figure out how to get down to Ceres using only what is available)

     Kevin prowled through the corridors of their prison. There has to be some way, he told himself. Ceres mocked him from below, less than three hundred kilometers down. It hung huge in the night sky.
     Three hundred kilometers down, and we're moving about half a kilometer a second relative to Ceres, Kevin thought. That's not very much velocity. Under a thousand miles an hour. It doesn't take much energy to get to that speed. How much gasoline does it take to accelerate a car on Earth up to a hundred miles an hour—a gallon or so? We only need ten times that, not even that much.
     There's plenty of hydrogen and oxygen. Marvelous rocket fuels if we only had a rocket. More than enough to get us down, except that the temperature of hydrogen burning in oxygen is a lot hotter than anything we have to contain in it—
     No. That's not right. The fuel cells do it. But they do it by slowing down the reaction, and they can't be turned into rocket engines.
     He remembered the early German Rocket Society experiments described by Willy Ley. The Berliners had blown up more rockets than they flew, and they were only using gasoline, not hydrogen. Liquid-fuel rockets need big hairy pumps, and Kevin didn't have any pumps.
     What did he have? Fuel cells, plenty of them, and so what? An electric-powered rocket was theoretically possible, but Kevin didn't have the faintest idea of how to build one, even if there was enough equipment around to do it with. He wasn't sure anyone had ever built one—certainly he couldn't.
     Back to first principles, he thought. The only way to change velocity in space is with a rocket. What is a rocket? A machine for throwing mass overboard. The faster the mass thrown away goes in one direction, the faster the rocket will go in the other, and the less you have to throw. All rockets are no more than a means of spewing out mass in a narrow direction. A rocket could consist of a man sitting in a bucket and throwing rocks backward.
     That might get a few feet per second velocity change, but so what? There simply wasn't enough power in human muscles—even if he did have a lot of rocks. Was there any other way to throw them? Not fast; and unless the thrown-away mass had a high velocity, the rocket wouldn't be any use. He went on through the tunnels, looking at each piece of equipment he found, trying to think of how it might be used.
     You can throw anything overboard to make a rocket. Hydrogen, for example. That's all Wayfarer's engines did, heat up hydrogen and let it go out through the rocket nozzle. We have hydrogen under pressure— Not enough. Nowhere near enough hydrogen and nowhere near enough pressure, not to get velocity changes of hundreds of miles an hour. Ditto for oxygen. Gas under compression just can't furnish enough energy. What would? Chemical energy; burning hydrogen in oxygen would do it, but it gave off too much; there was nothing to contain that reaction except the fuel cells and they did it by slowing the reaction way down and—
     And I'm back where I started, Kevin thought. Plenty of energy in the fuel cells if I could find a way to use it. Could I heat a gas with electricity? Certainly, only how—
     His eye fell on the hot-water tank in the crew quarters. An electric hot-water tank. There was a pressure gauge: forty pounds per square inch. Forty p.s.i.—He looked at the tank as if seeing it for the first time, then went running back to the others.
     "Glenda, Jacob, I've got it."

     "Sure it works." Kevin grinned. "Steam at forty p.s.i. will come out fast. About a kilometer a second."
     "I believe you," Glenda said. "But it sounds silly. Steam rockets?"
     Kevin shrugged. "It is silly. There are a lot more efficient systems. But this will work—"
     "In a low g field," Jacob said. "You will not have much thrust. Of course you won't need much."
     "I'm sure it works," Kevin said. "Now all we have to do is build it." He made himself sound confident; he knew how much room for error there was in his figures. "Look, it takes nine hundred and eighty calories to turn a gram of water into steam. We heat that steam up another thirty or forty degrees and let it out. The energy is moving molecules. We know the molecular weight of water, so we can figure the number of molecules in a gram and—"

     They disconnected the hot-water tank and drilled holes in it. Several turns of heating wire went through the holes, then they sealed them in epoxy. At one end of the tank they drilled a large hole and threaded a pipe into it, threaded a large valve onto the pipe, and welded a makeshift rocket nozzle beyond that.
     When it was done they tethered the tank and filled it with water, then connected a fuel cell to the heating leads. "Here goes," Kevin said. He threw the switch to start the heaters.
     Slowly the water inside heated, then began to boil. The pressure shown on the gauge began to rise. In half an hour they had forty-five pounds of pressure. "All right, let's try it," Kevin said.
     Glenda turned the valve to let out steam. A jet of steam and water shot out across the surface of the moonlet. Ice crystals formed in space and slowly settled to the rocket surface. The jet reached far away from them, well off the moonlet itself. The tank pulled against its tether lines, stretching the rope.
     "It works!" Kevin shouted. "Damn it, we're going to make it!" He shut off the electricity. "Let's get her finished."

     It didn't look like a spaceship. It didn't even resemble a scooter, crude as those were. It looked like a hot-water tank with fuel cells bolted onto it. For controls it had vanes set crosswise in the exhaust stream, spring-loaded to center, with two tillers, one for each vane; a valve to control steam flow; and switches to connect the fuel cells to the heaters. Nothing else.
     The tank itself was fuzzy: They'd sprayed it with Styrofoam, building it up in layers until they had nearly a foot of insulation. There were straps on opposite sides of the tank to hold two passengers on.
     The tank held nearly a hundred gallons of water. Kevin calculated that they had more than enough energy to boil it all in their two fuel cells, and they would only need sixty gallons to get to Ceres. The number was so small that he ran it four times, but it was correct.
     The strangest part was the stability system: a pair of wheels taken from a mining cart and set up in front of the water tank. Electric motors rotated the wheels in opposite directions.

     The total mass of Galahad with full water tank was just under 550 kilograms.

     It took only a gentle effort to push the steam rocket away from the moonlet, but the cartwheel-gyros resisted any effort to turn it. Finally they got it oriented properly in space. Then they climbed aboard.
     "Full head of steam," Kevin said. "Almost fifty pounds. Ready?"
     He twisted the steam valve. At first both steam and water were expelled from the tank, but as they began to accelerate, the water settled and the exhaust valve let out only steam. C-2 dropped away. They missed it. It was a prison, but a safe one; now they had only their makeshift steam rocket.
     Galahad showed a tendency to tumble, but with the gyros resisting, they were able to control it with the steering vanes. A plume of steam shot from the tank, rapidly crystallizing into ice fog that engulfed them.
     "Damn. That's going to make it hard to see," Kevin said. "Nothing we can do about it." He peered down toward Ceres. It didn't seem any closer. Jacob's farewell faded in their headsets.
     Norsedal's calculations had shown that twenty minutes' thrust should be enough to cancel all their orbital velocity. It would use up just about half their fuel. Once Galahad was stopped dead in orbit above Ceres, they would fall toward the asteroid, and they would have half their steam left to counteract that.
     The trouble was that Jacob couldn't calculate how high above Ceres they would be when the twenty minutes were finished. As they lost velocity, they would lose altitude, and their orbit would no longer be a smooth circle, but an ellipse intersecting Ceres—somewhere. At the end of twenty minutes Kevin cut the power off. He was pleased that they still had thirty pounds of steam pressure.

     "Yes, but that's what the numbers say."
     "All right."
     And a year ago I was working equations in school, Kevin thought. Numbers to crunch and write down for examinations. Now they're something to stake your life on.

From EXILES TO GLORY by Jerry Pournelle (1977).

The long-distance shuttle, the Rather Not, had its permanent mooring in the hollow center of the Orb. A four-legged strutwork held it in place against the gentle centrifugal tug, so it remained fixed over a repair berth. Mara clipped onto a mooring line that ran out to the Rather Not and adroitly pushed off from the Orb’s inner wall. Tsubata watched her movement with a critical eye. After a moment of coasting she flexed and turned so that her feet pointed toward the shuttle. She squirted her jets and slowed perceptibly. As an extra fillip, she unclipped from the mooring lines a few meters away and landed catlike on the tail section.

“Good enough. Don‘t move till I get there,” Tsubata said over suit radio.

“Okay.” Mara watched him swim easily across the twenty meters between them. He probably wanted her to mess up the maneuver; it would be easy to document if he had a friend watching on 3-D and would make a good first entry in a file. She knew enough about organizations to guess that, if Tsubata wanted to get rid of her, he would have to build a thick folder of instances to prove incompetence.

As Tsubata moved toward her, Mara glanced around and attached her suit tie-line to the nearest pipe. Most shuttles she had seen were different, each thrown together from cannibalized spare parts that came to hand. The Rather Not had a few customized pieces and the magnetic shielding coils were considerably larger, but otherwise it was like the others—all bones and no skin. The pilot couch was located at dead center of gravity in the middle, surrounded by struts, tanks, pipes, hauling collars, and storage lockets, all placed to obscure as littie of the view as possible. A large ion engine was mounted behind the couch in gray housing. It was lumpy but balanced; it wouldn't go into spinover if a pilot made a wrong move.

As Tsubata touched down she glided away from him, perching on top of the pilot couch backrest.

“I told you not to move.” Tsubata came after her.

“You’re going to have to give me more latitude than that. I know you’re not exactly tingling with anticipation to see me out here, but that’s the way it’s got to be.”

Tsubata said nothing, waving a hand to dismiss the subject. “First, I’m going to make sure you know what every piece of equipment on this shuttle is for.”

Mara had expected to know most of it, but there was a bewildering maze of detail. There were systems for fuel feed, a pipe complex regulating attitude jets, three different super-conducting magnet configurations for screening against Van Allen belt particles, two overlapping electrical systems, navigation index, vector integrater, multiple communications rigs, an emergency high-gain antenna for work when the Orb and shuttle were not in line of sight, gyros, radio, hauling apparatus, repair parts, life support—all this had to be integrated so that a change in one system didn’t cause a malfunction in another. In the next three hours Mara gained considerable respect for Tsubata and his work. He made it clear to her that a shuttle could not be run by the book; like most human creations, it demanded intuition, craft, and a certain seat-of-the-pants shrewdness.

It wasn’t until two days later that Tsubata considered her competent enough to take the Rather Not out on a routine flight.

From IF THE STARS ARE GODS by Gregory Benford & Gordon Eklund (1977)

(ed note: Aeneas MacKenzie is being boosted into orbit by laser launcher.)

      Ten gravities for ninety seconds is easily within the tolerance of a healthy man; but Aeneas had no wish to prolong the experience. He was laid flat on his back in a nylon web, encased in baggy reflective coverall and under that a tight garment resembling a diver's wet suit (a skintight space suit). The neckseal and helmet were uncomfortable, and it was an effort to exhale against the higher pressures in the helmet.
     He had thought waiting for the launch the most unpleasant experience he'd ever had: lying awkwardly on his back, with no control of his destiny, enclosed in steel; then the laser cut in.
     He weighed far too much. His guts ached. Like the worst case of indigestion imaginable, he thought. There was no way to estimate the time. He tried counting, but it was too difficult, and he lost count somewhere. Surely he had been at eighty seconds? He started over again.
     There was noise, the loud, almost musical two-hundred-fifty-cycle tone of the explosions produced as the laser heated the air in the chamber under him—how close? he wondered. That great stabbing beam that could slice through metal aimed directly at him; he squirmed against the high gravity, and the effort was torture.
     The noises changed. The explosion tone drifted down the scale. He was beyond the atmosphere, and the laser was boiling off material from the thrust chamber, reaching closer and closer to him—

     Silence. The crushing weight was gone. He was falling endlessly, with no way to know. Was he in orbit? Or was he plunging downward to his doom? He closed his eyes to wait, and then he felt he was truly falling, with the sick sensations of a boat in motion—he opened his eyes again to orient himself in the capsule.
     Will they pick me up? There was no reason they shouldn't. New crewmen arrived weekly, and he was merely another. He listened for a voice, a signal, anything—
     "Hullo, laddie. All right in there?"
     Aeneas grabbed for the microphone and pressed the talk switch. "That was one hell of a ride." He fought for control of his voice. "I think I'm all right now."
     "Except that you feel like letting the world's record fart, right?" the voice said. "Go ahead. You'll feel better." (one of the drawbacks of a skintight space suit)
     He tried it. It helped.
     "Hang on there, mate. Be alongside in a minute," the voice said. It took less than that. There were clunks and thuds, and the capsule jarred with some impact. "Righto. You're new in this game, they tell me."
     "Yes, very," Aeneas replied.
     "Right. So we'll start by testing your suit. I've got a bottle attached to the outlet, crack the atmosphere evac valve a half turn, there's a good chap."
     A short moment of panic. The capsule held half an atmosphere. When the capsule was evacuated, only his helmet above the neckseal would contain pressure. The tight garment he wore was supposed to reinforce his own skin so that it would be able to hold the pressure differences, and it had worked in the ground training chamber; but there had been physicians waiting there. Aeneas did as he was told. As the air hissed out, the pressure in his guts returned, but worse.
     "Fart again, lad. How's the breathing?"
     "All right." He carried out the instruction. Again it helped. It was hard work to breathe out, but there didn't seem to be any problems.
     "Good. Open the valve the rest of the way and let's get you out of there." Pumps whirred, and he felt more sensations of internal pressure. The wetsuit was very tight around every part of his body. His heart pounded loudly, and he felt dizzy.
     "Now unstrap and open the hatch."

     The steel trap around him seemed comfortable and safe compared to what he might find outside. Aeneas gingerly unfastened the straps that held him to the D-frame-webbed bunk and immediately floated free. It took longer than he had thought it would to orient himself and get his feet braced so that he could turn the latches on the hatchway, but Aeneas was surprised to find that he had no trouble thinking of what had been the capsule "wall" as now "down" and the hatchway as "up." The falling sensation vanished as soon as there was something to do.
     The man outside hadn't mentioned the tether line on its reel on his belt, but the ground briefing had stressed that before the hatch was open he should clip the tether to the ring by the hatchway. That took fumbling, but he managed it.
     The hatch opened smoothly and he put his head outside. There was brilliant sunshine everywhere, and he was thankful for the sun visor and tinted faceplate of his helmet. Crisp shadows, Earth an enormous bulging circular mass of white clouds and blue sea, not below but just there; stars brilliant when he looked away from Earth and sun . . . he had seen the pictures a thousand times. It wasn't the same at all.

     He used his hands to rotate himself. There was an odd vehicle about seven meters long at the aft end of the capsule. Its nose was shoved into the capsule thrust chamber, and it reminded Aeneas of dogs (maybe "dog-sled?"). An open framework of thin aluminum bars with—saddles? But why not? A mirrored helmet atop bulky metallic shining coveralls perched on the nearest saddle. Aeneas couldn't see a face inside it.
     "One of the ones who listen, eh?" the voice said. "Jolly good. Now you see that line above you?" Aeneas looked up and saw an ordinary nylon rope. It seemed to be a solid rod. "Get hold of it and clip it on your belt. After that, reach inside and unclip your own line. And don't be slow about it." There was a pleasant note to the voice, but it expected to be obeyed.
     Aeneas complied quickly. He was reeled very slowly toward the spindly personnel carrier, and with a lot of difficulty and help from the pilot managed to get astride one of the saddles. His feet slipped easily under loops in the thing's "floor"—Aeneas supplied the quotation marks because there was only a minuscule grillwork there—and a safety harness went around his waist.

     Now that he was in the carrier, he could look around, and he did unashamedly.
     The launch crew had cut it pretty fine, Aeneas told himself. Heimdall floated less than a kilometer away.
     It looked like a junkyard. Two large curved cylindrical sausages on the ends of cables rotated around each other at a distance of nearly half a kilometer. The sausages had projections at crazy angles: solar cell arrays, shields, heat dissipation projectors connected to the station by piping, antennae. There was an inflated tube running from each cylinder to an amorphous blob between them, and part of the center structure rotated with the cylinders. Most of the center did not rotate.
     Other junk—the pregnant machinegun shapes of supply capsules, cylinders of all sizes, inflated structures of no recognizable shape—floated without apparent attachment near the axis of spin. Solar panels and orange sunshades lay everywhere. Heimdall had no real form.
     "Quite a sight, isn't it?" his companion said. "Name's Kit Penrose, old chap. Officer in charge of everything else. Weight control, atmosphere recycling, support systems, all the marvy things like that. Also the taxi driver. Who're you?"
     "Oh, Christ, a bloody Scot. You don't sound one. Engineer?"
     Aeneas shrugged, realized the gesture couldn't be seen, and said, "Like you. Little of everything, I suppose. And I'm American."
     "American, eh? Whoever or whatever you are, the ground crew seemed worried about you. Well, you're OK. Here we go." He did something to the panel in front of him and the spindly structure moved slowly toward the satellite. His capsule was still attached at the nose. "We'll just take this along, eh?" Penrose said.
     "Yes, my kit's in there." And I may need everything in it, Aeneas thought.
     It took a long time to cover the short distance to the station. Kittridge Penrose burned as little mass as possible. "Energy's cheap up here," he told Aeneas. He waved carelessly at the solar panels deployed everywhere and at mirrors fifty meters across that floated near the station. The mirrors were aluminized Mylar or something like it, very thin, supported by thin fiberglass wands to give them shape. "Plenty of energy. Not enough mass, though."

     As they neared Heimdall, it looked even more like a floating junkyard. There was a large cage of wire netting floating a hundred meters from the hub, and it held everything: discarded cargo and personnel capsules, air tanks, crates, and cylinders of every kind. It had no door except an inward pointing cone—an enormous fish trap, Aeneas thought. They headed for that, and when they reached it and killed their approach velocity, Penrose unfastened himself from the saddle and dove into Aeneas' capsule.
     He emerged with two sealed cylindrical fiberglass containers of gear Aeneas had brought up and clipped them to the wire net of the cage. He did the same with the spindle vehicle they'd crossed on, then did something that released the personnel capsule from its faintly obscene position on the taxi's nose. Penrose gripped the cage with one hand and strained to shove the discarded capsule with the other.
     Nothing seemed to happen. Then the capsule moved, very slowly, down the tube into the cage; the motion was only barely apparent, but Penrose turned away. "Takes care of that. We'll have a crew come take it apart later. Now for you. I'll carry your luggage."
     He reached down and pulled the safety line out of the reel on Aeneas' belt and clipped it to his own. "Now you're tethered to me, but if you drift off and I have to pull you in, I'll charge extra for the ride. Follow me, and the trick is, don't move fast. Keep it slow and easy."

     They pulled themselves across the wire cage. It looked like ordinary chicken wire to Aeneas, a more or less sphere of it a hundred meters in diameter. There were other blobs of wire cage floating around the station. When they got to the side of the cage facing Heimdall, Aeneas saw a thin line running from the cage to the nonrotating hub between the cylinders. Up close the rotating cylinders on their cables and inflated tunnel looked much larger than before; twenty meters in diameter, and made of segments, each segment at least twenty meters long. They pulled themselves gingerly along the tether line to an opening ahead.
     There was no air in the part of the hub they entered. Penrose explained that the interface between rotating and nonrotating parts was kept in vacuum. Once inside, Aeneas felt a gentle tug as the long tube, leading to the capsules at the end of the tether line pushed against him until he was rotating with it.
     Before Aeneas could ask, Penrose pointed up the tube away from the direction they were going. "Counterweights up there," he said. "We run them up and down to conserve angular momentum. Don't have to spend mass to adjust rotation every time somebody leaves or comes aboard. Course we have to use mass to stop ourselves rotating when we leave, but I've got an idea for a way to fix that too."

     As they descended, Aeneas felt more weight; it increased steadily. They passed into the first of a series of multiple airlocks. Then another, and another. "Hell of a lot easier than pumping all this up every time," Penrose said. "Feel pressure now?"
     "A little. It's easier to exhale."
     "You could breathe here. Not well." They passed through another set of airlocks and felt increasing weight; after that it was necessary to climb down a ladder. The walls of the silo they were descending were about three meters in diameter. They stood out stiffly from the pressure and seemed to be made of the same rubberized cloth as his pressure suit, but not porous or permeable as his suit was.
     Eventually they reached a final airlock, and below that the silo had metallic walls instead of the inflated nylon. The final airlock opened onto a circular staircase and they climbed down that into the cylindrical structure of the station itself.

From HIGH JUSTICE by Jerry Pournelle (1974)

(ed note: Cot-Vee = Cargo Orbital Transfer Vehicle {COTV}, Pot-Vee = Personnel Orbital Transfer Vehicle {POTV}, Eff-Mu = Extra Facility Maneuvering Unit {EFMU})

      “Med, emergency in progress. Please stand by for possible rescue attempt. Better stand by with Pumpkin Array Subassembly Module Two Zero Two’s on its way up from LEO Base. They’ve had an accident. The survivors are in the personnel module, with the life-support system out and only a UHF emergency locator transmitter with limited voice capability.”
     “How many casualties?” Torn asked.
     “The brief report said three dead—one on EVA, the other two in the control module when it dumped to vacuum. The remaining four are apparently alive and uninjured in the personnel module, but they have life-support air for only an estimated seven hours.”
     Tom turned to Fred Fitzsinnnons. “Stumpy, power-up the Pumpkin and be ready to go. I don’t know where the subassembly is or whether we can reach. it with the Pumpkin. I’m going to Central. Dorothy, get things ready here for hypoxia therapy and possible abaryia resuscitation.”

     Tom located Herb Pratt surrounded by a bank of readouts and panels at Central’s main overview consoles. “We’ve got Doc Noels here now,” Pratt addressed the other three images on the screens. “Doc, are your people standing by to handle whatever medical problems might arise from this?”
     “We’re always ready for whatever crisis arises,” Tom replied curtly. “Can you tell me what’s going on, please? You’ve got a problem? Where are the Edison and the Steinmetz? Can’t those Pot-Vees rendezvous?”
     “Doc, if you’ll listen, you’ll discover what our problems are,” Pratt told him with uncharacteristic tact, either because he had really come to respect the GEO Base doctor or because the Hawk was on the conference net.

     “Array Subassembly Module Two Zero Two left LEO Base on schedule,” Pratt forged ahead. “According to its trajectory, the electric thrusters would boost it to GEO Base in seventeen-point-two hours. The normal crew of seven was aboard—two guidance-and-control technicians, two electric-thruster mechanics, two power-bus controllers, and the array commander. At fourteen-twenty-one, Zulu time, one of the electric-thruster mechanics, Bob Henson, got into his P-suit, cycled through the transfer lock, and powered-up the Eff-Mu to go out and check Thrusters Five and Eleven on the far dorsal surface of the array. Both thrusters were acting intermittently. There was no telemetry on the Elf-Mu, so we don’t know what happened when Henson started to move out along the array. Maybe a thruster valve stuck—we’ll never know. But he put the Eff-Mu right through the side of the pressurized control module.
     “The pressure in the control module dumped immediately,” Pratt continued soberly, “killing Lem Udevitz, the subassembly commander, and Sally Renquist, a control tech: As a matter of fact, they were blown out through the hole in the module wall. The presence of that much gas in the vicinity of the array, plus the presence of the Eff-Mu, which may also have dumped to vacuum and added to the out-gassing, caused the main array bus-bar junctions near the control module to arc. You don’t short out a nineteen-megawatt array subassembly without fun and games. All the protective circuits activated. The bus bars acted like massive fuse links and vaporized. We don’t know what happened to Henson and the Eff-Mu, but our radar signature says the Eff-Mu isn’t anywhere around the subassembly now. It may have been vaporized in the arc-over, or it may be tumbling out of control with all circuits dead somewhere between here and LEO Base.”
     Pratt checked two computer display readouts. “They lost most of the pressure in the living module before somebody slapped something over the holes and sealed them. Three of the survivors suffered the bends from the rapid decompression. Fortunately, one of the power-bus controllers was in her P-suit and was able to act quickly enough to save most of the life-support consumable gases for the module.
     “At this point, four of them are still alive in P-suits in the living module with emergency battery power for illumination. They’ve got their P-suits plugged into the emergency life-support fittings, and they’re trying to scavenge as much of the life-support consumables as possible. The power-bus controller found the emergency locator transmitter (ELT), got it on the air, and transmitted the basic elements of this report. Then she shut down the voice-transmission capability to conserve battery power. We’re still picking up the locator signal.”
     Pratt looked around at the three screens and concluded, “Here’s the problem: They’ve got … uh … seven-point-eight hours of life-support consumables left, according to calculations based on information received in the brief ELT report. The Edison is one-point-three hours from docking at LEO Base; no way for Nat Wallace to turn it around and head for the accident scene. He’s running heavy. He’ll have to be refueled, and that will take at least two hours after he docks. There’s no way he can make it to Two Zero Two before they run out of air.
     “The Steinmetz is two-point-nine hours from docking at GEO Base, and Ross Jackson’s running loaded with enough delta-v plus standard reserves to make GEO Base rendezvous, period. There’s no way he can reshape orbit to get to Two Zero Two in time, and when he got there he couldn’t do anything because he has only enough life-support for his passenger manifest, plus normal reserves. He wouldn’t have the delta-v capability to get to either LEO Base or GEO Base afterward. We’d just have a Pot-Vee and fifty more people stranded along with the subassembly.”
     Pratt looked around again. “That’s it in a nutshell, confirmed as best we can by radar track and signature analysis from here. We’re rechecking as many permutations and combinations as possible with computer runs, looking for some trajectory that would let us rendezvous a Pot-Vee with Two Zero Two, but we haven’t found it yet.

     “One guidance-and-control tech, Pat Mulligan. One electric-thruster mechanic, Jim Service,” Charlie Day announced from LEO Base as he checked his departure manifests. “And two power-bus controllers, Ed Swenson and Lucky Hertzog—Lucky was the one in the P-suit when the accident happened, and she was the one who sent the report.”
     Lucky? In that accident? With less than eight hours of life-support left? And no way to get to them with the Pot-Vees? Tom swallowed and tried to think straight. Given the situation, what could be done? What could he do?
     Finally, Owen Hocksmith broke the brief silence. “Four people and damned little time. Anybody got any ideas? To hell with the schedule, and to hell with the rules! Somehow, we’ve got to make an effort to get to them. No, we’ve got to get to them and bring them out of this alive!”

     There was silence from everyone on the conference net.
     “Dammit!” Hocksmith exploded. “We move thousands of tons of cargo and hundreds of people around in orbit every day! Surely there’s some way we can get to four people in a transfer orbit within seven hours and with enough lifesupport to keep them alive, even if it’s for just long enough to get a Pot-Vee turned around and on its way.”
     Dan Hills spoke up earnestly. “Let’s think about that one. We don’t have to get them and get back. We just have to get to them within seven hours with enough oxygen to sustain them until we can get a Pot-Vee there. Charlie, Herb, what do you have up there that one man can boost and control, carry about fifty man-hours of Oh-two (10 hours of oxygen for 1 rescue pilot and 4 survivors), no guidance system, vectors being fed to the pilot verbally from analysis of the radar track?”
     “I haven’t got an Eff-Mu big enough,” Charlie Day replied. “How about it, Herb? You’ve got Eff-Mus that are bigger. Do any of them have the delta-v to reach Two Zero Two in time with a pilot and fifty man-hours of Oh-two?”
     “Hold on, let me get a readout on the delta-v required for a seven-hour rendezvous.”

     Tom moved to another keypad and display. He had an idea. He didn’t know if it would work or not. He couldn’t do the math, and he couldn’t program the computer. But he had access to a very large general-purpose computer net: GALEN. He didn’t know if GALEN could handle celestial mechanics, but he could certainly ask.
     It could, using its links through EuroMed to computers in Brussels and London, plus a link into a DOD computer net through Bethesda Naval Hospital. He asked GALEN and its peripheral systems to solve the problem for him. GALEN already had all the parameters on the Pumpkin. All Tom had to do was feed it numbers on the location and trajectory of Two Zero Two and the location and orbit of GEO Base.
     When he was through, he had the answer.

     Dan Hills and Herb Pratt didn’t. “Mr. Hocksmith, the mission’s beyond the delta-v capabilities of any of our Eff-Mu vehicles,” Dan Hills announced. “They were designed as short-range craft for getting around the SPS during construction. They don’t have very much delta-v as a result.”
     “You’re the most negative problem solvers I’ve ever seen!” Hocksmith snapped back. “Four people out there, and we can’t come up with a way to get to them in time? Do you know what this could mean, gentlemen? It could mean that we get shut down for killing too many people. The hue and cry of the press could trigger the politicians and bureaucrats to do something, anything, to stop what they consider to be slaughter. We’re already in that position, as you damned well know. We’re supposed to be the world’s brightest people when it comes to space transportation. We’ve built and operated the biggest space transportation system in history. And we can damned well figure out some way to make it work to save four people! Think!

     Tom tapped Pratt on the shoulder and motioned for him to move over so he could get in the pickup’s field. The action came as such a surprise to Pratt that he moved immediately without a word. “Smitty, I’ve got an answer,” he told his old friend. “The Pumpkin, the GEO Base ambulance you designed for us, Smitty, It’s got more delta-v than any Eff-Mu because we need to move around fast here, which means high-g and gobs of thrust—in comparison, that is. It’s normally rated for a thousand pounds of payload. I’ve just been working with the GALEN computer, and I asked it whether or not I could get there as a single pilot in a P-suit with a cargo of five fifty-cubic-foot Oh-two backpack bottles. That’s about a hundred fifty pounds, plus me in a P-suit at two hundred pounds. Just to be on the safe side, I figured five hundred pounds; I may need some medical gear because three of those people are in severe pain with the bends. I can get there with the Pumpkin and enough Oh-two to save them. But I can’t get back. You’ll have to come rescue me with the Edison or the Steinmetz. That’ll give you ten hours after I make rendezvous. I can do it! Can you get to me in seventeen hours?
     “I won’t let you go,” was the comment from Hocksmith.
     “I won’t let Stan or Fred go. I’m a doctor, and those people may need a doctor, not a paramedic,” Tom explained.
     “We can get to you,” Pratt put in, looking at the display screen linked to GEO Base computer. “It’ll be close, but we’ll get there. Better take a couple of spare bottles, Doc, just in case.”
     “Can’t. I’ll be rendezvousing with electric thrusters as it is. Barely enough propellant to get me started and almost stopped. When it’s that critical, I want about five-percent reserve. Just get there within ten hours after I do, Herb.”
     Charlie Day broke in. “We’ll start from this end with the Edison, too. We’ll come after you from LEO and GEO. This operation’s got to have some redundancy built in somewhere!
     “Okay, I’ll be depending on both of you after I get to Two Zero Two,” Tom said. “I’ll fly by vectors from GEO Base radars and lidars. Herb, have your gang track me and give me those vectors. You’ll have my position, my trajectory, and your computer power—in short, all the data you’ll need. All I need is communication with you. No other way to do it.”
     “You’re right,” Herb remarked.
     “Tom, forget it! You’re not going!” Hocksmith yelled.
     “Smitty, you forget it! And shut up! You’re sitting on your ass down there with gravity and an atmosphere around you. Don’t try to run this operation by long distance. Herb, Charlie, and Dan work for you as employees—they’ve got to follow your orders. But I’m one of your contractors, and the Pumpkin was bailed to me by Eden Corporation. So you can’t tell me what to do at all! Or do you want four people to die?”
     Hocksmith threw up his hands. “Goddammit, go get’em, T.K.! But please be careful!”
     “A martyr I’m not,” Tom replied flatly. “Let’s go, Herb. Time’s a-wasting!”

     Tom was a little under his mass estimate. He did take a few extra backpack bottles and the equivalent of a spare fan belt. “I want a hand-portable communicator or a booster amplifier on my backpack radio, Herb. I will have to go EVA to get aboard Two Zero Two, and I want to be able to talk to you if necessary. I also want the unit as an ELT if something happens.”
     ;“We’ll give you a little extra delta-v, Tom,” Pratt told him. “I’ll have three of our Eff-Mus couple to you during GEO Base departure boost and supplement your own thruster on the Pumpkin. They’ll undock after they’ve boosted you. Sort of a two-stage vehicle. Computer says that’ll give you a ten-percent reserve—slim, but a hundred-percent improvement on the five-percent reserve you thought you’d need.”
     “Still going to be close, but thanks for the additional help,” Tom said as Fred buddy-checked the P-suit connections.

     The undocking was very gentle. Tom was reluctant to use any delta-v he didn’t have to. As he backed away from the med module’s docking. port, he saw on his displays that three Eff-Mus had drawn alongside. Into his helmet speaker came the voice of one of the Eff-Mu drivers. “Pumpkin, Eff-Mu Fourteen. We’re ready to move in and couple. Don’t try to hold position; let us move on you.”
     “Roger, Eff-Mu. GEO Base, Pumpkin, radio check.”
     “Loud and clear, Pumpkin. How me?”
     “Five by. While the Eff-Mus are coupling up, let’s check the data links.”
     “Go ahead, Pumpkin.”
     Tom exercised his small on-board computer, testing its megabyte memory (hah. Nowadays people have thousands of times more RAM in their smartphones. Not radiation-rated, though) and squirting the test data on the up-link to GEO Base, where the GEO computer examined it, determined it was all there, and echoed it back to the Pumpkin accompanied by its own test data. Within three seconds, the two computers were happy with each other and in communication.
     “Pumpkin, GEO Base,” Pratt’s voice called. “The Eff-Mus will maneuver you into boost attitude. We’re working this mission with Earth-oriented references, equatorial category.”
     Tom informed his computer and control systems. “Okay, Geo Base. Pumpkin’s ready for attitude positioning.”
     The three Eff-Mus gently lined up the Pumpkin.
     “Close enough,” Herb told Tom. “Your down-link data matches. Computer’s grinding out the final trajectory elements. Stand by for real-time updates on the up-link.”
     When the Pumpkin boosted from GEO Base on its errand of mercy, the computer estimated that Two Zero Two had six-point-nine hours of life-support available. The estimated trajectory time was six-point-eight hours.
     “I don’t like those numbers, Herb. Too many chances for error, and I know this is only a quarter-percent data.
     “No, we’ve got very accurate info on Two Zero Two. Air Force is feeding us their SpaceTrak data, too, and it cross-checks.”
     “Okay, Eff-Mus have separated,” Tom reported, “and I’m getting a solid up-link data signal. I’m on manual control.”

     When Tom had taken flight training from Dick Callins at the Roswell airport years before, he never thought he would find that detestable simulated-instrument hood training useful in flying a spacecraft. But that was exactly what he was doing. Instrument flight training had taught him to ignore the inputs from his otoliths and his kinesthetic senses, to give up flying by the seat of his pants. Then, as now, he was forced to rely only on the data that was presented to him by instruments. And it required the same degree of control precision—only the data presentation was slightly different.
     He still had a gyro attitude indicator and a gyro vector indicator. Otherwise, the instruments were fully electronic.
     It was a simple task for computers. Radar and lidar from LEO Base, GEO Base, and the Earth’s surface tracked the Great Pumpkin’s beacon, providing the computers with direction, range, and Doppler relative velocity. The computers were also receiving tracking data from the ELT beacon in Two Zero Two; they knew where it was—and where it was going to be. The instructions for right-left, up-down, and fast-slow were transmitted to the Pumpkin on the data up-link, where the ship’s computer converted the data for display, telling Tom how and how much to change direction or thrust. The Pumpkin's simple autopilot couldn’t be used on this long flight because neither it nor the Pumpkin’s inertial guidance system had the accuracy required. They didn’t have to be accurate for operating around GEO Base and the SPS assembly; they just had to keep general track of where the Pumpkin was. Thus, Tom had to fly the Pumpkin by hand, keeping dots of light centered on displays and making sure that the indicators on graphic displays stayed right on the lines.
     It wasn’t difficult, because nothing happened very fast as long as Tom kept on top of things constantly.

     “Going right down the tunnel, Pumpkin,” Pratt told him.
     “Any further messages from Two Zero Two, Herb?”
     “Nothing but the beacon signal,” the base boss reported. “Its code hasn’t changed and indicates the situation’s the same.”
     “Any way to get word to them that we’re coming?”
     “They have no receiver, and they’re sealed in that living module, so there’s no way to send even a laser signal to them.”
     “That’s got to be grim,” Tom observed.

     The Pumpkin was coming up on final trajectory velocity. Tom concentrated on the displays, his hand on the main throttle with the Vernier throttles just below. He was also receiving a verbal countdown from Pratt. Five feet per second short of final velocity, he chopped the main engine and used the verniers to bring the Pumpkin to precisely the required velocity.
     “Looks good, Pumpkin. Right down the pike. Take five, because we won’t do a mid-course correction for two hours yet. I want to let the trajectory errors build until we’ve got a reliable track that we can correct with greater precision. No sense burning up vernier delta-v by correcting every little glitch in the radar track.

     Tom couldn’t help but think of Lucky Hertzog, trapped in that can, knowing how much oxygen was remaining but not knowing whether anybody was on the way, and not being able to find out. He agonized because he knew it must be hell. On the other hand, he didn’t think Lucky would come apart under the circumstances. She was made of stout stuff. He knew there would be no hysteria, only tight-jawed discipline right to the very end if necessary.

     “Pumpkin, GEO Base. Here’s your latest ETA at Two Zero Two.” Herb’s voice returned him to reality. “It’s tight, Tom. The estimate’s converged with the flight time. We show a rendezvous only five minutes before life-support exhaustion. I think it’s too close to call. Let’s hope Two Zero Two has instituted drastic conservation measures. If they have, you’ll make it.”
     “I refuse to trust any computer when it comes to that close a call on the chances of living or dying,” Tom snapped back. “I’ll make it, Herb, because we’re dealing with people, not with computers.”
     He hoped he was right.

     Tom saw it on the forward screen through a ghostly haze of electric-thruster plasma. The huge solar array gleamed in the sunlight and bright specular reflections overloaded the video pickup, causing streaks of overexcited display phosphor to paint wiggly lines on the tube face. He fired the vernier thrusters carefully to rendezvous as precisely as possible with the personnel module that appeared only as a tiny polygon on the near end.
     According to the digital readout, he didn’t have a foot-second of delta-v to spare.
     The computer also told him he was running out of time.
     He’d have to move in on the personnel module with one single continuous application of the thruster in order to save time. Then he’d have to do a fast EVA.
     He had prepared for that. During the hours of coast-in, he’d pumped the Pumpkin’s cabin atmosphere back into the ship’s life-support system and carefully blown-down the cabin to vacuum; in fact, he had used the blow-down to provide some fractional delta-v, which gave him a trifle more reserve. He’d even opened the hatch to vacuum. When he got to Two Zero Two, he was ready to move—fast.

     Suddenly his instruments began reporting relative velocity between the Pumpkin and Two Zero Two. The computer was presenting projections and forecasts of future velocities, positions, and closing rates. He knew he would have to be exceptionally precise and that he had only one chance. He realized that this was the, same degree of precision he had to exercise as a surgeon, and, as in surgery, he had only one opportunity to succeed.
     “Gently! Positive pitch! Too much, back it off! Bang yaw right a couple of times. Coming right on in.” Tom talked to himself as he often did during an operation or during instrument approaches in his Maule. “GEO Base, Pumpkin! Closing nicely. I’m videotaping the monitors, but I’ll give you a verbal — There’s a big hole in the side of the command module and a series of smaller holes in the personnel module. The ones in the personnel module look as if they’ve been sealed from the inside. There’re no lights showing. I’m receiving only the modulated r-f signal from the ELT. Okay, closing slowly … Ten feet and dead in space. I’m holding it there. I don’t want to bump the personnel module because I don’t know what internal damage it’s suffered, and it could collapse if I whanged it. How’s my timing?”
     “Tom, it’s too close to call,” Pratt admitted.
     “Okay, I’m uncoupling, going to backpack. My transmission may get garbled because I’m switching to the booster transmitter strapped to the backpack. Now I’m free. Moving to the hatch, hauling the backpack bottles with me. Out of the hatch. What a mess! Everything seems to be covered with a grayish deposit. Probably vapor deposition caused by the arc-over. The survivors are lucky. The reflectance of that coating is probably just enough to maintain a comfortable interior temperature in the personnel module.”

     Tom pushed off the five feet across the void to the damaged module, not even taking the time to latch a safety line. He hit with both feet and bounced back in spite of the fact that he had used his knees to absorb his momentum. He would have bounded right back to the Pumpkin’s hatch except for the two-hundred-pound bag of backpack oxygen bottles in his left hand. Its momentum forced him around as it kept going and thudded into the module. He planted his feet on the module again, looked for. handholds, found them, and pulled himself to the hatch.
     He banged on the closed hatch and could feel the vibrations through the soles of his P-suit boots. There was no response.
     “Dammit, I’m too late!”
     He tried to twist the latch, but couldn’t do it. He had to hold on to the bag of oxygen bottles with his left hand and, therefore, could work only with his right. His body twisted instead. So he banged again, hoping he might somehow dislodge the hatch-closure dogs or that someone might detect his banging and open from inside.
     “Open up! For God’s sake, open up!” He found himself screaming in his helmet that was pressed against the hatch. Maybe his voice would penetrate by direct contact.
     He almost fell into the module when the hatch suddenly swung open.
     And he found himself faceplate to faceplate with Lucky. She touched helmets, and he heard her say, “Well, you took long enough to get here, but did you have to make such a racket?” She reached out, put her arms around the neck of his P-suit, and hauled him into the module.
     And she continued to hold him tight.

From SPACE DOCTOR by Lee Correy (G. Harry Stine) 1981

Lunar Escape System

This is an emergency lunar escape vehicle concept, in case an Apollo Lunar Module crashed upon landing. It was designed to be assembled from various parts canibalized from the wreck. Note that in the two-man version, the pilot gets an acceleration chair, but the poor second astronaut is slung under the chair by straps. You can read more about this here, and here.

Space Pod

A space pod is a small pressurized vehicle with one or more waldoes or mechanical arms. They are often used for space construction and maintenance. In the movie 2001 A Space Odyssey, they were referred to as "EVA pods." In Wernher von Braun and Disney's Man In Space series, they were called "bottle suits." They are also known as "closed-cabin cherry picker", "manned autonomous work system", and the ever popular "man-in-a-can." One of their main advantages over a soft space suit is that they solve the depressurization problem.

There are some designs that carry more than one astronaut, these are in the gray area between space pods and space tugs.


Jameson turned back toward the repair rig. The two lobsters, bright orange against blackness, were maneuvering themselves into position, getting a helpful nudge or two from the men swarming around them. A repair lobster was nothing more than a simple cylinder with a plastic bubble for the head of its operator at one end. It got its name from the two big claw-like waldos at the forward end and the twin rows of smaller specialized limbs down its ventral surface.

One of the lobsters anchored itself on the Callisto lander’s hull and grasped the embedded landing foot. It tugged gently, trying to do as little further damage as possible. The leg came free. There was a little frosty explosion of particles of trapped air. A couple of space-suited men took charge of the damaged leg and ferried it back to the repair frame. One was Chinese, one American. Jameson grinned without humor. Even the garbage detail had to be bi-national.

The other lobster brought over a replacement leg, an articulated metal lattice five meters long, with the flat mesh pad of the landing foot at one end. Swimming behind it was a four-man crew with laser cutting torches.

From THE JUPITER THEFT by Donald Moffitt (1977)

I'm back to trying to put together some semi-realistic design for near-future space flight. In this case, I'm mainly trying to tackle a couple of problems. The first is the restrictions put on by current EVA technology. There's no such thing as being able to put on your spacesuit, go out the airlock and deal with an emergency these days. A minimum of about 20 hours of slow decompression and prebreathing pure oxygen is required before anyone goes out into space. Thats because the cabin environment of the Space Station, and the Shuttle is oxygen/nitrogen at sea level pressure, while the suits operate with pure oxygen at 5 p.s.i. They do that because, with present, vintage 1980 space suits, the arms and legs become impossible to bend if the pressure is any greater. The other problem is radiation shielding. For long stays outside, or any meaningful work beyond the Earth's ionosphere, the present suits just have inadequate radiation protection.

The potential solution is MAWS. It will have the same internal pressure as the station, or whatever long duration habitat we have in the future, because it doesn't have flexible joints. Instead it uses a couple of miniature versions of the station's robot arm. Its possible to put much better radiation shielding around MAWS, too. Probably the first exploration of asteroids or moons of Mars will be done in something like this design.

So this is the baseline look of the MAWS, as loosely worked out by NASA. Should it have a second set of heavier arms? Where would EVA equipment be attached? In general, what do you think of the idea?


Discovery's extravehicular capsules or "space pods" were spheres about nine feet in diameter, and the operator sat behind a bay window which gave him a splendid view. The main rocket drive produced an acceleration of one-fifth of a gravity—just sufficient to hover on the Moon—while small attitude-control nozzles allowed for steering. From an area immediately beneath the bay window sprouted two sets of articulated metal arms or "waldoes," one for heavy duty, the other for delicate manipulation. There was also an extensible turret carrying a variety of power tools, such as screwdrivers, jack-hammers, saws, and drills. Space pods were not the most elegant means of transport devised by man, but they were absolutely essential for construction and maintenance work in vacuum. They were usually christened with feminine names, perhaps in recognition of the fact that their personalities were sometimes slightly unpredictable. Discovery's trio were Anna, Betty, and Clara.

Once he had put on his personal pressure suit—his last line of defense—and climbed inside the pod, Poole spent ten minutes carefully checking the controls. He burped the steering jets, flexed the waldoes, reconfirmed oxygen, fuel, power reserve.

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

Grumman DC-5 EVA Craft

     Mass at Earth Gravity: 1,387 Kg.
     Overall Diameter: 1.98 m.
     Capacity: One Person Standard; Three Person Emergency
     Propulsion systems: Ten Mk 12 (140 Kgs. Thrust) for major course changes along all axes; Eight Mk 17 (35 Kgs. Thrust) for precision maneuvers; Eight Mk 8 micro-thrusters (10 Kgs.) for low-gravity station-keeping; Five Mk 14 (80 Kgs. Thrust) provide roll; One Mk 37 (500 Kgs. Thrust) for use in emergency.
     Life Support: 12 Hrs. (One Person)
     Radar: Grumman EPS-2D; Long Range; Active Pulse
     Other Equipment: Explosive Bolt Door Separation*; Short-range Object Approach System and Transponder; Complete HAL 9000 Data link System; Automatic Thruster Control; Auto Hover; Eight-Channel communication system; Advanced Manipulator Control System; Two-hour Oxygen Reserve System.
     Notes: The Grumman DC-5 carries can carry little in the way of food and water stocks, due to short life support capacity. A single air conditioning vent is provided.
     Misc. Technical Information: (From Frederick Ordway and the British Interplanetary Association)
     Propulsion: A subliming solid system provides vernier propulsion, wherein the solid propellent sublimes at a constant pressure and is emitted from a nozzle. Such reaction jets will last for long periods of time, have great reliability and use no mechanical valves. The main propulsion system is powered from by storable liquids.
     Mechanical Hand Controls: Selection controls are placed on each side so that the appropriate hand must be removed from the manipulator to select a tool or to park. Selection of a tool returns the arm to the 'park' position, where it leaves the 'hand', then the arm goes to the appropriate tool and plugs in. In doing so, it inhibits the 'finger' controls on the manipulator, so that when the operator returns his hand into the glove he can only move a solid object, not individual fingers.
     Television: It was found possible to produce all-round TV coverage with eight fixed cameras. This, however, did not give a sufficiently accurate picture for docking or selecting a landing space. For this purpose, the field of view can be narrowed or orientated; controls are included for this purpose.
     Normally, the TV link is occupied by the internal camera, so that the parent craft can monitor the pod interior. The pilot can switch in any other camera for specific purposes (survey, etc.) reverting to interior camera for normal work.
     Proximity Detector: This is the safety system with omnidirectional coverage working from the main communication aerials. It gives audible warning when the pod approaches a solid object. This is necessary as a safety measure as the pilot cannot monitor seven or eight TV displays continuously. The system also detects an approach to an object, the speed of which is too high to be counteracted by the vernier thrust settings on the control system. In this event, full reverse thrust is applied, overriding the manual control setting. The system depends upon a frequency modulated transmission and under safe conditions results in a low, soft audible background signal. This continuous signal is considered necessary in order to provide a continuous check on a vital safety system. If the speed of an approach to an object becomes dangerous compared with the distance from it, the tone becomes louder and higher pitched, and, if unchecked, end in a shrill note accompanied by reverse thrust. The system also works in conjunction with a transponder (to the give the necessary increased range) to measure distance from the Discovery.
     Flying Controls: Manual controls are considered necessary both as a standby and for local maneuvers. Two hand control sticks, each with two degrees of freedom and fitted with twist grips, provide the necessary control about six axes.
     Analog information is presented for attitude, heading rate and distance; these can be referred to local ground (for landing, takeoff, etc.), course (which enables the pilot to face forward, head up, on any preselected course, or parent ship (for docking, local maneuvers, etc.) This data has to be presented, as the pilot has to act immediately on them. This is the most easily assimilated display. A variation in full scale rate, which can be applied by the control sticks, is included; this allows the full stick movements to result in any proportion of vernier motor thrust, thus giving a 'fine' control for local maneuvers.

He was nearer to the sun than any man had ever been. His damaged space-pod was lying on no hill, but on the steeply curving surface of a world only two miles in diameter.

Even then, it was still possible for men in the tiny self-propelled space-pods — miniature spaceships, only ten feet long — to work on the night side for an hour or so, as long as they were not overtaken by the advancing line of sunrise.

He was still not quite sure what had happened. He had been replacing a seismograph transmitter at Station 145, unofficially known as Mount Everest because it was a full ninety feet above the surrounding territory. The job had been a perfectly straightforward one, even though he had to do it by remote control through the mechanical arms of his pod. Sherrard was an expert at manipulating these; he could tie knots with his metal fingers almost as quickly as with his flesh-and-bone ones.

He had aimed the pod with its gyros, set the rear jets at Strength Two, and pressed the firing button. There had been a violent explosion somewhere in the vicinity of his feet and he had soared away from Icarus—but not toward the ship. Something was horribly wrong; he was tossed to one side of the vehicle, unable to reach the controls. Only one of the jets was firing, and he was pinwheeling across the sky, spinning faster and faster under the off-balanced drive. He tried to find the cutoff, but the spin had completely disorientated aim. When he was able to locate the controls, his first reaction made matters worse—he pushed the throttle over to full, like a nervous driver stepping on the accelerator instead of the brake. It took only a second to correct the mistake and kill the jet, but by then he was spinning so rapidly that the stars were wheeling round in circles.

Everything had happened so quickly that there was no time for fear, no time even to call the ship and report what was happening. He took his hands away from the controls; to touch them now would only make matters worse. It would take two or three minutes of cautious jockeying to unravel his spin, and from the flickering glimpses of the approaching rocks it was obvious that he did not have as many seconds. Sherrard remembered a piece of advice at the front of the Spaceman’s Manual: "When you don’t know what to do, do nothing." He was still doing it when Icarus fell upon him, and the stars went out.

It had been a miracle that the pod was unbroken, and that he was not breathing space. (Thirty minutes from now he might be glad to do so, when the capsule’s heat insulation began to fail… .) There had been some damage, of course. The rear-view mirrors, just outside the dome of transparent plastic that enclosed his head, were both snapped off, so that he could no longer see what lay behind him without twisting his neck. This was a trivial mishap; far more serious was the fact that his radio antennas had been torn away by the impact. He could not call the ship, and the ship could not call him. All that came over the radio was a faint crackling, probably produced inside the set itself. He was absolutely alone, cut off from the rest of the human race.

It was a desperate situation, but there was one faint ray of hope. He was not, after all, completely helpless. Even if he could not use the pod’s rockets—he guessed that the starboard motor had blown back and ruptured a fuel line; something the designers said was impossible—he was still able to move. He had his arms.

He slipped his fingers into the controls that worked his mechanical limbs. Outside the pod, in the hostile vacuum that surrounded him, his substitute arms came to life. They reached down, thrust against the iron surface of the asteroid, and levered the pod from the ground. Sherrard flexed them, and the capsule jerked forward, like some weird, two-legged insect… first the right arm, then the left, then the right… .

It was less difficult than he had feared, and for the first time he felt his confidence return. Though his mechanical arms had been designed for light precision work, it needed very little pull to set the capsule moving in this weightless environment. The gravity of Icarus was ten thousand times weaker than Earth’s: Sherrard and his space-pod weighed less than an ounce here, and once he had set himself in motion he floated forward with an effortless, dreamlike ease.

Yet that very effortlessness had its dangers. He had traveled several hundred yards, and was rapidly overhauling the sinking star of the Prometheus, when overconfidence betrayed him.

From SUMMERTIME ON ICARUS by Arthur C. Clarke (1960)


This is from Launching and Alightment Systems for Aero-Space Vehicles by the Wright Air Development Division. In the middle part of the report, they figure that it will be a big problem for two spacecraft to rendezvous safely. So they looked into all sort of possibilites.

Waldoes And Drones

For maximum protection of the astronauts, it is best to help them avoid leaving the spacecraft at all. They can stay in the relative safety of the habitat module while using waldo robot arms or free-flying drone pods to get the job done.

Waldoes are also used for berthing a spacecraft (not docking, berthing).


Mobile Servicing System (MSS)

The MSS is composed of three components — the Space Station Remote Manipulator System (SSRMS), known as Canadarm2 (successor to the original Canadarm), the Mobile Remote Servicer Base System (MBS) and the Special Purpose Dexterous Manipulator (SPDM, also known as Dextre or Canada hand).

Canadarm2 is usually attached to the MBS, which moves along a rail. However, Canadarm2 can detach and literally walk on the surface of the station to where it is needed, moving end-over-end like a giant metal inch worm. Either end can plug into special sockets ("power data grapple fixtures") built at strategic spots on the surface of the station. The only draw-back is that Canadarm2 cannot carry any equipment while in inch-worm mode, hence the MBS.

The main limitation is that each "step" must end at a socket, but this is due to power and control signal issues. A more advanced version might be self contained enough to not require sockets, just hand-holds or other protrusions that it could grab.

Canadarm 2 is quite large, 17.6 meters (57.7 feet) long when fully extended.


This is From Nuclear Shuttle Systems Definition Study Phase III Final Report Volume II Concept and Feasibility Analysis Part A - System Evaluation and Capability. Thanks to Erin Schmidt for bringing this report to my attention.


DARPA’s Robotic Servicing of Geosynchronous Satellites (RSGS) program is to develop technologies that would enable cooperative inspection and servicing satellites in GEO.

1964 Lockheed unmanned SCHMOO drone: "Space Cargo Handler and Manipulator for Orbital Operations"

G.E. Remote Manipulator Spacecraft (1968)

Space Tug

A space tug is a tiny spacecraft with over-sized engines and some means of grappling another spacecraft. If the tug pushes its cargo,it will have a massive push plate on its bow, with a core of structural members to transmit the thrust of its engines to the push plate. If the tug pulls its cargo, it will have cables and winches on its stern, and the engines will be vectored to fire backwards at an angle so it does not torch the ship it is dragging. The engines will suffer a reduction thrust penality proportional to the cosine of the engine angle.

Note that if nuclear propulsion spacecraft are involved, the tugs and the spacecraft will generally be designed to dock bow to bow. Otherwise you will be exposing the other ship to the radiation from your engine.

According to the Technovelgy site, the term "space tug" was invented in 1942 by Eric Frank Russell in his short story "Describe a Circle"

The Last Great War

(ed note: Nuclear Salt Water powered Frigate New Jersey wants to dock with colony on asteroid 624 Hektor. Nuclear Lightbulb powered Tug Brutus assists. Remember, with nuclear drive rockets using shadow shields the only safe way to dock is nose-to-nose.)

"Conn, tug Brutus requests permission to dock."

"Permission granted. Close the fuel valves."

As New Jersey shut down her main engine, the powder blue UN tug approached on thrusters. Fitzthomas watched on external cameras, never liking it when his ship was in others' hands, but powerless to do anything about it. The traffic rules within 100 k-klicks of Hektor were as plain and draconian as those of LEO: no unauthorized burns, and no open cycle nuclear reactors in operation under any circumstances. And the UN tug drivers were pretty good.

"Conn, Brutus is making her final approach. Docking in one minute."

"XO (executive officer), signal all hands."

"Aye sir." A moment later, Allen's voice came over the shipwide intercom. "All hands, prepare for ship to ship dock." He switched back to his private channel to the captain. "Let's hope whatever blue hat is driving that donkey cart knows how to actually fly a spaceship."

As it turned out, he could. Brutus and New Jersey touched nose to nose at barely a meter per second. Heavy duty docking latches locked the ships together, and Brutus extended a fiber optic probe into a receptacle inside New Jersey's docking ring.

"Conn, we have hard dock with Brutus. They are requesting propulsion access."

Fitzthomas removed a hard blue plastic key from his extensive key ring and inserted it into a blue lock. "Transferring propulsion access on my mark....mark." He turned the key and the clear plastic ring around the lock lit up blue. Brutus's pilot now had control over New Jersey's maneuvering thrusters. For the duration of the ride, Fitzthomas's hand would hover over the key, ready to cut Brutus out of the system, just in case.

Brutus's pilot could now also see what New Jersey's docking radar and aft cameras saw, a necessity since the bulk of the frigate would block the tug's line of sight—visual or otherwise—while they maneuvered. Brutus was little more than a nuclear engine (closed cycle, which meant no reactant could escape with the exhaust, at the cost of about half the ship's specific impulse, which didn't matter for a short range, low speed tugboat) with a sturdy docking ring and a cockpit jammed in between. In some operations, the tug was unmanned and guided by computer or radio control operator until it docked with the target ship, and then the tug would relinquish control of its systems to the target ship's pilot, or a harbor pilot brought on board for the purpose, saving some of the mass of reactor shielding for the cockpit and some of the ulcers for shipmasters, but the UN insisted on doing things the old fashioned way. Fitzthomas had heard of tugs which did the entire trip by remote control or onboard computer, but he'd rot in hell before he let some toe-picker play model airplane with his spaceship, and the United States Space Guard agreed.

New Jersey's thrusters fired, heeling the ship around 180 degrees, so that her bow, with the tug latched on, faced Hektor. Brutus then fired her main engine, continuing the deceleration burn New Jersey had started. Fitzthomas felt himself lift ever so slightly out of his chair. His ship's decks were aligned so "down" when they were under thrust was towards her main engine. With Brutus docked with her nose and her thruster pointing the other way, "down" was now, temporarily, in the direction of the overhead. One more thing for Fitzthomas not to like about the tugboat.

"Approaching Hammarskjöld docks. Ten minutes to docking."

From The Last Great War by Matthew Lineberger (not yet published)

Space Tug: Boeing

Boeing Space Tug
Thrust104,000 N
Isp460 sec
Restarts4 to 20/mission
Total Starts
Burntime1,000 sec/mission
100,000 sec/life
30 days active
180 days quiescent
Repair and
In Space
+3 years

The Boeing Space Tug is a modular design. This concept was later developed into the NASA Space Tug. One way to tell the difference is that the Boeing tug's crew and cargo modules were spherical, while the NASA tug's modules were cylindrical.

The information presented here is primarily from the Boeing Company Aerospace Group report Pre-Phase A Technical Study For Use Of Sat V, Int 21 & Other Sat V Derivatives To Determine An Optimum Fourth Stage (Space Tug). Specifically from Volume I Book III, and Volume II.

Modules and Kits

Modules were designed to fit in Space Shuttle cargo bay. Study assumes a space shuttle payload capacity of 24,500 kilograms delivered to an 180 kilometer orbit at a 28.5° inclination.

Modules are rated to be safely re-used a limited number of times, e.g., the crew module is rated for 10 lunar landings or 100 orbital missions. These are listed with the modules.

After each mission all modules need to be refurbished. This is assumed to cost 3% of the module's first unit cost. After the final use, module can be refurbished to be used once more on an expendable mission. Refurbishment is done in space, unless the tug has exceeded one year of operations in space or is to be used in an expendable mission.

Propulsion Modules
Propellant Mass7,620 kg18,053 kg28,100 kg
Inert Mass1,668 kg25,445 kg2,964 kg
Wet Mass9,288 kg20,595 kg31,087 kg
Mass Fraction0.8200.8760.905
Number Engines1
Engine Thrust104,000 Newtons
FuelLOX / LH2
Specific Impulse460 sec
Expansion Ratio225
Subsystems and Materials
StructureAluminum 2219-T87, Aluminum 7075-T6
MicrometeoroidHexcel Filler, Aluminum 2219-T87 Shield
EnginesRL10A-3-8 (uprated RL10)
PressurizationGHe for LOX; GH2 for LH2
ActivationElectrical Actuators
Gimbal Angle
RCSSupercritical LOX / LH2
ElectricalBatteries and electrical networks

The micrometeoroid and thermal shields are sized for a 14 day orbital mission. Their mass will have to be increased for a 50 day lunar mission, reducing the payload capacity.

The number of reuses the propulsion module is rated for are:

  • 50 uses in a one-way mission with delta V below 8,000 f/s
  • 20 uses in a one-way mission with delta V above 8,000 f/s
  • 20 GEO missions
  • 10 lunar landing missions
  • 50 lunar orbit missions

Medium propulsion module will easily fit in shuttle cargo bay, but if it is loaded with propellant and mated with an astrionics module, it is very close to the shuttle's mass carrying limit.

Large propulsion module will barely fit in space shuttle cargo bay, but if it is loaded with propellant it will exceed the shuttle's mass carrying limit.

Note how the RCS clusters are inset into the hull. If the clusters were on the hull surface, the propulsion module would not fit into the space shuttle cargo bay.

Drop Tanks
Propellant Mass7,620 kg18,053 kg28,123 kg
Inert Mass1,059 kg1,855 kg2,318 kg
Wet Mass8,680 kg19,908 kg30,441 kg
Mass Fraction0.8670.9060.924
Subsystems and Materials
StructureAluminum 2219-T87 (tanks), Aluminum 7075-T6 (load structure)
MicrometeoroidHexcel Filler, Aluminum 2219-T87 Shield
PressurizationGHe for LOX; GH2 for LH2
ElectricalBatteries and electrical networks
Feed SystemAluminum 7075-T6 lines

Drop tanks are basically propulsion modules with no engines and thrust frames. They are dropped at LEO or GEO orbit along with the payload.

Mass in kilograms
15 crew
2 day
3 crew
50 day
Crew Systems
(including crew)
Electrical Power5959
Misc. Equip.3636
36 m3
48 to 101 kPa
Crew Systems
Crewmembers, bunks, seats, food, medical, clothing, hygiene, EVA suits, suit PLSS backpacks.
Environment Control / Life Support System (EC/LSS)
Hardware, O2, N2, etc.
Electrical Power
Batteries, regulators, junction boxes, wires, cables, power distributer.
Communications and Data Management
TV, audio, antenna.
Displays, controls, wiring, lighting.
RCS, lines, instruments.
Miscellaneous Equipment
Manipulator arms display and controls, maintenance equipment, etc.
RCS propellant, fuel cell reactants, etc.
The crew module is rated for 10 uses in a lunar landing mission, and 100 uses for LEO or GEO missions.

The astrionics module is 4.3 meters across and 1.2 meters high. Mass varies from 857 kg to 1503 kg, depending on mission (see image below). The structure is octagonal with eight load bearing columns for transfer of the loads between the propulsion module and that portion of the Space Tug above the astrionics module. The systems listed on the bottom of the figure are mounted on the eight component mounting panels. These panels are accessible from both the inside and outside of the astrionics module. Radiator/louver doors provide thermal control as well as cover and protect the component mounting panels.

The number of reuses the astrionics module is rated for are:

  • 50 uses in a one-way mission with delta V below 8,000 f/s
  • 20 uses in a one-way mission with delta V above 8,000 f/s
  • 20 GEO missions
  • 10 lunar landing missions
  • 50 lunar orbit missions

Cargo modules are used to carry multiple low volume packages. If the cargo is in one large single piece (e.g., a satellite), it does not need no steeking cargo module. Instead it will be designed to withstand the mission environment, equipped with a payload adaptor, and attached bare naked to the payload adaptor on the nose of the space tug.

Cargo modules come in two types: Round and Doughnut. Round are mounted on the top of tug while doughnut are mounted at the bottom (encircling the rocket engine). Round are used for orbital missions and doughnut are used for lunar landing missions. This is because it is almost impossible to lower the round module's cargo 13+ meters down to the lunar surface. The doughnut cargo module will be about 1.5 meters from the lunar surface.

Cargo Modules
Payload Capacity9,072 kg4,536 kg
Volume36 m328 m3
Mass1,316 kg2,038 kg

Round module is one piece constrution with two exits.

Doughnut module is two half doughnut construction with two connecting hatches 180° apart plus exit hatch to surface. This is because the assembled doughnut is too big to fit in the space shuttle cargo bay, so it was split in two.

Both of them are:

Cargo modules are rated for 100 uses.

Round modules are basically hollow crew modules. They have a cargo capacity of 9,072 kg and a volume of 36 m3. The empty module has a mass of 1,316 kg. Only those minimum electrical, instrumentation, and environmental control systems as required to maintain the cargo are provided. The cargo modules will be provided with racks arid other bracketry to house the small packages which are envisioned for delivery as cargo to the space station or to low earth orbit. Packages are 0.3m × 0.3m × 0.6m. Liquids will be housed in the lower ellipsoidal section of the cargo module.

As previously mentioned, the doughnut module is for lunar landing missions. The idea is to get the module as close to the lunar surface as possible, to aid unloading (1.5 m from the lunar surface, instead of 13 m). This means it needs a doughnut hole in the middle to accommodate the rocket engine. Given the cargo requirements, the module will have a diameter too large to fit in the space shuttle's cargo bay. So the module is split into two section.

The doughnut module has a cargo capacity of 4,536 kg and 28 m3. The empty module mass is 2,038 kg, larger than the round module due to being split into two sections.

Kit Masses (kilograms)
Astrionics Module Plug-Ins0 to 420 (see figure)
Auxiliary Electrical Power (APK)0 to 1134
Environmental Protection System0 to 221
Clustering Adapter0 to 181
Docking Adaptor (DA) / Payload Adaptor91
Landing Legs (LL)876
Manipulator Arms (MA)91
RCS Booster280
Staging Adapter
and separation mechanism (SASM)


The basic astrionics module will be designed to accomplish low earth missions. To accomplish other missions, it will be necessary to provide additional astrionics capability. Plug-in astrionics will provide this capability. The kits will consist of additional (1) data management systems, (2) guidance, navigation and control systems, (3) command and control systems, (4) electrical power systems and (5) electrical networks.

The additional masses are shown in this figure.


For the lunar missions, the power requirements for the lunar experiments will exceed the capability of the standard power supply for the Tug. An auxiliary power kit will make up the deficit.

This kit will consist of a two kilowatt fuel cell, supporting tankage, lines, valves, fuel, etc.

For lunar missions, the power kit will be installed inside the doughnut cargo module, for easy access while on the lunar surface. For quiescent mode operations (mothballing) it will be installed in the center of the astrionics module.


Clustering adapters will be required for the large payload synchronous missions where more than one propulsion module is required for each stage.

Clustering adaptors connect propulsion modules side-by-side instead of one-on-top-of-another as do staging adapters.


Docking Adaptors and Payload Adaptors are basically the same unit. They are called "docking" for crewed tugs and "payload" for uncrewed tugs. As payload adaptors they are used to mount a monolithic playload (i.e., not suited for a cargo module) atop the astrionics or crew module.

Docking adaptors are rated for 100 uses.


Environmental protection kits are additional micrometeoroid shielding.

The basic Space Tug configuration will be designed to accomplish the low earth orbit and/or synchronous missions. For the accomplishment of longer duration missions, environmental protection kits will be provided which will provide further micrometeoroid protection capability.


These allow the tug to land on Luna without toppling over.

A space tug assembled for lunar landing missions is assumed to have a height of about 15.2 m. This height requires the landing legs to extend 9.1 m from the center of the tug to ensure stability.

A landing leg kit has four landing legs, 90° apart, of tubular construction. The legs would be fabricated from Aluminum 7075-T6, with shock absorber system consisting of liquid springs and landing discs to absorb shock and to act as leveling mechanisms. The upper attachment point for the landing legs is approximately 4.6m off the ground at the mid point of the LOX tank. The lower intersection point is approximately even with the lower part of the LOX tank.

Landing legs are rated for 10 uses.


The technical term is "waldoes". These are mounted on special fittings on the crew module. Displays and controls are installed in the crew control room.


For the lunar landing mission, the basic laser system will not provide the necessary identification of the landing terrain due to the dust and other visibility inhibiting environmental effects.

The radar kit will provide the visibility necessary for the accomplishment of the landing.


The basic Space Tug configuration is designed to operate in low earth or synchronous orbits.

An RCS booster kit will be required to provide additional maneuvering capability during some of the Space Tug's more complex missions (i.e., lunar landing).


This is to assemble a multi-stage vehicle.

For a "stage-and-one-half" vehicle, you use the SASM to mount a drop tank on top of the tug, to increase the available propellant. Usually the monolithic payload is mounted on top of the drop tank using a payload adaptor. When the tug reaches the specified orbit, both the payload (satellite) and the drop tank are dropped off.

For a full multistage vehicle, you use the SASM to mount an entire second vehicle on top of the first. When the lower stage exhausts its propellant, the SASM provides separation, and the upper stage ignites its rocket.

The staging adapter portion of the kit will consist of mating conical frustrums at the aft end of the upper module and at the forward end of the lower module. The upper stage conical frustum will fit into the lower stage conical frustum. The separation mechanism will consist of an electrical or hydraulic system to actuate pins to lock (or separate) the two modules. This kit will be primarily fabricated from Aluminum 7075-T6.

Sample Tugs

LEO Space Tugs
Single Stage
Single Stage
No Cargo
Single Stage
ItemWeights (kilograms)
Astrionics Module
(synchronious reusable
1st stage version)
Cargo Module1,316--1,316
Crew Module--4,2574,257
Docking Adaptor91----
Propulsion Module9,2609,2609,260
Stats (without cargo)
Wet Mass
(less cargo mass)
Dry Mass
(-7,620 propellant)
(less cargo mass)
Mass Ratio2.852.081.91
(Ve = 4,510 m/s)
4,720 m/s3,300 m/s2,920 m/s
Initial Accel
(F = 104,000 N)
8.9 m/s2
7.1 m/s2
6.5 m/s2
Stats (max cargo)
(Cargo)(≤ 9,072)--(≤ 9,072)
Wet Mass
(max cargo mass)
Dry Mass
(-7,620 propellant)
(max cargo mass)
Mass Ratio1.58--1.44
(Ve = 4,510 m/s)
2,060 m/s--1,610 m/s
Initial Accel
(F = 104,000 N)
5.0 m/s2
--4.2 m/s2

Lunar Landing Space Tugs
Single Stage
Single Stage
ItemWeights (kilograms)
Astrionics Module
(lunar landing version)
Crew Module--4,425
Propulsion Module20,72720,727
Cargo Module2,0382,038
Landing Legs1,2701,270
Payload Adaptor91--
Stats (without cargo)
Wet Mass
(less cargo mass)
Dry Mass
(-18,053 propellant)
(less cargo mass)
Mass Ratio4.312.52
(Ve = 4,510 m/s)
6,580 m/s4,170 m/s
Initial Accel
(F = 104,000 N)
4.4 m/s2
3.5 m/s2
Stats (max cargo)
(Cargo)(≤ 27,216)(≤ 4,536)
Wet Mass
(max cargo mass)
Dry Mass
(-18,053 propellant)
(max cargo mass)
Mass Ratio1.552.10
(Ve = 4,510 m/s)
1,980 m/s3,346 m/s
Initial Accel
(F = 104,000 N)
2.1 m/s2
(1.30 Lunar g)
3.0 m/s2
(1.86 Lunar g)

Space Tug: Dornier

Dornier Space Tug
Specific Impulse450 sec
Exhaust Velocity4,410 m/s
Core Module
Dry Mass
1,800 kg
Core Module
Wet Mass
16,500 kg
Aux Module
Dry Mass
900 kg
Aux Module
Wet Mass
7,500 kg
No Payload
Dry Mass Max
7,200 kg
Wet Mass Max
61,500 kg
Mass Ratio8.5
ΔV9,400 m/s

In 1970 the European Launcher Development Organisation (ELDO) awarded a contract to two European industrial consortia to study the feasibility and economic aspects of space tugs. Dornier Systems (a west German aerospace firm) produced this proposal.

The vital components were the Core Unit (propulsion system and basic propellant load) and the Auxiliary Units (a series of modules with additional propellant clustered around the core). The number of auxiliary units can be tailored to the delta V requirements for the mission (2 to 6 auxiliary units). If the mission required a large payload and/or large delta V, the auxiliary units could be staged (jettisoined when they became empty)

The core unit contained 14,700 kg of propellant, and each auxiliary unit had 6,600 kg of additional propellant.

The core unit alone with no auxiliary units can inject a payload of up to 2,000 kg into a geostationary orbit and return (8,800 m/s ΔV). The core unit can inject 6,100 kg of payload into geostationary orbit but will not be able to return (4,400 m/s ΔV). In between missions the core unit waits in a LEO parking orbit.

Payload to Geostationary Orbit
Aux ModulesTug ReusedTug Expended
0 (just Core)2,000 kg6,100 kg
26,700 kg11,600 kg
39,700 kg14,100 kg
412,900 kg17,600 kg
618,900 kg25,000 kg

Take the first trip: Tug with just the core (no auxiliary units) for 1,800 kg dry mass, 14,700 kg of propellant, and 2,000 kg payload. First leg of the trip is traveling from LEO to GEO, requiring 4,400 m/s ΔV.

R = eV / Ve)


ΔV = ship's total deltaV capability (m/s)
Ve = exhaust velocity of propulsion system (m/s)
M = mass of rocket with full propellant tanks (kg)
Me = mass of rocket with empty propellant tanks (kg)
R = ship's mass ratio
ex = antilog base e or inverse of natural logarithm of x, the "ex" key on your calculator

Plugging in our values:

R = eV / Ve)
R = e(4,400 / 4,410)
R = e(0.9977)
R = 2.7

We can use this mass ratio to calculate how much propellant was burnt. Mass ratio is

R = M / Me

Simple algebra gives us:

Me = M / R

Plugging in our values:

Me = M / R
Me = (1,800 {dry mass} + 14,700 {propellant} + 2,000{payload}) / 2.7
Me = (18,500) / 2.7
Me = 6,850 kg

So the tug arrives at GEO with a total mass of 6,850 kg. We know that 1,800 kg is dry mass and 2,000 kg is payload. By subracting we see that there is 3,050 kg of propellant left.

In GEO, the 2,000 kg payload is delivered, and is no long part of the tug's total mass.

It is time for the second leg of the trip. Now the tug has a wet mass of 1,800 + 3,050 = 4,850 kg. It has a mass ratio of 4,850 / 1,800 = 2.69. How much ΔV does it have?

ΔV = Ve * ln[R]
ΔV = 4,410 * ln[2.69]
ΔV = 4,410 * 0.99
ΔV = 4,370 m/s

4,370 m/s is close enough for government work to the 4,400 ΔV required to travel from GEO back to the LEO parking orbit.

Space Tug: Grumman

This is from a report Manned Orbital Transfer Vehicle (MOTV) by Grumman Aerospace, Vol 1, Vol 2, Vol 2b, Vol 3, Vol 4, Vol 5, and Vol 6.

EREmergency Repair
OPOperate Large Space System
PPassenger Transport
DRDebris Removal
UCUnmanned Cargo

The MOTV was intended for a series of orbital missions, listed in the table. They range from short-duration/small-crew/low-mission-hardware-mass to long-duration/large-crew/heavy-mission-hardware-mass. Orbits range from GEO to 12hr/63° elliptic to deep space (400,000 nautical miles circular).

The crew capsule had several configurations: two or three crew, and basic/functional minimum. Basic has the luxury of tiny privacy quarters for each crew. Functional minimum on the other hand is dreadfully spartan, with no privacy whatsoever.

Basic has 4 m3 per crew, while functional minimum has only 3 m3.

Why does "functional minimum exist? To reduce mass, of course. Every gram counts. By removing the privacy quarters by combining work and sleep stations you can shorten the 3-crew capsule by an entire meter, and save 440 kilograms of dry mass. The 2-crew capsule shortens by 1.5 meters and saves 805 kilograms. The reductions are figured from the length and mass of the 3-crew basic capsule.

As it turns out, most of the missions can be performed by two crew.

The propulsion system is contained in a central core module aft of the crew capsule. It has a capacity of 17,500 kg of LH2/LOX fuel. It is equipped with two RLIO cat IIB type engines with a specific impulse of 458 seconds. Each engine delivers 67,000 Newtons and can be gimbaled over ±20°. The wide gimbal range is due to the huge shift in the spacecraft's center of gravity when it jettisons a drop tank.

In addition the core has four reaction control system (RCS) modules with 700 N of thrust each. They have a specific impulse of 230 seconds and are fueled with 2,600 kg of hydrazine. The core's intertank skirt has assorted other equipment mounted: three fuel cells and reactant, 4.53 m3 of heat radiator, and an optional 12 kWe solar array.

The core can have up to four drop tanks mounted, each containing 27,270 kg of fuel. Each has a tiny deorbit engine to send expended tanks to burn up in Terra's atmosphere. All tanks (including the core tank) will have a boiloff rate not to exceed 19 kg/day per tank. The heat from Sol makes cryogenic fuels boil, the vapor has to be vented or the tanks explode. Use it or lose it.

Space Tug: Johnson Space Center

This is from a Johnson Space Center report Initial technical environmental, and economic evaluation of space solar power concepts. Volume 2: Detailed report. The tug design will be used to assist construction of a gigantic solar power station (SPS). The spacecraft is called a Personnel Orbital Transfer Vehicle (POTV) or a Cargo Orbital Transfer Vehicle (COTV), depending upon whether a personnel or cargo module is docked to the crew module. OTV is a fancy word for "space tug".


The basic mission will be a trip from Low Earth Orbit (LEO, 200 to 500 km altitude from Terra's surface) to Geosynchronous Orbit (GEO, 42,164 km from Terra's center) then back to LEO. Transit time from LEO to GEO will be from 8 to 9 hours.

There were three main missions proposed for the OTV:

  • Geosynchronous Sortie A 4 crew mission spending a week on geosynchronous satellite maintenance, with transfers of up to 15° longitude between each satellite visit. Only the crew module is required, added to the propulsion stages.
  • Crew Rotation The contruction and operational crews on the solar power stations will be rotated at least every six months due to allowable radiation dose. A crew module and a personnel module are required, added to the propulsion stages.
  • Station Resupply Replenish the GEO station consumable, supplies, and equipment necessary for 180 days.

For some missions the spacecraft is configured with two stages. The initial burn is to leave LEO and enter the GEO transfer orbit. When 85% of the required delta V has been generated, staging occurres. But the first stage is not discarded. Upon staging, the first stage still has some propellant left. The stage uses the remaining propellant to return to LEO under automatic pilot. The weird 85% staging point is to allow both first and second stages to have identical propellant tanks and delta V. They do have a different number of engines, so the first stage has a higher acceleration.


The modular design has three components: propulsion stages, crew modules, and resupply modules. All modules are sized so they will fit in a space shuttle payload bay (maximum diameter 4.42 meters, maximum length).

Propulsion Module

This concept consists of two nearly identical stages used in tandem that provide the required mission delta-V. The first of these stages is unmanned and is used to provide approximately 85% of the delta-V required for departure from LEO on a crew rotation flight. Stage 2 provides the remainder of the boost delta-V as well as the impulse required for injection into the destination orbit and for the return to LEO.

Following separation from stage 2, stage 1 is returned unmanned to LEO. Splitting the delta-V as described above results in the stages having identical propellant capacities. Subsystems design approaches are also common between the stages including the size of the main engine. Taken individually, each of these stages is similar to the single stage concept in terms of subsystem selection and location.

At the forward end of the stage 1 are two types of docking provisions. One of these systems isused to connect with stage 2 while the center mounted unit is an international type design that allows docking with systems other than stage 2; examples of these other systems include a tanker for independent servicing or a space station ifbasing isrequired while awaiting the return of stage 2.

Stage 2 docking provisions are required at both the forward and aft ends. The forward docking station uses an international type unit for attaching payloads. In addition, this unit accommodates tankers or is used to connect the stage to a space station for basing. The aft docking provisions are used in conjunction with those in the forward section of stage 1 and enable the stages to be connected. Provisions are also included on stage 2 to allow servicing of stage 1 when the two stages are connected, and the tanker is docked at the forward end of stage 2.

The OTV start burn mass is 123 metric tons (I think this includes one crew module) with a main propellant loading of 106 metric tons. Each stage is 4.42 meters in diameter and 17.06 meters in length (stage 2 length is 15.61 meters with engine nozzles retracted) and are Shuttle compatible and require on-orbit fueling and refueling. The first stage employes four 66,720 newtons thrust engines and the second stage employs two of the same engines.

Crew Module

Personnel Module

Resupply Module


The following designs have a very similar appearance to the JSC space tug.


     So four days ago or there abouts, I put a poll up on Google+ with a selection of spacecraft I was thinking about making isometric cutaways of. The frontrunner is the Intra-Fleet Space Tug. That means, RocketFans, that we’ve got ourselves a project!

     The context for this particular spacecraft, like the Cygnus capsule I also put in the poll, is the care and feeding of the distributed-network fortification that is a deployed UN Constellation in the Conjunctionsetting. In summary, the fleet’s configuration is a tetrahedron in space with a single control ship at the apex, patrol craft making up the other three vertices, and edges three hundred thousand kilometers long. Just how do you supply ships that are as far out as the Moon is from LEO?

     In the article about how fleets work, I stated that the crews on the patrol craft could be swapped out by ferrying fresh people out via the Cygnus. While this would certainly work for crew transfers, you’d also have to detail additional craft for cargo transfers, of consumables and (if armed with rail guns) ammunition. As versatile as the Cygnus is, it cannot not re-supply that most important consumable resource in terms of tactical movement, propellant.
     To put the problem into perspective, a Cygnus stack is a rough cylinder 4.5 meters in diameter and about ten meters long. The propellant tanks on a Type A Patrol Cutter are 8 meters in diameter and total thirty meters long. And there are two stacks. Clearly, to refuel a patrol ship, we need a real tanker.
     I’ve said it before RocketFans, and I’ll surely say it again: Atomic Rockets is an invaluable resource for the budding rocketeer. The “Realistic Designs” sections are a veritable clearinghouse of old NASA designs that were pretty good but never got a decent budget. These oldies make for a great library of inspiration when designing any spacecraft that is meant to work with real-world physics. For our Intra-Fleet Tug, I was inspired by the Johnson Space Center’sTug study, who’s image I used in the Poll. This beauty is a two-stage ferry to get from LEO to GEO where NASA was going to build a solar power station.
     Anyway, a light-second is good deal further than the LEO/ GEO distance, right? In kilometers, yes, but in Delta-V, not even close. It takes a whopping 4.33 km/s to go from LEO to GEO, but a paltry 2.74 km/s to get from LEO to Lunar orbit…a little over a light-second away.
     Gravity is funny like that.
     So our tug only needs about 75% the range of the JSC version. Since that design was staged and the first staged carried the spacecraft 85% of the way to GEO we could just lop of Stage I and call it a day. But where’s the fun in that?
     The problem with just ripping of the JSC design is that it isn’t a tanker. We need to be able to deliver a large amount of propellant, so we’re going to need a large spacecraft. Something that could haul at least a quarter or half of the Delta-V needed to completely refuel a Patrol craft. What follows is an experiment: I’m thinking of just taking an entire rocket stack from a Patrol craft and slapping a command module on the front for our Tug. Let’s see how that would work, shall we?
     First of all, we need to dust off our rocketry equations so we know what variables we need to consider. We’re going to need to know the Tugs dry mass, wet mass, and engine details such as propellant flow, thrust, and exhaust velocity. Since we’re using the dimensions of the propellant tanks from the Class A Patrol Craft, and possibly one of its main engines, that gives us a great place to start. In fact, lets crunch the numbers for the Patrol rocket’s main engine and an alternate, say something along the lines of the J-2 from the Saturn V’s SIV-B stage.
     First, let’s establish the tonnage for the Tug without it’s engines. We’ll want a decent sized crew module, because gaming, and also so we can have cadets aboard during all flights. In Conjunction, like in Heinlein’s Space Cadet every UN convoy and spacecraft has a group of peacekeeper candidates learning how to work in space by working in space. I see an actual crew of about four: a Flight Commander (F-Com), Guidance Procedures Officer (GPO), Maintenance, Mechanical Arms, and Crew Systems Officer (MACS), and a Payload Officer (Payload). Add as many again of Candy-Cruisers, and you’ve got eight people in the command module. That’s a bit crowded for a Tug, but we can use hot-bunking with to limit the sleeping berths to four. The CM must also have at least a pair of robotic arms, and a sturdy docking module for carrying passenger capsules and cargo pods. Behind the CM will sit a flared-out service module, with avionics, life support, and computer systems. The SM will be mated to a 30 × 10 meter saddle truss, which is what will actually hold our propellant tanks and provide a mount for the rocket stack. But in addition to all of that, we will also need a passenger module and cargo pods, so we need to know the mass for all of those as well.
     Here’s how it breaks down:
SystemMass (kg)
Command Module12,671
Service Module3,000
Saddle Truss24,119
Propellant tanks24,119
Passenger Module7,540
Crew Average Mass2,400

     I arrived at some of these number dubiously, so take them with a grain of salt. The CM mass is from the Trans Hab Calculator on the AR website, the SM is from the JSC Tug, the truss is simply repeating the mass of the propellant tanks, since I couldn’t find any reliable numbers for that. The Passenger module is also from the JSC tug, while the consumables and cargo masses are calculated for the tugs trip out and back, as well as 30 days of supplies for the 20-person crew of a Patrol craft. And of course, we can’t forget the mass of the crew and passengers themselves, plus what ever possessions they can carry inside their regulation 100 kg mass-limit. Finally, the propellant tank mass is 6% of the propellant mass, as per Dr. Rob Zubrin, and the propellant masses came from the Useful Tables appendix from Atomic Rockets. But the most important thing to remember is that we have no engine yet.
     The Class A Patrol craft uses an easy to maintain in freefall analog of the Space Shuttle Main Engine (SSME) so I could simply steal copy the vital statistics. Engine List on Atomic Rockets has these available. Just below that entry is the stats for the Tug engine we will also use. These are not exactly the J-2 stats, but they are for a NASA tug, and they have the information I need to calculate with, whereas sources on the J-2 did not.
     What we want to know is, assuming a 100-hour flight time, is how much propellant will be left in the big tanks at the end? We need to have spend no more than 1/3 of our propellant mass in transit. That way, we can refuel with another third (plus a bit extra) and use the remaining less-than-a-third to take our much less massive tug home.
     This means math. So, so much math.
     Well, not so much, perhaps. We know all the vital statistics for our engines, our mass numbers, our Delta-V budget, and our distances. By establishing an arbitrary travel time of 100 hours, we also provided a much-needed value for equations, and more important, the mass of needed consumables.
     An Intra-Fleet Tug that uses a “F-2b” SSME-analog will have a wet mass of 846,901 kg, or 847 tons. Let’s see if we can get from point A to B while only burning through 125,664 kg of propellant.
     Simple, right?
     If only using 125.6 tons of our propellant, we will be operating with a mass ratio of only 1.8 By using the Delta-V equation of Delta-V = Exhaust Velocity × ln(Mass Ratio). This results in a Delta-V of 2621.96 m/s, or 2.62 km/s. We need 2.74 km/s to get to our destination, so it’s close, but no cigar.
     If we attempt the same thing with our J-2 analog, we have a wet mass of 845,512 kg. This gives us a mass ratio of 1.8 again. However, the exhaust velocity is 4159.4 (I had to calculate it using the specific impulse, but that’s why we have algerbra in the first place). With the mass ratio and a lower exhaust velocity, the Delta-V is 2.45 km/s. Both engines are pretty comparable, but neither will get us out a light second and back.
     Or will they?
     The moon averages 384,000 kilometers from Earth. A light-second is only 300,000 kilometers. We actually have less distance to travel, and hopefully less Delta-V, than the 2.74 km/s we’ve been using. Possibly a lot less.
     I forgot that moving around a fleet formation like this is not remotely the same as moving around orbits. Moving from LEO to Luna is a Hohmann trajectory, which is a change between orbits from around one body moving at one speed to another body moving at a very different speed. When deployed, our constellation is all moving at a constant speed along a constant orbit/vector. This means that all spacecraft in the formation are at rest relative to one another. So we need to go from a starting velocity of (relatively) zero to a certain speed, coast, flip, and then decelerate back to zero. This is just a simple physics problem.
     This is also where our arbitrary 100-hour travel time comes in. With time and distance known, as well as acceleration (Thanks to the engine stats) we can solve for velocity and begin to figure out what we need to know.
     Solving the displacement equation gives us an average velocity of 833.333 m/s to travel a light-second in four days and change. This means we need a final velocity of 1666.666 m/s. Our SSME engine will take only 721 seconds to boost our monster tug to speed, and the same to decelerate at the other end. Now for the biggie – mileage. By which I mean, just how much propellant did we use up in those 1442 seconds?
     Turns out that’s an easy one, because we know the mass flow. A single SSME tosses 409 kilos out the back every second, so our Tug will have to burn 589,778 kg. This is more than the entire wet mass of the tug, so say nothing of the “one-third” we wanted to get by with.
     As for the J-2, we need to re-do our acceleration calculation so we can figure our burn duration. Unfortunately, with a burn duration of 1282 seconds one way, the performance is even worse.
     What went wrong? This tug has half the power or a patrol rocket – it should have at least comparable performance.

     Having gone back over my notes I discovered my problem, and it’s an embarrassing one. The Class A Patrol Craft I just mentioned, the one that’s over twice as large as this tug? It has a dead weight tonnage of 70 tons. That’s it. The Tug has a dry mass of 466 tons. Well, there’s our problem!
     I designed the Patrol Craft to take into account the likely progression of materials science toward ever lighter and stronger materials. It was built out something that has the same strength of titanium, and half the mass. Add to that it’s outer skin is mostly carbon and aerogel – literally the least dense substance there is – and its easy to see that simply cribbing numbers from a design made when aluminum was the lightest thing you could build spacecraft of is a problem.
     Let’s try this again shall we?
SystemMass (kg)
Total Structure Mass24,119
Crew Average Mass2,400
With J-2409,544
With SSME409,337

     I not only went back and recalculated the structure mass using 22nd century materials, I also hand-calculated the mass of the consumables and cargo, using NASA rations. Much better results. With these stats, the Tug can pull 4.43 m/s, and only has to burn for a total of 376, instead of 1442. This means we only burn 141,514 kg of propellant. With less thrust and more mass, I don’t feel a need to calculate for the J-2. 141.5 tons of propellant is 37% of our propellant mass. For the return trip, we’ll need less propellant, say, 25%? The Tug would only mass 126 at that propellant fraction, and accelerate at a whopping 14.4 m/s, or 1.4 gs. It will only have to accelerate for 115 seconds and burn only 43 tons of propellant, while carrying 96 tons. This is over a 100% reserve, enough that we could add another 20 tons or so to the 124 tons our Tug is pumping into the Patrol craft.
     So, there you have it, RocketFans, a glimpse into the hair-tearing-out, thankless job of designing a realistic spacecraft. I’m glad I just have to make these look good on paper. But the important part is, I can now draw a spacecraft with all the particulars I wanted to, and it will not only look realistic, it will be realistic. It’s capabilities and limitation will suggest numerous plot points and story ideas, and I can be assured that each and every one of them will pass the litmus test of plausibility, because I did the math up front.

Space Tug: Lockheed

Details are sparse on this 1963 design. Click on blueprints for larger image. Blueprint is written in Italian but it has been translated for the website by Alberto Bursi. The engines are around the waist, on swivels. The designers also appear to have a flippant attitude towards maintaining a sense of up and down. If the pilot turns his head he will see his copilot's feet.

Space Tug: NASA

RocketCat sez

This is a spiffy design for giant robot fans. Those titanic mecha arms will immediately grab the attention anybody who adores Jaegers.

This is a 1972 era NASA concept for a space tug. It is a modular design. It is an altered version of an old Boeing space tug design. One way to tell the difference is that the Boeing tug's crew and cargo modules were spherical, while the NASA tug's modules were cylindrical.

The information is from a North American Rockwell Corp. document entitled Pre-phase A Study for an Analysis of a Reusable Space Tug. Volume 4 - Spacecraft Concepts and Systems Design Final Report. The document is solid gold, but be warned it is 640 megs in size and over 600 pages long. It has tons of blueprints.

Also useful is Pre-phase A Study for a Analysis of a Reusable Space Tug. Volume 5 - Subsystems Final Report.

For purposes of analysis, they created designs for three different missions:

Mission TypeNumber of CrewMission DurationSupply
Space (LEO)67 days42 crew-days
Lunar Stay428 days112 crew-days
Rescue121 day12 crew-days

In addition, they mentioned a two-crew "mission" which boiled down to "use a crew module as a control room." You see this often as a crew module perched on top of a Reusable Nuclear Shuttle.

For what it is worth for the Lunar Stay mission, the Apollo Lunar Module descent module used about 2,500 m/s of delta V for the descent and landing, and the ascent module used about 2,220 m/s delta V for the return to orbit. About 4,720 m/s delta V total.

Minimum acceleration for lunar landing/lift-off is about 2.43 m/s2, 2.10 m/s2 in a pinch. The Apollo Lunar Module ascent module had an acceleration of 3.4 m/s2 (2.2 lunar gees)

Below 1.52 m/s2 (lunar surface gravity) you will crash while landing, and at take-off you will just vibrate on the lunar surface while the rocket blast blows the regolith around.

The tug was mandated to be cylindrical. First off they tried to find the optimum diameter.

They did an analysis of crew modules which were 3.6, 4.5, and 6.7 meters in diameter, because those are 12, 15, and 22 feet respectively. 4.5 m is compatible with the Space Shuttle cargo bay. 6.7 m is compatible with the Saturn booster. 3.6 m was a smaller sized picked arbitrarily just to see how it worked.

3.6 m was far too cramped, unless they made it two decks tall. 6.7 m was too big to be economic, unless they stuck the contents of other modules into the crew module (which kind of defeats the entire "modularization" idea). By "too big" they mean it gave the crew space they didn't need, which still costs payload mass for the bulkheads and pressurization. 6.7 m is also too big to fit in the Shuttle cargo bay.

4.5 m was just right.

Modules and Kits

The modular components of the space tug include:

Propulsion Module (PM)
The rocket engine
  • Main engine
  • Main propellant tank
  • Auxiliary propellant supply
  • Docking provisions
  • Two S-band antenna
  • Landing sensors (if Lunar landing guidance and navigation sensors kit is installed)
  • Can attach landing gear kit, but usually better to attach to crew module
  • Holds heat radiators from intelligence module
Tank Set (TS)
Propellant tanks. Basically a Propulsion module with no engines and no docking provisions.
Crew Module (CM)

The habitat module the crew lives and works in. This module is optional. The tug can be unmanned, pre-programmed or under remote control.

Two man for a control/working module. Four man for a lunar base module. Six man for crew transport. Twelve slot for emergency evaculation module.

For lunar landers it makes sense to have the crew module on the bottom of the stack, with the landing gear kit attached.

  • Crew provisions
  • Environmental control / Life Support System
  • Environmental control heat radiators
  • Manual guidance, navigation, and control
  • Displays (guidance and navigation I/O)
  • Power distribution
  • Docking interface
Intelligence Module (IM)
The tug's brain and nervous system.
  • reaction control system (auxiliary propulsion)
  • Auxiliary propellant supply
  • Electrical power generation
  • Heat radiators (mounted on propulsion module)
  • Guidance, navigation, and control
  • Automatic flight programming
  • Communications
  • System C/O, monitoring and control
  • Data management
CArgo Module (CAM)
Various sized cargo holds to hold, you know, cargo. Often used to transport supplies to space stations and bases. Some CAM are split long-ways (hemipods) in halves or quarters, and are hung on either side of the propulsion moodule like saddle-bags for a low center of gravity (so the lunar lander isn't quite so tippy when it lands).
Payload (PL)
Special and general purpose cargo which is not carried in cargo modules. Satellites to be placed, experiments, etc.
  • Docking adapter kit. Provides capability for standard neuter docking to Apollo probe or drogue
  • Guidance and navigation docking sensor assembly. Attached to foremost surface of tug and payload for active rendezvous and docking capability. Mostly TV camera and contact sensor. Former for maneuvering, latter to signal that the docking clamps can now be activated.
  • Manipulators (waldo arms) for assembly, maintenance, repair, satellite retrieval, and cargo handling (either bolted to a module or in a submodule)
  • CM manipulator interface assembly. Human-usable controls for the manipulators, placed inside the crew module.
  • Neuter docking adapters, for either end of any module
  • Extra provisions for manned flight
  • Extra subsystems for manned flight (lunar landing)
  • Landing gear (lunar landing). Bottom mounted landing legs. These are generally fixed because it turns out that stowage and deployment of folded gear constitutes a formidable problem. As a rule of thumb you want the gear to be long enough so that at touchdown the main propulsion engine nozzles are at least two exit diameters above the lunar surface.
  • Lunar landing guidance and navigation sensors. Landing sensor system added to the propulsion module with readouts inside the crew module.
  • Extra heat radiators
  • Lunar landing heat radiators. Standard radiators are mounted on the hull. Unfortunately while landed, thermal energy from the sun is reflected from the lunar surface and interferes with the hull radiators. So separate deployable radiators are required, facing the sky. Generally top-mounted. About 28 m2 in two or four panels.
  • Cable elevator to lower crew to lunar surface. Used if crew module is on the top
  • Lunar landing antenna. Long-range extensible parabolic antenna (1.8 m diameter) either tug-mounted or portable. Used for additional communication capability.
  • Electrical Power Kit (for IM) for manned missions or payload support. Includes additional heat radiators.
  • Aerobraking Kit to allow aerobrake assisted Terra reentry and landing.

In an earlier design, the intelligence module had the rocket engines mounted in the center, and the IM was placed underneath a Tank Set (containing internally both liquid oxygen (LOX) and liquid hydrogen (LH2) tanks). Sometimes there was a dedicated LOX Tank Set and a dedicated LH2 Tank Set.

Propulsion (PM)
The rocket engine
  • Main propulsion
  • Auxiliary propellant supply
  • Two S-band antenna
  • Landing sensors
  • Can attach landing gear kit, but usually better to attach to crew module
  • Holds heat radiators from intelligence module

4.5m diameter, height depends upon amount of propellant contained. With no propellant the mass is approximately 3,580 kilograms. The report studied concepts with 36,287 kg of propellant (LOX+LH2) and 28,576 kg of propellant.

In all designs the engines are chemical LOX/LH2 engines. The example design had an exhaust velocity of around 4,550 m/s and a specific impulse of 464 sec.

The 4.5m lander design had four swing-out engines each with a thrust of 44,482 Newtons (177,928 N total thrust).

It burned at a oxygen/fuel (O/F) ratio of 6 to 1 instead of the theoretical maximum (stoichiometric) of 8:1 (they used 6:1 because of liquid hydrogen's annoyingly low density).

The propellant mass was 36,287 kg or 31,103 kg LOX and 5,184 kg LH2. The LOX tank had a volume of 31.1 cubic meters and the LH2 tank was 93.4m3.

The PM had a diameter of 4.5m and a height of 13.1m.

Crew (CM)

The habitat module the crew lives and works in. This module is optional. The tug can be unmanned, pre-programmed or under remote control.

Two man for a control/working module. Four man for a lunar base module. Six man for crew transport. Twelve slot for emergency evaculation module.

For lunar landers it makes sense to have the crew module on the bottom of the stack, with the landing gear kit attached.

  • Crew provisions
  • Environmental control / Life Support System
  • Environmental control heat radiators
  • Manual guidance, navigation, and control
  • Displays (guidance and navigation I/O)
  • Power distribution
  • Docking interface

4.5m diameter and 2.4m tall. About 3,960 kg for the space mission (6 crew for 7 days) and 5,613 kg for the lunar landing mission (4 crew for 28 days).

They did an analysis of crew modules which were 3.6, 4.5, and 6.7 meters in diameter (because those are 12, 15, and 22 feet respectively. 15 feet is compatible with the Space Shuttle cargo bay. 22 feet is compatible with the Saturn booster.). 3.6 m was far too cramped, unless they made it two decks tall. 6.7 m was too big to be economic, unless they stuck the contents of other modules into the crew module (which kind of defeats the entire "modularization" idea).

4.5 m was just right.

For the 4.5m diameter 2.4m tall crew module, they determined the following mass breakdown:

4.5m dia. Crew Module Mass Schedule
2.0Body Structure1,150 kg1,150 kg
3.0Induced Envir Prot154 kg154 kg
4.0Lnch Recov & Dkg218 kg218 kg
8.0Power Conv & Distr23 kg23 kg
9.0Guidance & Navigation86 kg95 kg
11.0Communication136 kg136 kg
12.0Environmental Control86 kg89 kg
13.0Growth Allowance265 kg274 kg
14.0Personnel Provisions743 kg832 kg
15.0Crew Sta Contrl & Pan70 kg70 kg
SUBTOTALS (DRY WEIGHT)2,933 kg3,038 kg
17.0Personnel (90.7 kg each)544 kg
(6 crew)
363 kg
(4 crew)
18.0Cargo, food, etc.220 kg735 kg
19.0Ordnance N2 and TK9 kg9 kg
20.0Ballast EVA-163 kg
SUBTOTALS (INERT WEIGHT)3,706 kg4,308 kg
EPS O2234 kg1,182 kg
EPS H220 kg123 kg
TOTALS (GROSS WEIGHT)3,960 kg5,613 kg
2.0 Body Structure
Body-structure weight: The weight of the basic and secondary load-carrying members, exclusive of the nonstructural panels used for induced environmental-protection systems.
3.0 Induced Envir Prot
Induced environment protection system. Generally the heat shield on a reentry vehicle.
4.0 Lnch Recov & Dkg
Apparently "Launch, recovery, and docking", so it probably referring to the docking port.
8.0 Power Conv & Distr
Apparently "Power conversion and distribution", so it is probably referring to the electrical power system.
13.0 Growth Allowance
These weight breakowns are typically estimates, submitted when bidding for a NASA contract. The Growth Allowance is insurance, in case one or more of the weight estimates for a subsystem is too low. Since every gram counts, NASA is quite intransigent about weight estimates. The growth allowance gives the contractor some wiggle room before they are in violation of the contract.
15.0 Crew Sta Contrl & Pan
Apparently "Crew stations, controls, and panels", so it is probably referring to the flight control stations.
Ordnance N2 and TK
Apparently "Ordinance, compressed nitrogen and tankage", used for atmosphere or to pressurize the fuel cell tanks.
Ballast EVA
Probably EVA suit(s) or the consumables reserved for EVA activity. Current day EVA suits are about 53 kg each.
Electrical Power Subsystem oxygen, probably Fuel Cell O2 fuel
Electrical Power Subsystem hydrogen, probably Fuel Cell H2 fuel
Dry Weight
The sum of codes 1 through 16. In this usage, it means the mass of the spacecraft/module with no propellant, payload, crew, or consumables.
Inert Weight
The sum of codes 1 through 21. In this usage, it means the mass of the spacecraft/module with everything (payload, crew, consumables) BUT no propellant. Which is the exact opposite terminology that I am used to.
Gross Weight
The sum of codes 1 through 27. The mass of the spacecraft fully loaded with propellant and everything. The "wet mass". Since the crew module has no propulsion it technically does not have propellant. It appears they are including the fuel cell fuel as "propellant."

For a Space mission the Space Tug would probably have the crew module mounted on top of the spacecraft stack. There would be a docking port on the top, along with roof windows to assist the pilot with the rendezvous.

For a Lunar-Stay mission, the tug would probably have the crew module mounted on the the bottom of the spacecraft stack. The bottom position would give the pilot a much better view of the landing as opposed to being perched on top of tall spacecraft with no view of what the landing gear (L.G.) was landing on. The landing gear would also be attached to the strong crew module, instead of the aluminum foil thin walls of the propulsion module. The entire spacecraft would have a lower center of gravity, always a plus when trying to land. Once landed, the airlock door will exit only a meter or so above the surface, instead of tens of meters.

The drawback of course is the crew will have a ring-side seat if the space tug crashes. A short view, only until the mass of the rest of the spacecraft (on top of the crew module) accordions it flat like a beer can in a trash compactor. The exhaust nozzles of the propulsion module would be on swing-out engines aimed to fire off the the side instead of hosing the crew module with flaming death. This makes the engine more complex (more points of failure) with a bigger mass penalty.

The crew module is an aluminum honeycomb pressure vessel with a centrally located air lock. There is also an emergency egress hatch in the side wall of 0.91 meters in diameter. The module has a pressurized volume of 31.85 cubic meters.

The control station is a stand-up station similar to the Apollo lunar module. For docking there will be windows for the pilot locate on the roof. For landing there will be angled windows located on the sidewall, again much like the lunar module.

Workstations are chairs with tables. Above the workstation benches are storage cabinets for food preperation, environmental control equipment, and scientific equipment.

Fold-up bunks are provided on the side walls. When folded up, the crew module can be used in rescue mode, with space for twelve persons. Using fold up bunks is far superior to having a totally different design for a rescue crew module.

The airlock is 1.5 meters in diameter with a pressurized volume of 3.78 cubic meters.

Below are the blueprint for the Space Mission (six crew) and Lunar-Stay Mission (four crew) version. There really is not much difference between the two. Basically the Lunar-Stay Mission version has the extra two bunks removed and replaced by additional workstations.

The blueprints show a passive docking ring on the aft end of the crew module. This is the configuration when the crew module is located at the bottom of the spacecraft stack. When the crew module is located at the top, the docking ring will move to the roof, and may be replaced by an active neuter docking system.

Intelligence (IM)
The tug's brain and nervous system.
  • reaction control system (auxiliary propulsion)
  • Auxiliary propellant supply
  • Electrical power generation
  • Heat radiators (mounted on propulsion module)
  • Guidance, navigation, and control
  • Automatic flight programming
  • Communications
  • System C/O, monitoring and control
  • Data management

The module is a torus with an inner diameter of 2.03m and an outer diameter of 4.57m diameter. It is 0.9m tall. The center hole is for airlocks, propellant pipes, rocket engines, docking ports or whatever.

The module has four reaction control system pods. Each pod has four jets: two aft, one forward, one on each side. There are two jets aft so the RCS can also act as auxiliary propulsion. Each pod can retract into the IM to keep the module within the 4.57m diameter limit of the Shuttle cargo bay.

IM for unmanned tug 1,560 kilograms. IM for manned Space mission 1,703 kg. IM for manned Lunar landing mission 1,973 kg.


Various sized cargo holds. Some are split long-ways (hemipods) in halves or quarters, and are hung on either side of the propulsion moodule like saddle-bags for a low center of gravity.

In North American Rockwell's study on constructing a lunar base, they saw a need for a sort of Lunar tractor vehicle with a tall hoist. Lunar base modules could be transported down as a unit by the tug, then unloaded and moved into place by the tractor. Base modules are 9.2 meters long, 4.6 meters in diameter, and have a dry mass of 4,500 kilograms. They have docking ports on each end.



Waldo arms for repair, satellite retrieval, and cargo handling. They are either bolted to a module or incorporated into a special manipulator submodule.

Landing Gear

This allows the space tug to land on the Lunar surface.

These are generally fixed because it turns out that stowage and deployment of folded gear constitutes a formidable problem. As a rule of thumb you want the gear to be long enough so that at touchdown the main propulsion engine nozzles are at least two exit diameters from the lunar surface.

Since landing gear have appreciable mass under acceleration and exert stress when supporting the tug on the lunar surface, they should be attached to load-bearing structures. Which is usually not the propulsion module, who have walls made out of aluminum foil. Many lunar landing tug designs have the crew module on the bottom, so the landing gear is attached mostly to the load bearing CM frame, and only partially to the PM.

Cable Elevator

Used to lower crew to lunar surface if crew module is mounted on the top.

Long-range Extensible Antenna

For lunar missions larger antennae may be required for communication with Terra. These are about 1.8 m diameter.

Lunar Landing Heat Radiator

Standard radiators are mounted on the hull. Unfortunately while landed, thermal energy from the sun is reflected from the lunar surface and interferes with the hull radiators. So separate deployable radiators are required, facing the sky. About 28 m2 in two or four panels.

Sample Tugs

The study looked into ten different tug configurations, later expanding it to eleven. They are all assumed to have four LH2/LOX chemical engines with an exhaust velocity of 4,550 m/s and a combined thrust of 177,928 Newtons

They eventually narrowed it down to three configurations: Concept 1, Concept 5, and Concept 11. The main difference was how much propellant they carried. The secondary difference is the staging. Concept 1 is a single stage. Concept 5 is two stage, with both stages recoverable. Concept 11 is one-and-one-half stage. That is, it has a small propulsion module with a small propellant tank joined with a huge disposable tank set.

Space Tug Concepts
C136,300 kgSingle Stage
C516,300 kgMulti-Stage
C1121,800 kgOne-and-One-Half Stage
Tug Specifications
Space (LEO) MissionLunar Mission
NASA mode A
Lunar Mission
NASA mode B
Intel Mod 11,500kg1,500kg1,720kg1,720kg
Intel Mod 2-1,500kg--
Crew Mod--4,170kg4,170kg
Prop Mod 13,580kg1,860kg3,580kg1,860kg
Prop Mod 2-1,860kg-1,860kg
Landing G--2,720kg1,410kg
Total Inert9,600kg11,250kg16,740kg15,560kg
Aux Con270kg540kg1,360kg1,360kg
Wet Mass46,400kg44,900kg43,730kg40,960kg
Start Accel3.8m/s24.0m/s24.1m/s24.3m/s2
Mass Ratio4.84.0 2.62.6
ΔV7,160m/s6,300m/s 4,270m/s4,420m/s
  • Staging
    • A1 = Single-stage, recovered
    • B3 = Two-stage, both recovered
    • C1 = Two propulsion modules, one intelligence module, parallel operation
    • D1 = One propulsion module, one tank set, one intelligence module; operating as a single stage
    • E1 =
    • E4 =
  • Intel Mod 1 = intelligence module 1 mass
  • Intel Mod 2 = intelligence module 2 mass (if any)
  • Crew Mod = crew module mass (if any)
  • Prop Mod 1 = propulsion module 1 mass
  • Prop Mod 2 = propulsion module 2 mass (if any)
  • Landing G = landing gear mass (if any)
  • Payload = valuable cargo mass tug is pushing, pulling, or hauling in cargo modules
  • Total Inert = dry mass, or total mass less propellant
  • Propellant = propellant mass, sum of main engine LOX and LH2. Oxygen/fuel (O/F) ratio of 6 to 1 or six units of LOX per 1 unit of LH2
  • Aux Con = auxiliary consumables mass. Pressurization nitrogen and RCS fuel.
  • Wet Mass = total spacecraft mass
  • Start Accel = spacecraft acceleration with full propellant tanks
  • Mass Ratio = mass ratio
  • ΔV = delta V, spacecraft's total possible velocity change

Space Tug: Parkinson

This 1975 design from Dr. R. C. Parkinson was faintly seen in an article The Resources of the Solar System by Dr. R. C. Parkinson (Spaceflight, 17, p.124 (1975)). It was off in the corner of a small diagram. I had an old photocopy of the article in my files since the late 1970's. I supplied them to William Black and he made stunning images of Dr. Parkinson's lighter and tanker. These images attracted the attention of a former colleague of Dr. Parkinson, a certain Dr. James Garry. He kindly introduced us to Dr. Parkinson and provided contact information. Dr. Parkinson generously supplied us with never before published diagrams and commentary.

In a private correspondence, Dr. Parkinson told William Black and I: “As a matter of interest, the "Space Tug" & Lunar Lander were based on some earlier design work done in Europe when it looked as if a cryogenic Space Tug might be the European contribution to the Space Shuttle program (those were the days!).”

In his visualization, William Black added additional engineering details. He put more struts to support the reaction-control jets and liquid oxygen tanks. Dr. Parkinson's notes indicated that the manned capsule had its own propulsion, so William added a single gimbaled low-thrust engine. He also added: a high-gain antenna for communications and a radar dish; forward-facing view ports for visual orientation during docking maneuvers; four forward-facing and four aft-facing cameras to aid in docking procedures.

Space Tug: Tinsley

Space tug concept by Frank Tinsley. Tug has grapples and grippers on its stern. The four square plates around its waist are ion drive units (The crewman's hatch is unfortunately placed right in the line of fire of one of the ion drives).

The petals near the bow are heat radiators. Sadly the radiators are spaced too closely. In reality one would want two radiators at 180° or at the most four radiators at 90°. The arrangement shown would have the heat from one radiator impinging on its neighbors.

And at the tip of the pointed prow would be the tiny nuclear reactor. It would be nice to include a small shadow shield to protect the crew from nuclear radiation.

Space Tug: ULA

This is from Robust Lunar Exploration Using an Efficient Lunar Lander Derived from Existing Upper Stages and A Commercially Based Lunar Architecture, both from United Launch Alliance (ULA).

The ULA's Advanced Common Evolved Stage (ACES) is basically a ULA standard propulsion bus. The idea is to avoid relying upon gigantic expensive launch vehicles such as the Ares_V (not to mention the fact that the Ares V doesn't exist yet). ULA proposes using the tiny ACES refueled with the miracle of orbital propellant depots so that smaller inexpensive commercial launch vehicles can be used instead of the expensive Ares V.

Without the support of orbital propellant depots, the ACES would have to lug along all the propellant needed for the entire freaking mission. Since Every gram counts, this would bloat the ACES design to the point where there was no choice but to use the pricy Ares V.

According to the second ULA report: "This strategy leads to high infrastructure utilization, economic production rates, high demonstrated reliability and the lowest possible costs." It will also help develop the infrastructure needed not only for Lunar operations, but also missions to Near Earth Asteroids and Mars. Establishing a propellant depot at the Terra-Luna L2 point will assist exploration outside of the Terra-Luna system. Since 75% of the mass being boosted to LEO is propellant, it is cheaper to use commercial launch vehicles. This also encourages conducting lunar exploration as a continuous process instead of a series of disconnected missions.

In addition to using propellant depots, the strategy includes using a common propulsion stage, the ACES module. Ideally the various components of the ACES should be commodities, that is, be off-the-shelf components available from several companies instead of just from ULA or NASA.


The ACES module uses its basic liquid hydrogen/liquid oxygen for main propulsion, propellant pressurization, RCS, power from fuel cells, and heat radiators. By using LH2/LOX for everything, it reduces the number of points of failure. E.g., helium tanks to pressurize the propellant, MMH/NTO for RCS, and solar panels for power are just three more systems that can break. ULA's buzzword for this concept is Integrated Vehicle Fluids.

This makes the ACES module a valuable component of a modular design spacecraft. It is doing its level best to be an "Instant spacecraft kit - just add payload".

The basic unit is the ACES 41 unit, containing 41 metric tons of propellant (liquic oxygen and liquid hydrogen). The "stretched" version, the ACES 71 contains, you guessed it, 71 metric tons of propellant. The stretching of the design is possible since all the subsystems are concentrated on the aft-mounted equipment deck, just forwards of the engines. All that needs to be done is add side-wall segments. Due to the clever planning of the orbital propellant network, only a 41 and 71 metric ton design are required. They can handle all the necessary tasks in the mission plan.

The tank has a diameter of 5 meters. It drastically reduces cryogenic propellant boil-off by a variety of methods: tank geometry, low conductivity tank structures, passive thermal protection, and vapor cooling. In addition the cryogenic propellant is subcooled so it can last longer. The tank's exposed surface is covered by a thick multi-layer insulation blanket, to reduce heating from Terra or Sol.

As preveviously mentioned, the ACES has no helium pressurization system, hydrazine fed RCS, nor solar power panels. Instead these functions are performed using the already present supply of LH2/LOX.

But the major feature is the tanks are designed to be refilled with propellants once in space. Practically no existing spacecraft can do this, but it is a sine qua non for utilizing orbital propellant depots.

ACES mounts 2 to 4 RL10 rocket engines.

In the lunar mission plan, the ACES module will be used for four primary in-space mission functions:

  • As service module propulsion system for an ACES 41/Orion spcecraft
  • As the descent propulsion system for an ACES 41/Altair lunar lander
  • As an ACES 71 propellant tanker
  • As a component of an ACES 71 propellant depot (14.6 metric tons LH2 capacity)

ACES/Orion spcecraft

Add to an ACES 41 an environmental control and life support system (ECLSS) Module and an Orion Crew Module, and you have an Orion spacecraft. The ACES 41 is acting as a "service module" for the Orion Crew Module. The ACES provides the propulsion, half of the RCS (other half is on Orion), electrical power, and heat radiator. The ECLSS provides the Orion Crew Module with N2 replenishment, CO2 scrubbing, and voice communication.


This is a "stretched" version of the ACES 41, the ACES 71 contains 71 metric tons of propellant. It will be used as a propellant tanker (71 metric tons of propellant) used to supply depots, and as the LH2 storage section of an depot (14.6 metric tons of liquid hydrogen).


This is an ACES 41 mated to a modified ACES 71. The ACES 71 section will be used for LH2 storage, and the ACES 41 section will be used for LOX storage.

The modified ACES 71 component has the bulkhead between the liquid hydrogen (LH2) and liquid oxygen (LOX) shifted in order to maximize LH2 storage. The engines are removed and a deployable sunshield is installed.

The depot has multiple interfaces for transferring propellant to and from the depot tanks. It can also supply power and support services to docked vehicles for extended periods.

The proposed orbital propellant depot network will have one depot in LEO and the other at L2

Yes, I am aware that other experts are of the opinion that L1 is superior to L2 when it comes to siteing Terra-Luna propellant depots. However ULA wants the depot at L2 to assist missions to Mars and other points outside the Terra-Luna system. An L2 depot can replace an L1 depot, but an L1 depot cannot replace an L2 depot.

The entire depot structure (both ACES 41 and ACES 71) is launched with the ACES 71 section empty, so the external insulation can be optimized for vacuum operations (as a depot) instead of needing foam cladding to deal with atmospheric heat. Since the ACES 71 empty shell, it has a mass of only 12 metric tons.

After launch into LEO, the ACES 41 section will have about 20 metric tons of propellant left. It will transfer the residual LH2 into the ACES 71 tank, vent the local tank, then fill the newly emptied local tank with the residual LOX. Remember that the ACES 71 section is for LH2 storage while the ACES 41 section is for LOX.

The depot will become the LEO orbital depot. Subsequent launches will fill the tanks and keep them filled.

The second depot launched into LEO is destined to be installed at L2.

Once it reaches LEO, the ACES 41 section will be refueled with both LH2 and LOX, since it will be used as a tug. The ACES 71 section will just be filled with LH2 since it is basically payload. The ACES 41 section transports the entire depot to L2.

The L2 depot will be kept topped up by periodic visits from a propellant tanker based on an ACES 71. EAch LEO to L2 trip will deliver 29 metric tons of propellant to the depot.

Temperature conditions are very different in LEO as compared to L2. LEO is a hot place, with thermal radiation from Terra heating up the depot tanks and boiling off propellant. L2 is relatively cold.

The depot uses a passive thermal protective system. It deals with the problem by being designed to primarily boil-off and vent gaseous hydrogen (since it has about ten times the thermal capacity of oxygen). It will boil-off about 27 kilograms a day. The liquid hydrogen is used to cool off the liquid oxygen, in other words. As it turns out, objects in LEO need lots of RCS action to keep the depot in its assigned spot and not falling out of orbit to a fiery doom or something like that. The boiled-off gaseous hydrogen can be used in RCS attitude jets to prevent that unhappy fate (Isp of 390 seconds, about 2 to 3 m/s of delta V per day). The boil-off and station-keeping needs can be balanced.

At L2 the heating rate is far less, boil-off of only one kilogram a day or so. Luckily at quasi-stable L2 the station-keeping requirements are also low.

The LEO Depot will lose about 10 tons of liquid hydrogen a year. However, since the plan has over 300 tons of propellant transfered through the LEO Depot in a year, the heating loss is less than 4%.


For Lunar operations, a belly lander spacecraft based on the ACES 41 propulsion bus will be used. This is called the Dual Thrust Axis Lander (DTAL) since it has two thrust directions: aft like a tail-sitter, and dorsal like a belly-lander. The DTAL-R is a robot controled cargo landing vehicle, the DTAL-Crew is a manned cargo landing vehicle.

Basic Element Mass Summary
Vehicle Element/AssemblyDry Mass
metric tons
metric tons
Basic ACES 41540.8 @ 5.25
Basic ACES 71/ Tanker5.570.7 @ 5.0
Orion Command Module6.0
Orion ECLSS Module2.0
Orion Crew & Associated Cargo1.0
Altair Cargo/Descent Module2.0
Altair Ascender3.04.0 @ 6.0
Altair Light Cargo3.5
Altair Heavy Cargo20.0
Depot Systems Module3.0
ACES Depot (2 docked ACES)12.5121
Vehicle Assembly Mass & Performance Summary
Vehicle AssemblyTotal Mass
metric tons
Delta V
Delta V
ACES/Orion @ LEO Departure54.85,6004,4005
ACES/Orion @ L2 Departure17.01,4008001.4
ACES /Altair @ LEO Departure58.36,3003,50013
ACES/Altair @ L2 Departure59.05,0002,90016
ACES/Altair Cargo @ LEO Departure74.83,9003,5003.0
ACES/Altair Cargo @ L2 Departure66.5Variable2,9004.0
ACES/Tanker @ LEO Departure76.211,3503,50029.0
Ascender @ Lunar Departure7.52,9002,6500.4

Lunar Transport Operations

In ULA's master plan there are seven "tasks."

Tasks 1, 2, and 3 are the Logistics Stream, they are handled by commercial space services. They are mostly concerned with the orbital propellant depots.

Tasks 4, 5, 6, and 7 are the Crew Transport Stream, and they are handled by NASA with help from contractors. They are mostly concerned with astronauts and exploration missions.

The important point is that the two streams are not closely coupled, they need only loose choreography. So the commercial services keeping the depots topped up do not need to keep close tabs on what NASA is doing. They only need enough cooperation to ensure that there will be propellant at the depot when NASA needs it.

The Logistics Stream

Trying to do space missions without propellant depots can waste lots of expensive equipment and propellant. With propellant depots you always get the maximum value out of each vehicle and drop of propellant.

Without depots, each spacecraft stage is designed for the worst-case scenario. If the payload turns out to be lighter than expected or there is a favorable launch window or if the stage performs better than you feared, the end result is you have to throw away tons of expensive propellant at staging. What a waste! But with depots, if you have left over propellant, you can load it into the local depot at the end of the trip leg. ULA says "The excess performance at each step of the way makes propellant a kind of currency that can be applied to downstream needs." In other words: waste not, want not.

TASK 1: Move propellant from surface into LEO Depot

Basically keeping the LEO depot topped off. The baseline plan is delivering about 30 metric tons per month.

This can be done by a wide range of launchers and providers, which is a good thing. Insuring against interruptions of service by a single provider is always prudent. This will be a great area for startup companies, since accidentally blowing up a tank of liquid hydrogen is no great loss. At least compared to accidentally blowing up a $200 million communication satellite. With competition launch prices will drop with time.

TASK 2: Move propellant from LEO Depot into L2 Depot

Because the LEO environment is so thermally hot compared to L2, you want to move propellant to L2 as fast as possible before it all boils away. Use it or lose it.

Given the capacity of the LEO Depot, the baseline is a propellant transfer to L2 roughly every other month. This can be done with a dedicated ACES Tanker, or with the left-over propellant from Altair or Orion visits. Since these craft can make the trip to L2 with propellant to spare, each trip is also a small tanker mission.

For dedicated Tanker missions, roughly every third tanker launch will continue on to the L2 Depot (after topping off their tanks with 30 or 50 tons of propellant from the LEO Depot, depending upon the launcher). The Tanker then departs for L2 in a low delta V trajectory that consumes about 41 metric tons. The remaining 29 metric tons or so are added to the L2 Depot.

There will be room for competition. If one of the service providers creates a tanker that uses an ion drive or other system allowing more propellant to be shipped, they will have a competitive advantage.

TASK 3: Move Altair and cargo to lunar surface

The most complex of the Logistics Stream commercial tasks is landing all the cargo on Luna. Before you can send any astronauts you are going to have to deliver tons and tons of cargo: rovers, radiators, solar power systems, gas handling and compressor systems, excavating equipment and other bulky cargo and consumables.

The robot ACES/Altair is boosted into LEO by a Delta IV HLV rocket. Altair has a mass of 36 metric tons. After refueling at LEO Depot it travels to L2, delivering about 30 tons of combined vehicle and cargo mass. The usual cargo will probably be less than this, meaning there will be residual propellant that can be added to L2 Depot's stash. If the Altair is intended to be cached at L2 for future crew use, it will deposit all its propellant into the depot for efficient long term storage.

Before the ACES/Altair performs a lunar landing it will load or top off its propellant tanks, including the Ascender tanks (if Ascender is present). The Altair fully loaded can deliver a combined mass of vehicles (such as the Ascender), cargo, and residual propellant greater than 40 metric tons to the lunar surface.

The ACES/Altair proper never returns from the lunar surface, though the separate Ascender can transport astronauts back to L2.

On the surface, the ACES/Altair's propellant tanks can act as storage tanks. LH2/LOX is not very useful as propellant at a lunar base, but it is very valuable to feed fuel cells, or to store the output of regenerative fuel cells. The tanks can also be fed from residual propellant from future ACES/Altair landings. "Tank farms" of landed ACES/Altair can be made, since the vehicles can be towed to be adjacent to other vehicles due to the little wheels on the landing gears.

As a nice bonus, the Altair will be tested again and again via robot landing, so all the dangerous bugs can be worked out before it is used to land actual human beings.

The Crew Stream

TASK 4: Move crew to L2

The Crew Stream will be under NASA control, but will use much of the same equipment. Especially the ACES 41.

Once the robot Altairs have delivered enough supplies and equipment to the lunar base site such that astronauts can actually live there, it is time to transport the crew to luna.

The ACES/Orion crew vehicle will be launched on an Atlas booster. The booster can deliver 11 metric tons of mass to LEO, enough for an ACES 41 and an Orion. The ECLSS Module, cargo, and crew will be delivered on a separate flight.

Once assembled and fueled, the ACES/Orion can travel to L2 in about 4 days using a high delta-V transfer. Upon arrival all propellant is transferred to the L2 Depot because it has better boil-off prevention. The Orion's station keeping, power, and other services are provided by the depot.

TASK 5: Move crew from L2 to lunar surface

A previously delivered crew ACES/Altair with an ascender module is prepped for the descent. Very little cargo will be carried because [A] there is a mountain of cargo at the site already, delivered by robot Altairs, [B] you want the crew Altair to have a very high performance margin so it can escape from disasters during the descent and [C] the residual propellant also sets the duration of the surface stay, since the propellant is also the astronaut's breathable oxygen and fuel for the fuel cells.

With a nominal landing, there should be about 10 metric tons of residual propellant.

The descent is powered by the main RL10 engines. As the lunar surface nears, the Altair rotates and switches to the banks of 4,500 Newton lateral thrusters to hover and land.

Once landed, the side cargo hatches can be opened, and the "bomb-bay"style airlock deployed from the belly.

If an emergency occurres during the descent, the ascender module can separate and carry the crew back to L2 while the Altair falls to its doom.

TASK 6: Move crew from lunar surface to L2

The Ascender module uses banks of 4,500 Newton lateral engines burning the same LH2/LOX that everything else uses. The lateral engine propellant tanks are only filled shortly before lift-off, since the main tanks have superior boil-off resistance. This does lose a couple of kilograms of propellant due to tank chilldown, but more would be lost by boil-off.

Each bank has 12 small engines that are throttled to about 30% power. They are located such that they can accommodate substantial differences in the ascender's center of gravity (easy with 12 small engines, hard with one large engine). The exhaust is angled such that it does not incinerate the Altair that is left behind, future expeditions can use it.

The ascender travels to the L2 Depot, docks, and dumps its residual propellant into the depot. It will be reused, being attached to a newly arrived ACES/Altair.

TASK 7: Move crew from L2 to Terra

The crew from the Ascender module transfer to the ACES/Orion that brought them. The tanks are filled and it travels to Terra. It only needs 10% of propellant capacity for the trip. The delta V cost is so modest that the trajectory can be initiated with the RCS instead of the main RL10 engines, not that you'd want to do that.

Space Tug: William Black


Light Freighter for intraorbital service between space colonies and industrial platforms, designed for the System States Era of my Orion’s Arm future history setting.

A timeline for my future history is to be found here: Timeline

In the System States Era asteroid mining operations thrive throughout the asteroid belt and among the moons of Jupiter and Saturn the Martian terraforming program has left legacy: a sprawling archipelago of island stations and industrialized moons, Bernal Sphere's and O'Neill Cylinders, Spindle and Wheel cities, and a population of humanity growing into the millions. Space colonies are independent city-states and trade is their lifeblood. Entire generations are born and live their lives in spinning cylinders, bubbles, and torus shaped habitats, harvesting, mining, and fabricating all they need from the environment of the outer solar system.

Orion and Medusa style nuclear pulse freighters haul payloads of raw materials across interplanetary distances, while nuclear orbital transfer vehicles (OTV’s) provide light freight and passenger service between space habitats in Jupiter and Saturn orbit.

For a table of Delta V required for travel using Hohmann orbits among the moons of Saturn see
Why Saturn on Winchell Chung’s Atomic Rockets site. Scroll a little further down the page and you will find a Synodic Periods and Transit Times for Hohmann Travel table for Moons of Saturn.

Nuclear propulsion Systems: Operational Constraints

The abundance of various chemical ices for use as reaction mass among the moons of the outer system gas giants makes NERVA an excellent option for commercial application. Nuclear thermal rockets provide excellent efficiency; they also impose certain operational restrictions. The engine emits significant levels of radiation while firing and even after shut-down, and while passengers and crew are protected by the engines shadow-shield and hydrogen tanks, you wouldn’t want to point the engine at other spacecraft or space platforms. During the U.S. nuclear thermal rocket engine development program NFSD contractors had recommended that no piloted spacecraft approach to within 100 miles behind or to the sides of an operating NERVA I engine. The only safe approach to a spacecraft with a NERVA engine is through the conical “safe-zone” within the radiation shadow created by its shadow-shield and hydrogen tanks. Docking NERVA propelled spacecraft to a space station or habitat is problematic because structures protruding outside the conical safe-zone can reflect radiation back at the spacecraft, irradiating the passengers and crew.

These facts impose a set of mandatory operational parameters and flight rules for nuclear operation. An exclusion zone for nuclear propulsion (60 kilometers minimum) is imposed around every orbital platform. Orbital Guard units would hold broad discretionary powers—violate an exclusion-zone or disregard traffic-control and the local guard will cheerfully vaporize your spacecraft. No warning shots, no second chances. A crew that violates flight rules doesn’t live long enough to worry about fines or attorney fees, and the public’s time and funds are not wasted with trials of incompetent captains and crew.

Nuclear Freighters “park” propulsion modules in station-keeping orbit with their destination, and the freight/passenger module undocks, separating from its nuclear propulsion module, proceeding to birthing under thrust of a chemical maneuvering unit.

Because the nuclear propulsion modules are valuable, and are potentially deadly missiles if mishandled — codes to access the autonomous flight computer and possession of the nuclear propulsion module are temporarily handed over to the local orbital-guard for safe keeping.

For a good example of Space traffic control see the entry on Winchell Chung’s Atomic Rockets site here and scroll down to quote from Manna by Lee Correy.

At this point in my future history, 750 years post Martian colonization, spacecraft are essentially stacks of common modules which can be swapped out to suit application.

Independent Operators, like today’s truckers, might “own” only the CMOD (Command Module) with other units being leased per flight. The Freight Carrying Structural Spine, essentially a rigid frame with mountings for cargo modules, might be leased by the shipper and loaded with cargo (but owned by a separate freight transport supplier) and since different payloads mass differently it might be the responsibility of the shipper to lease suitable nuclear and chemical propulsion modules rated to the task. Passenger transport services might likewise lease passenger modules of varying capacity and Transport Brokerage firms would coordinate freight and passenger payloads assigned to same destinations and offer these in an open-bid market.

Propulsion Modules

Different payload masses require different propulsion module configurations, the light freighter detailed here requires only a single Solid-Core nuclear thermal rocket. A heavy payload freighter might use clusters of solid-core, or Open-Cycle Gas-Core, nuclear thermal rockets.


3D models are my own conception based on various real-world proposals.

As research for the passenger/crew module I studied the POTV (Personnel Orbital Transfer Vehicle) pages 86-96 from NASA Technical Memorandum 58238 Satellite Power System: Concept Development and Evaluation Program Volume VI1 -Space Transportation available: here.

Propulsion for my light freighter is a Solid-Core NERVA Derivative, details available here.

In conversation Winchell Chung suggested the modification Cascade-Vanes: details available here.


Space Tug: Other

Skeletons And Spacesuits

I noticed a couple of pulp covers with skeletons in spacesuits. So I looked on Google image search. I had no idea it was such a wide-spread meme.

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This week's featured addition is Nuclear Pulse Helios

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