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

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

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

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

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

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

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

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

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

...or any other division of 30.

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

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

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

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

In NASA-speak:

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

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


The basic requirements for life support are:

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

The first three requirements are called "consumables", since they are gradually used up by the crew. Each of those three can be controlled by either an "open" system or a "closed" system.

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

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

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

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

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

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

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


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

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

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

– “Sophontology of the Talentar Settlers”
Mirial Quendocius

Breathing Mix

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

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

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

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

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

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

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

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

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

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


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

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

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

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


Making Oxygen

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

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

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

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

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

For emergency use, it would be wise to pack away a few Oxygen Candles. These are composed of a compound of sodium chlorate and iron. When ignited, they smolder at about 600°C, producing iron oxide (rust), sodium chloride (salt), and approximately 6.5 man-hours of oxygen per kilogram of candle. Molecular Product's Chlorate Candle 33 masses 12.2 kilos, cylindrical can dimensions of 16 cm diameter x 29 height, burns for 50 minutes, and produces 3400 liters of oxygen.

Removing Carbon Dioxide

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

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

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

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

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

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

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

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

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

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

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

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

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

..."That puts me in mind of something that happened to me when I was 'farmer' in the old Percival Lowell -- the one before the present one," Yancey went on. "We had touched at Venus South Pole and had managed somehow to get a virus infection, a sort of rust, into the 'farm' -- don't look so superior, Mr. Jensen; someday you'll come a cropper with a planet that is new to you!"

"Me, sir? I wasn't looking superior."

"No? Smiling at the pansies, no doubt?"

"Yes, sir."

"Hmmph! As I was saying, we got this rust infection about ten days out. I didn't have any more farm than an Eskimo. I cleaned the place out, sterilized, and reseeded. Same story. The infection was all through the ship and I couldn't chase it down. We finished that trip on preserved foods and short rations and I wasn't allowed to eat at the table the rest of the trip."


"Yes, Dodson?"

"What did you do about air-conditioning?"

"Well. Mister, what would you have done?"

Matt studied it. "Well, sir, I would have jury-rigged something to take the Cee-Oh-Two out of the air."

"Precisely. I exhausted the air from an empty compartment, suited up, and drilled a couple of holes to the outside. Then I did a piping job to carry foul air out of the dark side of the ship in a fractional still arrangement -- freeze out the water first, then freeze out the carbon dioxide. Pesky thing was always freezing up solid and forcing me to tinker with it. But it worked well enough to get us home."

From SPACE CADET by Robert Heinlein. 1948.

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

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

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

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

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

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

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

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

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

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

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

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

From STEP TO THE STARS by Lester Del Rey. 1954


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

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

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

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

How do you calculate safe breathing mixes for yourself?

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

How do you calculate the partial pressure of oxygen?

pO2 = pMix * O%

pMix = pO2 / O%


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

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

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

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

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

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

A more annoying than serious problem with low pressure atmospheres is the fact that they preclude hot beverages and soups. It is impossible to heat water to a temperature higher than the local boiling point. And the lower the pressure, the lower the boiling point. You may have seen references to this in the directions on certain packaged foods, the "high altitude" directions. The temperature can be increased if one uses a pressure cooker, but safety inspectors might ask if it is worth having a potentially explosive device onboard a spacecraft just so you can have hot coffee.

The Bends

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

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

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

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

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

Please note that sometimes the bends can occur if one moves from one habitat to another that has the same pressure, but a different ratio of breathing mix (the technical term is "Isobaric counterdiffusion"). Spacecraft of different nations or models could use different breathing mixes, beware. In fact, rival astromilitaries might deliberately utilize odd-ball breathing mixes, to make life difficult for enemy boarding parties invading their ships.

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

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

The astronaut(s) enter the airlock, and the airlock pressure is reduced to 10.2 psi. They breath pure oxygen through masks for 60 minutes (because the air in the airlock contains nitrogen). They then put on their space suits and do an EMU purge (i.e., flush out all the airlock-air that got into the suit while they were putting it on, to get rid of stray nitrogen). The air inside their suits is now also pure oxygen. The airlock pressure is then brought back up to the normal 14.7 psi. They then do 100 minutes of in-suit prebreath. Of those 100 minutes, 50 of them are light-exercise minutes and 50 of them are resting minutes. "Light exercise" is defined as: flex your knees for 4 minutes, rest 1 minute, repeat until 50 minutes has passed. Thus "Slow Motion Hokey Pokey". Now they are ready to open the airlock and step into space.

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

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

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

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


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

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

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


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

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

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

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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

From FIREPROOF by Hal Clement (1949)

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

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

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

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


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


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

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

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

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

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

From SPECIAL ACCOMMODATIONS by Rob Garitta (2016)

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

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

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

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

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

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

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

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

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

From PODKAYNE OF MARS by Robert Heinlein

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

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

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

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

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

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

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

Atmospheric Contaminants

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Meteor Punctures

Meteors are probably nothing to worry about. On average a spacecraft will have to wait for a couple of million years to be hit by a meteor larger than a grain of sand. But if you insist, there are a couple of precautions one can take.

Whipple Shield

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


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

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

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

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

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

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

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

From ROCKET SHIP GALILEO by Robert Heinlein. 1947.

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

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

From SPACE CADET by Robert Heinlein. 1948.

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

From SPACEMEN LOST by George O. Smith (1954)

Hull Patching

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

From PASSAGE AT ARMS by Glen Cook (1985)

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

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

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

(ed note: then the accident happens)

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

From GENTLEMEN, BE SEATED! by Robert Heinlein (1948)


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

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


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

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

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


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

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

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


  • t = time for the pressure to drop (seconds)
  • V = volume of compartment (m3)
  • A = Area of the hole (m2)
  • P0 = stagnation pressure in room (far from the hole) (Pascals) (cabin normal = 101,300; spacesuit normal 32,400)
  • Pƒ = final pressure in room (Pascals) (cabin anoxia = 25,200; spacesuit anoxia = 5,300)
  • T = Stagnation temperature in room (far from the hole) (Kelvin) (about 293 K for room temperature ~20°C; note √293 ~ 17.12)
  • sqrt[x] = square root of x
  • ln[x] = natural logarithm of x

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

So if a posh passenger cabin of 15 cubic meters has a 3 square centimeter hole (area 7.07×10-4 m2) blown in the bulkhead by a wayward meteor, the inhabitants have an entire 151 seconds (about two and a half minutes) before anoxia strikes.

Somebody in a space suit doesn't have that kind of time. The suit has a volume of approximately 0.02 cubic meter. A hole a half-centimeter in diameter has a hole area of 1.96×10-5 square meters. As long as the suit's air tanks can keep up the loss the pressure won't drop. But once the tanks are empty, the pressure will drop to anoxia levels in a mere 9.3 seconds.

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

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


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

The Physics Of Decompression And Constricted Airflows

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

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

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

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

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

The Human Race Needs To Breathe To Survive

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

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

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

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

Does "The Expanse" Get It Right?

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


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

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

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

There was a hissing noise.

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

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

That scared me to death.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

I said, "Yessir."

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

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

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

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

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

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

An emergency space suit is currently science fiction. It is some temporary suit you can put on in about thirty seconds.

Equipment used to save untrained civilians in case of a loss of pressure can be found here.

The science fiction suit hinges on some kind of oxygen you can inject into your blood stream to avoid anoxia. Coupled with some kind of suit to provide pressure to avoid Ebullism, Decompression Sickness, Kittinger Syndrome, and other nasty ways that space kills you.

Star Trek predicted something along these lines called "tri-ox compound." The novel Phase Two postulated "dioxo solution." As it turns out there is a real world version of injectable oxygen being experimented with. It only works for 15 minutes but I'm sure that will be improved.


(ed note: technical term is apparently Intravenous Oxygen or Injectable Oxygen)

      Boston, Mass. - Patients unable to breathe because of acute lung failure or an obstructed airway need another way to get oxygen to their blood—and fast—to avoid cardiac arrest and brain injury.  A team led by researchers at Boston Children’s Hospital has designed tiny, gas-filled microparticles that can be injected directly into the bloodstream to quickly oxygenate the blood.
     The microparticles consist of a single layer of lipids (fatty molecules) that surround a tiny pocket of oxygen gas, and are delivered in a liquid solution.  In a cover article in the June 27 issue of Science Translational Medicine, John Kheir, MD, of theDepartment of Cardiology at Boston Children’s Hospital, and colleagues report that an infusion of these microparticles into animals with low blood oxygen levels restored blood oxygen saturation to near-normal levels, within seconds. 
     When the trachea was completely blocked— a more dangerous “real world” scenario—the infusion kept the animals alive for 15 minutes without a single breath, and reduced the incidence of cardiac arrest and organ injury. 

     The microparticle solutions are portable and could stabilize patients in emergency situations, buying time for paramedics, emergency clinicians or intensive care clinicians to more safely place a breathing tube or perform other life-saving therapies, says Kheir.
     “This is a short-term oxygen substitute—a way to safely inject oxygen gas to support patients during a critical few minutes,” he says. “Eventually, this could be stored in syringes on every code cart in a hospital, ambulance or transport helicopter to help stabilize patients who are having difficulty breathing.”
     The microparticles would likely only be administered for a short time, between 15 and 30 minutes, because they are carried in fluid that would overload the blood if used for longer periods, Kheir says.
     Kheir also notes that the particles are different from blood substitutes, which carry oxygen but are not useful when the lungs are unable to oxygenate them. Instead, the microparticles are designed for situations in which the lungs are completely incapacitated. 

     Kheir began investigating the idea of injectable oxygen in 2006, after caring for a little girl who sustained a severe brain injury resulting from a severe pneumonia that caused bleeding into her lungs and severely low oxygen levels. Despite the team’s best efforts, she died before they could place her on a heart-lung machine. Frustrated by this, Kheir formed a team to search for another way to deliver oxygen.
     “Some of the most convincing experiments were the early ones,” he says.  “We drew each other’s blood, mixed it in a test tube with the microparticles, and watched blue blood turn immediately red, right before our eyes.”
     Over the years, Kheir and his team have tested various concentrations and sizes of the microparticles to optimize their effectiveness and to make them safe for injection. “The effort was truly multidisciplinary,” says Kheir. “It took chemical engineers, particle scientists and medical doctors to get the mix just right.” 
     In the studies reported in the paper, they used a device called a sonicator, which uses high-intensity sound waves to mix the oxygen and lipids together. The process traps oxygen gas inside particles averaging 2 to 4 micrometers in size (not visible without a microscope). The resulting solution, with oxygen gas making up 70 percent of the volume, mixed efficiently with human blood.
     “One of the keys to the success of the project was the ability to administer a concentrated amount of oxygen gas in a small amount of liquid,” Kheir says. “The suspension carries three to four times the oxygen content of our own red blood cells.”
     Intravenous administration of oxygen gas was tried in the early 1900s, but these attempts failed to oxygenate the blood and often caused dangerous gas embolisms. 
     “We have engineered around this problem by packaging the gas into small, deformable particles,” Kheir explains. “They dramatically increase the surface area for gas exchange and are able to squeeze through capillaries where free gas would get stuck.

From INJECTING LIFESAVING OXYGEN INTO A VEIN by Boston Children’s Hospital (2012)

(ed note: Stan does not realize he has been subjected to a hyper-learning technique in school that has programmed his brain with spacecraft survival protocols, among other things. He books a trip with Captain Paulsen to travel to the asteroid belt. An assassin has planted a small explosive charge to blow a hole in the ship's habitat module and kill Stan and Paulsen. Due to the assassin's ignorance of spacecraft survival protocols the attack is ineffectual.)

Excitedly Stan turned to the skipper, but his thoughts were cut off by a thunderclap which hammered his body. Instantly the explosion was followed by a high-pitched, whining scream that echoed on each nerve, and the internal feeling of bursting that meant rapidly falling atmospheric pressure.

Terror tore at his nerves—the terror of vacuum, of space, of the emptiness around the tiny ship; of the internal explosion in vacuum that would extinguish forever the tiny spark that was himself … Yet the terror seemed to lie on an unimportant shelf of his consciousness, while his body took on a life of its own—opening his mouth and yelling to expel the pressure from his lungs.

Then his eyes turned as of their own volition to Paulsen, whose lips were moving, whose fingers were reaching out to a control—the control that would cut the motors, Stan realized. At the same moment he found himself releasing the straps on his own body and pushing out of the deep seat, twisting with the push to bring his hands into line with the small opening in the wall above and behind their seats.

The shelved panic jibbered at him as his fingers found the opening and began groping, since his eyes were losing their focus. The scream was fading, then cut off abruptly just as his fingers found the syrettes they were seeking. He grasped two and reached one toward Paulsen.

The skipper was almost beside him now, a hazy figure, and Stan groped for his hand, forcing one of the syrettes into it. Then he brought the remaining syrette to his leg with a slap that forced the needle in and injected its contents into his system.

The jibbering idiot on the shelf of his mind was subsiding slowly as he pulled the syrette carefully out, pinned it to his tunic. His eyes now could barely make out the most gross objects in the cabin swinging lazily about him as he spun slowly in free fall.

The dioxo solution from the syrette spread a warm glow through him. Stan opened his mouth wide and expelled the last of the air that was doing its best to strain out of his lungs. The pressure in his ears let go with a loud pop. The cloudy look of things before him and the burning sensation in his eyes caused him to squeeze them tight shut, and as he did so pain shot through them, and the jibbering panic clawed again for his brain. Tiny crystals of ice were grating across the tender surfaces of his eyes, he knew; and as this was followed by a sensation of cold, he realized that the boiling tears would freeze in the vacuum around him and freeze the eyelids shut.

Something grasped him, and momentarily the panic took over and he twisted ready to slug. Instantly he realized that it was Paulsen, and he took the fear almost physically, shoving it aside and completely away, before he turned his attention back to what Paulsen was doing.

It felt as though he were being stuffed into a bag, but there was no sound. Then he felt drawstrings pull tight at his shoulders and across his chest, and abruptly there was pressure around his face again. And Paulsen was sliding the bag down over his arms, tying it at each joint; then down over the torso with a repeated lacing.

Blinded by tears, Stan opened his eyes to see clear plastic standing only inches ahead; and, as he began to breathe again, Paulsen’s voice came to him over a tiny speaker somewhere in the hood.

“That’s right, Dustin. Work your jaws and the swallowing mechanisms. Keep blinking your eyes.”

As Stan became more aware of his surroundings, he saw that he was in a loosely fitting plastic bag, tightly belted at each joint.

I’ll be damned, he thought. A Mickey Mouse.

There was a tingling sensation in his throat, and he realized that the “air” he was breathing was not air but carbon dioxide quickly developed from a small plastic pack of acid and soda, from between which the separating plug had been pulled; a gas generator designed to supply the necessary minimum pressure to the suit. It was a device that could not have been used except for the diox which would supply his oxygen requirements for the next hour.

Temporarily safe, the panic vanished to whatever realm he had thrown it, Stan found a handhold and turned himself toward the control panel.

Paulsen was in his seat now, checking the space around the ship for enemy craftbut the guy wasn’t in a spacesuit!

Unbelieving, Stan stared. Paulsen had on a hood, but just that, over his regular red pilot’s suit.

But of course. That pilot’s suit was a gas-proof spacesuit; and the hood that had obviously been unzipped from a pocket at the back of the pilot’s suit collar had a similar low-pressure gas-generator packet.

Stan sighed his relief, then let his attention slide to the deep hole in the checkerboard wall centered above the control panel.

The hole was a full two-foot square that had blown through to the outside of the hull and was now crushed there; a mess of metal and foam plastic insulation, at the bottom of what seemed to be a square tunnel into the hull structure. The water shielding from the compartment had obviously been blown on through into space, followed by the air from the control cabin; but the hole through which they had blown could not be seen past the mess of metal and plastic.

Paulsen was through with his check now, and his face looked puzzled, but he only said, “I’m going to put us under drive to get gravity, then we’ll see what the damage is.”

The return of even the light one-tenth-G gravity was grateful to Stan’s senses, and the cabin reoriented quickly around him.

“If we can/work fast,” Paulsen’s voice came to him abruptly over the tiny intercom, “we can save having to pressurize the bunk area to get you into a tightsuit. I’ve got plug-in compartments aboard, of course, so it shouldn’t take more than half an hour to clear up this mess. Do you think you can take the Mickey Mouse for that long?”

Experimentally, Stan flexed his arm and found that it responded stiffly. The veins that had been standing out like cords against his taut skin were beginning to recede. The rapid breathing induced by the one hundred percent carbon-dioxide atmosphere was exchanging nitrogen out of the blood at a rapid rate, and pressure was equalizing between himself and the suit.

“Seems okay,” he said. “A little stiff and a few cramps, but yeah, I can work like my life depended on it. I didn’t know they were plug-in compartments, though. I can take the Mickey Mouse all right. I just didn’t know the problem could be resolved so quickly.”

“It’s a Belter, not an Earthie system. You’ve surprised me so often with your Belter know-how, I guess I’m surprised now when you don’t know.” Paulsen chuckled, then without another word crawled into the tight tunnel.

From PHASE TWO by Walt and Leigh Richmond (1979)

(ed note: this does not require injectable oxygen, it has a shoulder PLSS)

Alice was beside him in the other hammock. Her eyes were open, her mouth faintly frowning.

That scared him. "What is it?"

"I don't know. Suit up."

He grimaced. Suit up—she'd had him climbing in and out of that damn emergency suit for six hours of the first day. It was a man-shaped clear plastic bag with a zipper that ran from chin to knees, forking at the crotch. You could get into it in an instant, and it took another instant to plug that thick air-and-water tube into the ship's lifesystem; but he'd caught the zipper a couple of times and got language one does not expect from one's sex partner regardless of previous experience. "From now on you wear nothing but a jock strap," she'd ordered. "And you wear that all the time. Nothing gets caught in that zipper." The last couple of hours she was throwing the suit at him from behind, a crumpled ball he had to shake out and get into in ten seconds. When he could do it with a blindfold, she was satisfied.

"It's your first move," she'd said. "Always. Anything happens, get into that suit."

He snatched the suit without looking, slid feet and hands and head in and zipped it two-handed and plugged into the wall. Another instant to pull the shoulder pack out of its recess, slip it on, pull the plug and plug it into that. Stored air filled his suit, tasting tasteless. Alice was still faster; she was ahead of him, swarming up the ladder.

From PROTECTOR by Larry Niven (1973)

Blown Out The Airlock


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

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

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

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

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

Object (human) parameters:

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

Chamber parameters:

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

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

Derived/calculated quantities:

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

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

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

Applicable equations:

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

Values at t = 0 s (3 figures):

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

Values at t = 1 s (3 figures):

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

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

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

Applicable equations:

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

Values at t = 0 s (3 figures):

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

Values at t = 1 s (3 figures):

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

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

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

Applicable equations:

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

Values at t = 0 s (3 figures):

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

Values at t = 1 s (3 figures):

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

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

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

Applicable equations:

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

Values at t = 0 s (3 figures):

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

Values at t = 1 s (3 figures):

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

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

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

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

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

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


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


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

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

f(t) = ½ ρ(t) vr(t)² C_D A

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

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

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

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

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

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

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

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

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

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

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

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

d/dt M(t) = -ρ(t) h va

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

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

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

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

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

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

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

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

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

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

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

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


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

Brian Davis

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

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

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

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

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

John Park

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

Tim Little

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

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

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

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

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


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

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

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

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

Dr J. R. Stockton

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

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

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

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

Tim Little

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

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

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

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

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

John Schilling

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

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

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

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

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

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

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

Erik Max Francis

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

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

Russell Wallace

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

Wayne Throop

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

Tim Little

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

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

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

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

Erik Max Francis

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

Michael Ash

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

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

Wayne Throop

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

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

Robert Martinu

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

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

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


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

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

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

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

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

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

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

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


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

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

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

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


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

NASA has a variety of space foods. Preparing food for prolonged space missions is always a challenge.

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

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

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

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

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

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

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

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

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

Add about 1000 liters of water (water for 150 crew for 90 days, plus a reserve) which of course masses 1000 kg.

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

Together air and water add about 5 m3.

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

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

When the body uses glucose the reaction is:

C6H12O6 + 6 O2 => 6 CO2 + 6 H2O

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

Eeking Out

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

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

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

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

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

Eating Utensils

On NASA shuttle and ISS missions, the astronauts have conventional knives, forks, and spoons; a hot/cold water injector, a warming oven, and scissor to cut open plastic seals.

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

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

The warming oven is a forced air convection oven with internal hot plate. Its internal temperature is from 71° to 77° C. It can hold up to 14 food containers at a time: rehydratable packages, thermostabilized pouches or beverage packages.

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

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

Drinking Utensils

Emergency Rations

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

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

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

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

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

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

The most famous science fiction field ration is the Federation Space Forces Emergency Ration, Extraterrestrial, Type Three (aka 'Extee 3' or 'estefee') from Little Fuzzy by H. Beam Piper.

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

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

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

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

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


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

From STAR GUARD by Andre Norton (1955)

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

The First Watch Officer comes through the Weapons hatch. He has a metal case in his arms, a sheet of paper in one hand. The Commander peers into the case. "Pass them around." He snatches the tattered sheet.

Yanevich hands me a ration packet. I laugh softly.

"Something wrong with it?" the Old Man asks.

"Emergency rations! This's better stuff than we've been eating for three months." I pull the heat tab. A minute later, I peel the foil and — lo! — a steaming meal.

It's no gourmet delight. Something like potato hash including gristly gray chopped meat, a couple of unidentifiable vegetables, and a dessert that might be chocolate cake in disguise. The frosting on the cake has melted into the hash. I polish the tray, belch. "Damn, that was good!"

Yanevich gives each man a meal, then hands me another pack. They come forty-two to a case. He sets the last aside for the Chief. To my questioning frown, he says, "That's for your buddy."

Out of nowhere, out of the secret jungles of metal, comes Fearless Fred (the cat), rubbing my shins and purring. I heat his pack, thieve the cake, place the tray on the deckplates. Fred polishes his tray in less time than I did mine.

From PASSAGE AT ARMS by Glen Cook (1985)

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

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

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

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

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

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

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

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

From THE ZERO STONE by Andre Norton (1968)

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

Kelly seemed puzzled.

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

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

From SPACE ANGEL by John Maddox Roberts (1979)

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

James Comer notes:

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

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

From WEST OF HONOR by Jerry Pournelle (1976)

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

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

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


Waste Disposal

On the topic of human metabolic waste, NASA assumes:

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

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

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

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

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

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

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

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

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

Warshall: For each time?

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

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

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

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

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

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

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

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

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

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

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

Warshall: How do you get it in there?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

From PACKING FOR MARS by Mary Roach (2010)

Feces and Debris

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

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

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

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

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

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

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

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

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

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

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

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

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

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


Astronaut hygiene is complicated.

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

Bath and showers are very difficult in free fall. The crew will probably be reduced to sponge-baths or maybe a shower while zipped up in a bag. In Robert Silverberg's 1968 novel World's Fair 1992 he mentions "sonic showers" which use sound waves to remove dirt with no water required. In Babylon 5, only the command and VIPs have water showers, the rest have to make do with "vibe showers". And in Andre Norton's space novels, the bathing room is called the "fresher" which presumably is short for "refresher". As TV Tropes says: Our Showers Are Different.

People who have gone camping are familiar with how surprisingly difficult it is to keep clean in the absence of running water. As do city-folk living in houses near a water main break who have to make do without tap water for a few days. You tend to take for granted the luxury of accessing unlimited amounts of water out of the faucet. In the space environment, water is strictly limited, and what water there is performs poorly as a cleansing agent in free fall.

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


Lack of cleanliness

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

From THE RACE TO MARS Discovery Channel

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

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

From STARFARERS by Vonda McIntyre (1989)

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

From Leviathan Wakes by James Corey (2011)

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

From THE ROLLING STONES by Robert Heinlein (1952)

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

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

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

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

– The Starship Handbook, 155th ed.


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

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

From GALACTIC DERELICT by Andre Norton (1959)

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

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

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

...Susan slipped a personal package to Tanya...

..."How many are in here?"

"Four hundred."

"Tanya's eyes widened. "Four hundred?"

"We're the miracle workers of folded fragrance."

From EXIT EARTH by Martin Caidin (1987)

Cleaning Hab Interior

Keeping the habitat module clean is also a challenge. Water is limited, water does not clean things very well in free fall, and the limited atmosphere prevents one from using any alternate cleanser that it toxic or has a disagreeable odor.

And as mentioned elsewhere, any free floating garbage tends to accumulate on the air-intake vents. The vents on the Skylab space station quickly became quite disgusting with random bits of rotting food and dust particles.



The crews of any aerospace vehicle will generate particulate matter from their bodies and their clothing. Equipment also releases particulates. In a weightless state this debris will float in the cabin until it is entrained by the ventilation gas or is separated and captured by a surface (such as a crewman's lungs). Of course, the ventilation gas and filters will remove most of the debris; however, some spaces in the cabin will tend to accumulate floating debris due to a lack of sufficient ventilation. Therefore, on long duration missions (of one or more weeks) a vacuum cleaner should be provided to collect this material—which may include viable microorganisms and the media necessary for growth.

If the vehicle is provided with a pneumatic collection system for urine and/or feces, the fan used for this purpose can also be used to draw gas into a small debris collection bag. This bag can be made from the same material as the fecal collection bag. A gas flow rate of 5 ft3/min is adequate for this purpose.

A personal grooming device-vacuum cleaner is provided on a branch of the control air circuit of the waste management unit. This collects hair, nail clippings, shaving clippings, etc. Collection bags are provided to dry and store the wastes.


One of the shipboard roaches woke Lindsay by nibbling his eyelashes. With a start of disgust, Lindsay punched it and it scuttled away.

... He shook another roach out of his red-and-silver jumpsuit, where it feasted on flakes of dead skin.

He got into his clothes and looked about the gym room. Two of the Senators were still asleep, their velcro-soled shoes stuck to the walls, their tattooed bodies curled fetally. A roach was sipping sweat from the female senator's neck.

If it weren't for the roaches, the (spacecraft) Red Consensus would eventually smother in a moldy detritus of cast-off skin and built-up layers of sweated and exhaled effluvia. Lysine, alanine, methionine, carbamino compounds, lactic acid, sex pheromones: a constant stream of organic vapors poured invisibly, day and night, from the human body. Roaches were a vital part of the spacecraft ecosystem, cleaning up crumbs of food, licking up grease.

Roaches had haunted spacecraft almost from the beginning, too tough and adaptable to kill. At least now they were well-trained. They were even housebroken, obedient to the chemical lures and controls of the Second Representative. Lindsay still hated them, though, and couldn't watch their grisly swarming and free-fall leaps and clattering flights without a deep conviction that he ought to be somewhere else. Anywhere else.

(ed note: Alistair Young calls those "cleaning roaches")

From SCHISMATRIX PLUS by Bruce Sterling (1996)

(ed note: The Christmas Bush is a Fractal Robot. Tiny parts can be separated to be small robots "sub-motiles")

Now, let me show you some of its other tricks." He reached into his shirt pocket and pulled out a pressurized ball-point pen. He then unbuttoned his shirt front and used the pen to push out a bit of lint from behind a button-hole. He kicked over to a nearby wall and deliberately made an ink mark on the wall. As he kicked back, he let loose the bit of lint into the air. As he came to a halt back with the group, they watched as two tiny segments of the Christmas Branch detached from one of the arms. The smaller one, a minuscule cluster of cilia not much bigger than the bit of lint, flew rapidly through the air with a humming sound like that of a mosquito, captured the floating ball, and flew out the door to another part of the ship, zig-zagging as it went.

"It's picking up other bits of dust on its way to the dust-bin," explained David. "They're too small for us to see, but its little laser radars picked them up from their backscatter."

The larger sub-motile jumped from the Christmas Branch to the wall, and like a spider, used its fine cilia to cling to the wall and walk over to the ink smudge. The cilia scraped the ink out of the wall pores and formed it into a drying ball. The wall now clean, a sub-section of the spider detached and swam off through the low gravity, while the remainder of the spider jumped back to the Christmas Branch where it resumed its normal place.

"Yet housekeeping is a continual chore, so don't be surprised if you see a mosquito flying through the air or a spider walking across the ceiling. They will just be collecting all the dirt and dust you've made that day."

The Christmas Bush was busy weaving cloth using a bright green artificial thread that it had reconstituted from the lint fibers it had collected over the past years.

From ROCHEWORLD by Robert Forward (1982)

Vermin Control

Once space travel matures to the point where spacecraft are regularly traveling between locations with habitable environments, the ships will tend to become infested with vermin. Rats and cockroaches invaded seagoing vessels about five minutes after ships were invented. And after thousands of years they are still a problem. Spacecraft are highly unlikely to be free of the problem, unless ships are single-use items and only travel to airless worlds.

And we all know how indestructible roaches and rats are. Atomic radiation just slows them up a little. Only slightly more vulnerable are bed bugs.

Possible solutions include fanatical cleaning of the habitat module, periodic temporary removal of the hab module's breathable atmosphere to create vacuum, Ship's cat or other animals, and tiny hunter-killer robots.

If vacuum doesn't finish them off you have a real problem. You might have to go to the next level and flood the place with poison gas/insecticide. The trouble with that is purging the module of the poison afterwards so it doesn't kill the crew. And how tense things will get if an emergency crops up right in the middle of the gassing.

But if radiation mutates the vermin to the point where they actually become intelligent, well you are truly up sewage pulsar with no gravity generator.


Star Trek: Mission to Horatius
In this incredibly tedious Star Trek novel the starship Enterprise has been on such a prolonged mission that Dr. McCoy is worried that the crew is starting to suffer from "space cafard", a future version of the cafard which was endemic to the old French Foreign Legion. The crew is heading for shore leave at Starbase 12, when to their disgust they are abruptly ordered to check out a distress call in a boondocks solar system.

About this time Lieutenant Sulu's pet rat Mickey escapes. Later a random crew member chuckles that he just saw Mickey in the corridor, and the funny rat looked like it was dancing. Both McCoy and Sulu turn the color of library paste. McCoy bolts back to Sick Bay while Sulu explains that dancing was a symptom of a rat who had Bubonic Plague. Egads.

The rat leads the crew on a merry chase over the next few weeks, while McCoy worriedly tells Captain Kirk that Bubonic Plague is so ancient that the medical records do not list the cure. Finally they give up on half measures, put the entire crew in space suits, and flood the Enterprise with poison gas. Lieutenant Uhuru writes "The Ballad of Mickey the Space Rat" and performs it for the crew.

The valiant crew then successfuly completes the mission. Space cafard starts setting in again. And suddenly Mickey reappears, dancing away.

The crew freaks out, grimly determined that they are not going to spend their shore leave quarantined on board. A level by level search finally corners Mickey, who is shot by about thirteen phaser-bolts simultaneously. His body is vaporized.

Privately, Dr. McCoy comes clean to Captain Kirk. Mickey did not have the plague, this was all a ruse to fight space cafard. McCoy taught Mickey how to dance, and held him in an oxygen tent while the ship was being gassed. And yes, the medical records do contain the cure for Bubonic Plague, you fell for it Captain.
Plague Ship by Andre Norton
This is the second novel of Norton's Solar Queen series about the dangerous uncertain life of an interstellar free trader, living in the shadows of the megacorporation trade companies in an hand-to-mouth existence.

Due to events recounted in the prior Solar Queen novel, the free traders were given compensation in the form of another (late) free trader's trade rights to the planet Sargol. The cat-people there have a few odd types of perfume for trade. Not very profitable, certainly nothing to attract the attention of the megacorporations.

However, the dear departed free trader had discovered on his last trip something called Koros gemstones. A small pouch of these beauties had almost caused a riot among the bidding gem merchants at an inner planet trading mart. Incredibly valuable. And more than enough to bring the megacorporations sniffing around.

The traders of the Solar Queen finally manage to obtain some Koros stones, after they discover the cat-people of Sargol love catnip even more that the ship's cat. A representative of the Inter-Solar megacorporation appears, becoming very annoyed to find the Solar Queen. Inter-Solar was hoping to poach some stones before the Queen showed up. The crew of the Queen is suspicious, the I-S man seems to be up to something nefarious.

A few days on the trip back home to Terra, the crew starts falling sick. Headaches, then falling into a coma. They fear it is some sort of plague, but then the medic notices small puncture wounds. The ship's cat does not catch anything, but the captain has a weird pet called a Hoobat (a nightmare combination of crab, parrot and toad). It manages to lure out of hiding some Sargolian chameleon insects with coma-inducing stingers. The Hoobat can make a hypnotic noise (by rubbing its claws together) which attracts the insects. It seems that the last load of perfume wood from Sargol had been seeded with the bugs by the I-S man.

When the Solar Queen leaves hyperspace and approaches Terra, they find that I-S has spread the word far and wide that the free trader is a plague ship, and should be quarantined. At least long enough for I-S to clean Sargol out of all its Koros stones. Hilarity ensues but our heroes manage to triumph over the evil megacoporations.

(ed note: The crew of the commercial freighter starship Tinker rescues another ship imperiled by malfunctioning carbon-dioxide scrubbers. They rescue the crew and the passengers, but it would make repairs so much easier if they could replace the deadly CO2 poisoned air with breathable air.)

Chief Gerheart turned to her counterpart. “How long would it take you to vent and replenish your air?”

“Three or four stans (standard hours). As long as we’re suited up, we can flush it with nitrogen and keep hull pressure without having to worry about vacuum damage.”

Greta grinned. “The Verminator Protocol.”

Green grinned back. “Exactly.”

Periodically ships needed to do a complete fumigation to rid themselves of the odd stowaway vermin that had followed man into space. That was usually done by flushing all the breathable air from the ship and filling it with nitrogen gas, sometimes laced with a fungicide. It was usually done with the ship docked and the crew safely ashore. There wasn’t anything that would prevent it from being used in this situation, so long as the people aboard were suited and supplied with oxygen. The nitrogen would push all the carbon dioxide laden air out and would, in turn, be replaced with a clean mixture.


      A recent run to Zaonia resulted in a tet crab female coming onboard and laying a clutch of eggs. She died at the pincers and palps of her voracious children since she’d already eaten their father. At that point the young went into hiding and began maturing or being eaten by their siblings.

     Luch the steward’s cat, Rockit was in charge of vermin control. Being a young cat he assumed the Profit Rockit was his ship. It was named after him after all. Since the humans had their uses he let them remain. At the moment the situation was developing he entered the lower hold, which was nearly empty. That was why he spotted the tet crab so easily. The other reason was she was an arrogant young crab that considered the ship her property and ate whoever disputed it.
     Rockit attempted a pouncing maneuver, but came up short when four pincers began snapping in his face. The two began circling, Rockit hissing, the crab whistling. The commotion brought Luna, the ship’s dog.

     Luna was an anomaly. The ship already had a cat for pest control and anti-hijacking apps for security. She was really not needed. But, when was a dog ever really needed unless you were herding or hunting? All that mattered was that Skipper the deckhand wanted her and after a great deal of fuss she was allowed to keep Luna.
     Luna still had a lot of puppy in her but was an exceptional dog, even in Rockit’s opinion, considering she’d learned to use the ladders on the ship by herself. Rockit still didn’t think much of her of course since he was a cat.
     Luna saw Rockit and the pinchy thing with many legs circling and went for it. Dogs have an innate loyalty but even their biggest fans admit they have no sportsmanship. Luna came at the thing from the side hoping for a quick kill but the crab had several more eyes and very good peripheral vision and Luna got a pincer clamped onto her muzzle. Her fur saved her from laceration but it still hurt like blazes. She tried shaking the tet crab off and the crab’s pincer caught Rockit by the tail as the cat turned to get out of the way.

     Canine, crustacean, and feline did a sad and painful dance on the deck, like a small tornado with pincers and fur. The commotion brought Skipper and Luch. Luch immediately ran to his cat’s aid and stomped the alien intruder.
     The crab latched onto Luch’s slipper-clad foot with a free pincer. Skipper fled as the steward joined the dance. At this point Captain and Sandoval arrived. Sandoval was the first to climb the ladder to the deck and found herself at floor level with a whirling ball of feet and pincers. She did what any good spacer would do, screamed like a little girl and got the hell out of their way. Captain was next up the ladder and he dodged the falling Second Tier Navigator.

     Captain was a Zaonian and Zaonians don’t knuckle under. This one almost did. Then he heaved himself up onto the deck and began seeking a weapon. That was when Skipper came down the ladder from the upper with Captain’s revolver sidearm. She took careful aim fired and missed completely, the bullet burying itself in a deckplate. Captain grabbed the revolver from her before she could ruin another gravity generator, gripped it by the barrel and attempted to pistol whip the tet crab.

     Tet crabs also don’t knuckle.

(ed note: I will note in passing that holding a sidearm by the barrel and using it as a hammer is an outstanding way to shoot yourself)

     Vermin on ocean going ships is a given. The same will most likely be true of space going ships. Both afford plenty of small dark places to hide and edibles. Unlike terrestrial ocean going rats and roaches any SF pests may have to adapt to the environment and diet of the ship's crew. there's not going to be any fluorine or levo-protein based life on a human ship for example. But then most SF settings ave a lot of planets with compatible environments and biologies. And the player characters thought this was for their convenience. Heh heh.

     On the other hand vermin breed rapidly, otherwise they aren't vermin. A bear rummaging in your pantry isn't vermin, it's an animal encounter. Rapid breeders may adapt quickly as subsequent generations grow in unusual conditions. A good example of this is the flea. Fleas could cover the earth in a month unchecked and breed so rapidly using the same toxins against them for more than a couple of months can result in them becoming immune. Your crew's referred methods of dealing with pests may become useless at the worst time.

     A bear is probably less destructive to a ship than most vermin. Roaches, rats and such can not only make your galley fail a health inspections, they can destroy wiring, including warning sensors. As for fouling a galley think of telling a high-passenger that you all have to eat prepackaged rations on your next trip out because you failed a health inspection.

     There are many and numerous methods of pest control. The Tech Level 0 solution is a cat. Cats are pound for pound very efficient little killers (just ask one). Dogs generally speaking come in a far second, unless your crew is savvy enough to get breeds that were bred for ratting, like terriers. Then again some aliens pests might make a ship's mascot earn hazard pay. Genemodded cats and dogs are also possible. I wouldn't get any pets cybernetic enhancements. I wouldn't trust a cat with laser eyes and a dog wth laser eyes would take its begging to a whole new level. Just step away from the pot roast.

     There are many and numerous poisons and traps doing a web search for pest control can give all manner of devices. Checking out an exterminator's web page could give plenty of ideas and they generally give you cogent reasons why you should leave the pest control to professionals.

     Some starports, of course, will seal and bug bomb your ships for a reasonable rate. Reasonable to the folks who sell you a ton of the most common element in the universe for 500 cr. that is.

     Of course space is not an ocean. One resource spacecraft al have easy access to is vacuum (sometimes the access is too easy but by then the pests are very far down your list of concerns!) Lifting a ship and opening the airlocks is pretty cheap. Of course it requires the crew and any passengers have spacesuits or survival bubbles. Remember you can shove two middle passengers in a survival bubble but high passengers get their own. this also will not likely win you repeat business but in the example above, tet crabs might make a few minutes in a bubble time well spent.

     Vacuum will also get into places poison will not and it pretty much kills everything outright, unless you have some really hardcore pests. Just make sure the cats and dogs are safe as well as any fresh foods or other commodities that will not react well to vacuum, like bottled wine. Also make sure there are no pests hiding out in the pressurized cages and cargo pods.

     A far future sort of pest might be destructive nanites. Heinlein help you. Immune to vacuum, breeds like mad and might have a go at eating everything. You might have to shut everything down and drop an EMP bomb or buy some hunter killer nanites.

     Uncharitable type may note many of these ideas apply to stowaways.

From ALL CREATURES BITEY AND SMALL by Rob Garitta (2017)


Be that as it may, the real peril may not be from macroscopic pests at all. Microorganisms could be much more serious. Even if they were not being carried by plague rats.

If you are lucky the mutant germs are just a new kind of plague.

If you ain't, you might be dealing with the functional equivalent of the Andromeda Strain or Mutant 59: The Plastic Eaters (i.e., a plague capable of destroying all life or all technology on a planet). The medical service may order your spacecraft intercepted with a nuclear warhead, which may or may not help matters.


Gerald was an exobiologist, a student of life off the planet Earth. The flaw, of course, was that there wasn’t any life beyond Earth. Except, of course, such Earth-evolved life that continued to evolve even off planet. Every human being, every plant, every animal brought along to the Settlements carried microscopic life-forms by the billions.

Anywhere humans went, viruses, bacteria, and other microbes, disease-causing and benign, traveled as well. Normal medical practice was enough to keep most of the nasties at bay inside the sealed colonies—but some microbes escaped the domes, tunnels, ships and habitats to the outside environments. Virtually all of them died the moment they left the controlled environment. But a few survived. And of those survivors, a very few managed to reproduce, and evolve, often at a ferocious rate.

Earth-derived microbes lurked in the soil around Martian cities, living off dome leakages of air, moisture and organics; lived inside the rock of mining asteroids, dining on a witches’ brew diet of complex hydrocarbons; lived as mildew-like patches in airlocks all over the Solar System, absorbing air, moisture and bits of organic matter whenever the locks were pressurized, encysting when they went into vacuum.

A divine hand that worked in mysterious and sometimes horrifying ways. For a few, a terrifying few, of the outsider organisms came back inside the domes and the spacecraft. Most such Returnees were wiped out by the drastically different environment, but some readapted to life back inside. That was when terror struck. Hardened by their generations outside air, light and pressure, some Returnee organisms bred hellaciously back inside, carrying in their genes the ability to digest unlikely things. Plastics, metal, resin compounds, semiorganic superconductors. And some of them, ancestors of disease organisms, retained the ability to infect the human body.

There were microorganisms that could cause disease in humans and also eat through pressure suits and air domes from the inside. Or dissolve the superconducting wires of power grids. Or jam valves in fusion systems.

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


If the dire dice of destiny land on you with both sixes down, your vermin infestation might turn out to be a super-vermin infestation. The classic example is the xenomorph from the Alien movie. But in novels, it usually takes the form of rats or something have have mutated to the extent that they actually become intelligent.

With super-vermin, the ship's captain tends to stop thinking about venting the ship to vacuum and more about initiating self-destruct.

The Imperial Starships Lenin and MacArthur travel on a first contact mission to the alien Motie planet. Cruiser MacArthur will do the contacting, the battleship Lenin will allow no aliens anywhere near it and has orders to destroy the MacArthur if it is captured. We will take no chances with the existence of the human race, thank you very much.

The Moties have sub-species. One of them is called the "watchmakers", they are semi-intelligent miniature Moties and are used by Motie engineers as sort of mobile tools. They are very clever and breed like rabbits. I think you can see where this is going.

The MacArthur accepts a breeding pair, who promptly escape and disappear into the duct work. The anti-rat ferrets are worthless and the watchmakers are too good at hiding for humans to find. So the crew vents the entire atmosphere to vacuum and figure the problem is solved. The crew does not realize that watchmakers can make their own pressure-tight hab modules.

It isn't until a few weeks later that Captain Blaine realizes they are still infested with the beasties, who are busy reengineering the entire ship. The crew tries to exterminate the watchmakers with a frontal assault with laser handguns, but are defeated by a combination of watchmaker counter-attack and unexpectedly redesigned ship systems that do not operate quite the way they used to.

The crew is evacuated to the Lenin but are only allowed to board after being strip-searched. Especially after they have to fight off a few animated space suits full of watchmakers. The Lenin destroys the MacArthur, which takes an inordinate amount of time since the watchmakers have drastically improved the MacArthur defensive force fields.

The Motie aliens do not have a problem with watchmakers because [A] their watchmakers are not feral so they can order them around to a limited extent and [B] Moties don't care if their ships are redesigned while in flight.

(ed note: The interstellar grain starship has a rat problem. Worse: the rats near the ship's hull have their germ plasm mutated by cosmic radiation. Over the rat-generations they evolve into intelligence. They live in the between-hull areas of the ship, in tribes with spear and knife level of technology.

Shriek has managed to conquer all the tribes and has become the leader of the rats. His wife Wesel is a telepath, and has managed to read the mind of one of the human crew. This was prophesied as "The End", the Ragnarok of the rats. )

      “Shriek!” Wesel’s voice was grave. “We must return at once to the People. We must warn the People. The Giants are making a sorcery to bring the End."
     “The great, hot light ?”
     "No. But wait! First I must tell you of what I learned. Other wise, you would not believe. I have learned what we are, what the world is. And it is strange and wonderful beyond all our beliefs.
     “What is Outside?” She did not wait for his answer, read it in his mind before his lips could frame the words. “The world is but a bubble of emptiness in the midst of a vast piece of metal, greater than the mind can imagine. But it is not so! Outside the metal that lies outside the Outside there is nothing. Nothing! There is no air.” (the "Outside" is the ship's hull. It is a skin of metal lined with insulation. The nothing is deep space.)
     “But there must be air, at least.”
     “No. I tell you. There is nothing.
     “And the world—how can I find words? Their name for the world is—ship, and it seems to mean something big going from one place to another place. And all of us—Giants and People—are inside the ship. The Giants made the ship.”
     “Then it is not alive ?”
     “I cannot say. They seem to think that it is a female. It must have some kind of life that is not life. And it is going from one world to another world.”
     “And these other worlds?”
     “I caught glimpses of them. They are dreadful, dreadful. We find the open spaces of the Inside frightening—but these other worlds are all open space except for one side.”

(ed note: the "Inside" is the area within the hull, the open spaces are rooms. The rats find the rooms frightening because they live in narrow tunnels they made in the hull insulation. Planets are all open spaces except for the ground)

     “But what are we?” In spite of himself, Shriek at least half believed Wesel's fantastic story. Perhaps she possessed, to some slight degree, the power of projecting her own thoughts into the mind of another with whom she was intimate. "What are we?”
     She was silent for the space of many heartbeats. Then: “Their name for us is—mutants. The picture was … not clear at all. It means that we—the People—have changed. And yet their picture of the People before the change was like the Different Ones before we slew them all.
     “Long and long ago—many hands of feedings—the first People, our parents’ parents’ parents, came into the world. They came from that greater world—the world of dreadful, open spaces. They came with the food in the great Cave-of-Food (grain cargo bay)—and that is being carried to another world (the rat ancestors arrived in grain cargo cannisters loaded into the starship for transport to another planet).
     “Now, in the horrid, empty space outside the Outside there is—light that is not light. And this light—changes persons (space radiation causes mutations). No, not the grown person or the child, but the child before the birth (radiation does not mutate you, it mutates your future offspring). Like the dead and gone chiefs of the People, the Giants fear change in themselves. So they have kept the light that is not light from the Inside.
     “And this is how. Between the Barrier (inner hull) and the Far Outside (space) they filled the space with the stuff in which we have made our caves and tunnels (insulation and radiation shielding). The first People left the great Cave-of-Food, they tunneled through the Barrier and into the stuff Outside. It was their nature. And some of them mated in the Far Outside caves. Their children were—Different.”
     “That is true,” said Shriek slowly. “It has always been thought that children born in the Far Outside were never like their parents, and that those born close to the Barrier were—”
     “Now, the Giants always knew that the People were here, but they did not fear them. They did not know our numbers, and they regarded us as beings much lower than themselves. They were content to keep us down with their traps and the food-that-kills (rat poison). Somehow, they found that we had changed. Like the dead chiefs they feared us then—and like the dead chiefs they will try to kill us all before we conquer them.”
     “And the End?”
     “Yes, the End.” She was silent again, her big eyes looking past Shriek at something infinitely terrible. “Yes,” she said again, “the End. They will make it, and They will escape it. They will put on artificial skins that will cover Their whole bodies, even Their heads (spacesuits), and TheyThey will open huge doors in the … skin of the ship (airlocks), and all the air will rush out into the terrible empty space outside the Outside. And all the People will die.”
     “I must go," said Shriek. “I must kill the Giants before this comes to pass."
     “No! There was one hand of Giants (five human crew)—now that you have killed Fat-Belly there are four of them left. And they know, now, that they can be killed. They will be watching for you.
     “Do you remember when we buried the People with the sickness? That is what we must do to all the People. And then when the Giants fill the world with air again from their store we can come out.” (the insulating foam will expand in the vacuum and may trap pockets of air that the rats can survive in until pressure is restored)

(ed note: a few rats survive the depressurization, but are later killed by the great, hot light. Shriek manages to kill all but one of the humans. The sole survivor realizes that they have a Rise of the Planet of the Apes situation on their hands, and dives the ship into a nearby sun in order to save humanity)

From GIANT KILLER by A. Bertram Chandler (1945)
      “It’s more than a legend," said Sam Halden, biologist. The reaction was not unexpected — non-humans tended to dismiss the data as convenient speculation and nothing more. “There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel—and yet each planetary race can interbreed with a minimum of ten others! That’s more than a legend—one hell of a lot more!”
     “It is impressive,” admitted Taphetta. “But I find it mildly distasteful to consider mating with someone who does not belong to my species.”
     “That’s because you’re unique,” said Halden. “Outside of your own world, there’s nothing like your species, except superficially, and that’s true of all other creatures, intelligent or not, with the sole exception of mankind. Actually, the four of us here, though it’s accidental, very nearly represent the biological spectrum of human development.
     “Emmer, a Neanderthal type and our archeologist, is around the beginning of the scale. I’m from Earth, near the middle, though on Emmer’s side. Meredith, linguist, is on the other side of the middle. And beyond her, toward the far end, is Kelburn, mathematician. There’s a corresponding span of fertility. Emmer just misses being able to breed with my kind, but there’s a fair chance that I’d be fertile with Meredith and a similar though lesser chance that her fertility may extend to Kelburn.”
     Taphetta rustled his speech ribbons quizzically. “But I thought it was proved that some humans did originate on one planet, that there was an unbroken line of evolution that could be traced back a billion years.”
     “You’re thinking of Earth,” said Halden. “Humans require a certain kind of planet. It’s reasonable to assume that, if men were set down on a hundred such worlds, they’d seem to fit in with native life-forms on a few of them. That’s what happened on Earth; when Man arrived, there was actually a manlike creature there. Naturally our early evolutionists stretched their theories to cover the facts they had.
     “But there are other worlds in which humans who were there before the Stone Age aren’t related to anything else there. We have to conclude that Man didn’t originate on any of the planets on which he is now found. Instead, he evolved elsewhere and later was scattered throughout this section of the Milky Way.”
     “And so, to account for the unique race that can interbreed across thousands of light-years, you’ve brought in the big ancestor,” commented Taphetta dryly. “It seems an unnecessary simplification.”
     “Can you think of a better explanation?” asked Kelburn. “Something had to distribute one species so widely and it’s not the result of parallel evolution not when a hundred human races are involved, and only the human race.”

(ed note: from old Big Ancestor ruins they figure the average height was about forty feet. Which implies that the Big Ancestors used genetic engineering to make themselves into six-foot tall human colonists.)

     “You’ve heard of the adjacency mating principle?” asked Sam Halden.
     “Vaguely. Most people have if they’ve been around men.”
     “We’ve got new data and are able to interpret it better. The theory is that humans who can mate with each other were once physically close. We’ve got a list of all our races arranged in sequence. If planetary race F can mate with race E back to A and forward to M, and race G is fertile only back to B, but forward to O, then we assume that whatever their positions are now, at once time G was actually adjacent to F, but was a little further along. When we project back into time those star systems on which humans existed prior to space travel, we get a certain pattern. Kelburn can explain it to you.”
     Kelburn went to the projector. “It would be easier if we knew all the stars in the Milky Way, but though we’ve explored only a small portion of it, we can reconstruct a fairly accurate representation of the past.”
     He pressed the controls and stars twinkled on the screen. “We’re looking down on the plane of the Galaxy. This is one arm of it as it is today and here are the human systems.” He pressed another control and, for purposes of identification, certain stars became more brilliant. There was no pattern, merely a scattering of stars. “The whole Milky Way is rotating. And while stars in a given region tend to remain together, there’s also a random motion. Here’s what happens when we calculate the positions of stars in the past.”
     Flecks of light shifted and flowed across the screen. Kelburn stopped the motion.
     “Two hundred thousand years ago,” he said.
     There was a pattern of the identified stars. They were spaced at fairly equal intervals along a regular curve, a horseshoe loop that didn’t close, though if the ends were extended, the lines would have crossed.
     Taphetta rustled. “The math is accurate?”
     “As accurate as it can be with a million-plus body problem.”
     “And that’s the hypothetical route of the unknown ancestor?”
     “To the best of our knowledge,” said Kelburn. “And whereas there are humans who are relatively near and not fertile, they can always mate with those they were adjacent to two hundred thousand years ago!”
     “The adjacency mating principle. I’ye never seen it demonstrated,” murmured Taphetta, flexing his ribbons. “Is that the only era that satisfies the calculations?”
     “Plus or minus a hundred thousand years, we can still get something that might be the path of a spaceship attempting to cover a representative section of territory,” said Kelburn. “However, we have other ways of dating it. On some worlds on which there are no other mammals, we’re able to place the first human fossils chronologically. The evidence is sometimes contradictory, but we believe we’ve got the time right.”
     Taphetta waved a ribbon at the chart. “And you think that where the two ends of the curve cross is your original home?”
     “We think so,” said Kelburn. “We’ve narrowed it down to several cubic light-years — then. Now it’s far more. And, of course, if it were a fast-moving star, it might be completely out of the field of our exploration. But we’re certain we’ve got a good chance of finding it this trip."

     “Hydroponics is your job. There’s nothing I can do.” Halden paused thoughtfully. “Is there something wrong with the plants?”
     “In a way, I guess, and yet not really.”
     “What is it, some kind of toxic condition?”
     “The plants are healthy enough, but something’s chewing them down as fast as they grow.”
     “Insects? There shouldn’t be any, but if there are, we’ve got sprays. Use them.”
     “It’s an animal,” said Firmon. “We tried poison and got a few, but now they won’t touch the stuff. I had electronics rig up some traps. The animals seem to know what they are and we’ve never caught one that way.”
     Halden glowered at the man. “How long has this been going on?”
     “About three months. It’s not bad; we can keep up with them.” It was probably nothing to become alarmed at, but an animal on the ship was a nuisance, doubly so because of their pilot.
     “Tell me what you know about it,” said Halden.
     “They’re little things.” Firmon held out his hands to show how small. “I don’t know how they got on, but once they did, there were plenty of places to hide.” He looked up defensively. “This is an old ship with new equipment and they hide under the machinery. There’s nothing we can do except rebuild the ship from the hull inward.”
     Firmon was right. The new equipment had been installed in any place just to get it in and now there were inaccessible corners and crevices everywhere that couldn’t be closed off without rebuilding. They couldn’t set up a continuous watch and shoot the animals down because there weren’t that many men to spare. Besides, the use of weapons in hydroponics would cause more damage to the thing they were trying to protect than to the pest. He’d have to devise other ways.

     He looked from Halden to Emmer and back again. “The hydroponics tech tells me you’re contemplating an experiment. I don’t like it.”
     Halden shrugged. “We’ve got to have better air. It might work.”
     “Pests on the ship? It’s filthy! My people would never tolerate it!”
     “Neither do we.”
     The Ribboneer’s distaste subsided. “What kind of creatures are they?”
     “I have a description, though I’ve never seen one. It’s a small four-legged animal with two antennae at the lower base of its skull. A typical pest.”
     Taphetta rustled. “Have you found out how it got on?”
     “It was probably brought in with the supplies,” said the biologist. “Considering how far we’ve come, it may have been any one of a half a dozen planets. Anyway, it hid, and since most of the places it had access to were near the outer hull, it got an extra dose of hard radiation, or it may have nested near the atomic engines; both are possibilities. Either way, it mutated, became a different animal. It’s developed a tolerance for the poisons we spray on plants. Other things it detects and avoids, even electronic traps.”
     “Then you believe it changed mentally as well as physically, that it’s smarter?”
     “I’d say that, yes. It must be a fairly intelligent creature to be so hard to get rid of. But it can be lured into traps, if the bait’s strong enough.”

(ed note: They finally catch a few of the vermin chewing on the hydroponics plants by using traps baited with tiny knives just the right size for vermin's hands with opposable thumbs. The vermin were not interested in other bait.)

     Clumsy, but because it had a thumb, it could handle such tools as a knife.
     He had made an error there. He had guessed the intelligence, but he hadn’t known it could use the weapon he had put within reach. A tiny thing with an inchlong knife was not much more dangerous than the animal alone, but he didn’t like the idea of it loose on the ship.
     The metal knife would have to be replaced with something else. Technicians could compound a plastic that would take a keen edge for a while and deteriorate to a soft mass in a matter of weeks. Meanwhile, he had actually given the animal a dangerous weapon—the concept df a tool. There was only one way to take that away from them, by extermination. But that would have to wait.
     Fortunately, the creature had a short life and a shorter breeding period. The actual replacement rate was almost neglible. In attaining intelligence, it had been short-changed in fertility and, as a consequence, only in the specialized environment of this particular ship was it any menace at all.
     They were lucky; a slightly higher fertility and the thing could threaten their existence. As it was, the ship would have to be deverminized before it could land on an inhabited planet.

(ed note: They finally find the origin planet of the Big Ancestor. It is deserted, the cities are empty, all the possessions and artifacts are missing. They do find a document. After lots of computer work the document is translated. The crew assembles to listen to the translation.)

     The translator coughed, stuttered and began.
     “We have purposely made access to our records difficult. If you can translate this message, you’ll find, at the end, instructions for reaching the rest of our culture relics. As an advanced race, you’re welcome to them. We’ve provided a surprise for anyone else.
     “For ourselves, there’s nothing left but an orderly retreat to a place where we can expect to live in peace. That means leaving this Galaxy, but because of our life span, we’re capable of it and we won’t be followed.”
     “At the time we left,” the message continued, “we found no other intelligent race, though there were some capable of further evolution. Perhaps our scout ships long ago met your ancestors on some remote planet. We were never very numerous, and because we move and multiply so slowly, we are in danger of being swept out of existence in the foreseeable future. We prefer to leave while we can. The reason we must go developed on our own planet, deep beneath the cities, in the underworks, which we had ceased to inspect because there was no need to. This part was built to last a million generations, which is long even for us.”
     Emmer sat upright, annoyed at himself. “Of course! There are always sewers and I didn’t think of looking there!”
     “In the last several generations, we sent out four expeditions, leisurely trips because we then thought we had time to explore thoroughly. With this planet as base of operations, the successive expeditions fanned out in four directions, to cover the most representative territory.”
     “After long preparation, we sent several ships to settle one of the nearer planets that we’d selected on the first expedition. To our dismay, we found that the plague was there—though it hadn’t been on our first visit!”
     Halden frowned. They were proving themselves less and less expert biologists. And this plague there had to be a reason to leave, and sickness was as good as any—but unless he was mistaken, plague wasn’t used in the strict semantic sense. It might be the fault of the translation.
     “The colonists refused to settle: they came back at once and reported. We sent out our fastest ships, heavily armed. We didn’t have the time to retrace our path completely, for we’d stopped at innumerable places. What we did was to check a few planets, the outward and return parts of all four voyages. In every place, the plague was there, too, and we knew that we were responsible.
     “We did what we could. Exhausting our nuclear armament, we obliterated the nearest planets on each of the four spans of our journeys.”
     “I wondered why the route came to an end,” crinkled Taphetta, but there was no comment, no answer.
     “We reconstructed what had happened. For a long time, the plague had lived in our sewers, subsisting on wastes. At night, because they are tiny and move exceedingly fast, they were able to make their way into our ships and were aboard on every journey. We knew they were there, but because they were so small, it was difficult to dislodge them from their nesting places. And so we tolerated their existence.”
     They weren’t so smart,” said Taphetta. “We figured out that angle long ago. True, our ship is an exception, but we havn’t landed anywhere, and won’t until we deverminize it.”
     “We didn’t guess that next to the hull in outer space and consequently exposed to hard radiation,” the message went on, “those tiny creatures would mutate dangerously and escape to populate the planets we landed on. They had always been loathsome little beasts that walked instead of rolling or creeping, but now they became even more vicious, spawning explosively and fighting with the same incessant violence. They had always harbored diseases which spread to us, but now they’ve become hothouses for still smaller parasites that also are able to infect us. Finally, we are now allergic to them, and when they are within miles of us, it is agony to roll or creep.”
     Taphetta looked around. “Who would have thought it? You were completely mistaken as to your origin.” Kelburn was staring vacantly ahead, but didn’t see a thing. Meredith was leaning against Halden; her eyes were closed. “The woman has finally chosen, now that she knows she was once vermin,” clicked the Ribboneer. “But there are tears in her eyes.”
     “The intelligence of the beast has advanced slightly, though there isn’t much difference between the highest and the lowest — and we’ve checked both ends of all four journeys. But before, it was relatively calm and orderly. Now it is malignantly insane.”

From BIG ANCESTOR by F. L. Wallace (1954)

(ed note: A dreaded Qul-En alien scout is one of many searching for a source of a hormone needed by the Qul-En race. It lands on Terra, and quickly determines that the hormone is common in Terran mammals in general, and in human brains in particular. The scout roams a remote area in a vehicle disguised as a mountain lion, killing and dissecting animals. It soon determines that Terra will be a prime spot to harvest human beings to extract the needed hormone from their brains.

Unfortunately for the scout, like an idiot it left the door of its flying saucer open, letting the bugs in...)

For a time it did; there was certainly no disturbance at the ship. The small silvery vessel was safely hidden. There was a tiny, flickering light inside—the size of a pin-point—which wavered and changed color constantly where a sort of tape unroled before it. It was a recording device, making note of everything the roaming pseudo-mountain-lion’s eyes saw and everything its microphonic ears listened to. There was a bank of air-purifying chemical which proceeded to regenerate itself by means of air entering through a small ventilating slot. It got rid of carbon dioxide and stored up oxygen in its place, in readiness for further voyaging.

Of course, ants explored the whole outside of the space-vessel, and some went inside through the ventilator opening. They began to cart off some interesting if novel foodstuff they found within. Some very tiny beetles came exploring, and one variety found the air-purifying chemical refreshing. Numbers of that sort of beetle moved in and began to raise large families. A minuscule moth, too, dropped eggs lavishly in the nest-like space in which the Qul-En explorer normally reposed during space-flight. But nothing really happened.

The Qul-En in the lion shape had been vastly pleased to find the sought-for hormone in another animal besides a mountain lion. The dissection job was a perfect anatomical demonstration; no instructor in anatomy could have done better, and few neuro-surgeons could have done as well with the brain. It was, in fact, a perfect laboratory job done on a flat rock in the middle of a sheep-range, and duly reproduced on tape by a flickering, color-changing light. The reproduction, however, was not as good as it should have been, because the tape was then covered by small ants who had found its coating palatable and were trying to clean it off.

This time it wasn’t a rabbit; it was a coyote. It had been killed and most painstakingly taken apart to provide at a glance all significant information about the genus canis, species latrans, in the person of an adult male coyote. It was a most enlightening exhibit; it proved conclusively that there was a third type of animal, structurally different from both mountain-lions and rabbits, which had the same general type of nervous system, with a mass of nerve tissue in one large mass in a skull, which nerve-tissue contained the same high percentage of the desired hormone as the previous specimens. Had it been recorded by a tiny colored flame in the hidden ship—the flame was now being much admired by small red bugs and tiny spiders—it would have been proof that the Qul-En would find ample supplies on Earth of the complex hormone on which the welfare of their race now depended.

This was dictated to the pin-point flame, and the flame faithfully wavered and changed color to make the record. But the tape did not record it; a rather large beetle bad jammed the tape-reel. It was squashed in the process, but it effectively messed up the recording apparatus. Even before the tape stopped moving, though, the record had become defective; tiny spiders had spun webs, earwigs got themselves caught. The flame, actually, throbbed and pulsed restlessly in a cobwebby coating of gossamer and tiny insects. Silverfish were established in the plastic lining of the Qul-En ship; beetles multiplied enormously in the air-refresher chemical; moth-larvae already gorged themselves on the nest-material of the intrepid explorer outside. Ants were busy on the food-stores. Mites crawled into the ship to prey on their larger fellows, and a praying-mantis or so had entered to eat their smaller ones. There was an infinite number of infinitesimal flying things dancing in the dark; larger spiders busily spun webs to snare them, and flies of various sorts were attracted by odors coming out of the ventilator opening, and centipedes rippled sinuously inside...

Then the mountain-lion, which was not a mountain-lion, went bounding through the night toward its hidden ship.

Within an hour, it clawed away the brush from the exit-port, crawled inside, and closed the port after it. As a matter of pure precaution, it touched the “take-off” control before it even came out of its vehicle.

The ventilation-opening closed—very nearly. The ship rose quietly and swiftly toward the skies. Its arrival had not been noted; its departure was quite unsuspected.

It wasn’t until the Qul-En touched the switch for the ship’s system of internal illumination to go on that anything appeared to be wrong. There was a momentary arc, and darkness. There was no interior illumination; ants had stripped insulation from essential wires. The lights were shorted. The Qul-En was bewildered; it climbed back into the mountain-lion shape to use the infrared-sensitive scanning-cells.

The interior of the ship was a crawling mass of insect life. There were ants and earwigs, silverfish and mites, spiders and centipedes, mantises and beetles. There were moths, larvae, grubs, midges, gnats and flies. The recording-instrument was shrouded in cobweb and hooded in dust which was fragments of the bodies of the spiders’ tiny victims. The air-refresher chemicals were riddled with the tunnels of beetles. Crickets devoured plastic parts of the ship and chimed loudly. And the controls—ah! the controls! Insulation stripoed of here; brackets riddled or weakened or turned to powder there. The ship could rise, and it did. But there were no controls at all.

The Qul-En went into a rage deadly enough to destroy the insects of itself. The whole future of its race depended on the discovery of an adequate source of a certain hormone. That source had been found. Only the return of this one small ship fifteen feet in diameter—was needed to secure the future of a hundred-thousand-year-old civilization. And it was impeded by the insect-life of the planet left behind! Insect-life so low in nervous organization that the Qul-En had ignored it!

The ship was twenty thousand miles out from earth when the occupant of the mountain-lion used its ray-beam gun to destroy all the miniature enemies of its race. The killing beam swept about the ship. Mites, spiders, beetles, larvae, silverfish and flies—everything died. Then the Qul-En crawled out and began to make repairs, furiously. The technical skill needed was not lacking; in hours, this same being had made a perfect counterfeit of a mountainiion to serve it as a vehicle. Tracing and replacing gnawed-away insulation would be merely a tedious task. The ship would return to its home planet; the future of the Qul-En race would be secure. Great ships, many times the size of this, would flash through emptiness and come to this planet with instruments specially designed for collecting specimens of the local fauna. The cities of the civilized race would be the simplest and most ample sources of the so desperately needed hormone, no doubt. The inhabitants of even one city would furnish a stop-gap supply. In time—why—it would become systematic. The hormone would be gathered from this continent at this time, and from that continent at that, allowing the animals and the civilized race to breed for a few years in between collections. Yes...

The Qul-En worked feverishly. Presently it felt a vague discomfort; it worked on. The discomfort increased; it could discover no reason for it. It worked on, feverishly...

Out in space, the silvery ship suddenly winked out of existence. Enough of its circuits had been repaired to put it in overdrive. The Qul-En was desperate, by that time. It felt itself growing weaker, and it was utterly necessary to reach its own race and report the salvation it had found for them. The record of the flickering flame was ruined. The Oul-En felt that itself was dying. But if it could get near enough to any of the planetary systems inhabited by its race, it could signal them and all would be well.

Moving ever more feebly, the Qul-En managed to get lights on within the ship again. Then it found what it considered the cause of its increasing weakness and spasmodic, gasping breaths. In using the killing-ray it had swept all the interior of the ship. But not the mountain-lion shape. Naturally! And the mountain-lion shape had killed specimens and carried them about. While its foreleg flamed, it had even rolled on startled, stupid sheep. It had acquired fleas—perhaps some from Salazar—and ticks. The fleas and ticks had not been killed; they now happily inhabited the Qul-En.

The Qul-En tried desperately to remain alive until a message could be given to its people, but it was not possible. There was a slight matter the returning explorer was too much wrought up to perceive, and the instruments that would have reported it were out of action because of destroyed insulation. When the ventilation-slit was closed as the ship took off, it did not close completely; a large beetle was in the way. There was a most tiny but continuous leakage of air past the crushed chitinous armor. The Qul-En in the ship died of oxygen-starvation without realizing what had happened, just as human pilots sometimes black out from the same cause before they know what is the matter. So the little silvery ship never came out of overdrive. It went on forever, or until its source of power failed.

The fleas and ticks, too, died in time; they died very happily, very full of Qul-En body-fluid. And they never had a chance to report to their fellows that the Qul-En were very superior hosts.

From NOBODY SAW THE SHIP by Murray Leinster (1950)

Temperature Regulation

NASA directs that the temperature inside a habitat module should be from 291.5 K to 299.8 K with the nominal temperature 295.2 K. That's 18.4°C ⇒ 22°C ⇒ 26.7°C in metric (and 65°F ⇒ 72°F ⇒ 80°F for those poor benighted folk still using Imperial)

NASA assumes that each astronaut emits 11.82 MJ of heat per day.

This is the job of the Spacecraft Thermal Control Systems.

Temperature inside the habitat module is prevented from getting too cold by hull thermal insulation (to prevent the internal heat from escaping), and by adding heat from sources such as electrical resistance heaters.

Temperature inside the habitat module is prevented from getting too hot by hull thermal insulation (to prevent heat from the sun from entering), and by removing heat using heat radiators. In the TransHab design, it needs approximately 96 kilograms of heat radiators and internal thermal equipment per person.

Radiation Shielding

Radiation shielding has its own separate page.

You want to limit the acute dose of radiation to under 0.1 Grays, and the astronaut career chronic dose to under 4.0 Sieverts.

What this boils down to is supplying the habitat module with a small radiation shielded room called a storm cellar or biowell. It will need radiation shielding to the tune of 500 grams per square centimeter of surface. Since this very expensive in terms of mass, storm cellars will be as small as the designers think they can get away with. With the restriction that all the crew has to physically fit inside, and they might have to shelter there for several days.

If the spacecraft has a fission, fusion, or antimatter power plant or propulsion system, it will require an anti-radiation shadow shield to protect the crew.

If the spacecraft is a combat spacecraft who will have to face radiation from nuclear warheads and particle beam weapons, it is going to require lots of very massy armor.

Artificial Gravity

Supplying artificial gravity has its own separate page.

It is unknown what the minimum amount of artifical gravity is required for health. The only data we have are for 1.0 g on Terra, 437 days in 0.0 g in the ISS, and a few hours at 0.16 g for the Apollo lunar vists. NASA limits astronauts on the International Space Station to 180 day visits.

So, for instance, if the minimum required gravity for health is above 0.4 g, Martian colonists living on the ground will still need regular visits to the centrifuge.

Pretty much all the reports I could find on the subject conclude with something like "I have no idea, more research is needed."

Effects of prolonged microgravity include:

A centrifuge would provide gravity to prevent these dire medical effects, but they are a major pain to attach to a spacecraft.

A possible compromise is the personal centrifuge. This is a centrifuge a few meters long, just big enough for one man to strap in, spin up about 30 RPM, and do some exercises. Yes, this will probably give them severe motion sickness, but it will only be for the duration of the exercise period. This will only help some but not all of the damage done to the body by microgravity.

It is tempting to just forget about spin gravity, and just have everybody float around while the ship is not under thrust. One can be an optimist and assume future medical advances will discovere treatment for all the hideous effects. Marshall Savage suggests electro stimulation therapy of the muscles (Ken Burnside says rocket crewmen will have to wear their "jerk-jammies" when they sleep). One would hope that a medical cure will be found for the nausea induced by free fall, or "drop sickness" (they say that the first six months are the worse).

But the only way to guarantee 100% freedom from all of the nasty medical effects is with full 1 g artificial gravity.

Some of the body’s systems adapt to the environment of space quicker than others. This figure represents how quickly each system adapts to microgravity.

The bottom line is the 1g setpoint, or normal gravity level on Earth for each system. The middle line is called the 0g setpoint, or the level each system obtains once it adapts to microgravity in space. The setpoints for 1g and 0g are different, and so it takes some time to adapt. The top line is called the clinical horizon and it is the point that problems in performance can occur.

As you can see, the neurovestibular system is the first to change. This system is responsible for assessing what direction the body is moving. When this system is not functioning properly, motion sickness can occur. You can see at first, there is a high peak for this system, indicating clinical problems. However, after a few days, this peak disappears, and the system adapts to space travel and has a stable value at the 0g setpoint.

You can see it takes the other systems, such as the muscular system, longer to adapt. On the figure, the muscular system is represented in part by the line labeled “lean body mass”. Lean body mass refers to the mass of the body which is not composed of fat. You can see on the figure that lean body mass eventually reaches a stable value at Og although it does take some time. In addition, the value at Og is less than that at 1g, indicating a loss in lean body mass with space flight.

Some systems, such as bone, don’t adapt to spaceflight. The bone system never reaches a stable value at 0g gravity, but instead continues to climb towards the clinical horizon.

From Marc E. Tischler

Countermeasures thus far have addressed the symptoms in a piecemeal fashion, rather than the underlying cause. For example, high-impact strength training may slow the decline of muscle and bone mass, but it does nothing to mitigate the damage to vision from increased fluid pressure in the eyeballs. Dietary and pharmaceutical countermeasures are fraught with complexity and the risk of unintended side effects — further complicated by the fact that weightlessness itself changes the body’s absorption of and reaction to drugs. Adding calcium to the diet to preserve bone structure is not very effective when the bones are leaching out the calcium they already have due to their lack of mechanical stress. (On Earth, that stress triggers a piezoelectric effect that regulates the growth of bone where it’s needed [Chaffin 1984], [Mohler 1962], [Woodard 1984].) On the contrary, calcium supplements are likely to increase the concentration of calcium in the blood and urinary tract, with a concomitant risk of developing kidney stones.

Artificial gravity via rotation — centrifugation — is the only practical countermeasure that addresses the underlying cause, rather than a subset of symptoms, of the health decline due to gravity deprivation. It’s still not known whether some threshold of gravity less than 1 g would be adequate to stave off the decline. Except for a few hours by a few men on the Lunar surface, there is a dearth of human experience in anything between 0 g and 1 g.

To the extent that a health risk is attributable to gravity deprivation, we don’t need to understand the intricate why’s and how’s to have confidence that restoring gravity will mitigate the risk. Whatever gravity’s effects might be, one can travel from Seattle to Sydney knowing that as long as the gravity in each locale is essentially the same there should be no gravitydeprivation illness or injury.

[Chaffin 1984] Chaffin, Don B.; Andersson, Gunnar B. J. Occupational Biomechanics (p. 25). John Wiley and Sons, Inc.
[Mohler 1962] Mohler, Stanley R. (1962 May). "Aging and Space Travel." In, Aerospace Medicine (vol. 33, p. 594597). Aerospace Medical Association.
[Woodard 1984] Woodard, Daniel; Oberg, Alcestis R. (1984). "The Medical Aspects of a Flight to Mars" (AAS 81239). In P. J. Boston (Ed.), The Case for Mars (AAS Science and Technology Series, vol. 57, p. 173180). American Astronautical Society

Dianne Steiger sucked on her bulb of coffee and considered just how much she hated zero gee. Not for herself, mind. After an adult lifetime spent in spacecraft of one sort or another, a shift from this gravity to that meant little to her. The medical problems caused by zero gee were no great challenge, either, if people paid attention and took care of themselves—and she made quite certain that everybody on a ship of hers took care of themselves. Zero-gee debilitation was to spaceflight as scurvy had been to sea travel five or six hundred years before—completely preventable, and fatal all the same, for anyone fool enough not to take precautions.

It was the headaches that zero gee caused in managing the ship. Terra Nova had been designed for operation either in zero gee or in roll mode, rotating along her long axis to produce artificial gravity via the centrifugal effect. The TN could function either way, but roll mode was preferred for almost everything on board, from drinking coffee to flushing the toilets, from pumping coolant to controlling the ship’s thermal load. There were ways to do everything in no-grav, but most of them were awkward and inconvenient, work-arounds rather than straightforward procedures.

From THE SHATTERED SPHERE by Roger MacBride Allen (1994)

Closed Ecological Systems

Remember the fundamental rule of rocket design: Every Gram Counts.

The spacecraft will have to lug along inconveniently large masses of air, food, and water ("consumables") so that the astronauts can live. And if the ship runs out while in a remote location, the crew will be reduced to a castaways in a lifeboat situation drawing straws to see who dies. With the added constraint that castaways in a lifeboat at least have unlimited access to breathable air. The fact that consumables run out at all will limit the duration of any given mission.

Which explains NASA's burning interest in Closed Ecological Life Support Systems (CELSS). In theory the only input such a system needs is energy, either sunlight or some power source to run grow lights. The advantages are:

  1. The astronauts will have air, food, and water forever (or until the equipment breaks down or the energy input stops)
  2. After a certain mission duration, it will be cheaper (in terms of mass) to use a CELSS instead of transporting consumables. With a primitive CELSS this happens at about 145 days, increasing the efficiency will bring the break-even duration point lower. The mass of the CELSS is constant regardless of mission duration, the mass of consumables goes up with mission duration.

The main functions of a CELSS are:

  1. Turn astronaut's exhaled carbon dioxide into oxygen
  2. Turn astronaut poop and table scraps into food
  3. Turn astronaut pee and washing wastewater into drinkable water

The current lines of research focus on doing this the same way Terra's ecosystem does: by using plants. In order to make the CELSS hyper-efficient they have to use hyper-efficient plants. Which explains the focus on algae.

Currently the state of the art is nowhere near achieving a 100% efficient CELSS. But an efficiency of over 75% or so would be a huge help. Sometimes a sub-100% system is called a Controlled Ecological Life Support Systems. The system might also be partial, such as a system which can 100% recycle carbon dioxide into oxygen, but cannot recycle food at all.

In NASA jargon, a closed environment life support system based on algae is called a "yoghurt box", one based on hydroponic leafy plants is called a "salad machine", and one based on a fish farm is called a "sushi maker".

Problems with creating and maintaining a balanced CELSS include carefully controlling the amount of plants consuming carbon dioxide (so they don't gobble more CO2 than the astronauts can produce, resulting in plant death from asphyxiation), and small-closed-loop-ecology buffering problems. The latter means that the smaller your CELSS system is, the more rapid and violent the results from tiny changes. With a closed-loop ecology the size of Terra, tiny changes can take months to years to show any effects, and those will be mild. With a small spacecraft CELSS, tiny changes can cause immediate and drastic effects.

Since maintaining the balance of a CELSS is so tricky, it will be a major undertaking to keep things stable if the number of crew members changes. If the number goes down (by a group on a landing mission the the Martian surface, or by crew casualties) the amount of plants will have to be cut back. Adding new crew is more of a problem. Leafy plants take time to grow to useful size when increasing square meters of cultivation. Algae is less of a problem since single celled plants multiply at a speed that puts rabbits to shame. It will probably be only a few hours to grow the biomass of algae enough to accommodate the new crew.

Another concern is the shipboard supply of phosphorus and nitrogen, since these are biological bottlenecks.

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

Growing Plants

Terra's ecosystem fundamentally works by plants feeding animals while the animals feed the plants. Pretty much all spacecraft CELSS system try to utilize plants to feed the astronauts. Replacing plants with something else seems like a silly attempt to re-invent the wheel. Why do all that work when Mother Nature has already done it for you, for free?

The plants ingest water, carbon dioxide, sunlight, and some trace elements. Using Mother Nature's photosynthesis process, the plants output carbohydrates and oxygen. The astronauts consume plant carbohydrates and oxygen. Using human digestion, the human body is nourished, while producing water, carbon dioxide, and some trace elements. If you can balance the system, it will keep spinning as long as there is sunlight available.

Photosynthesis essentially splits water into hydrogen and oxygen, spits out the oxygen, and fuses hydrogen and carbon dioxide to form carbohydrates.

According to Chris Wolfe, NASA's best estimate is that the amount of leafy plants needed to handle one astronaut's carbon dioxide exhalation will produce only half of that astronaut's food. This is a problem. If the CELSS is producing all of the crew's food, it will have twice as many plants as needed, which will rapidly deplete the atmosphere of carbon dioxide, which will suffocate all the plants. It will also overproduce oxygen, but that can be extracted from the air and put into tanks for latter breathing, for rocket oxidizer, or exported and sold.

The solution is to recover the carbon trapped in the non-edible parts of the plants harvested for food.

The easiest way is to burn those parts and feed the generated carbon dioxide to hydroponics. The ash will contain other nutrients. Another solution is to feed the leftovers to a supercritical water oxidation unit and let it generate the carbon dioxide.

For CELSS uses, plants are generally grown by using some species of soil-less cultivation. Using actual soil to grow plants, with all of its active cultures and other messy ingredients, is far to unreliable to use in a life-or-death system.

Plants require light in order to perform photosynthesis, but using direct sunlight is a problem. First off you'll have to filter out ultraviolet and other frequencies harmful to plants. A transparent window allowing direct sunlight to illuminate the plants will also allow deadly solar storm radiation to fry them to a crisp. Granted plants tolerate up to 1 Sievert per year, but lets be reasonable here. There ain't no such thing as transparent radiation shielding (as yet).

In theory a shielded shutter will protect the plants from solar storms, but it is yet another possible point of failure. This is unacceptable if you are relying upon your plants to allow the crew to keep on breathing. If the storm detector fails, if the shutter actuators fail, if the crew forget to close manual shutters, all of these mean death by asphyxiation.

A fiber optic pipe fed with filtered sunlight and containing numerous bends to defeat radiation might work. But then if the spacecraft moves further away from Sol than Terra's orbit, the intensity of sunlight drops off rather alarmingly due to the inverse square law. That moron Freeman Lowell took far too long to figure this out in the movie Silent Running.

When you figure in that plants can only use certain wavelengths of sunlight, you might as well give up and use artificial grow-lights. LEDs are best, due to their relatively low waste heat. Feed the LEDs with electricity from the power generator of your choice.

The wavelengths used by photosynthesis are called photosynthetically-active radiation (PAR). They lie in a band from 400 to 700 nanometers, more or less the visible-light spectrum. Chlorophyll, the most abundant plant pigment, is most efficient in capturing red and blue light. This is why plant leaves appear yellowish-green to our eyesight, the chlorophyll doesn't eat those wavelengths so they spit them out. PAR is usually measured in bizarre units of "µmol photons m−2s−1" because photosynthesis is a quantum mechanical process (i.e., a bizarre process).

According to Chris Wolfe, most plants flourish under 26 mol PAR per square meter per day (26,000,000 µmol PAR/m2/d). Assuming that 12 hours (43,200 seconds) of the day are daylight and 12 hours are nightime, this means the plants are enjoying about 601 µmol PAR per square meter per second (µmol m−2s−1, the negative exponents are a cute way of saying "per" or "divided by").

LEDs can produce about 1.7 µmol PAR per watt-second or 6,120 µmol PAR per watt-hour. Supplying 601 µmol m−2s−1 will require about 354 watts (601/1.7 = 354) per square meter.

In other words, your hydroponics LED lights are going to need about 354 watts of electricity per square meter of hydroponic plants, for 12 hours out of every day. Certain plants require different amounts of mols PAR per square meter, and different numbers of illumated hours per day, but this is a good back-of-the-envelope value. Lettuce and spinach want about 250 µmol m−2s−1 (not 601), while tomatoes and cucumbers can get by on only 100 µmol m−2s−1

If I am reading the reports properly, algaculture requires a wee bit more. Chlorella algae wants 450 µmol PAR/m2, and Spirulina's optimal value is about 120 µmol PAR/m2.

So doing the math, Chlorella's 450 µmol PAR/m2 will need about 265 watts/m2 of LED electricity, while Spirulina needs 71 watts/m2. Since algae is typically cultivated in tubes or tanks, I am unsure how to translate the square meters of illumination into volumes of algae culture. The thickness will not be much, because algae is so good at harvesting photons that is is practically opaque.

In terms of area, I've seen values ranging from 10 to 40 square meters and perhaps 40-160 cubic meters per person. My own spreadsheet based on densely stacked racks comes to 11.5 m² floor space, 22.14 m² growing area and 46.2 m³ volume for one person (2.5 kg per day), but we want to allow for safety and variety. People don't want to eat tomato and potato for three meals a day simply because they are excellent producers. I also want to leave volume for animal production and associated equipment, so let's start with 30 m² floor space and 120 m³ per person. About 75% of that will be lit, or 43.3 m² of grow area. We need half of 354 watts per m² or 7,667 watts per person for lighting. Additional power will be needed for pumps and fans.

The extra area provides reserve supplies of storable food like rice and beans, indulgence crops like coffee (1.62g/day*m²), tea (1.92g/day*m²) or cocoa (0.42g/day*m²) {all require several years to establish}, animal feed, plastic feedstock and extra O2 for export. One cup of coffee requires about 10 grams of grounds; a cup a day would use 6.17m² of floor space.

Life Support

Feeding a person requires about 40m³ of hydroponics volume (including row spacing, aisles, nutrient storage, equipment, seeding areas, etc., etc.). The exact amount varies and can be pushed lower (below 20m³ is my guess) but this is a reasonable number to start with. Plants need light (from LEDs), and hydroponic grow systems need pumps, fans and sensors. This gear collectively eats about 5 kW of electricity per person, nearly all of which ends up as low-grade heat.

That same volume will convert two people's CO2 back into oxygen. This is because most of a plant's dry mass is carbon compounds but only about half of that is food; the rest is waste. That carbon comes from CO2, so crops to feed one person trap a second person's worth of carbon as waste. Fortunately we can simply burn the waste to recover that carbon on demand. This would be done in a pyrolysis unit to form neat little carbon blocks for storage and controlled release; these may even be used as filters before ultimately getting burned to keep the CO2 levels high enough for growth. Since plants and humans have very different 'ideal' atmospheres, CO2 scrubbers (zeolite sorbent beds) will be used to actively move CO2 out of human spaces and into plant spaces.

Nitrogen is a buffer gas; it is inert and allows the oxygen percentage in the atmosphere to be low enough to avoid fires. It's also an important part of amino acids (and thus proteins), and is actively cycled in humans and in plants. Nitrogen gas is very stable, meaning it is hard to convert into active forms like urea or nitrate. Nitrogen fixers like legumes and many bacteria can do the job, plus there are methods of making ammonia and other nitrogen-containing chemicals directly (given enough energy). The active nitrogen compounds in the system are assembled in plants to form proteins, eaten by humans, excreted as waste, separated in a waste processor and converted into hydroponic nutrients to be fed to the plants. Some of it is bound up in plant wastes and is either recovered from there or burned back to nitrogen gas depending on how fancy the recovery system is. Quantities of nitrogen are stored in liquid form to replenish atmosphere (everything leaks). That handles the nitrogen cycle, but note that some of it is unavoidably lost over time and resupply is eventually necessary even with perfect recycling. The same applies to all other volatiles (liquids and gases).

Argon will probably be used as a buffer gas and ion engine propellant since it is readily available on Mars. It doesn't get used in biological processes but otherwise would be used in place of nitrogen for maintaining atmosphere.

The waste processing systems will recover other important nutrients like phosphorus, potassium, calcium, iron, etc., usually as salts that can be used directly as fertilizer after purification. Inputs are wastes, water and energy. Outputs are these salts, clean water, heat and CO2 (for the most part). Water circulates through most of these systems; it is taken up by plant roots and evaporated from leaves, bound up in sugars, eaten, drank and excreted, condensed on cold surfaces, etc. Power consumption is minimal for the baseline (relying heavily on bioremediation and SCWO) but could be higher for more advanced systems.

Humidity and temperature is maintained by the CO2 system, since the air must be dried before it can be filtered properly. Incoming warm, wet 'used' air is cooled and dried, passed through the filter, then heated and moistened to the desired level. The filter regenerates by pumping warm, very dry and very high CO2 air through to the plant sections. Any excess water is sent to waste processing for filtration. This means that the atmosphere system needs active refrigeration and is the primary load on the craft's radiators; it needs to be able to handle the entire heat load of the habitat since only a small amount is lost through the solid metal connections to the rest of the craft. Power consumption is roughly 1 kW per person.

A better use of plant waste would be to make animal feed with it and raise fish and chickens. Food fish have a short enough lifespan that they can be raised inside the radiation shielding water, though breeding pairs would be kept inside the storm shelter. Chicken eggs greatly expand the kinds of foods you can create and would be a big benefit to morale. This kind of microfarming can be done even for a very small population; certainly a ship carrying more than a hundred people would be able to sustain populations of both.


As previously mentioned, plants will probably be grown by using soil-less methods.

There are lots of different types of soil-less cultivation, all based around using water (Hydroponics). Some are suitable for CELSS.

  • Hydroponics: growing plants without live bacterial-infested soil ("salad machine")
    • Solution Culture: no substrate, just nutrient water
      • Static solution culture: plants in jars of still nutrient water
      • Continuous-flow solution culture: flows of nutrient water passing over plant roots
      • Aeroponics: plant roots are in the air, misted with a fog of nutrient water
      • Algaculture: microalgae cells cultivated in either static or continuous flow solutions cultures ("yoghurt box")
    • Medium Culture: using a sterile solid substrate bathed in nutrient water
    • Aquaponics: solution or medium cultures in association with tanks of fish and other sea food ("sushi maker")

Growing leafy plants for food is not as efficient as growing algae or other single-cell plant. But it is quite a bit easier. The basic idea is to grow food plants not in soil, but instead in nutrient filled water or in an inert material bathed in nutrient filled water.

Medium cultures can use all sorts of substrates: rock wool, baked clay pellets, glass waste growstones, coco peat, parboiled rice husks, Perlite, Vermiculite, pumice, sand, gravel, wood fibre, sheep wool, brick shards, and polystyrene packing peanuts have all been used.

The Executive Officer assigned other tasks not directly concerned with formal training. Matt was appointed the ship’s “farmer.” As the hydroponics tanks supply both fresh air and green vegetables to a ship he was responsible for the ship’s air-conditioning and shared with Lieutenant Brunn the tasks of the ship’s mess.

Theoretically every ration taken aboard a Patrol vessel is pre-cooked and ready for eating as soon as it is taken out of freeze and subjected to the number of seconds, plainly marked on the package, of high-frequency heating required. Actually many Patrol officers fancy themselves chefs. Mr. Brunn was one and his results justified his conceit—the Aes Triplex set a good table.

(ed note: microwave ovens had been invented about one year before Heinlein wrote this novel. That is what "high-frequency heading" is referring to.)

Matt found that Mr. Brunn expected more of the “farm” than that the green plants should scavenge carbon dioxide from the air and replace it with oxygen; the mess officer wanted tiny green scallions, fragrant fresh mint, cherry tomatoes, Brussels sprouts, new potatoes. Matt began to wonder whether it wouldn’t have been simpler to have stayed in Iowa and grown tall corn.

When he started in as air-conditioning officer Matt was not even sure how to take a carbon-dioxide count, but shortly he was testing his growing solutions and adding capsules of salts with the confidence and speed of a veteran, thanks to Brann and to spool #62A8134 from the ship’s files—“Simplified Hydroponics for Spaceships, with Growth Charts and Additives Formulae.” He began to enjoy tending his “farm.”

Until human beings give up the habit of eating, spaceships on long cruises must carry about seven hundred pounds of food per man per year. The green plants grown in a ship’s air-conditioner enable the stores officer to get around this limitation to some extent, as the growing plants will cycle the same raw materials—air, carbon dioxide, and water—over and over again with only the addition of quite small quantities of such salts as potassium nitrate, iron sulphate, and calcium phosphate.

The balanced economy of a spaceship is much like that of a planet; energy is used to make the cycles work but the same raw materials are used over and over again. Since beefsteak and many other foods can’t be grown conveniently aboard ship some foods have to be carried and the ship tends to collect garbage, waste paper, and other trash. Theoretically this could be processed back into the cycles of balanced biological economy, but in practice this is too complicated.

Even though turnip greens and such can be used in the jet, the primary purpose of the “farm” is to take the carbon dioxide out of the air. For this purpose each man in the ship must be balanced by about ten square feet of green plant leaf. Lieutenant Brunn, with his steady demands for variety in fresh foods, usually caused Matt to have too much growing at one time; the air in the ship would get too fresh and the plants would start to fail for lack of carbon dioxide to feed on. Matt had to watch his CO2 count and sometimes build it up by burning waste paper or plant cuttings.

Brunn kept a file of seeds in his room; Matt went there one “day” (ship’s time) to draw out Persian melon seeds and set a crop. Bran told him to help himself. Matt rummaged away, then said, “For the love of Pete! Look at this, Mr. Brunn.”

“Huh?” The officer looked at the package Matt held. The outside was marked, “Seeds, melon, Persian jumbo fancy, stock #12-Q4728-a”; the envelope inside read Seed, pansies, giant variegated.”

Brunn shook his head. “Let that be a lesson, Dodson—never trust a stock clerk—or you’ll wind up half way to Pluto with a gross of brass spittoons when you ordered blank spacecharts.”

“What’ll I substitute? Cantaloupe?”

“Let’s grow some watermelon—the Old Man likes watermelon.”

Matt left with watermelon seeds, but he took along the truant pansy seeds.

Eight weeks later he devised a vase of sorts by covering a bowl from the galley with the same sponge-cellulose sheet which was used to restrain the solutions used in his farming, thereby to keep said solutions from floating around the “farm” compartment during free fall. He filled his vase with water, arranged his latest crop therein, and clipped the whole to the mess table as a centerpiece.

Captain Yancey smiled broadly when he appeared for dinner and saw the gay display of pansies. “Well, gentlemen,” he applauded, “this is most delightful. All the comforts of home!” He looked along the table at Matt. “I suppose we have you to thank for this, Mr. Dodson?”

“Yes, sir.” Matt’s ears turned pink.

“A lovely idea. Gentlemen, I move that we divest Mr. Dodson of the plebeian title of ‘farmer’ and designate him Horticulturalist extraordinary.’ Do I hear a second?” There were nine “ayes” and a loud “no” from Commander Miller. A second ballot, proposed by the Chief Engineer, required the Executive Officer to finish his meal in the galley.

Lieutenant Brunn explained the mishap that resulted in the flower garden. Captain Yancey frowned. “You’ve checked the rest of your supply of seeds, of course, Mr. Brunn?”

“Uh, no, sir.”

“Then do so.” Lieutenant Brunn immediately started to leave the table, “—after dinner,” added the Captain. Brunn resumed his place.

“That puts me in mind of something that happened to me when I was ‘farmer’ in the old Percival Lowell—the one before the present one,” Yancey went on. “We had touched at Venus South Pole and had managed somehow to get a virus infection, a sort of rust, into the ‘farm’—don’t look so superior, Mr. Jensen; someday you'll come a cropper with a planet that is new to you!”

“Me, sir? I wasn’t looking superior.”

“No? Smiling at the pansies, no doubt?”

“Yes, sir.”

“Hmmph! As I was saying, we got this rust infection and about ten days out I didn’t have any more farm than an Eskimo. I cleaned the place out, sterilized, and reseeded. Same story. The infection was all through the ship and I couldn’t chase it down. We finished that trip on preserved foods and short rations and I wasn’t allowed to eat at the table the rest of the trip.”

From SPACE CADET by Robert Heinlein (1948)


Algaculture in a spacecraft CELSS is always in the form of growing microalgae, not gigantic macroalgae aka seaweed. Popular food microalgae types include Chlorella and Spirulina.

Algae is cultivated in photobioreactors. These try to hold the algae cultures in thin layers because the little greenies are so good at absorbing the light that any algae that is too deep will get no light at all. The concentration of algae is typically something like 5×108 algae cells per mililiter of water.

In 1965, the Russian CELSS experiment BIOS-3 determined that 8 m2 of exposed Chlorella could remove carbon dioxide and replace oxygen within the sealed environment for a single human (I am assuming this is in a very shallow tray). The official figure for Chlorella oxygen production is 25 to 400 femtoMol O2/cell/hour. If am I doing the math correctly, at a concentration of 5×108 cells/ml, this translates into about 0.0032 kg of O2 produced per hour per liter, and 0.768 kg of O2 produced per day per liter. Since astronauts require 0.835 kg of O2 per day, this implies they would need 1.09 liters of chlorella culture.


In THE MILLENNIAL PROJECT, Marshall Savage sings the praises of Spirulina algae. However, you'd best take the following with a grain of salt. There is often a long distance between the ideal and the real.

Anyway, Spirulina is apparently almost the perfect food, nutritional wise. A pity it tastes like green slime (though Savage maintains that genetic engineering can change the flavor). Spirulina is highly digestible since it contains no cellulose. It is 65% protein by weight and contains all eight essential amino acids in quantities equivalent to meat and milk. It also has almost all the vitamins, with the glaring exception of vitamin C (I guess rocketmen will become "limeys" again). It is also a little sparse on carbohydrates. Savage calculates that it will be possible to achieve production rates of 100 grams (dry weight) of algae per liter of water per day. It breaks down 6 liters of algae water per person, supplying both food and oxygen, while consuming sunlight (or grow-lights), CO2 and sewage. 6 liters of algae water will produce 600 grams of "food" (540 grams is 2500 calories, an average daily food requirement), 600 liters of oxygen, and consume 720 liters of CO2 and an unspecified amount of nutrient salts extracted from sewage. Since food is generally 75% water, 600 grams of dry food will convert into about 2.4 kg of moist food, which compares favorably with the 2.3 kg on the USS Wyoming.

600 liters of oxygen is about 0.8574 kg of oxygen, which is above the NASA requirement of 0.835 kg of oxygen per astronaut per day.

NASA commissioned a study back in 1988 to determine how difficult it would be to cultivate Spirulina as part of a closed ecological life support system.

Dr. John Schilling mentions a possible pitfall:

[Spirulina is] [h]igh in nucleic acid, which means you can only eat about fifty grams per day or you're at risk of gout. And it's going to be really, really, really embarassing if you have to list "gout" as the cause of failure for a space mission.

Dr. John Schilling

There are other things you have to be mindful of when cultivating Spirulina. From the Swedish Medical Center:

Various forms of blue-green algae can be naturally contaminated with highly toxic substances called microcystins.

Some states, such as Oregon, require producers to strictly limit the concentration of microcystins in blue-green algae products, but the same protections cannot be assumed to have been applied to all products on the market. Furthermore, the maximum safe intake of microcystins is not clear, and it is possible that when blue-green algae is used for a long time, toxic effects might build up...

...Blue-green algae can also contain a different kind of highly toxic substance, called anatoxin (ed note: AKA "Very Fast Death Factor").

In addition, when spirulina is grown with the use of fermented animal waste fertilizers, contamination with dangerous bacteria could occur. There are also concerns that spirulina might concentrate radioactive ions found in its environment. Probably of most concern is spirulina's ability to absorb and concentrate heavy metals such as lead and mercury if they are present in its environment. One study of spirulinas grown in a number of locations found them to contain an unacceptably high content of these toxic metals. However, a second study on this topic claims that the first used an unreliable method of analyzing heavy metal content, and concludes that a person would have to eat more than 77 g daily of the most heavily contaminated spirulina to reach unsafe mercury and lead consumption levels.

These researchers, however, go on to suggest that it is not prudent to eat more than 50 g of spirulina daily. The reason they give is that the plant contains a high concentration of nucleic acids, substances related to DNA. When these are metabolized, they create uric acid, which could cause gout or kidney stones. This is of special concern to those who have already had uric acid stones or attacks of gout.

SF writers with an evil turn of mind will see some interesting plot possibilites in these facts. The ship's food supply could become contaminated by an incompetent repair of the algae system utilizing lead pipes, an algae culture supplier with poor quality control, or deliberate sabotage.

Algae Tankage

The advantage of algae is that it can theoretically form a closed ecological cycle. This means that 6 liters of algae water, one human, some equipment, and sunlight can keep the human supplied with food and oxygen forever. Theoretically, of course. 0.006 m3 per person compared to 90 m3 per person is a strong argument for lots of green slime dinners for enlisted Solar Guard rocketmen. Of course the Biosphere II fiasco shows how far we are from actually achieving a closed ecological cycle. Don't forget the 0.25 liters of water per person per day to make up for reclamation losses.

“All right, you two!” broke in Tom good-naturedly. “Enough’s enough! Come on. We’ve got just enough time to run up to the mess hall and grab a good meal before we check the ship.”

“That's for me," said Astro. “I've been eating those concentrates so long my stomach thinks I've turned into a test tube."

Astro referred to the food taken along on space missions. It was dehydrated and packed in plastic containers to save weight and space. The concentrates never made a satisfactory meal, even though they supplied everything necessary for a healthful diet.

From DANGER IN DEEP SPACE by Carey Rockwell (1953)

William Seney points out that as a luxury, some of the algae can be diverted to feed fish such as carp, catfish or tilapia for an occasional treat.

And you'd better keep the algae tanks far from the atomic drive. The last thing you want is for the little green darlings to mutate into something you can't eat. Or worse: something that is really inefficient at producing oxygen.

Christopher Huff begs to differ:

Actually, the algae tanks would make pretty good radiation shielding. "Clean" cultures of the original strain of algae would be easy to carry along to replenish the main tanks if an inedible form did take hold...just stick some packets of dry spores in the radiation shelter. As for the last possibility, a strain that was poor at conversion of CO2 would quickly be out-bred by the better strains. With algae constantly being removed for food, it would quickly be eliminated from the system.

Also, in addition to fish, a small colony of shrimp or crabs could be fed off the algae, providing a bit more variety in the food supply. Clams could also have a place, providing a useful sink for calcium, carbon, and oxygen in their shells as well as helping to process water. A combination of fresh and salt water systems might work out best.

Christopher Huff

There were some figures in a report on a cruder life-support set up written in 1953. This used Chlorella algae, which isn't quite as good as Spirulina since it has an indigestible cellulose cell wall. The figures assume a Chlorella culture density of 55 grams per liter of water and a daily yield of 2.5 grams per liter. Savage's 100 grams per liter sounds a little optimistic, and 2.5 sounds a little pessimistic. The truth is probably somewhere in between.

At a yield of 2.5 g/l, to provide one rocketeer with 500 grams of food (instead of Savage's 600 grams) will require 200 liters of algae culture.

Urine is passed through an absorption tube to remove excess salt (which would kill the algae) but retaining urea and other nitrogen compounds the algae needs. Faeces are irradiated with ultraviolet to kill all bacteria and added to the urine. This is fed to the main algae tank along with pressurized carbon dioxide (previously removed from the air with calcium oxide). A pump sends a flow of algae culture to the growth trays under filtered sunlight. The culture then passes through a centrifugal separator on its way back to the main tank. The separator performs two functions: [1] removing excess gas to maintain a pressure equilibrium with the carbon dioxide injection and [2] periodically harvesting algae for food. Harvest will occur once a day, extracting 500 grams of algae from nine liters of culture per person. The pump will be controlled such that the algae on the average will experience two minutes of sunlight then three minutes in the darkness of the main tank before it starts the cycle anew.

A fresh batch of urine and faeces is added immediately after algae harvest, to give the algae twenty four hours to consume it. So by next harvest there is no human excretions contaminating the food (you hope).

Now for the answer you've been waiting for. Dr. Bowman estimates that the equipment will mass approximately 50 kg, plus 200 kg per man for algae culture. Since the equipment is such a small fraction of the total, mass savings depend upon getting the algae yield higher than 2.5 g/l. Such as Savage's 100 g/l Spirulina with 6 kg per man of algae culture.

Dr. Bowman points out that when one compares an algae system with merely stocking crates of food, the break-even point occurs at a mission of 145 days (about five months). Below this time it takes less mass to bring crates of food, as the mission duration rises above 145 days the algae tanks get more and more attractive.

Growing Meat


Other SF novels have suggested vats of yeast or tissue cultures of meat ("carniculture" or in vitro meat) to supplement food supplies. But unless they can re-cycle wastes from the crew, it seems more efficient to just carry more boxed food.

Currently scientist can only grow tissue cultures as a single sheet of cells, making them thicker will require figuring out how to make them grow blood vessels to nourish all the cells ("vascularization"). But some technicians figure that they can grow lots of meat cell sheets, then laminate the sheet layers together to approximate a slab of meat.

There are researchers exploring several different strategies to make full-blown vascularization. But it ain't easy. Strategies include material functionalization, scaffold design, microfabrication, bioreactor development, endothelial cell seeding, modular assembly, and in vivo systems. See link for details.

The joke name for this process is "In Meatro"

If you are trying a closed cycle with tissue cultures, you will have to deal with the problem of the Food Chain. Typically each higher level of the pyramid has one-tenth the biomass of the one below, for reasons you can read about in the link. What this means is that you will have to feed ten meals worth of algae to the meat tissue culture in order to produce one meal worth of meat. Even on Terra, this is the reason why meat is more expensive than vegetables.

Obviously the food chain effect also applies to diverting some of the algae to fatten up some fish as a special meal.

At least the tissue culture helps increase the meat ratio. For instance, an entire cow is about 40% edible meat. The rest is bones, hooves, hide, and other inedible parts. Tissue cultures would theoretically turn that up to 100% edible meat. Granted the inedible parts can be recycled via supercritical Water Oxidation, but the inefficiency of wasting all that algae food energy on growing inedible bones kills this idea dead. Not that it would have been practical to bring a cow along on your spaceship in the first place.

As a side note, the idea of lab grown in vitro meat has caused some controversy among the vegetarian community. Any person who is vegetarian on the basis of avoiding animal cruelty, should have no objection to eating in vitro meat. But some vegetarians still maintain that one should not eat meat because of Reasons.

Of course things can become a real moral quagmire, as Sir Arthur C. Clarke points out in his disturbing short story The Food of the Gods.

(ed note: "Chicken Little" is a chicken breast meat tissue culture.)

Arielle went to bed, too, but first she stopped off at the sick bay to get patches for her cracked fingernails, then at the galley to get a bite to eat. She had a double helping of protocheese with real garlic from Nels's hydroponic gardens, two algae shakes with energy sticks mixed in for crunch, then, still hungry, she finished with a desert consisting of a half-pound of white-meat sticks from "Chicken Little" — her real-meat ration for a week — sliced into thin strips and hot-cooked with James's secret recipe of herbs and spices.

From ROCHEWORLD by Robert L. Forward. (1990)

You know I admire classical artists like Rembrandt and Bonestell, and don’t care for abstractions or chromodynamics. I’m not very musical. I have a barrack-room sense of humor. My politics are conservative. I prefer tournedos to filet mignon but wish the culture tanks could supply us with either more often. I play a wicked game of poker, or would if there were any point in it aboard this ship.

From TAU ZERO by Poul Anderson (1970)

“What’s it going to be tonight?” Grevan asked, reaching up to guide them in to an even landing.

“Albert II in mushroom sauce,” said Klim. She was a tall, slender blond with huge blue eyes and a deceptively wistful expression. As he grounded the cooker, she put a hand on his shoulder and stepped down. “Not a very original menu, I’ll admit! But there’s a nice dessert anyway. How about sampling some local vegetables to go with Albert?”

“Klim thinks Albert is beginning to look puny again,” Cusat announced. “Probably nothing much to it, but how about coming along and helping us diagnose?”

The Group’s three top biologists adjourned to the ship, with Muscles, whose preferred field was almost-pure mathematics, trailing along just for company. They found Albert II quiescent in vitro—as close a thing to a self-restoring six-foot sirloin steak as ever had been developed.

“He’s quit assimilating, and he’s even a shade off-color,” Klim pointed out, a little anxiously.

They debated his requirements at some length. As a menu staple, Albert was hard to beat, but unfortunately he was rather dainty in his demands. Chemical balances, temperatures, radiations, flows of stimulant, and nutritive currents—all had to be just so; and his notions of what was just so were subject to change without notice. If they weren’t catered to regardless, he languished and within the week perversely died. At least, the particular section of him that was here would die. As an institution, of course, he might go on growing and nourishing his Central Government clients immortally.

They reset the currents finally and, at Cusat’s suggestion, trimmed Albert around the edges. Finding himself growing lighter, he suddenly began to absorb nourishment again at a very satisfactory rate.

“That did it, I guess,” Cusat said, pleased. He glanced at the small pile of filets they’d sliced off. “Might as well have a barbecue now.”

“Run along and get it started,” Grevan suggested. “I’ll be with you as soon as I get Albert buttoned up.”

From THE END OF THE LINE by James H. Schmitz (1951)

Several calves were born, and seemed to be doing well; the biochemistry of Tanith and Khepera were safely alike. Trask had hopes for them. Every Viking ship had its own carniculture vats, but men tired of carniculture meat, and fresh meat was always in demand. Some day, he hoped, kregg-beef would be an item of sale to ships putting in on Tanith, and the long-haired hides might even find a market in the Sword-Worlds.

From SPACE VIKING by H. Beam Piper (1962)

Insect Protein

There is an alternative between eating algae and the daunting task of growing vascularized meat tissue cultures, but you ain't gonna like it.

There are quite a few edible insects that will happily eat algae. Since they are live, they make their own vascularization. They are very efficient at converting algae into insect meat. And a much higher percentage of insect body mass is edible meat.

Yes, most people from western cultures find the thought of eating bugs to be incredibly disgusting. However the astronauts are already drinking recycled urine so it just takes some training. Processing will help, a compressed-protein bar composed of finely ground insects will be easier to eat than a plate full of microwaved bugs with too many legs.

In the following table, the "Algae for 1 kg of animal" is how much algae an entire animal will need to eat in order to increase its weight by one kilogram. "Edible meat" is the percentage of the animal's mass that is edible. "Algae for 1 kg of meat" is how much algae the entire animal will need to eat in order to increase its edible meat mass by one kilogram (i.e., reciprocal of edible meat percent times algae for 1 kg of animal).

You can probably use the "Algae for 1 kg of animal" figure as a ballpark figure for a tissue culture.

Algae to Meat Conversion
AnimalAlgae for
1 kg of animal
Edible meatAlgae for
1 kg of meat
Cow10 kg40%25.0 kg
Pig5 kg55%9.1 kg
Chicken2.5 kg55%4.6 kg
Cricket1.7 kg80%2.1 kg

Data from Edible insects: Future prospects for food and feed security.

If you figure a beef tissue culture requires 10 kg of algae for each new kilogram of beef, the freaking live crickets are still more efficient.

At harvest time, insects are killed by freeze-drying, sun-drying or boiling (in space, exposing them to vacuum probably counts as freeze-drying). They can be processed and consumed in three ways: as whole insects; in ground or paste form; and as an extract of protein, fat or chitin for fortifying food and feed products. Insects are also fried live and consumed, but a deep-fat fryer in microgravity is insanely dangerous. Some species need to have their legs and wings removed before eating.

In practice, extracting insect protein is probably not worth the effort. Needs lots of exotic chemicals and equipment, and reduces the percentage of edible mass. It is easier just to grind them into powder or paste and make bug-burgers.

For more details than you really want to know, read the report.

Science fiction authors could use this as an interesting bit of historical detail. Old-timer spacers can tell tales about back in olden days when they had to eat bugs. You young whipper-snapper spacers have it easy nowadays, what with your vascularized filet mignon tissue cultures.


I was reading the article in Atomic Rockets about growing meat in space where you suggested growing insects as an alternate to lab-grown meat cultures. You use crickets as your example insect. As someone who has raised crickets in captivity I can tell you that there is no way you're going to get a cricket farm in a closed system like a spacecraft. Even a well maintained cricket colony smells like a just-opened bag of chicken feces that has been sitting in the sun.

Go down to a pet store and ask to sniff their crickets if you don't believe me. Those things are absolutely pungent.

Also, crickets are annoying to culture because they eat each other if you're not careful and there's a lot of work that goes into making sure that doesn't happen too much. Plus, they're fast and they jump (and fly!) which makes them hard to keep contained even on earth.

Know what insect is slow moving and has a very mild odor? Cockroaches.

It would thrill me to no end to crack open a paperback one of these days to read about astronauts eating processed cockroach bars. I'm a big fan of cockroaches.

I no longer have a colony of roaches but thinking back to the smell of the colony I'm 95% certain that the only odors were that of decaying paper from the egg cartons and toilet paper rolls I raised the creatures in and the smell of any food I gave them. I raised Blaptica dubia roaches, by the way, because of their inability to climb glass and their lack of sexual behavior at normal room temperature. In case my tank ever broke I would be assured that the subsequent roach infestation would last only a single generation. Also, I could easily throttle the rate that they bred by switching on and off the tank's heater. Male B. dubia roaches have wings, however, and while they do not typically fly they will, apparently, flutter if you pick one up and drop it. I'm not sure how that would work in microgravity. Probably better to choose a species that has no wings at all.

I'll need to think about an ideal roach species for breeding in space, but B dubya is at the top of my list so long as the males don't start flying about in microgravity. A couple factors I would consider is whether or not the roach can cling to glass (so you can open their container without having roach stuck to the lid), whether or not they deposit or carry their egg sacks while they gestate, and whether or not they fly or stink.

From Samantha Davis (2015)


A shmoo is a fictional cartoon creature created by Al Capp, they first appeared in his classic comic strip Li'l Abner in 1948. Shmoos were prolific, required no food (only air), are delicious and nutritious, have no bones or other waste, and are eager to be eaten. (Ironically, they are the greatest menance to humanity ever known. Not because they are bad, but because they are good.)

Oddly enough, shmoos share many common traits with one-celled yeast. Yeast even looks a little like a shmoo. When a yeast cell senses the mating pheromone, it initiate polarized growth towards the mating partner, creating the characteristic outline of a shmoo. The process is called "shmooing", which shows that biologists have a sense of humor. As to the matter of the deliciousness of yeast, see the exerpt from Lucky Starr and the Oceans of Venus below.

The science fiction version of a shmoo is a Frumious Bandersnatch, from Larry Niven's "Known Space" series.

In the real world, left-over brewers' yeast is used to create such foods as Marmite and Vegemite. Even in 1902 people realized that it was a criminal waste to just throw away the huge quantities of perfectly edible yeast protein that was a by-product of making beer. Marmite and Vegemite are still being sold today. Actually in Australia, Vegemite is more or less a food staple.

In science fiction, one occasionally encounters the term "dole yeast". In future societies that have some form of social welfare system for unemployed people, the food given is generally a portion of unpalatable raw yeast, since that is usually the cheapest food available. Single-cell protein is very inexpensive, especially if you grow it on minimally processed sewage.


      He glanced at the menu on a waiter’s chest, and recoiled. “Ye gods. The prices!”
     “This is as expensive as it gets. At the other end is dole yeast, which is free—”
     “—and barely worth it. If you’re down and out it’ll keep you fed, and it practically grows itself."

From PROTECTOR by Larry Niven (1973)
Bigman turned his attention reluctantly to his dessert. The waiter had called it "jelly seeds," and at first the little fellow had regarded the dish suspiciously. The jelly seeds were soft orange ovals, which clung together just a bit but came up readily enough in the spoon. For a moment they felt dry and tasteless to the tongue, but then, suddenly, they melted into a thick, syrupy liquid that was sheer delight.

"Space!" said the astonished Bigman. "Have you tried the dessert?"

"What?" asked Lucky absently.

"Taste the dessert, will you? It's like thick pineapple juice, only a million times better.

Lucky smiled and went on, "Venus is a fairly developed planet. I think there are about fifty cities on it and a total population of six million. Your exports are dried seaweed, which I am told is excellent fertilizer, and dehydrated yeast bricks for animal food."

"Still fairly good," said Morriss. "How was your dinner at the Green Room, gentlemen?"

Lucky paused at the sudden change of topic, then said, "Very good. Why do you ask?"

"You'll see in a moment. What did you have?"

Lucky said, "I couldn't say, exactly. It was the house meal. I should guess we had a kind of beef goulash with a rather interesting sauce and a vegetable I didn't recognize. There was a fruit salad, I believe, before that and a spicy variety of tomato soup."

Bigman broke in. "And jelly seeds for dessert."

Morriss laughed hootingly. "You're all wrong, you know," he said. "You had no beef, no fruit, no tomatoes. Not even coffee. You had only one thing to eat. Only one thing. Yeast!"

"What?" shrieked Bigman.

For a moment Lucky was startled also. His eyes narrowed and he said, "Are you serious?"

"Of course. It's the Green Room's specialty. They never speak of it, or Earthmen would refuse to eat it. Later on, though, you would have been questioned thoroughly as to how you liked this dish or that, how you thought it might have been improved, and so on. The Green Room is Venus's most valuable experimental station."

"I am guessing," said Lucky, "that yeast has some connection with the crime wave on Venus."

"Guessing, are you?" said Morriss, dryly. "Then you haven't read our official reports. I'm not surprised. Earth thinks we are exaggerating here. I assure you, however, we are not. And it isn't merely a crime wave. Yeast, Lucky, yeast! That is the nub and core of everything on this planet."

For a moment they sipped in silence; then Morriss said, "Venus, Lucky, is an expensive world to keep up. Our cities must make oxygen out of water, and that takes huge electrolytic stations. Each city requires tremendous power beams to help support the domes against billions of tons of water. The city of Aphrodite uses as much energy in a year as the entire continent of South America, yet it has only a thousandth the population.

"We've got to earn that energy, naturally. We've got to export to Earth in order to obtain power plants, specialized machinery, atomic fuel, and so on. Venus's only product is seaweed, inexhaustible quantities of it. Some we export as fertilizer, but that is scarcely the answer to the problem. Most of our seaweed, however, we use as culture media for yeast, ten thousand and one varieties of yeast."

Morriss looked soberly at the small Martian and said, "If you wish. Bigman is quite correct in his low opinion of yeast in general. Our most important strains are suitable only for animal food. But even so, it's highly useful. Yeast-fed pork is cheaper and better than any other kind. The yeast is high in calories, proteins, minerals, and vitamins.

"We have other strains of higher quality, which are used in cases where food must be stored over long periods and with little available space. On long space journeys, for instance, so-called Y-rations are frequently taken.

"Finally, we have our top-quality strains, extremely expensive and fragile growths that go into the menus of the Green Room and with which we can imitate or improve upon ordinary food. None of these are in quantity production, but they will be someday. I imagine you see the whole point of all this, Lucky."

"I think I do."

"I don't," said Bigman belligerently.

Morriss was quick to explain. "Venus will have a monopoly on these luxury strains. No other world will possess them. Without Venus's experience in zymoculture.

"In what?" asked Bigman.

"In yeast culture. Without Venus's experience in that, no other world could develop such yeasts or maintain them once they did obtain them. So you see that Venus could build a tremendously profitable trade in yeast strains as luxury items with all the galaxy. That would be important not only to Venus, but to Earth as well- to the entire Solar Confederation. We are the most over-populated system in the Galaxy, being the oldest. If we could exchange a pound of yeast for a ton of grain, things would be well for us."

From LUCKY STARR AND THE OCEANS OF VENUS by Paul French (Isaac Asimov)(1954)

This near the center of Ceres' spin, that wasn't from gravity so much as mass in motion. The air smelled beery with old protein yeast and mushrooms. Local food, so whoever had bounced the girl hard enough to break her bed hadn't paid enough for dinner.

He poured a glass of moss whiskey, a native Ceres liquor made from engineered yeast, then took off his shoes and settled onto the foam bed.

An hour later, his blood warm with drink, he heated up a bowl of real rice and fake beans—yeast and fungus could mimic anything if you had enough whiskey first—opened the door of his hole, and ate dinner looking out at the traffic gently curving by.

Miller took another forkful of fungal beans and vat-grown rice and debated whether to accept connection.

Kate Liu returned to the table with a local beer and a glass of whiskey on her tray. Miller was glad for the distraction. The beer was his. Light and rich and just the faintest bit bitter. An ecology based on yeasts and fermentation meant subtle brews.

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

A batch of single-cell protein has been produced by using electricity and carbon dioxide in a joint study by the Lappeenranta University of Technology (LUT) and VTT Technical Research Centre of Finland. Protein produced in this way can be further developed for use as food and animal feed. The method releases food production from restrictions related to the environment. The protein can be produced anywhere renewable energy, such as solar energy, is available.

"In practice, all the raw materials are available from the air. In the future, the technology can be transported to, for instance, deserts and other areas facing famine. One possible alternative is a home reactor, a type of domestic appliance that the consumer can use to produce the needed protein," explains Juha-Pekka Pitkänen, Principal Scientist at VTT.

Along with food, the researchers are developing the protein to be used as animal feed. The protein created with electricity can be used as a fodder replacement, thus releasing land areas for other purposes, such as forestry. It allows food to be produced where it is needed.

"Compared to traditional agriculture, the production method currently under development does not require a location with the conditions for agriculture, such as the right temperature, humidity or a certain soil type. This allows us to use a completely automatised process to produce the animal feed required in a shipping container facility built on the farm. The method requires no pest-control substances. Only the required amount of fertiliser-like nutrients is used in the closed process. This allows us to avoid any environmental impacts, such as runoffs into water systems or the formation of powerful greenhouse gases," says Professor Jero Ahola of LUT.

Tenfold energy efficiency

According to estimates by the researchers, the process of creating food from electricity can be nearly 10 times as energy-efficient as common photosynthesis, which is used for cultivation of soy and other products. For the product to be competitive, the production process must become even more efficient. Currently, the production of one gram of protein takes around two weeks, using laboratory equipment that is about the size of a coffee cup.

The next step the researchers are aiming for is to begin pilot production. At the pilot stage, the material would be produced in quantities sufficient for development and testing of fodder and food products. This would also allow a commercialisation to be done.

"We are currently focusing on developing the technology: reactor concepts, technology, improving efficiency and controlling the process. Control of the process involves adjustment and modelling of renewable energy so as to enable the microbes to grow as well as possible. The idea is to develop the concept into a mass product, with a price that drops as the technology becomes more common. The schedule for commercialisation depends on the economy," Ahola states.

50 per cent protein

"In the long term, protein created with electricity is meant to be used in cooking and products as it is. The mixture is very nutritious, with more than 50 per cent protein and 25 percent carbohydrates. The rest is fats and nucleic acids. The consistency of the final product can be modified by changing the organisms used in the production," Pitkänen explains.


Chose three ingredients to make a nutritious meal and it's unlikely you'd pick carbon dioxide, water and microbes. But researchers in Finland are developing a way to zap that simple recipe with electricity inside a bioreactor to create a powder that's about 50 percent protein and 25 percent carbohydrates.

The edible powder could be mixed into a shake or turned into a tofu-like food for people. It also could be transformed into feed for animals. Because it's processed inside in a bioreactor — similar to how beer and Quorn, a British meat substitute, is made — it doesn't require the tremendous amounts of land, water or other resources necessary for large-scale agriculture and doesn't emit greenhouse gases into the atmosphere.

"We detach the whole process from the land," says Jero Ahola, a professor in the department of electrical engineering at Lappeenranta University of Technology. If solar power is used to produce the electricity, the process is about 10 times more efficient at producing food than conventional agriculture that relies on soil, says Ahola.

For this proof-of-concept endeavor, the bioreactor used was the size of a coffee cup, and the process to produce 1 gram of the protein took about two weeks. Ahola and colleague Juha-Pekka Pitkänen, a principal scientist at VTT Technical Research Centre of Finland, say they are working on plans to build a larger bioreactor, about 6 liters (1.6 gallons) in size, by early next year. After that, they'll apply for additional funding to scale up the system even more, building a 2-cubic-meter (71-cubic-foot) bioreactor that can produce 5 kilograms (11 pounds) of powder per day. Imagine one of those 10-pound bags of flour or sugar, and you get the idea.

"We think that we would be able to scale it up rather soon now that we have got it working," says Pitkänen.

At the moment, the system is running at about 26 percent efficiency, meaning that 26 percent of the electricity is going directly toward turning the mixture into food. The team says they feel confident that they can almost double that to achieve upward of 50-percent efficiency.

The Recipe

To make the powder, Ahola and Pitkänen combine carbon dioxide, water and Knallgas bacteria with ammonium, sulfate and phosphate salts, which act like fertilizers. When the ingredients are inside the bioreactor, the scientists deliver a constant electric current through the mixture. The electricity splits the water molecules, which are made of hydrogen and oxygen atoms. Once freed from its molecular bond to oxygen, the hydrogen can be used by the Knallgas bacteria as energy, which helps the bacteria take in CO2 and turn into protein.

"The first real application could be in the desert, feeding people in Africa," says Pitkänen.

Although electrifying a bacterial concoction to make food seems futuristic, it actually dates back to the 1960s, says Pitkänen, when renowned German microbiologist Hans Günter Schlegel and co-author R.M. Lafferty published a research paper in the journal Nature describing the notion. After that, Soviet and NASA scientists began experiments to see if they could use microbes to create food for astronauts.

"They were investigating how one could turn CO2 and microbes into microbial biomass," says Pitkänen.

But the technology for efficiently generating electricity in space was not well-developed. Space ships are a closed system, where everything must be used or recycled. Carrying heavy fuel onboard to make food didn't make sense, and renewable energy was still in its infancy. For years, the idea of turning microbes into food fell behind.

Today, with renewable energy on an upward trajectory, generating zero-emission electricity and using it to convert a brew of water, CO2 and microbes into a powdery protein makes more sense. With a renewed interest in human space travel, food from electricity could find its way into the cosmos.

In the meantime, it has plenty of applications on Earth. Today, 795 million people worldwide lack enough food to eat. A nutritious, high-protein powder could help address global hunger. It may also help the planet overall reduce greenhouse gases, and Finland specifically, which has set a goal to lower CO2 emissions by 80 percent by the year 2050.

"Our Earth is becoming like a kind of spaceship," says Ahola. "We realize that we are approaching limits and we have to think of similar kinds of solutions for these problems."

Growing Both

"Aquaponics" is a way of raising both plants and meat in one tank. You use an over-sized deep hydroponic tank to grow the plants. Below the plants you raise fish. The fish are fed food pellets. The hydroponic nutrient media is supplemented by the waste the fish excrete. The plants consume the nutrients, purifying the water and keeping the fish healthy ("rhizofiltration"). The system is more stable than a standard hydroponic rig, since the larger tank will buffer and moderate any changes. The larger volume of water also means you can get away with a more dilute solution of nutrients.

Not just standard fish can be cultivated, the system can also be used for shellfish such as lobsters, shrimp, clams and oysters.

In NASA jargon an aquaculture system is called a "sushi maker".

Recycling Wastes

Wastes have to be fed to the algae, or whatever. But it would be nice to turn the astronaut poop into sterile chemicals first instead of infecting the algae tanks with E. coli bacteria. And the problem of reducing to useable form plant stalks, fish bones, chicken feathers, and other tough scraps. Not to mention all the plastic bag bits.

Enter the Supercritical water oxidation (SCWO) unit.

By placing water at temperatures and pressures above the thermodynamic critical point, it turns into a fluid that combines the worst properties of a blast furnance and sulphuric acid. You feed anything into one of these hellfire-in-a-box thingies and nothing is going to come out the other end except water, oxidized chemicals, and mineral ash. This happens at about 374.1°C and 22.12 Mpa.

The only estimates I've managed to find (Parametric Model of a Lunar Base for Mass and Cost Estimates by Peter Eckart) for a SCWO unit are:

  • Mass: 150 kg per person being supported
  • Expendibles required: 10 kg per person per year
  • Volume: 0.5 m3 per person
  • Power required: 0.36 kilowatts per person
  • Heat load: 0.09 thermal kilowatts per person
  • Liquid waste input: 27.18 kg per person per day
  • Solid waste input: 0.15 kg per person per day

Waste products from the astronaut's septic tanks and tablescraps are run through the SCWO. The appropriate output chemicals are fed to the Spirulina, which multiplies in meters of transparent tubes run under filtered sunlight. Filtered because raw sunlight in outer space is quite deadly to algae, and it isn't too healthy for humans either.

Water is pretty near the universal solvent at room temperature. Heat it to quite high temperatures, under fairly high pressure so that it doesn't boil, and it gets, uh, more so. Dissolve a bit of oxygen in it, and you have a fantastically corrosive witches' brew that will vigorously attack almost anything. Throw in just about any organic substance you care to name, and out comes water, CO2, nitrogen, and sterile ash (oxides of metals, mostly). One of the bigger practical problems, in fact, is making the equipment stand up to it. The other major problem is that it's pretty power-intensive, because of the high temperature and high pressure.

It's pretty much the preferred way to recycle organic wastes — kitchen garbage, human wastes, etc. — in designs for advanced closed-cycle life-support systems.

Henry Spencer

There is more information on SWO units here. The first reference describes a facility with a volume of just over 20 cubic metres that can process 7.5L per minute, more than enough for a crew of 300. (30L/person/day - 20 hours a day). Thanks to William Seney for these link.

General Atomics has some developed some SWO units for waste disposal.

Amino Acids


 Plants are not a particularly efficient source of protein. They tend to be better at producing carbohydrates. As a result, vegetarian diets often focus on a few high-nitrogen plants like beans, soy and peanuts.

 I tend to explore food systems that are familiar, but let's take a minimalist approach and see where it leads. Instead of deriving protein from plant sources directly, what if we use microorganisms to produce amino acids in bioreactors using plant starch as input? This is like that sci-fi staple 'vat meat', but with neither texture nor flavor. Still, amino acids can be stored for years (possibly decades) if powdered and sealed.

As with all my posts, this article is based largely on internet research. I am not a process biologist. I've included sources where possible, but these results should be considered preliminary at best.

Short results: vat-grown amino acids can be yours for 4-6m³ per person.
That includes vats, supporting equipment, hydroponic space and waste treatment.
You will still need to provide bulk calories and other nutrients.

 Let's start with demand. The indispensable amino acids  are tryptophan, threonine, isoleucine, leucine, lysine, methionine, phenylalanine, valine and histidine. Required amounts vary; women typically need the least at about 14g, men in the middle with about 18g and children requiring the most at about 22g. Contrast with protein requirements of 110g, 140g and 90g respectively. These figures are from my menu tracker which is based on US dietary recommendations, so do not take this as specific dietary advice.

 Dietary protein serves two purposes: first as a source of food energy and second as a source of amino acids. If we eat only amino acids then the 'missing' food energy needs to be provided by additional carbohydrates and fats. That also means we only need to eat enough amino acids to satisfy the body's need for building material. The science is not settled, so let's assume we need twice the minimum amount or an average of 36 grams per person per day. Some of this will be provided by other food items but let's ignore any other protein sources for now.

 Production is varied as there are several distinct chemical structures involved in the various amino acids. Each type or family requires a specific environment, feedstocks and process. A basic overview is available on Wikipedia, while a deeper look at processes for the aromatic amino acids is available here. This is just an example; the industry has been active for decades and there is a lot of material available on this technology.
 Plant starches can be readily decomposed into glucose using microbes or enzymes. (see for example the process of making sake; rice is decomposed by a fungus to produce sugar-rich material for yeast to ferment into alcohol.) Sweet potato mash with autolyzed yeast and/or spirulina should be a reasonable starting point for producing a viable nutrient solution.
 The chosen microorganism is grown in a starter culture (1-5l) for half a day and then transferred to a large vat (100-500l) for fermentation over an additional one to three days. For industrial and medical purposes the finished broth is lysed by freezing, vibration or centrifugation and then separated by centrifugation. Further purification steps are applied including filtration and fractional crystallization. For nutritional use this high-grade purification may not be necessary. An example might be alanine as a byproduct of valine production; for an industrial process this would be a contaminant but as a food source it's beneficial. In this case a single-step centrifugation/separation can be applied with the result tested for composition and then dried without further processing.

Yields listed below are lab results, specified in units of product per unit of glucose. Nonessential amino acids are in italics. Many of these values leave significant room for improvement.
There is also a note in the book "Corynebacterium glutamicum: Biology and Biotechnology"  (edited by Nami Tatsumi, Masayuki Inui) on page 111 giving a snapshot look at yields of industrial C. Glutamicum fermentation processes. These values are weight percent, given in {} brackets below; as you can see, most products scale up well but a few do not.

Glutamate - {50%}
Glutamine -  {40%}
Proline - 36% g/g
Arginine - 35% g/g

Aromatic amino acids
Phenylalanine - 25% g/g {50%}
Tyrosine - 30% g/g
Tryptophan - 14% mol/mol {22%}

Lysine - 42% mol/mol {50%}
Asparagine - unknown
Methionine - 20% {17%}
Threonine - 60% {45%}
Isoleucine - 22% {25%}

Ribose 5-phosphate
Histidine - 5.5%

Serine - 45% g/g {32%}
Glycine - unknown
Cysteine - unknown

Alanine - 86% g/g {50%}
Valine - 88% mol/mol {35%}
Leucine - 30% mol/mol

A ballpark value for the overall average yield is perhaps 40% by weight, requiring 90 grams of glucose per person per day.

 Final concentrations average around 20g per liter, with some exceptions (histidine in particular is perhaps 5g/l while some others are over 45g/l). That works out to 8g/l/day or 4.5l per person. Let's double that volume again (for redundancy) and call it about ten liters of bioreactor volume per person. Space is required for starter cultures, nutrient processing and storage; let's assume this supporting volume (and wasted space due to packing issues) is twice that of the vats and call it 30 liters of volume per person. At a thousand liters per cubic meter, 1m³ could serve a bit over 30 people.

Let's go over the drawbacks:

 - The bioreactors have to be controlled (pH, temperature, glucose, nitrogen, oxygen, agitation), which requires energy. Information on power requirements are difficult to find, so I can't offer even a bad guess. This also means some smart tech is required for automation.
 - Product yield is less than 1% of the final broth, so assume that the entire volume has to be treated as wastewater. About 5 liters per person per day.
 - As a biological process, cleanliness is essential. Quantities of soap, alcohol or bleach and washwater will be required.
 - Population control is important. Bacteria evolve rapidly and cross-contamination is a possibility. Vats must be monitored for invasive species and unexpected byproducts. Reserve supplies
 - At least nine separate product lines are required. More may be needed to completely replace food protein needs.
 - The nutrient solution has to provide everything needed for the microbes to grow and thrive. This is on par with intensive hydroponics for complexity.
 - Centrifuges are tricky in microgravity. Angular motion needs to be carefully balanced, so vats should always be counter-spun in mass-matched pairs.
 - The system requires carbohydrates as inputs. These in turn require production of enzymes to break the starch into glucose.
 - Amino acid powders are not particularly appetizing.

These are largely the same drawbacks that apply for alcohol production and can easily be integrated into that workflow. Nutrient supply can be integrated with the hydroponics workflow. Wastewater can be handled largely by evaporation or ultrafiltration (though centrifugation should yield concentrated sludge and fairly clean water as separate outputs), with concentrated wastes blasted in the SCWO reactor and recovered by spirulina. Carbohydrate supply can be provided by either sweet potato (24.0g/m²/day) or wheat (18.5g/m³/day), requiring 3.8 to 4.9 m³ per person. These inputs would co-produce edible protein extracts amounting to 8.6g or 16.5g respectively. Not much can be done for the taste other than combining with protein extracts or other food ingredients, unfortunately; perhaps that will change with applied research.

Here are the advantages:

 - No animals.
 - Simple waste streams.
 - Extremely compact.
 - The tools and techniques can be applied to other biosynthesis products such as ethanol and other industrial feedstocks as well as a broad variety of medicinal compounds.
 - The techniques for producing the necessary inputs are largely the same as for intensive hydroponics.
 - A variety of techniques are available for continual improvement, including selective breeding, directed mutation and outright genetic engineering. Microbial gene editing (such as with CRISPR) allows earth-based developments to be applied to in-space organisms by sending only data.
 - The process can be scaled easily for populations from one to a thousand or more.
 - All of the technology can be built, tested and optimized on Earth. A round of low-gravity performance testing and some engineering sweetness to handle periods of microgravity would be a good idea before deployment but not strictly necessary for use on a spinning habitat.

I still believe it would be beneficial to use all plant wastes as feed for insects, fish and possibly chickens. This represents recapture of energy that would otherwise have gone to waste into food products for variety. Even so, a vat process could be paired with suitable hydroponics for complete nutrition with high efficiency. Sweet potato greens are edible, so a menu could be devised that minimizes plant waste. A steady diet of sweet potatoes, salad and amino acid seasoning doesn't sound very appealing to me but it might be among the earliest self-sufficient space food systems.

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