A recent thread on eating one’s own feces in a survival situation got me thinking: Are Dune-style stillsuits possible with today’s technology, and if they are, how expensive / difficult would it be to construct one? For those who aren’t familiar with Dune, a stillsuit is a suit covering almost all of the body, that collects all liquids excreted (sweat, urine, feces, moisture from exhalation), filters them, and delivers them back to the user in the form of potable water.
I’m interested to hear people’s takes on this one. For me, the tough part to accept was that it did all that using only the energy of the person’s movements. I’d imagine that with a sufficient power supply, you could recycle enough to delay, but not totally prevent, dehydration. But I don’t buy the perpetual motion aspect of it.
Stillsuits are not possible today, and I doubt that they would ever work. Have you seen the size of a sewage treatment plant? And those things don’t produce potable water, they only clean it enough to release back into nature, AFAIK. If there was a simple technology that would make it possible for a stillsuit, it would be used in municipal plants first.
Plus, would you really want to spend any amount of time in a form fitting bodysuit that you defecate in? I know that I wouldn’t.
It’s not perpetual motion… you have to eat. This is an energy input.
And the fremen do drink water… they just pretend they don’t need to.
With modern materials and processes, you could make one that recycled most of the urine, and some of the sweat, and maybe a little condensation from the breath and feces, but the suit would be nowhere near as efficient as the one Herbert depicts, nor would I make any guarantees about the palatability of the water, and you’d have to spend a lot of effort cleaning it out regularly…
Ick.
Oh, and it would also be prohibitively expensive, and require external power sources to operate.
Nothing’s impossible, but not everything is practical.
Science. Fiction.
The real problem with stillsuits is fouling up shedding heat. How on Arrakis are you supposed to cool off if you’re not evaporating water??? If the freemen have a low tech way of cooling off without losing water, recycling it would be a breeze.
Strictly speaking, deserts don’t have to be hot. There’s nothing to keep the average ambient temperature of Arakis from being a chilly 3 degrees C, which would solve the whole heat problem.
Herbert never delved into the actual details of the stillsuits. Perhaps the recycling utilized some sort of engineered bacteria that would munch on the organic molecules in the urine and feces and excrete something drinkable, or leave something drinkable. Which would also solve the energy problem. Sort of.
A tertiary treatment plant will produce water that is clean enough to drink. The whole aim of most tertiary plants is to reduce the faecal coliform load of the effluent to below that of the water source into which it is discharging.
Here is no place for stillsuit technology is sewage treatment. A treatment plan is designed to remove bacteria and requires vast amount of water to do so. A stillsuit is designed to remove water, and whether the effluent is sterile or not is irrelevant. They do completely different jobs.
If it were a choice between that and death then I know that I would.
According to the Dune Encyclopedia, which I no longer own, the heat is shed as normal. The sweat soaks into an inner layer of cloth and evaporates just as it would if you were wearing normal clothes. The water vapour is then caught by a chemical in the next layer a few millimetres away. If anything the design would increase cooling because humidity next to the skin would always be close to 0.
It seems distantly possible until the “feces processed in the thighpads part…” I could conceivably imagine a membrane filter for sweat, or urine, but I can’t even imagine a mechanism for handling solid waste.
Reading Dune, I often chuckled to think of proud Fremen warriors crapping in their pants whenever the mood struck. I guess I’d rather spend my time in a form-fitting sewage-eating suit than a droopy, sagging one.
They wouldn’t be “crapping in their pants whenever the mood struck.” I can’t remember which book it was, but at one point a character explains that one should never leave water in the stillsuit catchpockets, but drink it immediately, because “the best place to conserve water is in your body.” For this reason, and the fact that solid waste excretion carries a water cost, I imagine that Fremen children would be taught to “hold it in” as long as practical to conserve water - the thighpads are a contingency option, but not the preferred one. Just my take, of course - your milleage may vary.
What would you do about the bacterial growth and resulting BO that would build up inside that kind of suit after like, 12 hours? Most people feel icky if they don’t shower every day while wearing breathable cloths.
I think that what grew on the outside the body would be just as big a hassle as filtering what came from the *inside * of the body.
Mmmm.
Sietch Tabr. Smells like home to me.
This would merely transfer heat from the skin to the suit. It’s the water vapor that carries the heat away, so if you recapture the water vapor then you are recapturing the heat as well. I think a stillsuit, if used in a hot desert, would need a powerful active cooling system to make up for this.
So the general consensus would be to use only at night and to have a Mad Max poop hole?
If heat retention was not a problem, solid waste was not recycled and you were only filtering what needed to be filtered to make the liquid not harmful, could all that be done using motion, a small battery and filters?
Also, could it every be used in a hot environment? If we go with the idea that Blake mentions and have the heat transferred from the skin to a layer within the suit, is there any way of ensuring that that heat was then passively shed outwards rather than either just sitting there and cooking us or being shed back in to the body? What we need is a heat Gore-Tex 
.
Unfortunately a “heat Gore-Tex” (i.e. a material/device that passes heat only one way) would violate the laws of thermodynamics. So that’s out.
If the air temperature is at least a few degrees below body temperature, you can use forced convection for cooling. That means using a fan. Your suit would need to be impermeable to water yet have high thermal conductivity; fortunately this is easy, a simple aluminum foil does the job. You’d also want to minimize radiative heating (absorption of visible and infrared light), but a simple parasol may suffice. In addition you need a fan to maximize convection (that’s the “forced” part in forced convection.)
If the air temperature is higher but the exposure duration is limited (e.g. it gets cool/cold at night), you could use a material that can absorb heat throughout the day and “refreshed” overnight. Similar to what we use in coolers.
But I think it’d be easier to use an active cooling system and try to think of ways to obtain energy somewhere. In addition to temperature control, you’d need a heat exchanger to reclaim water which has evaporated from your body. If it’s a hot desert you can probably use solar cells.
yBeafy, you the man (or woman)! I’ve been wanting to ask this question for the longest.
I know this won’t stick to the Fremen stillsuit specs, but perhaps we can simplify the design to better accomodate what existing technology can deliver. Forget processing the feces. Forget processing most or all all of the sweat. Perhaps a feasible suit could be built collecting moisture from aspiration and from urine?
IIRC, the amount of moisture lost during aspiration dwarfs the amount of moisture lost from sweat, urine, and feces anyway.
Boy, I sure know how to kill a thread.
Why not use the recycled water to help cool the suit? I see microtubes running throughout the suit. Movement (especially in the knees and elbows) help pump and circulate the water. Chemical reactions in the storage areas cool the water. Before leaving, the user “primes” the suit with water. The amount expired is captured and added to the suit’s reserves. Eventually, the suit would run out of water but a user could probably last for a few weeks at least.