Do a Google search for:

"cooling suit" ice
or
"cooling suit" vapor compression

Here's some stuff I came up with during a search for a low-tech basis for cooling suits for Mechwarrior.

These suits use ice as the coolant:

http://www.nttc.edu/ertProgram/corecool.asp
http://apps.em.doe.gov/OST/pubs/itsrs/itsr1898.pdf

While this one uses an actual vapor-compression system like your car's or home's air conditioning:

http://www.natick.army.mil/about/pao/2001/01-40.htm

The bottleneck is not the suit (which can be very light), or even an actual refrigeration unit (which is obviously conquerable in light of my third link), but the batteries. Those were reduced pretty well in the 1990s, and any society (like SR) that can create batteries adequate for man-portable laser weapons will have no problem designing a chill suit.

Now, the whole water-capture thing is a bit more difficult, but simple enough once you have refrigeration, a face mask (for exhaled water vapor), and "plumbing" connections (probably easier to hook up for men than women). Refrigeration allows for easy condensation and collection of exhaled water vapor. Recycling urine is old hat for life support systems. Reverse osmosis, charcoal filters, etc. will get the impurities out pretty well, and can probably be made flexible enough to fit into thigh or torso pouches.

If you want to recycle water out of solid wastes...it's probably just be easier to "hold it in" longer and let the large intestine soak out moisture (which is part of the large intestine's duty anyway) than to try some fancy, compact turd dryer built into the suit. The plumbing connections alone would be a difficult (and gross) engineering challenge.

As for sweat off the skin, you shouldn't be leaking much from there with a good chill suit keeping you cool. If not, I suspect it's easier just to sweat it out through breathable fabric than trying to collect it.

Something for the average soldier? I'd remove a few features.

FANCY MILITARY MODEL:

Make an insulated garment like a wetsuit, but the fabric is breathable and the underlayer is laced with coolant tubes and thermal storage gel packs (as reserve coolant). Colors can be anything, maybe even color-shifting camo. You don't need high reflectivity to keep the heat down, just add a bigger refrigerator unit. In some convenient location (shoulders or waist), add the refrigeration unit(s). Give'em about 500 to 1000 watts of cooling capacity (more for orcs and trolls) - this is the future, you can make them that size, considering they're in the 300-watt range now. There refrigerator will have 2 batteries, each 1kg, that easily snap in and out of the refrigerator. The suit will be c3kg. The refrigerator will be 2kg, perhaps split into two units to distribute the weight. The batteries will be 2kg. May have gloves and face mask to minimize burns and maximize cooling. Good for, say, 12 hours per battery. The outer layer may function as a solar cell, extending operating time quite a bit. The suit IS insulated, which both slows the rate the sun heats a soldier and keeps a soldier warm over night.

Batteries are recharged in an hour at a charging station on a handy APC or other vehicle, hence two batteries: one can be swapped out at a time.

Primary differences from the even fancier civilian model: no "plumbing connections" and not reflective. No effort to recycle water, except maybe a face mask. IMO, the fanciest part of the suit is the whole water capture thing. By reducing sweating of the soldiers, water usage in the desert should be way down.

SIMPLE MILITARY MODEL

This is just a set of lightweight, full body under clothing, like:

http://www.ninfinger.org/~sven/models/suit...its/suit67.html

All it does is provide cooling and stays under normal clothing (and armor). The refrigeration unit is put on any web gear or other external mount. 1kg suit, 4kg of refrigeration and batteries.

REALLY SIMPLE MILITARY MODEL

Like the Simple Military Model, but the refrigeration unit is replaced with a 5kg thermos of 3kg of ice (for humans - double for trolls). A low-power electric pump circulates the coolant. Good for about 3 hours. Swap out the thermos for a fresh one from a special freezer kept a nearby vehicle.

I wasn't recommending a full body suit because it was needed, I was recommending that because it kept the wearer comfortable, like on a 20-degree day. I figure if you're passing around personal air conditioning systems, there's no reason to do things by halves.

I was also specifically avoiding peltier coolers because of their terrible efficiency at moving heat. You can probably save weight in the overall system if you use another refrigeration technique and reduce the battery size. Peltier coolers win points for mechanical reliability, but a scroll or double-lobed compressor has about three moving parts, as I understand the systems. That's only about two more moving parts than the peltier version (which still has the water pump).

well i dunno about compressors, but I do know peltiers, and as far as im concerned they would do the job.

Come to think of it ive heard that compressors dont like being shaken and jostled, thats why you should let a fridge sit after you move it so it dosent explode.

Yes, peltiers would do the job, and honestly, there's something attractive about their simplicity. I suspect their efficiency could be improved over the decades.

As for exploding, consider cars - including those rugged off-road sorts - and planes (fighter aircraft, too) do use compressors in their AC systems despite heavy vibration and shaking.

fair enough, The person who told me that was known for his Bumchat and Asshattery.

a friend of mine made a USB drink cooler out of a aluminium block, a peltier, an old cpu cooler and a usb cable...

Precisely why I posted this.

Since we're all flapping about:

What I'm looking for is intended, initially, for SOF (Special Operations Forces), and the average infantryman.

Now, FYI, the average infantryman easily carries 100 lbs of gear. This being the ME, he has to do it in some very hot weather. (For some strange reason, wars in the region around Israel *always* happen in the summer, despite that being the WORST POSSIBLE TIME to be in combat!) It's a *bad thing* to add appreciably to the soldier's load, IMHO.

Also, one of the massive problems of military logistics these days is not moving bullets and such; Nope...it's moving WATER and fuel. That's why the US Army really wants to use hydrogen fuel cells in its Future Combat System (to be deployed maybe 2010-2015); You eliminate both of those requirements. Now, maybe I can't really pull the fuel requirement, but....the idea of water recycling like the stillsuit presented in Dune appeals to me because of that logistics issue.

Not worth the trouble or cost if you're equipping 10000 infantry, if you ask me. Just by including cooling systems in infantry clothing, you'll cut water needs significantly. Trying to include water recycling systems in thin-shelled suits with no room or mass for that kind of complexity (let alone asking 10000 infantry to get their "plumbing" connections right) is just too much bother.

If you want water from vehicles, put an exhaust trap on hydrocarbon-burning vehicles. The products of burned hydrocarbons (methane, gasoline, diesel, kerosene, etc.) are notionally carbon dioxide and water. In less than ideal circumstances, you also get nitrous oxides, carbon monoxides, etc. But you still get water when those fuels are burned. Run the exhaust through a chilled trap to capture the water, filter the water, and you have plenty of drinking water.

In fact, you should get about as much water (by weight) out of a combustion engine as the mass of fuel you burn. If your tank burns 500 gallons of diesel, you should get 400 gallons of water (or more) out of the deal.

Is that 4 liters per day in a desert environment, or 4 liters per day in a temperate/air conditioned environment?

And I take it that...

1) the SOF in question does not have a vehicle(s)
2) the SOF in question does not have a mage

...correct? Just mundane PBI?

Anyway, I did some research on real life water usage and took another look at water recovery/loss prevention.

"Still suit" is a misleading term for what I'm proposing. Two major sources of water loss (feces and sweat) are much better dealt with through prevention, rather than waiting for defecation and sweating to happen and then try to distill water from them. Rather, a change in diet and a "Chillsuit" would be much more effective (or easier to engineer) than a "stillsuit."

And the important thing is reducing water usage of SOF/regular troopers in the desert, right, not actually holding to the aesthetic of a stillsuit?

WATER LOSS FROM AN ADULT HUMAN
Sedentary adult human: 2.5L/day
Average adult human: 3.8L/day
US Marines survival minimum, desert: 9L/day
US Marines recommended minimum, desert: 20L/day

LOSS MECHANISMS
Urine: ~1.5L/day
Feces: ~1.5L/day
Sweat, non-exercise: ~0.8L/day
Sweat, non-exercise, 100F/38C: 1L/hour
Sweat, exercise, 100F/38C: 1.5L/hour+ (4L/hour has been reported)
Breathing: .25-.5L/day

CAPTURE & FILTER MECHANISMS:


Exhaled Water is a trivial engineering challenge. A face mask with one way intake/exhaust valves can send exhaled air through refrigeration pack, where water can be condensed out and run through charcoal filters.

Urine is relatively easy, particularly for males: a capture tube (condom variant) sends urine to reverse osmotic filters to separate water from the salts. A pass through a charcoal filter should finish the job. There might be some other treatment needed, but it should be straightforward. For your SOF types, the "ick, eww, I'm drinking piss" factor should be readily conquerable. Convincing regular troops of the same is another matter. With several years development (c2000AD), the filters should be readily made flexible and flat, fit for putting in thigh or calf pouches.

Fecal water content. Well, you need to stop thinking of the stillsuit doing everything and focus on the goal: reducing water loss, which can also be achieved by prevention. I think you'll like the third concept of fecal water recovery.

*First, to recover the fecal water content...you can give up on fecal water content as a lost hope. Even SOF troopers may have unconquerable concerns about drinking distilled fecal water, although there's 1.5L lost to it daily.

*Second, to recover the fecal water content, you can have some exterior, heated (solar?) dehydration still that captures evaporating water. This should be a quite lightweight mechanism, like cookware. (An aluminum bedpan shared by the whole squad?) It just won't fit easily into the stillsuit. The person who carries, loads, and operates the still will redefine "shit duty." (Don't throw away that used toilet paper! It's got water on it! Put it in the distiller!)

*Third, to recover the fecal water content, you can stop defecating. No, seriously. Put the soldiers on a "low residue diet," making more of the soldiers' diets liquid or readily soluble, so most of the waste is in the urine and the soldiers can go for days, or over a week, without defecating. It seems to work for astronauts (the ones who don't want to risk zero-G toilets) and people facing certain proctological exams. The above urine trap can reclaim the extra water.

Sweat: the big water loss mechanism in the desert. Again, you might not want to think in terms of capturing sweat with the stillsuit, but rather preventing the loss to begin with.

*First, to recover sweat, you can stop/minimize sweating. Seriously. Remember, people sweat in the desert because they're hot. That's not a problem with a refrigerated stillsuit, is it? If you have a powerful cooling system (as would be possible for Shadowrun in the 2060s) that give keep skin temperatures at 60F/16C and below, you can exercise the soldiers like a horse with minimal sweating. Cooling the soldiers is a relatively easy and practical way of slashing water consumption by a many liters per day.

*Second, to recover sweat, speculating on what's possible with 2060's materials technology, you can use the very cooling tubes lacing the suit. Make the tubes osmotic tubes that suck in water on their surfaces. The circulating water will carry the half-purified water to the refrigeration pack, where excess water can be squeezed out by reverse osmosis (figure the coolant actually has some anti-freeze or other chemicals). The suit will get pretty funky with crusted salt, so it better be washable.

*Third, to recover sweat...don't bother with anything other than cooling the soldier. Make the stillsuit lightweight, breathable, etc. If you can cut water losses through sweating in half by cooling the soldier, you've already saved more water than recycling piss and exhaled water will net you.

If you want some other 2060s tips for describing the stillsuit:

1) There are no pumps. Contractile polymers (myomers in BT) wrap the tubing in the suit and create a peristaltic pumping action. If enough of the tubing is made this way, it will be impossible for localized damage to cease coolant (and water) circulation. If the tubes can contract enough, they can isolate any holes by pinching off a broken line.
2) The outer shell (if not meant to be covered by body armor) of the still suit is a solar panel.
3) Power is (also) from a fuel cell (direct methanol fuel cell for safety). Say a liter nets 48 hours of cooling power. Heck, that's more a near future solution than Shadowrun's batteries for man-portable laser weapons.
4) The cooling system has no moving parts. It uses a high-efficiency peltier or sorbtion cooler.

Penta, I'm curious:

Do you want stillsuits, or do you want to minimize the amount of water troops in the desert need to carry with them?

The goals are not necessarily the same, especially now that you've limited the discussion to real life technology.

The way human bodies shed water and with the current state of the art, the saying, "an ounce of prevention is worth a pound of cure," is highly applicable.

Closer threading...just use plastic sheets rather than woven fabrics.

Anyway...

Reduction in water usage. From my research (available further up in the thread), the primary means of losing water in a desert is sweat.

To prevent that: keep the person cool. This is not only possible with real life technology, but available in forms of equipment easily usable by common soldiers. It also gives a whole new meaning (to me) to all that talk in the military about "microclimate suits" - the researchers are talking about taking soldiers out of the desert without taking the soldiers out of the desert. They put them in air conditioned clothing. This avoids (most of) the 1-liter per HOUR water loss to sweating and gets you down to the 4L/day of most people.

Next two big loss areas:

*Urination - 1.5L/day
*Defecation - 1.5L/day

Defecation is another area where water loss can be prevented, and it doesn't even need equipment changes, just diet changes. "Low residue diets."

Now you're down to 2.5L/day usage. Well, probably 4L/day, those low residue diets are usually water-based (soups, etc.) But you've changed the water loss of defecation into something easily recovered: urine.

Urine is the only recycling part of a desert suit that's really needs distillation, and it's easy to distill. Reverse osmosis, charcoal, this and that, and you've recovered the water in your urine. Very easily usable by the average soldier, not to mention SOF troopers, and even quite possible with real technology.

In the end, you'll be spending about 1L/day on respiration, which should be recoverable with a mask that sends exhalations through the desert suits' refrigeration pack.

I'd gratuitously add 1-2L/day sweating losses. Hard working bodies leak sweat even if they don't get wet.

Suggested stats:

1) Diet change is handled by rations. You'll need extra water to begin with, like 4L to kick start the low residue diet. Then you can tap water from the desert suit to rehydrate low residue rations.

2) The Full Desert Suit itself is...7kg for a human, elf or dwarf. It's all in the battery pack. That's 7kg without water. Two batteries are present and good for 24 hours each (of cooling OR heating), but actually each last about 48 hours because the skin of the suit is a solar cell. The suit keeps the wearer cool and recycles urine, storing up to 10L of water in assorted, distributed bladders that serve as temperature moderating thermal masses during battery changes. Each liter adds a kilogram to the suit. The water may be tapped from a tube to rehydrate rations. The suit is simple enough for any wearer to use, but precludes other clothing or armor. Usually used by SOF troopers who don't want to be burdened with heavy armor but want protection from the desert. Provides 5/3 armor for the whole body, including head, hands, and feet. Cost is 2000 nuyen, or 12000 nuyen with active camoflague.

3) The Minimal Desert Suit is an undergarment for heavy military armor or uniforms, fit for dumb grunt infantry. It is 6kg (batteries), but any water must be stored in external canteens. Like the Full Desert Suit, it provides cooling and urine recycling. Provides no armor, costs 1500 nuyen.

I like the point about form fitting armor. That's definitely worth noting.

Damage rules. I like that. Well, the suit has three critical systems:

1) Cooling tubes
2) Batteries & Refrigerator
3) Urine filtration packs & water storage

Damage to the cooling tubes won't matter much, especially with 2060s-era self-sealing tubes, so there's large areas of the suit that won't mind being damaged. And a deadly wound to the wearer (bullet to the heart, for example) won't necessarily hit any critical systems.

So maybe...

*Roll 1d6 when the wearer is injured...
*Light wound: no effect to suit.
*Medium wound - roll of 7 suit is damaged, armor B/R test TN 5 to repair
*Serious wound- roll of 6+ suit is damaged, armor B/R test TN 7 to repair
*Deadly wound - roll of 5+ suit is damaged.
*If the wound is inflicted by an explosion or a burst of more than 3 bullets, add 2 to the roll. If the wound is inflicted by naval-scale damage, add 3 to the roll.
*If the roll exceeds the target by 2, the suit is irreparably destroyed.

Damage effects: Roll 2d6 and multiply by 10% (maximum 100%). This is the amount of stored water lost (does not apply to minimal suit). Further, the suit no longer works - it is a hot, insulated garment until repaired. Repair attempts generally take 1 hour divided by extra successes.

That damage information can be put together into a compact paragraph or two in an equipment write-up, along with equipment blurbs.

Good, good. I'd add "greater than both WORN impact and ballistic armor combined," because the minimal suit worn under military grade armor would be pretty well protected.

And damage means "the suit stops working until fixed."

I'd also note (for roleplaying effect) that, "this damage represents serious damage that stops the suit from functioning. The suit is quite rugged. Lesser damage, including quite a few small punctures and tears, do not interfere with the suits function."

Okay, so, in summary:

DESERT WATER CONSERVATION EQUIPMENT:

1) Diet change is handled by rations. You'll need extra water to begin with, like 4L to kick start the low residue diet. Then you can tap water from the desert suit to rehydrate low residue rations.

2) The Full Desert Suit itself is 7kg for a human, orc, elf or dwarf, or 12kg for a troll. It's all in the battery pack. That's 7kg or 12kg without water. Two batteries are present and good for 24 hours each (of cooling OR heating), but actually each last about 48 hours because the skin of the suit is a solar cell. The suit keeps the wearer cool and recycles urine, storing up to 10L of water in assorted, distributed bladders that serve as temperature moderating thermal masses during battery changes. Each liter adds a kilogram to the suit. The water may be tapped from a tube to rehydrate rations; this usage is factored into recycling values. The suit is simple enough for any wearer to use, but precludes other clothing or armor. It is usually used by SOF troopers who don't want to be burdened with heavy armor but want protection from the desert. The suit is rugged - a lot of minor punctures, tears, and dents are ignored. Only significant damage causes it to stop working. Provides 5/3 armor for the whole body, including head, hands, and feet. Cost is 2000 nuyen, or 12000 nuyen with active camoflague.

3) The Minimal Desert Suit is an undergarment for heavy military armor or uniforms, fit for dumb grunt infantry. It is 6kg or 10kg (batteries), but any water must be stored in external canteens. Like the Full Desert Suit, it provides cooling and urine recycling. Its batteries last 24 hours each. Provides no armor, costs 1500 nuyen.

RULES
The low residue diet does not alter the amount of water a person uses, but changes how the body gets rid of it (mostly through urination, vs. urination and defecation) and simplifies the life of recycling equipment.

Both desert suits basically eliminate water loss due to sweating while they have power, leaving a person's water usage at 4L per day. The suits reduce this to 2.5L per day by recycling urine. If the person is on a low residue diet, water use per day is 1L. The distilled water produced by the suit (chilled, even) is assumed to be drunk and used in rehydrating food, and thus need not be tracked.

The suits can be damaged. If the power of an attack is greater than both the suit's and worn armor's impact and ballistic values combined, the suit may have suffered damage. The number by which the power exceeds the armor must be rolled on 1d6 to avoid damage to the suit. If damage is not avoided, the suit stops functioning until repaired. TN 6 on Armor B/R to repair. If a non-functioning suit is worn in temperatures over 25C, the wearer suffers 1 box of stun damage per 10 minutes from heat exhaustion

The full desert suit gives armor; the minimal suit does not.

The full suit is meant to be worn by itself, without extra armor, by soldiers. Ergo, it has armor.

The minimal suit is meant for grunt soldiers who will have additional armor as part of their standard gear, and thus does not have armor.

Nothing bad about your question. It was certainly worth clarifying why the gear did (or did not) have armor built in.