# Solar Heated Spacesuits



## AlexanderSen (Jan 6, 2014)

I had an idea for one of my books, maybe someone could help me with it? 

The idea was Spacesuits which have a special two-way material which  could function as both insulation, on one side, and a heat absorber on  the other. Sort of like a living plant, the suit could collect all the  energy of the Solar radiation and use it for heating, cooling, and  energy of the suit, while the suit material on the other side would only  allow heat energy to travel in one direction, thus keeping the user  insulated.

Are there any other stories with such a thing? And what are technical  problems of such a suit? As I don't know much about engineering such a  suit.


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## chrispenycate (Jan 6, 2014)

Firstly, in space (in vacuum, more precisely) the difficulty is more in cooling than in keeping warm (all the freezing of blood and the like is due to adiabatic expansion of gasses from within the suit when there's a leak, or the evaporation of body fluids and the latent heat of vaporisation. There is no conduction or convection in a vacuum (see also thermos flask) so you're restricted to radiation to dispose of energy.

As, you may say, is the Earth itself, hitting a balance between energy absorbed on the sunward side, and re-emitted on the night side into the 3°K of cosmic background, with a minor correction for greenhouse effect and starlight, geothermal and reflected energy. Stable is around freezing. But Earth does not have such a high percentage of its interior taken by exothermic living organism. A passive human being produces a hundred watts of energy, one doing hard physical work can manage more than a kilowatt. All that energy ends up as heat, which needs disposing of, and only radiation to dispose of it by. Cooking is much easier than freezing.

I would accept solar panels as energy sources, but don't heat sink them into the suit; you're more likely to want to cool that down.

If you use compressed gas jets for mobility in space, you've got some useful cooling when it expands; or, if you use my suits (), which are tight compression mesh which you can sweat through to use the body's natural thermostasis and water cooling rather than relying on heat radiators, we might be able to use entirely solar energy, but don't forget solar cells, like any heat engine rely on difference in temperature to function.


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## AlexanderSen (Jan 8, 2014)

I was planning to use it for a novella I am writing about colonizing a new planet. It is based upon some of my experience landscaping and working with the land. There is some heavy machinery in it, so there is some more rugged work with the suits involved.

I was looking for a more rugged suit, which had more utility as living and working on another planet means a lot more stability/ruggedness is needed if they are to survive more than a short stay.


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## chrispenycate (Jan 11, 2014)

So, not really a spacesuit at all. Designed to work in planetary gravity, with an atmosphere surrounding it, even if the atmosphere is not optimum pressure and unbreathable or even corrosive. Their standard vacuum suits could be used as a temporary expedient, but carry a lot of gadgets that are unnecessary or ill adapted to the different conditions, notably propulsion.

If they in advance knew they would be exploring another planet, they'd take planetary isolation suits with them, sealed against external environments but otherwise very much like tough outside overalls with gloves and an airtight hood. Air can be carried, power recycled or filtered from the exterior atmosphere (anything that can detect molecular differences to get the gas mix right will have no problem eliminating viruses or potential allergens), but I doubt whether solar energy would be sufficient to do the carbon dioxide breakdown. There again it might be; plants are not over efficient.

You'd keep a slight positive pressure inflating the suit, so in the case of a puncture, interior gas would leak out, rather than unknown external compounds seeping in (with an alarm; it could always diffuse in). The most difficult is actually the gloves; difficult retaining strength and sensitivity without being perforable. 

The exact requirements for the suit will depend on local conditions; a cold,  thin-atmosphered desert planet would be essentially simple, just a question of insulation, not much different from terrestrial polar gear, while a thick, hot layer of methane, water vapour and carbon dioxide, though more promising for future terraforming, would demand refrigeration, and that pushes you towards the limit of what you what you can get from solar power. Odd that  you should need more energy to get rid of heat than to generate it, and we've got to work out breathable air yet, too. 

One trouble with solar power planetside is that you have to stock it. There are periods of darkness, obstacles to the energy. So you need some pretty hefty batteries of some sort – quite likely electrochemical, but perhaps magnetic or capacitive – incorporated into the weave. I can see several means of cooling – if you have an adequate supply of water you could even use your body's thermostasis sweat evaporation, pumped past the airtight (=waterproof) fabric of the suit by muscular action, if not (as in Dune), you need to run a gas compressor or heat intensifier semiconductor junction to generate coolth, and the energy used to run this will end up as more waste heat. 

If you are in a cold environment, you can make the sunward side of the suit colour itself dark, absorbent, while the shadeward side is reflective, radiating as  little energy as possible. This mode is compatible with absorbing as much solar energy as available. Inverting this for a hot environment means your solar energy conversion becomes low efficiency, practically useless (as you're reflecting off all the sunlight) even while you're needing more for your cooling system. I strongly suggest that a supplementary power generator be available for hot (or extremely cold) environments.

All this gas storage, energy storage, waste retention and insulation (plus protective armouring of the cloth - gotta be tough, long wearing, next best thing to indestructible) has made the thing thicker and clumsier than I had wanted; I'd hoped to make something you would hardly notice you had on, but it rapidly became clear this was not going to be the case. Lights, communications, ray guns, telemetry and other such power-hungry applications are not included, and will presumably be carried in a back pack. However, a moisture condenser is, and the suit's fabric acts as a radar beacon, lasing at a standard frequency.


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## AlexanderSen (Jan 16, 2014)

Cool~ Those are some good points! 

I was trying to make a slightly different story than the regular sci-fi norms - But what exactly that is a tough question! 

The standard conventions of suits is relatively all the same. I never thought much of suits as anything else than just suits. I was trying to think up some other ideas in which suits could be used and benefit the colonists. Things like bio-organic suits and or self healing technology comes to mind. But also I was thinking there must be something more than just a suit as a suit. In another project, that I am working on when I am not working this one, has enviro-suits which are also fashionable like clothes. Just trying to think up some other functions for these exoplanet suits.


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