How quickly will you actually freeze in space?

[Trachmyr]

I'm trying to throw together a Template for a TL10 spacer pantropic genetic mod... but when I stated to check out what would be needed in terms of Temperture Tolerance, I could not find any detailed data.

Assuming that the Black-Body temerature would be under 200K. Also these people would be more likely to work in the shadow. Also assuming that I would like them to be able to comfortably bear a space environment for about two hours.

From what I've been reading on wiki/NASA... it seems that overheating might be an even bigger concern...

Also consider that the genemods would be using the Doesn't Breathe (Oxygen Storage) advantage, along with Nictitatating Membrane.... thus there would be little moisture escape unless it's needed for cooling.

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So how long does it take for body tempature to drop? After two hours what levels of Temperature Tolerance would be needed? Would I need to be more concerned with overheating?

[David Johnston2]

2 hours? Cold isn't much of an issue except for one thing. Handling things will freeze your hands very quickly. As long as you don't touch anything, your internal heat should be sufficient to avoid problems.

[Ulzgoroth]

Wouldn't Sealed be a good idea for anything exposing itself to vacuum? That would guarantee no unwanted fluid losses.

Body temperature dropping should probably not be happening unless your base species doesn't thermoregulate. Certainly for humans any significant change in core body temperature is a major problem.

It looks like, assuming human size and a surface temperature of 33-37C, you'd be loosing heat at 1kJ per second, which doesn't seem all that bad. Though it'd drain you pretty quickly. In practice, radiative loss might be lower than that because the skin can be allowed to cool below core temperature, but I don't know how low that can go.

Overheating is definitely a potential problem, but I don't think humans actually generate a kW of heat constantly. And equilibrating with the sun isn't a big deal either...the equilibrium temperature of a black-body at earth orbit appears to be about 5 degrees centigrade.

Huh. Am I doing something wrong? This looks too easy.

[Fred Brackin]

Originally Posted by Ulzgoroth

Huh. Am I doing something wrong? This looks too easy.

Probably not. Radiation lags way behind conduction,convection and evaporation as a heat transfer method.

[Anthony]

At human body temperature (37C, 310K) a perfect blackbody radiates heat at about 520W/m^2; over a typical surface area of 1.8 square meters, that works out to 940W. However, humans are likely to not be anything close to a perfect blackbody, a biomod is presumably optimized for these purposes, plus simply wearing clothing would trap a lot of infrared radiation, so it would be fairly straightforward to reduce emissions below 100W, meaning the answer is 'never'; in fact, you'd probably need special designs to get over 250W heat elimination. As a first order approximation, heat output = Calories/hr, so with even modest exercise you can overheat fairly easily.

[Trachmyr]

David Johnston2: Excellent point about handling items... something I'll have to consider since I want these genemods to function without gloves (for [/I]Clinging (Low Gravity 0.1G, Accessability: Bare Feet or Bare Hands)[/I])... perhaps a Resistance (or Immunity) to Frost-bite for short exposures, maybe due to a thick epideral on palms/soles which insulates for a short time then sheds off when damaged...

Ulzgoroth: I want to avoid the Sealed Advantage, and NASA site (concerning vacuum & space suits) indicates that the human body is sufficiently sealed against moisture loss. The primary evaporation occurs at the mouth, nose & eyes. This seems already enough for my needs, so I don't want to add on an advantage that is also going to give immunity to corrives and toxins. It's also TL 11, and I have trouble imagining how this advantage would work without symbiosis of nanomachines (which is illegal in my setting to boot).

Anthony: Thanks for the breakdown. As far as how close they can get to blackbody, I am incorporating the Chameleon advatage that autonomously responds to tempature and radiation, so when needed be their skin can turn jet black... I'm also wondering if fine scales might be more appropriate... but I don't know if this would give any effect.

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I'm also trying to avoid Vaccum Support... from what I can read it primarily stops rapid decompression. NASA also state that the human body expands in a vacuum, and while it doesn't mention that this is imeediately harmful, I can't imagine it would be a good thing after constant exposure. Generally these Genemods will be wearing a Mechanical Counter-pressure Suit to avoid this effect, and Rapid Decompression is still very hazardous to them. Is there anything else that Vacuum Support covers that I'm missing? Is it safe to go without it if wearing a MCP Suit and avoiding Rapid Decompression? I've also considered using the Maximum Duration Limitation and the Accessability Limitation (not against Rapid Decomression) on the Vacuum Support Advantage to be on the "Safe Side"... is that a good idea? I'm trying to avoid TL11 traits from Bio-tech, but with these limitations I can see it becoming TL10... does that seem fair?

Thank You...
-Trachmyr


Edit: Does Tempature Tolerance (Only to Tolerate Body Heat) or perhaps Resistance (Overheating) seem appropriate to avoid overheating in short durations? Many of the Mechanical Couter-Pressure Suits being considered by NASA use sweat to regualte temperature... is that enough?