How fast will a spaceship cool off

If your spaceship loses power, your main problem isn't cold, it's breathable air.

If you really want to figure out the temp inside it'd depend a lot on stuff you invent, like the kind of ship, what it's made of, where it is and when, what's on it, the people on it (we do give off heat), etc., etc. As my physics teacher said, there is no such thing as cold, there is only the absence of heat. That really isn't likely to be a primary issue though; it'd be behind several things I can think of.

No specific examples, but:

http://forums.spacebattles.com/threads/heat-loss-in-a-vacuum.89276/

I found an answer through google in about 12 seconds (6th result on the page for my search terms) but it takes into account several things that cornflake mentioned and you were entirely ungracious about that response and a wee bit demanding about someone providing the information for you, so I guess I say go look it up for yourself

The short version is that if your ship loses power, your main problem isn't cold, it's breathable air.

mizor said:

Perhaps I was ungracious, but to be blunt cornflakes answer was insulting and I tend to react poorly to that sort of thing. Did it ever occur to either one of you that when I ask about cooling rates and someone tells me I need to worry about breathable air they are
A: telling me that I'm not bright enough to ask the proper question or
B: they know what I'm going to write about better than I do.

I didn't ask about breathable air because it is totally irrelevant to the scenario I had in mind.

I'll try the Google search again This time with different search parameters

Click to expand...

There was an answer there that you chose to ignore. Equations (like the rate of heat transfer dQ/dt = k deltaT) are useless without a solid knowledge of the ship's design, proximity to a sun, and a host of other factors. You're asking for a straight answer to a complex problem that has no short answer. You need to define several parameters (square surface of the ship, insulating materials and properties, heat transfer coefficient between your ships hull material and a vacuum, etc).

Between hull design and proximity to nearby stars, there's every chance your ship's occupants will fry like eggs if their cooling unit loses power while drifting too close to a star. Drop that same ship at the furthest edges of the universe and maybe they'll be popsicles in minutes.

An interesting tidbit on why space shuttle payload doors stay open:

[FONT=Arial,helvetica][SIZE=-1]The forward 30-foot sections of both doors incorporate radiators that can be deployed; they are hinged and latched to the door inner surface in order to reject the excess heat of the Freon-21 coolant loops from both sides of the radiator panels when the doors are open. (source) [/SIZE][/FONT]

Click to expand...

If heating a shuttle was that important, they'd be routing that heat into the shuttle instead of trying to disperse it.

People are going to interpret your questions in their own ways, and sometimes they're not always 100% helpful or on topic. Don't confuse your misinterpretation of someone's attempts to help with your own insecurities.

Physics BS and material science engineer here -

Heat loss in space by a spaceship will be ONLY through radiation. Conduction and convection are essentially nonexistent in the vacuum of space. Whoever made that post about a thermos - space IS a giant thermos, you don't have to build one into your ship. Radiative loss will come from blackbody emission. Assuming a emissivity of .1 - .2 (typical for metals like aluminum/steel), the ship will lose heat at a rate of 52.37 W/m^2.

The ratio of the ship's volume to surface area will tell you more about how fast it cools down. As others have noted, cooling off is a much smaller problem compared to air.

Also worth noting is how fast you are going compared to the inertial frame in which the microwave background is isotropic. The faster you travel in space, the more blue-shifted the CMB ahead of you becomes. If you are travelling at a significant fraction of the speed of light, the CMB will be hot enough to heat your ship. At near-lightspeed, the CMB will be deadly x- and gamma-rays.

Of course, this is all handwaved away typically, so don't sweat the science too much. There's always a bit of suspension of disbelief necessary for spec-fic.



http://www.wolframalpha.com/input/?i=radiative+heat+transfer&a=*FS-_**StefanBoltzmannLaw.Phi-.*StefanBoltzmannLaw.eps-.*StefanBoltzmannLaw.T--&f2=.1&f=StefanBoltzmannLaw.eps_.1&f3=310+K&f=StefanBoltzmannLaw.T%5Cu005f310+K

susysquark said:

Assuming a emissivity of .1 - .2 (typical for metals like aluminum/steel), the ship will lose heat at a rate of 52.37 W/m^2.

The ratio of the ship's volume to surface area will tell you more about how fast it cools down. As others have noted, cooling off is a much smaller problem compared to air.

Click to expand...

Not to mention the ship will produce heat at a rate of something like 100W per human occupant, and that's assuming they're mostly sitting around doing nothing strenuous.

Depending on the ship's size, design, and population density, it's entirely possible that it won't cool at all so long as the air, food, and water last.

This is still ignoring how much heat might be stored inside the ship to begin with, as well. It's not like the lost heat will only come from the atmosphere and occupants. And there's also the old-school option of just setting things on fire to generate heat--since oxygen is apparently plentiful, if they're losing heat overall they'd be silly not to do that eventually, once the temperature drops noticeably.

Heat loss in space is so slow that it doesn't take much to offset it.

Oh, oh! On a slightly related question - how does heat loss in space compare to heat loss in a submarine completely underwater?

The subs I'm moderately familiar with have double hulls and some kind of insulation or material in between, but the environments are radically different. I've heard proposals that future starships might utilize submarine-like technologies in their construction and environments and, since it would be fairly easy to calculate the surface area of a modern submarine due to its shape, I'm kinda' wondering if that idea is such a good idea after all and thinking that getting rid of heat would definitely be problem.

Having pulled ice from the inside of the hull on a submarine "greater than 450 feet" under the surface of the North Atlantic in January, I'd presume it's quite different.

There's a convection component underwater that doesn't exist in space (which is all radiative, as previously mentioned).

It sure is morbidly fun to put a thermometer against the hull and see it read 29 degrees, Fahrenheit.

susysquark said:

Physics BS and material science engineer here -

Click to expand...

Maybe you better spell that out: Bachelor of Science.

Heat loss in space by a spaceship will be ONLY through radiation. Conduction and convection are essentially nonexistent in the vacuum of space. Whoever made that post about a thermos - space IS a giant thermos, you don't have to build one into your ship. Radiative loss will come from blackbody emission. Assuming a emissivity of .1 - .2 (typical for metals like aluminum/steel), the ship will lose heat at a rate of 52.37 W/m^2.

The ratio of the ship's volume to surface area will tell you more about how fast it cools down. As others have noted, cooling off is a much smaller problem compared to air.

Click to expand...

I recall Apollo 13, the air going bad and the temperature dropping were both problems. They were about four days from returning to Earth, which gives a rough idea of the speed the temperature dropped.

Also worth noting is how fast you are going compared to the inertial frame in which the microwave background is isotropic. The faster you travel in space, the more blue-shifted the CMB ahead of you becomes. If you are travelling at a significant fraction of the speed of light, the CMB will be hot enough to heat your ship. At near-lightspeed, the CMB will be deadly x- and gamma-rays. [/quote]
If you're going a significant fraction of the speed of light, you probably have a propulsion system that keeps you warm... Also, a common solution to radiation (and running into the occasional subatomic particle or hydrogen atom) is an ice shield ahead of the ship. Particles hit the ice which captures the particle and the energy makes the ice evaporate, rather than the particle hitting the metal hull and causing problems.

Of course, this is all handwaved away typically, so don't sweat the science too much. There's always a bit of suspension of disbelief necessary for spec-fic.

Click to expand...

It depends on your target audience. I'm reading recent Analog magazines, and I'm reminded how good SF is with the least amount of handwaving possible.

FOTSGreg said:

Oh, oh! On a slightly related question - how does heat loss in space compare to heat loss in a submarine completely underwater?

The subs I'm moderately familiar with have double hulls and some kind of insulation or material in between, but the environments are radically different. I've heard proposals that future starships might utilize submarine-like technologies in their construction and environments and, since it would be fairly easy to calculate the surface area of a modern submarine due to its shape, I'm kinda' wondering if that idea is such a good idea after all and thinking that getting rid of heat would definitely be problem.

Click to expand...

The outer hull of a submarine is basically at whatever temperature the water is. The conduction (water is pressing against every point on the hull) and convection (as the hull heats water, the water rises and more cool water shows up to replace it) pretty much insures this. A submarine needs a double hull to have any hope of having the inside temperature be anything other than the water temperature.

I'm thinking a double-hulled spaceship would be done mainly for shielding against radiation, needed for longer missions outside of the Van Allen belts, such as to Mars.

benbradley said:

The outer hull of a submarine is basically at whatever temperature the water is. The conduction (water is pressing against every point on the hull) and convection (as the hull heats water, the water rises and more cool water shows up to replace it) pretty much insures this. A submarine needs a double hull to have any hope of having the inside temperature be anything other than the water temperature.

Click to expand...

Along with the more fundamental need of having a way to become bouyant/non-bouyant.

benbradley said:

If you're going a significant fraction of the speed of light, you probably have a propulsion system that keeps you warm... Also, a common solution to radiation (and running into the occasional subatomic particle or hydrogen atom) is an ice shield ahead of the ship. Particles hit the ice which captures the particle and the energy makes the ice evaporate, rather than the particle hitting the metal hull and causing problems.

Click to expand...

I'm not talking about particles hitting the ship, but light - the light that pervades the entire universe. Normally its quite cool, in the microwave range, hence Cosmic Microwave Background. Once you get going though, it becomes anisotropic and red/blueshifted along the direction of travel.

Basically the edge of the universe is always throwing very low energy photons at you. Go fast enough, and those photons start to hit harder, like driving in a downpour, which can heat up your ship when they get absorbed. If you get up to speed but then lose power, you will continue forward at that speed, and the CMB will continue to heat your ship up. If you're going fast enough, the blackbody temperature of the CMB can be blueshifted above the temperature of your ship, which means that the net effect will be a rise in temperature.

Go too fast and the CMB becomes x-rays and gamma rays, and everyone gets cancer. An ice shield would hardly help at that speed.

Many variables. How large is the ship? How good is the insulation? What is the power source?

caw

susysquark said:

Go too fast and the CMB becomes x-rays and gamma rays, and everyone gets cancer. An ice shield would hardly help at that speed.

Click to expand...

An ice shield won't help at all. Long before you have to worry about the temperature of the ship, or cancer, everybody on board will have been fried.

caw

I'm also wondering where this area of space is with no interstellar particles, and how long it would take to get there at a nonrelativistic speed.

benbradley said:

I'm also wondering where this area of space is with no interstellar particles,

Click to expand...

Forget that one. Our universe contains no region without interstellar particles. Space is not "empty".

caw

mizor said:

Perhaps I was ungracious, but to be blunt cornflakes answer was insulting

Click to expand...

No, it wasn't. It was a completely sensible response to the question posed.

mizor said:

I tend to react poorly to that sort of thing.

Click to expand...

Which is your problem. This is a discussion site, and you're not dealing with idiots here.

mizor said:

I didn't ask about breathable air because it is totally irrelevant to the scenario I had in mind.

Click to expand...

Then you should have been more specific about the scenario you had in mind.

You're new. The line under your username says: Learning about thick skin.

Consider this a learning experience. And if you think cornflake's comment was offensive, hang around for a while and you might learn about really contentious discussions.


caw