Eating in Space

Roland Piquepaille writes "What do you think astronauts aboard the International Space Station (ISS) ate for Thanksgiving? Roasted turkey? Wrong answer. In "Orbital Thanksgiving," NASA tells us they had tortillas and gives details about food in space. If the dining view, 200 miles over the Earth, is great, preparing meals is quite a challenge. For example, there is no refrigerator or freezer aboard the Station, so food must remain good for long periods at room temperature. And you need to avoid crumbs which could float around. This is why tortillas are favored over bread. This overview contains additional references and includes a picture of a cosmonaut preparing food in the ISS galley."

Comments

No freezers?

[Mondoz]

I guess they didn't want to mention the Enhanced Gaseous Nitrogen Dewar system, which keeps samples frozen at -321 degrees Fahrenheit...
Or perhaps the ARCTIC freezer system, with 38 liters of -20C degree cold stowage...
ISS Fact Sheets

Re:Turkey?

[Yokaze]

> And what's this about "no freezer"? What exactly is outer space, if not cold?

Temperature is the mean kinetic energy of particles per volume. Space is quite empty, which keeps the temperature quite low. But, do you know what the best (heat-) insulator is? Vacuum.

What one usually calls "cold" is not something of low temperature, but something with a lower temperature and a good heat conductance. Hence, a piece of metal of room temperature is cold.
It "drains" the heat from you.

Re:in space, no one can hear farm animals scream

[Kazymyr]

Actually the current state of molecular and cell biology almost makes it possible to grow muscle cells in an organized fashion in a cell culture dish - in other words, growing steaks in the lab. It will definitely be possible to do it for real in a matter of years. Would it be economically viable? Certainly not for a while on Earth, where cheaper alternatives are plentiful - but it could be a solution to avoiding a 100% vegetarian diet on long space missions.

HUGE heat sinks

[roman_mir]

The ISS is cooled down by emmitting infrared radiation through gigantic heat sinks that use two closed loops: one with water - to take the heat out of the stations interior and to the heat sinks and the oher with ammonia - to take the heat out of the water and into the heat sink tubing (ammonia freezes at a much lower temperature than water. Water would just become ice and would clog the tubes.) Now THIS is some heat sink that could solve heating problems of a huge super-computer.
I wonder what did MIR use for cooling down?

I like this chronology - a very exciting reading.

Re:Turkey?

[TarpaKungs]

In space, an object will lose most of it's internal kinetic energy by radiation; it emits electromagentic (EM) radiation in relation to it's absolute temperature. Normally, in warm surroundings, the EM lost is balanced by EM receieved from surrounding objects - so when equilibrium is achieved, the temprature of the object stabilises (assuming no other sources of heat energy).

But, do you know what the best (heat-) insulator is? Vacuum.

No... Conduction is one loss mechanism. There will be little conduction in space. Radiation however is a very significant mechanism too. Check your thermos flask - it's silvered as well as presenting a vacuum barrier.

In space, there is much lower background EM depending on whether you are in sight of the sun or not, so for best effect put your "freezer" out behind the ISS away from the sun and I think you'll find that stuff freezes pretty quickly.

Re:Insulator?

[deander2]

an object in a vacuum will radiate its heat, yes, but that is not why the rubber shattered.

while the vacuum pump was working, it was decreasing the air pressure in the jar. lower the air pressure, lower the temperature of the remaining air. the rubber cooler by the same principle as your air conditioner.

a vacuum is still a great insulator. (that's why my coffee mug here has a vacuum between the inner and outer shells :)

Re:Decreasing air pressure...

[Aglassis]

You said: "Do you have any idea how fast heat radiation will cool an object in space?"

Stefan's Law states: P = (sigma) * AeT^4, where P is the power radiated, (sigma) = 5.6696 * 10^-8 W/(m^2 * K^4), A is the surface area, e is the emissivity, and T is the temperature (in Kelvin). The emissivity can vary from 0 to 1 depending on the properties of the surface. An ideal absorber, which is also an ideal radiator, has an emissivity of 1 and is known as a black body. So, since an object can both radiate and absorb, its net power is P-net = (sigma) *Ae (T^4 - T-0 ^4) where T-0 is the temperature of the surroundings.

What this means is that your turkey is always going to be radiating a certain value depending on its temperature, but depending on where that turkey is (in the shade behind the spacecraft or in front of the spacecraft receiving radiation from the sun) it may cool down or heat up (if the suns radiation is enough to overcome the heat radiated away). If the turkey stays in one place it will come to equilibrium because eventually the radiation absorbed and radiation emitted will equal out whether or not it heated up or cooled down.

On one side note though, in the case where a turkey is in the radiation stream from the sun, because the radiation from the sun comes from only one direction, one side of the turkey would be much hotter than the other.