Keeping objects in space cool

As far as I remeber there was a danger when Discovery had to be repaired in space -the danger had to do with parts of the Shuttle being hot.

I am not sure about it but I think those parts of the Shuttle had got their heat from sunlight. So what about a shield against sunlight to keep onjects cold? Is it a challenge to provide mirros or plates to keep an object behind? Or is the problem the required size simply?

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Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Probably just the space and mass required. Also, keep in mind that space vehicles -- from satellites on up -- tend to use rotation as a sort of thermostat, making sure that all the parts are heated evenly like a piece of meat on a rotisserie. Putting up a sunshade would keep the entire vehicle from heating, and might require a more extensive heating system for life support -- I'm just guessing here, let's see what one of our resident experts has to say.

It would be sufficient if the temperature could be regulated up or down to that level required or safe for working on a part of a vehicle. May be that there are activities which require higher temperatures and other activities which require lower temperatures.

The focus in the media here was on differences in temperature between different part sor regions of the Shuttle. So another goal could be to keep all parts or regions of a vehicle at the same temperature.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Read Sundiver by David Brin for a way of keeping ships cool - does require a way of converting heat directly to electricity.

James

May be that's no problem if there simply would be a shield against sunlight. The shield could serve as a solar power plant in space truning the energy into microwaves and beaming it down to Earth or over to a satellite, a space station or even a vehicle.

This is called "Kuppelproduktion" in Economics as a german term - the english term may be "joint production" or so. The "joint" can't be avoided and might be compared to symbiosis perhaps.

A technology to keep vehicles cool and at non-varying temperature during repairs or while in a spacedock may be a power generating technology in parallel and then spacedocks may be located at solar power plants mostly if not allways. May be very comfortable and advantageous.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

An article under www.wissenschaft.de is reporting today a belgian and an american physicist have found a new concept to of cooling - that concept makes use of Brown's movement of molecules. The article refers to Physical Review Letters, Vol. 96 article 210601 ( http://link.aps.org/abstract/PRL/v96/e210601 ).

There is a boom not larger than a small molecule equipped at its ends with one paddle each. A difference in tempearture between the two ends word turn the boom. An external force could turn the boom the opposite direction which would reduce the temperature.

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The concept has been proposed for CPUs - but might there be a chance to equip tanks or the ends of tanks by thousands, millions or billions of such paddles and thus keep tanks very cold or to keep very cold other objects in space and even if the object. vehicle, station, satellites is on the day side of Earth or any other planet?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

How about modifying Sterling engines into wide flat versions that could use larger surface heat sinks to the interior. Hot to warm, warm to cold! Yeah, now that I'm typing this, I realise the weight would make this a waste of time to consider. Easier just to roll. Still, perhaps we could have a nose section that deliberately allows itself to heat up, so energy could be extracted. Some telescopeable rods supporting a sunshade might be useful, but is it really worth it? Especially when we only have ten to fifteen flights left in the shuttles.

With luck the next work horse will be designed with some novel energy extraction innovations incorporated into the skin.

An article under www.wissenschaft.de today is reporting about another alternative way to cool things.

Interesting is that solar power is used und solar cells are involved. the electricity generated by them is used to cause and make use of the thermoelectric effect.

The thickness still is in the millimeter- to centimeter-range but the next step is get below 1 millimeter.

Of course - at present the applications thought of are terrestrial only.

The article refers to www.solar2006.org/program/saag.htm#WEDN ... Y_12,_2006 and http://www.rpi.edu/index.html .

But in space there is much more solar power than down here - so the thermoelectric effect should be usable in space the more.

What about this?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Under www.bernd-leitenberger.de I found the information that MESSENGERs sunshade will become 370° C to 450° C hot at it's sun-faced side while what's shaded by it will have a temperature of 20 K only. Let's assume that 20 K is a typing or writing error and 20° C are meant - then there is a difference of 350° C to 430° C.

So couldn't such a sunshade be used to keep propellants in orbital propellant depots etc. as cool as possible? Couldn't it keep the temperature even as low as required to keep boil-off within a margin of less than 5%?

And what about using it for the purpose I had in mind in the initial post?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Why not use the temperature differential to generate power using thermocouples in the same way that a RTG works?

I don't think it is a typo.

A shaded spacecraft surface will cool to the "ambient temperature" of space given enough time an no conduction from the rest of the spacecraft. The background temperature of deep space is about 3K, though I suspect it is higher near planets and stars (not talking about very close to stars, when the temperature climbs rapidly due to interaction with particles/radiation of Sun).

Thus, once shaded, the spacescraft surface will radiate (or conduct) off temperatures until the spacecraft reachs an equilibrium temperature or some mechanism (internal/external) changes things.

Take the reported temperutres on the Moon ref:

Mean surface temperature (day) 107°C
Mean surface temperature (night) -153°C
Maximum surface temperature 123°C
Minimum surface temperature -233°C

Thus a deeply shaded spacecraft surface on the Moon would be around 40 K. I would suspect a spacecraft away from the Moon or Earth could get slightly cooler.

Keeping the propellants cool in space usually isn't the issue. In fact, just the opposite is a problem. For example, some thrusters on satellites use Catalyst Bed Heaters to work efficiently.

Keeping propellants cool while still on the pad, is definitely an issue though.

- Alistair

Hello, alistair,

I am thinking about the temperatures cause by the sun and some posts mentioning boil-off-problems in space.

Also the problem might be the larger the closer to the sun a vehicle is. If mankind will become a space fairing civilisation taht also goes to Venus or Mercury either propellant for return will have to be carried there each flight or orbital propellant depots will have to be installed. Because of the closer proximity of the sun at those two planets the heating is increased - and keeping the propellants cool is harder.

But as I said I remember having read posts mentioning boil-off-problems in space regarding LOX and LH2.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

The article "Ambitious NASA Probe to Fly Through Sun's Fringe" ( www.space.com/businesstechnology/080521 ... probe.html ) is reporting that a heat shield may be developed that is capable to protect a probe against a heat of 1,400 degrees Celsius. It will be .

It will be applied in 7 million km distance from the sun - which may have another interesting implication.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Under www.wissenschaft.de there is an article today telling that Polarpolymeres under investigation at present because they might used as cooling when set to some voltage.

They then turn from an unorganized state into an organized state releasing temperature. Removal of the voltage or current causes them to heat up again.

The idea at present is also that sits of sportsmen or fier men can be cooled down this way.

Scientists achieved a cooling by 12° C this way.

The article also says that those Polarpolymeres could be applied to heat something also.

In space solar power might provide the electricity required. But what abou applying electrostatic charged environemnets to achieve the opposite effect? Might the solar wind getting down to the martian surface be applied?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

The article "New Thin Skin to Protect Tiny Spacecraft" ( www.space.com/businesstechnology/080819 ... craft.html ) is reporting that

I am not sure from this if the film is cooling if it is given the electrival cahrge - but if so then it would cool the more the closer to the sun it is located. Then the question would be if the effect can be increased so that it can keep a vehicle at any Earth-like temperature even at the distance of Mercury to the sun.

Wirtschaftswoche was reporting about a colling effect of colours on Earth. BASF has developed black pigments that can reduce the temperature by 20 degrees Celsius.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)