Cooling Comparisons

Three of the most common types of cooling used in everyday life and in spacecraft are:

Passive Cooling
Stored Cryogens
Mechanical Coolers (Mechanical Refrigerators)

Here are tables that compare these 3 types of cooling, as they are used in everyday life as well as in spacecraft.

Passive Cooling

Everyday Spacecraft

Examples Standing in the shade on a hot day.
Cooling a drink by putting it outside in winter. Using sunshades on the sunny side, radiators on the dark side.

Advantages Simple. Simple.

Disadvantages Depends on surroundings:
you can't cool off in the shade unless there's shade;
you can't cool your drink by putting it outside unless it's cold outside. Depends on surroundings;
limited in how cold you can get.

	Everyday	Spacecraft
Examples	Standing in the shade on a hot day. Cooling a drink by putting it outside in winter.	Using sunshades on the sunny side, radiators on the dark side.
Advantages	Simple.	Simple.
Disadvantages	Depends on surroundings: you can't cool off in the shade unless there's shade; you can't cool your drink by putting it outside unless it's cold outside.	Depends on surroundings; limited in how cold you can get.

Stored Cryogens

Everyday Spacecraft

Examples Ice in your drink;
Ice in the cooler you carry to the beach;
Dry ice. Liquid helium in COBE, the Cosmic Background Explorer;
Solid (frozen) argon in BBRXT, the BroadBand X-Ray Telescope (a shuttle payload)

Advantages Easy Relatively easy.

Disadvantages Ice eventually melts;
dry ice eventually sublimes away.
(The verb "to sublime" means "to go directly from solid to vapor without first melting," which is what dry ice does. ) The stored cryogen eventually evaporates or melts;
it's only possible at temperatures where there is a convenient cryogen.

	Everyday	Spacecraft
Examples	Ice in your drink; Ice in the cooler you carry to the beach; Dry ice.	Liquid helium in COBE, the Cosmic Background Explorer; Solid (frozen) argon in BBRXT, the BroadBand X-Ray Telescope (a shuttle payload)
Advantages	Easy	Relatively easy.
Disadvantages	Ice eventually melts; dry ice eventually sublimes away. (The verb "to sublime" means "to go directly from solid to vapor without first melting," which is what dry ice does. )	The stored cryogen eventually evaporates or melts; it's only possible at temperatures where there is a convenient cryogen.

Mechanical Coolers

Everyday Spacecraft

Examples Refrigerators; air conditioners. Mechanical coolers now in development;
one is planned to be added to the Hubble Space Telescope.

Advantages Doesn't melt or evaporate;
keeps running as long as the electricity is on and
as long as it doesn't wear out.
Available in convenient temperature ranges. Doesn't melt or evaporate;
keeps running as long as the electricity is on and
as long as it doesn't wear out.
Available in convenient temperature ranges.

Disadvantages Requires electricity
Expensive to repair or replace. Requires electricity (in short supply on some spacecraft);
Expensive or impossible to repair or replace.
Not yet available in every temperature range.
Some types of coolers require extra electronics to hold down vibration levels.

	Everyday	Spacecraft
Examples	Refrigerators; air conditioners.	Mechanical coolers now in development; one is planned to be added to the Hubble Space Telescope.
Advantages	Doesn't melt or evaporate; keeps running as long as the electricity is on and as long as it doesn't wear out. Available in convenient temperature ranges.	Doesn't melt or evaporate; keeps running as long as the electricity is on and as long as it doesn't wear out. Available in convenient temperature ranges.
Disadvantages	Requires electricity Expensive to repair or replace.	Requires electricity (in short supply on some spacecraft); Expensive or impossible to repair or replace. Not yet available in every temperature range. Some types of coolers require extra electronics to hold down vibration levels.

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Curator: Mark O. Kimball
NASA Official: Eric A. Silk
Last Updated: 09/11/2014