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As we all know temperature of space is near to absolute zero.Then why super conductors aren't used there?

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Superconducting magnets are used for some astro-particle physics missions, but "As we all know temperature of space is near to absolute zero" is far too simplistic. The presence of the sun means that space vehicles are not, in general, near absolute zero at all. The magnets I mentioned have to carry cryoliquids to stay cold, and when they run out the magnets have to run at lower current in resistive mode. –  dmckee Feb 17 at 5:08
    
This question appears to be off-topic (see dmckee's comment). –  Dimensio1n0 Feb 17 at 5:16
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I don't think the question is off topic. It's a fair question, and the temperature of space (out of sunlight) is indeed near to absolute zero. The problem is staying out of the sunlight. –  John Rennie Feb 17 at 7:14

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The intensity of the light from the Sun at the orbit of the Earth is around 1.4 kilowatts per square metre. For comparison, a domestic heater is usually around 3 kW, so a satellite with a 2m surface area (admittedly this is bigger than most satellites) facing the Sun needs to dissipate as much energy as used to heat your living room. This is in addition to the waste heat produced by the electronics on the satellite. For most satellites it's keeping cool that's the problem, and that's why they're wrapped in reflective foil.

Where you have a satellite that needs to stay really cool, such as the Herschel Space Observatory, the satellite has to carry a supply of liquid helium to cool itself. In fact the Herschel Space Observatory ran out of liquid helium at the end of April last year and can no longer operate.

It's certainly true that if you can stay out of sunlight space is a pretty cold place. If you could avoid all reflected light then in principle you could cool to the 2.7K temperature of the microwave background, and this is cold enough to use superconductors. However this isn't a practical way to operate most satellites.

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