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Comment by elzbardico | Hacker News Reader

The space surrounding you may not have a temperature but your spacecraft does, and it will lose heat via radiation, batteries and electronics will stop working after your temperature reaches a certain low.

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And: if one designed ones spacecraft / lander with a presumption of being exposed to solar radiation, which peaks around 120°C (250°F), then the temperature-management problem is one of excess heat, not insufficient heat, and would feature radiators and foil insulation to avoid acquiring more heat.

Designing for a wide range of temperatures in space where shedding heat is a challenge and running heaters (during dark/cold periods) is necessary, and where at the best of times re-deploying radiators and heat shields is difficult, let alone when the craft is lying on its side.

So ambient temperature matters. As another comment notes, in most cases, the problem is excess heat and the shedding of it. Particularly for Earth-orbiting satellites, which are subject to 1kW/m² solar radiation and are in shadow for only a small portion of their orbit (less with higher altitudes).

Any moderately active satellite has far more issues with excess heat

It depends on the size of the satellite and its power use. Small spacecraft often don't use enough power to generate enough heat to warm themselves. The problem then is batteries get cold (which is one of the places you need heaters) and become inefficient and then you end up in death spiral. Here the probe likely wasn't generating enough power anyway, so that would almost certainly kill it before the cold.

The problem is less the quantity of heat generated than of shedding that heat. Even modest electronics emit several watts of thermal waste heat, and given that the entire satellite is in a highly-insulating vacuum, as well as subject to solar insolation (at 1 kW/m²), it's easy to exceed thermal budgets.

You can do the sums. Spacecraft lose heat by radiation and if you do the sums for a small spacecraft you can see the equilibrium temperature is low enough that you don't need to take any special measures to shed the heat.

The article clearly states that providing enough power to run the heaters was one of the challenges that led to the death of the probe. Satellites are rarely in the shade for an extended period.

It does, but here we are talking about a spacecraft not exposed to sun radiation and without significant amounts of stored energy to generate heat to overcome the heat losses due.

>The space surrounding you may not have a temperature

Just to be pedantic, it actually does, which is the microwave background radiation. But that doesn't detract anything from your point.

There's also ~80,000 molecules per cubic centimeter on the moon. It's extremely thin but there's still stuff out there it's just a VERY slow transfer because there are so few collisions compared to what you'd get on Earth.

Is that really "space" as opposed to "the lingering effects of the big bang"? (or less interestingly, the temperature of the CMB photon gas)

I don't think a photon can exist outside of space, but I'd be very interested to hear of any alternate points of view on that!

What I mean is that isn't the temperature of "space" -- if we're being pedantic. Such a temperature would presumably be measured by the blackbody radiation of... space, if space were a blackbody.

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