Is the principle of passing close the Sun with the Parker Solar probe the same as if you pass your hand over a candle flame fast enough you won't get burned?
1 Answer
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No, it's much too slow for that. The Parker Solar Probe's heat shield at least approaches thermal equilibrium on its perihelion passes; your hand passing briefly through a flame does not.
answered Dec 30, 2018 at 18:38
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2$\begingroup$ The Parker Solar Probe is pretty fast but the Sun is huge. $\endgroup$– UweCommented Dec 30, 2018 at 18:59
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$\begingroup$ This answer is wrong as it stands. If the probe were to reach thermal equilibrium at perihelion, most of it would evaporate. It is the whole purpose of the heat shield to prevent equilibrium from happening. What's true is that this works not because of the quick movement but because of the low heat conductivity, but this is a more technical distinction. $\endgroup$ Commented Dec 30, 2018 at 20:57
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3$\begingroup$ @leftaroundabout Well. the surface of the heatshield of the Parker Solar Probe reaches (or at least approaches) thermal equilibrium on its perihelion passes. Would you agree to this modification? $\endgroup$– UweCommented Dec 30, 2018 at 21:01
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$\begingroup$ @Uwe yeah, that would be more accurate, but then it doesn't really answer the question: would the probe eventually reach equilibrium (and thus be destroyed) if it stayed longer at perihelion-distance? Or does the thermal radiation it emits to the back already compensate the heat flow through the shield and thus give a pseudo-equilibrium with steady-state heat flow through the shield? I don't think so (else why would it need water-cooling), but actually I'm not sure. $\endgroup$ Commented Dec 30, 2018 at 21:10
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1$\begingroup$ @leftaroundabout This 2012 paper suggests that the heat shield does indeed reach thermal equilibrium. There's another paper with more complicated simulations, but it mostly focuses on the wind itself. $\endgroup$ Commented Dec 31, 2018 at 0:37