There is a lot of information on the internet about NASA's Parker Solar Probe mission, including several multi-hundred page scientific reviews and in-depth studies - here's one. But could someone take a moment to explain how something could spend weeks at a time tens of millions of kilometers from the sun?

Is the closest (and final?) approach still planned to be nine solar radii from the surface? It's a swing-by in a highly elliptical orbit, but that's going to be days or weeks, not minutes.

Is it all just based on a really good insulator supporting an amazing temperature gradient, or is there something more complicated going on?

Please try to add something quantitative - numbers, simple calculations, etc. to support your answer.

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above: screen shot from NASA's Solar Probe Plus Fact Sheet note: the link seems to be dead now, but there is plenty of related information available at http://solarprobe.jhuapl.edu/index.php#spacecraft

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above: illustration of NASA's Parker Solar Probe from here. Sun is up - to state the obvious!

  • $\begingroup$ I was really amazed to read about this mission - mentioned in this question about high temperature spacecraft. $\endgroup$
    – uhoh
    Commented Jul 26, 2016 at 12:29
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    $\begingroup$ Joke answer: they're going at night. $\endgroup$
    – Tristan
    Commented May 31, 2017 at 2:48
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    $\begingroup$ @Tristan ;) I thought the'd scheduled it to happen during a solar eclipse. $\endgroup$
    – uhoh
    Commented May 31, 2017 at 3:10
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    $\begingroup$ @Tristan: Didn't North Korea already put an astronaut on the sun's surface a few years ago? That also happened at night. Man, NASA is far behind. $\endgroup$ Commented May 31, 2017 at 23:36
  • $\begingroup$ I knew they landed the first man on Saturn too! $\endgroup$
    – Tristan
    Commented Jun 1, 2017 at 1:47

1 Answer 1


Solar Probe Plus will be protected by an 11.4 cm (4.5 inch) carbon composite shield during it's closest approaches. Furthermore, the highly elliptical orbit will ensure that it won't remain close to the sun for long, although it will be long enough to heat up considerably.

Also of some note is the very narrow profile. The satellite won't have to have much of it facing the Sun, which will allow it to remain relatively cool. The parts not facing the sun will also act as radiators, cooling the spacecraft somewhat.

The solar panels are protected by a liquid cooled system to keep them in operational order. They can also be retracted completely behind the shield if required. At closest approach, they will be in the partial shadow of the shield, allowing the spacecraft some power.

The shield is complete with radiators, minimal structure to the remainder of the spacecraft.

  • $\begingroup$ Can you help find the actual thermal conductivity of this shield - is it outrageously low, or actually similar to things used for insulation in every day situations on earth, like bread or wood? (yes there's also https://youtu.be/Wex_yKfrTo4) fyi figure ES-4 on page ES-9 is pretty interesting - it's not weeks, or is it minutes either. $\endgroup$
    – uhoh
    Commented Jul 26, 2016 at 13:54
  • $\begingroup$ Oh, I'm starting to understand more now. Those side panels between the shield and the body of the satellite (a gaudy yellow-goldish color in the illustration shown in the question) are radiators to cool the back of the heat shield? $\endgroup$
    – uhoh
    Commented Jul 29, 2016 at 23:40
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    $\begingroup$ Yes, that is correct. Also, none of it touches much of the spacecraft, there's minimal thermal coupling between the main body and the heat shield. $\endgroup$
    – PearsonArtPhoto
    Commented Jul 29, 2016 at 23:44

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