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Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

nasa.gov

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Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#101

Post by jccooper »

monochromatic wrote: post #88
jccooper wrote: post #57

The part of the answer here that NASA always seems to skip (perhaps because it's not as fun as talking about all the cool heat-resistant technology) is that the vehicle is in an orbit that will only take it into the corona for a short time. While the closest approach is very close, its aphelion is (at closest) about the orbit of Venus. This gives it time to cool down after each corona encounter. https://www.youtube.c…

Short on what timescale though? Surely hours/days. Long enough to approach equilibrium, I would think.

Here's a graph of the PSP distance from the sun in solar radii: https://space.stackexchange.com/questions/17562/how-does-the...

The corona can be expected to be out to ~12 solar radii, which suggests about a day of really severe conditions. (The data pass is 30 hours, which suggests that's about right.) That's why it needs to be a really good head shield.

It's smallest orbit has a period of 88 days.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#102

Post by mncharity »

perlgeek wrote: post #72
lifeformed wrote: post #70

Earlier quoted context omitted.

Also, the cool side of the craft will stay cool by radiating its heat away into space.

... which only works due to the low density of corona. In a thick atmosphere like earth, heat radiation comes from all sides, so no chance at radiating off very much heat.

> In a thick atmosphere like earth, heat radiation comes from all sides, so no chance at radiating off very much heat.

Desert nights, without the thermal mass of clouds and wet ground, cool quickly.

Earth is doing "barbeque roll" thermal management. Sitting between bright hot Sun, too hot, and dark cold deep-space sky, too cold, Earth spins, mixing too hot with too cold into not too bad. There seems an opportunity to improve the clarity of science education explanations, down to kindergarten, as the cooling half of that balance is pervasively left unmentioned. I wish I could find a forum where opportunities like this were discussed.

Also fun is using photonic structures to engineer your thermal emission spectrum to concentrate energy at frequencies where the atmosphere is more transparent.[1] So you couple more directly than usual with the deep-space sky.

[1] https://news.stanford.edu/2017/09/04/sending-excess-heat-sky... https://www.nextbigfuture.com/2016/12/cooling-by-radiating-h...

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#104

Post by bdamm »

lifeformed wrote: post #70
Nokinside wrote: post #67

Earlier quoted context omitted.

Thank you. I was wondering just this. Heat resistant material will eventually reach equilibrium where the back side is almost as hot as the front side unless it's cooled somehow.

Also, the cool side of the craft will stay cool by radiating its heat away into space.

Is there a limit to the amount of heat a body of space can transmit via black-body radiation? I wonder if the performance of the heat transfer is going to be a useful measurement for science on this mission. I would think so. I just can't help but wonder how much heat an area of space near a star can have added to it. Is it infinite? Is the limit so high that it's far beyond even the atmosphere of a sun? And are there special areas of space where the heat limit has reached its maximum and if so what does that mean for the properties of that space?

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#105

Post by bdamm »

perlgeek wrote: post #71
netfire wrote: post #66

The article makes it sound like there is no possible way for the probe to melt. Is this actually the case? Is there no possibility that manufacturer defects or a solar anomaly that could cause unexpected problems? I don’t want to downplay the good design and engineering that went into this, but should we be so confident without actually having done something like this thousands of times?

> Is there no possibility that manufacturer defects or a solar anomaly that could cause unexpected problems? There sure is. At least two of the systems (positioning and water cooling) are active systems that could fail. > but should we be so confident without actually having done something like this thousands of times? "we" are confident enough that we rely on it to protect a > 1 billion USD probe. What's the use in…

It's worth noting that the initial orbits will all be fairly far out and they will ease into the tighter orbits after a few years of testing.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#107

Post by tesseract »

close04 wrote: post #61
ComputerGuru wrote: post #17

Earlier quoted context omitted.

> The coolant used for the system? About a gallon (3.7 liters) of deionized water. While plenty of chemical coolants exist, the range of temperatures the spacecraft will be exposed to varies between 50 F (10 C) and 257 F (125 C). Very few liquids can handle those ranges like water. To keep the water from boiling at the higher end of the temperatures, it will be pressurized so the boiling point is over 257 F (125 C).

I just imagined that for an object sent to the Sun they'd want to... overdo it a little. Go for something synthetic that would behave even better or would save 1/2 Kg. I'm just the inquisitive type. Explaining that something is used always makes me wonder "why not something else" :).

Water has a higher specific heat than most substances, and probably the highest of anything that's a liquid across the operating temperature range for the electronics.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#108

Post by Taniwha »

chiph wrote: post #4

Dad joke: "They'll go at night" But really, it's cool that they're using carbon-carbon protection similar to that which was originally developed for the leading edges of the Space Shuttle. And I really want to know how they built foamed carbon for the interior. I'm guessing that they're using white ceramic paint on top instead of a reflective foil shield (like the Webb uses) because the foil would be shredded by the…

Well essentially they are going at night, bringing their own night with them

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#109

Post by flashman »

> If Earth was at one end of a yard-stick and the Sun on the other, Parker Solar Probe will make it to within four inches of the solar surface.

91cm and 10cm, to save anyone else doing the conversion. Also, it seems to understate the closeness: Closest approach is 6.1 million km, which is 1/24th of 1 astronomical unit, but four inches is 1/9th of a yard-stick.

Re: Traveling to the Sun: Why Won’t Parker Solar Probe Melt?

#110

Post by jacquesm »

sebazzz wrote: post #54
mpweiher wrote: post #7

Earlier quoted context omitted.

> Stick your hand into into a pot of water at 100 celsius ..and: please don't! :)

Fast reflexes will prevent major damage. It won't prevent pain though.

As someone with extensive scarring on one arm from a water burn I'd prefer it if you didn't put things like this out there.

Fast reflexes won't help your hand to recover from a bad burn, they won't prevent it either, your hand is much too large to be immersed fully and retracted before substantial damage will occur.

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