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

Towards the end, it says:<p>&gt; “After launch, Parker Solar Probe will detect the position of the Sun, align the thermal protection shield to face it and continue its journey for the next three months, embracing the heat of the Sun and protecting itself from the cold vacuum of space.”<p>What a phenomenal piece of engineering! The article was not only fascinating to read as a non-astronomer&#x2F;lay person, but it also makes it all look like child’s play, the way they decided what materials to use and how.<p>&gt; “And to withstand that heat, Parker Solar Probe makes use of a heat shield known as the Thermal Protection System, or TPS, which is 8 feet (2.4 meters) in diameter and 4.5 inches (about 115 mm) thick.“<p>So is someone going to be bothering someone else about TPS Reports [1] over the expected seven year span of this probe? Sorry, I couldn’t resist making that reference! :)<p>[1]: <a href="https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;TPS_report" rel="nofollow">https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;TPS_report</a>

Not a rocket scientist, but this article is very well written for an audience with a minimal understanding of Physics and Chemistry. Articles like these help high school students realise that what they&#x27;re learning now is not really a waste of time.

Dad joke: &quot;They&#x27;ll go at night&quot;<p>But really, it&#x27;s cool that they&#x27;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.<p>I&#x27;m guessing that they&#x27;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 solar particles.

The part of the answer here that NASA always seems to skip (perhaps because it&#x27;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 <i>very</i> close, its aphelion is (at closest) about the orbit of Venus. This gives it time to cool down after each corona encounter.<p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=cMNQeCWT09A" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=cMNQeCWT09A</a>

&gt;This all has to happen without any human intervention, so the central computer software has been programmed and extensively tested to make sure all corrections can be made on the fly.<p>I&#x27;d love to get some deeper insight into how NASA writes and tests software, I can only guess it&#x27;s a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?

&gt; 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.<p>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&#x2F;24th of 1 astronomical unit, but four inches is 1&#x2F;9th of a yard-stick.

&gt;Another challenge came in the form of the electronic wiring — most cables would melt from exposure to heat radiation at such close proximity to the Sun. To solve this problem, the team grew sapphire crystal tubes to suspend the wiring, and made the wires from niobium.<p>are these wires on the outside of the spacecraft? but what about the silicon of all the electronic stuff that this thing must be keeping? The cooling surface would also get a bit hot (it would always get some more energy at some rate), so how does the coolant transmit any heat away from the probe?

As I understand, temperature is a measure of how fast atoms and molecules are vibrating, and not a measure of how much energy per unit area of contact can be transferred in a unit time.

Previous discussion <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=17569741" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=17569741</a>

They have a nice theory that the spacecraft won&#x27;t melt when it gets close to the sun, but do they really know for sure? NASA doesn&#x27;t succeed on every mission. It is possible something will go wrong, and the probe will melt.

<a href="http:&#x2F;&#x2F;earthsky.org&#x2F;space&#x2F;heat-shield-parker-solar-probe" rel="nofollow">http:&#x2F;&#x2F;earthsky.org&#x2F;space&#x2F;heat-shield-parker-solar-probe</a><p>It appears the heat shield is a carbon sheet sandwich. At first I was guessing some form of tungsten-carbine, but that is the traditional material of NASA heat shields.<p>&gt; Why is the solar wind a breeze closer to the sun but a supersonic torrent farther away? Why is the corona itself millions of degrees hotter than the surface?<p>I suspect the answer to all those questions is simply <i>gravity</i>, but it will be nice to verify such things with data.

&gt; Particles may be moving fast (high temperature), but if there are very few of them, they won’t transfer much energy (low heat). Since space is mostly empty, there are very few particles that can transfer energy to the spacecraft.<p>That explains why energy is not transferred by conduction or convection to the spacecraft. But what about energy (heat) transfer by radiation? Why won&#x27;t the spacecraft get all the energy from radiation and have its temperature shoot up?

A key sensor (Faraday cup [1]) for studying the solar wind, outside of the shield, was constructed of not one but apparently four varieties of <i>unobtainium</i>: Titanium-Zirconium-Molybdenum alloy, acid-etched tungsten, sapphire crystal tubes, and niobium wiring. All together these could make a fascinating engagement ring.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Faraday_cup" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Faraday_cup</a>

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?<p>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?

Any reason why they&#x27;re using water for cooling? There&#x27;s no other liquid with lower density and perhaps better thermal properties?<p>I imagined they would try to save weight in some places if it allows them more freedom in others. Although I have no idea how much water is used in the first place so it might be a moot point.

It blows my mind to think that we DO have materials that can withstand such temperatures, even after understanding the part about heat transfer.<p>I hope that kind of materials can be mass-produced on the short term future to be used as insulation for homes!

With 200km&#x2F;s deep orbit we should have probably brought several tons of fuel to do Oberth burn say for a piece of the probe which would then pass by the Vojager in a few years and be on track to get to alpha centauri in several thousand years :)

The article and the videos it contains are amazingly clear. Cannot wait for the first results of that mission! I&#x27;m always amazed by NASA great endeavors, and how these scientists can be so sure their probe are not going to melt...

This mission is also very cool in the sense that the period from launch to first interesting data is short. There is going to be a Venus flyby on 28 Sep, and a Sun flyby on 1 Nov.

Some of the most incredible astronomy shots I&#x27;ve seen are of close(r) ups of the sun - I can&#x27;t wait to see what Parker sends back as it closing in on the Sun.

Can we use same probe to travel to Earth&#x27;s core?

go at night...

Inches? A yard stick? Millions of degrees Fahrenheit?<p>I’m American and I’m embarrassed by this. This is science, make it easy for people to understand. Use SI units, please.