NASA spacecraft ‘touches’ the Sun for the first time ever | Hacker News Reader

NASA spacecraft ‘touches’ the Sun for the first time ever

nature.com

266 pointsperihelions83 comments

Since getting that close takes a lot of DeltaV and I was curious:

>The Parker Solar Probe mission design uses repeated gravity assists at Venus to incrementally decrease its orbital perihelion to achieve a final altitude (above the surface) of approximately 8.5 solar radii, or about 6×106 km (3.7×106 mi; 0.040 au).[35] The spacecraft trajectory will include seven Venus flybys over nearly seven years to gradually shrink its elliptical orbit around the Sun, for a total of 24 orbits.[1] The near Sun radiation environment is predicted to cause spacecraft charging effects, radiation damage in materials and electronics, and communication interruptions, so the orbit will be highly elliptical with short times spent near the Sun.[34]

https://en.wikipedia.org/wiki/Parker_Solar_Probe

Highly elliptical orbits are cheaper to achieve anyway, right? You can get into one directly from your Venus gravity assists, and not have to keep precious fuel to transfer to a circular orbit later on.

Yes.

As a bonus in this particular case, it limits your time in the higher temperatures of the corona; the spacecraft gets time to radiate heat and cool off before the next skim through.

> 6×106 km

Please... 6×10^6 km

I don't know why the wiki doesn't just say six million kilometers.

Or 6 Gigameters.

Scientific notation makes it easier to indicate how many significant digits you have in the measurement.

Or 6e6 km :)

Why not just write 636 km?

It was meant to be 6×10^6 -- as a quick soundness check, the sun's radius is significantly more than 75 km (636 / 8.5) -- though I agree it would probably have been more reasonable to just write "6 million km"

If you’re curious why it won’t melt: https://www.nasa.gov/feature/goddard/2018/traveling-to-the-s...

Basically not much heat is transferred because there's not many particles to do the transfer, like a hot oven.

What I didn't understand was the coolant. It's got to dump whatever heat it picks up somewhere? Just a big radiator?

> It's got to dump whatever heat it picks up somewhere? Just a big radiator?

Yes. The absence of any medium in space makes radiating the only way to get rid of heat.

The article puts some numbers on it, as well:

> That means that while Parker Solar Probe will be traveling through a space with temperatures of several million degrees, the surface of the heat shield that faces the Sun will only get heated to about 2,500 degrees Fahrenheit (about 1,400 degrees Celsius).

I'm a little curious how they were able to determine this before even sending a craft there and measuring it and have a high degree of confidence in its accuracy.

The thing about space is, heat transfer is all radiative. The "dark" side of the probe, which is in its own shadow, faces the darkness of space (which is very cold indeed). Therefore you can put insulation on the side facing the sun, and a radiator on the dark side to remove any heat that gets through the insulation.

But space is a vacuum which is a pretty good thermal insulator. How are they dumping the heat?

Pick a material for the surface of the radiator which has high emissivity.

That is, when the material gets warm, it will convert the thermal energy to electromagnetic energy (light). Some of this light will escape, leading to a cooling effect.

This is known as “incandescence” or “black body radiation”, and it’s why metals glow red hot when they’re heated to a certain temperature. (Though it’s not always red, it can be white, blue, or even UV. Animals are warm enough to glow in infrared, which is what thermal cameras detect).

The physical mechanism is radiative cooling: https://en.m.wikipedia.org/wiki/Radiative_cooling

More details about the specific mechanism on the Parker Solar Probe’s cooling system: https://blogs.nasa.gov/parkersolarprobe/2018/09/14/parker-so...

IR radiation, in a nutshell.

Relevant part: the capturing cups are of metals with high melting points, plus

> The corona through which Parker Solar Probe flies, for example, has an extremely high temperature but very low density. Think of the difference between putting your hand in a hot oven versus putting it in a pot of boiling water

And for the rest of the craft there is a highly reflective heat shield.

are you saying this protects you from Corona? why isn't this in the news?

Putting your head in a hot oven continuously will probably prevent you from dying of the coronavirus indeed.

As does flying to the sun, for that matter. Can't catch corona if you're ~150 million kilometers away from the nearest other person.

The vacuum probably also helps. I'd also expect a few mm of vacuum might do the trick of avoiding contracting covid, though I'd not (as the Dutch say) put my hand in the flame for it.

(Equivalent expression in English might be that I'd not wager a lot of money on it, i.e. that I'm not completely certain given the consequences if it's wrong.)

Corona is dangerous.

I can’t believe you want to make light of it!

Sorry, it’s not sunny.

You'll probably die from the vacuum before any corona will kill you. or is that not 'prevent'?

Also spending most of it's orbit pretty far away from the sun. You can move your hand though an open flame with no issues, but if you keep it in the flame it will get burned.

Not sure I get the oven analogy. If I stick my hand in for a few seconds, sure, but if I was in the oven, I'll burn and die there too.

It's in an elliptical orbit that also flies by Venus so it's like putting your hand for a few seconds twice a year.

> if I was in the oven, I'll burn and die there too.

Eventually. Not momentarily.

It would take you much longer to die in the oven than if you would dive into boiling water. I didn't tried both so I cannot be sure, but I suspect that one can live in a boiling water just for a several seconds, while it is possible to live a few tenths of seconds in the oven.

Finnish saunas regularly go to 100°C (210F). I can personally attest that fifteen minutes in dry 100°C air is very survivable, you just get sweaty. Meanwhile 100°C water burns you almost instantly.

Though it's worth noting that when talking about humans in air the humidity plays a huge role. Sweat cools your body through evaporative cooling, which works better the drier the air is. At 100% relative humidity you can't cool down and eventually overheat, at 10% humidity we can survive some ridiculous temperatures for as long as we can keep sweating.

Yes, some sauna's need you to wear the key of your dressing locker on an arm bracelet. While relaxing nicely in the heat you can instantly burn yourself severely the moment the iron part of the key presses into your skin. (Talking from experience here)

You got it actually, it's all about how long you leave your hand in. And that is why the probe has a very elliptical orbit, so it "touches" the sun briefly and goes back out into space to cool down.

Temperature is not what burns you, it's heat flow that does the burning. A boiling pot has a lot of molecules densely packed together, so heat transfer happens fast. The air inside the oven is hot but will not be as effective in transferring heat to your hand. There is more "thermal resistance" between your hand and the air inside the oven than your hand and the water inside a boiling pot.

Imagine sticking your hand in the oven for 1 second. Now imagine sticking it in a pot of boiling water for 1 second. One you do every day, the other is an immediate trip to the hospital. What’s the difference? Water is far more dense than the air in the oven thus will transfer much more heat to your hand over that same duration.

I like to remind people that if you could suddenly create a mass of living bodies the size of the sun, it would have a higher power density :D

They're going at night, duh

From the article:

  > A NASA spacecraft has entered a previously unexplored region of the Solar System — the Sun’s outer atmosphere, or corona. 

  > The mission’s closest approach is scheduled for 2025 at a distance of just 6.2 million kilometres from the solar surface, well within the orbit of Mercury.

From the paper, it looks like the closest approach was

  > 18.4 solar radii (R⊙ ≡ 6.95 × 10⁵ km) from the center of the Sun

Wait, what? NASA says[1] the corona extends 5 million km, so 6.2 million km would be outside the corona. 18.4 × 6.95 × 10⁵ = 12.788 million km, which is more than twice the quoted number. And according to Wikipedia[2], Mercury's orbit is ~58 million km from the sun. So it's already well within that orbit. I've had a couple beers, but I didn't think I was that drunk already. What's going on?

[1] https://www.nasa.gov/content/goddard/nasas-stereo-maps-much-...

[2] https://en.wikipedia.org/wiki/Mercury_(planet)

I haven’t read any of this cause I’m on my phone but wouldn’t the closest approach occur in 2025? And isn’t the 6.95 quoted the closest distance so far?

I think the 5 million km figure is just an order-of-magnitude/ballpark estimate, not something precise.

"The corona starts at 10,000 kilometers and extends out to about 10 million kilometers, where the gas finally escapes the sun's gravity and becomes part of the solar wind." [1]

[1] https://www.scientificamerican.com/article/i-read-that-the-s...

For one, the NASA article says 5 million miles (12 solar radii), not kilometers. So it's actually about 2/3 the quoted number.

Doesn't NASA have some sort of educational duty? Surely they should be using SI units always so as to avoid exactly this kind of confusion.

I'd rather have them always use both units, so that people would eventually learn intuitively, by example, what a km is relayed to a mile, or a kg to a pound, etc.

Yes, but the primary units should always be SI. They can put the US Customary units in brackets after.

> NASA says[1] the corona extends 5 million km, so 6.2 million km would be outside the corona.

The corona is not a perfect sphere. See the various pictures on https://en.wikipedia.org/wiki/Stellar_corona - it's irregular.

The link to the original paper in the article is wrong, it can actually be found here [1](pdf).

1. https://physics.aps.org/featured-article-pdf/10.1103/PhysRev...

Thanks!

I get the heat part (well, after reading the explanations in the article that is), but how do they send the data back to Earth, considering the amount of EM noise that close to the Sun?

It doesn't. While it's near the sun, it's only collecting data. It transmits the data when its elliptical orbit takes it further away from the Sun.

https://www.space.com/41457-parker-solar-probe-what-next-sun...

For metric system people, if the Sun and the Earth were 1 meter apart, the probe would get as close as 11cm from the Sun.

(site writes: "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.")

The original phrasing is more accurate. "Earth and sun being ... apart" doesnt tell you if you are measuring from the center or surface.

> "Earth and sun being ... apart" doesnt tell you if you are measuring from the center or surface.

Typically in the English language that is understood as surface to surface.

But that's not really touching the sun, is it?

Yes, it is. The Sun is a very large ball of gas with a small one of something that is not gas on the middle (and a gradient between them). This goes well inside the large ball of gas.

The sun doesn't have a solid surface like the Earth - it is a ball of gas that gets progressively less dense as it transitions to vacuum.

But it's getting closer with each pass, and that distance will be down to 4cm by 2025.

11cm is still a long ways away. It's crazy how close yet so far everything is.

Well done. And now, Set the Controls for the Heart of the Sun.

https://en.wikipedia.org/wiki/Set_the_Controls_for_the_Heart...

Here is a link to their press conference zoom call. https://www.youtube.com/watch?v=Lme7EjH8uP4 Lots of other good information and images from the probe.

Maybe we'll finally find Vulcanoids, asteroids in a stable zone within the orbit of Mercury. https://en.wikipedia.org/wiki/Vulcanoid

Harvesting "The Golden Apples of the Sun" [1]

[1] https://en.wikipedia.org/wiki/The_Golden_Apples_of_the_Sun

I didn't even know this was possible to get something that could withstand this much heat and still take valid measurements. This is incredible. Congratulations to the team that made this happen.

Icarus, consider yourself avenged.

That would have been a great name for this probe.

https://en.wikipedia.org/wiki/Sunshine_(2007_film)

> The Parker probe crossed into the Sun’s atmosphere at 9:33 a.m. Universal Time on 28 April of this year. It took several months for mission scientists to download and analyse the data it collected, and to be sure that the spacecraft had indeed crossed the much-anticipated boundary

What an achievement this is! I can't imagine the build up and anticipation the team members endured for months on end to finally get to this point.

If the Moon was 10x as far away from the Earth as it is now then that would still be closer to Earth than this probe ever was to the Sun.

And your point is?

The moon doesn't have a million-degree corona.

Check out this video of the "streamers" the probe encountered in the corona: https://www.youtube.com/watch?v=IQXNqhQzBLM

Please tell me this mission ends with the Venera/Cassini treatment of "let's drop the sucker into the atmosphere and see how long it lasts"

It’s not possible sadly. In order to crash into the sun you’d need to get out of orbit, counter-intuitively. The orbital speeds here are crazy high so the spacecraft would need either a gigantic amount of gravity assists or a gigantic rocket.

Inconveniently, the sun is a loud radio emitter, so it isn't possible to communicate with this probe when it's at a low phase angle with the sun.

This is huge. It’s fun seeing people I worked with mentioned in a news article on a project that seemed so far off when I left the field in 2012.

Are there any photos from the spacecraft just to get an idea how close it is?

I am wondering why the sun looks like from there.

Does anyone know what the differences in intent and mission scope are between this and the Solar Orbiter?

This obviously seems to go a lot closer, but both missions seem similar length and NASA is involved in both.

They're complementary. Parker Solar Probe (PSP) carries a smaller, less capable payload than Solar Orbiter (SO) but it goes closer to the Sun, allowing for direct sampling of the corona. PSP cannot carry cameras for observing the Sun because of how close it gets (heat shield reasons), but SO can. This allows SO to observe the Sun's corona on a large scale, while PSP can validate those measurements with local sample collection.

Humanity at its finest.

A giant step for mankind, I do hope that this will continue for the years to come

This is awesome, the engineering and execution is simply inspiring.

Truly!

The NASA article on the probe mentions its autonomous course corrections abilities. Does anyone have an idea about what kind of onboard CPUs/SoCs do probes like this employ? Which ISAs? How about other hardware like memory and storage? And what kind of programming languages are used to code such internal "systems".

I'm very curious to see if someone can shed some more light on this.

what hppen after that to spacecraft

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