A giant step for mankind, I do hope that this will continue for the years to come
NASA spacecraft ‘touches’ the Sun for the first time ever
51–60 of 89 posts
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#52Earlier quoted context omitted.
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.)
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#53Please 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"
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#54Earlier quoted context omitted.
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.
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.
> 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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#55For 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.")
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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#56Earlier quoted context omitted.
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.
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.
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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#57Earlier quoted context omitted.
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.
> 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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#58Since 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 shri…
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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#59From 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 Su…
> 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.
Re: NASA spacecraft ‘touches’ the Sun for the first time ever
#60Earlier quoted context omitted.
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?
IR radiation, in a nutshell.