Traveling to the Sun: Why Won't Parker Solar Probe Melt?
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Graphene oxide sheets may be the ideal candidate for solar harvesting. Full radiation spectrum absorbance. High conductivity. Thermoelectric power generation that increases at very high (3000K+) temperatures. Lightweight. Inexpensive. 3D-printable. With cloth-like flexibility.
Might be time to fund a zero-gravity graphene factory in low Earth orbit.
https://phys.org/news/2017-07-gravity-graphene-space-applica...
But in a little more serious manner, if anyone is going in this direction i'd love to hear about it.
Can't we siphon the total energy output of some other star? #NIMBY
To see the kinds of effects this would have on the gas giants would be fascinating. It would probably drastically alter the coriolis banding and spots on Jupiter and Saturn.
Venus would probably be the only other planet affected, and perhaps comet behavior might change. In fact, I wonder if planets would become so cold, that they might produce visible comas as they warm up, when they enter the sun's (now hemispherical) light cone. That's probably the most prominent effect I can see happening.
Plus, it would be fun to screw with societies in other parts of the galaxy that are using their Kepler satellite equivalents. Every time the Earth transits, the light would dip in a way that would lead the observers to think Earth was much larger, thereby much less massive (for the math to work). Great defensive strategy as they would not think our planet was worth pursuing.
Turns out I was wrong and they just used old IMAX projectors they purchased off eBay.
https://astronomynow.com/2018/05/01/old-imax-projectors-simu...
I guess the obvious answer would be "the distance which the Earth is at," but what I really mean is could you be floating around in a spacesuit or some object with minimal shielding and you would neither overheat nor freeze to death.
(100C is the boiling point. 0C is freezing.)
Anyone got a link to a quick and dirty explanation of how the vacuum of space would impact this?
More generally: practically all phase-changes depend on both temperature and pressure. Lower pressure almost behaves like higher temperature... within certain ranges (and it varies for every material).
E.g. for water, note that there are three major regions in its phase diagram[1]. At human-normal scales (the red horizontal line is 1 atmosphere) we see water boil/freeze at 100 and 0 celsius. If you lower the pressure though, you'll see there's a spot where all three phases meet, and below that there's no liquid phase separating solid and gas. When it's in near vacuum, you literally can't have water - ice evaporates (sublimates) directly into a gas, with no intermediate phase.
Given the diagram, this seems to happen somewhere around -60c in a serious vacuum. So in space or on the surface of the moon (without an atmosphere / something pressurizing it) you simply can't have liquid water - a portion of it will evaporate almost immediately, which steals energy from the remaining portion, causing it to freeze. After that, the solid portion just sublimates away (because the sunny side is 127c, well above the temperature needed to turn it into a gas).
[1]: https://en.wikipedia.org/wiki/Phase_diagram#/media/File:Phas...
What I am trying to figure out specifically -- to mental model -- is what impact this has on human comfort, per the original question.
So I have lived in very hot and humid places -- like Georgia, where it is often around 100F in summer -- and I have lived in even hotter places with a much dryer climate -- like the Mojave Desert, where it can get to 115F and I would wait until nightfall to go for walks for exercise at 99F and no sun. Humidity does make a big difference in how uncomfortable a temperature is. If it is hot and dry, you can stay reasonably comfortable if you get enough fluids and electrolytes into you and stay out of direct sunlight.
I'm trying to fit this into a mental model of that sort. Like is a boiling temperature going to burn you? Or, you know "It's a dry heat, man!" only "It's in the vacuum of space, man!"
Thanks to anyone who replies to this.
I imagine some of it depends on what our heat-sensors actually react to. At the least-interesting case, seems like being above boiling without heat would feel fizzy, just because it's physically doing that to the outer layers of your skin. Or something like laser hair removal, where it kinda feels like a hard slap.
So, you don't need the sun at all! Make your spacesuit small and shiny and you can enjoy balmy temperatures deep in the inky blackness of the interstellar void, for as long as your food and oxygen lasts (food and oxygen ultimately being the fuel for your 100W).
Citations: https://en.wikipedia.org/wiki/Thermal_radiation and typing '100 Watt = 0.12 × (5.6704W⋅(10^−8)/(m^2⋅K^4)) × 2 m^2 × x^4 to celsius' into Qalculate
> Parker Solar Probe is powered by two solar arrays, totaling just under 17 square feet (1.55 square meters) in area. They are mounted to motorized arms that will retract almost all of their surface behind the Thermal Protection System – the heat shield – when the spacecraft is close to the Sun.
https://blogs.nasa.gov/parkersolarprobe/2018/05/07/solar-pow...
Solar panels are just more reliable than any heat engine and actually using the temperature differential in a heat engine (stirling or whatever) would decrease the heat shields ability to reject heat. And it'd add mass in the form of radiators with space already at a premium.
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But more in general, I'm super excited about Solar Probe+ (Parker Probe) as well as the completion of the Advanced Technology Solar Telescope (Daniel K. Inouye Solar Telescope (DKIST)). They're both going to be exposing never before sampled, very exciting, territory.
The Solar Probe with actually in-situ measurements of the magnetic field of the corona (as opposed to inferences based on optical Hanle scattering or radio emission). It is going to put a lot of constraints on previously weakly constrained flare and CME models. Maybe in the 9 radius passes it might even detect (or more likely not!) the stupifyingly unphysical entire electron contents of the corona dumping down during flares most models call for.
And the ATST/DKIST with it's diffraction limited imagining and fast optical spectroscopy of the sun at 100s of km scales projected on the photosphere. There's so much going on in the photosphere and chromosphere that right now is just blurry blobs. When resolved I think there's going to be a lot to see.
WRT Stirling generators, there is already work ongoing for arrangement ssuitable to space applications, through new research on nuclear power sources (stirling radioisotope generators, and the Kilopower nuclear reactor). Generally the solution is to mount several Stirling generators such that their torques cancel each other out. Search for "managing the stroke of the pistons" at https://beyondnerva.wordpress.com/2017/11/19/krusty-first-of...
> They are mounted to motorized arms that will retract almost all of their surface behind the Thermal Protection System – the heat shield – when the spacecraft is close to the Sun.
Yes, there's a moving part. It only has to move twice (deploy, mostly retract) but it's still a moving part.
Best thing: no moving parts required!
"The chips that produce an electric field for the Solar Probe Cup are made from tungsten, a metal with the highest known melting point of 6,192 F (3,422 C). Normally lasers are used to etch the gridlines in these chips—however due to the high melting point acid had to be used instead."
I had no idea tungsten was used to make ICs. What kind of density is achieved by laser etching (on tungsten or otherwise)?
One's 1/5 the distance from the Earth to the Sun, the other is 1/5 that distance.
The distance ladder is a good way to think about it.
> 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
Perhaps they meant 4 cm.
On a side note I always thought AUs were a bit silly and self centered....
https://www.youtube.com/watch?v=1-vcErOPofQ&feature=youtu.be...
And does the fact that AU comes from the earth's distance to the sun make it self-centred? Sure, but everyone we need to communicate with would equally find it centred on them. Compared to other measures like "the distance from the king of England's nose to the tip of his outstretched finger" it's quite neutral.
https://en.wikipedia.org/wiki/Parker_Solar_Probe
If one AU is 1 meter, 0.04 AU is 4 cm. So it's, roughly, if 3 feet is between the Earth and the Sun, the probe would pass by the Sun at one and half inch.
(It is obviously easier to think in metric units.)
Or cancer, the disease?
Nice one. It just didn't process. Good for a chuckle
Maybe my limited English skills. Or maybe too tired.
Which is not about understanding the mechanics of the joke (what it's supposed to say) but getting the feeling that it should invoke.
I guess that I'm more into cleverness and subtlety. Humor that directly or indirectly makes fun of people strikes me as sad, not funny.
The parent's joke (about the probe going to the sun at night, since during the day the sun is hot) is both clever (though not original, it's old), and in no conceivable way "directly or indirectly makes fun of people".
My comment has the wrong parent too. On mobile, thought I was actually replying to the "go at night?" smart ass comment. That one was just so basic... good grief.
Normally, we are more serious here, and I read it, drew a blank, again, then chuckled.
I don't know. I mean, even if you went "at night" -- aka directly away from the Sun, always keeping the Earth in between -- you'd never get near the Sun. Unless you set out to circumnavigate the Universe. And in any case, once you got farther than the Moon's orbit, it wouldn't be night anymore, because you'd see the Sun.
So OK, approach the Sun edge-on. So is this a riff on flat-Earthers? I suppose that they might also have the Sun being flat. I can't quite imagine the geometry.
Because it had been destroyed, and became a ring, home of the Sky Dwellers. Or perhaps an orbital ring, as Stephenson has it in Seveneves. But there's nothing about a bombardment in Morgan's "Land Fit For Heroes". And that brings up the question about how a Moon breakup would really go.