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Traveling to the Sun: Why Won't Parker Solar Probe Melt?
- blacksmith_tb 8y agoA very cool mission (pun intended)! It makes me wonder if it would be possible to exploit that huge temperature differential behind the heatshield to generate power...
- greglindahl 8y agoThis is what they actually do: > 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-power-parker-solar-probe-tests-its-arrays/ https://blogs.nasa.gov/parkersolarprobe/2018/05/07/solar-pow...
- superkuh 8y agoI guess that's exploiting the temperature differential for power systems but it's not exploiting the temperature differential for power generation. 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. --- 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.
- greglindahl 8y agoAnother way to think of it is that they already have too many solar panels because the probe has to power itself from Earth orbit to its final orbit near the Sun. So, anything that uses what you've already got (solar panels) with minimum additional mass and risk (the little motors to move the panels mostly behind the heat shield) is a winner.
- AngryData 8y agoThere are ways, piezoelectric devices can generate power off temperature differential. And mechanically you could put a stirling engine on although the torque and rotational force likely would not be ideal.
- azernik 8y agoThermoelectric, not piezoelectric ^_^ 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-a-new-breed-of-reactors-kilopower-part-ii/ https://beyondnerva.wordpress.com/2017/11/19/krusty-first-of...
- jschwartzi 8y agoThat seems really complicated for something that the solar arrays do with no moving parts.
- greglindahl 8y agoNote the quote from a while ago: > 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.
- jschwartzi 8y agoA motor that predictably moves an object from one point to another can be much more reliable than an array of heat-driven reciprocating engines that have to be in constant motion and rely on conducting heat toward the internals of the spacecraft in order to function.
- HarryHirsch 8y ago
- mirimir 8y agoIn Watts' Echopraxia the powersat Icarus does that, exploiting the temperature differential between the hot and dark sides.
- gok 8y agoWhy don’t they just go at night?
- yazr 8y agoBecause they wont be able to observe anything useful ?
- Yetanfou 8y agoThe 'dark side of the sun' sounds pretty interesting to me...
- da_chicken 8y agoIt's cancer. The dark side of the sun is cancer.
- DoreenMichele 8y agoCancer, the constellation? Or cancer, the disease?
- dhruvkar 8y agothe solar arrays on the probe would stop working.
- ddingus 8y agoDamn it. I read this twice. Nice one. It just didn't process. Good for a chuckle
- sp332 8y agoThat's not as close as I was expecting for a solar probe. It's about the same distance as Mercury.
- greglindahl 8y agoParker is at 0.04 AU, Mercury is 0.21 AU.
- superkuh 8y agoOr in more imaginable terms: 9 solar radii out at the closest passes in the far future. Here's an older sim clip showing the process, https://www.youtube.com/watch?v=IClNiZ2-ee4 https://www.youtube.com/watch?v=IClNiZ2-ee4
- greglindahl 8y agoMany people can imagine 0.04 AU and 0.21 AU just fine. 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.
- lucb1e 8y agoI have no clue how large the sun is, for all I know it could be 0.000001AU or 0.01AU, but I do know how hot the sun can be at 1AU and that Mercury is scorched at 0.21AU so that's a lot more imaginable than a multiple of some unknown unit, particularly "in the far future" (sounds to me like 10k years, but given the topic of a single mission, maybe it's 30 years? Or 10? This is super vague, too.)
- greglindahl 8y agoYes, that's the kind of thinking that resonates with me as an astronomer, and when I talk to the general public and non-astronomer scientists, I find that a lot more people have a grasp of how hot it is at 1/5 of Mercury's orbit than 9X the radius of the Sun.
- 8y ago
- ArtWomb 8y agoBaby steps to humanity's first Dyson Sphere ;) 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-applications.html https://phys.org/news/2017-07-gravity-graphene-space-applica...
- Roritharr 8y agoWow. This actually sounds like a fun weekend project I'd like to try my hand on. But in a little more serious manner, if anyone is going in this direction i'd love to hear about it.
- breadAndWater 8y agoI mean, sure. Except for the part where we blot out the only star in our solar system. Can't we siphon the total energy output of some other star? #NIMBY
- ambicapter 8y agoI mean, you could have the sphere cover everything except the solid angle that subtends the Earth and literally nothing would change (on Earth).
- breadAndWater 8y agoI think that would mean only a dyson hemisphere, since Earth is illumnated by the entire hemisphere of the sun that faces us, due to the sun's sheer size. 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.
- apatters 8y agoThis is a very naive question, but is there some distance from the sun at which it would heat an object in space to a temperature that we would consider comfortable? 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.
- DoreenMichele 8y agoAs a wild guess, probably further out then the Earth. The atmosphere here plays an important role in keeping us comfy. Even so, the tropical sun can be too much. Heat waves can be too much. Desert heat can be too much. Etc.
- Groxx 8y agoA brief google informs me that the sunny side of the Moon is around 127˚ Celsius, while Phobos goes up to about -4˚. So somewhere most of the way to Mars probably?
- DoreenMichele 8y agoFor other half-asleep Americans, 127 C is about 260 F. (100C is the boiling point. 0C is freezing.)
- Monory 8y agoAt 1 atmosphere of pressure. Important to remember when we are talking about Moon and such.
- DoreenMichele 8y agoI had to think about that for a bit. I've tried to Google it to better understand it. I am not immediately coming up with an elucidation. Anyone got a link to a quick and dirty explanation of how the vacuum of space would impact this?
- MarcScott 8y agoI thought at first that an IMAX projector must be some sort of solar simulator, and the similar acronym to the ones in movie theaters was just a coincidence. 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-simulate-sun-in-key-test-for-parker-solar-probe/ https://astronomynow.com/2018/05/01/old-imax-projectors-simu...
- TheOtherHobbes 8y agoI love the technology on this - Niobium wire inside sapphire tubes is a total geek out.
- lukasb 8y agoThis is SO COOL
- carloscm 8y agoFrom the article: "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)?