18 ms·
Traveling to the Sun: Why Won’t Parker Solar Probe Melt?
- hliyan 8y agoAs 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.
- guidedlight 8y agoExactly. Stick your hand into an oven at 100 celsius ...OR... Stick your hand into into a pot of water at 100 celsius. The difference is that the water molecules are more tightly packed, than the air molecules in the oven. In space, they are quite far apart.
- mpweiher 8y ago> Stick your hand into into a pot of water at 100 celsius ..and: please don't! :)
- sebazzz 8y agoFast reflexes will prevent major damage. It won't prevent pain though.
- mcbits 8y agoMaybe for a fingertip, but I wouldn't try it with a full hand. The water stuck to the hand will take time to cool down no matter how fast you remove it. Unless you're just saying second degree burns don't count as major damage...
- jacquesm 8y agoAs someone with extensive scarring on one arm from a water burn I'd prefer it if you didn't put things like this out there. Fast reflexes won't help your hand to recover from a bad burn, they won't prevent it either, your hand is much too large to be immersed fully and retracted before substantial damage will occur.
- 1ste 8y agoThe article's video described this
- kenjackson 8y agoIs that also a reason that you feel warmer in high humidity heat?
- tgb 8y agoThat's only part of it - sweat not being able to evaporate is another part. I'm not sure which is the bigger effect.
- Sharlin 8y agoAs explained in the article. > Temperature measures how fast particles are moving, whereas heat measures the total amount of energy that they transfer.
- deleted 8y ago[deleted]
- chiph 8y agoDad joke: "They'll go at night" But really, it's cool that they'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. I'm guessing that they'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.
- thedancollins 8y agoTexas A&M, represent!
- kijin 8y agoI'm curious about the foam, too. Normally, foam contains a lot of air. But that kind of foam will blow itself apart in a vacuum. How do they make foam where all the air pockets are replaced with vacuum? Is vacuum-filled foam a better or worse insulator than air-filled foam?
- noir_lord 8y agoI think it would be better if it was vacumn voids rather than air filled since air will conduct heat via conduction.
- rubatuga 8y agoFoam can be made and slowly evacuated. Vacuum filled foam is a better insulator
- jstanley 8y agoIt could be open-cell foam instead of closed-cell foam. In earth atmosphere the cells would still be filled with air, but the air would be able to leave without blowing the foam apart.
- dghughes 8y agoAnd if the foam cells have a vacuum in them (in? lack of?) how does it not implode when on earth.
- MichaelMoser123 8y ago>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. 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?
- implements 8y agoNot a scientist, but I assume using "radiative heat transfer" ie a hot surface shielded from the sun emitting thermal radiation away from the spacecraft.
- MichaelMoser123 8y agoYes, but the shield would have two sides, where one of them is facing the sun.
- ourmandave 8y agoMelting points: sapphire - 3,722°F (2,050°C) niobium - 4,491°F (2,477°C)
- SomeHacker44 8y agoImportantly, they likely have very different thermal conductivity and and specific heats. They probably also need to have reasonably similar thermal expansion coefficients so heating and cooling cycles do not cause them to strain and break.
- known 8y agoCan we use same probe to travel to Earth's core?
- close04 8y agoAny reason why they're using water for cooling? There's no other liquid with lower density and perhaps better thermal properties? 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.
- ComputerGuru 8y ago> The coolant used for the system? About a gallon (3.7 liters) of deionized water. While plenty of chemical coolants exist, the range of temperatures the spacecraft will be exposed to varies between 50 F (10 C) and 257 F (125 C). Very few liquids can handle those ranges like water. To keep the water from boiling at the higher end of the temperatures, it will be pressurized so the boiling point is over 257 F (125 C).
- close04 8y agoI just imagined that for an object sent to the Sun they'd want to... overdo it a little. Go for something synthetic that would behave even better or would save 1/2 Kg. I'm just the inquisitive type. Explaining that something is used always makes me wonder "why not something else" :).
- tesseract 8y agoWater has a higher specific heat than most substances, and probably the highest of anything that's a liquid across the operating temperature range for the electronics.
- perlgeek 8y agoNot a spacecraft engineer, merely somebody who has studied physics a long time ago, so take my answer with a grain of salt. Basically, there are two ways you can design a cooling system: one that involves phase change, and one that simply transports heat from A to B by moving a heat carrier, usually a liquid. Phase change systems typically have a higher efficiency, because the phase change has larger relative energy than heat capacity. But it also has two disadvantages: it only works near the boiling point of the medium, and you need to deal with all the pressure changes that come with a phase change. The Parker probe seems to use a "mere" transport, and there the heat capacity and the working range of the medium is very important, and water is a pretty good choice on both of these criteria. Oh, and you also don't want something very corrosive to destroy your expensive space craft from the inside :-) IIRC the ISS uses two cooling systems, one based on water that is used throughout the station, and then an ammonium-based system that takes the heat off the water and transports it to the heat radiators. But on the ISS, maintenance is possible.
- JonoW 8y ago>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. I'd love to get some deeper insight into how NASA writes and tests software, I can only guess it's a million miles from how most of us work. Anyone know of any good talks, articles from engineers there?
- Aaargh20318 8y agoHere's an article about it I read a while back, interesting read: https://www.fastcompany.com/28121/they-write-right-stuff https://www.fastcompany.com/28121/they-write-right-stuff
- marsRoverDev 8y agoThis redundant software and hardware setup typically isn't necessary when humans aren't involved. The space shuttle system is similar to what you will find on a Boeing or Airbus aircraft. Redundant software, written by different people in different countries with completely different cultures in different languages (on purpose), running on multiple machines with different hardware and voting on the decisions to be made. It is complete overkill when "all" you're going to lose is a robot and some pride, as with a space probe you want to have lots of features and this level of safety is very restrictive on development effort. More than likely, the spacecraft in question is written in C or C++ with the help of RTEMS or VxWorks. It is probably running a radiation hardened, very slow processor.
- deleted 8y ago[deleted]
- rtkwe 8y agoThey don't do 3x calculations and voting but they do often have redundant computers they can switch over to in case of failure. Curiosity had to switch to it's 'B-side' computer back in 2013 when A-side had a memory issue. Even when not carrying humans it's still a billion/million dollar mission that probably wouldn't be replicated for a while if ever (within the researchers life times at least) that could be scuttled by a softwer bug. If anyone is interested JPL publishes their code standards doc for C: https://lars-lab.jpl.nasa.gov/JPL_Coding_Standard_C.pdf https://lars-lab.jpl.nasa.gov/JPL_Coding_Standard_C.pdf
- austincheney 8y agohttp://earthsky.org/space/heat-shield-parker-solar-probe http://earthsky.org/space/heat-shield-parker-solar-probe 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. > 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? I suspect the answer to all those questions is simply gravity, but it will be nice to verify such things with data.
- hutzlibu 8y ago"Why is the corona itself millions of degrees hotter than the surface? I suspect the answer to all those questions is simply gravity, but it will be nice to verify such things with data" Can you explain your hypothesis a bit?
- smueller1234 8y agoNot GP, but here's an article that talks about it. Note that this is relatively recent. It's not something that was thoroughly understood in ancient times exactly. https://www.nasa.gov/feature/goddard/sounding-rockets/strong-evidence-for-coronal-heating-theory-presented-at-2015-tess-meeting https://www.nasa.gov/feature/goddard/sounding-rockets/strong...
- superkuh 8y ago> https://www.nasa.gov/feature/goddard/sounding-rockets/strong-evidence-for-coronal-heating-theory-presented-at-2015-tess-meeting https://www.nasa.gov/feature/goddard/sounding-rockets/strong... It explains the temporal heating behavior at some scales. But it doesn't give a mechanism of heating. It could be electron beam target heating. But it could also be mediated by plasma waves. The electron beams need acceleration and the most common suggestion is x-point magnetic reconnection providing up and down voltage gradients due to changing magnetic field. But the amount of electrons needed is unphysically large; the entire electron contents of the relevant volume of the corona. There are plasma wave models that don't require unphysically large parameters. These two (and a couple other) options aren't clarified by the observation of heating profiles. With the launch of Parker Solar Probe and the DKIST (diffraction limited solar telescope) the two models above will finally be testable. Spectroscopy of ion species by DKIST will tell what kind of heating is happening and Solar Probe will be there to measure the input from the corona.
- TheSpiceIsLife 8y agoPrevious discussion https://news.ycombinator.com/item?id=17569741 https://news.ycombinator.com/item?id=17569741
- Sreyanth 8y agoNot 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're learning now is not really a waste of time.
- deleted 8y ago[deleted]
- jeandejean 8y agoThe article and the videos it contains are amazingly clear. Cannot wait for the first results of that mission! I'm always amazed by NASA great endeavors, and how these scientists can be so sure their probe are not going to melt...
- newscracker 8y agoTowards the end, it says: > “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.” What a phenomenal piece of engineering! The article was not only fascinating to read as a non-astronomer/lay person, but it also makes it all look like child’s play, the way they decided what materials to use and how. > “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.“ 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! :) [1]: https://en.m.wikipedia.org/wiki/TPS_report https://en.m.wikipedia.org/wiki/TPS_report
- cryoshon 8y ago>The article was not only fascinating to read as a non-astronomer/lay person yeah, this article was a masterpiece of science writing. all of the difficult concepts were boiled down into very fruitful analogies and metaphors which clarified things succinctly.
- samstave 8y agoYeah... so if you could just come in on SUNday... that'd be great. thanksssss.
- earenndil 8y agoCorrect me if I'm wrong, but isn't space actually not cold at all -- there's barely any matter there to have a temperature?
- lisper 8y agoThe effective temperature of a vacuum is the temperature of whatever is on the other side, because that determines whether radiated energy is emitted or absorbed. For most of space, the "other side" is the cosmic microwave background, which has a temperature of about 3K. So yes, space is generally pretty frickin' cold.
- callumprentice 8y agoSome of the most incredible astronomy shots I've seen are of close(r) ups of the sun - I can't wait to see what Parker sends back as it closing in on the Sun.
- jccooper 8y agoThe part of the answer here that NASA always seems to skip (perhaps because it'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 very close, its aphelion is (at closest) about the orbit of Venus. This gives it time to cool down after each corona encounter. https://www.youtube.com/watch?v=cMNQeCWT09A https://www.youtube.com/watch?v=cMNQeCWT09A
- Nokinside 8y agoThank you. I was wondering just this. Heat resistant material will eventually reach equilibrium where the back side is almost as hot as the front side unless it's cooled somehow.
- lifeformed 8y agoAlso, the cool side of the craft will stay cool by radiating its heat away into space.
- perlgeek 8y ago... which only works due to the low density of corona. In a thick atmosphere like earth, heat radiation comes from all sides, so no chance at radiating off very much heat.
- mncharity 8y ago> In a thick atmosphere like earth, heat radiation comes from all sides, so no chance at radiating off very much heat. Desert nights, without the thermal mass of clouds and wet ground, cool quickly. Earth is doing "barbeque roll" thermal management. Sitting between bright hot Sun, too hot, and dark cold deep-space sky, too cold, Earth spins, mixing too hot with too cold into not too bad. There seems an opportunity to improve the clarity of science education explanations, down to kindergarten, as the cooling half of that balance is pervasively left unmentioned. I wish I could find a forum where opportunities like this were discussed. Also fun is using photonic structures to engineer your thermal emission spectrum to concentrate energy at frequencies where the atmosphere is more transparent.[1] So you couple more directly than usual with the deep-space sky. [1] https://news.stanford.edu/2017/09/04/sending-excess-heat-sky/ https://news.stanford.edu/2017/09/04/sending-excess-heat-sky... https://www.nextbigfuture.com/2016/12/cooling-by-radiating-heat-into-space.html https://www.nextbigfuture.com/2016/12/cooling-by-radiating-h...
- nextstep 8y agoInches? A yard stick? Millions of degrees Fahrenheit? I’m American and I’m embarrassed by this. This is science, make it easy for people to understand. Use SI units, please.
- trgv 8y agoIt's written for a general American audience so it makes sense to use those units.
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- netfire 8y agoThe 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? 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?
- perlgeek 8y ago> Is there no possibility that manufacturer defects or a solar anomaly that could cause unexpected problems? There sure is. At least two of the systems (positioning and water cooling) are active systems that could fail. > but should we be so confident without actually having done something like this thousands of times? "we" are confident enough that we rely on it to protect a > 1 billion USD probe. What's the use in adding a lot of ifs and maybes to some piece of marketing/explanation? If it fails, adding some ifs and maybes to a marketing video won't really change anything.
- netfire 8y agoDoesn’t it undermine the credibility of NASA if something goes wrong? The public who is the audience for this article is also paying the bills (through taxes). I’d settle for just changing “won’t melt” to “shouldn’t melt”. I think that appropriate for something that’s never been attempted.
- dawnerd 8y agoEither way we’re chucking lots of money at the sun so if it fails we still learn something, not to mention developed a lot of technologies along the way.
- netfire 8y agoFor sure, but it would be a shame if NASA lost confidence and trust (and possibly funding) with their stakeholders (the public), because they weren’t more upfront about the potential risks. As a scientific organization that has experienced significant (and expensive) failures before, I expect better.
- msravi 8y ago> 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. That explains why energy is not transferred by conduction or convection to the spacecraft. But what about energy (heat) transfer by radiation? Why won't the spacecraft get all the energy from radiation and have its temperature shoot up?
- andbberger 8y agoRadiant shielding
- trhway 8y agoWith 200km/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 :)
- cwmoore 8y agoA key sensor (Faraday cup [1]) for studying the solar wind, outside of the shield, was constructed of not one but apparently four varieties of unobtainium: Titanium-Zirconium-Molybdenum alloy, acid-etched tungsten, sapphire crystal tubes, and niobium wiring. All together these could make a fascinating engagement ring. [1] https://en.wikipedia.org/wiki/Faraday_cup https://en.wikipedia.org/wiki/Faraday_cup
- FigmentEngine 8y agogo at night...
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- flashman 8y ago> 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. 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 1/24th of 1 astronomical unit, but four inches is 1/9th of a yard-stick.
- gersh 8y agoThey have a nice theory that the spacecraft won't melt when it gets close to the sun, but do they really know for sure? NASA doesn't succeed on every mission. It is possible something will go wrong, and the probe will melt.
- jogundas 8y agoThis 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.
- otto_ortega 8y agoIt blows my mind to think that we DO have materials that can withstand such temperatures, even after understanding the part about heat transfer. I hope that kind of materials can be mass-produced on the short term future to be used as insulation for homes!