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NASA Plans Probe to the Sun
FudRucker writes "For more than 400 years, astronomers have studied the sun from afar. Now NASA has decided to go there. 'We are going to visit a living, breathing star for the first time,' says program scientist Lika Guhathakurta of NASA Headquarters. 'This is an unexplored region of the solar system and the possibilities for discovery are off the charts.'"
The problem isn't to contain such a temperature, but to do it in a way that is compatible with space travel (i.e. not involving heavy and brittle insulation.)
GAAH! MY PRINTER IS ON FIRE!!! PUT IT OUT! PUT IT OUT!
No, what we need is some sort of material that can reflect away the radiation, and also has a ridiculously high specific heat. Hmmm, what could we use to reflect electromagnetic radiation... hmmm, something reflective... what do have that's reflective? Anyone?
http://en.wikipedia.org/wiki/Image:TPScube.jpg
I like to place meaningful quotes in my sig, so people will know that I know what meaningful quotes are.
Yea we do, the outer layers aren't much hotter than say the core of a nuclear reactor. Of course dissipating excess heat will be impossible so its not going to last very long.
No. Not Really.
... "Above the temperature minimum layer is a thin layer about 2,000 km thick, dominated by a spectrum of emission and absorption lines. It is called the chromosphere..." ... "Above the chromosphere is a transition region in which the temperature rises rapidly from around 100,000 K to coronal temperatures closer to one million K." http://en.wikipedia.org/wiki/Sun
And certainly not at the temperature of the Sun's corona (which probes will most likely have to travel through to get to the inner 'cooler' layers..)
This is where we need 'shielding' technology similar to Star Trek, or to jump physical dimensions directly into the desired location with technology similar to Event Horizon, etc..
"The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K."
"The chemical element with the highest melting point is tungsten, at 3695 K (3422 C, 6192 F) making it excellent for use as filaments in light bulbs. The often-cited carbon does not melt at ambient pressure but sublimates at about 4000 K; a liquid phase only exists above pressures of 10 MPa and estimated 4300-4700 K. Tantalum hafnium carbide (Ta4HfC5) is a refractory compound with a very high melting point of 4488 K (4215 C, 7619 F)" http://en.wikipedia.org/wiki/Melting_point
Even diamonds are not tough enough... Above 1700 C (1973 K / 3583 F) diamonds are converted into graphite.
If you go here
[snip]So wouldn't that tend to prevent anything man made from getting near the sun, much less its "surface" / chromosphere?
RS
From your own link: Though the corona's temperature is high it's molecules are so far apart that the gases release little heat. If a person were to stand on the sun's corona they wouldn't burn, they would freeze in the near vacuum of the corona.
Yes the surface is only around 5800K, hot enough to melt any known material. But the corona surrounding the surface is over 10^6K. I'm curious how they intend to handle such intense energy. Not just heat energy, but insane amounts of radiation across the spectrum. This will be quite interesting from an engineering standpoint.
The particles have a high temperature (are moving quickly) but the particle density is low. Therefore the heat will be small. Heat is the flow of energy from a hotter body to a cooler body.
Since the corona isn't dense enough for the heat to be a problem, all they have to worry about is the radiation. Since that's all coming from the same direction, they can just hide behind something (the thing labeled "thermal shield" in the picture).
Can we vote that you join the crew too for having that stupid signature. (Note: No I didn't click it)
Seriously, though, it's not quite that simple. "The area around the sun" is very hot, but it's not very dense. IANAThermalEngineer, but I imagine they have one or two at NASA, and I'm guessing that they can come up with some kind of effective radiative cooling system. (Though perhaps they'll just rely on a Thermal Protective System (aka "heat shield"), like they did for the original Solar Probe.)
What about radiant heat?
If you can't see the value in jet powered ants you should turn in your nerd card. - Dunbal (464142)
But they're not entering the corona. From TFA:
I'm not saying 1400 degrees isn't hot, but it's not unmanagable.This should not be modded informative. Please. A nuclear reactor (I assume you mean fission not fusion since that is the usual meaning of reactor) core does not get hot enough to melt the fuel - if it did, you must mean Chernobyl so you should have been more specific. The surface of the Sun is at a much higher temperature than the melting point of any material.
...the future crusty old bastards are already drinking the Kool-Aid.
"This calls for a very special blend of psychology and extreme violence" - Vyvyan "The Young Ones"
The recent science fiction movie Sunshine described taking a special spacecraft close to the Sun. The premise of the movie and final resolution were bogus to me. However the issues of near solar travel and the special effects were interesting.
And it radiates via what medium?
Infrared photons would be my guess, just like most radiant heat.
When our name is on the back of your car, we're behind you all the way!
Though the corona's temperature is high it's molecules are so far apart that the gases release little heat. If a person were to stand on the sun's corona they wouldn't burn, they would freeze in the near vacuum of the corona.
Oh, they'd burn alright - but it would be a really bad tan. The side facing the Sun would absorb insane amounts of radiation; the side facing away would freeze... A good example (though far away from the corona): the extreme surface temperatures of Mercury, depending on the amount of sunlight, range from around 100 K to over 700 K.
Awesome, it's Earth's first Class 4 probe.
sudo eat my shorts
Also from TFA:
"To solve these mysteries, Solar Probe+ will actually enter the corona," says Guhathakurta. "That's where the action is."
If its stupid but it works, its not stupid.
Saying that the shade of Venus is very cold, paints a rather mis-leading picture. It's not the same thing as staying in, say, really cold air. As you say, only radiation transfers heat in space, so _all_ the cooling effect you're going to get is whatever the craft radiates. That's not very much. It also depends of the fourth square of temperature, as per Steffan-Boltzman, it's a lot harder to lose the last (or next to last) 10% than it is to lose the first 10%.
But more importantly, you start gaining it right back, as soon as you're no longer behind Venus. It'll take years to go from Venus's orbit to where they want to get, simply because it's that hard to go down into a gravity well. You need to lose a heck of a lot of energy, but being that it's in space and you don't have friction as a cheap brake, it means as much firing the rockets as if you wanted to gain the same energy. So it'll have a heck of a lot of time to warm up right back.
And again, see Steffan-Boltzman. The farther you got from equilibrium by sitting in the shade, the bigger the difference will be between incoming energy and energy you radiate, hence the faster you warm right up. If you managed to get, say, 100K lower than equilibrium in the sunlight, the first 25K of that gain will be lost a lot faster than the last 25K.
In short, past a point, every Kelvin you go lower by sitting in the shade, will take longer to get it, and the faster you'll lose it when you get out of the shade.
A polar bear is a cartesian bear after a coordinate transform.
Um, no. You know how if you drop a thimble of 200 degree water into a 5 gallon bucket of 70 degree water, it fails to raise the temperature to even 71 degrees, despite the much higher temperature it had? High temperature doesn't heat things much if there isn't a lot of material that has it.
If you were to walk into a room full of solar corona gas, you wouldn't be incinerated. You wouldn't even be heated. The instant evaporation of the water on your skin would cool you several orders of magnitude more than the million degree gas would heat you. Overall, your temperature would drop. And then you'd die of being exposed to a near vacuum. But the point is, the instant effect would not be the room's gas vaporizing you, it'd be you cooling the room's gas to approximately body temperature, just as the water in the thimble is almost instantly cooled to the temperature of the water in the bucket.
"Convictions are more dangerous enemies of truth than lies."