Parker Solar Probe, Take the Solar Plunge Options

[ljk4-1]

Any serious plans to send a probe into the Sun to explore its depths as far as possible?

What would help a probe last as long as it could and how deep could it get?

Could it even radio or laser out any data?

What about a Sun skimmer?

[nprev]

I don't know, but my best guess would be <poof!!!> before any such probe even got close to the photosphere, so I doubt that any useful data could be gathered even if it could somehow be transmitted through all that RF noise... (need shades just to think about it!!!)

[JRehling]

Solar Probe was supposed to come within 3 solar radii.

I suppose an elaborately shaded craft could get pretty close. A "ball" with instruments could be surrounded with a hemispherical shade with near 100% reflectance held by struts rather far from the craft. Perhaps even a hierarchical tier of such shades could perform even better.

Entering the photosphere would instantly annihilate any craft. The velocity of the craft as it hit the outer layers of gas, which would increase rapidly in pressure with depth, would be colossal -- even aside from the radiative heat.

[Guest_Richard Trigaux_*]

Solar Probe was supposed to come within 3 solar radii.

I suppose an elaborately shaded craft could get pretty close. A "ball" with instruments could be surrounded with a hemispherical shade with near 100% reflectance held by struts rather far from the craft. Perhaps even a hierarchical tier of such shades could perform even better.

Entering the photosphere would instantly annihilate any craft. The velocity of the craft as it hit the outer layers of gas, which would increase rapidly in pressure with depth, would be colossal -- even aside from the radiative heat.

Yes, if we imagine a shield, the shape of a ... shield, which shadow comes up on the probe itself, in such a way that it just eclips the Sun and, seen from the probe, appears like a disk just a bit larger than the Sun (like the Moon just eclips the Sun seen from Earth) then this shield gets very hot, indeed, but, seen from the probe, it appears as a circle just a bit larger than the Sun but not so hot. The reason is that it absorbs Sun heat from one side, but it radiates its own heat on both sides. So it can provide an efficient shadowing. And a tiered structure of such shields can really efficiently cut down the heat received by the probe itself in one or two orders of magnitude.
So we can get much closer from the Sun than with any other design. The limitation is the first shield (the shield size quickly increases with the number of tiers) which must be made of very high fusion point material and be polished so what it reflects as much heat as possible without aborbing it. The only solution I see would be a very thin veil of tungsteen, polished in front and blackened with graphite at the rear. The second, third etc. tiers would be conical in shape, to increase side radiation.

Such a design would allow to get very close from the Sun, much closer than Mercury, and, if we give the shield a slightly parabolic shape, it can also be used as a high gain antenna, and contribute to overcome the very poor signal/noise ratio.

Getting closer? The capture speed near the Sun is more than 600km/s, and this figure alone is detering: even if a probe manages to cope with the radiated heat, as soon as it will enter the corona it will drag and burn. Remember: the coldest place on the Sun is 4000°C (in spots) where tungsteen and graphite cannot bear much more than 3000°C. So, unless there is some very new and unexpected discovery in physics, we are bound to contemplate the Sun from afar.

The laser to cool the probe? Whatever its technology, a laser produces waste heat. And, unless we find a way to get around the second principe of thermodynamics, we cannot use it to cool anything. The only way to cool a probe would be to bring a lot of water, and make it boil to regrigerate the probe for a short time, before it gets too hot. Even one hour gained at 600km/s would allow to gain two Sun radii. But, very close from the Sun, the heat is enough to boil a full swimming pool of water in some seconds...