Author Topic: Magnetohydrodynamic (MHD) aerobraking and thermal protection  (Read 5382 times)

Offline neilh

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A couple months ago I was reading about magnetohydrodynamic (MHD) aerobraking and thermal protection concepts over at Jon Goff's blog:

http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-i-introduction/
http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-ii-atmospheric-reentry-for-rlvs/
http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-iii-aerobraking-and-aerocapture/

While it's obviously at quite a low TRL, the concepts seem potentially promising. Any thoughts on how useful MHD tech might be for aerobraking and reusable thermal protection?

I also was intrigued by the idea in the comments that suborbital spaceflights could be a good place to test this tech.
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Offline JasonAW3

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A couple months ago I was reading about magnetohydrodynamic (MHD) aerobraking and thermal protection concepts over at Jon Goff's blog:

http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-i-introduction/
http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-ii-atmospheric-reentry-for-rlvs/
http://selenianboondocks.com/2010/02/mhd-aerobraking-and-thermal-protection-part-iii-aerobraking-and-aerocapture/

While it's obviously at quite a low TRL, the concepts seem potentially promising. Any thoughts on how useful MHD tech might be for aerobraking and reusable thermal protection?

I also was intrigued by the idea in the comments that suborbital spaceflights could be a good place to test this tech.

     And to think I verbally pitched this same exact concept to some of the people at NASA Langley's space Exploration group in '89.  Should have tried to patent it back then...  Oh well.
     The problem as I saw it was keeping the superconducting magnets cold enough to be able to push away the plasma shock wave and use it as the actual heat shield.  By its' nature, there would be some erosion and heating of the aeroshell before the bow wave would reach plasma temperatures that the magnetic field could interact with.  That heating could pose a problem with cooling the magnets off enough for superconduction.  For instance, where would you dump the excess heat? Steam venting cooling?
     A great idea that may require the creation of a plasma under the craft before actually interacting with the atmosphere.

     Not saying it CAN'T be done, but there are technical issues that need to be resolved first.

jason
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Offline Jim

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It is more likely not viable.  The energy put into the system could be use instead to slow the vehicle eliminating the need for thermal protection.

Offline jimgagnon

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You may be interested in this 1968 Boeing proposal on Transpiration cooling for reentry -- Jon referenced it in another blog entry. It describes a phase one study of an alternative to ablative heat shields. From what I understand, there were no follow up studies.

If I recall correctly, Jon felt that a ceramic heat shield with some sort of transpiration cooling that also enhanced plasma shield effects might be interesting heat shield mechanism for a smaller spaceplane than the Shuttle.

Offline RanulfC

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jimgagnon:
There actually HAVE been somewhat "follow-up-studies" just not many by NASA or in the United States per-se.

The military continued studying the concept but the majority of the work is still classified data, and there has been "renewed" interest in the concept in Europe, Russia and Asia over the last 10 years or so. Googling "Transpiration Cooling" gets some of the information and reports that are available though I myself haven't done a search in a couple of years. Thanks for the report though it's one I didn't have :)

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Offline JasonAW3

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It is more likely not viable.  The energy put into the system could be use instead to slow the vehicle eliminating the need for thermal protection.

   Just had a thought though;  Could this system, using the plasma flowing past the edge of the reentry shield, tap the power of the reentry itself as an MHD generator?  I figure the cathodes and anodes could be electrically isolated from the hull of the craft and spaced around the circumfrumce of the heat shield, (assuming either an Orion or Dragon style reentry craft) and might be able to generate enough excess power to assist whatever fuel cells and/or high powered batteries being used,  in generating enough of a magnetic field, long enough, to be able to pull this off.

     Mind you, I know it would be very tricky generating power with the very media that you are trying to push away from the surface of the TPS shield, but I think such a balancing act just might be possible.

I still see alot of technical issues that would need to be worked out, but I think it just might be possible.

     (And before someone starts harping on 'perpetual motion machines, what would be done here is tapping the conversion of kenitic energy to heat energy for extra power, that would otherwise be lost as waste heat.  Plus, the field would be initially established using the power availabe from onboard the spacecraft itself).


Jason
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Offline mmeijeri

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You may be interested in this 1968 Boeing proposal on Transpiration cooling for reentry -- Jon referenced it in another blog entry. It describes a phase one study of an alternative to ablative heat shields. From what I understand, there were no follow up studies.

Transpiration cooling sounds very interesting and there are quite a few papers about it. In a sense it is ablative too, but in a way that is easily "refurbished", simply by filling up the water tanks again. This could even be done in orbit, which might be interesting for Mars since it might be more efficient than propulsive capture/descent without needing a heavy and expendable monolithic heat shield.
Pro-tip: you don't have to be a jerk if someone doesn't agree with your theories

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