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How about using the intense heat on the surface of the spacecraft from friction to heat a gas up to provide additional thrust?
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It actually doesn't get all that hot, and if it does it isn't hot for very long.
Remember two things, that first heat only travels from hot to cold, so the skin coolant would need to get hotter than the exhaust gas to contribute to its heating.
And, if you ran the thing open cycle and let the coolant escape through a nozzle to produce thrust, remember that every gram you throw out is a gram less rocket fuel you could be carrying. Simply, because the skin doesn't get that hot or at least not for very long, you get more performance from carrying another gram of fuel than you do blowing skin coolant out the back.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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Use the air as the fuel?
What about re-entry? Would we be able to reclaim energy from the friction, maybe using it plus air to produce a retro rocket?
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Then the engine nozzle would be flying backwards into its exhaust plume and it won't work.
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Use the air as the fuel?
What about re-entry? Would we be able to reclaim energy from the friction, maybe using it plus air to produce a retro rocket?
Ciclops is right, the pressures generated by reentry are too high to counter with a practical low-energy retro rocket.
Edit: I'd like to add that a rocket is a relatively simple contraption as far as the physics of its performance goes, and we have already squeezed most of the efficiency out of them as we can. What is really the limiting factor is the limited amount of energy in the fuel and/or what the rocket is made of.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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Thanks for the input.
Just throwing ideas around, eventually one should work.
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about the re-entry thing, as I understand it, the air is ionized, so would a superconducting ring (the solution to all of our problems, it sometimes seems) expell the ions away and produce valuable thrust?
-Josh
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That would require energy to keep it superconducting.
Ionosphere braking sounds useful though I haven't done any maths for it. Repeling off the Ionosphere might work.
It's plasma that surrounds a craft on reentry. Maybe forcing it tomake a vacuum bubble around the craft?
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about the re-entry thing, as I understand it, the air is ionized, so would a superconducting ring (the solution to all of our problems, it sometimes seems) expell the ions away and produce valuable thrust?
The sheer velocity of the vehicle on reentry, which is what makes the air hot enough to become a plasma, is so great that you aren't going to reverse it with a magnet of practical power. Keeping the supercon magnet cold would be very difficult as well.
Although repelling the plasma is a little interesting, wouldn't it require an equal amount of energy as the kinetic energy of the vehicle wouldn't it? Which would, of course, be huge. I may have to ponder the physics of this a bit.
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The basic physics requires the conversion of the spacecraft's kinetic and potential energy into another form, preferably outside the vehicle. Compressing a local magnetic field would create enormous mechanical stresses on the field generator which would need a heavy structure to hold it together. The energy would therefore be transferred into the structure of the vehicle rather than ablating a heat shield and heating the air, not a good trade.
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In other words, instead of heating the air as the vehicle passes through the atmosphere, that energy would instead go into crushing the vehicle? I don't know about that, aren't the pressures against the heat shield transmitted to the vehicle?
In any case, it would take an absurdly powerful magnet, and it would only stop the fraction of gas thats converted to plasma. The uncharged gas would go right though the magnetic field, still necessitating some kind of thermal heat shielding and severely complicating the cooling for the magnet. A neat idea, but not really practical, spend the money on making better ceramic or alloy plates or something.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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In other words, instead of heating the air as the vehicle passes through the atmosphere, that energy would instead go into crushing the vehicle? I don't know about that, aren't the pressures against the heat shield transmitted to the vehicle?
In any case, it would take an absurdly powerful magnet, and it would only stop the fraction of gas thats converted to plasma. The uncharged gas would go right though the magnetic field, still necessitating some kind of thermal heat shielding and severely complicating the cooling for the magnet. A neat idea, but not really practical, spend the money on making better ceramic or alloy plates or something.
Yes. On second thoughts magnetic braking with a plasma is nonsense lol ... the charged particles would just spiral along the field lines and not be repelled. To repel them would require an electrostatic field, the braking force being proportional to the mass of the particles.
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