Reply To: extracting energy out off the plasma soup

[Earl of Plasma]

FF of course is already a rocket. An old forum post claimed exhaust velocity of around 3% lightspeed, giving us a very efficient rocket.

Without adding extra reaction mass, though, I’d think thrust would be quite low. Maybe too low to be optimal for a fast Mars trip, I don’t know.

So how fast could FF get us to Mars, if we used the plasma jet directly? And if that would be slow, how much could we improve matters with extra reaction mass?

I can’t give you a straight answer but I can give you clues. One device of the size shown by LPP focus fusion is not enough, so you would need several or a much bigger machine. Maybe It’s possible to built several units in the same shell?

The trust depends of how much and how fast you let the gases out of the nozzle. The connection between speed and velocity is according to square root of the temperature. You can get much more thrust if with more mass and lower temperature. First you can use the surrounding air compress it, heat it with the alfa particles from fusion and let it out. Higher up there are no air, so then you can use gas you brought with you, to heat and let out. You can not bring unlimited amount of gases, but surely enough to get out of earth gravitation. Other could as you know.

Finely the alfa particles are the only to give thrust. There energy is about 3/2*KB*T and equals to m*v*v/2.
KB*T should equal 7Mev according to physics table of binding energy and m = 4*1,6*10 exp(-27). This gives v=58 milj m/s
But that’s very theoretical so lets say efficiency is 50 % gives v=40milj m/s.

The rocket can never reach that speed and it’s probably relatively heavy and the mass flow tiny. But it will get close the velocity out of the nozzle, even if it takes times, since there are almost no resistance in space.