In reply to Michel Jullian's message of Sat, 6 Jan 2007 17:24:05 +0100: Hi, [snip] >Thanks for confirming Stephen, your maths look ok to me; > >What you call "waste" heat can be turned into useful backwards radiation with >a proper reflector can't it? I even wonder if a thermonuclear engine producing >just heat could not be turned into an efficient photon drive. P.S. It seems it >could, according to http://en.wikipedia.org/wiki/Nuclear_photonic_rocket
While true that a photonic rocket is most efficient if all the fuel mass is converted to photons, it may not be true if that isn't possible. IOW all our current fuel sources only convert a tiny fraction of the mass into energy. This is even true of nuclear reactions. (Not true however of anti-matter reactions). So if we are stuck with a fuel that is largely going to end up as dead weight, then perhaps we are better off ejecting it out the exhaust, rather than hanging on to it, and trying to accelerate it further. Ejecting it has the further advantage that we get a much larger thrust for the same energy expenditure. Sorry, I don't feel like breaking my brain trying to do the math on this one. ;) [snip] Regards, Robin van Spaandonk http://users.bigpond.net.au/rvanspaa/ Competition provides the motivation, Cooperation provides the means.
