In that case, Randall is right, but not for the reasons he thinks he is.
I don't think engineering is an area you can be right or wrong in. Life's too complex. Randall's point of view seems sound on this.
A subsonic ramjet is a almost as big a fuel hog as a rocket.
I can't parse that. I need numbers cos I'm an engineer. What does 'almost as big a fuel hog' mean?
I'd be interested if anyone has any hard numbers like ISP on subsonic ramjets.
I did a web search and found a good link:
http://www.onera.fr/conferences/ramjet-scramjet-pde/#ramjet
which compares the different propulsion systems, but doesn't describe ramjet's behaviour as low as mach 0.8. The graph seems to imply that they don't work below mach 2, but I know that's flat-out wrong. I've also been playing with a ramjet simulator from NASA that suggests that ISPs as high as 2000 seconds may be theoretically achieveable at mach 0.8 (interestingly you have to wind down the combustion temperature, so you use less fuel and so of course ISP goes up).
In theory running a ramjet on metal powder rather than Kero doubles the ISP since the energy density of aluminum/LOX is twice that of kerosene/LOX- a ramjet is just a fancy way to heat up air. The link above says that some Ruskies have actually built a fluidised metal engine that way, which is presumably even more efficient since it uses ambient oxygen; but some of the throw away comments imply it's a bit fiddly in actual operation.
I don't know, there's enough variables there that it's probably doable, it still doesn't sound totally stupid; in fact if you're reasonably optimistic, it may well beat conventional turbojets at slightly subsonic speeds.
The real difficulties are, as always with reusable designs, how much bigger the overall vehicle turns out to be; and whether that's really worth it.
Anyway, I'm bored with this whole discussion- I am not replying anymore no matter how much Pierce implies I'm a dipstick for even thinking about such low tech stuff :-)
-p
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