On Sun, 25 Aug 2002, The Silent Observer wrote:
> To give an extreme example, the NERVA nuclear engine, essentially a
> submarine reactor cooled with hydrogen, was to have an ISP of something
> like 3000 seconds...
Uh, no, somebody's got their numbers mixed up -- the Isp spec for the
second-generation NERVA design (75klb thrust) was 825s, and about the best
number considered in the program was 850s. To get 3000s you need a
gas-core engine (a fissioning plasma), which is a rather bigger technical
challenge.
However, his point remains: Isp and thrust/weight ratio are independent
performance numbers. For a really good rocket engine, you need to do well
on both.
Henry Spencer
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