(Allen Thomson) writes:
He's concerned with very high Isp engines; Nerva-style nuclear thermal
rockets have Isps only modestly higher than chemical ones. (Note
that in the rocket equation, "modestly higher" can make a substantial
difference in system performance for some applications.)

I'm sure we could generate higher ISP with nuclear engines than
Nerva. Materials science has advanced just a bit since then.

Besides, what nuclear thermal engines lack in ISP, they make up for in
high thrust.

Even better would be a dual mode nuclear engine that could produce
high thrust exhaust or electricity. Use the electricity for cruise
mode where something like an ion or plasma engine is more efficient,
but use the high thrust nuclear engine for entering and leaving
the planned planetary orbit (to save time).

Jeff
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