fusion rockets...

George:

>Steve Higginbotham commented that my numbers for
>Fuel Usage on a fusion rocket were sensible for
>what we can forsee now, but not for what we can
>do in 3000 years.  This is not strictly true.
>
>There's only so much energy available when you
>take four hydrogen atoms and make helium.
>That energy is the top-end, 100% best that you'll
>ever get out of a fusion rocket.  The corrected
>numbers for TL9 fusion rockets I gave are running
>a significant fraction (50ish percent, if I remember
>my source material right) of that maximum limit.
>Engineering only lets you get closer to that limit,
>not to pass it....

Last time I looked, energy available from fusion of four
hydrogen atoms to one helium is on the order of 0.7%
conversion, which gives a theoretical Isp of 3,660,000
or so.  Which is a WHOLE LOT more than twice what you
allowed, George...


>[note that the potential Isp of an antimatter rocket
>is a whole lot more fun to work with 8-) ]

It sure is! :)

Later...

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I have learned to use the word "impossible" with the greatest caution.
                                    --W. von Braun