Using __repr__ or __str__ for own printable class?

Andrew Dalke adalke at mindspring.com
Tue Apr 15 06:15:34 CEST 2003


Erik Max Francis
> There are even in some circumstances more fuel-minimizing transfers than
> Hohmann, like bielliptic transfers (which is sort of like a
> double-Hohmann transfer to a point way out in space), but they take vast
> amounts of time (e.g., a Hohmann-like transfer out to Neptune and then
> back simply to go from Earth to Mars).  Under some circumstances this
> can take less fuel than a simple Hohmann transfer (although it won't be
> energy minimizing).

I hadn't heard of a bielliptic transfer before, but then again, nearly
everything I know about this topic comes from reading Heinlein.  ;)
(Okay, and reading magazines like Nature and various articles
about space flight.)

Still, a gravitational assist can get things out faster and with less fuel
than either of those two.  But they are non-trivial to compute, and
Heinlein sure hadn't heard of them, given especially the constraint
of having to work it all out on paper and sliderule.

'Course, once Kilgore figures out his energy transformation equations[1]
and we work out the (*ahem*) "astrogation and control difficulties"[2],
we'll just get there at 1g the whole way.  <wink>

                    Andrew

[1]  Heinlein's "Farmer in the Sky" used a matter-energy conversion
power plant to boost at 1g for 4 hours, then coasted for two months.
The older atomic powered ships took "two years and nine months"
using, I assume, a Hohmann orbit.  "Your grandchildren will make
the trip in a week, blasting at one g all the way"

[2] After all, in "Have Spacesuit, Will Travel," a slipstick is
still "the best thing since girls."






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