From: Michelle Jones (spike66@ibm.net)
Date: Tue Aug 11 1998 - 22:29:51 MDT
Michelle Jones wrote:
> Mike Linksvayer wrote:
>
> >Supposedly the Roton will cut launch weight by spinning the engine,
> >pumping the fuel into the engine chambers and avoiding heavy pumps...
>
> yes i saw that but i was not sure if they were serious... {8^D
after doing some calculations, i ask you to ignore my previous posts on
the subject of roton. i repent! i was a nattering nabob of negativity!
{8-[
now i will explain how i went wrong. first, i was going by an earlier
concept of roton, that given in the final frontier magazine. that article
presented the concept strictly as a single stage to orbit/reentry body,
which one
need not assume. a roton concept can be used as a first stage, second
stage, or a throwaway non-reentry system. after i convinced myself that
the rotors would be heavier than the cryopumps they would replace, i
tossed the whole thing aside. (single stage to orbit has verrry little
margin
for unnecessary weight).
secondly, i failed to realize that the roton system not only obviates the
cryopumps, it also eliminates the need for thrust vector control. i never
did see this stated anywhere, but a roton would be inherently stable due
to the gyroscopic rotor. much weight is saved by using fixed nozzles.
thirdly, and this is the most embarrassing, i failed to even consider the
cost. cryopumps are inherently expensive and tweaky. and dangerous.
for being a classical thinking rocket scientist, who considers *only
performance*
ignoring cost and complication, well, i guess i am the poster child. {8-]
even if the roton gives up some performance to conventional designs, it is
waaay
simpler and cheaper than the alternative. i guess this is why amateur
groups never
deal with liquid rockets: cryopumps and thrust vector control cannot
really be done at a reasonable cost. but a roton could be imagined which
has very few moving parts, and none with the kind of difficult
manufacturing
tolerances associated with high capacity cryogen pumps.
now, after all that apology, i would suggest those who would sell the
roton
concept should emphasize its real strengths. it is sold as a possible
reentry
body: i still have serious doubts about that. however, if a launcher is
simple
and cheap enough, why worry about getting it back? sell it as a means of
lifting raw materials to orbit very cheaply, in the form of rotons.
perhaps a
manufacturing facility could be set up in orbit, and the raw materials
could
be obtained by taking rotons apart, that were launched into orbit just for
that purpose. spike
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