Re: a total Roton reversal, with apologies

Michelle Jones (
Tue, 11 Aug 1998 21:29:51 -0700

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