David.Smith@CMU-CS-IUS@sri-unix.UUCP (08/05/83)
There is another type of electric rocket (besides ion) which has been used for attitude stabilization. It involves a block of teflon and an electrical spark. The spark vaporizes a bit of teflon, which then goes flying out the nozzle. AW&ST carried an article on it -- what, several moons ago? In actual use on a spacecraft, the things were fired several times a second over some years. Very low thrust, but not much is needed for this application. Incidentally, the latest AW&ST (that I have seen) has a picture of the meteroid hit on Challenger's windshield which forced the glass to be replaced.
karn@eagle.UUCP (Phil Karn) (08/07/83)
Speaking of electric rockets, AMSAT has come up with a similar rocket that could be used on a future payload launched from a GAS can on the shuttle. The problem here is that you want an engine to boost the payload into a longer lived orbit than 300 km, but to prove to the NASA people at the same time that it is intrinsically safe to fly on a manned vehicle. The proposal is to fly a steam rocket. Liquid water is directly preheated with solar energy and fed to a thrust chamber where an electrically powered heater turns it to steam. Specific impulse is terrible (~140 sec) but mass isn't a limitation; only a couple tens of kilograms of water would be required for the job. Of course it would be much easier and quicker to just carry two solid rocket motors to perform a two-impulse Hohmann transfer to the higher circular orbit, but just getting permission from NASA to deploy something from the GAS can will be a major accomplishment. Phil