Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!hplabs!sri-unix!REM@MIT-MC From: REM%MIT-MC@sri-unix.UUCP Newsgroups: net.space Subject: Intersecting orbits Message-ID: <508@sri-arpa.UUCP> Date: Sun, 1-Apr-84 07:48:00 EST Article-I.D.: sri-arpa.508 Posted: Sun Apr 1 07:48:00 1984 Date-Received: Thu, 5-Apr-84 00:55:36 EST Lines: 31 From: Robert Elton Maas Date: Saturday, 31 March 1984 10:10:03 EST From: David.Smith@cmu-cs-ius.arpa [Satellite orbits go nearly every which way, even though most go generally in the easy direction of west-to-east.] This, by the way, makes me skeptical about the claim that the space station would be useful as a base for satellite repair. It takes more than a station, you also need a tug to bring the satellite out of its former orbit into rendezvous orbit with the station (and to put it back in proper orbit when done, although that can be done by a permanently-mounted second-stage rocket rather than with a true tug), an astronaut with backpack to despin the satellite, and a grappling arm to latch onto the satellite so it won't move away or rotate every time a tool applies force to it during repair. We've already demonstrated the backpack and Canada-arm, so now we need the station and tug. Note that it takes a lot less energy to tug an orbiting object around than to re-orbit it from ground, even if it's in a grossly different orbit, mostly because tugging can be done with a highly efficient ion rocket or solar sail whereas lifting from ground requires a high-impulse rocket or shuttle, which with present technology requires highly inefficient chemical rockets which require all their energy stored at liftoff rather than taken in from the Sun during maneuvering. Thus a space station is useful but only as one of the four main parts of the system, and until the tug is developed it really won't be directly useful for this task except where the orbit of the satellite so nearly matches the orbit of the station that the STS might be used as an interim tug. But I suspect by the time the station is up there we'll be close to having a tug too.