Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 11/03/84 (WLS Mods); site escher.UUCP Path: utzoo!watmath!clyde!burl!ulysses!bellcore!petrus!scherzo!allegra!princeton!astrovax!escher!doug From: doug@escher.UUCP (Douglas J Freyburger) Newsgroups: net.space Subject: Re: Mt Shasta on Uranian moon!! Message-ID: <71@escher.UUCP> Date: Mon, 27-Jan-86 19:52:14 EST Article-I.D.: escher.71 Posted: Mon Jan 27 19:52:14 1986 Date-Received: Tue, 28-Jan-86 06:32:48 EST References: <8601261231.AA04077@s1-b.arpa> Organization: NASA/JPL, Pasadena, CA Lines: 43 > When are we gonna get that damn ion rocket developed so we can send > Mariner/Viking/Galileo-class spacecraft (orbiter/lander) to all the outer > planets without having to wait ten years to get the craft to the very outer > ones via gravity-assist from the nearer ones? My preferred answer would be right-now/yesterday, but... There are some communications satelites that use ion rockets to keep station, and various ion drives have been flown for years. It would seem that the answer really IS yesterday. The major problem with running ion driven spacecraft to the outer planets is their strong magnetic fields. Ion drives have severe problems in strong enough magnetic fields. They work by accelerating charged particles in a straight line to VERY high speeds and out the nozzle. In a magnetic field, the particles follow an arc (f=B-cross-v/c) and foul up the 'combustion chamber'. The other problem is restarting the drives. They tend to foul up when they are shut down, so you only get one sure shot per engine. SO: We just have to send up a probe that 1) has enough regular rocket fuel to maneuver when it gets into the magnetic field, 2) only uses the ions to get there fast and still slow up when it gets close, and 3) can get out of Earth orbit on regular rockets (I'm not sure enough about field strengths to know if this is a problem). This is a tough list to make, and we lose multiple planet missions, but we DO get there the fastest with the mostest. Is it time to push for this for the next wave of planetary exploration? Mariner Mark II doesn't have any ion rockets, and I don't know if the isotopic generators make enough energy. Could be we are restricted to Mars-and-closer until we are willing to fly "real nuclear reactors". -- Doug Freyburger DOUG@JPL-VLSI, JPL Mail Stop 23 escher!doug, escher!teleop!doug Pasadena, CA 91109 etc.