Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Fri, 2 Feb 90 01:26:47 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 2 Feb 90 01:26:25 -0500 (EST) Subject: SPACE Digest V10 #465 SPACE Digest Volume 10 : Issue 465 Today's Topics: Spacecraft drives and fuel efficiency ---------------------------------------------------------------------- Date: 2 Feb 90 05:52:59 GMT From: mentor.cc.purdue.edu!f3w@purdue.edu (Mark Gellis) Subject: Spacecraft drives and fuel efficiency Hi, I have a question I figured you people might be able to answer. I write sf as a hobby (hopefully for money someday), and I have a foolish desire to get as much of the science right as I can. I understand the Daedelus-type spacecraft designed some years ago by the British Interplanetary Society can reach a velocity of about 15% c with a fuel-payload ratio of 50-to-1. As I understand it, the engines had an Isp of about 1,000,000. A friend of mine pointed out that the Daedelus design is a highly inefficient fusion engine. It is, he claims, based on the bomb-version of fusion propulsion. He suggested that you could get a much higher Isp by using fusion power to superheat reaction mass--hydrogen, probably-- and then spew it out at very high velocity. Actually, if you can get controlled fusion at all (meaning you can control magnetic fields and deal with multi-million degree temperatures) it sounds like it would be more efficient this way. I know that, in theory, you cannot get an Isp better than 30,000,000 (because it means you have an exhaust velocity of the speed of light), and I am curious as to how much you could get, assuming a technology that has to use our rules regarding physical principles, but has solved all or most of the technical problems. I would be grateful if anyone would be willing to comment on this subject (c'mon, you engineer types, earn your keep!). In particular, I am looking for what people think is the best fuel efficiency (Isp/EJV/etc.) that you could get from a fusion drive of this kind (the kind that heats up reaction mass with fusion power and then lets it rocket out). Thanks in advance. Mark ------------------------------ End of SPACE Digest V10 #465 *******************