Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/3/84; site teddy.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!talcott!panda!teddy!rdp From: rdp@teddy.UUCP Newsgroups: net.space Subject: Re: Nuclear Rockets Message-ID: <939@teddy.UUCP> Date: Mon, 15-Jul-85 17:15:51 EDT Article-I.D.: teddy.939 Posted: Mon Jul 15 17:15:51 1985 Date-Received: Sat, 20-Jul-85 07:50:13 EDT References: <1839@mordor.UUCP> Reply-To: rdp@teddy.UUCP (Richard D. Pierce) Organization: GenRad, Inc., Concord, Mass. Lines: 27 In article <1839@mordor.UUCP> @S1-A.ARPA,@MIT-MC:jheimann@bbnccy writes: >From: John H. Heimann > > > Back in the 'sixties, there were a number of programs (funded, I think, >by NASA and what was then AEC) to develop nuclear powered space propulsion >schemes. The ones I recall are project Orion, which involved the detonation of > > My question is, why were these projects cancelled? I can imagine that >project Orion would violate the Limited Nuclear Test Ban Treaty, which >prohibits atmospheric or outer-space testing of nuclear weapons. The main >reason I can think of for cancelling the hydrogen/reactor engine is concern >about radioactive exhaust or, if the rocket should crash, radioactive waste. >Neither of these concerns would be legitimate if the engine were used well >outside the earth's atmosphere. There is of course the problem of getting a >fission reactor safely into orbit. A few tons of plutionium oxide, molten from >reentry, would not be the nicest thing to have falling into one's backyard. > The use of nuclear propulsion tended (in the case of the non-explosive technique) to result in extremely high exhaust velocities and very high efficiencies, but extremely low thrusts. I recall hearing of thrusts in the neighborhood of ounces! Such propulsion methods are useful when you can tolerate long durations of firings (months or years) and do not need tremendous accelerations. For near-earth and earth-moon manned missions, and the like, what was needed was lots of thrust over short periods of time, the kinf of things chemical rockets are good at.