Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!henry From: henry@utzoo.UUCP (Henry Spencer) Newsgroups: net.space Subject: Re: Orbital Artillery Message-ID: <3577@utzoo.UUCP> Date: Sat, 25-Feb-84 21:01:59 EST Article-I.D.: utzoo.3577 Posted: Sat Feb 25 21:01:59 1984 Date-Received: Sat, 25-Feb-84 21:01:59 EST References: <16648@sri-arpa.UUCP>, <3562@utzoo.UUCP> Organization: U of Toronto Zoology Lines: 28 Kieran asks: Has anyone else on the net, upon hearing O'Neill's idea for using mass-drivers throwing away tiny pellets of reaction mass ( say little buckets of lunar dirt) as a high-efficiency rocket-engine, had the thought, "Good Lord, who wants to fill the solar system up with billions more meteorites, especially around what will eventually be a crowded shipping region, the earth-moon region? Won'rt the probability of hulling your ship increase dramatically?" Actually, O'Neill thought of this. The first part of the answer is that there is so much natural debris around that it's hard for human activities to increase it much. The second part is that there are fairly easy ways to handle the problem, which should probably be used to prevent a problem developing in the long term. Specifically... The mass-driver's big virtue is that it can use most anything as reaction mass. So you can choose something that will be relatively inoffensive. Early on, the choice of propellant will be constrained by what's available, such as aluminum dust from ground-up shuttle external tanks. The problem can be minimized by spraying a static charge onto the dust as it leaves the mass-driver; this will make the dust particles disperse. Later, the propellant of choice is liquid oxygen extracted from lunar/asteroidal rock. The LOX simply boils off into vacuum after release, leaving no debris at all. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry