Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.BERKELEY.EDU Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!ittatc!dcdwest!sdcsvax!ucbvax!space From: ST401385@BROWNVM.BITNET Newsgroups: net.space Subject: Re: next generation shuttle: electrically assisted take-off? (Reply to Dani Eder's comments) Message-ID: <8602182033.AA12344@s1-b.arpa> Date: Tue, 18-Feb-86 14:16:57 EST Article-I.D.: s1-b.8602182033.AA12344 Posted: Tue Feb 18 14:16:57 1986 Date-Received: Fri, 21-Feb-86 04:19:39 EST Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: ST401385%BROWNVM.BITNET@WISCVM.ARPA Organization: The ARPA Internet Lines: 39 >... one can build towers that literally extend out of the atmosphere. >...T300/934 Graphite/Epoxy composite, used in airplanes, has a >density of 0.057lb/in^3 and a compressive strength of 215800 lb/in^2. >...the height of a column of graphite/epoxy that just barely can >support its own weight is 59.7 miles. If we taper the tower, we can >make it taller. You also want to work at less than theoretical >strength, but the order of magnitude is correct. Now a 60 mile tall tower: *that's* SF. It would have to be either very tapered, or else wire braced (like a radio tower) to avoid buckling. And if it is to support, say, 10 tons, it's gonna take a *lot* of graphite. But it's a neat idea. (still, why not build it on top of a mountain? On the equator? If you don't like Kenya, how 'bout Cotopaxi, in Equador (6 Km) or Huascaron, in Peru (7 Km), or even Mauna Loa, in Hawaii (not on the equator but at least near it, 4 km)?) Where did you get the compression strength of graphite, by the way? Is this the strength to failure by plastic deformation? Does it include the epoxy matrix? The electrically-assisted shuttle launch was an idea for a lead-in to true mass drivers. Most of the mass driver ideas I saw four or five years ago (I haven't kept up) required huge amounts of power in one or two seconds, to sustain hundreds of g's to get into orbit. This stretches out the power need to almost a minute, and lowers the g's to something that could launch almost any payload, including people. Gene O'Neill spent a year at MIT looking at mass drivers, and delivered a lecture talking about a "telephone pole launcher" to deliver packages about the size and shape of a telephone pole to orbit from Pike's peak. (or, at least almost to orbit: it obviously needs an apogee kick to make an orbit not intersecting the surface). I assume he published somewhere, but I don't know where. This would make a good device for getting kevlar into orbit if you want to make some sort of skyhook. --Geoffrey A. Landis Brown University.