Newsgroups: sci.space Path: utzoo!henry From: henry@utzoo.uucp (Henry Spencer) Subject: Re: Space applications of cold fusion Message-ID: <1989Apr4.164030.1053@utzoo.uucp> Organization: U of Toronto Zoology References: Date: Tue, 4 Apr 89 16:40:30 GMT In article SCOTT@GACVAX1.BITNET (Scott Hess) writes: >... One device I've read about in Jerry Pournelle's >"High Justice" used lasers. It seems that a powerful ground-based laser >is fired into a cavity at the bottom of the spacecraft. It is pulsed on >and off, at a high speed. The cavity is vented in such a way that it draws >in air. The laser heats the air very quickly, so the air pushes out the >bottom, propelling the craft. Then more air is brought in ... Basically >a ramjet with half the engine ground-based... >My basic question is this: Does this work? ... In principle it ought to, although arranging for the laser to heat the centimeters of air in the cavity but *not* the kilometers of air in the rest of the beam path is a bit tricky. The US has a small research program on laser launchers, although they're currently focusing on rockets rather than air-breathing systems. It is hoped that SDI will develop the necessary lasers and optics. It looks both feasible and promising. In particular, with short-pulse lasers, it scales down well. Launching capsules weighing tons takes formidable power sources and lasers, but if you're willing to settle for something smaller, the system (and its budget) gets much more manageable. -- Welcome to Mars! Your | Henry Spencer at U of Toronto Zoology passport and visa, comrade? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu