Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site mordor.UUCP Path: utzoo!utcs!lsuc!pesnta!amd!dual!mordor!space@mit-mc From: space@mit-mc Newsgroups: net.space Subject: Light Sails Message-ID: <595@mordor.UUCP> Date: Thu, 21-Feb-85 11:42:50 EST Article-I.D.: mordor.595 Posted: Thu Feb 21 11:42:50 1985 Date-Received: Fri, 22-Feb-85 14:26:47 EST Sender: daemon@mordor.UUCP Organization: S-1 Project, LLNL Lines: 21 From: John Heimann I sat down and tried to sketch out just how fast a solar sail could reasonably be expected to go, assuming a point source of illumination (the sun), the usual inverse square law for drop-off of photon intensity, a bit of handwaving about the mean photon momentum, and some reasonable figures for the density of the sail material. I realized then that I wasn't really sure how the thing was to operate after all. Are solar sails designed to get their momentum from elastic collisions with solar photons (reflecting sunlight), or do they get most of it from collisions with other particles that are constantly emitted from the sum (e.g. neutrons)? A typical neutron from a nuclear reaction packs a lot more momentum than a photon from the same reaction, so this is an important issue. Also, what's a good assumption as to the composition of the sail? Would a large expanse of metallized mylar be reasonable, or would this rip to shreds under meteor impact? Not having read anything about the subject in years, I really am not up on the latest ideas - although the old ideas were certainly interesting. Any technical info. would be appreciated. John ("Lux et Veritas")