Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site lanl.ARPA Path: utzoo!watmath!clyde!bonnie!akgua!sdcsvax!sdcrdcf!hplabs!hao!seismo!cmcl2!lanl!jlg From: jlg@lanl.ARPA Newsgroups: net.space,net.columbia Subject: Re: orbit-60 cents/pound Message-ID: <17130@lanl.ARPA> Date: Fri, 30-Nov-84 21:36:05 EST Article-I.D.: lanl.17130 Posted: Fri Nov 30 21:36:05 1984 Date-Received: Tue, 4-Dec-84 05:41:37 EST References: <1078@inuxc.UUCP>, <16504@lanl.ARPA> <4689@utzoo.UUCP> Sender: newsreader@lanl.ARPA Organization: Los Alamos National Laboratory Lines: 34 Xref: sdcsvax net.space:2893 net.columbia:1206 > > If you want a more modern example, the Copperhead missile is fired from > a six-inch gun. It has non-trivial laser-homing electronics and optics > on board. My recollection of the articles I've seen on its design is > that care was necessary, but the result doesn't look overly outlandish. > > Remember that human beings, one of the more fragile payloads of interest, > have taken 50+ Gs briefly without serious injury. The accelerations ARE > probably too high for humans, but should not be a serious problem for > many types of cargo. The key word in the above message is 'briefly'. The longer an instrument, device or person is subjected to the high loading, the more likely that permanent damage will occur. Humans may indeed be able to survive very short encounters with ~50 Gs, but long (10-60 seconds) exposure to just 15 Gs usually results in long term disability or worse. Even well built equipment would break down fairly quickly under the proposed 100 to 1000 Gs of these E/M mass drivers. Remember, the proposals are for tens of seconds at 100 Gs or several seconds at 1000 Gs. The cannon launched equipment previously mentioned only had to withstand the accelerations for times on the order of microseconds or at most milliseconds. I once had a fairly high quality 'shock resistent' mechanical watch which was advertised to be able to take shocks of up to 100 Gs (which corresponded to dropping it on concrete from ceiling level). I'm sure it couldn't really have survived 100 Gs for any period exceeding a few milliseconds though. 100 Gs is zero to 60 mph in .028 sec, during which time the unfortunate race driver would travel two and a half feet (He's really plastered on the seat). 100 Gs accelerates an object to 200 mph in less than .1 second, during which time the object travels about 27 feet. Anyone who has ever seen the results of an aircraft hitting trees and stopping within 27 feet knows the type of damage this kind of acceleration (or deceleration) can cause. And the longer something is subjected to these forces, the worse it gets.