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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
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Organization: Los Alamos National Laboratory
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> 
> 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.