Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!henry
From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.space,net.columbia
Subject: Re: orbit-60 cents/pound
Message-ID: <4689@utzoo.UUCP>
Date: Tue, 27-Nov-84 12:57:04 EST
Article-I.D.: utzoo.4689
Posted: Tue Nov 27 12:57:04 1984
Date-Received: Tue, 27-Nov-84 12:57:04 EST
References: <1078@inuxc.UUCP>, <16504@lanl.ARPA>
Organization: U of Toronto Zoology
Lines: 34

> There were two estimates of the acceleration necessary for an EM launcher
> to work: 92 g and 1000 g.  I'm not going to argue which is right since
> I can't think of subjecting any object to those forces except raw materials.
> To manufacture something which could take that kind of acceleration would
> either cost too much or add weight to the object just to strenghthen it.
> Sending only raw materials into space would solve this problem (manufacture
> what you need in space).  I still don't know what kind of vehicle (to put
> the raw materials into) could withstand the forces.  Seems like the vehicle
> itself would account for the lions share of the launch weight.

Not at all.  This sort of acceleration may sound formidable, and there are
a good many things which could not travel via such a launcher, but it's not
as bad as you suggest.  Back ten or fifteen years ago, there was a small
research project called HARP (High Altitude Research Project), a joint
US-Canada effort.  It was doing upper-atmosphere studies, using a most
unusual method to get its instrument packages to high altitudes:  firing
them out of cannons!  I believe HARP reached an altitude of 75 miles with
one package, fired out of a 16-inch gun with a tremendously long barrel
(two WW2 battleship guns end-to-end, I think).  The packages had to be,
uh, sturdily built, but there were no insuperable difficulties involved.
The accelerations involved were tens of thousands of Gs.

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.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry