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From: (Dani Eder)
Subject: Re: small is not beautiful (was Re: SSTO "agnostics", please read)
Date: Oct 16 1995

>>It most closely correlates with number of parts, not dry mass.
>>I've seen curve fit approximations which were along the lines of
>>(#parts)^(1.1-1.25) * (mass)^(0.5-0.85)

A relation that can be found to hold from concrete dams (cheap
structure) to satellites (expensive structure) is that cost
per pound for structure goes as the 3/2 power of stress level
(in psi).  The more highly stressed the part, the more time
and effort is spent analyzing and testing the part.


Concrete Dam	400 psi		$0.015/lb
Steel Building	7,200 psi 	$0.5/lb
Airplane Wing	40,000 psi	$30/lb 
Satellite Structure	200,000 psi	$1000/lb

Dani Eder

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