From: firstname.lastname@example.org (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