[ExI] portability of spreadsheet models, was RE: ai class at stanford
spike66 at att.net
Wed Aug 24 02:15:06 UTC 2011
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Adrian Tymes
>>...You are attempting to invoke code reuse, of something that was never
designed to be reusable...
>...It has been reused many times, but in a limited sense. I have used it
to estimate ascent trajectories of rockets going up through the atmosphere.
Agreed it couldn't be used for predicting hurricane paths... spike
Furthermore, there is a good reason for all this biz. When you get into the
specific class of payloads in which the payload is dense, very small
envelope, high number of individual payloads and expendable, where the
design driver is minimization of cost per payload, then solid rocket
boosters have some compelling advantages. They have a much lower specific
thrust than the liquids, which means the payload mass fraction is often way
less than 1%. So if you can really sharpen the old pencil and engineer a kg
out of a radome or nose tip, you can get nearly an extra kg of payload.
But wait, there's more.
With solids, there is a huge savings in launch infrastructure costs, but it
often forces four stages, which drives the need for at least two aft placed
aerodynamic surfaces. This is a killer in solids because solids already
have a big problem with the CG being too far aft. So you often need to
ballast the nose, and ooooh that hurts, so if you can sharpen the pencil
enough to engineer a kg out of an aft aero surface, you can remove some
ballast forward and get more than a kg extra payload. Now you can see why
we go to extraordinary efforts to know with great precision the air density
at every point in the launch profile: to get some weight out of the second
and third stage fins.
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