RSE #33
Performance Mathematics
Rocket Science for Earthlings # 33, PERFORMANCE MATHEMATICS
Every rocket engineer alive today has been trained to produce rockets with
maximum performance as the best way to get minimum cost. All rocket design
equations are based on maximum performance. In my research I often find really
excellent examples of maximum performance mathematics. Kraft Ehicke in
"Spaceflight Dynamics" gives an excellent method of determining the liftoff
acceleration of a booster to give maximum burnout velocity, but does not address
costs. A.N. Hosny in "Propulsion Systems" proves that all stages in a rocket
should have the same mass ratio to achieve maximum performance, but also does
not address cost as a factor. Constant thrust from a stage can be shown to produce the best performance over constant acceleration. Calculations involving costs are kind of messy and
are not favored by rocket scientists. It involves something called parametric
analysis which is a fancy name for plugging in a whole bunch of numbers and
hunting around for the best answer. This method is often used in business cost
calculations, but seldom used in scientific calculations. Rocket scientists don't
like it. Is it any wonder that our current launch vehicles cost so much.