A Nonlinear Programming Model for Launch Vehicle Design and Costing

A nonlinear programming model is developed that has as the objective function (to be minimized) total cost of the development, manufacture, and launching of a launch vehicle. Constraints on physical interrelations, basic performance relations, and desired achievements are given as functions of the variables. The variables are physical properties of the launch vehicle such as airframe weight, total inert weight, mass fraction, thrust, propellant weight, length, and other similar properties. The model is for the purpose of assisting in launch vehicle design by generating designs that have minimum cost for selected performance characteristics. Previous work has mostly been in estimating or predicting costs of given designs. This model goes one step further in that it uses cost-estimating relations (CERs) to influence the design. The nonlinear programming models are not convex. The basic model has 25 variables, 34 inequality constraints, and 9 equality constraints. Nonnegativity restrictions hold on all the variables. The nonlinear programming problems have been solved using the sequential unconstrained minimization technique (SUMT).