Optimal solid-rocket assisted space shuttle ascent trajectories are investigated. Solid-rocket thrust profiles are simulated by using third-degree spline functions, with the values of the thrust ordinates defined as parameters. The trajectories are optimized parametrically-with use of the Davidon-Fletcher-Powell, penalty function method-by minimizing propellant weight subject to state and control inequality constraints and terminal boundary conditions. This study shows that optimizing a control variable parametrically by using third-degreespline-function interpolation allows the control to be shaped so that inequality constraints are strictly adhered to and all corners are eliminated. The absence of corners makes this method attractive from the viewpoint of solidrocket grain design limitations.
Nomenclaturea a = axial acceleration dji = spline function coefficients bi = coefficients for cubic polynomial during tailoff C n = aerodynamic normal force coefficient D = drag force e =e } +e 2 + ... +e f e { = error functions gj = /th point equality constraint go = gravitational constant hi = /th point inequality constraint Ap = specific impulse kj = weight constants or penalty constants for point equality constraints gj = weight constants or penalty constants for point inequality constraints m = mass n g = number of point equality constraints n h = number of point inequality constraints Q = dynamic pressure Sj = state and control inequality constraints= angle of attack p = atmospheric density Subscripts i = /th value max = maximum min = minimum spin = spline curve fit of stage = evaluated at staging steer = evaluated at time when optimal steering begins tail = during tailoff Superscripts (') =d/dt