  The performance optimization for a combined ascent-entry mission subject to
constraints on heating rate and heating load is studied. The ascent vehicle is
modeled as a three-stage rocket that places the vehicle onto a suborbital
exo-atmopheric trajectory after which the vehicle undergoes an unpowered entry
and descent to a vertically downward terminal condition. The entry vehicle is
modeled as a high lift-to-drag ratio vehicle that is capable of withstanding
high levels of thermal and structural loads. A performance index is designed to
improve control margin while attenuating phugoid oscillations during
atmospheric entry. Furthermore, a mission corresponding to a prototype launch
and target point is used in this study. The trajectory optimization problem is
formulated as a multiple-phase optimal control problem, and the optimal control
problem is solved using an adaptive Gaussian quadrature collocation method. A
key aspect of the optimized trajectories is that, for particular ranges of
maximum allowable heating rate and heating load during entry, relatively small
adjustments made during ascent can potentially decrease the control effort
required during atmospheric entry. Outside of these ranges for maximum
allowable heating rate and heating load, however, it is found that the required
control effort increases and eventually saturates the commanded angle of attack
upon initial descent. The key features of the optimized trajectories and
controls are identified, and the approach developed in this paper provides a
systematic method for end-to-end ascent-entry trajectory optimization.
