Advanced Guidance and Control for Hypersonics and Space Access
Advanced guidance and control (AGC application to hypersonic air-breathers is planned. We list the test cases used to demonstrate that the desired results are achieved, briefly describe an automated test scoring method, and display results of the tests. Some of the technology components have reached the maturity level where they are ready for application to a new vehicle concept, while others are not far along in development.
New Nonlinear Control Technique for Ascent Phase of Reusable Launch Vehicles
Current flight control of reusable launch vehicles is based on table look-up gains for specific flight conditions. A new suboptimal nonlinear control technique for the complete ascent phase of reusable launch vehicles is presented. The new technique, called the θ-D method, is synthesized by adding perturbations to a typical optimal control formulation with a quadratic cost function. The controller expressions are obtained by getting an approximate closed-form solution to the Hamilton-Jacobi-Bellman equation. The θ-D method avoids iterative online solutions. A controller using this new method has been designed for the ascent phase of a reusable launch vehicle and implemented in a six-degrees-of-freedom high-fidelity simulator being run at the NASA Marshall Space Flight Center. Simulation results show that the 0-D controller achieves accurate tracking for the ascent phase of the reusable launch vehicle while being robust to external disturbances and plant uncertainties.
DESIGN AND EVALUATION OF A 3-D OPTIMAL ASCENT GUIDANCE ALGORITHM
This paper considers the problem of optimal threedimensional guidance of a launch vehicle through the atmosphere while satisfying a set of operational constraints, and satisfying a set of tangency conditions at main engine cut-off. A hybrid analytic/numerical approach is applied to the solution of this problem. The resulting guidance algorithm makes maximum utilization of the analytically tractable portions of the solution to construct a set of interpolating functions. These functions are then used in a numerical treatment of the total problem based on the method of collocation. A numerical study is performed using a single stage vehicle model. The results indicate that the guidance algorithm converges reliably and accurately, and that the execution time required for a single guidance update is well within the realm of real time implementation. Nomenclature