The Development of Autonomous Dynamic Trajectory Optimization Control of Launch Vehicles

This paper first introduces the technical requirements for autonomous flight, with a brief review of the International Academy of Astronautics(IAA) study group, "autonomous dynamic trajectory optimization control of launch vehicle". Two research scenarios, ascent rescue and powered descent, are compared from the viewpoint of optimal control. On this basis, the technologies on the autonomous trajectory planning and control under the thrust-drop failures in the ascending phase, and the autonomous guidance method during the powered landing for the recovery of the rockets are discussed respectively. For the ascending problem, the characteristics of different solutions, including the iterative guidance method(IGM)-based residual carrying capacity evaluation, the state-triggered indices(STI), the joint planning with the payload’s performance, and the multiple graded optimization(MGO), are analyzed for comparison. For the landing problem, the challenges such as the feasible region reduction caused by high thrust weight ratio(HTWR) and the disturbance adaptability brought by the limited feasible region, are studied in detail, as well as the onboard planning demonstration flight in China are introduced. Finally, the foundations supporting the above methods are summarized, which play an important role in promoting the flight autonomy.

Autonomous mission reconstruction during the ascending flight of launch vehicles under typical propulsion system failures

In recent years, Chinese Long March(LM) launchers have experienced several launch failures, most of which occurred in their propulsion systems, and this paper studies Autonomous Mission Reconstruction(AMRC) technology to alleviate losses due to these failures. The status of the techniques related to AMRC, including trajectory and mission planning, guidance methods,and fault tolerant technologies, are reviewed, and their features are compared, which reflect the challenges faced by AMRC technology. After a brief introduction about the failure modes of engines that can occur during flight, and the fundamentals of trajectory planning and joint optimization of the target orbit and flight path, an AMRC algorithm is proposed for geostationary transfer orbit launch missions. The algorithm evaluates the residual performance onboard, and plans new objectives and corresponding flight path by iterative guidance mode or segmented state triggered optimization methods in real-time. Three failure scenarios that have occurred during previous LM missions are simulated to check the robustness of the algorithm: imminent explosion risk of the boosters’ engines, thrust drop during the first stage of flight, and being unable to start the engine during the second stage. The payloads would fall from space according to the current design under these conditions, but they were saved with the AMRC algorithm in the simulations, which allowed the rocket to get into the target orbit as intended or the payloads were deployed in other orbits without crashing. Although spaceflight can be very unforgiving, the AMRC algorithm has the potential to avoid the total loss of a launch mission when faced with these kinds of typical failures.