Research Of Trajectory Technologies For Reusable Launch Vehicle's Ascent Flight And Abort Return Flight

For a Reusable Launch Vehicle (RLV), the maximum altitude is about30kilometers and the maximum Mach number is about3for the ascent flight which aims to certify the key technologies of Terminal Area Energy Management (TAEM). If the RLV can ascend as planned, it will flight powerlessly return to Auto-landing Interface (ALI) after attending to the maximum altitude and then undergoing TAEM. If the RLV powers off because of malfunction of its engine during its ascent, it have to renturn urgently to ALI after urgent ascent and urgent return flight phase. The designing technologies of trajectories for ascent and urgent return flight have been researched in this dissertation with a background of the TAEM flight test.The normal ascent trajectory of a RLV is called the trajectory of nominal ascent flight phase. Designing of the trajectory of this phase is a Two Point Boundary Problem with multi-index and multi-restriction. The main indexes in this paper include the maximum altitude and the maximum Mach number. Its physical restrictions comprise dynamic pressure restriction and over loading restriction. During ascent flight of a RLV, the time length of its engine is limited. Meanwhile, the index variables altitude and Mach number are the symbol of potential energy and kinetic energy respectively. Therefore, the maximum altitude and the maximum Mach number limit each other. Hence, when designing the trajectory of nominal ascent flight, balance must be made between the different indexes and the restrictions must be obeyed. In this dissertation, the designing strategy is to plan the flight path profile first and to propagate the trajectory to get its profile parameters and all the other profiles of the reference trajectory.The urgent ascent flight phase originates from the power-off point and ends when the flight path angle becomes zero. In this phase, the remnant poisonous fuel must be discharged totally. The object of designing of the trajectory for this phase is to maximize the end energy of the RLV without disobeying the physical restrictions. The main factors that can affect the energy loss are overcoming dynamic resistance and discharge of the fuel. The two factors couple each other. Flight path angle profile determines how much work overcoming dynamic resistance does. A flight path angle profile has been provided in the dissertation to uncouple the coupled effect. By analysis of mass point dynamics, the law that discharge timing affects velocity of the energy loss has been researched and a plan of discharge timing was selected. An onboard trajectory designing method was provided using the above-mentioned flight path angle profile plan and the plan of discharge timing.The urgent return flight phase originates from the end of the urgent ascent flight phase and ends at ALI, and TAEM is its special case. Energy Corridor is the core concept of TAEM trajectory designing.The coupling between longitudinal and lateral maneuvers is ignored. Thus, it is a two-dimensional (2D) trajectory designing method. For the other cases of urgent return flight, the2D trajectory designing method can also been used.The difference is that the propagation step is not altitude but range-to-go. A trajectory designing method with range-to-go steps is provided in the dissertation, and it was used in onboard trajectory designing for urgent return of the RLV.In urgent return flight phase, if the lateral maneuver can been used when needed, the three-dimensional (3D) trajectory designing method must be used. That is, the coupling between longitudinal and lateral maneuvers must be considered and the lateral reference trajectory is necessary. Based on the planned reference dynamic pressure profile and lateral reference trajectory, the3D reference trajectory can be propagated. Based on the snake-styled lateral trajectory, a multi-mode lateral trajectory planning method has been put forward. For different initial position errors, different mode of trajectories can be selected to erase the heading error and the position error relative to the ALI. In addition, a three-dimensional propagation algorithm has been brought forward to follow the reference dynamic pressure profile and the lateral reference trajectory in an optimization problem.The algorithm makes it available to propagate the3D trajectory fast.Last, by the Simulink module in MATLAB, a trajectory emulation environment has been built up. The designed reference trajectories have been emulated to test the veracity, physical flyability and stability of nominal ascent, urgent ascent and urgent return.