Abstract: To design the fuel optimal ascent trajectory of space planes under complex and multiconstrained conditions, a strategy is proposed to segment the ascent trajectory according to the thrust characteristics of the engines. When the original optimal control problem is transformed into a multistage optimal control problem, the Gauss pseudospectral method is used for parallel optimization. Numerical result shows that this strategy can easily satisfy the constraints of state variables when the engine switches and generates the fuel optimal trajectory within short computing time. It is verified that the optimization strategy proposed is efficient.

Key words: space planes, fuel optimal, multiplestage optimization, Gauss pseudospectral method