Trajectory optimization of an advanced launch vehicle is addressed. The optimal control problem is converted into a parameter optimization problem. Then, simulated annealing based single and multiobjective optimization algorithms are used. The single objective optimization problem is formulated to minimize the total flight time, while the multiobjective formulation tries to maximize payload mass and orbit insertion velocity. The problem is also solved using our novel Multiple Cooling Multiobjective Simulated Annealing Algorithm. It is shown that the algorithm is capable of finding the Pareto front of such nonlinear, multimodal problems.