1. Ph.D. Candidate, College of Astronautics, Northwestern Polytechnical Univ., Xi’an, Shaanxi 710072, P.R. China (corresponding author).
2. Professor, College of Astronautics, Northwestern Polytechnical Univ., Xi’an, Shaanxi 710072, P.R. China.
3. Lecturer, Shaanxi Aerospace Flight Vehicle Design Key Laboratory, Northwestern Polytechnical Univ., Xi’an, Shaanxi 710072, P.R. China.