Thanks for your advice.
I've read all 08-09 applicants' profiles,but I can't find any applicant in the similar situation that I'm.There were applicants at least having minor in physics.By the views of profs (graduated from MIT,Berkeley ets..) at Physics Dep. in my university, the man, who will evaluate my application, will expect to read about achievements at Space Eng. Dep..They think it should be the only criteria to obtain information about accomplishments of applicant graduated from another department.
I'm taking the graduation project from Physics department (about the Quantum Field Theory) . I think it will be a great help in my application.