I am interested in learning science and doing research in missile technology but i don't know which course i must select.

You must inform your present level of study.It means that you want a Defence job,which you will get by studying Physical Sciences/Polytechnic/Engineering and following the recruitment procedure at the appropriate time.

You must be do b.tech in aerospace technology plz go to https://science.shiksha.com/aerospace-aeronautical-engineering-colleges-in-delhi-ncr-categorypage-2-56-320-0-0-10223-1-2-0-none-1-0#page-top