Hello Spandan,

Initially during your btech tenure both subjects/branches has a lot of difference.As for mechanical you will learn about machine and its functioning while they will prepare to be specialized in aerodynamics.But when you will take aerospace for mtech than it will be aa great advantage for you being a mechanical student.It will help you to grab the topics easily and some might be related to.But initially it sill differ,but yes being a mechanical student will help you in future if you do masters in aerospace.

Hope it will help