Greetings,

For civil services, unless you plan on opting for your own under graduation subject as optional, it does not matter what you discipline you graduate from.

if you go the conventional way of opting for arts and humanities subjects as option (anthropology, sociology, history, polity, etc.) you will have to prepare for it separately from scratch. Some people choose subjects during their under graduation that are also available for UPSC (like all core branches of Engineering, Mechanical, Civil, etc.)

As for your dilemma, I'd suggest you go for Aerospace if you are really interested in it and will opt for a different subject for UPSC as it is a great field that can serve as a strong backup option for employment or research.

I am attaching a link to all UPSC optional subjects for you to see and decide better:

https://competition.careers360.com/articles/upsc-ias-syllabus

good luck

hello,

If you want to persue civil services then the only crieteria you have to follow you must have a bachlor degree whether you do 4 years course (engineering) or do B.Sc, BA any 3 years course. If you have any of the bachlor degree you are eligible to give UPSC exam. Upsc have syllabus of history, civics, geography, current affairs, means all the subjects. If you want to persue your aerospace engineering you can do definately but if you want to save your 1 year you can do any 3 years course in order to get bachlor degree. Its upto you.

hope this will help you

all the best!!