Hello Aravind,

Welcome to CareerGuide.com.

From, your query and discussion ,all I can make out that you want to make a transition as per your interest and stick to it for the rest of your career.

Well, interest is one of the aspects that contributes to a successful career. Others include the right aptitude, skills set , personality traits etc. Please evaluate your self among these lines before you decide a transition. Do you feel you have an acute eye for details, loads of imagination and patience? A lots of creativity and personal and technical innovation ? A sort of perfectionist? And a lot more.....
Also I would recommend you take the psychometric assessment services provided by careerguide.com , to know your inherent potential and traits, after which you can make an informed career decision.

After that our experts will discuss the report with you and help you decide according ly.

Now, regarding Design, you need in depth knowledge and mastery of CAD computer aided designing software. This will give you the basic knowledge about design, plus there are other structural design softwares that are different for each domain, such as 3D modeling, Solidage tools etc. ... That is per the corporate choice. This will help you to start with R&D design .

Further, in Aerospace engineering, you will be responsible for designing the structure of what ever craft it is! You can enter into this after you complete Masters degree.
There are very good colleges in India that provide courses in aerospace engineering. Please go through the following links to find further information:

http://www.aero.iisc.ernet.in

http://www.embibe.com/100marks/top-10-aerospace-engineering-colleges-in-india/

Hope this helps!

Still have queries? Feel free to revert/discuss

All the best...