Are you an undergrad student in any mechanical engineering? or other engineering fields?
Do you have knowledge in mechantronics, solid mechanics, machine design and manufacturing?
As mentioned in the replies above, i think all the fields you mention have certain applications in aerospace industry...
You certainly need mechatronics to control everything in a space-craft.
Knowledge in solid mechanics may be used in designing the machanical parts of the machine..
Machine design...i guess you will need to have some knowledge about different mechanisms, design guidlines of different machine components say gears, bearings etc to design anything mechnical?
Manufacturing...well, when you design something, you have to consider whether it can be manufctured?
It sounds to me all these fields are useful in aerospace industry and as a matter of fact, I guess the industry requires experts in all these fields and of course a lot more than these fields, say heat transfer. (You need to have thermal control)