Q) "What type/kind of (a) compressor is used in a rocket engine?"
A) "The compressor used in a rocket engine is called the rocket-engine compressor and it is not that type/kind of (a) compressor that is commonly used in other fields of engineering........"
All that I'm confused of is whether or not to use an indefinite article before "compressor" in the above two structures.
And would it be grammatical, if I pluralized the above interrogative structure as below?
Q) "What types/kinds of compressors are used in rocket engines?"