Question: Why do rocket nozzles open wider at the end than, let's say, get narrower?
Let me explain:
I recently learned from random internet sources, that a jet engine works by having this amazing thing called a combustion chamber. The combustion chamber ignites the air to expand it, thus, causing more thrust. And to generate more thrust, jet engines usually have a narrow ending (i.e hole getting smaller) so more thrust is compacted down into that single bit of space.
But for rockets, the nozzle gets larger and larger. Such as below.
Theoretically speaking, wouldn't it be better, and more efficient to have the nozzle end get slightly narrower similar to a jet engine, to gain more thrust? I'm assuming people have already thought of this idea, because it seems like such a basic concept. Yet, I can't find/think of an answer why...
