There are four categories of thrusters: Rockets, Jets, water propellers and propellers
They are the most efficient and heavy-weight lifting things in the game, however, they cost the most fuel per second. Rockets are extremely powerful, being deemed extremely useful for any kind of creation.
Are like propellers, but stronger and cost more fuel per second
They are strong enough to lift a few blocks, and cost the least amount of fuel per second.
They are just propellers, but they work only in water. *ship propeller*
There is a small chance for a propeller or rocket to emit a sound that sounds like:
I personally think it is an easter egg the creator put in, for it seems intentional.