what exactly do you think its going to make up? "The Hybrid Synergy Drive runs on apples and fairy dust"? I doubt that OP wants to build one of the engines, they just want a concise explanation.
I've seen gpt hallucinate all kinds of things. But very rarely for something like explaining a process or system.
It writes things that sound reasonable in context. So it will likely give something that sounds like a Popular Mechanics article about how some kind of machine works, but it may not really be this particular machine that you are asking about, or any actual machine in existence. That's the tricky thing about it, if it actually said "fairy dust" you know you can stop reading, but what it actually writes typically needs some actual understanding of the subject to refute.
I've seen gpt hallucinate all kinds of things. But very rarely for something like explaining a process or system.