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by sandworm101 3343 days ago
Jetpacks are officially dead. The advantages of not lifting your own o2, of burning fuel using air, means that systems based on rockets are now done.
1 comments

Then perhaps your first sentence should have read, "Rocket packs are officially dead".

I think that the terms have historically been used interchangeably, but the distinction should be made. It's awfully nice not to need to carry oxidiser for your propellant.

A rocket is something with only an exhaust. A jet also has an intake. And it goes a little further than just not lifting the 02. Any unburnt gas (air) becomes a 'working fluid' that can be pushed. A rocket moves by throwing gas away at speed. Jets also grab gas from the air and accelerate it along with exhaust products. That's why a jet or turbofan can have a high specific impulse with such a low exhaust velocity, higher (>8k) than even an ion thruster in vacuum.