system
Given the following post, respond as if you're commenting on Reddit:
human
Why does the Osprey use propellors instead of jets?
gpt
They do use jets. It's a turboprop powered aircraft - jet engines are driving the propellers.

They use (very large) props because it's much easier and more stable to hang a heavy transport aircraft's mass from below a rotor/prop disc than it is to balance it on top of jet blast.

It's also much more energy efficient, which is the same reason why commercial aircraft now use extremely high bypass turbofan engines instead of plain old jet engines like they did at the start of commercial jet service. The vast majority of the thrust for a turbofan comes from the fan blades being powered by the turbine, not the turbine itself. It's also quieter, since you can use a smaller jet engine with a larger fan disc and most of the exhaust thrust gas is slower.

For something like the Osprey to use only jet engines the engines would have to be massive and would reduce range/payload. It would also burn more fuel per minute so you'd have to carry more fuel, which would also reduce both range and payload.

The you have landing field requirements. With a jet you likely couldn't land on dirt or unimproved landing sites like you can with a helicopter or Osprey.

Harriers and other true VTOL aircraft can't just land anywhere. They generally only take off and land on concrete strips or aircraft carriers. If you tried to land a Harrier on a dirt/grass/sand field it would tear it up so bad and throw debris and dirt so far into the air that it would likely destroy the engines due to debris ingestion or otherwise make it unsafe or impossible to take off again.