No idea as this is the first time I even heard of this. But a gas turbine (a jet engine, basically) is efficient, kerosene is very energetic, and for a hoverbo

No idea as this is the first time I even heard of this. But a gas turbine (a jet engine, basically) is efficient, kerosene is very energetic, and for a hoverboard I imagine the hot & compressed exhaust itself is what’s mechanically useful. There’s no reason to have a line other than as a tether, though that comes with its own risks.