Jet engines, like those powering airliners, burn a lot of fuel, right? Think again. . . .

In the attached paper, I reveal how a jet engine can also be made to work without combustion of any kind. The trick is that you must carry some heavy fluid on board, so the thrust actually comes from the "kinetic energy" accumulated in that fluid.

So, it's not going to provide free propulsion, but it may come in handy if you're ever shot at with a heat-seeking missile, since the exhaust of this engine is perfectly cool.