The modern definition of a hybrid vehicle is any single machine with multiple sources of power. Usually, this means one internal combustion engine and one electric motor with batteries. This is again the case with the Biohazard Jet Bike, though its internal combustion engine happens to be a propane-fed turbine engine which spins at up to 112,000 revolutions per minute and produces forty-five pounds of thrust. The electric motor is powered by twenty-four volts of juice and is said to be good for eighteen miles per hour for up to twenty miles.

The bike also has pedals, though they are non-functional. From the looks of things, much of the cycle comes from the pedal-powered world, with a front fork and wheels cribbed from the bike world for sure. Still, this machine looks like lots of fun, and jet engines have been known to run on nearly any combustible fuel, including our personal favorite: biodiesel.

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• Inventive minds attach a jet engine to a Honda Ruckus

[Source: eBay Motors]

We're fans of the Honda Ruckus here at AutoblogGreen, as its 50cc four stroke engine combines excellent fuel economy and fairly low emissions. With its cool urban-destroyer styling, knobby tires and ample storage space, the Ruckus makes both a cool vehicle on which to chart out unknown territory and an excellent little runabout. There are plenty of ways to lower the fuel efficiency of the little engine, but few of them make as loud a statement as adding a jet turbine to the back shelf. Sound crazy? Absolutely, but that didn't stop at least one enterprising person from accomplishing the feat.

We've got a couple of videos pasted after the break for you to watch, so hit the jump for more. Notice the row of bikes at Starbucks in the first video... if there weren't a jet turbine on that Ruckus, it would look a little out of place, no?

There's a crazy underground community which focuses on the pulse jet, which history buffs may remember as the powerplant of the German Buzzbombs of World War II. As you could probably guess, the buzz name comes from the sound that the engine makes. As you can see in the video seen here, the buzzing bomb jet engine attached to a retro-style bicycle frame is capable of moving along quite nicely. We're not so sure that your neighbors would love you as you fired up your jet-powered bicycle for the morning commute, but with a seventy-five mile per hour top speed, at least you'll get to the office quickly. The builder of this contraption, Robert Maddox, sells engines ranging from just fourteen pounds of thrust all the way to one-thousand pounds of thrust. The one attached to the bicycle seen here is worth between fifty and sixty pounds. Seriously, there's no end to the fun you could have with your very own jet engine...

[Source: Youtube, eBay via The Kneeslider]