Tuesday, December 1, 2009

Jet Packs

When I was a kid, I loved watching those old Warner Bros. cartoons; the days when violence was not yet strictly monitored on television as it is today. And characters like Bugs Bunny, Daffy Duck, Elmer Fudd, Sylvester the Cat, and Tweetie Bird made animated shows popular. One of my favorite cartoons was Road Runner, where the coyote was always trying any new ACME product or other crazy idea to thwart the ever escaping road runner. A contraption that even I thought couldn’t be built was his jet pack. And while in this episode it worked (the coyote smashing into a cliff wall though), I later learned that this fictitious device had some real history to it.

Also known as rocket packs, jet packs attain liftoff from fast escaping liquid or gases that propel the pilot skywards. The first rocket pack was designed by (who would have guessed) the Nazi regime during World War II. Its user wore two shortened Schmidt-Argus jet pulse engines that were used to power Fieseler Fi 103 (V-1) flying bombs. The machine was called a Himmelsturmer (“Skystormer” in English). To take off, the flier ignited both engines simultaneously whose propulsions were channeled into a single, angled rear tube that provided lift and forward thrust. There was also a smaller tube mounted on the user’s chest that maintained a lower, constant upward thrust.


V-1 flying bomb

Sustained flights weren’t possible so only short jumps of up to 60 meters (180 feet) at an altitude of 15 meters (50 feet) were attempted. The device was intended to assist German engineer units across minefields, barbed wire, and wide waterways. As soon as the throttle was disengaged, the jet pack shut off. Surprisingly, there are no recorded casualties at the hand of this machine.

In the 1960’s the United States army began to hire companies to design a similar apparatus to be used by soldiers in combat. Most, if not all of these designs, used different types of compressed gases (i.e. hydrogen peroxide, nitrogen) to obtain lift.

Another application that came from this work was using similarly working device in space. One such design was the Bell Pogo, a small rocket powered platform that two people could ride on. In the 1980s, NASA demonstrated its Manned Maneuvering Unit (MMU) which later was replaced by the SAFER to be used in case of an accidental separation from the spacecraft or station.



Bell Pogos



While it may have been fun to ride, engineers realized that rocket packs would be able to traverse longer distances in they had some form of a wing. One of my favorite examples of such a device is Yves Rossy’s jet pack. His pack was built with rigid carbon-fiber wings spanning about 8 feet (2.4 meters) holding four small kerosene-burning jet engines underneath. After being lifted to a proper altitude by plane, he ignites the engines just before exiting the plane with the wings folded. The wings unfold while in free-fall, and he is then able to fly horizontally for several minutes, landing using a parachute. Rossy controls his flight by adjusting his body position and uses a hand throttle to maneuver. He and his sponsors spent over $190,000 to build the device.



A water-propelled jet pack, the Jetlev-Flyer, debuted in 2009 as a product that could be purchased by the public. Instead of gas, it uses two water jets for thrust. A small unmanned boat with a pump delivers pressurized water to the jet pack via a hose. This amazing idea has a MSRP of $129,000.



If you’re already thinking about building your own jetpack, I implore you to reconsider. Not only are your chances of success minimal, but there would be no truly safe way to test it. However, you’re likely to see someone else perform aerobatics on one if you go to a popular air show. Companies like Jetpack International and Martin Jetpack often perform stunts at large venues or can be hired to be at your own event.


Martin jetpack

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