Thursday, March 31, 2011

Williams International X-Jet and other Vertical Take Off and Landing (VTOL) systems

 A stunning array of technological innovations has been woven into the day-to-day fabric of early-21st-century life: clothing made from recycled plastic Coke bottles; phones that run on high-frequency microwave radiation; snack-food science capable of containing such unruly forms as s'mores and peanut butter and jelly within the confines of a toaster pastry. Yet for some of us, such marvels are slim compensation for the unrealized possibilities of another device, one promised throughout childhood and never delivered. Where are our jetpacks?

The iconography of the jetpack -- a rocket-powered backpack offering its user the power of solo flight -- stretches back to Buck Rogers comic strips of the late 1920's and recurs in Walt Disney's 1950's Tomorrowland, James Bond's gadget-filled films and the skyways of the city where the Jetsons make their home. By the early 1960's, the jetpack was such a familiar pop-culture image that it had become interchangeable with the very idea of the future -- to mention one was to invoke the other. Yet still we find ourselves, in the year 2000, traveling by conveyances of the last century rather than soaring happily above the treetops. What happened? Where are our jetpacks?

The WASP (Williams Aerial Systems Platform)

Williams X-Jet

The Williams X-Jet, created by Williams International, was a small, light-weight Vertical Take Off and Landing (VTOL) system powered by a modified Williams F107 turbofan aircraft engine. This vehicle was nicknamed "The Flying Pulpit". It was designed to be operated by and carry one person and controlled by leaning in the direction of desired travel and adjusting the power. It could move in any direction, accelerate rapidly, hover, and rotate on its axis, staying aloft for up to 45 minutes and traveling at speeds up to 60 miles per hour (100 km/h). It was evaluated by the U.S. Army in the 1980s, and was deemed inferior to the capabilities of helicopters and small unmanned aircraft.
Other VTOL systems developed by Williams International included a jet-powered flying belt developed in 1969, which was powered by a Williams WR19 turbofan, and the WASP (Williams Aerial Systems Platform) developed in the 1970s, which was powered by the more powerful WR19-9.

General characteristics
  • Crew: One pilot
  • Length: ft (m)
  • Wingspan: ft (m)
  • Height: 4 ft 0 in (1.22 m)
  • Footprint: 4 ft² (0.4 m²))
  • Wing area: ft² (m²)
  • Empty weight: 401 lb (182 kg)
  • Loaded weight: 550 lb (250 kg)
  • Max takeoff weight: lb (kg)
  • Powerplant: 1 × modified Williams F107 turbofan, 600 lbf (2.7 kN)
  • Maximum speed: 60 mph (96 km/h)
  • Range: endurance of 30-45 minutes ()
  • Service ceiling: 10,000 ft (3,049 m)
  • Thrust/weight: 1.11
Currently one is on display in the National Aviation Hall of Fame, located inside of the National Museum of the U.S. Air Force, Dayton, OH.

modified Williams F107 turbofan aircraft engine


Hiller VZ-1 Pawnee

The Hiller VZ-1 Pawnee (U.S. Army designation; earlier Army designation: HO-1) was a unique direct lift rotor aircraft, using contra-rotating ducted fans inside a platform that the single pilot stood upon for lift, and controlled by the pilot shifting his body weight around to tilt the platform. The platform was developed starting in 1953 under an Office of Naval Research contract to Hiller Aircraft Corporation, and flew successfully starting in 1955.

Hiller VZ-1

The original concept had been developed by Charles H. Zimmerman in the late 1940s. Further elaboration followed, both by Hiller and the De Lackner Company.
There were two main models, the ONR model the 1031-A-1, and a somewhat larger VZ-1 Pawnee model produced in 1956 for the U.S. Army. Three of each model were built as prototypes. Neither of the variants was put into production.
The smaller models used two 44 horsepower Nelson H-59 piston engines. The larger models used three of the aforementioned engine and had an extended duct area. The largest variant had ineffective "kinesthetic control" and instead had the operator seated on a platform controlling the flight with conventional helicopter controlsDue to aerodynamic effects in the duct within which the propellers rotated, the platform was dynamically stable, even though the pilot and center of gravity of the platform were fairly high up. In testing, the prototypes flew well enough, but the U.S. Army judged them to be impractical as combat vehicles as they were small, limited in speed and only barely flew out of the ground cushion effect.
Two of the six prototypes are known to survive today — one ONR smaller model at the Hiller Aviation Museum in San Carlos, California, and one VZ-1 Pawnee model at the National Air and Space Museum in Washington, D.C. The latter craft was formerly on loan to the Pima Air Museum
General characteristics
  • Crew: one
  • Length: 8 ft 4 in (diameter) (2.5 m)
  • Wingspan: ()
  • Height: 7 ft (2.1 m)
  • Empty weight: 370 lb (167.8 kg)
  • Powerplant: 6× 2 x Nelson H-56 piston engines, 40 hp (30 kW) each
  • Maximum speed: 16 mph (26 km/h)
  • Service ceiling: 32.8 ft (10 m)
  • standard combat weapons for a U.S. soldier

The United States Army called them small rocket lift devices and began financing their development in the 1950's, intending to use them for amphibious troop landings, reconnaissance missions and passage over hazardous terrain. Early versions were ballyhooed, including Thiokol's Jump Belt and Aerojet-General's Aeropak, but the first major success was achieved in 1961, at Bell Aerosystems in Buffalo. The Rocket Belt, designed by engineer Wendell F. Moore, was a kind of hard-frame backpack powered by two hydrogen-peroxide fuel tanks (with long exhaust pipes trailing off on either side of the wearer) and controlled with motorcycle-like handgrips. Flying in a standing position, with knees slightly bent, users could achieve speeds of up to 60 miles an hour. One test pilot described the experience as "having a giant pick you up by the arms." But it wasn't very practical for wartime use: the pack was heavy; in flight it made a loud screeching noise; and fuel capacity limited the flight time to just over 20 seconds. So after demonstrating it for the military, Bell started flogging it at state fairs, Disneyland, the Paris Air Show and numerous international exhibitions, ultimately hiring it out for the opening sequence of "Thunderball," a commercial for P. F. Flyers sneakers and episodes of "Lost in Space" and "Bewitched."
Further refinements yielded the Flying Chair (1965), which mounted a Rocket Belt apparatus on one of Eero Saarinen's stylish Tulip chairs, and the Pogo (1968), which put the device on a flying platform.
In 1968 Bell, in collaboration with the Michigan-based contractor Williams Research Corporation, unveiled the Jet Belt, which used a miniature kerosene-powered jet engine. This device could accelerate to 70 m.p.h. from a hovering position in three seconds and was capable of sustained flight for 10 minutes. A test pilot told Popular Science magazine that the Jet Belt made him "feel safer than I do driving the family car in traffic." Of course, the jet engine was tremendously heavy and nearly deafening, but hopes for it were high. A year later, however, Wendell Moore, still the device's chief engineer, died of a heart attack. Subsequently the military declined to commission mass production of the Jet Belt, and in early 1970, Bell Aerosystems sold all related patents to Williams.
At Williams, the Jet Belt's engine became the centerpiece of the WASP, or Williams Aerial Systems Platform. Developed in two stages over the next 15 years, the WASP II was a 250-pound cylindrical tub resembling a flying garbage can. Hard as it is to believe, it could fly at speeds up to 60 m.p.h. for as long as 30 minutes.
The WASP II was featured in Jane's All the World's Aircraft as late as the 1984-1985 edition, but again the army, which had financed its development, lost interest. Further attempts by Williams to market it under the name X-Jet failed, and then . . . nothing. No more test flights, and a subsequent abandonment of individual flight systems. Today the company is curiously reticent on the subject: though jetpack fanatics continue to call with inquiries on a regular basis, a spokesman for Williams dismisses the issue as something from "the very old past."
Several years ago, Derwin M. Beushausen, an enthusiast from the Midwest, distributed a videotape of short films made by Bell that documented test flights of the Rocket Belt, Flying Chair, Pogo and Jet Belt. Like people Jet Skiing through the sky, Bell's implacable fliers slalom effortlessly through and over trees, zoom across whitecapped river rapids, whip alongside steep cliffs, float above warehouse roofs and hover over a lawn, turning slow rotations for a group of military observers. They are among the most thrilling, and also heartbreaking, images I've ever seen. I sit watching the tape and think only: Why? Why can't I fly one of those things?
"Jetpacks?" asks Frank Winter, curator of rocketry at the National Air and Space Museum. "I think here we call them Personal Lifting Devices," he says. The museum owns the Bell Aerosystems Rocket Belt No. 2, which is slated for display at the Dulles Center, in conjunction with the Smithsonian, scheduled to open in the year 2003. "People still call me about them every so often, but you know it was a commercial failure. It wasn't a practical reconnaissance device." Winter must sense how crestfallen I am. "It really was ingenious," he adds. "I'm not knocking it. You know, it's too bad that it wasn't picked up."
These days, the only new jetpacks are the ones worn by astronauts. NASA calls them M.M.U.'s, or manned maneuvering units: worn in a backpack configuration similar to the Rocket Belt, they use nitrogen fuel to propel and guide movement during spacewalk activity. In the earth's gravity, however, M.M.U.'s would be far too weak to function.
Rocket Belts, with their 20-second flight duration, are still used for show-business purposes; memorably, in 1984, millions watching the opening ceremonies of the summer Olympic Games witnessed a former Bell pilot, Bill Suitor, descending into the Los Angeles Coliseum, trailing clouds of white exhaust behind him. But all of the subsequent research and development has seemingly been for naught.
A note sent to me by Williams tersely explains that testing of the X-Jet was stopped when they concluded that "in order to make feasible more useful applications, [it] would require substantially improved performance from its turbofan engine." Winter agrees: "Even 30 minutes of flight time would be too limited for commercial purposes. If you're a park ranger, fighting a fire, what if you need 35 minutes, or two hours?" Still, he concedes that "if the right entrepreneur came along, it could be a neat attraction. We may not be looking at the last chapter with this sort of device."
So where are our jetpacks? Might they still be part of a future to come? The last line of my final communication from Williams holds out a sliver of hope. "Year by year," it says, "we are continuing to advance our turbofan technology." But if somehow, miraculously, we were to get them, would they prove to be more nightmare than dream -- as in the current television commercial for Budget Rent-a-Car, in which a jetpack user becomes hopelessly entangled in power lines? Were these devices easy to use and readily available, would our urban skies mirror the jammed rush-hour streets and freeways below? Though it saddens me to think so, maybe the answer is that jetpacks no longer exist in the future but behind us, receding into the past: a device for memory instead of flight.

 Martin "JetPack" Controllability Free-Flight (Indoor)

Other tipes of Vertical Take Off and Landing (VTOL) systems


  1. Do you have any idea what kind of fuel was used in the X-Jet? I was also curious the amount of fuel? I find the x jet to be very interesting and wonder why it hasn't been redone yet.

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