In The Great American Jet Pack: The Quest for the Ultimate Individual Lift Device, Steve Lehto (Chrysler’s Turbine Car), offers a definitive history of the jetpack and comparable solo flying devices—like flying shoes, hovering platforms and jet belts—explaining how the extraordinary technology arose, how they worked and why they never became the commercial success they were expected to become. With a colorful cast of characters—inventors, scientists, hucksters and cheats—The Great American Jet Pack tells the essentially American story of man’s pursuit of flight without wings and the technology whose promise may one day yet be realized—perfect for technology fans, history buffs and anyone who has dreamed of what it would be like to fly.
And thanks to our friends at Chicago Review Press, we’re presenting a fantastic excerpt of this entertaining and illuminating book.
A variety of stories are told of the origins of rocket belt technology and how it first caught the attention of the military. One involved an army officer named Colonel Charles Parkin at West Point in 1940 who was training men to use flamethrowers. At the time, flamethrowers used tanks of nitrogen to propel the flammable liquid, and one of Parkin’s soldiers accidentally opened a valve on a nitrogen tank he thought was empty. He quickly closed the valve on the hissing tank and asked Parkin what would happen if the valve were opened all the way with a full tank. Parkin told him, “It would probably go skittering across the field.”
The soldier jokingly asked, “Could I hang on and get a ride?” Parkin wondered about it.
After the war, he remembered the exchange and decided to try a little experiment. He said he found one of the nitrogen tanks and strapped it to his back. He opened up the valve and jumped. He felt that the thrust of the tank aided his jump, more than enough to make the project worth pursuing. After all, the tank was heavy and there might be more efficient things to power such a device. What if some of our best scientists and engineers worked on this notion? By 1957, Parkin was working in the army’s Transportation Research and Engineering Command, known as TRECOM, and he had not forgotten about his experiments with compressed nitrogen.
With the advances in rocketry that had been made during World War II, a lot of people had been thinking about strapping themselves to rockets or vice versa; it is hard to say who had the idea first. The idea very well could have been so obvious that it spontaneously occurred to several different people. In 1945, a French inventor named Marcel Marin filed a US patent for “Steering of Portable Reaction Motors.” While the title may not suggest a jet pack, the accompanying illustrations on the patent do. A man is shown on skis—both on water and snow—with a small rocket apparatus attached to his back with a harness. The inventor was clear that his device would likewise propel a person on roller skates, a bicycle, or in a “light car.” Clearly this was not a flying device, but the similarities are obvious enough. Marin did not specify what type of motor his invention would carry or what kind of fuel it would use but gave an array of possibilities including liquid or solid fuel rockets and compressed gas.
Marin’s was not the first patent for a wearable rocket. A Russian scientist had filed an interesting patent long before World War II. In 1929, Nikolai Alekseevich Rynin wrote a book titled Interplanetary Flight and Communication. The work was speculative in nature and contained a survey of sorts, showing all of the steps taken by man to fly, including the rudimentary flying machines, balloons, and rockets developed by this time. The book was also filled with fantastic products of the imagination, things people had thought of but not actually developed. Many of them were mythical, such as the Chinese inventor who is said to have blown himself up several thousand years ago trying to fly a rocket-powered kite. Buried deep in the book’s second volume was a description of something called “Andreev’s Rocket Apparatus,” the subject of a patent in Russia granted to a man named A. F. Andreev. Perhaps due to the oddities of 1920s Russian patent law or due to bad translations of Interplanetary Flight, the patent was said to have been granted in 1928, retroactively to 1924, even though it had been filed in 1921. The invention was described as “a portable rocket apparatus which . . . a person could carry on his back like a knapsack.” It was to be powered by methane and oxygen and was “intended for the transportation of a person or small loads for a distance up to 20 km.” According to the patent, it would also travel at around 120 miles per hour, and only weighed one hundred pounds. The fuel only weighed sixteen pounds. It is worth noting that the proposal suggested the device could travel twelve miles on a single load of fuel. If nothing else, this patent proved one thing: exaggeration in this field had begun by 1921.
Rynin’s book included a copy of the patent illustration but it would have been little use to anyone curious about the device’s planned operation. Its description said that a person could wear the device and control the “angle of inclination of the gas jets in relation to the apparatus as a whole.” There was no hint that Andreev ever tried to build his device, nor any explanation of how he derived his projected performance figures. Andreev’s only contribution to this field seems to be that someone else saw his patent and wondered if a man could strap a rocket to his back and live to tell about it.
Thomas Moore was a scientist who worked closely with Werner Von Braun in the 1950s. Along with other rocket scientists, they were making huge strides toward putting a man on the moon. Maybe they could also build a small man rocket? Von Braun told Moore he liked the idea and in 1951 he helped Moore lobby the government for development money. The army gave Moore $25,000 to flesh out the idea. Moore came up with a design that would be powered by a mix of hydrogen peroxide, ethyl alcohol, and liquid oxygen. He later told people he had been inspired by the Andreev patent.
Moore imagined a “Jet Vest” with fuel tanks that would be worn on the back. Fuel from those tanks would enter a combustion chamber and a chemical reaction would blast exhaust out through vent tubes that pointed downward, behind the pilot. The exhaust would rush out of the tubes with such force that it would lift the pilot wearing the Jet Vest off the ground. Moore built a mock-up of the vest for testing. Before he built the motors, he needed to know if the Jet Vest would fly and if it would be controllable. He built the plumbing portion of the Jet Vest and connected it to high pressure air hoses, much as Zimmerman and Hill had used compressed air to power their hover board. He then strapped himself in and blasted away while attached to safety tethers. As far as we know, he never managed untethered flight with the Jet Vest. He also never configured the vest to be operated with the rocket fuel motors. After the money ran out, he apparently didn’t have enough to show the army and no further funding was given.
Did Moore see Andreev’s patent in Rynin’s book? If so, he may have wanted to heed a warning on the first page. Rynin noted that the science of rocketry went back thousands of years but rocket designers still encountered numerous technical problems. Rocket engines developed such high temperatures that the rockets often destroyed themselves when they flew. Rockets flew very fast but often only for short periods; the fuels were dangerous; the engines often produced too little power to be practical; and the contraptions were difficult to control. Could Cold War–era scientists overcome all of these obstacles to make a wearable man rocket?
As is often the case in modern technology, engineers and scientists at different companies were working on the problem independently of each other. A company called Thiokol Chemical Corporation—Reaction Motors Division announced it had been working on a rocket device for a man to wear. The company called it a jump belt. Initially, Thiokol had made solid-fuel rocket engines and Reaction Motors had been making liquid-fuel rockets. Thiokol bought Reaction Motors in 1958, and by the end of the year the new conglomerate announced a groundbreaking invention it had teamed up to build. In presenting its device, the company claimed to have had conducted some interesting experiments. According to Thiokol, tanks of compressed nitrogen were strapped to a man’s back in a configuration that allowed him to blast 350 pounds of thrust for five seconds out of small nozzles at his waist. Thiokol claimed that its test pilot had managed to jump thirty feet horizontally and fifteen feet high using this nitrogen-powered contraption. It is unclear how a man could jump fifteen feet up without getting hurt on the way down. Did the system also break his fall somehow? Thiokol only produced photographs of a man blasting a large cloud of dust at an altitude of perhaps three feet. But more interesting was the company’s claim about the man running with the unit on his back: Thiokol said that he hit twenty-two miles per hour, albeit briefly, when he fired the unit for five seconds while simply running along the ground. Again, it seems hard to believe. How did the man’s feet keep up with the jet blast? How did he slow down and stop afterward? Thiokol was long on promises and short on evidence for the press, but the press played along, publishing the performance numbers without questioning them.
In June 1958, Thiokol had shown their nitrogen unit to the army. The military was curious enough to ask Thiokol to build something that would run longer than five seconds. Thiokol built a unit powered with hydrogen peroxide, one of the liquids Thomas Moore had used in his experiments. This was successful, but Thiokol only considered using its jump belt for augmenting a man’s jumping or running ability. The company did not imagine the invention had the ability to hold a man in the air once he had jumped.
Thiokol shelved the hydrogen peroxide unit and instead developed the jump belt, powered by little rocket motors. Popular Science magazine reported on “Man’s first leap toward free flight,” and boldly stated, “Man’s age-old dream of flying like a bird, free of any clumsy machinery, may be nearer than we think.” The article described a belt holding five canisters that sat against a man’s back. On each side of the belt were nozzles that aimed downward. The canisters contained solid rocket fuel that burned for a few seconds, and the resulting jet blast was ducted to the side nozzles. The canisters could be fired one at a time or all at once. In sequence, they would give perhaps a minute of boost. Thiokol told Popular Science that the exact facts and figures of the device were classified but the company made it clear that it was on the verge of a breakthrough. Thiokol told the writer that a man wearing this belt could “broad-jump a 50-foot river,” “leap from the ground into a second-story window,” or “race off at 35 m.p.h.” It is important to note that no one had ever done any of these things while wearing one of these devices. And, once again, a manufacturer of an individual lift-type device resorted to exaggeration to try to sell an invention.
Thiokol pitched the solid-fuel rockets for use in slowing the descent of paratroopers. The company theorized that a parachuting soldier could wear one of the jump belts and fire the rockets a moment before he hit the ground. This would enable the paratrooper to soften the impact of an otherwise potentially hazardous landing. As odd as this sounds, the United States later discovered that the Soviets utilized just such a rocket braking system when dropping large payloads of cargo by parachute. They did not use them for individual soldiers, however.
Thiokol told the reporter that the rest of the story was classified. It is unclear if the writer asked how far the experiments had progressed with the solid-fuel jump belt. Thiokol gave Popular Science photographs of a man wearing “a crude early version of the one-man jump belt” and claimed that the photographs showed the man “Breaking the world’s broad jump record (26 feet 8. inches).” The photographs are grainy, on the order of pictures provided of alien autopsies or Bigfoot sightings. Still, simple comparison of the photo of the man jumping and the one of the man landing make it clear that, at least in these pictures, the man did not clear twenty-six feet. It appears that the Popular Science writer simply took the Thiokol statements at face value and assumed that there must have been more to the story, particularly behind the curtain of classified information. This practice, too, would become common in the arena of personal flight. While developers were happy to exaggerate and overpromise, the press was more than happy to uncritically repeat almost anything it was told about the inventions.
Within the article about the solid-fuel jump belt, Thiokol revealed another experimental device to Popular Science readers: “The hush-hush flying belt.” Thiokol provided the magazine with photos of a man wearing a couple of different contraptions. Photographs showed larger tanks strapped to a man’s back with tubing extending from the tanks. In one picture, the exhaust pipes went straight out from the man’s shoulders and then pointed downward. In the other, a single pipe snaked up and around the tanks and pointed down behind the man. The devices were clearly variations of Thomas Moore’s Jet Vest.
These hitherto unreleased photos show an early model of the secret “Flying Belt.” In view at right, jets and control are folded for maximum convenience; in the other they are in flying position. Thrust angle is changed by moving the control forward or back, and amount of thrust or lift is varied by the movement of the hand grip. The belt would enable the wearer to rise quickly to an altitude of several hundred feet and fly “miles.” How soon will the Flying Belt emerge from the laboratory? Reaction Motors’ engineers estimate delivery of a workable one within two years.
Oddly, Thiokol did not say if it had gotten the flying belt off the ground, and it did not mention how the unit worked or what fuel it would use. Yet people within Thiokol had figured out the answer: hydrogen peroxide.
Colonel Parkin followed these developments with great interest, remembering his own primitive experiments. Now, with major aerospace players involved in the field, he convinced TRECOM to investigate whether American scientists could build a practical “jump belt.” Parkin would see to it that the scientists had the necessary funding to fully develop the technology.
