Mommy, I Want a Jetpack

It should be here by now. Advances in technology manifested in the form of touch screens, voice recognition, and holograms were once just dreams within the realm of science fiction not too long ago. Just a century ago, space travel was considered unfathomable, a concept strictly restricted to comic books and movies. However, forty years ago, something happened that epitomized the huge leap of progress that technology the world has made over the years: we sent a man to the moon. While this feat of engineering is mind boggling, the development of the jetpack pales in comparison. Amidst the whirlwind of breakthrough technologies, the advancement of the jetpack has been relatively stagnant. Although its purpose may not be as tangible as some of the aforementioned inventions, if perfected, the jetpack could have numerous applications transportation, recreation, and in the military. As inventors attempt to engineer personal flying machines, the jetpack’s history resembles that of the airplane—only without the Wright brothers. Despite some modest progress, nothing has embodied the sustained, unrestricted flight of characters such as Star Wars’ Boba Fett or Iron Man (see Fig. 1).

A closer examination of the jetpack’s development reveals that it has long been hindered by certain design challenges that still trouble engineers today. Even the most elaborate, exclusive, and expensive models can’t quite match the ideal vision conceived by science fiction. Numerous prototypes have emerged but none efficient enough to be released to the public. Its sputtering history and modern designs reveal why the conception of the jetpack has never overcome challenges of duration, cost, and mobility.

Not until a quarter through the 20th century did the mere idea of a jetpack reach the public eye. In 1928, a science fiction magazine called Amazing Stories published a story about a veteran World War I pilot named Captain Anthony Rogers. Known as “Buck”, the protagonist used a compact jet engine on his back to fly around and fight crime in the future (see Fig. 2). Buck Rogers quickly gained popularity and eventually became a prominent comic series, television show, and movie. By the 1930s, fiction was on the verge of reality when a Russian man named A. Andreev patented an oxygen and methane-fueled flying device. Complete with three-foot wings, a motor would be worn to produce enough power for liftoff. Mark Wells, a research engineer who once worked for NASA and the US military, called Andreev’s contraption “the first device of its kind that had any engineering detail at all”. However, the design was never actually tested [1].

Also referred to as the “rocket pack”, “rocket belt”, or “jet vest”, the jetpack reached a milestone in the late 1940s when engineers at a military base in Alabama began researching rockets that could lift a person and allow him or her to land safely upright. In 1959, the US Army contracted Bell Aerosystems to create a “small rocket lift device” for “light mobility systems missions”. The machine utilized motorcycle-type rotating grips for throttle and was powered by hydrogen peroxide. Eventually called the Bell Rocket Belt, its breakthrough came in 1961 when pilot Harold Graham flew for thirteen seconds [2, 3].
During the mid-60s, the Bell Rocket Belt gained significant exposure as Sean Connery wore one in his blockbuster James Bond film, Thunderball (1965) [3]. Some organizations and individuals continued to spend time and money on its research, including Bill Suitor, who did stunt work as James Bond. Suitor eventually became known for perhaps the most memorable jetpack flight in history, when he flew the rocket belt for seventeen seconds inside the LA Coliseum at the opening ceremonies of the 1984 Olympics. Two and a half billion television viewers from around the globe watched him soar across the field. It appeared that the jetpack had finally arrived, with the Bell Rocket Belt as the primary design [1].

It’s important to note that the Bell Rocket Belt, arguably the most famous jetpack in history, is not actually a jetpack. Like its name suggests, the device utilizes rocket propulsion instead of a jet engine. Bell Aerosystems also proposed a “Jet Belt”, but the Pentagon turned it down because it was too heavy and bulky [2]. Thus the rocket approach was at the forefront of developing the jetpack, and hydrogen peroxide proved to be the most economical fuel.

The image on the left in Fig. 3 looks futuristic and complex, but its functioning principle is quite simple. The three tanks are standard on a Bell Rocket Belt. Labeled number one in the diagram on the right, the center tank is filled with pressurized nitrogen gas. The outside tanks (number two) are full of hydrogen peroxide. When triggered, the nitrogen pushes the hydrogen peroxide through two pipes and into a chamber (number three) filled with a catalyst, typically made of silver. This catalytic reaction violently decomposes the hydrogen peroxide into superheated steam and oxygen. The hot, high-pressure gas is split through a valve and shoots out two nozzles, generating a thrust with gas velocity at about 1000 meters per second [4].
This technology dominated the world of jetpacks for over three decades, and some inventors still use it today. Since the chemical reaction is so reliable, it allows engineers to focus on meticulous issues like altering the sensitivity of the nozzles to balance thrust and yaw, or side to side movement. But despite the allure of hydrogen peroxide rockets, progress has literally and figuratively hit a ceiling. Although it can “accelerate faster than a Formula 1 car”, the Bell Rocket Belt and its variations have yet to fly for over a minute. This is unlikely to change because the additional weight of larger gas tanks negates the upward lift. And in over forty years of development, it is still difficult to fly and requires a lightweight pilot [5, 6]. With these limitations and diminished funding, the rocket belt has been forced into obscurity. Jetpack enthusiasts must have faith that innovation will save their dreams.

Latest but not Greatest Attempts

Following the Bell Rocket Belt, believers in the jetpack have pursued various techniques in hopes of glory. Swiss daredevil Yves Rossy, nicknamed the “Jetman”, essentially engineered a personal jet plane. It resembles something that a 12-year-old would doodle in class: a concoction of homemade carbon wings attached to jet engines, which he straps on his back (see Fig. 4). Rossy has been compared to the pioneers of flight in the early 20th century who would risk death for success [7]. Any doubters were silenced last year, when he dropped from a helicopter and flew 8,000 feet above the Grand Canyon at almost 200 miles per hour [8]. Just based on the numbers, one quickly realizes that the jet engines are far more powerful than their rocket counterpart. In a jet engine, a continuous charge of fuel forces compressed air to expand through a turbine. This creates an explosion of gas out a narrow opening at high speeds, which provides the thrust [9].

Rossy’s impressive flight may be the best real life reenactment of Iron Man, but it falls short in other aspects. The engine-wing jetpack weighs about 120 pounds, and any slight movement of the head, shoulders or arms will diverge its path [8]. Not only is it extremely dangerous, his flight started from a helicopter, which defeats the very purpose of a jetpack.

Instead of a chemical reaction or jet fuel, the Jetlev R200 makes use of the world’s most available resource: water. Created by Raymond Li and tested in 2009, the device looks like a traditional jetpack with back strap, nozzles, and handlebars. Of course, this is excluding the 33-foot-long hose connected to a floating vessel that contains a 255 horsepower engine, as one can see in Fig. 5. When engaged, the motor pumps high-pressure water up through the hose and out the nozzles of the pack. The shooting streams of water create a reaction force that propels the rider up to 28 feet in the air. The sensation has been described as “a bit like riding around on a pair of fire hoses” [3, 10].
Figure 5 illustrates the Jetlev’s operation and although it looks thrilling, it has not solved the world’s jetpack problems. For instance, to actually own such a toy would run you about $100,000. This is discouraging when considering its inability to reach ten yards above the water, let alone the ground. The Jetlev is quite an engineering achievement but cannot provide the freedom of flight essential to a jetpack.

Similar to Yves Rossy creating a personal jet plane, Glenn Martin has spent years designing a jetpack that is virtually a personal helicopter. Martin and his team have engineered a two-stroke gas engine that spins a pair of ducted fans, generating enough thrust to lift a person [10]. Because it is defined as a small vertical take-off and landing aircraft (VTOL), Martin’s jetpack is not subject to the same regulations as helicopters and fixed wing aircraft. Nevertheless, the engineers have designed it to comply with the ultralight standards of the Federal Aviation Administration, technically making it the safest jetpack ever assembled [6]. In 2011, the jetpack flew for almost ten minutes and reached 3,500 feet. If it had been holding a live person instead of a dummy, Martin’s design would have easily broken the record for longest flight (and highest discounting Rossy) [10].

The Martin Jetpack has many promising features, including a potential flight time of thirty minutes and speed of sixty miles per hour. Granted that this may be the best piece of jetpack technology available today, it still falls short in other respects. The Martin Jetpack joins the Jetlev for having a $100,000 price tag (keep in mind that Rossy’s design isn’t for sale). In addition, a two-week training session is required before flight [10]. With mediocre control over lateral movement, this jetpack fails with the rest of its contemporaries.

Besides the obvious flaws with the aforementioned models, there are some common design challenges that must be overcome before the jetpack truly takes off. Considering the record for longest manned flight is just minutes, engineers must find ways to extend its duration. This poses a problem for rockets and jet engines since a limited amount of fuel can fit on a person’s back. Martin’s fan-powered device may expend less fuel, but its large size is a drawback. With a machine that huge, one might as well take a helicopter. Perhaps the evolution of the jetpack will mock the computer and become smaller over time. Until then, the noisy, short-lived, and oversized prototypes will keep the public at bay.
Another glaring setback with current jetpack technology is that it fails to truly capture the desired freedom of movement. The Rocket Belt and Martin Jetpack lack the ability to quickly accelerate in the horizontal direction; Rossy’s jet wings cannot take off and land vertically; and the Jetlev is permanently attached to a water hose. Nick Sagan (son of famous scientist Carl Sagan), writes, “I think that’s a shame because there’s something really exciting about the possibility of going wherever you want with your jet pack. It’s the ultimate expression of control over our dominion” [2].
The problem with increased mobility is that it often entails navigational issues. This has plagued jetpack inventors since the original Bell Rocket Belt. Bill Suitor once compared the act of flying like “trying to stand on a beach ball in a swimming pool” [5]. Furthermore, most designs of today cite a weight limit for pilots (around 175 pounds) [2]. Factor in safety issues due to midair malfunctions and burns from exhaust, and the concept of a practical jetpack seems to fade away.

Up until 2007, only seventeen people had ever flown a jetpack [5]. With exorbitant price tags and limited functionalities, the jetpack remains a questionable investment in the eyes of the public. With the allure of giving individuals the freedom of flight, the jetpack has fueled the ambitions of engineers all around the world to think outside the box leading to inventions such as the Jetlev and the Bell Rocket Belt. However, its initial exponential progress soon plateaued, leaving engineers scratching their heads. In the case of the jetpack, a revolutionary design has eluded us. Its flight control, mobility, and sustainability issues have spoiled the hopes of the population. Maybe some day we will be able to enjoy its capabilities, but until then, it’s reserved for comic books, special agents, and the Jetsons.