Propellant packs used for individual flight, rather than for aircraft.
The jet pack is a device to allow a single person to fly without being enclosed in an aircraft. Jet packs first came to public attention during the opening ceremonies of the 1984 Summer Olympic Games in Los Angeles, California. The jet pack itself attaches to a regular backpack.
The inventor of the first practical jet pack, or rocket belt, was Wendell F. Moore. In the early 1950’s, Moore was an engineer at Bell Aerosystems and worked on the concept of small, light system mounted on a person’s back, that could be worn into battle. The idea had first been proposed by the Germans, who had been working on it at the end of World War II. However, Moore found very few people at Bell willing to fly the jet pack more than once or twice. Fortunately, Moore’s nineteen-year-old neighbor, William P. Suitor, had watched him working on the project in his backyard and was eager to fly the rocket belt. Suitor was hired by Bell in 1964 to work with its designers and engineers to learn to fly the new aircraft, at first on tethers, then in free flight. Suitor became known as the “Rocket Man.”
The rocket belt or jet pack used a hydrogen peroxide reaction rocket engine. The engine has a tank of compressed liquid nitrogen that pushes hydrogen peroxide out of two other tanks into a reaction chamber, a box with silver screens coated with samarium nitrate. This box reacts to the hydrogen peroxide, in turn creating a high-pressure steam that propels the belt as it flows out of the flight nozzles. The steam is so hot that it renders the jet pack not only quite dangerous but also loud, emitting a screaming sound. Nevertheless, the pack handles amazingly well.
In addition to the original Bell rocket belt, there is the RB2000, designed by Brad Barker, Joe Wright, Larry Stanley, and Doug Malewicki. These men used the basic principle and design of the original Bell model but managed to increase the flight time from 20 to 30 seconds. Various improvements, such as the use of new materials that can withstand higher temperature, have led to a lighter belt. The importance of such a belt is its ability to carry more propellant while still being comfortable for the pilot. Nonetheless, 30 seconds is the most one can expect to fly with the belt. In order for the jet pack to be really practical, it will be necessary to develop tiny jet engines to power it, which can be used in concert with the lightweight hydrogen peroxide rockets for fast takeoff, higher altitude, and longer flights.
Given its early promise, it is surprising that jet-pack technology failed to make an impact on personal transportation during the late twentieth century. There are hopes that the twenty-first century will finally see it achieve its promise as a viable means for personal travel.
Jet packs, once purely science fiction, are now part of the standard equipment of astronauts. The pack is a device fitted with pressurized metal containers that let out jets of gas, worn by astronauts on their backs to enable them to move around in space outside a spacecraft. The National Aeronautics and Space Administration (NASA) has introduced a new version of the jet pack called Simplified Aid for Extravehicular Activity Rescue (SAFER). This pack is a backup for the traditional tether that attaches the astronaut to the spacecraft. It is intended as an extra precaution for astronauts working outside space vehicles. The jet pack is also useful as a rescue device for astronauts who work outside spaceships. This pack was first tested in 1994 during a flight of the space shuttle Discovery. Astronauts Mark Lee and Carl Meade were the first to test the jet pack in space on September 16, 1994.
The pack weighs 80 pounds and carries 3 pounds of nitrogen propellant. There are twenty-four 1-inch-long thrusters, four to each side of a cube. Astronauts use a joystick fastened to the chest of the spacesuit to control their maneuvers. After astronauts right themselves, the packs enable them to get back to their vehicles at a maximum rate of 10 feet per second, or just over 6 miles per hour. The average speed, however, is closer to 1 mile per hour. There is little time for hesitation, since the packs only hold thirteen minutes of propellant fuel.
SAFER maneuvers much more easily than the previous 340-pound pack last used in 1984, the Manned Maneuvering Unit (MMU). Unlike the MMU, the new jet pack is worn during routine space walks. The astronaut can use various combinations of the jets to control pitches and rolls. The jet pack, which is rather boxy in shape, clips onto the regular backpack. There is a liquid crystal display allowing the astronaut to monitor information about fuel and battery power. There is also a computer in the pack to control the deployment of jets to stabilize the falling astronaut.
The development of SAFER has given greater credibility to the jet pack. Extravehicular activity emergencies are an astronaut’s worst nightmare. SAFER provides the astronaut a good chance to get back to the vehicle even in a worst-case emergency scenario. The first test of the jet packs was a success. However, two subsequent trials revealed problems. In 1997, the jet thrusters of Scott Parazynski’s pack failed to fire. In 1998, Jerry Ross’s pack burned his nitrogen gas at a higher rate than expected. These problems led NASA to conduct rigorous ground tests to locate and solve the problems. Astronauts compare jet packs to parachutes: pieces of equipment that they hope never to use, but that are reassuring to have available.
Hecht, Jeff. “Finding Your Way Back Home.” New Scientist 168, no. 2262 (October 28, 2000): 16. The use of SAFER, a jet pack for astronauts. Kiernan, Vincent. “How Not to Get Lost in Space.” New Scientist 143 (September 24, 1994): 7. A detailed discussion of SAFER. “Put Your Faith in Engineering.” Discover 15 (December, 1994): 22. A discussion of the jet pack. Wolf, Jaime. “Canceled Flight.” The New York Times Magazine, June 11, 2000, 36. More details on astronauts and the jet pack.
Astronauts and cosmonauts
National Aeronautics and Space Administration
Jet packs have not proved practical for daily transport, but they often add a touch of excitement to festive occasions such as the Rio de Janeiro carnival samba parade.