Jet pack

A jet pack, rocket belt, rocket pack or flight pack is a device worn as a backpack which uses jets to propel the wearer through the air. The concept has been present in science fiction for almost a century and the first working experimental devices were demonstrated in the 1960s.
Jet packs have been developed using a variety of mechanisms, but their uses are limited because of factors including the Earth's atmosphere, gravity, the low energy density of extreme fuels, and the human body not being suited to flight, so they are principally used for stunts.
A practical use for the jet pack has been in extra-vehicular activities for astronauts because of the weightlessness and lack of friction-creating atmosphere in orbit. The term jet suit is used for a system incorporating a jet pack and associated jets attached to the arms to increase manoeuvrability.

Overview

In the most general terms, a jet pack is a wearable device which allows the user to fly by providing thrust. With the exception of use in a microgravity environment, this thrust must be upwards so as to overcome the force of gravity, and must be enough to overcome the weight of the user, the jet pack itself and its fuel. This necessarily requires the jet pack to continually push mass in a downwards direction.
While some designs have power and/or mass supplied from an external, ground-based source, untethered flight requires all of a flight's fuel to be carried within the pack. This results in problems relating to the overall mass ratio, which limits the maximum flight time to a few minutes, rather than the sustained flight envisaged in science fiction.

Rocket pack

Liquid-fueled rocket pack

Andreyev: oxygen-and-methane, with wings

The first pack design was developed in 1919 by the Russian inventor Alexander Fedorovich Andreev. The project was well regarded by Nikolai Rynin and technology historians Yu. V. Biryukov and S. V. Golotyuk. Later it was issued a patent but apparently was not built or tested. It was oxygen-and-methane-powered with wings each roughly long.

Hydrogen peroxide–powered rocket packs

A hydrogen peroxide–powered engine is based on the decomposition reaction of hydrogen peroxide. Nearly pure hydrogen peroxide is used. Pure hydrogen peroxide is relatively stable, but in contact with a catalyst it decomposes into a mixture of superheated steam and oxygen in less than 1/10 millisecond, increasing in volume 5,000 times: 2 H₂O₂ → 2 H₂O + O₂. The reaction is exothermic, i.e., accompanied by the liberation of much heat, forming in this case a steam-gas mixture at. This hot gas is used exclusively as the reaction mass and is fed directly to one or more jet nozzles.
The great disadvantage is the limited operating time. The jet of steam and oxygen can provide significant thrust from advanced rockets, but the jet has a relatively low exhaust velocity and hence a poor specific impulse. Currently, such rocket belts can only fly for about 30 seconds.
A more conventional bipropellant could more than double the specific impulse. However, although the exhaust gases from the peroxide-based engine are very hot, they are still significantly cooler than those generated by alternative propellants. Using a peroxide-based propellant greatly reduces the risk of a fire/explosion which would cause severe injury to the operator.
In contrast to, for example, turbojet engines, which mainly expel atmospheric air to produce thrust, rocket packs are far simpler to build than devices using turbojets. The classical rocket pack construction of Wendell Moore can be made under workshop conditions, given good engineering training and a high level of tool-making craftsmanship.
The main disadvantages of this type of rocket pack are:

Short duration of flight.
The high expense of the peroxide propellant.
The inherent dangers of flying below minimum parachute altitude, and hence without any safety equipment to protect the operator if there is an accident or malfunction.
Safely learning how to fly it, given that there are no dual-control training versions.
The sheer difficulty of manually flying such a device.

These circumstances limit the sphere of the application of rocket packs to spectacular public demonstration flights, i.e., stunts; for example, a flight was arranged in the course of the opening ceremony of the 1984 Summer Olympic Games in Los Angeles, USA.

Justin Capra's flying backpack

claimed that he invented a "flying rucksack" in 1956 in Romania, and, without arousing any apparent interest, informed the American Embassy of his idea. However it was tested by Henri Coandă, a paratrooper who crashed it the first time but managed the second after he advised to change the fuel and improve on the design. In 1962 a backpack was created at Bell Laboratories, following Justin Capră's prototype. The backpack is now displayed in a museum.

Jump Belt

In 1958, Garry Burdett and Alexander Bohr, Thiokol Corporation engineers, created a Jump Belt which they named Project Grasshopper. Thrust was created by high-pressure compressed nitrogen. Two small nozzles were affixed to the belt and directed vertically downward. The wearer of the belt could open a valve, letting out nitrogen from the gas cylinder through the nozzles, which tossed him upward to a height of. While leaning forward, it was possible with the aid of the jump belt's thrust to run at. Later, Burdett and Bohr tested a hydrogen peroxide–powered version. The jump belt was demonstrated by a serviceman in action, but as no financing was forthcoming, there was no further testing.

Aeropack

In 1959 Aerojet General Corporation won a U.S. Army contract to devise a jet pack or rocket pack. At the start of 1960 Richard Peoples made his first tethered flight with his Aeropack.

U.S. Army interest

Transport studies of the U.S. Army Transportation Research Command determined that personal jet devices could have diverse uses: for reconnaissance, crossing rivers, amphibious landing, accessing steep mountain slopes, overcoming minefields, tactical maneuvering, etc. The concept was named "Small Rocket Lift Device", SRLD.
Within the framework of this concept, the administration concluded a contract with the Aerojet General company in 1959 to research the possibility of designing an SRLD suitable for army purposes. Aerojet came to the conclusion that the version with the engine running on hydrogen peroxide was most suitable. However, it soon became known to the military that engineer Wendell F. Moore of the Bell Aerosystems company had for several years been carrying out experiments to make a personal jet device. After becoming acquainted with his work, servicemen during August 1960 decided to commission Bell Aerosystems with developing an SRLD. Wendell Moore was appointed chief project engineer.

Bell Textron Rocket Belt

In 1960, the Bell Rocketbelt was presented to the public. The jet of gas was provided by a hydrogen peroxide–powered rocket, but the jet could also be powered by a turbojet engine, a ducted fan, or other kinds of rockets powered by solid fuel, liquid fuel or compressed gas.
This is the oldest known type of jet pack or rocket pack. One Bell Rocket Belt is on display at the Smithsonian Institution's National Air and Space Museum annex, the Steven F. Udvar-Hazy Center, located near Dulles Airport.

RB-2000 Rocket Belt

This was a successor to the Bell Rocket Belt.

Bell Pogo

The Bell Pogo was a small rocket-powered platform that two people could ride on. Its design used features from the Bell Rocket Belt.

Powerhouse Productions Rocketbelt

More commonly known as "The Rocketman", Powerhouse Productions, owned and operated by Kinnie Gibson, manufactures the 30-second flying Rocketbelt and organizes Rocketbelt performances. Since 1983 Powerhouse Productions has performed show flights in over 40 countries such as the Carnival in Rio de Janeiro, Super Bowls, the Rose Parade, Daytona 500, and the Michael Jackson Dangerous World Tour, as well as many television shows including Walker, Texas Ranger, The Fall Guy and NCIS. Powerhouse Rocketbelt pilots include stuntman Kinnie Gibson and Dan Schlund.

Jetpack International

Jetpack International made three models of wingless jet packs. The company stated that the could fly 152 meters, using hydrogen peroxide fuel for its rocket engine. It was flown for 34 seconds in Central Park on the 9 April 2007 episode of the Today Show and sold for $150,000. Their H₂O₂ jet pack was for demonstration only, not for sale, but the company stated that it could fly 457 meters, also with the hydrogen peroxide rocket engine. The T-73 was expected to fly up to 18 meters using Jet-A fuel and a jet engine, and to sell for $200,000.

Later technology

At the TechCrunch Disrupt conference in 2014, Astro Teller, head of Google X, said they investigated jet packs but found them too inefficient to be practical, with fuel consumption as high as, and were as loud as a motorcycle, so they decided not to pursue developing them.
In recent years, the rocket pack has become popular among enthusiasts, and some have built them for themselves. The pack's basic construction is rather simple, but its flying capability depends on two key parts: the gas generator, and the thrust control valve. The rocket packs being built today are largely based on the research and inventions of Wendell Moore at Bell Helicopter.
One of the largest stumbling blocks that would-be rocket pack builders have faced is the difficulty of obtaining concentrated hydrogen peroxide, which is no longer produced by many chemical companies. The few companies that produce high-concentration hydrogen peroxide only sell to large corporations or governments, forcing some amateurs and professionals to set up their own hydrogen peroxide distillation installations. High-concentration hydrogen peroxide for rocket belts was produced by Peroxide Propulsion from 2004 to 2010, but after a serious accident Peroxide Propulsion stopped making it.