Jet pack

This article is about the jet or rocket powered flying device. For other uses, see Jetpack (disambiguation).

Rocket Belt pilot Dan Schlund at the 2005 Melbourne Show

Rocket Belt pilot Dan Schlund at the 2007 Rose Parade

Jet pack, rocket belt, rocket pack, and similar names, are various types of device, usually worn on the back, that use jets of escaping gases (or in some cases liquid water) to allow a single user to fly.

The concept of these devices emerged from science fiction in the 1920s and popularised in the 1960s as the technology became a reality. Currently, the only practical use of the jet pack has been extra-vehicular activity for astronauts. Despite decades of advancement in the technology, the challenges of Earth's atmosphere, Earth's gravity, and the human body (which is not well suited for this type of flight) remain an obstacle to its potential use in the military and as a means of personal transport.

History

The German Himmelstürmer of World War II

During World War II, Germany made late-war experiments of strapping two wearable shortened Schmidt pulse jet tubes of low thrust to the body of a pilot. The working principle was the same as the Argus As 014 pulse jet that powered the Fieseler Fi 103 flying bomb, though the size was much smaller.

The device was called "Himmelstürmer" (Skystormer) and operated as follows: when the flier ignited both engines simultaneously the tubes began to pulse modulate. The angled rear tube strapped to the flier's back provided both lift and forward thrust while the chest mounted deflector tube of lower thrust maintained a constant upward thrust. This lifted the flier up and forward. By opening the throttle to the rear tube, calculated "jumps" could be made of up to 60 meters (180 ft) at low altitude (under 50 ft, 15 m). The tubes consumed very little fuel but not much could be carried either.

The intended use for this device was for German engineer units to cross minefields, barbed wire obstacles, and bridgeless waters. The device was never intended for troop use, despite the imaginative depiction of it in that role in the comic book and film The Rocketeer (which was a prop bearing no resemblance to the real device).

At the end of the war this device was handed over to Bell Aerosystems which tested it on a tether out of fear of harm as no test flier was willing to risk his life with the German machine. What became of the device is not known.

The fictional device used by The Rocketeer was a rocket pack that was technically unique (at least in the film adaptation) because it was designed to remain cool. The Himmelstürmer, by comparison, never operated long enough to get extremely hot and both tubes were angled away from the body of the flier. In operation the thrust difference between pulse tubes acted as a push/pull/lift system. Flight time for jumps was in seconds with no lengthy descent time as altitude was minimal. As soon as the throttle was disengaged the device was shut off, a very simple operation and there was no report of any casualties.

The Jump Belt (mostly compressed gas powered)

In 1958, Garry Burdett and Alexander Bohr, engineers of Thiokol Corporation created the "Jump Belt", which they named Project Grasshopper. Thrust was created by high-pressure compressed nitrogen. On the "belt" were fixed two small nozzles, directed vertically downward. The wearer of the "belt" could open a valve, letting out from the nitrogen gas cylinder through the nozzles, in this case it was tossed upward to the height of 7 meters. After leaning forward, it was possible with the aid of the "jump belt's" thrust to run at 45 to 50 km/h. Then Burdett and Bohr tested a hydrogen peroxide powered version. The "jump belt" was demonstrated by a serviceman in action, but there was no financing, and the matter again did not go to further tests.

The small size of the canisters is likely the reason why the name "-belt" rather than "-pack" became customary in the USA.

Aeropack

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

In 1960, Bell Rocketbelt was presented to the public. The jet of gas was provided by a hydrogen peroxide powered rocket but the jet can also be provided by a turbojet engine, a ducted fan, or other kinds of rockets powered by solid fuel, liquid fuel or compressed gas (usually nitrogen).

Development continues

American servicemen did not lose interest in this type of flight vehicle. Control of transport studies of the U.S. Army Transportation Research Command (TRECOM) assumed that personal jet apparatuses could find the most diverse uses: for reconnaissance, crossing rivers, amphibious landing, access to steep mountain slopes, overcoming minefields, tactical manoeuvring, etc. The concept was named Small Rocket Lift Device, SRLD.

Within the framework of this concept the administration in 1959 concluded with the company Aerojet General a big contract to research on 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 Moore of the company Bell Aerosystems 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 send an order for Bell Aerosystems to develop an SLRD. Wendell Moore was appointed as the chief project engineer.

Hydrogen peroxide powered rocketpacks

A hydrogen peroxide-powered motor is based on the decomposition reaction of hydrogen peroxide. Nearly pure (90% in the Bell Rocket Belt) hydrogen peroxide is used. Pure hydrogen peroxide is relatively stable, but in contact with the catalyst (for example, silver) it decomposes into a mixture of superheated steam and oxygen in less than 1/10 millisecond increasing in volume 5000 times: 2 H₂O₂ → 2 H₂O + O₂. The reaction is exothermic, i.e. with liberation of much heat (about 2500 kJ/kg), forming in this case a steam-gas mixture at 740 °C. This hot gas is used exclusively as the reaction mass and is directly led 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 fairly lightweight rockets, but the jet has a reasonably low exhaust velocity and hence a poor specific impulse. Currently, such rocket belts (limited to the amount of fuel the user can carry unassisted) 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 motor 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 of the construction of Wendell Moore can be prepared in workshop conditions but needs 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 (a maximum of around 30 seconds).
• 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 very spectacular public demonstration flights i.e. stunts. Due to their strong visual impact, rocket pack flights are guaranteed to seize the attention of spectators. As a result, rocket pack flights enjoy great success at major sporting events. For example, a flight was arranged in the course of the opening ceremony of the summer Olympic Games 1984 in Los Angeles, USA

Bell Textron Rocket Belt

Main article: Bell Rocket Belt

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. See Bell Rocket Belt#RB2000 Rocket Belt.

Bell Pogo

Main article: Bell Pogo

The Bell Pogo was a small rocket-powered platform that 2 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, is the first company to manufacture the 30 second flying Rocketbelt and performed Rocketbelt performances exclusively since 1983, including the 1984 Summer Olympics, Carnival in Rio de Janerio, Super Bowls, the Rose Parade and Daytona 500, Michael Jackson and many T.V shows including Walker Texas Ranger and NCIS. Powerhouse Rocketbelt pilots include stuntman Kinnie Gibson and Dan Schlund.

Tecnologia Aeroespacial Mexicana (TAM)

The Tecaeromex Rocket Belt is or was made by Tecnologia Aeroespacial Mexicana, which is said to be made by the only company in the world that offers a flying and tested rocket belt package, featured in the March 2006 issue of Popular Science magazine and many TV programs around the world like the Discovery Channel, the BBC, ProSieben, TV Azteca, The Science Channel, The History Channel. Its maker claims that four of his rocketpacks are flying now; his first tethered flights were on 22 September 2005.

On August 11, 2006, the inventor's daughter Isabel Lozano was the first woman in the world to fly tethered in a rocket belt in front of millions of TV spectators; she flew with a special rocket belt built by TAM. It runs on hydrogen peroxide. It sells for USA $125,000 including a training course in using it.

TAM also made a backpack helicopter called Libellula, with a 2-bladed rotor driven by a small motor at the end of each rotor blade.

Jetpack International

Jetpack International made 3 types of jet packs. They do not have wings:

Name	Max flight time	Max distance	Max speed	Max height	Max pilot weight	Fuel	Motor type	Fuel capacity	Price
Jet pack H202	33 seconds	500 ft	70 mph	120 ft	180 lbs	H2O2	rocket	5.8 gallons	Not for sale
Jet pack H202-Z	43 seconds	1500 ft	77 mph	250 ft	180 lbs	H2O2	rocket	8 gallons	Not for sale
Jet pack T-73	~9 minutes	c. 11 miles	~83 mph	~250 ft	180 lbs.	Jet-A fuel	T-73 jet motor	5 gallons	$200,000 incl. training

A Jet Pack H202 was flown for 34 seconds in Central Park on the 9 April 2007 episode of the Today Show, and sold for $150,000. As of January 2009 their H202 jet packs are for demonstration only, not for sale.

Turbojet pack

Turbojets

Packs with the turbojet engine work on the traditional kerosene. They have higher efficiency, greater height and a duration of flight of many minutes, but they are complex in construction and very expensive. Only one working model of this pack was made; it underwent flight tests in the 1960s and at present it no longer flies.

Bell Jet Flying Belt

In 1965 Bell Aerosystems concluded a new contract with the Defense Advanced Research Projects Agency (DARPA) to develop a jet pack with a turbojet engine. This project was called the "Jet Flying Belt", or simply the "Jet Belt". Wendell Moore and John K. Hulbert, a specialist in gas turbines, worked to design a new turbojet pack. Williams Research Corporation (now Williams International) in Walled Lake, Michigan, designed and built a new turbojet engine to Bell's specifications in 1969. It was called the WR19, with a rated thrust of 195 kgf (1,910 newtons) and weighing 31 kg.

The first free flight of the "Jet Belt" took place on 7 April 1969 at the Niagara Falls Municipal Airport. Pilot Robert Courter flew about 100 meters in a circle at an altitude of 7 meters, reaching a speed of 45 km/h. The following flights were longer, up to 5 minutes. Theoretically, this new pack could fly for 25 minutes and go up to 135 km/h.

In spite of successful tests, the U.S. Army lost interest. The pack was complex to maintain and too heavy. Landing with its weight on his back was hazardous to the pilot, and catastrophic loss of a turbine blade could have been lethal.

Thus, the "Bell Jet Flying Belt" remained an experimental model. On 29 May 1969, Wendell Moore died of complications from a heart attack he had suffered six months earlier, and work on the turbojet pack was ended. Bell sold the sole version of the "Bell pack", together with the patents and the technical documentation, to Williams Research Corporation. This pack is now in the Williams International company museum. A version of this engine went on to power the later US Tomahawk cruise missiles.

Special features of the turbojet pack

The "Jet Belt" used a small turbofan engine, which was mounted vertically, with its air intake downward. Intake air was divided into two flows. One flow went into the combustion chamber, the other flow bypassed the engine, then mixed with the hot turbine gases, cooling them and protecting the pilot from the high temperature. In the upper part of the engine the exhaust was divided and entered two pipes, which led to jet nozzles. The construction of the nozzles made it possible to move the jet to any side. Kerosene fuel was in tanks beside the engine. Control of the turbojet pack was similar the rocket pack, but the pilot could not tilt the entire engine. Maneuvering was by deflecting the controlled nozzles. By inclining levers, the pilot could move the jets of both nozzles forward, back, or sideways. The pilot rotated left/right by the turning the left handle. The right handle governed the engine thrust. The jet engine was started with the aid of a powder cartridge. While testing this starter, a mobile starter on a special cart was used. There were instruments to control the power of the engine, and a portable radio to connect and transmit telemetry data to ground-based engineers. On top of the pack was a standard auxiliary landing parachute; it was effective only when opened higher than 20 meters. This engine went on to become the basis for the early cruise missile propulsion unit.

In space

Bruce McCandless II operating the Manned Maneuvering Unit

Rocket packs can be useful for extra-vehicular activity (EVA) in outer space. While near Earth a jet pack has to produce a g-force of at least 1g (otherwise it just provides some steering capacity while falling down), for excursions outside a free falling spaceship even a small g-force, for a small deviation from free fall, is already sufficient, hence much less delta-v is consumed per unit time, and not during the whole EVA. With only small amounts of thrust needed, safety and temperature are much more manageable than in Earth gravity in the atmosphere.

Rocket packs were tested during mission STS-64. Mission Specialists Carl Meade and Mark Lee tested the SAFER Rocket Pack while Hammond remained inside the Orbiter.

NASA's Manned Maneuvering Unit (MMU) (compressed gas powered)

In the 1980s, NASA demonstrated the Manned Maneuvering Unit (MMU), a rocket pack that allowed an astronaut to function as his/her own spacecraft, but the system was retired before the decade was gone. The MMU is the only jet pack of practical importance. Its operational area is outside a space station or spacecraft, where an astronaut can limitedly move independently. The MMU's propulsion was produced by high-pressure nitrogen gas discharged through nozzles (which the MMU has 24 of). The MMU was used since 1984 in three Space Shuttle missions (STS-41-B, STS-41-C and STS-51-A).

NASA's SAFER

Recently, NASA has introduced the SAFER, a smaller, simpler version of the MMU meant to be used in case of accidental separation from spacecraft or station.

Winged jet and rocket packs

Artist's depiction of a jetpack with folding wings

Jet packs and rocket packs would likely have much better flight time on a tankful of fuel if they had wings. There have been occasional real cases of a man gliding horizontally long distances with his body horizontal and no flying aid except a pair of rigid airplane-type wings strapped directly to his body; see also wingsuits.

Visa Parviainen's jet-assisted wingsuit

On 25 October 2005 in Lahti in Finland, Visa Parviainen jumped from a hot air balloon in a wingsuit with two small turbojet jet engines attached to his feet. The turbojets provided approximately 16 kgf (160 N, 35 lbf) of thrust each and ran on kerosene (Jet A-1) fuel. Visa apparently achieved approximately 30 seconds of horizontal flight with no noticeable loss of altitude.

Yves Rossy's jet wingpack

Rossy's wing showing the four purple and silver jet-engines mounted close to the centre

Swiss ex-military and commercial pilot Yves Rossy developed and built a winged pack with rigid aeroplane-type carbon-fiber wings spanning about 8 feet (2.4 m) and four small kerosene-burning jet engines underneath; these engines are large versions of a type designed for model aeroplanes. He wears a heat-resistant suit similar to that of a firefighter or racing driver to protect him from the hot jet exhaust. Similarly, the engines are modified with the addition of a carbon fibre heat shield extending the jet nozzle around the exhaust tail, to further protect the wearer.

Rossy claims to be "the first person to gain altitude and maintain a stable horizontal flight thanks to aerodynamic carbon foldable wings," which are folded by hinges at the midpoint of each wing. After being lifted to altitude by a plane, he ignites the engines just before he exits the plane with the wings folded. The wings unfold while in free-fall, and he is then able to fly horizontally for several minutes, landing using a parachute. He achieves true controlled flight using his body and a hand throttle to maneuver.

The system is said by Rossy to be highly responsive and reactive in flight, to the point where he needs to closely control his head, arm and leg movements in order not to enter an uncontrolled spin. The engines on the wing require the achievement of a precise common alignment during set-up, in order to also prevent instability. An electronic starter system ensures all four engines ignite simultaneously. In the event of a spin, the wing unit can be detached from the pilot, and both pilot and wing unit descend to Earth on separated parachutes.

Rossy's jet pack was exhibited on 18 April 2008 at the opening day of the 35th Exhibition of Inventions at Geneva. Rossy and his sponsors spent over $190,000 to build the device.

Flights

His first successful trial was on 24 June 2004 near Geneva, Switzerland. Rossy has made more than 30 powered flights since. In November 2006 he flew with a later version of his jet pack.

On May 14, 2008 he made a successful 6-minute flight from the town of Bex near Lake Geneva. He exited a Pilatus Porter at 7,500 feet with his jet pack. It was the first public demonstration before the world's press. He made effortless loops from one side of the Rhone valley to the other and rose 2,600 feet.

It has been claimed that the military has been impressed and asked for prototypes for the powered wings, and that Rossy kindly refused the request and stated it is only for aviation enthusiasm purposes.

On 26 September 2008, Yves successfully flew across the English Channel from Calais, France to Dover, England in 9 minutes, 7 seconds. His speed reached 186 mph during the crossing, and was at 125 mph when he deployed the parachute.

Current technology

According to the US Government, real jetpacks have little practical value due to the limitations of current technology. The United States armed forces, which conducted most jet pack research, has declared that helicopters are far more practical. Many others have worked on devising a functional jet pack, but with limited success.

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 make their own hydrogen peroxide distillation installations. High concentrated hydrogen peroxide for rocket belts has been available from Peroxide Propulsion, Gothenburg, Sweden since 2005.

Two high-profile jet pack projects are currently being operated:

• Jetpack International
• Tecnologia Aeroespacial Mexicana

Water jet pack

A water-propelled jet pack, the Jetlev-Flyer, debuted in January 2009, as a recreational toy. Invented by Raymond Li of Newfoundland, Canada, it uses two water jets for thrust instead of gas jets. A small unmanned boat with a pump delivers pressurized water to the jet pack via a hose, so the Jetlev-Flyer is designed to be used over a body of water, and the water provides a safety cushion in case of a fall. Since the engine, pump, fuel and other systems are supported by buoyancy and dynamic lift of the water, high agility and thrust-to-weight ratios can be achieved. Height is regulated by the weight of the water-filled hose and is thus very stable. Pitch and roll stability is inherent in the design of the jetpack and the water hose assembly. Directional stability is greatly enhanced by the drag of the boat. Duration of up to two hours and range of 50-60 miles are possible, depending on pilot weight and skills. Most landings are soft landings in the water, although a technique for a low level landing approach and landing on docks or platforms is possible with proper training. A special training system with remote helmet radio and remote throttle control by the coach is mandatory, and owners must qualify as certified instructor with a one-day training program. Basic Jetlev flight can be learned in 10-15 minutes on the water on average, and in as little as two minutes.

In popular culture

A jet pack wearing hero on the cover of Amazing Stories, August 1928. The cover illustrates The Skylark of Space.

The concept of jet packs appeared in popular culture, particularly science fiction long before the technology became practical. Perhaps the first appearance was in pulp magazines. The 1928 cover of Amazing Stories featured a man flying with a jet pack. While several science fiction novels from the 1950s featured jet packs, it was not until the "Bell Rocket Belt" in the 1960s that the jet pack reached the imagination of the mainstream. Bell's demonstration flights in the U.S. and other countries created significant public enthusiasm.

The JetPack appeared in the James Bond movie Thunderball when 007 played by Sean Connery used a Jetpack in the pre-title sequence to escape the bad guys and rendezvous with a French Woman.

A Bell Rocket Belt was featured extensively in the 1976 CBS Saturday morning children's live action TV show Ark II.

A rocket pack flight occurred famously on the opening of the summer Olympic Games in Los Angeles in 1984. The pack was piloted by both Bill Suitor and Gordon Yaeger. Suitor was a legendary personality (in all calculation more than 1200 flights — more than in any other pilot to this day). Bill took off from platforms, flew above many spectators, who from the unexpected contingency covered their heads with their hands, and landed opposite the presidential platform, where Ronald Reagan sat. This flight was seen by 100,000 spectators on the platforms and about 2.5 billion television viewers.

The JetPack stock footage appeared in the television series Lost in Space several times.

A jet pack also appears in the final scenes of the 2010 movie Kick-Ass (film). In the movie, dual Gatling guns have been mounted to the jet pack to enable the lead character to gain access to a gangster's lair located at the top of a New York City skyscraper.

Home-made versions

Episode 32 of MythBusters investigates the urban legend of an affordable jet pack or rocket pack that can be built from plans purchased on the Internet. Extensive modifications were made by the MythBusters team due to vagueness in the plans, and the infeasible engine mounting system specified. The jet pack produced by the MythBusters had two ducted fans powered by ultralight-type engines. They found it was not powerful enough to lift a person off the ground, and was expensive to build. The plans specified a Rotax 503 ultralight engine, but they intended to use the more powerful and lighter Rotax 583 engine before a similar lighter unnamed engine was substituted.

America's only "private rocketeer", Gerard Martowlis, built a fully operational rocket pack. Like all flying packs, his is extraordinarily difficult and extremely dangerous to fly, taking many hours to learn and practice. He performed his recent test flights using a safety tether system in case he lost control. A consequence of the short flight time of any peroxide-based pack is that the entire flight is below the minimum parachute altitude. Accordingly, any loss of control or failure of the pack is most likely fatal. The training also incurs expensive fuel costs.

See also

• Backpack helicopter
• List of personal aircraft

External links

• Rocket Belt. Peter Guisbert's site, dedicated to the history of rocket pack. Enormous quantity of information and photographs.
• 3 News New Zealand about The Martin Jetpack being considered for a tourism venture.
• Flying into the Future: Ky Michaelson's Jet pack site
• Popular Mechanics comparison of the TAM Rocket Belt and Jetpack International's Jet Pack H202
• Rocket Man Short documentary on Gerard Martowlis, an aspiring rocketeer.
• Gerard Martowlis's rocket pack