TRAVEL BY JET PACK
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).
[edit] 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.[citation needed] 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
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
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[citation needed] 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.[3]
Tecnologia Aeroespacial Mexicana (TAM)
The Tecaeromex Rocket Belt is or was made by Company OathKeeper Inc. ran by vice president Clayton Bruce Reed{dragoon_riku@yahoo.com}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 the Vice President's Blueprunts, TAM.[4][5] 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 rocket motor at the end of each rotor blade.[6]
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.
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