If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Jet pack
https://en.wikipedia.org/wiki/Jet_pack
A jet pack, rocket belt or rocket pack is a device, usually worn on the back, which uses jets of gas (or in some cases liquid) to propel the wearer through the air. The concept emerged from science fiction in the 1960s and became popular as the technology became a reality. The most common use of the jet pack has been in extra-vehicular activities for astronauts. Despite decades of advancement in the technology, many obstacles remain in the way of use of the jetpack in the military or as a means of personal transport, including the challenges of Earth's atmosphere, Earth's gravity, low energy density of available fuels, and the human body not being naturally adapted to fly. To compensate for the limitations of the human body, the jet pack must accommodate for all factors of flight such as lift and stabilization. Andreyev: oxygen-and-methane, with wings The first jet pack was developed in 1919 by the Russian inventor Aleksandr Fyodorovich Andreyev. 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 (likeliest a rocket) with wings each roughly 1 m (3 feet) long. Hydrogen peroxide-powered rocket packs A hydrogen peroxide-powered engine 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 a catalyst (for example, silver) 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 (about 2,500 kJ/kg [5,800 BTU/lb]), forming in this case a steam-gas mixture at 740 °C [1,360 °F]. 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 fairly lightweight 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 (because of the limited amount of fuel the user can carry unassisted). 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. Current technology At the TechCrunch Disrupt conference in 2014, Astro Teller, head of Google X (Google's research laboratory), said they investigated jetpacks but found them too inefficient to be practical, with fuel consumption as high as 940 L/100 km (1/4 mpg-US), 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 (Gothenburg, Sweden) from 2004 to 2010, but after a serious accident Peroxide Propulsion stopped making it. Yves Rossy's jet wingpack Swiss ex-military and commercial pilot Yves Rossy developed and built a winged pack with rigid aeroplane-type carbon-fiber wings spanning about 2.4 m (8 ft) and four small kerosene-burning Jetcat P400 jet engines underneath; these engines are large versions of a type designed for model aeroplanes.[19] He wears a heat-resistant suit similar to that of a firefighter or racing driver to protect him from the hot jet exhaust.[20][21] Similarly, to further protect the wearer, the engines are modified by adding a carbon fibre heat shield extending the jet nozzle around the exhaust tail. 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 their midpoint. 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 then can fly horizontally for several minutes, landing with the help of a parachute.[22] He achieves true controlled flight using his body and a hand throttle to maneuver; jet wingsuits use small turbojets, but differ from other aircraft in that the fuselage and flight control surfaces consist of a human. 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 300 km/h (190 mph) during the crossing,[34] and was 200 km/h (120 mph) when he deployed the parachute. Since then he has—in several flights—managed to fly in a formation with three military jets and cross the Grand Canyon, but he failed to fly across the Strait of Gibraltar—he made an emergency landing in the water. * |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Jet Pack | [email protected] | Home Built | 0 | March 11th 10 09:50 AM |
jet pack | [email protected] | Home Built | 31 | August 11th 08 10:43 PM |
P-61 belly gun pack | Dave Kearton | Aviation Photos | 0 | March 2nd 07 09:19 AM |
Jet pack | Bob C | Soaring | 14 | January 12th 06 07:11 PM |
Jet pack | Bob C | Soaring | 0 | January 10th 06 07:21 AM |