Sunday, 26 August 2012

Personnel flight, flying without airplanes

Looking at todays films of superheroes, particularly the fictional character Iron man, I wonder if it is possible to use technology to strap on a device to lift you in the air and allow a sustained flight across long distances. Despite Iron-man's use of a fictional power source from his chest, there are current technologies that could in theory allow the operator to fly.

During World War II, Germany conducted late-war experiments by 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 (more popularly known as the V-1 or buzz bomb), though the size was much smaller. As such, the device had to be for short duration “jumps” of ranges up to 50-70 meters. This was not meant to be a individual flying machine to achieve any sort of altitude or long flight journey, so emphasis was placed on finding a suitable type of propulsion to accomplish the limited jump range.

The Schmidt pulse jet seemed ideal for this, but since a pulse jet cannot operate without forward airspeed, the units involved were adapted and force-fed oxygen by a separate oxygen tank. Paul Schmidt patented his pulse jet design in 1931 the unit utilized the pulse jet design. These Schmidt pulse jets were small pulse tubes able to be carried by one man.. The apparatus involved strapping on two Schmidt pulse tubes - one on the back for forward flight and a smaller, less powerful unit carried ventrally for simple control with hand grips for steering. Both pulse tubes had to be ignited at the same time to enable proper jumps. The units consumed 100 grams of fuel per second. Flight duration was minimal and both units had to be turned off immediately upon landing.
Aerojet General company in 1959 to research the possibility of designing a Small rocket lift device 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 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 SLRD "Small Rocket Lift Device".

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 a 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., accompanied by the 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 fed directly to one or more jet nozzles. Currently, such rocket belts can only fly for about 30 seconds (because of the limited amount of fuel the user can carry unassisted).

In the figure the hydrogen peroxide cylinders and compressed nitrogen cylinder are designated (pressure c. 40 atm or 4 MPa). The pilot turns the engine thrust control handle, and opens the regulator valve (3). Compressed nitrogen (1) displaces liquid peroxide of hydrogen (2), which on the tubes enters the gas generator (4). There it contacts the catalyst (thin silver plates, covered with a layer of samarium nitrate) and is decomposed. The resulting hot high-pressure mixture of steam and gas enters two pipes, which emerge from the gas generator. These pipes are covered with a layer of heat insulator to reduce loss of heat. Then the hot gas enters the jet nozzles (De Laval nozzles), where first they are accelerated, and then expand, acquiring supersonic speed and creating reactive thrust. The whole construction is simple and reliable; the rocket engine has no moving parts.

Recently Yves Rossy , inventor and aviation enthusiast, was the first person to achieve sustained human flight using a jet-powered fixed wing strapped to his back. This jet pack has led to his being nicknamed Airman, Jetman, Rocketman and, later, Fusionman.

Rossy developed and built a system comprising a back pack with semi-rigid aeroplane-type carbon-fiber wings with a span of about 2.4 metres (7.9 ft), powered by four attached Jet-Cat P200 jet engines modified from large-model, kerosene fueled, aircraft engines. His first flight was in November 2006 in Bex, lasting nearly six minutes and nine seconds. Rossy later successfully flew across the English Channel on 26 September 2008 in 9 minutes 7 seconds, reaching a speed of 299 km/h (186 mph) during the crossing. Later in 2008, he made a flight over the Alps, reaching a top descent speed of 304 km/h (189 mph) and an average speed of 124 mph.
On 5 November 2010, he flew a new version of his jet-powered flight system and successfully performed two aerial loops before landing via parachute. He launched from a hot air balloon piloted by Brian Jones at 2,400 meters (7,900 feet) and flew a total of 18 minutes before landing. The wingspan of Rossy's latest craft had been reduced to 2 m. On 7 May 2011, Rossy flew across the Grand Canyon in Arizona, after the United States Federal Aviation Administration classified his flight system as an aircraft, waived the normal 25 to 40 hours of flight testing time, and granted him permission to perform the flight.
There are other devices like the Martin jetpack which the operator straps on a large unit  similar to a vertical take of  engine with two ducted fans. Theoretically it could reach speeds unto 60-mph and rise to 8000 feet. Although its range is 31 miles with a price about $100,000, this device can take off and land and has the ability to fly at distance. Despite its cumbersome size the Martin jet-pack seems more like a miniature vehicle then a jet pack. My personnel preference would be Yves Rossy's design which uses 4 miniature model jets at a rough price of £2000 with a thrust of 100 Newtons or 10 kg per engine. Despite the jet wing not being able to vertically take off and land, Rossy simply uses a airplane at a safe height and lands with a parachute.
Perhaps one day someone might incorporate a two stage system which allow the vertical take off and land similar to the Bell rocket-belt and a miniature jet wing design  that Yvess Rossy invented, allowing the operator to take off and fly at distance and land safely on the other side.

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