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Aviation History
2002
2002 - 3163.PDF
TECHNOLOGY CERAMICS GRAHAM WARWICK / WASHINGTON DC P&W turns up the heat for engine experiment US company to demonstrate high-pressure turbine that can cope with high temperatures Pratt & Whitney is to develop a ceramic high-pressure turbine under a US Army programme to demonstrate technology for an unmanned air vehicle (UAV) engine. The army's Aviation Applied Technology Directorate plans to demonstrate the 370kW (500shp) heavy-fuel engine by 2007, aimed initially at the A160 Hummingbird rotary-wing long- endurance UAV, but with growth to power the planned Unmanned Combat Armed Rotorcraft (UCAR). Under a 39-month, $2 million cost-sharing contract, P&W and the United Technologies Research Center (UTRC) intend to demon strate a ceramic turbine that can operate at high rotor-inlet tempera tures without cooling. The team plans to employ ceramic technol ogy used in automotive super chargers to produce a durable inte grally bladed rotor. The targets of a 20% reduction in specific fuel consumption and a 50% improvement in power-to- weight ratio for the engine require higher temperatures that cannot be reached with metallic technology, says ceramic turbine programme Ceramic turbines could improve power-to-weight ratio and fuel consumption manager Aavo Anto, because the blades are too small to be cooled. The turbine is 180-200mm (7-8in) in diameter, with blades less than 15mm long. The programme will use a silicon nitride material developed for the automotive industry to produce the monolithic ceramic turbine. P&W and UTRC will also demonstrate barrier coatings to protect the tur bine from moisture and erosion as well as a proprietary way to attach the ceramic rotor to a metallic shaft, says Kevin Farrell, general manager small military engine programmes. Rig tests are planned for 2005. The technology could also be applied to gas turbines in the 225-595kW range used as vehicle engines or ground power units, says Farrell. Programme goals include a 35% reduction in production and operating and sup port costs relative to comparable engines available today. PROPULSION Boeing leads nuclear team NASA has contracted a Boeing- led team to develop power- conversion technologies for future nuclear electric reactor propulsion systems for deep space exploration. The team includes NASA's Jet Propulsion Laboratory and Glenn Research Center, Honeywell, Swales Aerospace and universi ties Auburn and Texas A&M. The team will produce a conceptual design and development plan for a high-yield technology advanced system based on the Brayton Power Conversion System. MICRO AIR VEHICLE Wasp flies to record AeroVironment has set an en durance record for hand-launched micro air vehicles (MAV), achieving a flight of lh 47min thanks to a design that combines the batteries with the structure. California-based AeroViron- ment's Wasp MAV has been devel oped under the US Defense Ad vanced Research Projects Agency's (DARPA) synthetic multifunctional materials programme. The design replaces separate bat tery and structure components with a material system that sup plies electrical energy for propul sion while carrying wing loads. The Wasp is a radio-controlled flying- wing MAV with a span of 330mm (13in) and a combined wing struc ture/battery pack weighing 120g (0.261b). The total vehicle weight amounts to 170g. The vehicle uses rechargeable lithium-ion batteries and the energy density of the wing struc ture-battery is 143W/kg, with an average power output during flight of over 9W, says DARPA. The next-generation Wasp, which is under development, will incorporate a simple autopilot and be able to carry a colour video camera payload. DEMONSTRATION UAV helps coffee crop NASA has completed a remote- sensing demonstration using the AeroVironment Pathfinder-Plus solar-powered unmanned air vehicle (UAV). The mission pro duced digital images of a coffee plantation in Hawaii to help growers select the ripest field. Dr Stan Herwitz, principal investigator for the UAV Coffee Project, says: "During the flight we assembled clear-sky images, even though the plantation was never completely cloud-free." The mission involved flying in civil air space. "The UAV was treated like any conventionally piloted aircraft by air traffic controllers," he says. The 11.5h mission on 30 September involved a 4h flight at 20kt(37km/h) and 21,000ft (6,400m) over the Kauai coffee plantation, with the Pathfinder- Plus downlinking more than 300 high-resolution digital images. Using a combination of pre planned flight lines and spontaneous remotely controlled manoeuvres to guide the UAV to cloud-free areas, the team was able to produce a mosaic image of the plantation showing the rel ative ripeness of the coffee field. "It would not have been as exciting had it been a clear sky," says Herwitz, highlighting the "mobile satellite" capability of the long-endurance UAV INVENTUS FLIES Las Vegas-based Lew Aerospace has flown the Inventus S-1 unmanned air vehi cle, a low-cost flying wing design intended for commercial and government use. The $269,000 vehicle has a maximum loiter time of 30h, 3,200km (1,730nm) range, 10,000ft (3,050m) alti tude, 122kt (225km/h) speed and 22.7kg (50lb) payload. The 3.2m-span S-1 is powered by a two-stroke engine. Lew says the S-1 performed flawlessly during its almost 18min first flight, with it reaching 500ft. www.flightinternational.com FLIGHT INTERNATIONAL 29 OCTOBER - 4 NOVEMBER 2002 31
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