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Aviation History
2004
2004-09 - 1997.PDF
TECHNOLOGY RECOVERY PETER LA FRANCHI / MELBOURNE Tether cable offers lines for research Australia backs study to explore airborne payload delivery Australia's RMIT University plans to demonstrate the use of a tether cable deployed from a fixed-wing aircraft as an airborne precision point delivery and recovery system later this year using a small-scale remotely operated aircraft as the tow platform. The research project, which is being funded by the Australian Research Council and supported by the Australian Defence Science and Technology Organisation, is exploring the potential use of teth ers for airborne payload delivery roles. The technology may also have potential application as an insertion and recovery system for Special Forces personnel, or in search and rescue missions. The concept is based on the pro gressive letting out of a multi-kilo metre length cable from a fixed- wing aircraft that is flying a con stant speed orbit above a ground target. As the tether descends, its tail is able to be steered in space by variations to the aircraft flightpath and speed. RMIT researchers believe suffi cient control can be exercised over the position of the tether end such that it can be brought into a stable hovering position less than 1.5ft (0.5m) above the ground while the launch aircraft is orbiting several thousand feet overhead. Related orbiting and tether con trol techniques are already used by US Navy Northrop Grumman E-6A TACAMO aircraft to deploy 8,000m- long airborne communications antennas into a near vertical profile. RMIT has developed an auto matic tether controller as part of its research programme. That system uses fuzzy logic processing algo rithms to translate movements in the cable end position in space into corresponding changes in the car riage aircraft flightpath. Computer simulations carried out by RMIT indicate a 3,000m tether, carrying a 25kg (551b) pay- load, would take about 600s to reach the ground after deployment. However, the simulations also indicate that the deployed tether effectively acts as a spring, and once the payload is released, the cable snaps back into the air. There is also a potential for the tether control sys tem to respond to the spring action by unwinding additional cable, causing the end of the tether to then strike the ground, delaying the start of recovery by around 150s. RMIT researchers say they are exploring options for a more-effi cient response by their prototype tether-control system to overcome this issue, with this to be investi gated further in the subscale flight demonstration. The option of tem porarily fixing the end of the tether to the ground during the unload- load phase of a mission is also being considered. AIRBORNE PRECISION P 7 6 5 4 E * 3 2 1 0 OVERY CONCEPT Test aircraft small-scale UAV Multi-kilometre length cable C - 25kg payload Tether end of cable can be controlled to maintain a hover position less than half a metre above the ground EUGHT ENDURANCE PETER LA FRANCHI / CHICAGO NASA aims high and long for next UAVs NASA plans to develop and fly at least four different configurations of high-altitude, long-endurance (HALE) unmanned air vehicle by 2018, including an airship derivative, under a new HALE technology research programme which replaces the former ERAST Earth sciences effort. The new programme includes plans for demonstrations of an "eternal" aircraft in 2014, designated Global Flyer In the near term, the new programme will include a series of flight oper ations by the Aerovironment Pathfinder Plus HALE UAV That UAV has been undergoing refurbishment and is expected to return to flight status this month. The first series of Pathfinder-Plus flights will explore the impact of light air turbulence on span lifter airframes. Turbulence-induced stress was a key cause of the June 2003 crash of the Aerovironment Helios HALE UAV demonstrator NASA released its final report on that accident last month. The first new air vehicle under the HALE roadmap, designated the Sub Orbital Long Endurance Observer (SOLEO), is planned to have an endurance of seven to 14 days. First flight is proposed for 2010, with the air vehicle to be powered by either a hydrogen fuel cell or an internal com bustion engine using liquid hydrogen as fuel. SOLEO would have a 180kg (400lb) payload capacity and is intended to continue exploring commercial and scientific missions similar to those examined under EFtAST These include hurricane monitoring, disaster relief and commercial telecommunications technology demonstrations. The second proposed UAV is the Global Observer, to fly in 2012 and demonstrate endurance missions of more than 30 days. The air vehicle concept is similar to Helios, with this including use of a propulsion system powered by a combined solar and fuel cell. Both SOLEO and Global Observer would have a ceiling of around 60,000ft (18,300m), but would be restricted to flight operations 45° north or south of the equator. The Global Flyer is intended to refine design concepts developed through SOLEO and Global Observer, but be capable of operating any where on Earth for unlimited periods. The airship option is being proposed as a solution for the final phase of the programme, the demonstration of a heavylifter eternal aircraft capability by 2018. COLLISION AVOIDANCE Ground-based autopilot could steer small unmanned vehicles NASA's UAV applications centre is developing a ground-based autopilot system to provide local-area deconfliction for small unmanned air vehicles operating in non-segregated airspace. NASA sees the approach as a means of overcoming practical limi tations on fitting sense and avoid hardware to small UAVs, particularly air vehicles operating in low-altitude, long-endurance (LALE) flight profiles over urban areas. The autopilot system comprises a ground-mounted Lockheed Martin LSDIS portable radar with track data integrated into the UAV navigation plot and mission control system. Fusion of the radar track data with the air vehicle autopilot system is intended to facili tate automatic deconf lictions as well as enhanced operator situational awareness. The LSDIS radar is a two-dimensional system derived from the Lockheed Martin PSTAR system and has a maxi mum range of 20km (11nm). NASA has demonstrated the system in two sets of trials in California during the past year and plans a further trial in April 2005 as part of a demonstration of using a LALE UAV to perform night time frost damage monitoring of vineyards in southern California. 30 12-18 OCTOBER 2004 FLIGHT INTERNATIONAL www.fliqhtinternational.com
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