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ERAST is flying high
Aerospace Projects Writer Four unique remotely-piloted aircraft being developed for high-altitude science and telecommunications missions under NASA’s Environmental Research Aircraft and Sensor Technology (ERAST) program at Dryden are seeking new flight milestones this summer. The quartet includes the piston-engined Altus II and Perseus B, the turbine-engined Proteus aircraft and the electrically powered prototype for the Helios solar-electric flying wing, formerly known as the Centurion. The Altus II, Perseus B and Helios Prototype flights are being conducted in restricted airspace over Edwards Air Force Base, while the Proteus aircraft is flown from Mojave. NASA established the ERAST program in response to growing scientific requirements for measurements at higher altitudes and longer durations than current airborne scientific platforms permit. Its goal is to develop aeronautical tech-nologies for a new breed of remotely piloted and autonomously operated uninhabited aircraft, which could operate at very high altitudes for long durations on atmospheric science missions and for commercial purposes, such as telecom-munications relays. Such "atmospheric satellites" could be built and repeatedly flown for a fraction of the cost of placing a traditional space satellite into Earth orbit. Concurrent efforts in developing, miniaturizing, and integrating sensors for science missions are also under way. ERAST project manager John Sharkey said that completion of a challenging set of milestones for the four aircraft will signal a turning point in the evolution of remotely piloted aircraft developed under the program. "By the end of this fiscal year, the Altus, Perseus and Proteus vehicles will have clearly demonstrated the capability to support operational uninhabited aerial vehicle science missions. In addition, the Centurion/Helios Prototype, using battery power, will have established the flight controls and handling qualities in support of subsequent solar-powered missions. "From this plateau of demonstrated capabilities, the emphasis within ERAST will shift toward expanding the envelope in terms of extreme altitudes, ultra-long durations and increased pay-loads." The Altus II recently resumed altitude-expansion flights out of nearby El Mirage into restricted airspace above Ed-wards, After a highly successful deployment to Hawaii this spring in support of the Atmospheric Radiation Measurement studies conducted by Sandia National Laboratories for the Department of Energy. On July 23, the dual-turbocharged Altus II flew at 55,000 feet altitude for four hours, meeting a major NASA milestone established for the aircraft. The milestone flight marked the culmination of more than four years of engine and aircraft development efforts by General Atomics Aeronautical Systems, Inc. of San Diego, Calif., builder of the Altus II. The Centurion/Helios Prototype arrived at Dryden in late July, followed by the Perseus B in Aug. 4. After several weeks of preparation, their series of flight tests are scheduled to begin in late August. Both the Perseus B and the Centurion/Helios Prototype have undergone significant upgrades and modifications since they last flew at Dryden, Perseus B in the spring of 1998 and the Centurion last fall. Designed and built by Aurora Flight Sciences of Manassas, Va., the Perseus B has been modified to increase its flight endurance and improve the operational reliability of its systems. Among upgrades incorporated by Aurora are the addition of external underwing fuel tanks and modifications to the three-stage turbocharger and engine to increase power and reduce fuel consumption, all of which will improve the aircraft’s high-altitude range and endurance. Avionics and control systems were also upgraded to provide redundancy and increase reliability, including the addition of a second Global Positioning System (GPS), a second air data pitot system, improved communications antennas and fault-tolerant flight control software to provide automatic detection and compensation for any flight sensor or actuator failure. The Perseus B is tentatively scheduled to fly three to six test flights in what is being termed an Operational Readiness Deployment at Dryden. After an initial checkout flight, one mission is targeted to reach the maximum altitude above 60,000 feet of which the Perseus B is capable while carrying a 176-pound payload. The final eight-hour mission will also be aimed toward reaching 60,000 feet but with the aircraft at maximum weight. The flight profile also calls for the Perseus B to stay above 55,000 feet altitude for four hours, meeting a major NASA ERAST milestone for the aircraft. The most noticeable modification to the Helios Prototype from its earlier incarnation as the Centurion is the addition of a fifth landing gear pod and sixth 40-foot wing section, bringing the overall wingspan of the featherweight craft to a gargantuan 247 feet. The additional section will allow for a larger array of solar cells to be installed when funding becomes available to provide adequate power for the craft to reach its design goals. Other upgrades installed by Aero-Vironment, Inc., of Simi Valley, Calif., in the Centurion/Helios Prototype include the addition of a differential GPS, an extensive turbulence monitoring system payload to record structural loads on the craft in the air and on the ground, and radiator plates to assist in cooling the avionics at high altitudes where there is little air to dissipate heat. During the initial flights, project engineers will evaluate new motor-control software, which may allow the pitch of the aircraft—the nose-up or nose-down rotation in relation to the horizon — to be controlled entirely by the motors. If successful, production versions of the Helios could eliminate the elevators on the trailing edge of the wing now used for pitch control, saving weight and increasing the area of the wing available for installation of solar cells. A two-phase flight series totaling five flights is planned for the Helios Prototype, with the first checkout and handling-qualities flight tentatively slated for Aug. 24. The first one or two flights will focus on meeting key technology requirements of the Centurion mission to reach and sustain flight at 100,000 feet, tentatively planned for the year 2001. The first phase flights will use all 14 motors and minimal ballast to save weight. The second phase will be focused on the four-day mission above 50,000 feet envisioned for the Helios, targeted to occur in 2003. For those flights, eight motors will power the prototype and more than 500 pounds of ballast will be added to simulate the weight of the energy storage system now being designed for Helios. In Mojave, Scaled Composites plans to complete refinement of an autopilot system for the Proteus prototype over the next two months, including installation and flight testing of the altitude hold/altitude change software. In addition, project officials expect to have a SATCOM (satellite communications) system fully operational which will give the Proteus an over-the-horizon command and control capability, including the ability to remotely control the aircraft from the ground via a satellite relay. Both systems are supported by the ERAST program to give the Proteus a hands-off "optionally-piloted" capability when the aircraft is on station at high altitudes. AeroVironment, Inc., General Atomics Aeronautical Systems, Aurora Flight Sciences and Scaled Composites are all members of the ERAST Alliance, a partnership established under a Joint Sponsored Research Agreement with NASA in 1994. |
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Responsible NASA Official: John Childress For questions, contact: Dryden Web Group Page Curator:WD-Team Modified: August 18, 1999 |
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