The Scaled Composites Model 281 Proteus is a tandem-wing high-altitude long-endurance aircraft designed by Burt Rutan to investigate the use of aircraft as high-altitude telecommunications relays. The Proteus is a multi-mission vehicle able to carry various payloads on a ventral pylon. The Proteus has an extremely efficient design and can orbit a point at over 19,800 m for more than 18 hours. It is currently owned by Northrop Grumman.
Design and development Proteus has an all-composite airframe with graphite-epoxy sandwich construction. Its wingspan of 77 feet 7 inches (23.65 m) is expandable to 92 feet (28 m) with removable wingtips installed. Proteus is an "optionally piloted" aircraft ordinarily flown by two pilots in a pressurized cabin. However, it also has the capability to perform its missions semi-autonomously or flown remotely from the ground. Under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project, NASA's Dryden Flight Research Center assisted Scaled Composites in developing a sophisticated station-keeping autopilot system and a satellite communications (SATCOM)-based uplink-downlink data system for Proteus' performance and payload data. The Proteus wing was adapted for use on the Model 318 White Knight carrier aircraft, which is the launch system for Rutan's Tier One spacecraft and the DARPA X-37. Flight testing of the Proteus began with its first flight on July 26, 1998, at the Mojave Airport and continued through the end of 1999. In June, Proteus was deployed internationally for the first time, debuting at the Paris Air Show. It was flown non-stop from Bangor, Maine to Paris. During the week-long show, it flew each day, demonstrating its capabilities as a telecommunications platform. The Proteus is the current holder of a number of FAI world records for altitude (class: C1-e: landplanes 3,000–6,000 kg, Group: 3, turbojet), set in cooperation with NASA Dryden. The highest altitude achieved was 63,245 feet (19,277 m) in October 2000. Proteus was included in the list of the "100 Best of 1998 Design", by Time magazine, December 21, 1998.
Operational history Due to the multimission nature of the aircraft, it has been involved in a number of significant research projects and missions. Scaled Composites, a wholly owned subsidiary of Northrop Grumman, actively markets the aircraft as a research platform, and has published a user's guide for planning proposed missions.
Angel Technologies HALO Proteus was originally conceived as a high-altitude, long operation (HALO) telecommunications platform. Proteus was to be the first of a series of aircraft built by Scaled Technology Works of Montrose, Colorado (a proposed spinoff of Scaled Composites which was later cancelled). The aircraft was intended to carry a 14-foot (4.3 m) antenna, which was flight tested in the autumn of 1999 and the summer of 2000, including the relay of a video conference while the aircraft orbited over Los Angeles. The project failed to move forward, however, and the subsequent series of aircraft were not built.
ARTIS camera A small Airborne Real-Time Imaging System (ARTIS) camera, developed by HyperSpectral Sciences, Inc., under NASA's ERAST project, was demonstrated during the summer of 1999 when it took visual and near-infrared photos from Proteus while it was flying high over the Experimental Aircraft Association's AirVenture 99 Airshow at Oshkosh, Wisconsin. The images were displayed on a computer monitor at the show only moments after they were taken.
NAST validation Proteus' first science mission was to carry the National Polar-Orbiting Operational Environmental Satellite System Airborne Sounder Testbed – Interferometer (NAST-I) instrument in March 2000 during the Cloud-Intensive Operating Period over the Department of Energy Cloud and Radiation Testbed (CART) site. The flights, based out of Stilwell, Oklahoma, encompassed 30 flight hours over a week and a half, characterizing cloud properties and validating the instrument. Then, in September and October 2000, during the Water-Vapor Intensive Operating Period, Proteus and NAST flew validation flights studying upper tropospheric water vapor and performing underflights of the Terra satellite.
ARM-FIRE AFWEX project In November–December 2000, Proteus flew as part of the DOE's Atmospheric Radiation Measurement (ARM) program and their water vapor experiments. Flights were essentially the same as was flown for the NAST Water-Vapor Intensive Operating Period validation flights.
NASA TRACE-P As part of the TRACE-P (Transport and Chemical Evolution over the Pacific) mission, Proteus once again carried the NAST pod during March 2001. The aircraft logged 126 flight hours, and was variously based out of Alaska, Hawaii and Japan, gathering data in coordination with ground, balloon and satellite sensor packages over the North Pole in March 2001.
NASA CLAMS Proteus took part in the NASA Chesapeake Lighthouse & Aircraft Measurements for Satellites (CLAMS) program in July and August 2001, flying out of NASA's Wallops Flight Facility. The project used a number of different aircraft to develop methods of measuring ocean characteristics, and estimates of aerosols.
Airborne laser target In February 2002, Proteus carried a 30-foot-long (9.1 m) pod which served as a target for development of the Boeing YAL-1 Airborne Laser system. The pod housed an array of over 2000 small holes containing optical sensors to detect the laser system. Due to scheduling constraints with other Proteus customers, the Airborne Laser never conducted an actual flight test with the Proteus target system. A target system was designed and integrated into the NKC-135 Big Crow aircraft and used for the majority of Airborne Laser testing.
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