The Perseus B remotely piloted vehicle (RPV) has achieved a record altitude for a single-engine, propeller-driven airplane of 60,260 ft (18,367 m) on June 27, 1998. The Perseus B is one of the test-bed aircraft developed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program for use in conducting high-altitude, long-duration missions carrying atmospheric sampling and sensing payloads for the scientific community within NASA and other agencies.

The Perseus B (see figure) is a slender, high-aspect-ratio airplane powered by a fuel-injected, four-cylinder ROTAX 912 engine aspirated by a three-stage, four-turbine turbocharger system with intercooling. Heat exchangers for the engine and intercooler coolant loops are a prominent feature on the center fuselage and under-wing positions. The engine is buried within the aft fuselage section, with a carbon-composite drive shaft extending rearward to drive a high-altitude, low-Reynolds-number-optimized two-blade propeller.

The airplane was demonstrated to fly at indicated airspeeds from 45 to 70 knots (23 to 36 m/s) and to climb at a healthy rate of 200 ft/min (1 m/s) at an altitude of 60,000 ft (≈18 km). The ascent to this altitude takes about 170 minutes, corresponding to an average climb rate of about 350 ft/min (≈1.8 m/s).

The Perseus B is a remotely piloted airplane designed to carry scientific instruments for research at high altitudes.

Because of the developmental aspects of the flight, the maximum altitude was maintained only momentarily before descent was initiated. Temperatures encountered at altitude were as low as –70 °C, and proved too harsh for some components, including a Mode 3C Federal Aviation Administration radar transponder, which ceased operating at an altitude of approximately 53,000 ft (≈16 km), and began operating again at approximately 38,000 ft (≈12 km) after it had warmed sufficiently. Global Positioning System (GPS) data became intermittent above 57,000 ft (≈17 km), but because the GPS data stream returned upon descent through the same altitude, the intermittency is thought to be due to software lockout rather than thermal effects. Both of these anomalies are easily correctable by (1) adoption of better thermal management of the environment of the transponder (e.g., installation of a heating blanket), and (2) obtaining the correct GPS software for use at high altitude. The aerodynamic performance of the airplane and the performances of its propulsion and control systems were flawless throughout the flight.

Prior to the 60,000-ft flight, three other flights to altitudes of 15,000 ft (≈4.6 km), 27,000 ft (≈8.2 km), and 45,000 ft (≈14 km), respectively, were made as envelope-expansion missions. Data obtained from the total of four flights are being analyzed. The results of this analysis will be used to modify the aircraft to fly longer at 60,000 ft, as well as to increase the reliability and robustness of aircraft systems, including the data link and flight-control logic. These modifications will prepare the Perseus B aircraft for another flight-test phase to demonstrate the duration at altitude and mission-readiness of the aircraft and test team. Following this phase, it is expected that the aircraft will be ready for work in flying instruments and sensors for scientific missions.

The aircraft will be capable of carrying a nominal payload mass of 176 lb (80 kg) for 8 hours on station at 60,000 ft. It can carry as much as 265 lb (120 kg) on a mission of longer duration at lower altitude. Up to 1 kW of electrical power at a potential of 28 V can be provided to the payload.

The flight-test techniques developed and experience gained from this first Perseus B deployment will be utilized in improving the safety and efficiency of future flight-test programs for ERAST and other unpiloted-aircraft projects at Dryden Flight Research Center. Technical information is collected and used by all of the ERAST Alliance members to further the development and mission-readiness of high-altitude, long-duration uninhabited scientific aircraft.

This work was done by Aurora Flight Sciences Corporation and managed by Gary B. Cosentino for Dryden Flight Research Center. For further information, access the Technical Support Package (TSP) free on-line at under the Machinery/Automation category.


NASA Tech Briefs Magazine

This article first appeared in the April, 1999 issue of NASA Tech Briefs Magazine.

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