NASA 

National Aeronautics and 

Facts

Space Administration 

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-276-3449 

FAX 661-276-3566 

pao@dfrc.nasa.gov FS-1999-08-059 DFRC 

Perseus B

The Perseus B is a remotely piloted aircraft developed as a design and performance testbed under NASA’s Environmental Research Aircraft and Sensor Technology (ERAST) project. 

The goal of ERAST is to foster new propulsion, materials, control, instrumentation, and sensor technologies that 

could enable development of a variety of slow-flying, high-altitude aircraft to carry out long-duration science missions in the upper stratosphere. The missions, flown either autonomously or remotely by a pilot in a ground control 

station, could include Earth sciences studies, storm tracking, atmospheric sampling, and spectral imaging for agricultural and natural resources monitoring. Such “atmospheric satellite” aircraft also would have potential for commercial use, serving as relay platforms for telecommunications systems. 

Perseus B is one of several flight vehicles involved in the ERAST project. It is a piston engine, propeller-powered 

aircraft designed and built by Aurora Flight Sciences Corp., Manassas, Va. Objectives of the aircraft’s ERAST flight 

tests are to reach and maintain horizontal flight above 60,000 feet and demonstrate the capability to fly missions 

lasting from 8 to 24 hours, depending on payload and altitude requirements. 

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The Perseus B established an unofficial altitude record of 

60,280 feet for a single-engine, propeller-driven remotely piloted aircraft on its seventh flight on June 27, 

1998. 

Modifications to the aircraft since its last flight series are 

being evaluated in a series of operational readiness and 

test missions being conducted at NASA’s Dryden Flight 

Research Center, Edwards, Calif., in August and September 1999. The modifications include engine, avionics, and flight control system improvements to increase 

flight endurance and reliability. 

In addition to its role in the NASA ERAST project, 

Aurora Flight Sciences is developing Perseus B to 

become a future platform aircraft for the type of atmospheric and environmental science missions envisioned 

in the ERAST project’s goals. 

Aircraft Description 

The Perseus B is a high-wing monoplane with a conventional tail design. Its narrow, straight, high aspect-ratio 

wing is mounted atop the fuselage. The aircraft is a 

pusher design with the propeller mounted at the rear, 

allowing use of an interchangeable payload bay in the 

Perseus B’s forward fuselage for science experiments. 

This design allows for unobstructed airflow to the 

sensors and other devices mounted in the payload 

compartment. Intercooler radiators are mounted on each 

side of the mid-fuselage and beneath the inner portions 

of the wings. The Perseus B incorporates a conventional 

tricycle-type fixed landing gear. The aircraft was designed to meet Federal Aviation Regulations (FAR) Part 

23 guidelines for structural strength, and has been limit 

load tested to three Gs—three times the force of gravity—at maximum gross takeoff weight. 

Perseus B is powered by a Rotax 914 horizontally 

opposed four-cylinder piston engine mounted in the midfuselage area. An Aurora-developed three-stage, fourturbine turbocharger provides sea-level air pressure to 

the engine up to 60,000 feet. A two-blade, variable-pitch 

propeller mounted at the rear of the fuselage is linked to 

the engine by a driveshaft. 

Perseus B is flown remotely by a pilot from a mobile 

flight control station on the ground. A Global Positioning System (GPS) unit provides way-point navigation 

data for continuous and precise location during flight. 

The ground control station features dual independent 

consoles for aircraft control and systems monitoring. The 

system includes dual independent telemetry uplinks and 

downlinks. Dish antennas are mounted atop the control 

station vehicle on a boom that is directionally controlled 

by GPS location information generated on the aircraft. 

The mobile unit includes a host of displays on which 

aircraft and systems performance are continually monitored during flight. The same telemetry and video 

imaging monitored in the mobile ground station is also 

viewed by NASA and Aurora Flight Sciences personnel 

in the Dryden Mission Control Center. 

A flight termination system, required on remotely piloted 

aircraft being flown in military restricted airspace, 

includes a parachute system deployed on command, plus 

a C-Band radar beacon and a Mode-C transponder to aid 

in location. 

Perseus B Development 

The Perseus B now undergoing test and development is 

the third generation of the Perseus design which began 

with the Perseus Proof-Of-Concept aircraft. Perseus was 

initially developed as part of NASA’s Small HighAltitude Science Aircraft (SHASA) program, which later 

evolved into the ERAST project. The Perseus Proof-OfConcept aircraft first flew in November 1991 and made 

three low-altitude flights within a month to validate the 

Perseus aerodynamic model and flight control systems. 

Next came the redesigned Perseus A, which incorporated 

a closed-cycle combustion system that mixed oxygen 

carried aboard the aircraft with engine exhaust to compensate for the thin air at high altitudes. The Perseus A 

was towed into the air by a ground vehicle and its engine 

started after it became airborne. Prior to landing, the 

engine was stopped, the propeller locked in horizontal 

position, and the Perseus A glided to a landing on its 

unique bicycle-type landing gear. Two Perseus A aircraft 

were built, and made 21 flights in 1993-1994. One of the 

Perseus A aircraft reached over 50,000 feet on its third 

test flight. Although one of the Perseus A aircraft was 

destroyed in a crash after a vertical gyroscope failed in 

flight, the other aircraft completed its test program and 

remains on display at Aurora’s facility in Manassas. 

The present Perseus B aircraft utilizes a more conventional powerplant coupled to a powerful three-stage, 

four-turbine turbocharger to furnish the equivalent of 

sea-level air at high altitudes. It first flew Oct. 7, 1994, 

and made two flights in 1996 before being damaged in a 

hard landing on the dry lakebed after a propeller shaft 

failure. After a number of improvements and upgrades— 

including extending the original 58.5-foot wingspan to 

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71.5 feet to enhance high-altitude performance—the

Perseus B returned to Dryden in the spring of 1998 for a 

series of four flights. Those flights culminated with a 

flight on June 27 to an altitude of 60,280 feet, establishing an unofficial altitude record for a single-engine, 

propeller-driven remotely piloted aircraft. 

Recent Upgrades 

Modifications to the prototype aircraft and its systems 

since its last development flight series in 1998 are 

expected to allow mission durations of up to 8 hours on 

future flights, as well as improve the overall reliability of 

the aircraft and its systems. 

The latest modifications include external fuel pods on 

the wing that more than double the fuel capacity to 100 

gallons. Engine power has been increased by more than 

20 percent by boosting the turbocharger output, and is 

now flat-rated at 105 horsepower to 60,000 feet. Fuel 

consumption has been reduced with fuel control modifications and a leaner fuel-air mixture that does not 

compromise power. The propulsion changes have been 

tested in Aurora Flight Sciences’ altitude chamber to 

simulated heights of 66,000 feet. This boost in engine 

performance is expected to give the aircraft better allaround operational capabilities, including a greater 

payload and better mission endurance at higher altitudes. 

Improvements in the aircraft’s avionics suite include a 

second GPS unit, a ring laser gyro to replace a mechanical unit, and installation of a longer-life emergency 

battery. 

The aircraft’s rudder has been modified by splitting it in 

two and installing an additional servo motor. Combined 

with a split elevator and independent ailerons, this gives 

the primary flight control system full redundancy for 

flight safety. The flight control software has also been 

modified to incorporate fault-tolerant control capability, 

giving the system automatic detection and compensation 

for any flight sensor or actuator failure. 

The aircraft’s air data instrumentation system has been 

supplemented with the installation of a second pitot tube. 

The new unit is a heated five-hole probe to insure 

accurate speed, pitch, and angle-of-attack measurements 

when the aircraft is at high altitudes. 

Instrumentation installed on the aircraft for initial 

development flights has been removed or incorporated 

into the flight data system to free-up payload space for 

future mission use. Standard aircraft running lights have 

been installed so the aircraft can be safely flown at night. 

Current Test and Readiness Missions 

Aurora’s Perseus B test and development team planned 

three missions for the aircraft during August and September 1999 to demonstrate its altitude, performance, 

and payload capabilities. The number of flights to 

achieve the three mission goals is expected to be from 

three to five. The operational readiness flight demonstrations are jointly sponsored and funded by ERAST and 

NASA’s Office of Earth Science at NASA Headquarters, 

Washington, D.C. 

The first mission is a functional check flight (FCF) with 

a goal of reaching an altitude of 30,000 feet in about two 

hours. The purpose of the FCF is to evaluate all aircraft, 

control, and navigation systems in a safe operational 

flight environment before proceeding with more demanding flights. If the FCF reveals that a system or 

subsystem needs to be modified or replaced, a second 

FCF can be scheduled. 

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The second mission for the aircraft is to achieve its 

maximum design altitude in its present configuration, 

believed to be about 62,000 ft. The flight is expected to 

take about 5 hours to complete. 

The third and final mission for Perseus B in the current 

series will be focused on endurance. The goal is to climb 

to 60,000 feet in a stair-step fashion while carrying a 

maximum payload weight, and to remain above 55,000 

feet for at least four hours of the projected eight-hour 

flight. In addition, project planners hope to expand the 

range the aircraft can be flown from the ground control 

station from 20 to 60 nautical miles. 

The NASA Dryden Connection 

All Perseus B development flights have been conducted 

at the NASA Dryden Flight Research Center. A NASA 

project manager is assigned as coordinator and liaison 

for all Perseus B activities such as flight operations and 

scheduling, flight safety, and the use of NASA facilities 

by test and development personnel from Aurora Flight 

Sciences. 

Dryden provides hangar and office space for the Perseus 

B aircraft and flight test and development team. During 

flight operations, the Dryden Mission Control Center is 

staffed by NASA and Aurora Flight Sciences personnel 

who continuously monitor the performance of the 

aircraft and its individual systems until the mission has 

ended. 

The ERAST Project 

NASA’s ERAST project is developing aeronautical 

technologies for a new generation of remotely piloted 

and autonomous aircraft for a variety of upper-atmospheric science missions and commercial applications. 

ERAST management and operations are centered at 

NASA Dryden Flight Research Center. A parallel effort 

at NASA’s Ames Research Center, Moffett Field, Calif., 

is focused on the development of lightweight, microminiaturized sensors that will be used to carry out the 

environmental research. 

Flying at slow speeds for long periods of time at altitudes of up to 100,000 feet, the post-ERAST vehicles 

could be used to gather, identify, and monitor environmental data to assess global climate changes, monitor 

Earth resources, and serve as telecommunications 

platforms at a fraction of the cost of placing satellites 

into space. 

Also contributing to the ERAST project in the areas of 

propulsion, energy storage systems, structures and 

systems analysis are NASA’s Glenn Research Center, 

Cleveland, Ohio, and Langley Research Center, Hampton, Va. NASA is also working closely with the Federal 

Aviation Administration to develop operational plans so 

the remotely operated aircraft can be safely flown in 

national airspace. 

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Aircraft Specifications 

• Wingspan: 71.5 ft (21.5 m) • Airspeed: Approx. 60 mi/h. (52 kn) cruise, 

• Wing area: 194 ft2 79 mi/h (69 kn) never-exceed speed. 

• Wing aspect ratio: About 26 to 1 • Maximum altitude: Approximately 62,000 ft 

• Length: 25 ft (7.6 m) (18.9 km). 

• Height: 12 ft (3.6 m) • Endurance: Prototype: approx. 18 hrs at 16,000 ft, 

• Gross weight: Approx. 2,200 lb (990 kg) with full 

internal fuel; approx. 2,500 lb with additional 

external wing-mounted fuel tanks. 

7.5 hrs at 50,000 ft, 1 hr at 60,000 ft. Production:

Approx. 24 hrs at 62,000 ft. 

• Range: Approx. 1,600 miles point-to-point (pro-

• Payload: Up to 260 lb of sensors and instruments 

in nose compartment; typical payload approx 

175 lb. 

duction version); radius from ground station 

approximately 60 miles line-of-sight communications limit. 

• Propulsion: Rotax 914 four-cylinder piston engine 

mounted in the mid-fuselage integrated with an 

Aurora-designed three-stage turbocharger, driving 

a tail-mounted lightweight two-blade pusher 

propeller via an eight-foot driveshaft. Engine is 

flat-rated at 105 hp to 60,000 ft altitude. 

• Flight controls: The aircraft has standard three-axis 

flight control surfaces—elevators, rudder and 

ailerons—for pitch, yaw, and roll motions. 

• Materials: Perseus B is constructed primarily of 

composite materials such as fiberglass, graphite 

epoxy, Nomex honeycomb, and Kevlar. The 

• Fuel capacity: 100 gal, including 40 gal internal 

and 60 gal in underwing auxiliary tanks, standard 

aviation gasoline. 

fuselage frame is welded tubular steel. 

• Manufacturer: Aurora Flight Sciences Corp., 

Manassas, Va. 

August 1999 

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