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-2002-08-020 DFRC 

ERAST:

Environmental Research Aircraft

and Sensor Technology

The Environmental Research Aircraft and Sensor 

Technology (ERAST) project is a joint NASA-industry initiative to develop and demonstrate aeronautical 

technologies that could lead to a family of remotely or 

autonomously operated uninhabited aerial vehicles 

(UAVs) to carry out long-duration Earth science and 

environmental missions at high altitudes. 

UAVs offer great promise to meet the needs of 

both science and industry for airborne sensing and 

imaging in a cost-effective manner while alleviating 

the constraints of mission duration, altitude and flight 

over inhospitable terrain faced by aircraft with onboard crew. Such long-duration, high-altitude UAVs 

can be flown on upper-atmospheric science missions 

to collect data and images which would help scientists 

identify and monitor environmental and climatic 

changes. They also could carry telecommunications 

equipment to high altitudes, serving much like satellites for a fraction of the cost of putting a traditional 

satellite in space. 

ERAST Goals and Objectives 

The primary objective of ERAST is to develop and 

transfer advanced technology to an emerging American UAV industry, and to conduct flight demonstrations of those technologies in controlled environments 

to validate the capability of UAVs to fly operational 

science missions. A concurrent ERAST effort is the 

development, miniaturization and integration of 

special-purpose sensors and imaging equipment for 

UAVs. 

The project’s goals are in line with the RevolutionHelios Prototype, built by AeroVironment Inc. ary Vehicles element of NASA’s Office of Aerospace 

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Technology Aeronautics Blueprint, to create environmentally compatible aircraft with revolutionary capabilities for unprecedented levels of performance and 

safety. ERAST’s goals also align with those of 

NASA’s Earth Science Enterprise to expand scientific 

knowledge of the Earth system using NASA’s unique 

capabilities from the vantage point of space, aircraft 

and on-site platforms. 

ERAST Project Management 

Begun in late 1993, the ERAST technology demonstration project is managed by NASA’s Dryden Flight 

Research Center, with significant contributions from 

NASA’s Ames, Langley and Glenn Research Centers. 

The project is operated as a joint NASA-industry 

alliance under a Joint Sponsored Research Agreement. 

Four small aircraft manufacturers are members of the 

ERAST Alliance, including AeroVironment, Aurora 

Flight Sciences, General Atomics Aeronautical Systems and Scaled Composites. Other partners in the 

alliance include Thermo-Mechanical Systems, 

Hyperspectral Sciences, and Longitude 122 West. 

American Technology Alliances (AmTech) is serving 

as facilitator for the Alliance. 

As project manager, NASA Dryden is responsible 

for establishing overall priorities and technical approaches toward meeting project objectives, providing 

funding, individual project oversight, coordination of 

facilities for UAV operations, development and 

coordination of payloads for demonstration flights, 

and ensuring that actions taken by ERAST Alliance 

partners meet NASA’s future needs for UAVs. NASA 

also conducts independent reviews of the vehicle 

systems and provides input to the builder/operator to 

improve the aircraft design and operations while 

reducing overall risk. 

NASA is working with the Federal Aviation 

Administration on the long-term issues related to 

operations of these vehicles in the national airspace 

and developing technology such as “see and avoid” 

sensors/processors and over-the-horizon communications equipment to make operations in civil airspace 

practical. 

ERAST also has a significant educational 

outreach component intended to foster student interest 

in science, math and aeronautics. 

ERAST Aircraft & Milestones 

Several remotely controlled prototypes have been 

evaluated or have served as flying testbeds for propulsion, aerodynamics, structures, materials, avionics and 

sensor technology. Among these have been the conventionally-powered Altus II and Altair, developed 

by General Atomics Aeronautical Systems; the Perseus A and B, developed by Aurora Flight Sciences; 

the Demonstrator 2 and the “optionally piloted” 

Proteus, developed by Scaled Composites; and the 

solar-powered Pathfinder, Pathfinder-Plus, and Centurion/Helios Prototype, developed by AeroVironment. 

A number of flight milestones have been achieved 

during the ERAST project to date, including: 

• A 26-hour flight above 20,000 feet altitude by the 

Altus in late 1996; 

• Sustained flight above 55,000 feet for four hours by 

the same aircraft in 1999 after being equipped with 

a powerful turbocharger; 

• An altitude of over 60,000 feet achieved by the 

Perseus B in 1998, an unofficial record for a turbocharged conventionally fueled single-engine, 

propeller-driven craft; 

• An altitude of 80,201 feet achieved by the Pathfinder-Plus in August, 1998, at that time an unofficial world record for both propeller-driven and 

solar-powered aircraft. 

• An unofficial world-record altitude of 96,863 feet 

achieved by the Helios Prototype in August, 2001, 

more than two miles higher than any non-rocket 

powered aircraft had ever flown. 

In addition, two highly successful science demonstrations have been flown—a crop, forest and coral 

reef imaging mission by the Pathfinder over the 

Hawaiian island of Kaua’i in 1997 and the Atmospheric Radiation Measurement series flown by the 

Altus in 1996 and 1999. These missions demonstrated 

the utility of the aircraft for science experiments and 

local crop management. 

ERAST Current Focus 

In its second phase, ERAST narrowed its projectcompletion focus to three high-priority areas: further 

development of solar-electric propulsion, development 

of a consumable-fuel aircraft capable of meeting 

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specific mission requirements of NASA’s Earth 

Science Enterprise, and further development of UAV 

subsystems technologies. That includes development 

of “detect, see and avoid” and over-the-horizon communications systems, as well as operational concept 

and draft FAA certification roadmaps. 

For the first, emphasis was placed on improving 

systems reliability which allowed the solar-powered 

Helios Prototype to demonstrate flight near 100,000 

feet altitude, and development of supplemental energy 

systems based on fuel cell technology which would 

enable the craft to perform multi-day sustained flight 

day and night at altitudes above 50,000 feet. 

For the second, NASA selected General AtomicsAeronautical Systems Inc. (GA-ASI) to develop the 

Altair, an extended-wingspan civil variant of its 

turboprop-powered Predator B military reconnaissance 

UAV, to exceed the minimum payload, duration and 

altitude requirements established by NASA’s Earth 

Science Enterprise. The Altair will also be required to 

demonstrate operational reliability and redundancy 

requirements suitable for “over-the-horizon” operations in unrestricted airspace. 

In the third area, subsystem technologies under 

development include a detect, see and avoid system 

which would allow UAVs to fly safely in national 

airspace. The systems, including radio, radar and 

infrared sensor devices, would enable UAVs to fly in 

the same airspace as other aircraft without risk of 

collision. A flight demonstration using the Proteus 

aircraft to evaluate promising see-and-avoid technologies was flown in spring, 2002 over southern New 

Mexico. 

The Pathfinder-Plus is also flying several demonstration missions in 2002 to confirm the practical 

utility of high-flying, remotely piloted, environmentally friendly solar aircraft for commercial purposes. A 

two-flight series in July emphasized its potential as a 

platform for telecommunications relay services, and 

another demonstration in September will find the 

Pathfinder-Plus soaring aloft on a three-flight coffee 

harvest optimization imaging mission. 

Completion of the above flight-demonstration 

milestones will support commercial application of 

UAVs for such areas as telecommunications, resource 

and disaster relief management. 

Helios Prototype/Centurion/Pathfinder 

Designed to reach extreme altitudes of up to 

100,000 feet on single-day flights and continuous 

flight for several days at lower altitudes, the Helios 

Prototype is a fourth-generation solar-powered flying 

wing designed by AeroVironment. 

First came the 98-foot wingspan Pathfinder which 

set unofficial world records for solar-powered and 

propeller-driven aircraft, leading to in a flight to 

Pathfinder-Plus, built by AeroVironment Inc. 

80,201 feet altitude in mid-1998 by the extendedwingspan Pathfinder-Plus. 

The Dryden Flight Research Center hosted the 

initial test flights of the 206-foot span Centurion flying 

wing in late 1998. A second series of flights in late 

1999 validated the flying characteristics of the extended 247-foot span version, renamed the Helios 

Prototype. Designed and built by AeroVironment, 

Inc., this aircraft is propelled by eight to 14 electric 

motors, depending on its mission. Although its initial 

low altitude test flights at Dryden were flown on 

battery power, it is now covered with solar cells and 

powered by energy from the Sun. The Helios Prototype flew into aviation history in August, 2001, when 

it reached 96,863 feet during a maximum-altitude 

demonstration flight near Hawaii. Certification of that 

milestone as a world altitude record for non-rocket 

powered aircraft is pending. 

Lightweight supplementary energy systems for 

the Helios Prototype based on fuel cell technology are 

well along in their development. When perfected, the 

systems will allow production versions of the Helios 

to remain aloft from a week to nearly indefinitely, 

storing sufficient energy received from the Sun during 

the day to power the aircraft through the night. The 

Helios will be able to perform many functions of 

communications satellites with greater flexibility and 

at far less cost, and provide a platform for continuous 

monitoring of the atmosphere and ground imaging. 

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Altair (Predator B) 

The Altair, a civilian variant of the enlarged, upgraded 

version of the RQ-1A Predator military reconnaissance UAV called the Predator B, has been developed 

by General Atomics-Aeronautical Systems Inc. (GAASI) to meet specific requirements of NASA’s Earth 

Science Enterprise for a flight-validated consumablefuel UAV to perform on-location science missions. 

Under a cost-sharing agreement with NASA, GA-ASI 

Altair, being built by GA-ASI. 

built three prototypes, two Predator Bs and the extended-wingspan Altair. The Altair is powered by a 

700-hp. turboprop engine and capable of carrying a 

660-lb. payload for up to 32 hours at altitudes ranging 

from 42,000 to 52,000 feet. In addition to exceeding 

minimum performance requirements set by NASA’s 

Earth Science Enterprise, the Altair has enhanced 

avionics systems to better enable it to to fly in FAAcontrolled civil airspace and demonstrate “over-thehorizon” command and control capability from a 

ground station. 

Perseus B 

The Perseus B is the third generation of the Perseus 

design developed by Aurora Flight Sciences Inc., 

having been preceded by the Perseus proof-of-concept 

demonstrator and the Perseus A aircraft. Aurora flew 

the Perseus B aircraft to an altitude over 60,000 feet in 

1998, meeting an ERAST milestone. The Perseus B 

Perseus B, built by Aurora Flight Sciences. 

utilizes a triple-turbocharged Rotax piston engine for 

power. With external fuel tanks and engine upgrades, 

the Perseus B is capable of carrying a 176-lb. payload 

at an altitude of 55,000 feet for a duration of four 

hours, a mission milestone set by the ERAST project 

for the aircraft. Under ERAST, Perseus-B helped to 

validate and mature propulsion, avionics and command and control systems technology. 

Altus II 

General Atomics/Aeronautical Systems also produced 

the dual-turbocharged Altus II aircraft, a modified 

version of the RQ-1A Predator military reconnaissance UAV designed for civilian environmental 

science missions. The Altus II is also powered by a 

small four-cylinder Rotax piston engine driving a rearmounted pusher propeller. The Altus II expanded its 

flight envelope to the point where it met an ERAST 

mission requirement for four hours flight duration at 

55,000 feet altitude, and also maintained flight above 

Altus II, built by General Atomics/Aeronautical Systems Inc. 

50,000 feet for eight hours in 1999. The Altus has 

successfully completed several science missions for 

the Department of Energy’s Atmospheric Radiation 

Measurement/UAV project, including a flight series at 

high altitudes over Hawaii in 1999 and a loweraltitude ARM study flight lasting in excess of 26 hours 

over Oklahoma in 1996. Under ERAST, the Altus II 

was used to validate propulsion system technology as 

well as other flight systems such as avionics, command and control. 

Proteus 

Scaled Composites produced the Proteus aircraft as a 

piloted aircraft primarily designed for commercial 

telecommunications relay purposes, but it is also 

capable of completing many of the ERAST missions. 

First flown in mid-1998, the twin turbofan-engine 

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Proteus, built by Scaled Composites Inc. 

aircraft is larger and heavier than other consumablefuel aircraft involved in ERAST. The Proteus is a 

tandem-wing design intended to carry payloads of up 

to 2,000 pounds to altitudes above 60,000 feet and to 

remain on station up to 14 hours. Development of the 

Proteus under ERAST focused on supporting development of the aircraft’s flight control system to allow it 

to be an “optionally piloted” aircraft, capable of being 

flown either by an onboard pilot or autonomously. 

Proteus was also utilized to validate many of the 

technologies required for UAVs, including over-thehorizon command and control communications. 

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