The Altair/Predator B: An Earth Science Aircraft for the 21st Century

NASA's Dryden Flight Research Center, Edwards, CA, has partnered with General Atomics Aeronautical Systems, Inc. (GA-ASI) of San Diego, CA, to demonstrate technologies that will expand the capabilities of remotely operated, uninhabited aircraft to perform high-altitude earth science missions. To accomplish the task, GA-ASI is developing an enlarged version of its Predator reconnaissance aircraft, the Predator B®, including an extended-wingspan Altair version for NASA, to meet these requirements.

The Project

GA-ASI's task under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) Joint Sponsored Research Agreement calls for GA-ASI to develop and demonstrate technical performance and operational capabilities that will meet the needs of the science community. As joint partners in the project, which covers flight validation as well as development of the aircraft, NASA's Office of Aerospace Technology is investing approximately $10 million, while GA-ASI is contributing additional funds, with about $8 million earmarked for the Altair project.

A satellite antenna and electro-optical/infrared sensors were among payloads installed on the Altair for the UAV’s flight demonstration.

NASA's Office of Earth Science established a stringent set of requirements for the conventionally powered, remotely, or autonomously operated aircraft. Among these requirements were a mission endurance of 24 to 48 hours at a primary altitude range of 40,000 to 65,000 feet with a payload of at least 660 lb (300 kg). Another key requirement is to develop the capability and operational procedures to allow operations from conventional airports without conflict with piloted aircraft, including new control, communications, and collision-avoidance technologies that are critical to enabling UAVs to fly safely in national airspace.

In addition to triple-redundant avionics, Altair is configured with a fault-tolerant, dual-architecture flight control system, and is equipped with an automated collision-avoidance system as well as an airtraffic control voice relay that allows Federal Aviation Administration (FAA) air-traffic controllers to talk to the groundbased Altair pilots through the aircraft. Command and control of the Altair, as well as research data gathered by Altair, will be transmitted through an "over the horizon" satellite link that allows scientists to receive research information as soon as the Altair obtains it. The aircraft also will have to meet all FAA airworthiness and maintenance standards.

The first Predator B prototype uninhabited air vehicle (UAV) is powered by a Honeywell TPE-331-10T turboprop engine, rated to 700 shaft horsepower, driving a rear-mounted, three-blade, controllable- pitch propeller. The Predator B is 36 feet long and has a wingspan of 64 feet, about 16 feet longer than the Predator. It is distinguished from its smaller cousin by its Y-shaped tail, with a ventral vertical fin. It is designed for a maximum gross takeoff weight of 6,400 lbs. The first turbine-powered aircraft built by GA-ASI, the Predator B is designed to fly as long as 25 hours at up to 200 knots indicated airspeed at altitudes as high as 45,000 feet, while carrying payloads of up to 750 lbs. The aircraft are designed to meet Federal Air Regulations Part 23 requirements.

The first Predator B prototype — aircraft 001 — logged its first flight on February 2, 2001 from the GA-ASI flight operations facility at El Mirage, CA. After an initial series of airworthiness test flights and downtime for various software and systems upgrades, the Predator B 001 flew a second series of flight tests in mid-summer 2001, aimed at expansion of its flight envelope and validation of its autonomous flight capabilities. The prototype reached a maximum sustainable altitude of 48,300 feet during one of those flights over the Edwards Air Force Base test range.

The Altair technology-demonstration variant for NASA is designed to carry an equivalent payload for as long as 32 hours at up to 52,000 feet. It has a maximum range of about 4,200 miles and can carry up to 750 pounds of sensors, radar, communications, and imaging equipment in its forward fuselage. The Altair is 34 feet long, and has a wingspan of 86 feet, 22 feet longer than the Predator B's 64-foot wingspan. Extensions of 11 feet will be added to each wingtip, giving the Altair an overall wingspan of 86 feet with an aspect ratio of 23.5. It also will be powered by the TPE-331-10 turboprop engine.

Operational Requirements

NASA's Earth Science Enterprise has established a stringent set of requirements for the Altair/Predator B to demonstrate its capability to serve as a high-altitude remotely or autonomously operated airborne platform for Earth science missions. The requirements include:

  • Flight demonstrate a primary altitude range of 40,000 to 65,000 feet.
  • Flight demonstrate a mission endurance of 24 to 48 hours with a minimum 660 lb. (300 kg) payload at the primary altitude range.
  • Demonstrate ease of ground handling so that the vehicle is capable of operating from general aviation airports and can integrate with conventional aircraft operations.
  • Demonstrate a flight environment envelope that is consistent with the weather and operating maneuverability necessary to support a broad range of science missions.
  • Demonstrate UAV compliance with current applicable FAA requirements or guidelines on UAV operations in civil airspace including, but not limited to, see & avoid compliance criteria and airworthiness/maintenance standards criteria.
  • Demonstrate Over the Horizon/See & Avoid Operations (in unrestricted FAA airspace, beyond line-of-sight) including, but not limited to, communication with FAA Centers (SATCOM relay of switchable UHF); communication of See & Avoid information; demonstrate logistics capability of the integrated system (UAV, GSE, GCS, etc.) to be deployable and/or transportable to remote locations; and perform a successful multiflight demonstration of a mission representative of those typically used for gathering science data.

Earth Science Missions

The Altair is designed to perform a variety of Earth science missions specified by NASA's Earth Science Enterprise. To demonstrate its ability to meet those standards, GA-ASI is required to conduct a multi-flight demonstration of the Altair representative of a scientific data-gathering mission, including all the necessary integrated logistical support that would be needed when operating from a remote location. The demonstration mission will include three long-duration, high-altitude flights with a payload of imaging and atmospheric sampling instruments.

Many potential science missions are being considered for the demonstration flights. These missions may take place over a wide variety of geographic locations, capitalizing on the aircraft's extreme range and duration. Volcanic observation over Hawaii, forest fire monitoring over the Western United States, and atmospheric sampling over Alaska are among the science demonstration mission possibilities — missions that are often too dangerous, difficult, or too lengthy for manned aircraft to perform. UAVs are uniquely positioned to perform long missions that have repetitive routines.

The long, narrow wings of NASA’s Altair are designed to allow the UAV to maintain long-duration flight at high altitudes.

Begun as a company-funded effort in 1999, the Predator B development program became a jointly funded effort by GA-ASI and NASA in January 2000, after NASA selected the Altair variant from several competing proposals for development to meet the agency's Earth Science Enterprise UAV requirements.

GA-ASI is no stranger to the ERAST project. Its Altus II had been involved in ERAST as a technology demonstrator of aerodynamic, propulsion, and control system technologies for future high-altitude, longendurance UAVs designed for civil scientific and commercial uses. The Altus II also has been utilized for several Earth resource missions, most notably a high-altitude atmospheric cloud radiation study conducted over Hawaii in the spring of 1999.

Milestones & Results

A milestone in the development of high-altitude, long-endurance, remotely operated aircraft occurred on June 9, 2003 with the first flight of NASA's Altair. The slender-wing aircraft lifted off the runway at GA-ASI's flight test facility for a checkout flight that evaluated the aircraft's basic airworthiness and flight controls. The rear-engine Altair glided to a landing on the remote desert runway 24 minutes later. The entire flight was conducted at low altitude within a comparatively short range of the El Mirage airstrip.

"This is what we've been waiting for," said Glenn Hamilton, Altair project manager at NASA Dryden, after witnessing the first flight. "Now we can move forward with getting UAVs into the national airspace and conducting research."

Hamilton's comments were echoed by Thomas J. Cassidy, president and chief executive officer of GA-ASI. "Altair's first flight is a culmination of 10 years of experience in building reliable unmanned aircraft based on a common design philosophy," Cassidy added. "I am very proud of our design, manufacturing, and flightreadiness teams for their dedication to a high-performance level of excellence."

For more information on the Altair/Predator B UAV program, visit