Edward Hoffman James Utick Alex Wightman

Ehoffman@oswego.edu

Utick@oswego.edu

Wightman@oswego.edu

• Solar-powered Aircraft: An aircraft that could stay aloft all day powered only by sunlight. An aircraft that is no more than a flying wing, able to fly without rudders, ailerons, tails or jet engines. An aircraft that flies without an onboard human pilot.

• Dryden Flight Research Center: Developing the latest in Global Civil Aviation Technology. Reduce the risks associated with using the new ideas and make it transferable to the private sector for commercialization. Conduct safe and timely flight research for discovery, technology development, and technology transfer for U.S. Aeronautics. Develop piloted and uninhabited aircraft testbeds for research and science missions. Conduct airborne science missions and flight operations. They also develop and construct a lightweight aircraft using composite materials such as carbon fiber, graphite epoxy, kevlar, nomex, styrofoam, and a thin transparent plastic skin.

• Solar cell powered aircraft. Bi-facial solar cells covering the upper wing surfaces. Electrical powered on board lithium batteries for current flight series. Brushless direct-current electric motors for driving two-blade propellers designed for high altitude. Prototype hydrogen-oxygen fuel cell based energy storage systems for stored energy for night flying. Solar cell array: Solar cell covers over 75% of its upper wing surface. The solar cell arrays are capable not only of absorbing direct sunlight, but can absorb light reflected from the ground through the transparent lower surfaces.

• Conduct flight testing in California’s high desert at Edwards Air Force Base. The desert environment provides good flying weather and average of 345 days a year, and the absence of large population centers throughout the high desert helps eliminate problems associated with aircraft noise and flight patterns.

• 12,000 square miles of special-use airspace over California’s high desert are used for research flights. Agencies monitoring flights are linked to the Western Aeronautical Test Range. The W.A.T.R. provides tracking and data acquisitions support through an automated complex of computer-controlled tracking and communications systems.

• Dryden research facility includes a high temperature and loads calibration laboratory to ground test aircraft and structural components for the combined effects of loads and heat. A flow visualization facility to study flow patterns on models and small aircraft components and a flight facility to carry out flight research with remotely piloted vehicles.

• Dryden’s Research Aircraft Integration Facility is used to carry out checks of flight controls, avionics, and electronics. It is the only facility of its type in NASA and is designed to speed up and enhance systems on all types of research aircraft.

• The Environmental Research Aircraft and Sensor Technology Program (ERAST) is an effort by a NASA-industry alliance to develop aeronautical technologies that could lead to a family of unpiloted aircraft to carry out scientific and environmental missions at heights of up to 100,000 feet on flights lasting up to several days or more.

• The ERAST project is managed by NASA’s Dryden Flight Research Center, in addition, NASA’s Langley Research Center, Hampton, VA., Glenn Research Center, Cleveland, Ohio, and Ames Research Center, Moffett Field, CA., are significant contributors to advance technology development in the RPVS (remotely piloted vehicles) program.

• The ERAST project has a significant Education Outreach component intended to foster student interest in science and aeronautics. The program includes sight visits by over 1,000 children and teachers workshops attended by over 250 teachers.

• The ERAST mission; slower, higher, longer. Slower, subsonic speeds, as slow as 50 miles per hour. Higher, at altitudes as high as 100,000 feet. Longer, for continuous missions lasting as long as 96 hours.

• Long duration, high altitude remotely piloted vehicles are used to conduct a wide variety of earth and atmospheric science missions. ERAST missions also carry out storm tracking studies, atmospheric sampling, spectral imaging for agricultural and natural resources monitoring as well as serve as relay platforms for telecommunications systems.

• RPVS (remote piloted vehicles) could carry telecommunications equipment to high altitudes, serving like satellites for a fraction of the cost of putting a traditional satellite into space.

• RPVS operational missions could cut costs and provide an affordable vehicle or "Air Taxi" for science payloads. Parallel effect in developing the RPV, is the development of lightweight, microminiturized sensors which will be used to carry out the environmental research and earth monitoring.

• RPVS meeting scientific and industrial needs for airborne sensing and imaging in a cost-effective manner while alleviating the constraints of mission duration, altitude and flight over inhospitable terrain typical of aircraft flown by an onboard pilot.

• Several remotely controlled prototypes have been or are being evaluated in areas of propulsion, aerodynamics, structures, materials, avionics and sensor technology. The four prototypes are the Pathfinder, Pathfinder Plus, Centurion and Helios. Each aircraft has a direct correlation to the next.

• Pathfinder: Was the first generation of solar powered aircraft. Solar arrays covered most of the upper wing surface, which provided up to 8,000 W of power at high noon on a summer day to power the aircraft’s six electric motors, avionics, and communications systems. Pathfinder also had a backup battery system that could provide power for between two and five hours in limited duration of flight after dark.

• In 1993 Pathfinder reached and altitude of 50,500 feet, setting a new altitude record for solar powered aircraft. In 1996 the Pathfinder was transferred to Hawaii. The location was chosen as and optimal location for testing. Pathfinder due to high levels of sunlight, available airspace and radio frequencies, and the diversity of terrain and coastal ecosystems for validating scientific imaging applications. In 1996 the Pathfinder reached a world record for the propeller driven as well as solar powered aircraft of 71,530 feet.

• Pathfinder Environmental Monitoring Missions: The detection of forest nutrient status, forest regrowth after damage caused by hurricane Iniki, sediment/algal concentrations in coastal waters, and assessment of coral reef health.

• Pathfinder has flight-tested two new scientific instruments, a high spectral resolution Digital Array Scanned Interferometer and a high spatial resolution Airborne Real Time Imaging System both for NASA.

• Pathfinder: Wingspan: 98.4 ft; gross weight: 560 lb.; airspeed: 17-20 MPH cruise. Power: Arrays of solar cells; six 8,000 W Electric motors. Endurance: 14-15 hours daylight limited to 2-5 hours after dark. Materials: Composites, plastic, foam.

• Pathfinder Plus: Second generation of solar-powered aircraft. Was modified into the longer winged configuration. In 1998 the Pathfinder Plus was flown to a record altitude of 80,300ft and was aloft for 15 hours. The goal of the flights were to validate new solar cells and aerodynamic, propulsion and systems technology. In addition the Pathfinder Plus was powered by eight more efficient electric motors designed for the next generation aircraft, the Centurion.

• Pathfinder Plus flights are meticulously planned around the weather. Winds aloft often make the aircraft fly backwards or stationary, but winds that can adversely affect the Pathfinder Plus usually diminish above 30,000 ft

• Pathfinder Plus: Wingspan: 121 ft; gross weight: 700 lb.; Airspeed: 17-20 MPH cruise; Power: Array of solar cells; Eight 12,500 W electric motors; Endurance: 14-15 hours, daylight limited with 2-5 hours on backup batteries.

• Centurion is a unique remotely piloted solar powered airplane being developed under NASA’s Environmental Research Aircraft and Sensor Technology (ERAST) program at the Dryden Flight Research Center.

• Centurion is a lightweight flying wing aircraft that demonstrates the technology of applying solar power for long duration, high altitude flight.

• It is the first aircraft believed capable of achieving sustained horizontal flight at altitudes of 90,00 to 100,000 feet.

• Designed only for extreme altitudes, but to do it carrying 100 pounds of remote sensing and data collection instruments.

• It is capable of carrying 600 pounds of sensors, telecommunication and imaging equipment up to 80,000 feet.

• Also performing multi-week flights at the north and south poles.

Wingspan: 206 feet (61.8 meters)

Length: 12 feet (306 meters)

Wing Chord: 8feet (2.4 meters)(front to rear)

Aspect ratio: 26 to 1

Empty weight: Roughly 1,200 pounds (529 kilogram)

Solar cells spread across the wing’s upper surface.

• Four to seven missions had originally been planned, but the test series was completed in only three flights.

• The successful record flight is one more milestone on the way to commercial solar – powered aircraft becoming low – cost complements to satellites.

• These flights will: relay communications signals, take photographs, track storms and can do what satellites do but with more flexibility and less of a financial investment.

• The Helios prototype is currently the largest solar powered aircraft under development by Dryden Flight Research Center. This prototype will be unmanned and used to electronically record a wide variety of earth and atmospheric conditions.

• The Helios Aircraft is also known as an UAV, Uninhabited Aerial Vehicle.

• The Helios was flown for a test run in late 1998 to test handling and performance characteristics.

• Helios’ first mission was to reach and sustain flight for four days at 100,000 feet altitude with a 100-pound payload.

• The Helios second mission is to carry a heavier load of up to a 600 pounds at 70,000 feet above sea level.

• The Helios is expected to fly continuously for up to 6 months at a time on science and commercial missions.

• These two missions are expected to be completed by the year 2001 and will simulate flight based for future Mars aircraft design and missions.

• AeroVironment Incorporation of Monrovia, California developed the Helios prototype that is now being evaluated and expanded upon by the National Aeronautics and Space Administration ERAST project.

• AeroVironment also initiated the development of the Pathfinder, Pathfinder Plus, and Centurion, all are lightweight solar powered aircraft.
• Helios’s Specification:

• The solar cells that cover the entire upper surface of the Helios wing span doesn’t only power the electric motors during the day, but will also charge the on- board fuel cells that will power the aircraft during night flying.

• The fuel cell called an electrolyer will store the excess electrical energy generated by the solar cells as disassociated water molecules.

• Oxygen and hydrogen gases are accumulated in separate tanks. At night when the solar cells stop producing electricity, the oxygen and hydrogen gases are fed back into the fuel cell to produce water and electricity, for motor operations till the next morning when the charging process starts over again.

• The Helios will be flown via remote control by a pilot on the ground in a mobile van or in a fixed ground station that is equipped with full flight control capabilities and consoles for systems monitoring.

• 79-inch diameter laminar-flow propellers are used on each of the Helios’ "engines".

• A flight termination system that includes a parachute system deployed on command and a homing beacon to aid in aircraft location must be on board the Helios due to laws governing remotely piloted aircraft flown in military restricted airspace.

• During later flights, AeroVironment’s flight test team will evaluate new motor control software, which may allow the pitch of the Helios to nose-up or nose-down attitude in reaction to the horizon to be controlled entirely by the motors.

• If successful, production versions of the Helios could eliminate the elevators on the wing's trailing edge now used for pitch control, saving weight and increasing the area of the wing available for installation of solar cells.

• Aircraft like the Helios may be able to do work such as telecommunications more efficiently and at much lower cost than our current space based satellites. They could also monitor weather, track hurricanes, and provide coverage of disaster sites such as fires, mud slides, flooding and earthquakes in order to more precisely direct emergency resources.

• The Helios has made several low altitude practice flights, the most recent flights took place on September 8 and 29, 1999 for an hour and fifteen minutes each.

• High efficiency, average 21.5% at AM1.5 (sunpowercorp)

• Light weight

• Fabricated using very thin monocrystalline silicon wafers.

• The design incorporates front surface texturing and a double layer antireflection coating.

• Low fluence space missions

• Solar race vehicles

• And solar powered aircraft

• Standard cell size 7.031 x 3.124 cm (sunpowercorp)

• Standard area 21.96 cm2 (sunpowercorp)

• Specific weight 40 mg/cm2 (sunpowercorp)