Solar powered aircrafts

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"Helios was drowned in the ocean by his uncles the Titans, after what he rose to the sky where he became the sun god."
(Greek Mithology)

August 13, 2001 - The Helios Prototype aircraft during initial climb-out to the west over the Pacific Ocean. July 14, 2001 - The Helios Prototype flying wing is shown near the Hawaiian islands of Niihau and Lehua during its first test flight on solar power from the U.S. Navy's Pacific Missile Range Facility.

HELIOS solar powered aircraft
(source/copyright: NASA Dryden Flight Research Center)

HELIOS project was a part of NASA's ERAST programme (Environmental Research Aircraft and Sensor Technology). It was developed by NASA and Californian company AeroVironment Inc. ERAST programme develops pilotless solar powered airplane technology. The HELIOS construction is based upon its predecessors like NASA's solar plane Pathfinder, which was successfully tested a few years prior to HELIOS. Due to its speed HELIOS was able to flew over the same spot for days or weeks, therefore, in the future such aircrafts could substitute communication satellites. In the test flight on 13^th August 2001, HELIOS reached the height of almost 30,000 meters. HELIOS was a slow airplane - if you ride a bicycle fast, you are quicker than HELIOS. It was a remotely controlled plane with no crew weighting less than most cars. However, it flew higher than any other plane powered solely by solar energy.


HELIOS - technical data	HELIOS - history in brief
Wing span: 75,3 m Length: 3,6 m Wing thickness: 0.3 m Height: 2 m, without upper blades of the propelers Wing area: 186.6 m² Mass: 600 kg - unloaded plane Allowed mass: up to 930 kg, depends on flight purpose and available energy. Cargo: up to 330 kg, depends on measurement equipment weight. Propulsion: 14 DC brushless electric motors (the power of each motor is 1,5 kW) with two blades, specialy designed for high altitude flights. The weight of each motor is less than 5 kg. Length of both propeller blades is 1,7 m. Energy source: Bifacial solar cells - dimmensions 1.25" x 2.75" (Front side efficiency 22 %, backside efficiency 11 %) placed on transparent wings. Energy source in the dark are lithium batteries. Fuell cells will be used as main energy source in the dark in the future. Speed: Typical flight speed is 30 to 40 km/h. The highest speed is 270 km/h. Flight height: Maximal flight height is 30000 m - typical height depends on flight mission and it is typical 15000 to 22000 m. Flight: The anticipated authonomy in the future together with fuell cells will reach for uninterupted flights (several months of authonomy). Materials: All main parrts of the plane are made of carbon fibres and styrofoam. Wings are covered with special designed and produced plastic sheet. Flying wings - From Pathfinder to Helios All Pictures and descriptions: NASA Dryden Flight Research Center	Gossamer Albatros > Gossamer Penguin > Solar Challenger

	Gossamer Albatross is best known for completing the first completely human powered flight across the English Channel in 1979. The Albatross II was the backup plane for this flight. It was equiped with a DC battery-powered electric motor and flight instruments for the NASA research program. NASA completed its flight testing of the Gossamer Albatross II in April, 1980. More about the "Father of Human Powered Flight" Dr.Paul Mac Cready...

	HALSOL > Pathfinder

	Pathfinder was a solar-powered, remotely piloted flying wing aircraft used to demonstrate the use of solar power for long-duration, high-altitude flight. Solar arrays provided up to 8 kW of power at high noon on a clear summer day. Pathfinder flew at typical airspeeds of 25 to 35 km/h. Pathfinder had a 30 m wing span, weighed 270 kg and was powered by six DC electric motors. It was built primarily of composites, plastic, and foam.

	Pathfinder Plus

	In 1998, Pathfinder was modified into the Pathfinder Plus aircraft. Major activities of Pathfinder Plus's Hawaiian flights included detection of forest nutrient status, forest regrowth after damage caused by Hurricane Inki in 1992, sediment/algal concentrations in coastal waters, and assessment of coral reef health. Pathfinder Plus has a 36 m wing span and weighs about 318 kg. Pathfinder Plus has eight DC electric motors, its solar arrays produced about 12,5 kW of power.

	Centurion

	Centurion has a 62 m wing span and it is powered by 14 brushless DC electric motors. The Centurion first flew in 1998. As with the Pathfinder/Pathfinder-Plus vehicles, the Centurion was further modified with the addition of a wing extension and a fifth landing-gear pod. Solar arrays have provided up to 31 kilowatts of power at high noon on a summer day to power the aircraft's motors, avionics, communications and other electronic systems. Centurion also has a backup lithium battery system.

In the future, such planes will also be used for interesting research purposes and missions, such as:

Fly through the volcano for the purposes of volcano plume study
Fly over the North and South Poles
Fly for weeks and months at a time collecting scientific data, which varies according to the sun position or the season of the year
Explore conditions on Mars

More than 60,000 high efficiency (22.5% at AM 1.5) solar cells produced by SunPower Corporation were used as an energy source for HELIOS. The peak power of solar cell array was approximately 30 kW. The total costs for HELIOS solar cells reached around US$ 9 million (200 US$/W). HELIOS was equipped with 14 propeller motors, which were purposely designed for use in very thin air on high altitudes. HELIOS' wings (in fact, there's only one wing) were longer than wings of a Boeing 747 or a Lockheed C-5 military transport plane.

HELIOS flight, August 13, 2001, Photo Carla Thomas; NASA Dryden Flight Research Center Photo Collection

August 13, 2001 - NASA's Helios Prototype aircraft taking off from the Pacific Missile Range Facility, Kauai, Hawaii, for the record flight

August 18, 1999 - Closeup of the Helios Prototype on lakebed

HELIOS protoype closeup on the lakebed, August 18, 2001, Photo Tom Tschida; NASA Dryden Flight Research Center Photo Collection

HELIOS flight, August 13, 2001, Photo Carla Thomas; NASA Dryden Flight Research Center Photo Collection

August 13, 2001 - The Helios Prototype aircraft at approximately 10,000 feet flying above cloud cover northwest of Kauai, Hawaii.

July 14, 2001 - The Helios Prototype flying wing is shown moments after takeoff, beginning its first test flight on solar power from the U.S. Navy's Pacific Missile Range Facility in Hawaii.

HELIOS test flight, July 14, 2001, Photo Nick Galante; NASA Dryden Flight Research Center Photo Collection

Solar powered aircrafts - related web sites

SunPower Corp. - high performance low cost solar cells. The company conducts its main R&D activity in Sunnyvale, California and maintains a pilot line for solar cells in Round Rock, Texas.

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NASA Dryden Flight Research Center - The Dryden Flight Research Center, located at Edwards, California, is NASA's primary installation for flight research.

NASA Dryden Flight Research Center - Photocollection.
NASA Dryden Flight Research Center - HELIOS Solar Plane Factsheets.

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Webmaster's choice - comprehensive photocollection and interesting factsheets about solar powered aircrafts.

Literature and more information

NASA Spaceplace.