AstroFlight Sunrise
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The AstroFlight Sunrise was an uncrewed
experimental An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...
electric aircraft An electric aircraft is an aircraft powered by electricity. Electric aircraft are seen as a way to reduce the environmental effects of aviation, providing zero emissions and quieter flights. Electricity may be supplied by a variety of methods, ...
technology demonstrator and the first aircraft to fly on
solar power Solar power, also known as solar electricity, is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Solar panels use the photovoltaic effect to c ...
. First conceived in November 1970, the Sunrise first flew on 4 November 1974 from Bicycle Lake, a dry lakebed on the Fort Irwin Military Reservation,
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,
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. The first prototype was destroyed on its 28th flight by turbulence. The improved Sunrise II flew the following year.


Development

While working as an engineer at
Hughes Aircraft The Hughes Aircraft Company was a major American aerospace company, aerospace and defense contractor founded on February 14, 1934 by Howard Hughes in Glendale, California, as a division of the Hughes Tool Company. The company produced the Hughes ...
, Roland Boucher began design work on an electric-powered aircraft concept in November 1970, calculating that the contemporary nickel-cadmium batteries available would be sufficient to sustain flight using a radio-control model glider. Early experimental projects proved the concept sound and in 1973 Boucher turned his attention to the creation of a high-altitude solar-powered aircraft that would have unlimited endurance. Boucher explained the project to his superiors at Hughes Aircraft in 1972 and after reviewing it, the company released the project to Boucher in 1973. Boucher took a leave of absence from Hughes to pursue the project and joined his brother, Bob Boucher, at AstroFlight, a small model airplane manufacturer in Venice, California. After successfully flying an electric drone carrying a payload on a
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adva ...
project for
Northrop Corporation Northrop Corporation was an American aircraft manufacturer from its formation in 1939 until its 1994 merger with Grumman to form Northrop Grumman. The company is known for its development of the flying wing design, most successfully the B-2 Spiri ...
, they then moved onto Project Sunrise. Using commercially available off-the-shelf solar cells producing only 10% efficiency, Boucher calculated that his project would need to be able to fly on about . The aircraft was envisioned as an uncrewed
sailplane A glider or sailplane is a type of glider aircraft used in the leisure activity and sport of gliding (also called soaring). This unpowered aircraft can use naturally occurring currents of rising air in the atmosphere to gain altitude. Sailplan ...
that would have an operating altitude of , powered by a single Samarium–cobalt magnet electric motor, the first motor of its kind in the world. The aircraft would use no batteries and, instead, would descend at night from its operating altitude to about at dawn, before solar energy was once again available for climb. Boucher saw the Sunrise as a proof of concept for a follow on aircraft that would be capable of remaining aloft for months at an altitude of . ''Project Sunrise'' was funded by DARPA commencing in January 1974 and administered by Lockheed Aircraft Corporation of
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, with the contract specifying a "proof of concept aircraft powered solely by incident sunlight on the wing surfaces." Roland Boucher took on the task of the structural design, aerodynamics, telemetry, control and navigation. He also designed the integration of the solar panel, electric motors, gearbox and the propeller. He selected an Eppler 387
airfoil An airfoil (American English) or aerofoil (British English) is a streamlined body that is capable of generating significantly more Lift (force), lift than Drag (physics), drag. Wings, sails and propeller blades are examples of airfoils. Foil (fl ...
for the wing. The solar cells were round commercial units provided by Heliotech. The actual airframe was constructed by a team under expert model builder Phil Bernhardt. The Sunrise's wing span was and the aircraft had a gross weight of . The
wing loading In aerodynamics, wing loading is the total weight of an aircraft or flying animal divided by the area of its wing. The stalling speed, takeoff speed and landing speed of an aircraft are partly determined by its wing loading. The faster an airc ...
was a very low 4 ounces per square foot (0.011 kg/sq m). The aircraft structure was built from spruce, balsa and maple. Due to their roughness the solar cells were only mounted on the aft two-thirds of the wing's upper surface. The wing spars were built from spruce spar caps with maple doublers at all attachment points and two balsa shear webs attached to balsa strips on the wing spars. The ribs were made from balsa. This construction resulted in a balsa spar box with tapered spruce caps. The leading edge was covered with balsa to form a leading edge D spar. The trailing edge was formed by two wide sheets forming a triangle with vertical spar sections in between the ribs. The covering was 1/2 mil
Mylar BoPET (biaxially oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical stability, dimensional stability, transparency reflectivity, an ...
. The span wing weighed and was capable of loads up to 100 pounds. Control was via an S & O Radio designed and built telemetry transmitter and receiver. The standard S&O six channel radio had channels for elevator, rudder, motor on and off and solar cell operating mode. The solar cells could be set for either series or parallel operation. The telemetry functions provided gave data on motor current, motor voltage, motor RPM, airspeed and two heading references from a sun compass for navigation.


Operational history

Flight testing commenced in 1974 at Bicycle Lake, California. The first flights were conducted on battery power, using a
bungee cord file:Bungee Cord PICT6882a.jpg, Bungee cords equipped with metal hooks A bungee cord (sometimes spelled bungie; also known as a shock cord or an ocky strap) is an elastomer, elastic cord composed of one or more elastic strands forming a core, usua ...
launch to . On its first flight the aircraft reached 500 feet, before returning for a landing. A lack of sunny days delayed flight testing, but in all, 28 flights were made. The Sunrise would climb slowly at first until its solar cells cooled down and their efficiency increased. On its 28th flight the aircraft was destroyed when it was flown too close to a cumulus cloud at about and the associated turbulence broke the aircraft's structure.


Aftermath

The success of the flights that had been completed allowed Boucher to state: DARPA and Lockheed proposed a follow-on design to the Sunrise to be powered at night by batteries instead of just gliding. Roland Boucher designed the second aircraft using higher efficiency solar panels that were more aerodynamically smooth. Roland Boucher had become physically exhausted from his work on the initial Sunrise and he suffered from
congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome caused by an impairment in the heart's ability to fill with and pump blood. Although symptoms vary based on which side of the heart is affected, HF typically pr ...
. He was admitted to intensive care at Santa Monica Hospital. While in hospital he resigned from AstroFlight and sold his interests in the company to his brother Bob Boucher who continued work on the second Sunrise aircraft. After recuperating, Roland Boucher returned to work at Hughes Aircraft on classified military programs. The Sunrise II first flew on 27 September 1975 from Nellis AFB, near
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.


Variants

;Project Sunrise Prototype #1 (Sunrise I) :Initial aircraft first flown in 1974 ;Project Sunrise Prototype #2 (Sunrise II) :1975 improved version for high altitude flight demonstration AIAA-84-1429 History of Solar Flight Robert J. Boucher


Specifications (Sunrise I)


See also


References

{{reflist, 30em


External links


Official website archives
on archive.org
Photo of Sunrise showing solar cells
Sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning, at the start of the Sun path. The term can also refer to the entire process of the solar disk crossing the horizon. Terminology Although the S ...
DARPA projects Solar-powered aircraft 1970s United States experimental aircraft Single-engined tractor aircraft Lockheed Corporation