Solar Flight #2: The Boucher Sun Plane

We launch this series on solar flight by introducing Roland and Robert Boucher, an innovative and visionary twosome that John Perlin refers to as “the Wright Brothers of solar aircraft.” The year was 1974 when their Sunrise 1, the first solar plane, took off.

Meyers: I’d like to know more about the Bouchers. How did you first learn about them?

Perlin: I met them at a party the evening before the launch of the solar-winged aircraft, the Helios, at Edwards Air force Base. All the pioneers of solar flight were there including the Bouchers. I learned about a whole new world that night – everyone attending, except for me, seemed somehow involved in human and/or solar flight. It was the densest crowd of creative geniuses that I had ever schmoozed with. I just asked questions and listened to their stories. Da Vinci would have envied these men who realized what he could only dream of.

Meyers: How were the Bouchers drawn to aviation in the first place?

Perlin: Like all the rest at the party, they had an aviation background and like the rest, as the reader shall see, contributed earlier in the development of human-powered or solar flight.

Meyers: I understand the Bouchers first attempted to win a defense contract flying a battery-powered spy plane.

Perlin: The Bouchers argued that an electric reconnaissance aircraft could achieve a stealthiness unmatched by gasoline-driven aircraft of the day whose exhaust left a thermal footprint easily picked up by radar and whose noise could be easily heard overhead. And they succeeded, flying in 1972 an electric-powered flying-wing that carried a six-pound load simulating surveillance gear or more than an hour at speeds up to 75 miles per hour.

Meyers: Were any others thinking about electric-powered flight at that time?

Perlin: Very few. As a later admirer of the Bouchers confessed, “Like so many people, I once had a subconscious block about electric flight.” Those in charge of defense contracts showed little interest, arguing successfully that gas-run planes could stay up longer and dismissed the attempt at electric-powered surveillance planes as “crazy.” They did not entirely dismiss the Bouchers’vision, though. If the Bouchers could get the flying time up to 12 hours, the defense people let the brothers know, there would be interest in funding such an endeavor.

Meyers: So what did the Bouchers do?

Perlin: They badly needed a technological breakthrough to move forward. Batteries alone wouldn’t cut it, as they would give out after three or four hours. Their salvation came serendipitously. Just in time, solar cell manufacturer Heliotek announced a major advance in solar cell efficiency so the power density would be equivalent to the batteries that ran their all-electric plane. They thad no doubt that a plane using the Heliotek cells would fly. The unsolved problem was storage. If they could somehow store enough solar energy during the day and run on it throughout the night, the plane could fly forever. But no suitable battery was available at the time. But Roland Boucher came up with a viable alternative – use the energy in the earth’s gravitational field as storage. In layman’s terms this meant having the plane climb high enough in the sky during the hours of daylight on solar power to allow for gliding throughout the night and then repeat the cycle day after day.

Meyers: Were there any takers on this vision?

Perlin: Interestingly, there were. The new plan piqued the interest of ARPA – Advanced Research Projects Agency – the military’s top research and development group in the early 1970s.

Meyers: So much so to fund them?

Perlin: Yes. They provided funding for the Bouchers to build the world’s first solar plane.

Meyers: Please describe how this prototype solar spy plane was built and where it was built.

Perlin: It was constructed out of spruce, weighed 22 pounds, and had a wing span of 32 feet with 4096 cells of 14% efficiency attached to 2/3 of the wing surface and capable of generating from sunlight 400 watts. The solar aspect added 6 ½ pounds to the plane.

Meyers; So, did the plane fly?

Perlin: The plane, named Sunrise, was ready late in the fall of 1974 for its first solar-powered flight. This meant testing the plane in potentially bad weather, as the rainy season begins in California at this time. And the forecast suggested a particularly wet and windy season that year. The Bouchers therefore argued with ARPA to test the Sunrise in Australia where summer was approaching or wait until the coming spring in California. ARPA rejected both scenarios and ordered them to fly the aircraft at the earliest possible date. Acceding to their funder’s orders, Sunrise’s maiden voyage began at 10 am on November 4, 1974. The plane rose slowly and silently above the California desert. The age of solar flight had begun.

Coming next: Solar-powered human flight.

Article based on archival research by John Perlin, author, Let It Shine: The 6000-Year Story of Solar Energy
Image: Project Sunrise