In a world ravaged by economic meltdown, weather catastrophes, oil price war, refugee crisis, terror attacks in Europe, Syrian conflict, Panama Leak, the Solar Impulse project is a sigh of relief from everything that is going down. Bertrand Piccard and Andre Borschberg took on the near impossible task to themselves of flying around the globe in a solar powered airplane: the Solar Impulse 2.
As Piccard set off from Hawaii for a 62-hour flight to San Francisco, California, the project was considered as an act of defying the realms of possibility. Certainly, in comparison with Solar Impulse 2’s last flight, the current trip seemed unremarkable. Back in June 2015, Borschberg flew 4,481 miles from Japan to Hawaii, which took around 117 hours and 52 minutes. It was the longest ever solar-powered flight both by time and distance, as well as the longest solo flight for any aircraft. It took almost 255 hours and 20,000km.
“Since the size of the cockpit allows only one person, when the weather conditions are right, the only restraint on how long the plane can fly is the pilot himself”
Flights like these are possible for Solar Impulse because of its design: it has a wingspan the size of a Boeing 747 covered in more than 17,000 solar cells; a cockpit size of a small car with a power output of a motorbike. The solar cells power four electric motors and charge four lithium-ion batteries during the daylight hours. The plane soars to the height of 39,000ft during the day before cutting its cruise speed from 49 knots to 33 knots to save power and slowly descending through the night until the sun comes up again.
Since the size of the cockpit allows only one person, when the weather conditions are right, the only restraint on how long the plane can fly is the pilot himself. The pilot takes 20 minute nap and perform yoga to stay limber.
The military have long been aware of a future when solar planes will soar. Unmanned drones like the Global Hawk have a flight durability of more than 30 hours, but as far back as 1983 an unidentified U.S. intelligence agency commissioned work on a classified drone known as HALSOL (High ALtitude SOLar) which would extend flight time to weeks.
“Unmanned drones like the Global Hawk have a flight durability of more than 30 hours”
The solar technology of the 1980’s was not up to the task, but HALSOL was later revived by the Ballistic Missile Defense Organization (BMDO). Under a project called Raptor/Talon, BMDO envisioned a fleet of long-endurance drones circling enemy territory, ready to shoot down ballistic missiles with miniature Talon missiles. Again, the technology was not developed enough. In 1993 HALSOL was declassified and turned over to NASA.
NASA continued development of solar aircraft in association with plane maker AeroVironment. In 2002 they established how a solar aircraft could act as a “communications satellite” from sixty thousand feet, broadcasting a television signal and carrying communications.
The Pentagon’s latest solar development is the Zephyr, designed by QinetiQ North America under a $44 million contract. This 70-pound drone has unofficially broken endurance records with a three-and-a-half day flight, but the ultimate goal is flying for three months at a time. QinetiQ brags Zephyr’s low cost and long endurance are ideal not just for military but also for civilian missions, such as disaster relief, ocean monitoring and weather research. The Zephyr could even act as a communication relay, bringing instant broadband network capability.
“NASA continued development of solar aircraft in association with plane maker AeroVironment. In 2002 they established how a solar aircraft could act as a “communications satellite” from sixty thousand feet”
Pegasus, a European solar aircraft partnership, has even more potential, suggesting applications including pipeline checking, flood management, urban mapping and forest fire risk assessment; all that’s needed is for the technology to grow. And judging from Solar Impulse’s test flight, solar aircraft technology is coming along nicely.
