September 03, 2012
Credit: LOCKHEED MARTIN
Innovation is by its very nature a strange process in which the only certainty is an unpredictable outcome. Take, for instance, the strange case linking the early Russian rocket pioneer Konstantin Tsiolkovsky, with the first outdoor tests this year of a laser-powered aircraft in California.
In 1895, inspired by the sight of the recently erected Eiffel Tower in Paris, Tsiolkovsky conceived the idea of a free-standing tower reaching from the Earth's surface to geostationary orbit. During the 20th century, the idea became better known as the space elevator and by the mid-2000s had sparked sufficient interest for NASA to sponsor a series of Space Elevator Games. Launched as part of the NASA Centennial Challenges program, the games were designed to foster technologies that could one day be used in a space elevator, but which were also applicable to nearer-term NASA programs.
One of the key technologies was the power-beaming system, which transmitted laser energy to the “elevator.” The contest, with a prize of almost $1 million, was won in 2009 by LaserMotive, headquartered in Kent, Wash. The company had been founded just three years earlier by laser propulsion expert Jordin Kare and Tom Nugent, former director of research for LiftPort Group.
LaserMotive clinched the prize by using a complete power-beaming system to propel a robotic climber to a height of 3,280 ft. (1 km) up a tether suspended below a helicopter. Not only was this the longest distance ever achieved for laser power beaming, but it came at the fastest speed of 3.97 meters (13 ft.) per second and with the most power transferred to a receiver: over 1 kw.
Winning the event, held at NASA Dryden Flight Research Center at Edwards AFB, Calif., was LaserMotive's big break, says Nugent. “We were the only team to make it across the finish line—but beyond the prize money, the publicity was huge.” Nugent had been working on the space elevator concept for several years and “reached out” to Kare to help perfect the idea in the run-up to the contest. “It was a convenient focal point, and provided a trigger for what happened after,” says Kare.
Despite his longtime enthusiasm for the novel transport concept, Nugent says he reluctantly “came to the conclusion that a space elevator is not going to be built on Earth in my lifetime. However, there are other applications for this wireless power via laser technology.” One of these is beaming power directly to UAVs, a role that is currently being tested with the Lockheed Martin Skunk Works somewhere in the desert Southwest U.S.
Under the tests, LaserMotive fed laser power to a small Stalker UAV fitted with a lightweight photovoltaic receiver and onboard power management system. The evaluation demonstrated net positive power in flight at ranges up to 600 meters. The addition of the laser receiver did not impact its normal flight operations or aerodynamics during the tests, which were conducted over different conditions at day and night. LaserMotive says the beam director tracked the receiver for long periods, with centimeter accuracy at 500 meters, despite turbulence and aircraft maneuvers.