NASA, in cooperation with Scaled Composites, LLC, is conducting a new phase of flight demonstrations of collision-avoidance systems to develop the ability of unmanned aerial vehicles (UAVs) to eventually fly routinely and reliably in the national civil airspace. Flights on a test range near Mojave, Calif., in early April are evaluating a Detect, See and Avoid (DSA) system that can identify non-cooperative aircraft without operating transponders. This follows a series of flight evaluations of a system to detect cooperative transponder-equipped aircraft conducted in March 2002 at Las Cruces, N.M.
The full potential of UAV systems cannot be realized until they demonstrate the ability to operate safely and routinely within the existing air traffic management system. NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program has sought to apply technology to scientific and commercial applications, particularly the mission to study the Earth's environment with high-altitude, long-endurance UAVs.
"NASA's interest is in getting UAVs to fly in national airspace as general aviation aircraft do today," said Glenn Hamilton, UAV subsystems project manager at NASA's Dryden Flight Research Center, Edwards, Calif. "We need to establish an equivalent level of safety for UAVs as manned aircraft have. Collision avoidance utilizing reliable Detect, See and Avoid systems is one of the critical technologies needed to enable UAVs to operate safely within the national airspace structure."
The surrogate UAV aircraft for the DSA tests is Scaled Composites' optionally piloted Proteus. For the current flights, Proteus is equipped with an Amphitech OASys high frequency radar system. Originally developed to warn low-flying helicopter pilots of power lines in their flight path, the 35 GHz (Ka band) radar is being used to detect any approaching aircraft on a potential collision course within a six nautical mile range, regardless of whether the intruder is equipped with an operating transponder. As a backup sensor, Proteus also is equipped with the Goodrich Skywatch HP traffic advisory system it used successfully to detect transponder-equipped aircraft at distances up to 35 nautical miles during last year's tests.
"We chose the Amphitech Ka band radar due to it being lightweight, low cost and having low power requirements," Hamilton added. "The demonstration is to see if it will work in this application. We're trying to find the lowest cost solution that will work."
Proteus and a variety of target aircraft, ranging from a hot-air balloon to a high-speed NASA F/A-18 jet, are flying a series of 22 different simulated conflict scenarios over several days. Flights are being conducted in a joint-use restricted test airspace zone northwest of Edwards Air Force Base, Calif.
During the flight demonstrations, Proteus is controlled remotely by a pilot in a ground station. Radar data is relayed to a ground station via either a line-of-sight telemetry link or an over-the-horizon Inmarsat satellite link, and the ground pilot then commands Proteus to change course as needed. To enhance flight safety and mitigate risk, a 500-foot "safety bubble," including a minimum 200-foot vertical separation, is being maintained throughout the tests and a pilot is on board the Proteus who can take control at any time.
Douglas Shane, Scaled Composites' vice-president of business development and Proteus' remote pilot for many of the test scenarios, noted that flight safety is taken very seriously.
"A big component of safety in these tests is the fact that all airplanes are piloted," he said. "They have humans with rules of engagement to ensure that we don't proceed into an area that might create a true conflict, or a true possibility of a mid-air collision. That's a big reason why the Proteus is a good developmental testbed, because you have that human backup looking out the window."
Russ Wolfe of Modern Technology Solutions, Inc., wrote the test plan for the current flight demonstrations, which he cited as "a very important step in proving enabling technologies for unmanned air vehicles."
"It's something that the FAA deems as essential. They will not approve a UAV to fly in the national airspace system without detect, see and avoid capability. This test, (along with) many in the future, will help to prove this enabling technology."
"One of the biggest impediments to getting routine access to the national airspace for unpiloted vehicles is the whole issue of see and avoid," Shane added. "That is one technology that is not mature yet, (and) that is critical in order for the FAA and the general public to accept an unpiloted airplane as being safe to operate...with all the others. We believe these tests are absolutely critical and fundamental to (enabling UAVs to have) routine access to the national airspace"
Based at Scaled Composites' facility at the Mojave Airport, the UAV collision-avoidance flight demonstrations brought together a team of pilots, engineers and technicians from NASA Dryden, Scaled Composites, Modern Technology Solutions, (MTSI), Amphitech International, New Mexico State University's UAV Technical Analysis Applications Center (TAAC) and the U.S. Navy Air Warfare Center (NAWC). NASA Dryden provided overall project management and two of the target aircraft. Scaled Composites provided the Proteus test aircraft and several of the intruder aircraft, as well as hardware and software development and the ground control station. In addition to developing the test plans and procedures, MTSI, based in Alexandria, Va., provided systems engineering and test coordination and will perform the post-test data analysis. Amphitech, headquartered in Laval, Quebec, Canada, furnished the 35 GHz OASys radar and engineering support. TAAC, based at the NMSU campus at Las Cruces, N.M., assisted with FAA airspace coordination. NAWC, China Lake, Calif., supported the integration of the Amphitech radar and the Skywatch traffic advisory system onto the Proteus.
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