“That’s Professor Global Hawk”
A remote-piloted warrior starts flying for science.
- By Kara Platoni
- Air & Space magazine, May 2011
(Page 2 of 3)
The team at Dryden received its first two demilitarized aircraft in 2007. NASA also acquired the last demonstrator, AV-7, in 2009. The fully re-engineered AV-6 has flown all of NASA’s science flights until last May, when AV-1 flew its first NASA test mission.
To train pilots on its three drones, NASA hired a pilot who had flown all of them. Tom Miller had logged some 1,500 hours flying Global Hawks, including with the flight test squadron at Edwards Air Force Base in California and later as part of Operation Enduring Freedom in Afghanistan. “It’s very cool to be asked to come back and fly them again,” he says.
Miller led training for the Pacific mission’s team and flew several of the missions himself. While some of the pilots had experience in manned high-fliers, like the U-2, none had previously flown a Global Hawk. Hall was the only one with a science flight background, having spent about 2,000 hours in NOAA’s Twin Otter.
Global Hawk pilots fly by desktop—in this case, from a brand-new ground station at Dryden dubbed the Global Hawk Operations Center. The center is divided into three compartments: a chilly lobby where air conditioners cool the giant stacks of computer hardware that keep the airplane flying, and two glass-encased rooms, both facing an enormous screen displaying a live camera feed from the aircraft. The pilots work out of the front room; in the back room sit more than a dozen payload operators, keeping their eyes on computer monitors as their instruments stream real-time data to them.
Global Hawk’s track is pre-planned; the aircraft flies on a scheduled airspeed and its bank angles are pre-set, although pilots can make mid-flight adjustments. “Typically—say, 75 percent of the time—we don’t stay on the canned mission plan because our mission objectives are usually things like weather and atmospheric phenomena, which move,” Hall says.
Pilots control the aircraft using four computer monitors, a keyboard, and a mouse. There’s no yoke—not even a joystick. Although they have a moving map that lets them track the aircraft’s progress over remote locations, there’s no feeling of motion. “You lose four of your five senses when you’re dealing with an unmanned vehicle,” says Miller. “You’re not in the airplane, so you don’t feel if the throttle comes back or you don’t feel it when it goes into a turn. Everything is based on sight, looking at the displays.” The pilots have no view out the aircraft’s window.
For the scientists, shifts can be long. Because some interesting bit of data could always come down the pipe, Newman says it was tempting to work long hours and late nights to get the data—“the scientific candy,” he calls it. He used to worry about ER-2 pilots flying over the Arctic: “If the engine flames out, if there is any problem with your ER-2, then you’re not getting that pilot or the plane back. There is no place to land up there, there are no runways, and it’s really brutally cold.” Now, he says, “I don’t have to worry about the pilots anymore—I have to worry about my own team and that they don’t drive off the road because they’re so tired.”
Because science and military missions have different objectives, NASA’s Global Hawk tried some new moves on its first two science flights. According to Chris Naftel, the Air Force had never taken a Global Hawk much past Fairbanks, Alaska, which is around 65 degrees north. Scientists want to get closer to the Arctic, a critical area for studying ozone depletion and other climate phenomena. On the Pacific flights, says Naftel, “we went up to 85 degrees—that’s about 300 miles short of the North Pole.” This is the farthest north a Global Hawk has ever flown.
Atmospheric scientists are equally interested in sampling near the equator, because that’s where greenhouse gases fountain up into the stratosphere before falling back toward the poles. For example, scientists would like to measure stratospheric water vapor—a greenhouse gas that is more insulating than carbon dioxide—to understand its effect on Earth’s surface climate.
But flying at high altitudes near the equator presents a risk: fuel freezing. “With our atmosphere, at 60,000 feet it’s actually colder at the equator than it is at the North Pole,” says Naftel. “The Air Force will fly around the equator for only about an hour, and now we have scientists that want to take eight or 10 hours of data there.” For such long-duration equatorial stays, NASA intends to take advantage of the Global Hawk’s heat exchange system, in which fuel is warmed through direct contact with the avionics equipment. The agency also hopes to utilize fuels that freeze at lower temperatures, says Naftel.
Ironically, one of the special requests scientists made during the Pacific mission was to have the high flier occasionally fly low. “We’re interested in other altitudes because some of the important things that we need to do are to take a cross-section of the atmosphere,” says Hall. “We’ll come down and loiter at a little lower altitude, maybe around 43,000 [feet] or so, and then go back up to altitude.”
The aircraft itself was also modified for the Pacific mission. While the Air Force had typically flown two sensing instruments, says Naftel, “we had 11 instruments on GloPac, and they were all over the place: some in the nose, some under the bottom, but some were on the back of the airplane, some on the sides of the airplane.” Northrop Grumman designed a modular honeycomb pallet system for two of AV-6’s payload areas that allowed instruments to be easily added or taken out and returned to the scientists for data analysis or repairs. Among the instruments flying on the demonstration mission: a cloud physics LIDAR (Light Detection And Ranging) instrument on the nose to profile dust and aerosols, ozone and water vapor samplers, and chromatographs for measuring greenhouse and ozone-depleting gases like nitrous oxide, methane, and CFCs (chlorofluorocarbon compounds).