A-10 Thunderbolt Turn into Storm Chaser

On the battlefields of Iraq, the U.S. military’s A-10 Thunderbolt jet Was a fearsome tank killer able to survive punishing hits from antiaircraft fire. Now, one retired Thunderbolt is taking on a new scientific mission that fits its nickname.

The National Science Foundation (NSF) has given a $ 10.9 million grant to a U.S. Navy university to transform the warplane into an aircraft capable of withstanding stomach-chuming winds, pounding hail, and lightning strikes as it probes the heart of heavy weather. The tubby Thunderbolt—also dubbed theWarthog—“may not be a thing of beauty, but we expect that the data that it collects will be,”says Brad Smull, a program director in NSF ’s Division of Atmospheric and Geospace Sciences. “It turns out that being able to survive wartime flak has a lot in common with being able to handle a strong storm.”

The grant, made 23 September, caps a 6-year effort to replace a propeller-driven T-28 military trainer that was grounded in 2005 after 35 years of storm chasing. That plane, based in South Dakota, collected data on everything from wind speeds and water vapor to electrical currents and dust particles. But atmospheric researchers had long wanted a plane that could carry more instruments, fly higher, and stay inside storms longer than the T-28.

After years of considering the options, experts pinpointed the A-10, a heavily armored, slow-flying jet developed in the 1970s to support ground troops. Air Force officials initially were cool to the idea of giving scientists a spare plane. But they warmed up once NSF arranged for another part of the military, the U.S. Navy’s Naval Postgraduate School in Monterey, California, to acquire and operate it. The school’s Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) already operates aircraft for NSF and other government research agencies.

The Thunderbolt, currently mothballed at a desert storage facility in Arizona, “will be completely taken apart and put back together for us,” says CIRPAS manager Robert Bluth. Mechanics Will also remove the Thunderbolt’s lethal, nose-mounted 30-millimeter cannon, creating “just a huge area for scientific instruments,” says NSF ’s James Huning, who has been coordinating the conversion. The plane also has plenty of “hard points” under the Wings that, instead of holding missiles and bombs, will eventually carry sensors and instrument pods. NSF expects to spend a total of $ l 3 million on the conversion.

Airborne instruments play a key role in scientists’ efforts to understand and predict storms. Although researchers have long studied storm dynamics using ground-based radars, weather balloons, and aircraft that can fly above or below bad Weather, “you really have to go right into the storm to get the most useful data,” says meteorologist Terry Schuur, who Works at the National Oceanic and Atmospheric Administrations National Severe Storms Laboratory in Norman, Oklahoma. And just a select few aircraft are capable of penetrating the interiors of big convective storms, such as thunderstorms, that churn with enormous energy.

The new plane’s capabilities are a wish come true for many atmospheric scientists, who will begin submitting proposals to NSF sometime next year. Schuur, for instance, wants to take advantage of the Thunderbolt’s ability to attain an altitude of 11 kilometer (compared with 7 kilometers for the old T-28). That extra height means it can reach into the icy, supercooled tops of giant, anvil-shaped thunderheads and collect real-world data to improve computer models of how hail forms. (In tests, the A- l 0’s engines were able to “inhale” nectarine-sized hail “and just keep going,” NSF’s Huning says.)

Another target could be the mysterious flashes of high-energy gamma rays associated with some storms and the “gamma glow” they leave behind, says physicist David Smith of the University of California, Santa Cruz. The Thunderbolt should be “able to take our [gamma ray] detector right into the heart of a storm and stay there a while,” he says. And its relatively slow flying speed—about 550 kilometers per hour—means “we’ll get much higher quality data. The slower the better, because you are in the hot spots longer.”

The A-10 ’s longer range and ability to linger in storms for up to 3 hours—compared with about an hour for the T-28—is a big plus for cloud physicist Sonia Lasher-Trapp of Purdue University in West Lafayette, Indiana. She studies how “warm rain” gets started in convective clouds and then interacts with colder water, ice, and aerosols as storms form. “Having more time on station per flight will be wonderful,” she says.

The A-10 will be able to do more than just probe severe thunderstorms, Smull notes. The plane’s ability to fly low will make it a good choice for long runs over oceans to study air-sea interactions. Its ability to shoulder heavy loads means it could ultimately carry radar, lidar, and other imaging systems that would “make it an exceptional Earth-observing platform,” Smull says.

Scientists aren’t the only ones excited about the new plane. A number of former A-10 pilots are eager to get into the single-person cockpit, Huning says, even though storm chasing “can bounce and bruise the pilot a bunch. One even passed out.” NSF hopes to have the Thunderbolt heading into thunderstorms by early 2013.

SOURCE : SCIENCE MAGAZINE 11 NOVEMBER 2011