The G Machine
Riding an Atlas into space was a piece of cake compared to pulling 32 Gs on the Johnsville centrifuge.
- By Mark Wolverton
- Air & Space magazine, May 2007
Courtesy Doug Crompton
(Page 3 of 3)
Not everyone was a “G monster” like Cloak. For Barry Shender, one go-round was enough, a routine familiarization ride that didn’t exceed a mild 3 Gs. “I’m not the roller-coaster-ride type,” he admits. Centrifuge engineer Bill Daymon was another one-timer, although in his case the purpose of the ride wasn’t familiarization but basic troubleshooting. “People were hearing noises, and I took a 3-G ride to listen to it,” he recalls. “That was my only ride. The year before I had had bypass surgery, and they were rather reluctant to let me ride it again.”
Subjects generally rode the centrifuge in one of two modes: closed-loop, or dynamic flight simulation, in which the rider had full control over the movements of the centrifuge; and open-loop, or “meat in a seat,” in which the rider was essentially a lab rat at the mercy of the researchers. Riders were usually given various tasks to perform under the G stresses, such as flying simulated combat missions and other activities demanding certain cognitive or motor skills. Doctors monitored all test subjects at every moment, and both the subject and the doctors had the capability to immediately stop the ride. It’s a testament to the Johnsville researchers that no one was ever seriously injured riding the centrifuge.
Despite the discomfort and dangers, willing volunteers were never in short supply. “You have to give a lot of credit to the folks that volunteer to do it,” Shender says, “because basically we beat them up every day, and they come back.” So why did they clamber into the belly of the beast? “Motivations like I want to see what I can do physically. I want to do something that would make good stories. I want to do something that’ll get me out of the office today.” Subjects could also score a souvenir. “If they like, we give them a video of their experiences in the centrifuge so they can show their family and friends when they lose consciousness and how silly they looked.”
The centrifuge research has had a lasting impact on the training of military pilots, the development of anti-G suits and techniques, and the design of aircraft and spacecraft systems. Aside from the biomedical effects of high Gs, the Johnsville researchers investigated practical problems, including the disorientation of Navy pilots following night catapult launches from a carrier, and spin recovery techniques in fighter aircraft such as the F-4B Phantom and F-14 Tomcat. Such projects used the centrifuge’s flight simulation capabilities to full effect. Sometimes the centrifuge was used to re-create the conditions of puzzling crashes that might indicate aircraft design flaws.
The last decade of operations at Johnsville saw one of the centrifuge’s most important contributions. “Back in the ’90s there was a mandate from Congress that everybody should be able to go into the tactical cockpit, boys and girls, small people, big people,” says Shender. “We developed what we called the Gender Neutral Study, where we wanted to ask the question: What happens if you’re a small female and you get put into one of these high-performance jets? Can you fly? Can you eject? Can you hold your head up?” As it turned out, women can more than hold their own against the flyboys. “We established that they can certainly fly high-G maneuvers without any difficulty, and certainly [have] comparable acceleration tolerance with the men,” says Shender. “These female subjects had a good time doing it. And they didn’t complain nearly as much as the male subjects do.”
In 1996 the Warminster base fell victim to the Base Realignment and Closure Act, and the Naval Air Warfare Center moved to the Navy’s Patuxent River facility in Maryland, leaving the centrifuge behind. Veridian Corporation, a private contractor, kept it spinning for mostly Navy programs for a while, but by 1999 mounting costs forced the wheel into retirement. Although centrifuge work continues at other military and NASA centers, “we’re sort of gearing down,” Shender says regretfully. The center of the action appears to be shifting overseas, with new centrifuges in Sweden and Japan. None measures up to Johnsville in capabilities or sheer engineering chutzpah.
As for the Johnsville centrifuge, proposals for its future use range from the sedate, such as turning the facility into a museum, to the outlandish, such as turning it into a thrill ride—an unlikely scenario, given that the deaths of two riders on Epcot Center’s “Mission: Space” simulator were linked to G-induced stresses. Shender and Cloak continue their work in acceleration science at the Naval Air Warfare Center at Patuxent River, while veterans of the center like Bill Daymon meet at reunions to trade war stories. Regardless of whether the Johnsville centrifuge ever spins again, its legacy in aerospace history—and in the memories of all who rode it—is secure.