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 2 of 3)
Some people not only tolerated the centrifuge, but strove to test its limits—and their own. “Things were different in the ’50s and ’60s,” Shender says. “You could wake up in the morning and think, Let’s do something crazy today, and then do it.”
In August 1958 Navy Reserve officer Carter C. Collins rode the wheel to more than 20 Gs for a record 54 seconds. Later that day, R. Flanagan Gray, a civilian psychologist, repeated the feat. A year later, Gray would go on to greater fame as the first man to ride the “Iron Maiden,” a project that began with a rather odd idea about counteracting G forces.
“I think it started when somebody spun a fish and didn’t notice anything irregular about the fish because of the high Gs,” says Stephen Cloak, a Navy research engineer and veteran centrifuge jockey. “So they postulated that if we put a human encased in water, it would dissipate the G forces and they could take high G.” The Maiden was an aluminum capsule designed by Gray, sculpted roughly in the shape of a seated human, that could be filled with water. Gray stayed alert throughout the 25-second run up to 32 Gs, suffering only mild sinus pain. “He was another one of these late ’50s, early ’60s guys that just kind of kicked the tires and went at it,” says Cloak. Gray wanted to go to the full 40-G capability of the centrifuge, but the Maiden was too big to fit inside the gondola and so had to be mounted farther inward along the arm, where 32 Gs was the maximum acceleration possible.
In the late 1950s, two scientists, Carl Clark and James Hardy, had a more daring idea. Physics dictated that if a spacecraft could be steadily accelerated at 2 Gs, it could reach the moon or Mars in days or even hours. But could a human being survive the constant acceleration? Clark used the centrifuge to find out.
“He essentially moved into the cab, brought his La-Z-Boy from home, and stayed in there at 2 G for 24 hours,” says Shender. Clark slept, ate, worked, and lived at two Gs for a full day under constant medical surveillance. He suffered nothing more than fatigue. Further marathon rides were planned, but more immediate space missions loomed and the idea was set aside.
One factor that eventually discouraged the sportier research projects was the mounting evidence of all that could happen to the body under acceleration. Under high Gs, Cloak explains, “you’re insulting the brain with a lack of oxygen in the blood. Each person’s brain is a little different, so you don’t know what’s going to happen.” Aside from G-LOC (for “G loss of consciousness”), possible effects included motion sickness, disorientation, anxiety, euphoria, and confusion. Cloak adds, “You get swelling of the feet and ankles, ruptured blood vessels in the groin area, blood clots, temporary change in blood-flow patterns in the lungs, possible collapsing of the lungs, fractured ribs, chest pain. For your heart it’s entirely possible to have arrhythmias, transient electrical changes, myocardial infarctions, interesting little things like that.”
Most of these effects were transient and fairly rare, but they were not to be dismissed. “We had to go through a battery of exams,” Cloak recalls, “because one of the major risks is sudden death. No matter how well they screen you, you just don’t know when you get in there if a 9-G ischemic insult to your system is gonna kill you or not.” Then there are the mild phenomena, such as petechial hemorrhaging. “You actually look like you’ve got measles—at high Gs, blood leaks through the blood vessels and you get little pinpoints all over. It’s kind of interesting, especially the first time you see it.”
Cloak rode the centrifuge routinely throughout his career at Warminster as an acceleration researcher. “I used to tell everybody it broke the week up,” he says with a laugh. He adapted quickly: “135 rides later, it was just like getting up and walking around. You get so used to it.” He became such an expert rider that he ended up teaching anti-G techniques to Navy fighter pilots.