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
To test human responses to G forces, the Navy put subjects in a 10- by six-foot oblate steel sphere at the end of a 50-foot arm. Courtesy Doug Crompton
John Glenn called it a “dreaded” and “sadistic” part of astronaut training. Apollo 11’s Michael Collins called it “diabolical.” Time magazine referred to it as “a monstrous apparatus,” a “gruesome merry-go-round,” and, less originally, a “torture chamber.”
The Johnsville human centrifuge—the machine everyone loved to hate—was operated by the Navy at its Naval Air Development Center (later the Naval Air Warfare Center) in Warminster, Pennsylvania, just outside Philadelphia. For almost 50 years—it ceased government operation in 1996—the centrifuge was the world’s most powerful and versatile tool for studying the G forces that are an inescapable part of flight.
In his 2006 book Getting off the Planet: Training Astronauts, Randall Chambers notes, “Very early in the space program, amusement park rides were considered as possible research vehicles to study acceleration forces.” But Chambers, the scientist who trained all the early astronauts, soon realized that such machines wouldn’t take the extreme forces and sustained abuse needed to conduct serious studies on humans. A high-performance centrifuge, a machine that could produce high acceleration and thus high G-forces by rapid rotation, was the only solution.
By July 1950, inside a giant round 11,000-square-foot building at its Johnsville facility, the Navy had completed the world’s largest centrifuge, which consisted of a 10- by six-foot oblate sphere steel ball, or gondola, at the end of a 50-foot arm. (The oblate sphere gondola was later replaced with a 10-foot-diameter sphere.) A 4,000-horsepower electric engine at the other end whipped the arm around a huge chamber. The dual-gimballed gondola, mounted to the arm on rotating bearings, allowed the test subject to be oriented in various positions relative to the applied G force. This enabled the centrifuge to be used as a “dynamic flight simulator,” capable of accurately reproducing the sensations experienced by pilots in various flight maneuvers. Researchers reveled in the opportunity to study G forces under controlled conditions at levels previously accessible only in high-performance aircraft. Simply by turning the gondola as it spun about the arm, experimenters could subject pilots to positive Gs (“eyeballs in,” with acceleration in a head-to-foot direction), negative (“eyeballs out,” foot-to-head, similar to a rapidly descending elevator), transverse (chest to back), and practically every other variation that might be experienced during flight.
The Johnsville centrifuge rose to stardom at the beginning of America’s space program. It started operating with the training of pilots for the North American X-15 hypersonic aircraft and hit its stride with the Mercury manned spaceflight program.
“We were really worried about what was going to happen when we started spaceflight,” says Barry Shender, a biomedical engineer and specialist in acceleration stress who worked at Johnsville. The centrifuge’s flight simulation capabilities made it possible to reproduce all the ways various spaceflight scenarios could affect astronaut performance. “We did the early Mercury training of John Glenn and [Wally] Schirra and all the rest of those guys just to learn what happens if we go up to these sorts of accelerations in these different vectors,” Shender says. “We were talking about reentry and during takeoff, long-term exposures. So if we’re going to develop these ballistic profiles, how much can people take? It was a great unknown.”
For the Mercury, Gemini, and Apollo astronauts, the “wheel” was both a rite of passage and an invaluable training tool. “Whirling around at the end of that long arm, I was acting as a guinea pig for what a human being might encounter being launched into space or reentering the atmosphere,” Glenn recalled in John Glenn: A Memoir. “You were straining every muscle of your body to the maximum…if you even thought of easing up, your vision would narrow like a set of blinders and you’d start to black out.”
One objective of such ordeals was to teach an astronaut to counteract the G demons by using breathing techniques and muscle contractions. Michael Collins recalls in his 1974 autobiography Carrying the Fire: “If you breathe normally, you find you can exhale just fine, but when you try to inhale, it’s impossible to reinflate your lungs, just as if steel bands were tightly encircling your chest. So you have to develop an entirely new method, keeping the lungs almost fully inflated at all times, and giving rapid little pants ‘off the top.’ ”
Related topics: Astronautics Astronauts Space race
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Comments (11)
Good Day:
My father was Reuben Flanagan Gray. I'd like to correct a couple of facts that are incorrectly stated in the article above. First, the poor gold fish was seriously hurt in his/her ride on the centrifuge. He could only swim upside down and died after a couple of days. I know because my Dad brought him home after his "ride". Dad often brought home animals after their brutal experiences at Johnsville to see if they could become pets and live out thier lives happily. It never worked out. This type of animal testing would not go on today.
Dad's injuries on the day that he achieved 35 Gs were a bit more than minor sinus pain; he also received a hernia and an eye injury that inhibited his vision for the rest of his life. I clearly remember the black government car bringing him home that day; he could barely walk into the house.
I wish he had lived to have a PC. Until the day he died he was doing research at his home. There were always charts all over the walls and he would manually update them daily. He would have loved the internet and excel!
For me, his most notable contribution was his kindness to all and tolerance of everyone's differences. He was a wonderful father and I still miss him often.
I loved reading this article about Johnsville and the centrifuge as I learned much during my visits there and feel as if I lived this part of history along with others who are not mentioned here, but should be. Mr. Dick Crosby, a good friend of my Dad, will remember much more than I do as he worked with Dad in his research.
Thanks very much.
Posted by Susanne Gray Lawton on March 14,2009 | 01:34 PM
As the younger sibling of Susanne, I don't remember the goldfish but I do remember the goat. I have to agree that experimentation on animals was horrendous and I would certainly hope that that type of experimentation would not go on today! However, I will say that my father experimented on himself as much as the animals. In this way, he contributed greatly to the safety and the possibility of human beings withstanding high Gforces and the exploration of outer space.
I remember him for his great kindness and patience.
Thank you, Penny Gray
Posted by Penny Gray on March 20,2009 | 08:37 PM
My ancestor (g-g-grandfather) was Reuben Flannigan Gray, born in 1811 in S.C. He was an MD. He later moved to Lake Charles, LA. Are we kin?
My father, Hurst Gray Bowers,his g-grandson, was very involved with the Air & Space Museum. He died in 2004.
Posted by Laura Foreman on March 31,2009 | 03:09 AM
Dear Susanne Gray Lawton and Penny Gray,
I am an engineering professor at West Virginia University with a long interest in space flight and centrifugal forces. Although I doubt that we are related, I am fascinated by what little I have learned about the accomplishments of your father, and I have a notion that I might like to write his biography. Please contact me if you would like to discuss this idea further. If you cannot reply through this website, you can find my e-mail address from the Directory tab at www.wvu.edu. I hope to hear from you.
Donald D. Gray
Posted by Donald D. Gray on April 16,2009 | 01:46 PM
The Centrifuge Building in Johnsville is currently being transformed into the Johnsville Centrifuge and Science Museum. Retired leaders as well as astronaut Scott Carpenter spoke at an open house there on Thursday, April 23, and will speak again at another open house on Friday, April 24. The museum and the involvement in it is a spectacular tribute to Reuben Flanagan Gray and all those who served at Johnsville. The museum has a group on facebook which can be found by searching "centrifuge."
Posted by Chuck Hall on April 24,2009 | 07:08 AM
I worked on DFS for several years as a computer scientist. We built an F/A-18 cockpit for the centrifuge with the intention of both supporting G-Tolerance Improvement Program (G-TIP) and for use as a flight training tool. To that end we built a very sophisticated simulation for its time.
Currently, the centrifuge facility remains at the "North American Technology Center" which is what the NAWCAD Warminster facility became after the base reallocation in the late 1990's. It is being turned into a museum as the centrifuge no longer operates. The Iron Maiden is currently located at the Patuxent River NAS Air Museum in southern Maryland but I would anticipate it being returned to Warminster.
As a side note the runway at NAWC Warminster was long enough to be an alternate shuttle landing site, with concrete over 10' deep, but was dug up and removed for low income housing after the base closed.
John Lamb
Computer Scientist
Posted by John Lamb on October 8,2009 | 11:34 AM
Is there a list of all the participants in this program?
I have a Vet (David Shanks) who was a participant and is interested in contact. Any long term health conerns? (Hearing problems? Strokes?) Mr Shanks stories of his experience were interesting to hear.
Posted by George Bleicher on December 15,2009 | 06:40 PM
I've been trying to find some information on the Iron Maiden and have found very little. From the bits I have found and the few pictures it appears that there were two versions of the iron maiden and a coffin like apparatus nicknemed the sarcophagus. Can anyone tell me if this is correct or point me to more information?
Doug
Posted by Doug Smith on July 11,2010 | 12:44 AM
Nothing as dramatic as done by those researchers but I got to ride a slightly smaller, and more modern, version in Pensacola, FL up to 6G.
Posted by Mark on May 18,2011 | 07:17 PM
Question: why isn't the Johnsville Centrifuge a part of the Smithsonian museums?
Posted by Ellen melchiondo on December 18,2011 | 09:23 PM