Supporting the “The Right Stuff”: Looking Back at the Navy Medical Department and the Mercury Space Program

Part I: The Johnsville Human Centrifuge

By André B. Sobocinski, historian, U.S. Navy Bureau of Medicine and Surgery

“Here is a multimillion-dollar unique device developed by the Navy, but of such capability that it has received worldwide attention. It has been employed and will be employed as a tool for solving problems of interest to not only the Navy but to the USAF, NASA, industry, and science.”

~Capt. Clifford P. Phoebus, MC, USN, December 1959


Part I--The Mercury Seven in April 1959
The Mercury Seven posing for portrait in their pressure suits, 1959. Courtesy of NASA Johnson Space Center Collection

In 1959, the National Aeronautical Space Administration (NASA) embarked on an ambitious program to prepare seven military pilots for the first man-in-space program (Project Mercury).  Over the next several years, NASA would send its “Mercury Seven” through a gauntlet of classes, training and tests across the United States to ensure they had the “right stuff” for orbital flight.

From the very beginning of the space program, the Navy Medical Department would serve as an important collaborator with NASA. Our physicians and scientists would act as NASA advisors and medical monitors; and Navy medical research institutions in Bethesda, Maryland, New London, Connecticut, Pensacola, Florida and Warminster, Pennsylvania would help ensure the success of Project Mercury.

Part I--Johnsville_Centrifuge
The Johnsville Centrifuge, ca. 1959. Courtesy of NASA Johnson Space Center Collection

The Aviation Medical Acceleration Laboratory (AMAL) was one of the institutions vital to man’s journey into space. Established in 1949 at the Naval Air Development Station in Warminster, Pennsylvania, AMAL was the home of the largest centrifuge in the world. Constructed by the McKiernan-Terry Corporation under the cognizance of the Special Devices Center of the Office of Naval Research, the centrifuge was housed in a 125-foot diameter room and consisted of a gondola on the end of a 50-foot arm mounted on one of the largest DC motors in existence—a 180-ton, 4,000 horsepower General Electric motor with peak burst of 16,000 horsepower.  The device could accelerate from 0-173 miles per hour in just 7 seconds generating 40 G’s of radial acceleration. It was built on land that was 98 percent bedrock and what was considered “the most stable piece of land in North America.”

In essence, the centrifuge was a flight simulator built to test resilience to G(ravity)-forces and also techniques for reducing G-LOC (gravity-induced loss of consciousness).  From 1959 to 1963, the centrifuge was used almost exclusively by NASA to evaluate anti-blackout procedures, to simulate conditions of the Mercury capsule above 27,000 feet, the acceleration profiles of boost phases and re-entry phases, and also used to study the astronaut full-pressure suit.

Part I--Grissom at AMAL
Astronaut Virgil (Gus) Grissom seen preparing for training in centrifuge at AMAL. A Navy Corpsman attaches sensors to Grissom to monitor his body’s reaction to the centrifuge. Courtesy of NASA Johnson Space Center Collection

Each of the Mercury Seven would spend about 10 hours in the centrifuge. John Glenn called the centrifuge “sadistic” and “dreaded.” Alan Shepard would call it the most important preparation for his historic May 5, 1961 flight into space. Even Ham, the first chimp in space, underwent acceleration training at AMAL.

AMAL’s centrifuge continued to be used to train astronauts into the 1980s.  Its last run took place in 2005.

Today, the old centrifuge is still in existence and now part of the Johnsville Centrifuge and Science Museum in Warminster, Pennsylvania.

This is part one of a four part series. Stay tuned for part two featuring the Naval School of Aviation Medicine and the Human Disorientation Device.