The Johnsville Centrifuge was a facility at the Aviation Medical Acceleration Laboratory of the Navy Air Development Center, Johnsville, Pennsylvania, used throughout the early American space program; it was the most powerful centrifuge then in existence. With a 17-meter radius, it had a rate change of 10g per second and could reach 40g per second. The 3- by 1.8-meter-diameter gimbal-mounted gondola was fully air-conditioned.

Prior to the arrival of the Mercury astronauts in August 1959, the Johnsville Centrifuge was used for testing by X-15 pilots – including Neil Armstrong prior to his selection by NASA. To this day, the Johnsville Centrifuge holds the distinction of being the largest human centrifuge ever built. In addition to the Centrifuge, the developments at the Johnsville Naval Air Development Center (NADC) included pioneering work on GPS, transition lenses, ejection seats, and "black boxes".

Johnsville Centrifuge and Science Museum

Although the centrifuge itself (including its 4,000 horsepower electric motor) has been decommissioned for the past decade or so, it is in private hands and a science museum has opened in Warminster, Pennsylvania, with the historic centrifuge as its prime attraction. Also on display is a collection of artifacts including the gondola and contour couch used by Deke Slayton in the centrifuge, and the Mayo Tank – a precursor to the "Iron Maiden" that was used to test the effectiveness of water as a buffer to high G forces.