Plethysmograph, Leg Volume, Skylab

Researchers at the United States Air Force Academy's Instrumentation Laboratory developed this blood volume measuring device for an experiment to be performed on board Skylab in the 1970s. This unit malfunctioned during testing, however, and was not used in space.

The devices were strapped around each leg of the astronaut during use of the Lower Body Negative Pressure unit, which put stress on the cardiovascular system of the astronaut beyond that otherwise experienced during spaceflight. The unit applied a suction pressure on the lower body to get their blood to move towards their legs as gravity does to the human body on Earth. These bands measured the change in blood volume and transmitted the data for later analysis. A pressure unit such as this, if successful, would help astronauts recover from some of the physical difficulties of long-duration spaceflight in low-gravity environments.

NASA transferred this measurement device to the Museum in 1974.