The PIGA is still considered the premier instrument for strategic grade missile guidance, though systems based on MEMS technology are attractive for lower performance requirements.
Up to three such instruments may be required for each dimension of an INS with the three accelerometers mounted orthogonally generally on a platform stabilized gyroscopically within a system of gimbals.
Since the number of shaft rotations represented speed, a cam switch was used to initiate missile control sequences such as engine throttle-down and shut-off.
A recovered MMIA accelerometer from an unexploded V2 was presented to Dr Charles Stark Draper of the Massachusetts Institute of Technology's instrumentation lab who had been developing the basis of inertial navigation for aircraft by initially concentrating efforts on achieving extremely low drift rate gyroscopes known as a floated integrating gyroscope.
The more generic name of PIGA was suggested by Dr. Draper due to the addition of various refinements such as electromagnetic or optical sensing of pendulum position.
Initially, compressed nitrogen was used but later fluorocarbons which had the advantage of being recyclable on board the missile or aircraft during extended waiting periods was used.