Standard Precision Navigator/Gimbaled Electrostatic gyro Aircraft Navigation Systems (SPN/GEANS) grew out of work in the 1950s by Professor Arnold Nordsieck of the University of Illinois on a novel gyroscope design, the Electrosatically Suspended Gyroscope (ESG). In the ESG, the rotating mass is a spherical ball supported in a vacuum by an electrostatic field. The corporation that took up Nordsieck’s work most actively was Honeywell of Minneapolis.

Professional Instruments Company lapped super-precise spherical rotors for Honeywell’s ESG. With these highly-favored gyros, the Navy’s nuclear-powered submarines could remain submerged for 30 days at a time, without requiring a star-based recalibration.

The photograph shows Professor Arnold Nordsieck holding an early experimental ESG. Note the spherical rotor in Nordsieck’s left hand.