Sounds like AIRS https://en.m.wikipedia.org/wiki/Advanced_Inertial_Reference_Sphere https://en.m.wikipedia.org/wiki/Advanced_Inertial_Reference_... Basically f

Sounds like AIRS https://en.m.wikipedia.org/wiki/Advanced_Inertial_Reference_Sphere https://en.m.wikipedia.org/wiki/Advanced_Inertial_Reference_... Basically floating gyros, pretty common design for IMUs.