Hemispherical resonator gyroscope

For a single-piece design (i.e., the hemispherical shell and stem form a monolithic part[1]) made from high-purity fused quartz, it is possible to reach a Q factor of over 30-50 million in vacuum, thus the corresponding random walks are extremely low.

[2] Such resonators have to be fine-tuned by ion-beam micro-erosion of the glass or by laser ablation in order to be perfectly dynamically balanced.

In application to the HRG shell, Coriolis forces cause a precession of vibration patterns around the axis of rotation.

The resonating shell weighs only a few grams and it is perfectly balanced, which makes it insensitive to vibrations, accelerations, and shocks.

The HRG exhibits superior SWAP (size, weight, and power) characteristics compared to other gyroscope technologies.

The HRG generates neither acoustic nor radiated noise because the resonating shell is perfectly balanced and operates under vacuum.

Currently three companies are manufacturing HRG: Northrop Grumman,[9] Safran Electronics & Defense[13] and Raytheon Anschütz.

[14] Classical HRG is relatively expensive due to the cost of the precision ground and polished hollow quartz hemispheres.