ISS Status Update: One of Four CMGs Fails

At 10:00 a.m. Central time today, International Space Station flight controllers reported that one of four Control Moment Gyroscopes (CMG) on the station’s Z1 Truss, which provide the majority of attitude control for the complex, experienced an underspeed, or loss of revolution per minute capability, apparently because of the failure of an internal spin bearing.

Astronauts inside the station’s Unity module radioed that they felt a growling vibration, apparently associated with the spindown of the CMG.

The loss of the CMG will have no impact on the STS-111 or ISS operations for the newly arrived Expedition Five crew since there are three other healthy CMGs and only two are required to maintain full attitude control for the 154-ton complex. Meanwhile, the astronauts and cosmonauts pressed ahead with work to enter the Leonardo Multi-Purpose Logistics Module for the start of the transfer of almost three tons of logistics and supplies for Expedition Five Commander Valery Korzun and Flight Engineers Peggy Whitson and Sergei Treschev.