Valley Forge Composite Technologies (USA; OTCBB: VLYF) announced its Aerospace Division has won a contract to supply momentum wheels for the attitude control systems going into upcoming microsatellites from an undisclosed customer.

NASA reaction/momentum wheel: cover removed

Valley Forge produces momentum wheels as extremely high precision full complement ball bearings, spinning at around 100,000 RPM in a vacuum and driven by brushless DC motors. Allowable radial runout of a momentum wheel bearing is less than 0.000001"; the company estimates their MTBF service life as approximately 226 years.

Valley Forge offers the bearings and wheels in sizes from 0.2" through 15.5" diameter, with stabilization force up to 400,000 ft-lbs available for very large satellites.

Valley Forge standard momentum wheel specs
Momentum wheels are the most critical components for satellite stabilization, momentum, and directional control. They are also necessary because satellites are subject to directional instability caused by radiation pressure.

Spinning at high speeds, they operate essentially like extremely sophisticated electronically-controlled gyroscopes. Satellites normally have four wheels -- one for each axis x, y, z, and a fourth for redundancy should one of the primary wheels fail.

NASA defines momentum wheels this way:

Reaction/momentum wheels are flywheels used to provide attitude control authority and stability on spacecraft. By adding or removing energy from the flywheel, torque is applied to a single axis of the spacecraft, causing it to react by rotating. By maintaining flywheel rotation, called momentum, a single axis of the spacecraft is stabilized. Several reaction/momentum wheels can be used to provide full three-axis attitude control and stability.

NASA licensed its small reaction/momentum wheel technology in 1997 to CTA Space Systems [now Orbital Sciences Corporation].

Wolfram Research notes about Reaction Wheels are (here).

Small reaction / momentum wheels are so inherently critical to the success of all modern small satellite programs that in 1999, the NASA Government Invention of the Year Award went to Charles Clagett of NASA-Goddard for the small reaction / momentum wheel:

NASA 1999 Invention of the Year : reaction/momentum wheel
NASA-Goddard's U.S. Patent is 5,723,923 [USPTO].