Bearings are rocket science

Sept. 1, 2005
Custom hybrid ball bearings from Pacamor Kubar Bearings go in rocket-engine controls and withstand both cryogenic temperatures and the vacuum of space.

Pacamor Kubar hybrid bearings support a gear shaft in a RVDT (Rotary Variable Differential Transformer). The RVDT actuator adjusts the throttle setting of an upperstage rocket engine.


Custom hybrid ball bearings from Pacamor Kubar Bearings go in rocket-engine controls and withstand both cryogenic temperatures and the vacuum of space. The bearings support a shaft in rotary variable differential transformer gearheads from Kearfott Guidance & Navigation Corp. The RVDT supplies position feedback to an actuator that adjusts a throttle-control valve for an upper-stage rocket engine. The rocket booster, when completed, will be used to deploy satellites.

"The RVDT unit operates at 425°F, too cold for standard lubricants," says Kearfoot Engineering Manager Tony Patti. "In addition, the bearing must tolerate repeated oscillating motion."

PKB engineers spec'd bearings with a special PTFE-based retainer. This low-friction material has good chemical resistance, handles low and high temperatures, and provides limited lubrication. The use of dry-film lubricants and ceramic bearing balls further help the bearings survive the harsh environment.

MAKE CONTACT
Kearfott Guidance & Navigation Corp.,
Wayne, N.J., www.kearfott.com

Pacamor Kubar Bearings, Troy, N.Y., pacamor.com

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