The term Drive Lock Assembly or DLA is used to refer to the mechanisms present in each Solar Alpha Rotary Joint or SARJ which allow the outer segments of the Integrated Truss Structure

Integrated Truss Structure

the Integrated Truss Structure forms the backbone of the International Space Station, with mountings for unpressurized logistics carriers, radiators, solar arrays, and other equipment.-History:...

, a component of the International Space Station

International Space Station

The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

 or ISS, to rotate and track the Sun

Sun

The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. A component of the DLA is a pinion

Pinion

A pinion is a round gear used in several applications:*usually the smallest gear in a gear drive train, although in the case of John Blenkinsop's Salamanca, the pinion was rather large...

 which engages with the race ring that serves as a bull gear. There are two race rings and two DLAs in each SARJ providing on-orbit redundancy, however a series of space walks would be required to reposition the DLAs and the Trundle Bearing Assemblies (TBAs) to utilize the alternate race ring.

Damage to Starboard SARJ

Currently NASA is investigating damage to the Starboard SARJ of the ISS. It is not known whether the DLA is damaged, however a spare DLA was brought to the ISS on STS-122

STS-122

STS-122 was a NASA Space Shuttle mission to the International Space Station , flown by the Space Shuttle Atlantis. STS-122 marked the 24th shuttle mission to the ISS, and the 121st space shuttle flight since STS-1....

.