At NASA Kennedy Space Center’s Orbiter Processing Facility-3, technicians will replace a power drive unit (PDU) that stalled during latching of shuttle Discovery’s payload bay doors yesterday. A spare PDU is available and the process will take approximately three days. Teams also will work on the spacecraft’s thermal protection system (TPS) over the weekend. At NASA’s Johnson Space Center, the STS-133 crew will practice TPS repair techniques in the Virtual Reality Lab today.