NASA Shuttle launch director Mike Leinbach stated that Endeavour’s launch will be no earlier than Monday at 2:33 p.m. EDT. Engineers need that time to troubleshoot an issue that resulted in today’s launch scrub.
During today’s countdown, engineers detected a failure in one of two heater circuits associated with Auxiliary Power Unit (APU) 1. Heaters are required to keep the APUs’ hydrazine from freezing on orbit. Attempts to activate the heater were not successful and engineers now believe the problem might be associated with a Load Control Assembly, which is a switchbox, located in the aft end of Endeavour, or an electrical short in the wires leading into or out of the switchbox.
Because of this, Leinbach said there will be a minimum 72-hour scrub turnaround.
The ISS Progress 42 cargo craft docked to the Pirs docking compartment on the International Space Station at 10:28 a.m. EDT Friday, less than six hours before space shuttle Endeavour’s scheduled launch to the station on the STS-134 mission.
The cargo ship launched at 9:05 a.m. Wednesday from the Baikonur Cosmodrome in Kazakhstan, carrying 1,940 pounds of propellant, 110 pounds of oxygen and air, 926 pounds of water and 2,976 pounds of maintenance hardware, experiment equipment and resupply items for the Expedition 28 crew.