Additional Testing for Faulty Power Box

Technicians at the NASA Shuttle Logistic Depot in Cape Canaveral, Fla., continue additional testing today on a faulty power distribution box, called a Load Control Assembly 2 (LCA-2). It was removed Tuesday morning from the aft compartment of space shuttle Endeavour on Launch Pad 39A at NASA’s Kennedy Space Center.

Technicians are trying to determine what caused the power box to fail. Initial testing from yesterday shows a driver (circuit) inside the LCA-2 shorted out. The LCA-2 feeds power to heaters on the fuel line for Endeavour’s auxiliary power unit-1 (APU-1). Initially, when the shorted out driver was replaced, the LCA-2 appeared to worked as designed.

‪Technicians are performing additional failure analysis on the driver today to confirm whether the short experienced by the system came from inside or outside the LCA-2. Depending on the results, additional testing of the box may be required.

‪On Launch Pad 39A, a new LCA-2 box was installed into Endeavour Wednesday morning, and technicians are retesting the system before Endeavour’s next launch attempt is scheduled. Currently, Endeavour’s no earlier than launch date remains May 10.

‪The APU-1 fuel line heaters did not work on April 29, prompting the launch team to scrub the Endeavour’s first launch attempt for the STS-134 mission to the International Space Station.