Monday, May 02, 2011

Crews work to ready Endeavour for next attempt

Kennedy Space Center teams today plan to remove from shuttle Endeavour a faulty electronic switch box that scrubbed last Friday's launch attempt.

A new launch date could be set today or tomorrow. For now, NASA is only saying the launch will be no sooner than 12:09 p.m. Sunday, Mother's Day.

Over the weekend, a rotating service tower at launch pad 39A was closed around Endeavour, and cryogenic propellants were drained from the orbiter's fuel cell system.

The roughly 45-pound box called the Load Control Assembly is located in an avionics bay inside an access door to the orbiter's left aft compartment.

The box routes power to dozens of functions associated with nine different systems. On Friday, it failed to turn on heaters that cover a fuel line feeding a unit that generates hydraulic power.

A replacement box was expected to be installed Tuesday, and then retests of all the systems with power switched to them, including some deep in the aft compartment would take a full two days.

As a result, Endeavour won't launch until after Friday's planned launch of a United Launch Alliance Atlas V rocket with a missile warning satellite from Cape Canaveral Air Force Station.

Then NASA will determine which launch date works best so that Endeavour wouldn't be scheduled to depart the International Space Station on the same day as a Soyuz spacecraft. That was expected to be a conflict for a May 9 launch, but plans are being assessed.

IMAGE: On Sunday, a technician at launch pad 39A crouched in shuttle Endeavour's aft section, where teams were preparing to remove and replace the aft load control assembly-2 (ALCA-2). Located in the orbiter's aft avionics bay 5, the assembly is believed to have caused heaters on a fuel line for Endeavour's auxiliary power unit-1 (APU-1) to fail April 29 during the first launch attempt for the STS-134 mission. Credit: NASA/Kim Shiflett

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