Penultimate Space Shuttle Launch Delayed Again Until End of Week

The launch of the NASA space shuttle Endeavour was scrubbed three hours before lift-off, due to problems with one of the shuttle’s three auxiliary power units. The auxiliary power units provide hydraulic power, used by the shuttle for steering purposes during ascent and re-entry.

The astronauts, led by Commander Mark Kelly, were already in the Astrovan when the launch was scrubbed.

A heater in the first auxiliary power unit (APU-1) has stopped working. The heater is one of two on APU-1, and is used to prevent the APU’s hydrazine fuel from freezing once the shuttle reaches orbit. NASA technicians have been systematically checking the thermostat associated with the APU-1 fuel line.

Though the thermostat is still not operational, NASA technicians have yet to determine whether the issue lies simply with the thermostat, or with an electrical switchbox or shorted wire. According to NASA, no decision on the feasibility of a Monday launch will be made until Sunday morning, at the earliest. The target launch time for the Endeavour shuttle is currently set for Monday at 14:34 eastern time.

Speaking on the decision to scrub the launch, Mission Management Team Chair and Shuttle Launch Integration Manager, Mike Moses stated, “It was pretty straight-forward scrub today. The team made a very good call.”

Endeavour’s external fuel tanks were drained Saturday. The draining of the “rocket fuel” – 500,000 gallons of liquid oxygen and  liquid hydrogen, is necessary for NASA technicians to safely reach the aft of the shuttle, from which they will attempt to diagnose the issue.   

The failure of the Endeavour launch was described as “disappointing” by shuttle launch director Michael Leinbach.

“A disappointing day for Team Endeavour and the astronauts, but as we always say in this business, ‘we will not fly this machine until it’s ready’ and today it was not ready’, ” he said.

The Endeavour mission is scheduled to bring a $2.1 billion dollar payload to the International Space Station, including the Alpha Magnetic Spectrometer (AMS-02) and spare parts. The AMS-02 is a particle physics detector which will search for dark matter and antimatter.

Sponsored by the United States Department of Energy, it was built and is operated by an international consortium spanning 16 countries and 56 institutes, and will be the first magnetic spectrometer to operate in space.

The launch was of particular historical importance. The mission, STS-134, was to be Endeavour’s last, and the penultimate space shuttle mission before the space shuttle program is discontinued. Built in 1992, the Endeavour is the youngest orbiter, and has successfully completed 35 previous shuttle missions.  It has orbited the Earth 4,429 times, and has spent over 280 days in space.

The Endeavour will spend two weeks in orbit. Following its re-entry in May, plans have been made for the shuttle to be displayed in a California museum.

The mission has also received additional attention due to the presence of Arizona Congresswoman Gabrielle Giffords, the wife of Commander Kelly.  Congresswoman Giffords was shot during a public meeting with constituents in January, and is currently undergoing physical rehabilitation in Texas.  She was on site to watch Friday’s launch from a private area reserved for the astronauts’ families.

President Obama was also present to watch the shuttle’s scheduled launch on Friday. He met with the astronauts and Congresswoman Giffords.  Following the launch’s scrubbing, the President took a tour of the Kennedy Space Center with his family.

On Sunday, the launch was again scrubbed because engineers had to replace a switch box in the engine compartment. The new target launch date is later this week.

As the space shuttle program draws to a close, attendance at the launches has grown significantly. Police have estimated that as many as 750,000 people were expected to watch the Endeavour launch from the surrounding roads and beaches.

Space shuttle Atlantis, scheduled for launch June 28th, 2011, will be the last orbiter to fly before the 30-year shuttle programs ends. The shuttle will carry the Raffaello multipurpose logistics module and spare parts to the International Space Station.

Photo Credit: nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/multimedia/gallery/gallery-index.html

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