NASA has scrubbed Friday's planned final launch of space shuttle Endeavour.
About three and a half hours before the shuttle's scheduled liftoff from Kennedy Space Center in Florida, Shuttle Launch Director Mike Leinbach announced its postponement, citing problems with two heaters associated with the shuttle's Auxiliary Power Unit. The unit provides hydraulic power during the shuttle's ascent and entry.
NASA announced that it will take at least 48 hours for engineers to assess the issue and reschedule the launch.
The postponement came well after Endeavour and its astronauts were being prepped for it's scheduled 3:47 p.m. EDT liftoff.
The shuttle had been loaded with 500,000 gallons of fuel. And the six Endeavour astronauts had already suited up and were being transported to the launch pad when the announcement was made.
Endeavour is poised for a 15-day mission to bring equipment and supplies to the International Space Station, and to conduct experiments there. The equipment includes two S-band communication antennas, spare parts for the station's humanoid robot, and a spare arm for the station's Dextre robot.
The shuttle also is carrying a piece of equipment that will search space for some of the biggest mysteries of physics -- antimatter and dark matter. The AMS (Alpha Magnetic Spectrometer) particle detector will be installed and operated on the International Space Station.
And while getting that machine in place is of great importance to scientists, the shuttle's mission is a historic one for NASA.
This mission is the second to last for the space shuttle program before NASA retires the fleet. Space shuttle Atlantis is scheduled to make the program's final launch on June 28.
Endeavour, the youngest shuttle in NASA's fleet, was first launched on May 7, 1992.
It's also had a storied history, taking astronauts aloft to conduct the first servicing mission on the Hubble Space Telescope. It also has made a trip to the MIR space station. The final trip marks its 12th to the International Space Station.
And according to NASA, at the time of Endeavour's final landing, the shuttle craft will have travelled more than 100 million miles during 25 flights and spent more than 294 days in space.
Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin, or subscribe to Sharon's RSS feed . Her e-mail address is firstname.lastname@example.org.