KENNEDY SPACE CENTER, FLORIDA -- It's almost time for the last go-round for the space shuttle Endeavour.

The final launch of the space shuttle Endeavour was supposed to take place at 2:47 Friday afternoon Central time.  NASA called off the Friday launch because of a heater failure.

Commander Mark Kelly and his crew were on their way to the launch pad, when NASA halted the countdown.  The Associated Press reports that the astronauts' van did a U-turn, and returned the astronauts to crew quarters.

NASA spokesperson, George Dillard, told the Associated Press that the next try will be Sunday at the earliest.

The NASA crew of 6 will lift off from the Kennedy Space Center in Florida and will be in space for 14 days.

This not only is the second to last launch for the shuttle program, it is also commanded by the husband of Arizona Rep. Gabrielle Giffords.  Giffords was shot attending a public meeting in Tucson back in January. She was in attendance for the Friday lift-off that was postponed, as well as President Obama and his family.

The shuttle’s load includes a $2 billion alpha magnetic spectrometer to be delivered to the International Space Station.  The instrument could prove or disprove the Big Bang Theory of how the universe was formed.

Following its mission, Endeavour will head to the California Science Center near Los Angeles after it is decommissioned.

The shuttle Atlantis is expected to make its final trip to space in June.


(The Associated Press contributed to this story.)

ABCNews.com contributed to this story.

Click here for a video gallary of Endeavour's final voyage