NASA's countdown clocks are ticking once again for what will be the next-to-last space shuttle launch, now set for Monday, and the six-man crew is ready to go.

The countdown began Friday morning for the second time for the shuttle Endeavour's final mission.  A launch attempt late last month was canceled because of an electrical problem aboard Endeavour.

NASA says repairs have been made and the problem is fixed.

Commander Mark Kelly and his five crewmates returned to Kennedy Space Center Thursday.  Their families will follow this weekend, including Kelly's wife, Arizona Congresswoman Gabrielle Giffords, who is recovering from gunshot wounds she got at a public constituents' meeting in January.

Endeavour will fly to the International Space Station and deliver a $2 billion science experiment. Four spacewalks are planned during the 16-day mission.  The shuttle Atlantis will fly the shuttle program's last mission in July.

via NASA counting down again for next-to-last launch | Science and Technology news | Chron.com - Houston Chronicle.

When the fleet of shuttle orbiters is taken out of service later this year, America's astronauts will be forced to hitch rides on Russian spacecrafts to travel to and from the International Space Station.

And these rides won't come cheap.  NASA will pony up nearly $56 million per seat for six round trips to the ISS in 2013 and 2014, and the price balloons to $63 million per seat for 12 additional spots before the end of 2015.

NASA hopes to have its next generation spacecraft, the Orion, in service by 2015.