Shuttle Launch Scrubbed Over Fuel Sensor Problems

Dec. 6, 2007 — -- The launch of a much-anticipated mission to install a European lab on the International Space Station was delayed today, after NASA had trouble with two fuel sensors on the shuttle's external tank.

According to NASA engineers, earlier this morning, the shuttle's external tank was being loaded when two of the hydrogen tank's four engine cutoff sensors dropped offline. The shuttle is not allowed to fly with only two sensors working. Engineers are currently trying to determine whether this is a computer glitch or a hardware problem.

NASA may still try to launch Atlantis, Friday.

The astronauts' flight will include the installation of a new lab at the International Space Station.

Mission STS 122 on the Space Shuttle Atlantis is a critical step in the assembly sequence for the space station. The crew of seven will deliver and install the European-built Columbus module.

Few observers thought NASA could pull off four shuttle flights in 2007, the most missions flown in one year since the Columbia accident in 2003.

In February, a hailstorm at the Kennedy Space Center knocked thousands of holes in the external tank on the Atlantis, delayed its March launch until June and played havoc with NASA's ambitious plans to get the shuttle program back on track. The space agency had wanted to launch five missions this year but is happy to settle for four.

It has been a very good year for NASA, as it performed four shuttle missions that proved the agency could face challenges on orbit and solve the problems with the efficiency and finesse the agency had been famous for during earlier days.

In the coming mission, three spacewalks are scheduled for the lab's installation. If time permits, and the crew can conserve enough shuttle power, a fourth spacewalk will be added to inspect a damaged mechanism that rotates the solar array of the right side of the space station.

Engineers want to know what is causing something inside the mechanism to grind. So the joint has been turned off until it can be fixed.

Cmdr. Steve Frick is in charge of this shuttle flight, his second to take him back to the space station.

Frick told ABC News he is anxious to see how much the station has changed since his last visit.

"It is tremendous to see the space station and how it has developed since I was there five years ago. It is going to look totally different. You have this huge truss out there now with these huge solar arrays. It has much more pressurized volume where we can actually live inside the space station," Frick said. "We feel really lucky to bring up another one and not just another pressurized volume that will increase the area where we can live and work, but the Columbus module, bringing the Europeans into the space station in a huge way."