HOUSTON (Reuters) - NASA approved a major design change in the space shuttle's fuel tank on Wednesday, clearing the last major hurdle before shuttle flights can resume as early as July 1, officials said.
"There were no surprises. Everything went smoothly," NASA spokeswoman June Malone said after managers and engineers approved the new tank design at a meeting at NASA's fuel tank manufacturing plant near New Orleans.
Officials will choose a firm launch date for Discovery at the completion of a formal flight review next week.
The shuttle fleet was grounded after the fatal 2003 Columbia accident for safety upgrades. After changes were made, Discovery was sent aloft in July 2005 but that flight exposed additional problems with the fuel tank.
A chunk of foam insulation fell off Columbia's fuel tank during launch, hit the ship's wing and critically damaged its heat shield. Seven astronauts aboard the shuttle died when Columbia broke apart as it flew through the atmosphere for landing.
Large foam chunks also fell during Discovery's liftoff last year, but did not strike the orbiter. The biggest piece broke off from a hand-crafted foam structure that shielded cables and pressurization lines from the tumultuous winds during launch.
Engineers proposed removing two foam windshields, eliminating the potential for debris. After nearly a year of debate, testing and analysis, managers decided the shuttle was safe to fly with the redesigned tank.
"The tests proved that the cable trays and pressurization lines are aerodynamically capable of withstanding the launch," said Kyle Herring, a spokesman with the Johnson Space Center in Houston. "This is a big one because it certifies the tank to fly with this major change."
NASA needs to get the shuttles flying to finish building the International Space Station before the shuttle fleet is retired in 2010. The agency has spent nearly $1.3 billion getting the shuttles ready to fly again.