Kennedy Space Center, Fla. ? The only way to really test the safety of the space shuttle’s redesigned external fuel tank is to fly, according to Discovery’s astronauts who said Friday they were eager for a May liftoff.

Six of the seven-member crew arrived at Kennedy Space Center to check equipment aboard the shuttle, visit the Orbiter Processing Facility and meet with reporters.

“We’re confident in the work being done, but every flight I’ve been on, something unexpected happens,” said mission commander Steve Lindsey, who is making his fourth space flight. “You get used to it. It’s a complex and dangerous business.”

NASA began redesigning a portion of the external tank after a chunk of foam fell off the tank during Discovery’s launch last July.

The foam missed the shuttle, but it was the same problem that damaged Columbia in 2003, causing it to break apart on its landing approach, killing the astronauts.

Wind-tunnel tests and other analysis still must be done before Discovery’s launch, which is scheduled for no earlier than May and could be delayed until at least July.

During the second mission in the Return to Flight sequence, the Discovery crew will continue to test new equipment, deliver supplies and cargo to the International Space Station and leave one member behind.

“We’re heading toward the right solution,” Lindsey said of the redesign efforts. “The program never advertised we would never lose foam.

“We want to make sure it’s small enough so that it doesn’t hurt the vehicle,” he said. “But we won’t know for sure until we fly it.”