Nearly one year after the Space Shuttle Columbia accident left seven astronauts dead and the U.S. space program stuck in limbo, NASA is preparing to resume shuttle flights this fall with the knowledge that the fleet’s days are numbered.

In the months leading up to NASA’s second space shuttle disaster in 17 years, the agency’s top managers were warming to the idea of keeping the shuttle flying well into the next decade -- possibly until 2020 or beyond. NASA had scheduled a space shuttle summit for just a few weeks after Columbia was slated to return from her 28th mission to get working on a plan for what it would take to keep the fleet flying for many years to come.

NASA and the nation’s confidence in the aging fleet changed abruptly when Columbia broke up Feb. 1, 2003 over the western United States. The Columbia Accident Investigation Board, convened within 48 hours of the accident, had by August recommended that NASA commit to a thorough re-certification of the space shuttle fleet before flying it past 2010.

Such an undertaking would not have been cheap. According to government  and industry sources, the White House had estimated that certifying the shuttle fleet to fly beyond 2010 would cost at least $3 billion and that keeping it flying would cost about $5 billion a year, up from the $4 billion NASA spends today.

When U.S. President George W. Bush unveiled a new space exploration vision for NASA Jan. 14, he pledged the United States to complete assembly of the international space station by 2010 and then retire the shuttle fleet.

“The president has given us a different future,” Michael Kostelnik, NASA’s deputy associate administrator for the space shuttle and space station programs, said in a Jan. 23 interview.

NASA Administrator Sean O’Keefe told reporters at a breakfast here Jan. 21 that the agency will meet or exceed all the recommendations laid down by the Columbia Accident Investigation Board before shuttle flights resume. He also predicted that once the shuttle is safely flying again, NASA expects to fly as many as five shuttle missions a year until the end of the decade.

For now, NASA may have more questions than answers about how this new future plays out. But some matters are becoming clearer by the day.

Kostelnik said NASA now has what amounts to a presidential mandate to return the space shuttle to flight status as soon as possible and get on with assembly of the space station. To meet these goals on the timetable set by the president, Kostelnik said, NASA will need to get all three of its space shuttle orbiters flying again. It will need to continue to invest in the space shuttle to ensure that it can fly safely until its job is done. And it will have to achieve a shuttle flight rate comparable to the schedule NASA sometimes struggled to maintain even before losing Columbia.

NASA hopes to fly as many as two shuttle missions before the end of 2004. The earliest would be Sept. 12. If NASA can get that flight off the ground within a month of that target, Kostelnik said, it would try for a second shuttle mission in November.

But if NASA misses the launch window that opens Sept. 12 and closes Oct.

10, Kostelnik said the odds of returning to flight in 2004 drop considerably. Because of new restrictions NASA has placed on shuttle launches at the recommendation of the Columbia Accident Investigation Board -- such as launching only during daylight hours -- November offers very few good launch opportunities.

NASA also wants as big a window as possible for the first flight, so if the program is not ready to go by mid-October, Kostelnik said, NASA would most likely wait until spring for its return to flight.

At Kennedy Space Center near Cocoa Beach, Fla., NASA has two shuttle orbiters -- Atlantis and Discovery -- being prepared for flight. Kostelnik said the agency would decide by March which orbiter has the best chance to be cleared for launch this fall.

Whichever orbiter is not picked to fly first, Kostelnik said, would be kept on track to launch soon after -- and not just because NASA would like to get two flights in before the end of 2004.

Kostelnik said NASA also wants to have the second orbiter in position to launch within weeks of the first in case the first crew finds itself stranded on orbit with a crippled shuttle that cannot be repaired.

NASA expects to fly the shuttle just two or three times in its first full year of operations and then ramp up to four or five flights a year thereafter, Kostelnik said.

NASA’s shuttle manifest is still in flux. But the agency expects to fly a minimum of eight missions to build the space station out to a point known as U.S. core complete. Fulfilling the United States’ commitment to launch the modules and other components being built by its partners would take an additional 15 shuttle missions.

Kostelnik said NASA is also evaluating whether it needs to add logistics flights to deliver spare space station hardware, such as the bulky control momentum gyroscopes, that are too big or too heavy to fit aboard any vehicle other than the shuttle.

“We are trying to see what options there are to add in logistics flights in order to put large spares on orbit before we put the space shuttle fleet down,” he said.

Meanwhile, NASA still has a lot of work to do before it can launch its first shuttle mission since the Columbia disaster.

An outside panel appointed last year to oversee NASA’s flight preparations reported Jan. 20 that the shuttle program has a long way to go to comply with all the conditions the Columbia Accident Investigation Board imposed on returning to flight.

Writing in its interim report, the Stafford Covey Task Group said that although NASA is addressing all 29 finding and recommendations of the CAIB’s final report, progress on many of the recommendations has been “uneven.”

“As time passes and the interval before the next scheduled flight diminishes, the enormity of the remaining task looms,” the report states.

Kostelnik did not dispute the group’s findings. “Our planning is not complete yet,” he said. “But I think we are peaking, hitting the crest of things and the sense I’m getting is we will start moving very aggressively in the next month to month and a half. We have come a long way.”

Kostelnik said NASA has not finalized its approach to meeting a number of the key recommendations of the CAIB report, including how to perform non-destructive testing of the space shuttle’s external fuel tank and repairing damaged shuttle wings on orbit. NASA is still modeling the danger posed by the insulating foam the shuttle’s external tank tends to shed during liftoff, Kostelnik said. Additionally, study of the aerodynamics of a redesigned fuel tank is still in process, with a mockup of the modified tank not expected to be ready for wind tunnel testing until summer.

Kostelnik predicted a high level of activity across the program in the months ahead as NASA settles on the most promising approaches and moves out quickly to make them happen.

NASA is also going beyond the CAIB recommendations in some areas. For example, the CAIB requested NASA to come up with a plan prior to its first flight for establishing a so-called independent technical authority to guard the space station against what had become the all too frequent practice of issuing waivers that compromised safety. Kostelnik said NASA not only intends to have a plan finished by the time it returns to flight, but to have the new organization up and running.