CAPE CANAVERAL-- NASA plans to have a rescue shuttle ready for just the first two post-Columbia missions. After that, they might go back to business as usual.

If the first two flights make NASA confident the safety fixes to the shuttles are working, agency managers said they might determine it's no longer necessary to have a rescue vehicle on standby for future missions.

"After that, we will take a look and evaluate . . . and see where we need to go from there," said John Casper, a former astronaut now leading NASA's effort to implement recommendations made by the Columbia Accident Investigation Board.

When Discovery blasts off on the first return-to-flight mission, as early as the spring, NASA says Kennedy Space Center will be ready to launch Atlantis on a rescue mission within 45 days. On the second flight, a rescue shuttle will be ready to go within 58 days.

That's the amount of time that engineers estimate there would be food, water and working life support systems aboard the International Space Station to keep a larger crew of 10 people alive if the shuttle somehow becomes stranded there on one of the first two flights.

Safety changes, such as reducing the amount of external tank foam debris battering the orbiters' heat shields, will be tested on those flights.

"We need to understand the fixes that we've done we need to understand how well the systems work," shuttle program manager Bill Parsons said.

Having a rescue shuttle on standby never was a requirement before Columbia because the agency was confident it was flying a reliable vehicle, Parsons said. If the safety modifications work as planned, engineers and managers may regain confidence that a rescue shuttle is not necessary.

That's not the only post-Columbia change that might only last two launches. A requirement to launch during the daytime so that tracking cameras can get clear images of possible debris strikes also may go away after the first two launches, NASA has said.

Getting rid of those two requirements would be a big boost to meeting President Bush's directive to finish building the space station and retire the aging shuttles by 2010. Doing so will require flying four to six times per year, a rate that was difficult to meet prior to Columbia.

They dismissed suggestions by people inside and outside the agency that a rescue can't be pulled off, however. "We know it's do-able," Parsons said.

Published under license from FLORIDA TODAY. Copyright © 2004 FLORIDA TODAY. No portion of this material may be reproduced in any way without the written consent of FLORIDA TODAY.