CLEVELAND, OH -- As NASA readies the space shuttle fleet to fly again, the agency's risk management teams are also paying attention to risk issues that affect the International Space Station.

"We have a lot of work in this arena to do," said Wayne Hale, NASA's space shuttle deputy manager at Johnson Space Center in Houston, adding that risk will always be part of any spaceflight. "We've brought the risk down a lot, but it's not [going to be] zero at the end of the day."

Since the loss of the space shuttle Columbia and its seven-astronaut crew during reentry Feb. 1, 2003, shuttle managers and engineers have worked not only to return its remaining three space planes to flight, but to prevent catastrophic accidents.

Hale said the failure rate for the space shuttle program has been two flights, and 14 lives, out of 113. "My job is to make sure it isn't three," he added.

Hale and other NASA officials spoke during the agency's Risk Management Conference 2004 here at the space agency's Assurance Technology Center in the Ohio Aerospace Institute.

Space shuttle engineers are implementing a series of recommendations made by the Columbia Accident Investigation Board (CAIB) to reduce mission risk, increase spacecraft safety and reliability. The next shuttle launch, Discovery's STS-114, is currently expected to launch sometime in May 2005.

The prime risk concern, Hale said, is still the launch system's external tank and efforts to eliminate the shedding of large pieces of insulating foam like that which critically damaged Columbia.

But there are also issues, such as developing the pedestals to hold a sensor-tipped orbital boom that will allow astronauts to take a close look at the spacecraft's thermal protection surfaces in orbit. While identical to the pedestals used for the shuttle's robotic arm, 20-year-old technical drawings for the tools are hard to read and have led to mis-machined parts.

"Prior to [Columbia] we thought we had a robust risk management program, but we were obviously wrong," said John Turner, NASA's space shuttle program risk manager at Johnson Space Center in Houston.

In addition to addressing risk with the space shuttle fleet, NASA must also work to lower risk associated with the International Space Station.

"A major part of the space station is maintenance," said NASA's Warren Pattison, deputy safety and mission assurance manager. "That is the nature of our business."

The grounding of the shuttle fleet after the Columbia accident halted space station assembly and limited extended expeditions to two crewmembers instead of the typical three. Despite reduced crew size, which the space station partners view as preferable to an unmanned space station, the station's operational requirements have not changed.

"We are trying to maintain the station with what we have," Pattison said.

During the last four two-person space station crews, the astronauts and cosmonauts have worked outside an empty space station for the first time, made complicated repairs on spacesuits and life support equipment and performed an unprecedented spacewalk coordinating between U.S. and Russian flight controllers.

But the station's future still lies with the space shuttle, which is the only vehicle currently capable of delivering the remaining modules and trusses to orbit for assembly.

"If we're going to complete the space station, we're going to need the shuttle," Pattison said. "It's going to take a lot of resources."