PARIS -- Europe has begun evaluating its options in the event the U.S. space shuttle is retired too early to launch the Columbus science laboratory, Europe's billion-dollar showcase contribution to the international space station, European Space Agency (ESA) Director-General Jean-Jacques Dordain said July 28.

ESA has ordered a team of engineers to evaluate scenarios in which the shuttle is capable of launching 20 times, 15 times and 10 times between now and its intended 2010 retirement date. The study, whose conclusions are expected in early September, includes a scenario in which the shuttle cannot launch the Columbus module.

"I will have an evaluation of all these scenarios, including a scenario in which there is no Columbus," Dordain said in an interview. "My biggest concern is to optimize the investments that our member governments have already made."

Columbus is the centerpiece of a multibillion-dollar European investment in the space station that includes an unmanned space tug, called the Automated Transfer Vehicle (ATV) that will deliver water, fuel and other supplies to the station. The ATV, whose first launch is scheduled for mid-2006, has been financed by ESA governments in part to repay NASA for the U.S. investment in the station's basic infrastructure and utility-type support including electricity and astronaut transport.

Dordain said that if Columbus is not launched, the ATV program's original reason for being would be lost and the program's interest to European governments would diminish.

ESA has spent some 300 million euros ($362 million) in charges directly related to the delay in the launch of the Columbus lab, which is completed and in storage at EADS Space Transportation's Bremen, Germany, plant. Those delay-related costs are certain to rise, as the estimates assumed a Columbus launch by the U.S. shuttle in 2006. A 2007 date is more likely -- assuming no further delays.

Like a similar laboratory built by Japan, Europe's Columbus facility was designed for launch only on the shuttle.

ESA member governments plan to meet in December in Berlin to fix the agency's mid-term financial and program objectives. Dordain said that by then he hopes the latest shuttle-related issues are resolved, and that the vehicle has been once again cleared for flight.

If not, he said, he will canvass his government members to determine how they wish to proceed. "Maybe we can use the station even without Columbus, and barter ATV against some kind of access to the station," Dordain said. "We are looking at all kinds of possibilities. We also need to think about whether, even if it is launched, we will be able to use it as we planned. There is no sense in launching Columbus without being able to use it fully. I know this: Our governments have invested billions of euros into this project, and right now my top priority for the program is to maximize a return on that investment."