LOS ANGELES (AP) -NASA’s flagship mission to land a nuclear-powered, next-generation rover on Mars is facing development problems and ballooning costs that could threaten its scheduled launch next year.

NASA Administrator Michael Griffin told a congressional hearing this month that engineers had to redesign the heat shield on the Mars Science Laboratory after tests showed the protective layer would not survive entry through the Martian atmosphere.

The extra work is expected to add $20 million to $30 million to the $1.8 billion price tag, already $165 million over budget.

NASA is still aiming for a 2009 launch, but the space agency is also mulling alternative voyages in 2010 and 2011, Griffin told the House Science and Technology Committee on Feb. 13.

“Things have gone along more slowly than we would like,” Griffin said.

Any delay of the Mars Science Lab would deal a major setback to NASA, which already had to push back a mission to send an atmospheric probe to the Red Planet because of an undisclosed conflict of interest in the purchasing process.

The Mars Science Lab will be the most advanced and expensive unmanned probe ever sent to the Martian surface. The 9-foot-long mobile robot is larger and can travel farther than the twin rovers Spirit and Opportunity, that are still alive four years after parachuting to opposite ends of Mars.

Both rovers have uncovered geologic evidence of ancient water on the planet. The goal of the Mars Science Lab is to determine whether the environment could once have been favorable for microbial life using sophisticated instruments to measure for the presence of life’s chemical building blocks and beam the discoveries back to Earth.

Science gleaned by the Mars Science Lab is also expected to help prepare NASA for its long-term plans to fly humans to Mars after a return to the moon.

Engineers initially wanted to use a heat shield like the type on the space shuttle’s external fuel tank, but extensive testing last spring proved it would break. NASA switched to a stronger cover similar to the one that cocooned the Stardust probe, which returned to Earth in 2006 with comet dust.

Because Stardust re-entered Earth’s atmosphere at twice the speed expected for Mars Science Lab, engineers feel confident the new shield will hold, said NASA spokesman Dwayne Brown.

Griffin said development hurdles are to be expected in such a complex project and he didn’t consider the problems to be out of the ordinary.

Some members of the Mars science community expressed concerns about the mission’s progress. Brown University geologist John Mustard said that if the launch date slips, the costs will soar.

“It kind of interrupts what has been an incredibly successful sequence of missions,” said Mustard, who heads an advisory group that gives scientific input on future Mars projects.

It’s not the first time the Mars Science Lab has run into problems. The project is managed by NASA’s Jet Propulsion Laboratory in Pasadena.

To control costs, NASA last year cut a camera from the mission and halted work on a laser chemistry tool. As a result, San Diego-based contractor Malin Space Science Systems agreed to develop the camera at its own expense and the project received outside funds to continue work on the laser instrument.

Some space policy analysts contend that if the Mars Science Lab’s budget spirals out of control, it could raise questions about the cost-effectiveness of robotic exploration.

“The repercussions are more pronounced for the future of the space program,” said Howard McCurdy, an American University public policy professor. “Are robots really that much more superior to human beings for going to the planets? Or are robots harder than we thought to manage?”

U.S. Rep. Mark Udall, D-Colo., said in a statement he would not question NASA’s decision to delay the launch if needed. However, Udall, who is on the House committee, added: “I want to be confident that NASA is doing all that it can to carry out the … development efficiently and effectively.”

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