NASA's Mars Science Laboratory (MSL) rover mission has run into problems with the development of its thermal protection system (TPS), along with other issues that could jeopardize its targeted September 2009 launch date.

NASA Administrator Michael Griffin told House lawmakers in Washington Feb. 13 that while he still hopes the team can launch in 2009, the agency also is looking at options in 2010 or 2011.

The relative orbital positions of the Earth and Mars allow for a shorter trip time in 2011, although the spacecraft will hit Mars' atmosphere at a higher velocity, which has implications for the TPS, according to James Green, director of the planetary science division at NASA headquarters. For now, however, the team is still focused on a 2009 launch, Green stressed.

"We would look into those [later] options only as a contingency," he told Aerospace Daily.

NASA had planned to use a super lightweight ablative (SLA) heat shield for MSL, similar to what is used on the space shuttle's external tank. But SLA samples failed testing, so the team is switching over to Phenolic Impregnated Carbon Ablator (PICA) material.

Changing to PICA, which also is the leading choice to protect the Orion Crew Exploration Vehicle from reentry heating, is adding several tens of millions of dollars to MSL's cost, Griffin said. NASA is requesting $223.3 million for MSL in fiscal 2009, the lion's share of the Mars exploration budget for the year (DAILY, Feb. 11).

The heat shield issues, while adding cost, probably won't contribute to a mission delay because thermal protection system development is occurring in parallel with spacecraft and rover development, Green said.

But in addition to the heat shield problems, "things have gone more slowly than we would like" with the mission's overall development, Griffin said during his appearance before the House Science and Technology Committee.

MSL, a rover about the size of a small car, will be by far the largest mission mass ever landed on the Red Planet. "This is an incredibly complicated and intricate spacecraft," Green said. At the moment the team is lagging behind in the development of its avionics, he said.

Describing MSL as "crucial" to NASA's Mars program, Griffin said he doesn't consider the problems the team has encountered to be particularly unusual for a mission of MSL's scope. "I have great confidence in the Mars Science Lab team," he said.