WASHINGTON — As U.S. President Barack Obama prepares to make a decision that could redirect NASA’s human spaceflight activities and investments, aerospace industry executives warn that without a sustained financial commitment to manned space exploration, the president risks alienating a new generation of scientists and engineers and ultimately harming national security.

During a hearing before the House Science and Technology Committee Dec. 10, lawmakers heard testimony from aerospace industry leaders who said the president must consider short- and long-term work force consequences as he weighs alternatives to NASA’s Constellation program, the 5-year-old effort to replace the space shuttle with new spacecraft optimized for lunar missions.

NASA’s work force includes 18,000 NASA civil servants and tens of thousands of contractors heavily concentrated at or near the agency’s 10 field centers and several ancillary facilities. With the space shuttle fleet expected to retire as early as next September, thousands of civil servants and contractors are expecting to transition to a Constellation program that is struggling to maintain a 2015 target date for fielding the Orion Crew Exploration Vehicle and its Ares 1 rocket.

Former Martin Marietta chief Tom Young said that as Obama considers alternatives to Ares 1 and Orion, including scenarios relying on commercial firms to transport astronauts to low Earth orbit, the president must recognize the value of the current spaceflight work force, which has evolved over decades of extraordinary success and tragic failure.

“Without a challenging and meaningful space program, this national capability will atrophy,” Young testified before the committee. “It can only be maintained by inspiring use. It has a limited shelf life.”

Young characterized the spaceflight work force as a national treasure and cautioned the Obama administration to avoid seeking “miracle” solutions to budget concerns associated with NASA’s manned spaceflight program.

“We’re faced with kind of a profound decision,” Young told lawmakers. “I strongly believe that if we do not approach this from a ‘what’s in the best interest of the country,’ as opposed to a budget issue, then I fear we’re going to end up with the wrong answer.”

Rep. Gabrielle Giffords (D-Ariz.), chairwoman of the House Science and Technology space and aeronautics subcommittee, said the president’s decision on NASA’s human spaceflight future will have a lasting impact on the nation’s aerospace industrial base and its leadership in the global market.

“The president and the Congress thus have serious decisions to make in the coming weeks and months,” Giffords said. “And if the president would recommend some manner of course change, we collectively would need to figure out how to make any such change in a way that protects the American taxpayers’ money, preserves crew safety and maintains America’s position as the world leader in space.”

David Thompson, president of the American Institute of Aeronautics and Astronautics here, said if the government’s commitment to human spaceflight wavers, one consequence will be to drive young Americans to eschew space-related fields due to a heightened perception of career uncertainty. He said a stable, long-term federal commitment to human spaceflight is necessary to ensure that space technology retains its allure as a career choice.

“To attract individuals into joining and remaining part of the aerospace work force, we need first to capture their imagination and later provide them with worthwhile, long-term projects to work on,” said Thompson, who also serves as chairman and chief executive of Orbital Sciences Corp.

While manned spaceflight programs, including the shuttle and international space station, make up only about 25 percent of the U.S. aerospace industry’s space and missile sales, and a corresponding fraction of direct employment, Thompson said their influence on the supply of future aerospace professionals is much greater. “Clearly, human spaceflight plays a critical role in ensuring that our country’s young people persist in cultivating their [science, technology, engineering and math]-related talents in order to pursue a career option that inspires them,” he said.

Rep. Pete Olson (Texas), the space and aeronautics subcommittee’s ranking Republican, said he saw it as ironic that the Obama administration is expressing concern about educating and retaining engineers and scientists while pursuing policies that may undermine such efforts.

“Stopping and starting a major program is not how you develop a technical work force, attract workers, inspire future engineers, or stabilize a local and national economy,” Olson said. “Companies and communities are watching us, but so too are impressionable students who may go into science and engineering fields. If we aren’t willing to commit to aerospace, why should they?”