The first and last of the Apollo program astronauts who walked on the moon urged the House Science, Space and Technology Committee on Thursday to ramp up support for NASA’s human exploration efforts.

Neil Armstrong, who commanded the July 1969 Apollo 11 landing, and Gene Cernan, who led the December 1972 Apollo 17 lunar descent, expressed concerns the U. S. will fall behind its global rivals in science and technology without a means of launching its own astronauts into orbit.

The moonwalkers were joined by Michael Griffin, NASA’s previous administrator, in warning that a loss in skilled workers in the aftermath of the shuttle program’s July retirement, could make it difficult to recover. As administrator between 2005 and 2009,Griffin was an architect of the Bush administration’s Constellation moon program, which was c ancelled in 2010 in response to budget concerns.

All three aerospace veterans recognized last week’s agreement between the White House and Congress to move forward with NASA’s Space Launch System, a strategy to produce a heavy lift rocket to launch the Orion/Multi-Purpose Crew Vehicle on future human missions to deep space destinations.

However, test flights of a less robust version of the SLS would not begin until 2017.

In the meantime, NASA is nurturing commercial companies to carry cargo and astronauts to the International Space Station, duties once assigned to the shuttle. Cargo missions will likely begin next year, human transportation in the 2015-16 timeframe. President Obama proposes additional NASA investments in technology to prepare the nation for the human exploration of an asteroid in 2025 as a step toward a human mission to Mars a decade later.

Armstrong, Cernan and Griffin urged the panel to hasten the schedule and lay out specific destinations for astronauts beyond the space station.

“For a country that has invested so much for so long to achieve a leadership position in space exploration, this condition is viewed by many as lamentably embarrassing and unacceptable,” Armstrong told the lawmakers.

“Most importantly, public policy must be driven by the recognition that we live in a technology driven world, where progress is rapid and unstoppable. Our choices are to lead, try to keep up or get out the way,” said Armstrong. “Leadership, however earnestly and expensively won — once lost — is very difficult and expensive to regain,” he said “The key to American investment in space is a clearly articulated plan and strategy supported by the administration and congress and implemented with all the consistency the budget will allow.”

Cernan was more direct, suggesting NASA pull the shuttle orbiters Atlantis, Endeavour and Discovery from retirement and resume missions until a commercial or government successor is available.

“We stand today at a crossroads,” he told the panel. “If we abdicate leadership in space today, we place not only space exploration at risk, but I believe the future of the country and thus the future of our children and grandchildren. Now is the time to be bold, innovative. It’s not just about space, it’s about the country.”

The House panel turned to Griffin for an opinion on a common concern, China’s rise in space. Currently, only China and Russia are capable of launching humans into orbit.  U.S.and Chinese relations are strained.

“In my opinion, China understands what it takes to be a great power,” said Griffin, who referred back to America’s victory in World War II and persistence in overcoming the Soviet Cold War challenge. “They understand that because we showed them how to do it.”

The House panel seemed sympathetic to their witnesses.

U. S. Rep. Ralph Hall, a the committee’s Republican chairman, acknowledged differences between the Congress and White House over budgets, schedules and deep space destinations, which he characterized as an “important considerations.”

‘If NASA does not move out quickly,  more and more of our industrial base — skilled engineers and technicians — and hard won capabilities are at risk of withering away,” Hall warned.

“This is so important for our young people. As we debate what we want to do with our nation’s human space flight program, we sometimes forget the American people are much less interested in what particular rocket NASA will be building than in why we invested in space exploration in the first place” said U. S. Rep. Eddie Bernice Johnson, the panel’s ranking Democrat. “The benefits of investing in human space flight are clear and compelling.”