NASA's new human spaceflight policy may have gained the support of Congress, but it still has critics.

Among them is A. Thomas Young, a former director at NASA Goddard Space Flight Center in Maryland.

"My big worry is that we've gone from one unaffordable program to another unaffordable program," he said Tuesday before addressing roughly 200 people at NASA Langley Research Center.

He was speaking about President Barack Obama's controversial plan to scrap NASA's return to the moon mission in favor of promoting the commercial space industry, extending the International Space Station and developing new space technologies.

Unveiled in February, the plan drew bi-partisan criticism from lawmakers who complained about potential job losses. After months of debate, Congress last week approved a modified plan that extended the space shuttle by one flight, and included the development of a heavy-lift rocket to carry people to asteroids and to Mars.

Young, who began his NASA career at Langley during the Apollo era, praised parts of the plan, including the Mars mission and developing more fuel-efficient airplanes. But like the moon mission Constellation, he said NASA's new policy lacks sufficient funding.

"If we don't fix that, then all we're going to do is have another train wreck," he said.

Congress authorized up to $58 billion for NASA for the next three years. The money isn't guaranteed. The bill must pass through appropriation committees, which will meet when Congress returns in November.

Young acknowledged the difficulty of convincing lawmakers to provide NASA with more funding, especially as the nation's economy has yet to recover from the recession. However, it's an area of federal spending that could use a boost, he said.

"The challenges of the next 50 years appear to be as great or greater than those of the past 50 years," he said. "The science budget is clearly not over-funded."

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