Why man instead of machine?

Yet at least for the US, the geopolitical reasons for putting humans in space that held sway during the cold war have lost their punch since the fall of the Berlin Wall, some analysts say. The old enemy is gone. And more avenues have opened for exhibiting economic and technological prowess in areas such as biotechnology and information science. There, Asia in general and China in particular are striving to position themselves among the global leaders.

As if to warn that congressional support can't be taken for granted, the US House of Representatives fired a legislative warning shot in 1993. House lawmakers, angered by space-station cost overruns, approved funding for the project by one vote. Twelve years later, that warning still reverberates. During last week's hearings with Dr. Griffin, lawmakers on the House Science Committee welcomed him warmly, then politely expressed frustration at what they saw as continued reshuffling of key pieces of the president's agenda. One message lawmakers were trying to make: We need a clear, consistent, timely, and fiscally credible story if we are to help fend off members of Congress critical of the manned spaceflight program.

Outside Congress, many scientists see NASA's reinvigorated push coming at the expense of research programs that in some cases have the potential to bear more immediately on human well-being. In a position statement released early last month, for example, the American Geophysical Union criticized cuts in the White House budget for space and earth sciences, which feed activities as diverse as weather forecasting, earthquake research, and unmanned space exploration. The organization argued that NASA was being asked to do more than the White House and Congress were willing to fund.

"I'm one of the most durable advocates for space exploration around," says James Van Allen, one of the deans of US space science and a professor emeritus at the University of Iowa. But beyond Apollo's moon landings and missions to service the Hubble Space Telescope, he adds, human spaceflight hasn't contributed as much to humanity's understanding of the cosmos as increasingly sophisticated unmanned probes.

"It's the cost," he says. "If it was easy to do, I'd be all for it." But with record federal deficits, an increasingly expensive war in Iraq, problems with Social Security, and other demands on the federal purse, the benefits to science from human spaceflight over the past 10 to 15 years have not justified the cost, he adds.

Public support for the space program varies. Surveys indicate that Americans will rally around the program in times of crisis. But between disasters, backing is fairly stable, though less robust.

"Human spaceflight in a democracy is hard," Dr. Johnson-Freese acknowledges. "If you ask people in a democracy if they support space, the majority answer is, 99 times out of 100, yes.... If you then ask the same group to rank priorities for funding, space comes in pretty much dead last. That's been consistent since Apollo."

Moreover, surveys that ask about funding levels for the space program typically show a plurality, if not a slight majority, agreeing that funding levels are about right - regardless of the state of the budget at the time the question is asked.

As time passes and more global players emerge on the wings of technologies that don't require putting humans in orbit, "the rationales that have traditionally been invoked are dwindling," notes Alex Roland, a former NASA historian, currently a history professor at Duke University.

The Smithsonian's Dr. Launius breaks these rationales down into five broad themes: geopolitics, human destiny, national security, economic competitiveness, and scientific discovery.

Yet for many spaceflight supporters, what appears to be a shrinking list of reasons to put humans in space may instead reflect a shift in emphasis as global conditions change.

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