Explorers Lewis and Clark didn’t know what dangers waited for them when they and the Corps of Discovery set out for the Pacific Northwest two centuries ago.

Nor could they have envisioned how their efforts would help alter the land, the nation and the people in the coming 200 years. They certainly didn’t anticipate that cities, mountains, rivers and schools would bear their names in honor of their contributions to the expansion of the nation. Like generations of explorers before and after, they risked their lives confronting the unknown.

At Cape Canaveral today, weather and technology permitting, America will launch another corps of Discovery. The seven- member crew of the space shuttle by that name is scheduled to take off on the first U.S. manned space venture in 2 1/2 years. That’s how long it has taken – coincidentally about what it took Lewis and Clark to complete their own 8,000-mile round trip – to address the safety concerns raised when the last shuttle, the Columbia, broke up on re-entry on Feb. 1, 2003.

Probing space was Buck Rogers fantasy until the 1950s, when Sputnik made it a geopolitical challenge, a test of technological superiority. Ultimately it matured into an enterprise that harnessed adventurism to promote scientific achievement.

But the investment is costly and the returns are, in many ways, as uncertain for the crew of Discovery as they were for the Corps of Discovery. Mission Commander Eileen Collins doesn’t know what entries the upcoming flight will make in the logbook of human advancement but she knows why it must go on.

“We’re a nation of explorers,” Collins said in an interview posted on NASA’s Web site. “We are the kind of people who want to go out and learn new things, and I would say take risks, but take calculated risks that are studied and understood.”

That’s a sentiment Cheney astronaut and Columbia crew member Michael Anderson would have endorsed. Will it take another 200 years to calculate whether the monetary expense of the NASA program and the personal risk to the astronauts are a reasonable price to pay for the returns of exploration?

Perhaps not. As Joe Bruce, director of children’s ministries at Hamblen Park Presbyterian Church, put it during a tribute to Anderson: “The first person who will walk on Mars is in school today.”