NASA had planned the final launch of its space shuttle program for today, and by the time readers see these words, we’ll know whether the launch proceeded as scheduled.

The tendency of shuttle launches to be delayed because of bad weather or technical problems reminds us that while the shuttle initially promised to make space travel routine, space exploration is still an uncertain business.

Mention “space shuttle,” and many of us automatically think of the explosion of the space shuttle Challenger on Jan. 28, 1986, a disaster that claimed the lives of the entire crew, including schoolteacher Christa McAuliffe.

Tragedy repeated itself on Feb. 1, 2003, when the space shuttle Columbia broke apart upon re-entry, killing everyone aboard.

Although those accidents offered a grim lesson in the continuing dangers of space exploration, the shuttle program, which had its first launch in 1981, became an icon of American optimism, a testament to American supremacy in space.

Louisiana residents had a special connection with the shuttle program because its fuel tanks were made at NASA’s Michoud Assembly Facility in New Orleans. Sean O’Keefe, who had strong Louisiana ties and served as NASA administrator before a stint as chancellor of LSU’s Baton Rouge campus, gave the state another connection with the shuttle program.

Critics suggested the political compromises necessary to fund the space shuttle program created a vehicle that was a “shuttle to nowhere,” its relatively low orbit diminishing the reach of its science.

But the shuttle carried many satellites into space, as well as the Hubble telescope, an instrument that dramatically expanded knowledge of the heavens.

Shuttles also enabled the construction of the International Space Station, a promising outpost for research.

Plans call for NASA’s shuttles to be replaced by another kind of space vehicle, but in the meantime, American astronauts will be forced to hitch rides to the space station on Russian spacecraft. That’s an embarrassing development for the United States — and an indication of the poor planning and inconsistent funding that have compromised America’s position as a leader in space exploration.

Part of the problem is that NASA relies on support from presidents and members of Congress who are asked to fund space missions that, in many cases, won’t be completed while these politicians are still in office. The political culture of Washington doesn’t lend itself to the kind of long-term thinking that space exploration requires.

There is much talk about an increased role for the private sector in space exploration, and we are not opposed to that possibility. But we also know that most of history’s great feats of human exploration, including the European exploration of North America, unfolded through a collaboration between government and private interests. We suspect that the future of space exploration will continue to rely upon such partnerships.

The precedent of European exploration also reminds us that when nations relinquish their roles in leading exploration, they cease to be major powers. Spain and France once affirmed their stature as great world powers by sending explorers into the vastness of the American wilderness. In turning away from such ambitions, they largely ceded the international stage to others.

The lessons for America seem clear as this nation closes one chapter of space exploration and ponders its future role in exploring the heavens.

“I no longer expect to see boot prints on Mars during my lifetime,” science writer Dennis Overbye recently wrote in The New York Times, “nor do I expect that whoever eventually makes those boot prints will be drawing a paycheck from NASA, or even speaking English.”

Such pessimism regarding America’s future leadership in space is understandable, but we hope the president and members of Congress, as well as their successors, find the will to expand, rather than diminish, the U.S. presence in space.