On a sultry afternoon in July 1969, a few leading citizens of Huntsville, Ala., hoisted a former enemy rocket engineer onto their shoulders and paraded him around the courthouse square before a happy crowd. Their celebration of the Apollo 11 splashdown marked a triumph both for the engineer - Wernher von Braun - and for the bureaucracy cobbled together just 11 years earlier to create the U.S. civil space program.

If past is prologue, that moment held echoes of NASA's tangled origins and foreshadowed the situation its managers face today, 50 years after the agency set up shop in a century-old townhouse across Lafayette Square from the White House. A cloud hung over the Huntsville throng that day, as it does over NASA at the beginning of its second half-century. Then, as perhaps now, the agency's spectacular accomplishments were about to collide head-on with shifting national priorities in an ever-changing geopolitical scene.

Huntsville's Apollo 11 "splashdown party" after the first lunar landing mimicked a more spontaneous event that erupted around the Madison County courthouse on Jan. 31, 1958, when von Braun and his famous "Peenemunde Rocket Team" pushed Explorer I into orbit and answered the challenge of Sputnik I in the first lap of the Cold War space race.

The Huntsville Germans - roughly half of whom had been members of the Nazi party before World War II ended - were on their way out by the time von Braun, also a former party member, took his triumphal ride. When Neil Armstrong made his "small step for [a] man," the Vietnam War already was gobbling up federal funds those in Huntsville doubtless would rather have seen spent locally to continue von Braun's ambitious plans for human space exploration.

Instead, a dry dozen years followed for NASA. "RIFs," the dreaded "reductions in force," swept the agency and its contractors as von Braun's cherished Saturn V was abandoned in the wake of the U.S. victory in the superpower space race. NASA, which had matched and then exceeded the Soviet Union in human spaceflight, soon lost its ability to send humans beyond the atmosphere. After the Apollo-Soyuz Test Project ended on July 24, 1975, it would be almost six years before the space shuttle Columbia returned U.S. astronauts to space.

Today, the U.S. agency is facing another gap in its ability to orbit humans, and another war, with fronts in Iraq and Afghanistan, is gobbling up the resources that could be used to narrow it. And the outlook for the space program is even cloudier today than it was in 1969, given the uproar in the financial markets. The space shuttle, a compromise follow-on to Saturn V, is scheduled to retire by the end of 2010. Given Russia's reemergence as a potential threat, Congress is distinctly queasy about continuing to rely on another former enemy to get U.S. astronauts to and from space after that.

The follow-on NASA is developing, an Apollo-like capsule called Orion and a hybrid solid/liquid-fueled rocket dubbed Ares, probably won't be ready to carry astronauts until at least five years after the last shuttle flight. When it is, its first job will be to deliver crews and a little cargo to the International Space Station.

The ISS is arguably an engineering triumph for NASA comparable to the Moon landings, in difficulty if not historic impact. Humans have been living on the station continuously for eight years now, operating through an intricately choreographed construction project that has merged hardware from three continents into a functioning outpost more than 200 mi. above Earth's surface.

But international cooperation in space is far from assured today. Russia's recent military incursion into Georgia has put a political strain on the international partnership that built the ISS, a strain that is every bit as dangerous to its continued operation as torn solar arrays and its malfunctioning solar alpha rotary joint. As it celebrates 50 years in space, NASA faces the prospect of watching $100 billion worth of hardware - most of it made in America - orbit overhead without U.S. astronauts on board.

As a practical matter, the station is the only game going in human spaceflight right now. NASA is studying a continuation of shuttle missions beyond 2010, and while it may be technically feasible, so far the jury is out on how to pay for it. Although shuttle program manager John Shannon believes there may be a way to keep the shuttle flying while Ares I and Orion are completed, that would require Congress to fund two major human spaceflight programs at a time when it is planning to use funds freed by shutting down the shuttle to develop its successor.