MOSCOW — When Sputnik took off 50 years ago, the world gazed at the heavens in awe and apprehension, watching what seemed like the unveiling of a sustained Soviet effort to conquer space and score a stunning Cold War triumph.

But 50 years later, it emerges that the momentous launch was far from being part of a well-planned strategy to demonstrate communist superiority over the West. Instead, the first artificial satellite in space was a spur-of-the-moment gamble driven by the dream of one scientist, whose team scrounged a rocket, slapped together a satellite and persuaded a dubious Kremlin to open the space age.

And that winking light that crowds around the globe gathered to watch in the night sky? Not Sputnik at all, as it turns out, but just the second stage of its booster rocket, according to Boris Chertok, one of the founders of the Soviet space program.

In a series of interviews in recent days with the Associated Press, Mr. Chertok and other veterans told the little-known story of how Sputnik was launched, and what an unlikely achievement it turned out to be.

Mr. Chertok couldn’t whisper a word about the project through much of his lifetime. His name, and that of Sergei Korolyov, the chief scientist, were a state secret. Today, at age 95 and talking to a small group of reporters in Moscow, Mr. Chertok can finally give full voice to his pride at the pivotal role he played in the history of space exploration.

“Each of these first rockets was like a beloved woman for us,” he said. “We were in love with every rocket, we desperately wanted it to blast off successfully. We would give our hearts and souls to see it flying.”

This very rational exuberance, and Korolyov’s determination, were the key to Sputnik’s success. So was happenstance.

As described by the former scientists, the world’s first orbiter was born out of a very different Soviet program: the frantic development of a rocket capable of striking America with a hydrogen bomb.

Because there was no telling how heavy the warhead would be, its R–7 ballistic missile was built with thrust to spare — “much more powerful than anything the Americans had,” Georgy Grechko, a rocket engineer and cosmonaut, told AP.

The towering R–7’s high thrust and payload capacity, unmatched at the time, just happened to make it the perfect vehicle to launch an object into orbit — something never done before.

Without the looming nuclear threat, Russian scientists say, Sputnik would probably have gotten off the ground much later.

“The key reason behind the emergence of Sputnik was the Cold War atmosphere and our race against the Americans,” Mr. Chertok said. “The military missile was the main thing we were thinking of at the moment.”

When the warhead project hit a snag, Korolyov, the father of the Soviet space program, seized the opportunity.

Korolyov, both visionary scientist and iron-willed manager, pressed the Kremlin to let him launch a satellite. America was already planning such a move in 1958, he pointed out, as part of the International Geophysical Year. But while the government gave approval in January 1956, the military brass wanted to keep the missile for the bomb program, Mr. Grechko, 76, said in an interview. “They treated the satellite as a toy, a silly fantasy of Korolyov.” America had its own satellite program, Mr. Grechko said. “The Americans proudly called their project ‘Vanguard,’ but found themselves behind us.”

The Soviet Union already had a full-fledged scientific satellite in development, but it would take too long to complete, Korolyov knew. So he ordered his team to quickly sketch a primitive orbiter. It was called PS–1, for “Prosteishiy Sputnik” — the Simplest Satellite.