It was a plan that read like science fiction: A system armed with an array of space-based X-ray lasers would detect and deflect any nukes headed toward the United States.

President Ronald Reagan saw the proposed Strategic Defense Initiative (SDI) as a safeguard against the most terrifying Cold War outcome—nuclear annihilation. When Reagan first announced SDI on March 23, 1983, he called upon the U.S. scientists who “gave us nuclear weapons to turn their great talents to the cause of mankind and world peace: to give us the means of rendering these nuclear weapons impotent and obsolete.”

From the start, politicians and scientists argued that SDI was overambitious. The technical hurdles required to achieve SDI (which included a number of proposed designs and weapons—not just space-based lasers) seemed so incredible at the time that Massachusetts Senator Edward Kennedy referred to it as ''reckless 'Star Wars' schemes.'' The ‘Star Wars’ moniker stuck. Over the course of 10 years, the government spent up to $30 billion on developing the concept, but the futuristic program remained just that—futuristic. It was formally scrapped by President Bill Clinton in 1993.

Despite criticisms from politicians, many scientists and others thought the SDI was impractical, expensive and dangerous, the concept was developed during a frightening era.

“The Soviets had literally hundreds of ballistic missiles aimed at the U.S., and the idea was that SDI would render all of them obsolete,” says Matt C. Pinsker, adjunct professor of Homeland Security & Criminal Justice at the L. Douglas Wilder School of Government and Public Affairs at Virginia Commonwealth University.

“The practical objection to SDI was that it was too expensive and not technologically feasible. The theoretical opposition to it was that it might ignite an arms race, though this does not make sense because there already was one.”

Vince Houghton, historian/curator at the International Spy Museum in Washington, D.C., says he believes Reagan “truly despised nuclear weapons, and especially despised the threat they posed to the security of the United States. As much as people love to give him grief for what would end up being a trillion-dollar quagmire, or accuse him of wanting Star Wars so that the United States could have a legitimate advantage over the Soviets in a nuclear war, Reagan seemed to truly believe that ballistic missile defense could finally release us from the perpetual, enduring, soul-crushing threat of Armageddon.”

But was the technology even feasible? In the 2000 book Way Out There in the Blue: Reagan, Star Wars and the End of the Cold War, Frances Fitzgerald writes that “a perfect antiballistic missile defense was beyond the reach of technology. It was just a story, and yet to trust the polls, the idea had great popular appeal in the mid-’80s, and many Americans believed such a thing could be built. In that sense the Strategic Defense Initiative was Reagan’s greatest triumph as an actor-storyteller.”

Houghton says scientists and engineers continue to say that if they had the necessary funding, they could have made the technology happen. But he calls that argument problematic, pointing to a 1987 study by the American Physical Society, which brought together some of the nation’s top scientific minds to take measure of all of the systems then under development. The study focused on the technical challenges of SDI, including developing high intensity lasers and particle beams.

“The report concluded that not a single one of the systems then under study or development was even remotely close to deployment,” says Houghton. “It noted that every single system under consideration had to at least improve its energy output by 100 times to be effective. In some cases, as much as a million times.”

Pinsker, however, claims the technology was feasible—if given enough time to develop. “We know this because much of it exists today,” he says. “For modern day examples of this, you can see how the U.S. Navy is placing lasers on its ships and has used them in exercises to take out drones and boats in military exercises.”

Of course this is now. In the 1980s, that kind of technology was rudimentary. Still, Pinsker argues, that was the point of Reagan's initiative—to grind away at the research until the concept became feasible.

“To criticize SDI as being ‘Star Wars’ is like criticizing the Manhattan Project as being ‘Star Wars,’” Pinsker says. “The whole point of both projects was to take theoretical ideas and make them a reality, which eventually both did. It didn't happen overnight with either, and both were incredibly expensive.”

Peter Westwick, an adjunct history professor at the University of Southern California, believes that it was clear at the time that the technology was going to take a long and intensive R&D effort over many years or decades, and even then many technologies would likely not prove attainable.

Partisan debate on the issue had Democrats in Congress questioning the viability of the program, with Louisiana Senator J. Bennett Johnston calling it "absolute folly" and some scientists and members of the media describing SDI as a bargaining chip or bluff. In 1993, The New York Times reported the Pentagon had “rigged a test and falsified other data to make the $30 billion program appear more successful than it was.”

Nevertheless, Westwick says, “I’ve seen no contemporary evidence that it was a bluff, at least for the first few years of the program, and the person whose view counted the most, namely Reagan, certainly didn’t view it as a bluff.”