美国国家公共电台 NPR Trump's Plan To Zap Incoming Missiles With Lasers Is Back To The Future（在线收听）

DAVID GREENE, HOST:

OK. Imagine space lasers and particle beams being used to zap incoming missiles. Sounds like something out of "Star Wars," right? Well, studying the use of those things for real is part of the Trump administration's new defense budget.

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PRESIDENT DONALD TRUMP: Our goal is simple - to ensure that we can detect and destroy any missile launched against the United States anywhere, anytime, anyplace.

GREENE: President Trump there, as he laid out his plan for the nation's missile defense system earlier this year. So how realistic is a space-based missile shield? Well, we asked NPR's Geoff Brumfiel.

GEOFF BRUMFIEL, BYLINE: Trump's not the first president to suggest space lasers. Back in 1983, Ronald Reagan unveiled a similar vision.

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RONALD REAGAN: It is part of a careful, long-term plan to make America strong again.

BRUMFIEL: Reagan called it the Strategic Defense Initiative. The press called it Star Wars. The program imagined an impenetrable shield that would include orbiting lasers and particle beams to zap Soviet missiles before they could hit their targets.

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REAGAN: I know this is a formidable, technical task - one that may not be accomplished before the end of this century - yet current technology has attained a level of sophistication where it's reasonable for us to begin this effort.

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TRUMP: My upcoming budget will invest in a space-based missile defense layer. It's new technology.

BRUMFIEL: That second voice was President Trump speaking in January. Except that new technology? On paper, it looks exactly like the old technology Reagan devoted billions to study.

JAMES ACTON: It's remarkable how similar all this stuff is. I'm actually not sure it's surprising.

BRUMFIEL: James Acton is a physicist at the Carnegie Endowment.

ACTON: You know, at the end of the day, the missile defense is a very, very tough problem. And there are a very limited number of ways of solving that problem.

BRUMFIEL: It's virtually impossible to make a nationwide missile shield without building it in space. It's only by taking the ultimate high ground that one can defend a target as big as the U.S. Despite many billions, Reagan's Star Wars program never produced that shield. But Rebeccah Heinrichs of the Hudson Institute says it's worth reconsidering.

REBECCAH HEINRICHS: It would be negligent on our part not to go back and look at these technologies.

BRUMFIEL: Things have changed since the 1980s. Lasers are much smaller and much more powerful. Satellites that once had to be the size of a school bus can be shrunk to the size of a shoe box.

HEINRICHS: And we can get launch costs down, which has been one of the biggest cost drivers for the whole thing, is just the cost of launch.

BRUMFIEL: Those little satellites, combined with new, cheap commercial rockets, might make a space-based defense program more affordable. Laura Grego is a physicist with the Union of Concerned Scientists, which tracks missile defense. She says, yeah, there's been progress, but much of the technology needed is still so far away. Take particle beams, focused streams of atoms designed to fry a target. Here on Earth, the equipment to generate a powerful beam could be miles long and use as much electricity as a small city. No one's found a way to shrink that technology to satellite size.

LAURA GREGO: I don't know why they think this is practical again.

BRUMFIEL: And there's another problem. A space-based system is constantly moving around the Earth in orbit.

GREGO: A single weapon will almost never be where it's supposed to be for it to work well. So you'd need a constellation of them. And so it becomes really expensive, really quickly.

BRUMFIEL: A 2012 study by the U.S. National Academy of Sciences said a space-based defense system would require many hundreds of satellites. It might cost as much as $300 billion. The president's budget is asking for a few hundred-million for R and D. It remains to be seen whether Democrats, who now control the House, will be willing to pay even that. Geoff Brumfiel, NPR News, Washington.