Here’s why putting a missile defense system in space could be a bad idea

The protective technology could also be used to shoot down other countries’ satellites

missile defense system

ROCKET BLOCKER  The United States’ ground-based missile defense system, shown here in a test conducted at Vandenberg Air Force Base in California, aims to protect the U.S. from ballistic missiles.

U.S. Missile Defense Agency

COLUMBUS, Ohio — A beefed-up missile defense system might seem like a good idea in a time of heightened nuclear tensions. But such enhancements could have dangerous consequences.

The current U.S. missile defense system isn’t all it was cracked up to be, performing unreliably in tests, physicist and missile defense expert Laura Grego argued April 14 at a meeting of the American Physical Society. Enhancing the system’s power, however, by building missile defense in space, for example, might put the world on a slippery slope to space warfare, she warned.

The worries come against the backdrop of North Korea’s nuclear weapons and missile tests (SN: 8/5/17, p. 18) and an upcoming missile defense review from the U.S. Department of Defense, expected in May. That review could accelerate efforts to revamp the current system, including schemes to strike at missiles from space.

“Missile defense is once again having its day,” said Grego, of the Union of Concerned Scientists in Cambridge, Mass., at a news conference.

Boosted by a rocket engine, a ballistic missile sails into space before releasing a warhead that plummets to its target under the force of gravity. Missile defense systems are designed to shoot down such missiles in flight. But today’s technology doesn’t fully protect the United States. Tests of the country’s system have literally been hit or miss, sometimes succeeding and sometimes failing to intercept the target.

Although not specifically designed for it, a system capable of stopping intercontinental ballistic missiles can also be used to destroy satellites, since some satellites travel at altitudes and speeds comparable with those of missiles. There’s some precedent for this: In 2008, the United States shot down one of its satellites, which was malfunctioning. Likewise, China demolished one of its fleet in 2007. So if countries around the world start ramping up their missile defense, that could have the world tiptoeing closer to space warfare.

Using such antisatellite weapons could have major repercussions, including creating long-lasting space debris that could damage spacecraft (SN Online: 8/15/11). “If you ever expect to use space again, you don’t start blowing things up in space,” Grego said.

Even if countries refrain from using ground-based missile defense systems for antisatellite capabilities, there’s another push to bring weapons into orbit. U.S. politicians have repeatedly floated the idea of taking missile defense to space as a way to get around limitations of ground-based systems. In a real-world scenario, ground-based missile defense systems have to cope with near-impossible conditions: For instance, in addition to releasing a weapon-carrying warhead, a missile might deploy a cloud of decoys that look similar to a real warhead, confounding the defense system’s attempts to take out the real thing. Unlike land-based systems, space-based missile defense could take out a missile before it has a chance to release its decoys.

But putting missile defense in space would also have antisatellite implications. While enhancing existing systems would strengthen the current U.S. capability to reach satellites orbiting at relatively low altitudes, creating the first space-based missile defense system could also threaten satellites in higher orbits, Grego said. That’s where GPS satellites are located, along with other equipment that provides essential services.

Many scientists have panned the idea of a space-based missile defense system for various reasons. A 2012 study from the National Research Council, for example, reported that the system would be prohibitively expensive and impractical. Still, the political push for such a project persists.

Putting weapons in space has generally been a taboo that the world has been hesitant to break.  But President Donald Trump said that his national strategy recognizes that “space is a war-fighting domain, just like the land, air and sea,” in a March 13 speech to military personnel in San Diego. He then suggested creating a new military branch dubbed the “Space Force.”

MIT physicist and missile defense researcher Theodore Postol has a different idea for defending the United States, at least from North Korea. A drone, flying above the waters off of North Korea, could carry an interceptor that could shoot down a missile in the early stage of flight, he said at the news conference.

Such a system would have the benefit of avoiding the problem of decoys by shooting down a missile before it had a chance to release any fakes. And the project could be accomplished with proven technology, Postol says, abandoning the “preoccupation with science fiction” that he says underlies some enhanced missile defense schemes.

Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award.

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