When planetary scientist H. Jay Melosh attended a meeting between nuclear weapons designers from the United States and the former Soviet Union in May 1995, he was surprised by how eagerly the ex-Cold Warriors sought to work together against an unlikely but dangerous extraterrestrial threat: asteroids on a collision course with Earth.
After Edward Teller, father of the American hydrogen bomb, urged others in the session at Lawrence Livermore National Laboratory to consider building and orbiting large, new, nuclear weapons for planetary protection, some top Russian weaponeers in attendance voiced their support.
“It was a really bizarre thing to see that these weapons designers were willing to work together—to build the biggest bombs ever,” said Melosh, a geophysicist at Purdue University and expert in space impacts who has an asteroid named after him.
Ever since, he has been pushing back against relying on nuclear bombs for the Earth’s defense, arguing that a non-nuclear solution—diverting the trajectory of asteroids by hitting them with battering rams — is both possible and much less dangerous.
But Melosh’s campaign suffered a setback last month when the Obama Administration’s new Energy Secretary, Ernest Moniz, signed an agreement with the Russians that the Americans said could open the door to new collaboration between nuclear weapons scientists on asteroid defense. The topic has been particularly interesting to the Russians since an asteroid the size of a tour-bus exploded high in the skies of Russia’s Chelyabinsk region last February.
President Barack Obama has committed the United States to seeking a world without nuclear weapons, pushed for joint reductions in the U.S. and Russian nuclear arsenals and sought tighter security for nuclear explosives worldwide. “When we fail to pursue peace, then it stays forever beyond our grasp,” Obama said during his landmark speech in Prague in April 2009.
But in recent years, advocates of the use of nuclear weapons to counter space threats have been gaining ground. NASA is spending hundreds of thousands of dollars a year to study the idea, and the U.S. nuclear weapons laboratories are itching to work with the Russians on it. Moreover, weaponeers in both countries are citing the asteroid threat as a reason to hold onto—or to build—very large yield nuclear explosives, which have little terrestrial justification.
There are a few impediments, such as the 1967 Outer Space Treaty signed by 129 countries, which prohibits deploying nuclear weapons in space, and other international treaties that bar nuclear weapons testing anywhere, including in space. Many planetary scientists are leery of the idea and some experts worry that radioactive debris from such a nuclear explosion could itself wreak havoc on Earth.
Outside the world of weaponeers, the idea can evoke humor, as exemplified by the kitschy 1998 Bruce Willis action film “Armageddon,” which shows a team of deep-sea oil drillers landing on an Earth-bound asteroid to implant a nuclear warhead that, at the last moment, separates the rock into neat halves that just miss Earth. Film critic Kenneth Turan called it “sporadically watchable.”
But in real life, Bong Wie, the director of Iowa State University’s Asteroid Deflection Research Center, has a three-year, $600,000 grant from the National Aeronautics and Space Administration to design a “hypervelocity nuclear interceptor system,” basically an missile-borne, nuclear explosive fitted with a battering ram. The ram would separate from the bomb before impact, gouging a crater in the asteroid so the bomb could then blast it apart.
Wie’s plan is hardly Teller’s grand vision of a space-based nuclear asteroid shield. He proposes using off-the-shelf land-based missiles and explosive warheads currently in the U.S. stockpile to intercept large, city-shattering asteroids that are less than about 10 years from slamming into the Earth, when time is too short to nudge them into a new orbit.
These Earth-defending missiles, he said in an interview, could be launched years in advance or even on short warning, although a later defense increases the likelihood that large chunks of radioactive debris will rain onto the planet’s surface. Wie argues that, even in this case, smaller pieces would burn up in the atmosphere and strikes by the remaining rocks would be less damaging than a direct hit by an intact asteroid.
The next logical step, Wie says, would be to test his plan by launching a missile and dummy warhead to strike an asteroid, at a cost of around $500 million, to see if his two-stage design could work. But so far this is just a concept.
Enthusiasm at the nuclear weapons labs
Robert Weaver, a research scientist at Los Alamos National Laboratory where U.S. nuclear weapons are designed, is also among those who have studied the effects of such detonations on asteroids. He used the Energy Department’s “Cielo” supercomputer—which the lab calls its “frontline” computer for simulating nuclear effects.
In a video that the laboratory posted on YouTube in 2012 , Weaver says his objective has been to understand how an “energy source of this magnitude”—his euphemism for a nuclear weapon—could “really disrupt this asteroid and prevent the hazard to the entire Earth.”
Los Alamos spokesman Fred DeSousa said that Weaver could not discuss his work, and the lab could not provide details of his funding, due to the government shutdown. Another source at the laboratory said a handful of other scientists have also worked part-time in recent years on the problem of Earth-crossing asteroids, including research physicist Cathy Plesko, who has also used computers to model asteroid blasting.
Keith Holsapple, an engineering professor at the University of Washington, said NASA has given him a five-year, $1.25 million research grant to study whether an impact device or a nuclear explosion could deflect an Earth-bound asteroid from its path. He and others say studies have shown these are the only two approaches that could work.
Holsapple says he is using a device called a gas gun at NASA’s Ames Research Center in California to study the impactor, while separately producing computer simulations of a nuclear blast, employing software originally developed for the nation’s weapons program.
“When we first started looking at this about a dozen years ago, very early on, the nuclear option was the one that everyone said, ‘Hey, we can do this,’” Holsapple said in an interview. “But that was politically incorrect, so there was a lot of hesitation for anyone to say that this is a solution.”
The leading proponent of the nuclear solution is David S.P. Dearborn, a research physicist and nuclear weapons designer at Lawrence Livermore National Laboratory in California, presently engaged in refurbishment of the U.S. W-87 warhead—a weapon with an explosive force estimated at more than 375 kilotons, or 29 times the power of the bomb that flattened Hiroshima(it has about a third of the explosive power of the largest bomb in the U.S. arsenal).
Wie called Dearborn “the sort of senior person in this community” of those studying the nuclear option. “I am just following in his footsteps.” Melosh said Dearborn “is reasonable, he tends to be pretty persuasive, he comes across as not being a rabid advocate of nuclear weapons for their own sake. He’s quietly persistent.”