How to use a human-made Doomsday device to defeat a universe-made Doomsday device.
The 1998 film Armageddon has been the butt of many jokes due to its voluminous scientific errors, but its basic premise—nuking asteroids that might impact Earth—is a genuine line of research in the worldwide planetary protection community.
Two recent papers anticipate how nukes could be employed to either deflect an asteroid on a collision course with Earth, or blow it into smaller, less hazardous chunks. One, published in Acta Astronautica, proposes a vehicle called the Hypervelocity Asteroid Mitigation Mission for Emergency Response (HAMMER), which could be deployed to nudge asteroids away from Earth, or in a worst case scenario, as a delivery mechanism for a nuclear device.
Another, published in the Journal of Experimental and Theoretical Physics, details how scientists blasted miniature mock asteroids with lasers to simulate how a nuclear detonation on a killer asteroid might play out in real life.
Both papers suggest it will take a lot of planning and foresight to deal with an asteroid that is intent on making human civilization go the way of the non-avian dinosaurs.
The HAMMER team, led by University of Maryland aerospace engineer Brent Barbee, focused on the case study of asteroid 101955 Bennu, a half-kilometer wide rock that has a 1 in 2,700 chance of impacting our planet on September 25, 2135, which is a relatively high probability of collision for an asteroid. Bennu, which will be visited by NASA’s OSIRIS-REx spacecraft later this year, would generate about 80,000 times as much energy as the atomic bomb dropped on Hiroshima if it were to collide with us, so it’s definitely a credible threat to life on Earth.
So...nuke the hell out of it? That’s Plan B, said Barbee’s team. Plan A is launching several iterations of the HAMMER concept, each measuring nearly 30 feet tall, decades before projected impact. These ships would act as “kinetic impactors,” meaning that they would crash into the asteroid to gently nudge it into a non-apocalyptic trajectory. The longer the lead time, the fewer HAMMER launches would be needed, with about seven to 11 spacecraft required to deflect Bennu 25 years before impact.
“If we only had ten years from launch, we would need to hit Bennu with hundreds of tons of HAMMER mass just to barely deflect it off of an Earth-impacting path, requiring dozens of successful launches and impact at the asteroid,” said study co-author Megan Bruck Syal, a physicist at Lawrence Livermore National Laboratory, in a statement.
Bennu has been tracked and studied since its discovery in 1999, but what would happen if a previously unknown asteroid was found to be barreling toward Earth with only years or even months before impact? That’s when the nuclear option might have to be explored.
One example of this, which will be assessed in forthcoming research from the HAMMER team, is a nuclear detonation at a distance from the hazardous asteroid, which would vaporize its surface causing it to be deflected from its deadly course.
The Journal of Experimental and Theoretical Physics study, meanwhile, found that it might also be possible to blast apart asteroids into tiny pieces that would hurtle past Earth. Conducted by researchers from Russia’s Rosatom State Nuclear Energy Corporation and the Moscow Institute of Physics and Technology, the study was based on laboratory experiments in which tiny asteroid models were blasted with lasers to simulate nuclear explosions.
Informed by the 20-meter-wide meteor that dramatically burst over the Russian city of Chelyabinsk in 2013, the researchers suggested that blowing up a 200-meter-wide asteroid into 10-meter chunks could mitigate the damage of a surprise asteroid, detected only years before the impending impact.
The team estimated that such an object could be neutralized at a distance of 13 million kilometers from Earth using a nuclear bomb with at least three megatons of explosive power. This would send most debris past Earth, leaving the small remnants—about half the size of the Chelyabinsk meteor—to burn up in the atmosphere.
The Russian team considered directly impacting objects with nuclear bombs, especially on weak spots like cavities or craters, or even burying bombs within an asteroid for a more efficient pyrotechnic result.
This approach would be riskier than deflecting an asteroid, but requires much less lead time—a spacecraft launched 15 days before the projected impact could reach and destroy the asteroid at a the target distance (assuming that the spacecraft had already been prepared for spaceflight before this window, a process that normally takes years). Consider it the emergency option.
The Chelyabinsk meteor, which was not detected until it hit, was a blunt wake-up call from the universe about the existential perils of living on a planet. Luckily, that object burst before it could do much damage, but the next surprise visitor might not be so easily neutralized. That’s why in addition to planning for an impact, it’s crucial that scientists continue to catalog and track hazardous asteroids so that when one comes knocking, we’ll be ready—potentially g’d up with nukes.
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