Deflecting Doom: How Sandia Research Could Save Earth from Asteroids
“I started working through the logic of how I could deflect a miniature asteroid in a laboratory just like in outer space,” Moore said. “A key fact was that asteroids in outer space aren’t attached to anything. But in a lab, everything is pulled down by Earth’s gravity, so everything is held in place by its gravitational attachment to something else. This wouldn’t let our mock asteroid move with the freedom of one in outer space. And mechanical attachments would create friction that would perturb the mock asteroid’s motion.”
The solution was to release the mock asteroid into the free space of vacuum, leading to the X-ray scissors concept.
To simulate a possible code red, Moore’s team placed a tenth of a gram of asteroid-like material — in this case, silica — in the target chamber of the Z machine, which reaches the temperature of the sun. The material was suspended by very fine foil, eight times thinner than a human hair, that instantly vaporized when Z fired. The process, termed “X-ray scissors,” untethered the sample material and left it free-floating, unaffected by gravity, just as the machine’s X-ray burst struck it. The velocity and impact of the target mass were noted. Researchers believe they can model the change in velocity exerted by a nuclear explosion near an asteroid free-floating in space.
Future Steps and Implications
“It was a novel idea,” Moore said. “A mock asteroid is suspended in space. For a one-nanometer fall, we can ignore Earth’s gravity for 20 millionths of a second as Z produces a burst of X-rays that sweeps over the mock-asteroid surface 12.5 millimeters across, about the width of a finger.
“The trick is to use just enough force to redirect the flying rock without splitting it into several equally deadly subsections advancing toward Earth,” Moore said, referring to a real intercept scenario like the recent NASA DART experiment.
The experiments, reported in the September 25 Nature Physics issue, are the first steps to creating a library of induced changes in asteroidal velocity to be consulted when an actual asteroid is analyzed by laser to determine its contents and its mass and velocity are telescopically known.
“Some asteroids are believed to be held together loosely — so-called ‘rubble piles’ — and how that would respond in the explosion will require more complicated mathematics. But without this capability, we would have to rely on practice missions in space, which are few and costly.” NASA has only done one such mission to date, he said, and it involved a different deflection mechanism — kinetic impact — that wouldn’t be suitable for the most Earth-threatening asteroids.
The team also has questions about fundamental properties of asteroid material under these extreme conditions — how the relationships between a material’s density, pressure and temperature change during asteroid deflection, which is also relevant to planetary formation, planetary impacts and even the robustness of walls for future fusion reactors.
