Protecting the earth from dangerous space stones may require a bit of asteroid-on-asteroid violence.
Researchers propose to add a new arrow to our pillar of planetary defense: sending small, benign earthly asteroids (NEAs) in large and dangerous areas, in a dramatic game with high stakes of cosmic billiards.
This idea is not as crazy as it may sound, the architects say. [In Pictures: Potentially Dangerous Asteroids]
"It will take a while before we can do this kind of thing, but I think it's promising," said David Dunham, chief mission design engineer at the Arizona-based company KinetX Aerospace last month at a presentation with NASA & # 39; s Future working group in space (FISO).
A cosmic shooting gallery
The earth zooms around in a shooting gallery and shares space with millions of NEAs. These spatial rocks regularly hit our planet, as the world was remembered on February 15, 2013.
On that day, a meteor exploded in the air over the Russian city of Chelyabinsk, creating a powerful shock wave that shattered thousands of windows in the underlying buildings. About 1,500 people were injured, most of them by shards of broken glass to fly.
Scientists believe that the object in Chelyabinsk was only 20 meters wide. And there are plenty of larger – and therefore more dangerous – space test rocks cruising around there in the dark depths, the vast majority of them unseen and unknown.
For example, only one third of the NEAs with a width of at least 460 feet (140 m) has been found and maintained to date, according to NASA officials. This knowledge gap is a bit disconcerting; the probability that the earth will be hit by such a big asteroid in the next 100 years is 1 percent, Dunham said – the same chance that you (or myself or someone else) will die from a car accident. (However, there is good news: NASA scientists believe they have found more than 90 percent of the mountainous size NEAs that are suitable to stop civilization if they hit us, and none of these samples is threat for the near future.)
But we do not just have to sit back and wait for destruction. Indeed, scientists and engineers around the world are working on ways to keep the Earth out of the aderoids.
The most sensational of these is the nuclear bombing strategy, which became famous for the 1998 film "Armageddon". But the real-life version of this technique would rely entirely on robotic spacecraft, not noble self-sacrificing miners.
And researchers regard atomic bombs as a last resort strategy, which can only be used if the asteroid is sufficiently large and discovered so late in the game that no other method would work. Destroying the asteroid with a bomb would generate a lot of space-rock shrapnel that could endanger the earth itself. [Photos: Asteroids in Deep Space]
If time is on our side – if we have years or, ideally, decades – we could use "kinetic impactors" by striking one or more (non-atomic) spacecraft in the threatening asteroid to get rid of it. researchers have said. We could also use the "gravity tractor" method, which would launch a probe to fly with the dangerous NEA. Eventually, the modest gravity tugboat of this spacecraft would push the space stone on a benign trajectory.
And then there's the asteroid billiard idea.
Fighting with rock
This concept, which Dunham explains in his FISO speech, is in fact an upscaled version of the kinetic impactor method.
It involves the launch of a robot spacecraft to a small NEA – a width of about 10 feet (10 m) or so. The probe would land on the asteroid (and attach to it) and then blow up the thrusters to set up a "gravity assist" plane of the earth. (Alternatively, the probe can pick a boulder from a larger asteroid and then fly away with that rock, Dunham said.)
This speed-increasing, job-changing flyby would send the asteroid combo from the spacecraft to the dangerous object. As it approached its target, the rock-riding probe would refine its course using on-board varying instruments, as well as reflectors and transponders placed on the large and dangerous rock, Dunham said.
The collision, when it came, would be much more powerful and effective than a smashup generated by a naked spacecraft that serves as the kinetic impactor, he said.
After all, there would be a lot of extra mass and impulse. Consider, for example, that the Mbozi meteorite in Tanzania, which scientists saw for the first time in 1930, is only 10 feet (3 m) long but weighs 18 tons (16 tons).
There are plenty of little NEAs flying around near Earth to make this strategy a real possibility, Dunham said. Indeed, calculations that he carried out, Natan Eismont from the Space Research Institute of the Russian Academy of Sciences, and their peers suggest that humanity could viablely grasp a dozen of such near-asteroids and would put them in orbits of a retention pattern can send; these cosmic projectiles can then be "activated" when needed.
"So, you'd have a whole bunch of these things ready to fly to every asteroid coming at you," Dunham said.
This asteroid arsenal can be especially useful for dealing with long-period comets, which spend most of their lives in the dark depths of the outer solar system and are therefore very difficult to find and follow, he added.
The asteroid-grabbing idea has applications beyond planetary defense, Dunham said: pre-positioned space rocks can serve as inviting targets for manned reconnaissance efforts. Indeed, NASA had just developed a plan until last year, when the Trump administration canceled the agency's asteroid diversion mission.
Dunham emphasized that the asteroid billiard concept should be studied in much more detail before it can be fully implemented. He would like the idea to be demonstrated for the first time on a benign target stone, referring to the proposed Double Asteroid Redirection Test (DART) mission of NASA as an illustrative example.
If everything goes according to plan, DART throws a spacecraft into the 500-foot-wide (150 m) moon of the asteroid (65803) Didymos in October 2022, in a test of the kinetic-impactor deflection strategy of the handbook.