On February 15, 2013, asteroid 2012 DA14 at 165 feet in diameter and weighing in at 143,000 tons missed Earth by about 17,000 miles having the impact power to wipe out 750 square miles. Coincidently, earlier that same day a meteor exploded over central Russia whose shockwave damaged buildings, smashed windows and injured 1,200 people. These faster-than-a-bullet behemoths traveling through space, render the Earthquite vulnerable to their random trajectories. WWWAn interesting fact to know about asteroids is that not all of them are solid rock, many are huge piles of smaller rocks brought together by their own forces of gravity, and there appears to be a soft dust layer known as regolith covering them that could be as deep as 30-feet.
So, what can we do about it? It’s comforting to know we have the science to intercept asteroids, exampled by Japan’s Hayabusa probe which they landed on, and returned from the potato-shaped asteroid Itokawa, and NASA’s Dawn spacecraft is currently orbiting around 4 Vesta in the asteroid belt; we even crashed NASA’s Deep Impact probe into the comet 9P/Tempel. We can get there, and there are a variety of options being researched to deflect these big stones from a path whose destination is Earth. WWWUnfortunetly only a tiny portion of NASA’s budjet is designated to developing technologies to implement such a mission. That’s due to Congress’ feeling that these collisions are rare, which is true, but what their superficial thinking misses is that it only takes one to take out a city, or even bring us to extinction. An extinction asteroid is one that’s about six miles in diameter as the one that took-out the dinosaurs. Fortunately, there is private research being conducted worldwide that we’ll be exploring.
The most obvious way most of us think of to rid ourselves of this threat is a nuclear bomb, and it is a viable option. The most common sense method is to deliver and detonate a nuclear device strategically near the asteroid, knocking it off its course. WWWRobert Weaver is a scientist at the Los Alamos National Laboratory (LANL). He runs simulations on the Cielo supercomputer to determine our ability to use a one-megaton bomb—50 times the power than the one dropped on Hiroshima—to annihilate an Earth bearing big rock and breaking it into pieces, causing most of them to miss Earth by changing their direction, and more importantly, that those still making it to Earth would be small enough to burn up in the atmosphere.
WWWWeaver says, “From my perspective, the nuclear option is for the surprise asteroid or comet that we haven’t seen before, one that basically comes out of nowhere and we have just a few months to respond to it.” His study is comprehensive in the many factors that determine how the asteroid will respond to such force, and it includes composition, the size, and its porosity.
WWWUnlike the movie Armageddon with Bruce Willis, there’s no need to drill into the center to deposit the bomb. His simulations for rocks the size of Itokawa show a surface explosion does the job, the center being the most effective by far. For larger ones he will soon be in collaboration with Lawrence National Laboratory where they will combine their funding and computational resources for solutions.
Just a Spacecraft
A spacecraft could be flown to, and impact an asteroid, nudging it off course. It could also fly near and follow the asteroid with the spacecraft’s slight gravitational pull tugging on it and changing its course—a one-degree change of course could mean missing Earth by millions of miles, given enough time. It’s likely that NASA and its partner agencies would be able to detect an asteroid ten to fifteen years out, which is plenty of time to send a craft to fly in formation with it. Astronauts Edward Lu and Stanley Love were the first to propose this concept.
Dr. Massimiliano Vasile, from the University of Glasgow feels the best way to divert a killer rock is to deploy a swarm of mirror satellites to focus beams of concentrated sunlight onto its surface as long as its applied well in advance of the impact. Concentrating sunlight heats the rock converting the surface material to gas, which will then create a rocket like thrust nudging the asteroid into a new orbit. Dr. Vasile says, “Our studies show this technology is genuinely feasible, and unlike methods where an explosion or impactor is used to divert the asteroid, there is no further risk from fragments.” WWWHe and his colleagues concluded using a nuclear device might be the most effective method for a small asteroid of about 300 feet in diameter, but with larger ones there is a risk of splitting them into unpredictable and dangerous fragments. They calculated ten mirror satellites with metal surfaces of 60 feet in diameter orbiting an asteroid 500 feet in diameter focusing sunlight to the surface would push it off course in 200 days, or 1,000 satellites with six foot diameter mirrors could do it in 90 days.
Giant Space Laser
Researchers at the University of California and California Polytechnic State University are proposing launching an array of solar powered lasers into orbit that would deflect or vaporize incoming asteroids. The system is known as DE-STAR, or Directed Energy Solar Targeting of Asteroids an exploRation, and would use the sun’s energy, focusing it into laser beams that could evaporate asteroids—a directed energy orbital defense system.
WWWGary Poly from Polytechnic said, “This system is not some far-out idea from Star Trek. All the components of this system pretty much exist today. Maybe not quite at the scale we’d need, scaling up would be the challenge, but the basic elements are there and ready to go.
A swarm of pebbles could deflect an asteroid if launched early enough. British researchers from the University of Strathclyde have calculated that 1,000 pounds of pebbles would deflect an 800-foot asteroid 22,000 miles if it met it eight years out, or about three orbits before the predicted Earth impact. The swarm would be launched in a single rocket, then directed at the asteroid in a tight formation, the pebbles being too small to fragment into dangerous smaller pieces.
Sung Wook Paek, a graduate student at MIT’s Department of Aeronautics and Astronautics won the 2012 Move an Asteroid Technical Paper Competition by proposing to move a threatening asteroid with a cloud of paint pellets. This is similar to the pebbles method plus increasing the reflectivity of the surface with a lighter color and inducing greater solar radiation pressure —the force exerted on objects by the sun’s photons.
WWWHe proposes launching two rounds from a spacecraft at close distance to cover both the front and back of the rock with white paint powder. View video below:
In his proposal, Paek used the asteroid Apophis as his test model. Apophis is 1,066-foot diameter, 27-gigaton rock that will make a close pass to Earth in 2029 and then again in 2036 as it orbits back toward Earth’s path. For an object of that size, Paek figures it would require five tons of paint. The pellets would burst on impact and splatter a five-micrometer-layer on the surface. He also calculates it would take 20 years for the cumulative effect of solar radiation pressure to pull it off Earth’s trajectory. WWWHis plan is to manufacture the paintballs in space, perhaps on the International Space Station and transferred to a spacecraft, rather than attempt launching them from Earth, as the turbulence may rupture them.
By the end of 2020 NASA hopes to identify and track 90 percent of all threatening objects larger than 450-feet in diameter. We can only hope that from our present utter helpless vulnerability, that at least a few of these methods have actually been tested, and offers us viable options against such a formidable and devastating foe. From the proposals explored here, that hope seems very real.