New ideas for deflecting Earth-threatening asteroids

and colleagues with funding from the European Space Agency, a fleet of eight or more spacecraft, each carrying a laser, would be sent to rendezvous with the asteroid. Hovering a few kilometers away, each craft would unfurl a 20-meter-wide mirror made of a flexible material such as Mylar. The mirror would focus the sun’s rays onto the spacecraft’s solar panels, powering the laser. 

All eight lasers would then be simultaneously fired at a single spot on the asteroid’s surface, vaporising that region and creating a plume of gas that should provide enough thrust to push the asteroid off course. This relatively gentle nudging, over a period of months or years, would not break the asteroid up into any smaller pieces, the team say. 

Vasile, who will also be presenting his idea at the Granada conference, touts the flexibility and reliability of the approach. “You have a formation of satellites and if one breaks you have the others [for back-up],” he says. “And it’s scalable, so if you have a bigger asteroid or you want to have a faster deflection then you add more spacecraft.” 

Whichever option is ultimately chosen, reliability will be essential for a task as critical as asteroid deflection, says Bill Ailor of the Aerospace Corporation in El Segundo, California, who is chairing next month’s conference. “Launch vehicles fail at a rate of about 1 in 100, and new spacecraft might fail at the rate of 1 in 3, [which] has to be factored into the overall design of your deflection,” he says. “We’re in a sense betting the planet that we’re going to make this work.” 

There are at least two additional methods being suggested for deflecting threatening asteroids:

Gravity tractor
A “gravity tractor” could deflect an Earth-threatening asteroid if it were deployed when the asteroid was more than one orbit away from the potential impact, according to a new study. If the space rock was found heading straight for Earth, a combination of techniques — including a gravity tractor — may save the day (see 29 July 2008 HS Daily Wire). The study, carried out by NASA’s Jet Propulsion Laboratory in Pasadena, California, shows that the weak gravitational pull of a nearby spacecraft could deflect a hypothetical asteroid 140 meters across, big enough to cause regional devastation if it hit Earth. “Prior to this study, the gravity tractor deflection technique had been proven in only a conceptual way,” says Clark Chapman of the Southwest Research Institute in Boulder, Colorado, who was not involved in the study. “Although there were few, if any, substantive criticisms of these concepts, some of us had the feeling that the ideas were viewed as quaint but not-ready-for-prime-time,” he says. “The JPL study gives it the solid engineering underpinnings that we never really doubted, but now are there for anyone to see.” Exactly how much of a push is needed to deflect an asteroid depends on how long before a potential impact the intervention begins, and what kind of orbit the object is going to follow in the interval, says Rusty Schweickart, a former Apollo astronaut and chairman of the B612 Foundation, which funded the study.

Reflective sheeting
A Ph.D. student with the University of Queensland’s School of Engineering has won top prize in an international competition for her plan to wrap a giant asteroid with reflective sheeting to prevent a collision with the Earth. Her proposal was made specifically for Apophis — an asteroid estimated to be about 270 meters across which will pass close to Earth in 2029, well inside the orbit of the Moon — but it applies to other asteroids as well. 

Mary D’Souza put forward her proposal and took out the top prize in an international competition to find new ways of stopping asteroids from hitting our humble, little planet. With her paper, entitled “A Body Solar Sail Concept for the Deflection of 99942 Apophis,” D’Souza beat entries from around the world in the Space Generation Advisory Council’s Move An Asteroid 2008 competition. She later presented her ideas at the International Astronautical Congress, the world’s largest space conference, held in Glasgow at the end of September 2008. 

-read more in David Dearborn, Peter Schultz, and Wayne Ulrich, “New Directions in Asteroid Deflection using Nuclear Explosives”; and Christie Maddock et al., “Designs of Multi-Spacecraft Swarms for the Deflection of Apophis by Solar Sublimation”; see also “Asteroid Threat: A Call for Global Response” (Association of Space Explorers, 2008)