In the wake of last month's meteorite explosion in Russia's Chelyabinsk, it has become increasingly clear that, if humanity is not to follow the dinosaurs into oblivion, it has to find a way to deflect killer-asteroids from hitting the Earth. As international space agencies continue their quest to find for the most effective threat-reduction methods, the Voice of Russia reviews the more unusual asteroid deflection techniques currently proposed by modern science.

Traditional thought suggests there are three possible means by which a threat from an Asteroid is most likely to be diverted: gravity tractors, kinetic impactors, and the nuclear blast-deflection method. The gravity tractor technique involves sending a probe to the asteroid without actually touching it. The probe would then remain alongside the celestial body and using its additional, albeit small, gravitational field, gradually drag the asteroid off course.

This technique offers the possibility of a very precise change in the asteroid's trajectory. Indeed, NASA's Dawn spacecraft is currently using exactly this method to pull the huge space-rock, Vesta, off course. The one downside to this method though is that it would take months, or even years, for a meaningful change in the asteroid's course.

This raises two problems: firstly, if the potentially fatal asteroid is detected too late, humanity might not have the luxury of time to use such a 'slow' prevention method. Secondly; to reliably and continuously operate alongside a giant space rock for several years the 'tractor' would need an incredibly powerful propulsion system, potentially ion thrusters, that has yet to be developed.

The kinetic impactor technique may address those difficulties by relying on brute force rather than a gentle gravitational tug. This method involves simply 'ramming' the threatening space object with a robotic probe to adjust its course away from Earth. While the impactor technique would not be as precise as the gravity tractor approach, it would still 'do the job'.

The European Space Agency (ESA) developed a mission concept of this type as early as 2005. Named the 'Don Quixote', the ESA proposed to deflect the infamous Apophis asteroid with two separate probes: one would slam into the asteroid at more than 48 000 kilometres per hour, while the other would remain in orbit to assess the kinetic impact's effect.

An even more aggressive deflection method would be to detonate a nuclear weapon on or near the surface of the offending asteroid. This technique could be particularly useful if the time between detection and projected impact were too short for the other methods to be relied upon. Despite being probably the simplest, and most popular, solution to the problem of deadly asteroids approaching Earth, the nuclear detonation method also has its problems.

It is still unclear how some asteroids might respond to a nuclear detonation, and what would happen if the explosion failed to deflect the object completely. Then of course, the use of nuclear devices in space could be a particularly sensitive topic both legally and politically because of current multilateral agreements prohibiting nuclear weapons testing in space.

Having reviewed these traditional asteroid deflection techniques, Sung Wook Paek, a graduate from the Massachusetts Institute of Technology, suggests an unusual alternative: Mr Paek proposes using paintballs to pull an asteroid off course.

The argument behind Mr Paek's idea is reasonably simple; after measuring the velocity and rotation of an incoming asteroid, two unmanned spacecraft would approach the celestial body close enough to be able to shoot large clouds of white paintballs at it! Two probes would be needed because, as the asteroid rotates, a shot from only one spacecraft would not cover the entire asteroid with white paint and so the first probe strikes one side of the asteroid, the second probe covers the other.

The white paint would reflect light and other electromagnetic radiation from the asteroid's surface, and, over time, the cumulative effect of billions of photons would result in the asteroid changing course. The white paint would effectively act as a 'solar sail', increasing the balance of solar radiation absorbed and emitted by the asteroid, gently easing it away from its original destination.

Another deflection technique, also based on light reflectivity or laser sublimation was proposed by a team of American researchers who suggested launching a swarm of 'mirror bees' towards the potential killer.

Tiny probes, equipped with mirrors, would position themselves in such a way as to reflect a concentration of sunlight on one specific point of the asteroid. This 'beam of light' would then generate enough heat for it to start to vaporise, creating propulsive gas jets. In essence, vapour emitted from the asteroid would push it off-course. Alternatively, the asteroid might 'simply' be wrapped in reflective 'foil'.

These of course are just a select few of the many deflection methods and strategies that are currently being developed and investigated by scientists from all over the world. It is vital that such research continues so that, if the worst should come, humanity will be equipped with a viable 'toolbox' of deflection techniques and live to tell the tale of the potentially deadly asteroid, that didn't, quite, hit Earth!

Source: Voice of Russia