Asteroid Deflection

SSI funded studies of asteroid detection, asteroid tracking, and mining of asteroids. We also studied the concept of assembling a mass driver engine in orbit, sending it to an Earth-approaching asteroid, and then using the mass driver to modify the asteroid’s orbit. This research was conducted with the goal of guiding the asteroid into a High Earth Orbit where it could be mined for its minerals. But such a technological capability, once developed, has obvious applications should we ever need to divert an asteroid from an Earth-intercepting course.

For a long while, the conventional wisdom on this issue was that one would use nuclear explosives for this purpose. But according to a paper published in the June 4th, 1998 issue of Nature, this may not be as easy as previously thought. It points out that many asteroids are multi-lobed. A nuclear detonation might be largely absorbed by one lobe, with little course deflection resulting in the whole. The paper theorizes that the average asteroid may not be so much like a solid rock as an aggregate of fragments loosely held together by fine dust. If this “flying gravel pile” theory is correct, a nuclear detonation might pulverize an approaching asteroid, converting one big problem into many little ones.

A mass driver engine, by contrast, could provide the low, steady, continuous thrust needed to change an asteroid’s course gradually, using the asteroid’s own material for reaction mass.

The ability to modify an asteroid’s course via mass driver certainly promises to usher in a new era where space resources are freely available for construction projects in High Earth Orbit, and holds out promise for obtaining resources in a way which is not damaging to the environment of Earth. But it is just barely conceivable that this same technology might also help to avert a catastrophe of major proportions.

In any event, a major program of asteroid mining can only make the Earth safer as the centuries pass. As it happens, those asteroids which cross the orbit of the Earth (and thus pose the greatest hazard) are also the ones most economically attractive for space-resource use.

It is good that humanity is becoming more aware of the threat posed by Earth-crossing asteroids. But at the same time we should also become more aware of their vast economic potential.

Technology for Human Space Settlement