Using Small Asteroids to Deflect Larger Dangerous Asteroids

The basic concept involves targeting a very small asteroid, about 10 meters across, to impact a larger dangerous one. The minimum size of the small asteroid is determined by the ability to detect it and to determine its orbit. Near-Earth asteroids (NEA’s) are selected from those that have a fly-by distance from Earth of the order of hundreds of thousands of kilometers. According to current estimates, the number of near Earth asteroids with such sizes is very large, making it possible to find the required small asteroid. Further, the possibility is evaluated of changing the small asteroid’s orbit so that, by application of a very limited ΔV impulse, the object is targeted to a gravity assist maneuver (Earth swingby) that puts it on a collision course with a dangerous asteroid. In order to apply the required V impulse, it is necessary to install on the small asteroid an appropriate propulsion system with required propellant mass. A control system similar to that used on a spacecraft is also necessary. The Keck study has already shown the feasibility of performing the above steps to change the orbit of similar asteroids to target them to a lunar orbit; our idea is similar in orbital energetics to that, only for slightly larger objects and targeting them to an Earth B-plane point rather than the vicinity of the Moon. Of course, any real test of this (or of any other deflection) strategy should first be performed on a benign asteroid whose orbital parameters give the asteroid no significant chance of a natural impact with the Earth during at least the next million years, even in the case of small changes in its orbit.