While NASA continues debating the final architecture for its planned Asteroid Redirect Mission (ARM), a couple of European researchers hope that theyve hit upon a means to drastically reduce the energies and velocities needed to overtake, grapple and gravitationally-capture such near-Earth objects.

If so, over-the-horizon asteroid capture missions not unlike ARM could someday be done on the cheap (or at least for less than their current projected billion dollar plus costs).

In a paper being published in the Journal of Guidance, Control and Dynamics, co-authors Patricia Verrier and Colin McInnes propose using a loophole in celestial mechanics that would allow for the artificial capture of an asteroid in an irregular, sticky orbit. That is, an orbit that wanders in a chaotic and ill-defined way. The idea is to use less energy by catching an asteroid in a chaotic sticky orbit rather than a regular and more well-defined and periodic orbit.

Capturing an asteroid around the Earth is usually done by reducing its energy to the point where it has less kinetic energy than needed to escape Earths gravity, Patricia Verrier, an astrodynamicist formerly at the University of Strathclyde in the U.K., told Forbes.

An artists concept of a NASA astronaut preparing to take samples from an asteroid that has been re-located into a stable Earth-Moon orbit. Credit: NASA

For a spacecraft to actually capture such an asteroid can require a high delta-v (or the amount of effort needed to change an objects orbit). This inherently presents quite a challenge for aerospace engineers actually designing capture mission spacecraft. But the authors found that the so-called irregular moon theory originally proposed by a separate group of researchers in 2003 to explain the chaos-assisted capture of our giant planets irregular moons could in theory also be used by mission engineers to aid in the capture of nearby asteroids.

The authors work, funded by the European Research Council (ERC), indicated that the energy that would be needed to capture an asteroid using their chaos-assisted method would be approximately only 10 percent of that needed for capture of an asteroid that is on an ordinary non-sticky orbit.

To demonstrate the concept, we looked at an asteroid trajectory that is not trapped around the Earth, but temporarily passes close to a regular region, said Verrier. We then calculated the point that requires the smallest energy change to apply an instantaneous impulse, or kick to move it into the regular region, so that its bound to Earth.

How different is this from previously proposed methods?

Other methods ensure that the asteroid is captured in such a way that it has less energy than it needs to escape again, so its permanently trapped, Colin McInnes, an astrodynamicist at the University of Glasgow in the U.K., told Forbes. With this method, in principle, the asteroid still has enough energy to escape, but cant since its orbit is sticky.

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Capturing Asteroids On The Cheap