A Captured Asteroid: our David's Stone for Shielding Earth and Providing the Cheapest Extraterrestrial Material
- Paper ID
2189
- author
- company
Centre National d'Etudes Spatiales (CNES)
- country
France
- year
2005
- abstract
The issue of protecting the Earth against an asteroid impact is very popular and many concepts have been proposed to fulfill this objective. In this paper we develop the idea of capturing a small size asteroid from an orbit close to Earth’s in terms of energy and placing it into a loose earth-bound orbit in order to use it as a source of material such as liquid oxygen for exploratory missions. In case our planet is threatened by an asteroid impact, we could also use this captured asteroid as a shield by engineering its collision with the incoming body prior to the impact with the Earth. We show that the production of a material such as liquid oxygen is much more efficient from an asteroid’s surface than from the Moon’s. As the celestial surface most accessible from Earth, an captured asteroid is also easier to engineer. Several thousands of tons of oxygen might become available sitting on the outer rim of Earth’s gravity field. The operations for turning the captured asteroid into a efficient shield appear to be quicker, easier, cheaper and safer than an mission aimed at landing on an incoming impact-bound asteroid either for altering its trajectory or attempting to destroy it. The aim is an asteroid typically 20 meter in diameter, too small to cause damage on Earth if an improper management leads to its crash, but big enough to destroy and deviate any incoming body if a collision is engineered with it at 3 or 4 million km from Earth. Such a collision could be implemented within a 6 month time frame. We examine the advantages and drawbacks of this concept and we propose a stepped approach for making it a reality within a foreseable future. Key factors are first the detection of a candidate, whose small size make it difficult to spot, among a population of asteroids easy to reach from the Earth. The second keypoint is how to deviate the candidate into an loose Earth bound orbit. Our preferred concept is to deposit a small robotic instrument aimed at throwing up matter gathered on the surface of the body with typical velocities of tens of meters per second. The robot would require a year and a few tens of watts to alter the velocity of the asteroid by typically a few meters per second in order to inject it through an Earth-Sun Lagrange point, and then to control a non conventional orbit around the Earth with a typical one year period. We conclude that such an enterprise is far from being unfeasible and that it can probably be conducted using today’s systems and exploratory tools in a few years time frame.