^.5 Asteroid Capture and Mining * It has been proposed by Brian O'Leary that Amor and Apollo asteroids could be captured and placed into earth orbit to provide a source of raw materials for various space activities. Typical characteristics of Amor and Apollo asteroids are shown in Table 4.2. The estimated population of these asteroids greater than 100 m in diameter is about 150,000. They are presently being discovered at the rate of 2 to 3 per year. The Apollo and Amor asteroids appear to be typical of ordinary and carbonaceous chondrites and contain a number of free metals including nickle, iron, gold, silver, platinum and so on. They are located in orbits close to that of the earth and require only about 3 km/s velocity increment for capture. O'Leary proposes the use of a mass driver that is capable of using asteroidial material to provide the necessary impulse for asteroid capture. This mode of capture would consume a significant fraction of the asteroid. Another mode, that examined here, proposes the use of argon propellant at 10,000 s specific impulse and the use of the SPS satellite as a power supply to effect asteroid capture. Taking a AV of 3 km/s each way and a 100 m diameter asteroid, 1.25 million MT, the propellant requirements are 2,300 MT outbound and 39,100 MT inbound for a total of 41,400 MT. Using this trajectory mode, a thrust duration of somewhat in excess of one year is required to impart the AV with the asteroid in tow. The economics of asteroid recovery depend strongly on the materials contained in the asteroid and the demand for these materials in space. Typical values of iron and nickle contained in a 100 m diameter asteroid are as follows: A 10 percent yield of iron would provide 0.125 million MT with a gross value, at $210 ♦ O'Leary, Brian, Mass Driver Retrieval of Earth-Approaching Asteroids, presented at the Third Princeton/AIAA Conference on Space Manufacturing Facilities, Princeton, NJ, May 9-12, 1977.
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