A Magnetic Tractor for an Iron-Rich Asteroid: Field-Gradient Coupling to a 95-Metre Metallic Body

This paper computes a magnetic tractor for an iron-rich 95 m asteroid of density 5,200 kg per cubic metre, iron fraction 68 percent and mass 2,334,386,601 kg. A superconducting coil on a spacecraft 85 m away produces a field of 0.018 T at the body, and the field gradient exerts 0.42 N, an acceleration of 1.8e-10 m per second squared, drawing 64 kW. Over 6.5 years the tractor delivers 36.9 mm per second against a requirement of 20.4 mm per second for a 9,000 km displacement with ten years of warning, a margin ratio of 1.81 and a computed separation of 16,305 km. This is a computed study of a deflection system for planetary defence, with no targeting or weapon application. It is simulated, not measured.