A Heavy Gravity Tractor: Eight Years of Gravitational Towing for a 180-Metre Asteroid

This paper computes the performance of a gravity tractor of 40,000 kg hovering 40 m above the surface of a 180 m asteroid of mass 6,412,618,925 kg, so that its centre is 130.0 m from the body's centre. Mutual gravitation supplies a towing force of 1.01 N and an acceleration of 1.58e-10 m per second squared. Held for 8 years, that acceleration delivers 39.9 mm per second against a requirement of 18.5 mm per second for a 9,000 km displacement with eleven years of warning, a margin ratio of 2.15 and a computed separation of 19,381 km. This is a computed study of a deflection system for planetary defence, with no targeting or weapon application. It is simulated, not measured.