Today, we received the final report from the B612-funded JPL study evaluating the feasibility of the Gravity Tractor asteroid deflection method.

The Gravity Tractor concept, developed by B612 Co-founder and former astronaut Dr. Ed Lu and fellow astronaut Dr. Stanley G. Love, proposes using the gravitational pull of a spacecraft stationed near an asteroid to gradually alter its trajectory. To assess this approach, B612 supported a detailed design study at NASA’s Jet Propulsion Laboratory (JPL), culminating in the Near-Earth Object (NEO) Transponder Tracking and Gravity Tractor Performance report.

Led by JPL researchers, the study analyzed how a Gravity Tractor spacecraft could be deployed in a real-world asteroid deflection scenario. The team examined a hypothetical Earth-impacting asteroid, 2016 NM4, projected to strike in 2049. The study simulated an initial kinetic impactor deflection in 2028 and explored how a Gravity Tractor could fine-tune the asteroid’s trajectory to prevent it from passing through a gravitational “keyhole”—a narrow region in space that could lead to a secondary Earth impact in 2054.

Key Findings

• A Gravity Tractor can effectively maintain position near an asteroid and apply controlled gravitational force to adjust its orbit.
• A 1000 kg spacecraft hovering 155 meters from the asteroid could impart a velocity change of 7 microns per second per month, sufficient to steer it clear of a hazardous keyhole.
• The fuel consumption required for this process is minimal (~1.4 kg per month), suggesting that a chemical propulsion system may be a viable alternative to more complex solar electric propulsion.
• Using an onboard transponder, the spacecraft can provide highly accurate asteroid trajectory updates, improving impact predictions by a factor of 2–5 over Earth-based observations.
• The Gravity Tractor is particularly effective as a secondary maneuver, ensuring that an asteroid deflected by other means does not inadvertently enter a trajectory leading to a delayed Earth impact.

The results of this study provide strong technical validation for the Gravity Tractor as a tool in planetary defense. While techniques like kinetic impactors or nuclear deflection may serve as primary deflection methods, a Gravity Tractor offers a precise and controllable means of adjusting an asteroid’s trajectory post-deflection.

Download the full report | Near-Earth Object (NEO) Analysis of Transponder Tracking and Gravity Tractor Performance, JPL Task Plan No. 82-120022 (2008)

Read the original Gravity Tractor proposal | “A Gravitational Tractor for Towing Asteroids,” Dr. Ed Lu & Dr. Stan Love, Nature (2005)

B612 continues to advocate for mission studies and technology development to prepare for future asteroid threats. This JPL study confirms that Gravity Tractors are not just a theoretical possibility—they are a feasible, effective tool for protecting Earth from future impacts. Consider making a donation today to support this important work.