Today, former B612 co-founder Dr. Ed Lu and fellow former NASA astronaut Dr. Stanley Love published a proposal for the Gravity Tractor method for altering an asteroid’s trajectory in Nature Vol. 438. Their method describes how a spacecraft could use its own gravitational pull to gradually change an asteroid’s path.

Unlike deflection techniques that require physical contact, such as kinetic impactors or surface-mounted thrusters, the Gravity Tractor operates by hovering near an asteroid. The spacecraft’s thrusters are angled outward to prevent surface disturbance, allowing its mass to exert a small gravitational force that slowly shifts the asteroid’s trajectory over time.

This approach does not depend on an asteroid’s surface properties, internal structure, or rotation—factors that complicate direct-contact deflection strategies. With sufficient lead time, typically decades, even small adjustments can result in significant trajectory changes.
One potential application is asteroid 99942 Apophis, a 320-meter-wide object that will pass near Earth in 2029. If later observations confirm a risk of impact in the 2030s, a Gravity Tractor could provide the necessary velocity change to prevent a collision. The required force for such a deflection would be within the capabilities of proposed space propulsion systems.

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