Gravity-Assist Mechanical Simulator for Outreach

NASA’s Jet Propulsion Laboratory, Pasadena, California

There is no convenient way to demonstrate mechanically, as an outreach (or inreach) topic, the angular momentum trade-offs and the conservation of angular momentum associated with gravityassist interplanetary trajectories. The mechanical concepts that underlie gravity assist are often misunderstood or confused, possibly because there is no mechanical analog to it in everyday experience. The Gravity Assist Mechanical Simulator is a hands-on solution to this longstanding technical communications challenge. Users intuitively grasp the concepts, meeting specific educational objectives.

Figure 1. **Gravity Assist Mechanical Simulator:** Yellow outlines the glass surface that represents the ecliptic plane.

A manually spun wheel with high angular mass and low-friction bearings supplies momentum to an attached spherical neodymium magnet that represents a planet orbiting the Sun. A steel bearing ball following a trajectory across a glass plate above the wheel and magnet undergoes an elastic collision with the revolving magnet, illustrating the gravitational elastic collision between spacecraft and planet on a gravity-assist interplanetary trajectory.

Figure 2. ***Major Components;*** *support structure and launcher not shown.*

Manually supplying the angular momentum for the elastic collision, rather than observing an animation, intuitively conveys the concepts, meeting nine specific educational objectives. Many NASA and JPL interplanetary missions are enabled by the gravity-assist technique.

This work was done by David F. Doody and Victor E. White of Caltech, and Mitch D. Scaff for Art Center College of Design and donated to NASA’s Jet Propulsion Lab oratory. For more information, contact iaoffice@jpl. nasa.gov. NPO-48001