How Do Gravity Assists for Spacecraft Work? | European Space Agency FriendsofNASA.org: Is there life on Terran V? Join the adventure to this fictional planet and find out what it takes to reach the farthest frontiers of deep space. This video uses a fictional spacecraft and star system to illustrate a gravity assist maneuver—also known as a planetary flyby or swingby. The gravity assist is one of the most important techniques in deep-space navigation. By carefully passing close to a planet, a sp