By Dr. Shane Ross

Getting from point A to B in space usually requires considerable quantities of propellant. But after it blasted off from Earth, the Genesis probe was able to travel 1.5 million kilometers. More.

Contrary to everyday experience on Earth, the most efficient route through space may not be a straight line. Some mathematicians and NASA engineers have learned in recent years that take best advantage of gravity, and save fuel in the process, it may be necessary to make bizarre loops through space.

Take for example the Genesis spacecraft. In 2004, it started on its way home after having spent two years collecting solar particles in orbit around a Lagrange point. a point between Earth and the Sun where the gravity of both bodies is balanced.

But Genesis did not come straight home. It took a long curvy path, going past the Earth to make an extended million-mile loop (around another Lagrange point) before coming back to Earth. Amazingly, this seeming impractical path actually saves fuel by making use of gravity in the Earth-Sun system.

The design of interplanetary space probes can now be done by taking advantage of the competing gravitational tugs of the different planets and their moons, which create a vast network of passageways by which a spacecraft can travel over large distances while expending very little energy. Without recent advances in mathematics and computation, these fuel-saving, mission-enabling paths through space could not be found.

Click the links to the right to learn more about the gravitational passageways which form this interplanetary transport network.

About the Author

Dr. Shane Ross; Assistant Professor of Engineering Science and Mechanics, Virginia Tech