You've heard of space explorers exploiting gravity to save fuel, but using a new method, spacecrafts could, with a little push, roll through the solar system mostly unaided. It's like rolling downhill all the way to work to save gas.
The central concept is that of Lagrangian Points, or L-points. An L-point is a place in space where the gravitational fields of the surrounding bodies all cancel out to create a point of apparent zero gravity. This concept has been exploited before; the Solar and Heliospheric Observatory is stationed at one such point, where the close-by Earth's gravity cancels the distant Sun's gravity. It sort of just sits there, in this gravitational rut.
And that's basically what these gravity corridors are: they are pathways in space where the gravity is lowest and, in most cases, where the gravity is getting lower. If the gravity of the surrounding planets can be seen as big hills, the gravitational corridors are the sloping valleys between these hills. If scientists can find the valleys that slope in the direction they want to go, they won't need much fuel at all to just roll down those valleys.
Scientists in America and Germany are working to develop a map of these corridors for future space flights. They envision a time when very little fuel would be needed to easily drift from one of Saturn's moons to the other using the gravity of these floating rocks.
As a result, fuel use could be cut by a factor of ten on space journeys, allowing for lighter and cheaper spacecrafts. Of course, drifting lazily through the gravity streams between distant space objects, as relaxing as it sounds, would also take a lot longer. Let's get working on those cryogenics!
Interplanetary Superhighway animation (by Cici Koenig)
Gravitational Space Corridors Could Slash Space Travel Costs [PhysOrg]
(Image and Video from Dr. Shane D. Ross)