Interplanetary Superhighway

For thousands of years, navigators have used the stars to find their way, but in recent years, GPS has all but eliminated the challenge of navigating the Earth’s surface. Today’s navigational problems are in space—and JPL research scientist Martin Lo has conceived an interesting and mathematically viable idea for navigating amongst the planets: an ‘Interplanetary Superhighway.’ Most missions take advantage of the way gravity speeds up a spacecraft as it swings by a planet or moon, but Lo’s idea takes advantage of something else—Lagrange points, which are the points between celestial objects where their gravitational pull is cancelled out. These points leave paths of ‘gravity voids’ through which spacecraft can travel without having to fight the pull of gravity, so just a tiny expenditure of energy would propel the craft, slashing the amount of fuel it needs to move. The Earth-Moon system has five Lagrange points, which connect to similar ones between other planets and moons, creating subtle pathways that link the solar system—imagine a network of virtual tubes, snaking through space like a freeway but constantly shifting as the planets orbit the sun. Even though travelling along these would be slower than more direct routes, and they do not guarantee easy access to every part of the solar system, this potential Interplanetary Superhighway requires minimal energy and therefore minimal fuel—a huge advantage for future unmanned deep-space missions.