“A July 17 news release incorrectly stated that NASA’s
Genesis mission was the first to use gravitational pathways
through the solar system described as part of an
“Interplanetary Superhighway” concept. The following revised
news release corrects that statement and adds additional
historical background.”

A “freeway” through the solar system resembling a vast array
of virtual winding tunnels and conduits around the Sun and
planets, as envisioned by an engineer at NASA’s Jet
Propulsion Laboratory (JPL), Pasadena, Calif., can slash the
amount of fuel needed for future space missions.

Called the Interplanetary Superhighway, the system was
conceived by Martin Lo, whose software was used to help
design the flight path for NASA’s Genesis mission, which is
currently using this “freeway in space” on its mission to
collect solar wind particles for return to Earth.

Most missions are designed to take advantage of the way
gravity pulls on a spacecraft when it swings by a body such
as a planet or moon. Lo’s concept takes advantage of another
factor, the Sun’s pull on the planets or a planet’s pull on
its nearby moons. Forces from many directions nearly cancel
each other out, leaving paths through the gravity fields in
which spacecraft can travel.

Each planet and moon has five locations in space called
Lagrange points, where one body’s gravity balances another’s.
Spacecraft can orbit there while burning very little fuel. To
find the Interplanetary Superhighway, Lo mapped some possible
flight paths among the Lagrange points, varying the distance
the spacecraft would go and how fast or slow it would travel.
Like threads twisted together to form a rope, the possible
flight paths formed tubes in space. Lo plans to map out these
tubes for the whole solar system.

Lo’s research is based on theoretical work begun in the late
nineteenth century by the French mathematician Henri
Poincare. In 1978, NASA’s International Sun-Earth Explorer 3
was the first mission to use low energy orbits around a
Lagrange point. Later, using low energy paths between Earth
and the Moon, controllers at NASA’s Goddard Space Flight
Center, Greenbelt, Md., sent the spacecraft to the first
encounter with a comet, Comet Giacobini-Zinner, in 1985.

In 1991, another method of analyzing low energy orbits was
used by engineers from JPL and the Japanese Space Agency to
enable the Japanese Hiten mission to reach the Moon. Inspired
by this pioneering work and research conducted by scientists
at the University of Barcelona, Lo conceived the theory of
the Interplanetary Superhighway.

Lo and his colleagues have turned the underlying mathematics
of the Interplanetary Superhighway into a tool for mission
design called “LTool,” using models and algorithms developed
at Purdue University, West Lafayette, Ind. The new LTool was
used by JPL engineers to redesign the flight path for the
Genesis mission to adapt to a change in launch dates. Genesis
launched in August 2001.

The flight path was designed for the spacecraft to leave
Earth and travel to orbit the Lagrange point. After five
loops around this Lagrange point, the spacecraft will fall
out of orbit without any maneuvers and then pass by Earth to
a Lagrange point on the opposite side of the planet. Finally,
it will return to Earth’s upper atmosphere to drop off its
samples of solar wind in the Utah desert.

“Genesis wouldn’t need to use any fuel at all in a perfect
world,” Lo said. “But since we can’t control the many
variables that occur throughout the mission, we have to make
some corrections as Genesis completes its loops around a
Lagrange point of Earth. The savings on the fuel translates
into a better and cheaper mission.”

Lo added, “This concept does not guarantee easy access to
every part of the solar system. However, I can envision a
place where we might construct and service science platforms
around one of the Moon’s Lagrange points. Since Lagrange
points are landmarks for the Interplanetary Superhighway, we
might be able to shunt spacecraft to and from such
platforms.” A team at NASA’s Johnson Space Center, Houston,
working with the NASA Exploration Team, proposes to someday
use the Interplanetary Superhighway for future human space

“Lo’s work has led to breakthroughs in simplifying mission
concepts for human and robotic exploration beyond low-Earth
orbit,” said Doug Cooke, manager of Johnson’s Advanced
Development Office. “These simplifications result in fewer
space vehicles needed for a broad range of mission options.”

The work on the Interplanetary Superhighway for space mission
design was nominated for a Discover Innovation Award by
Discover magazine editors and an outside panel of experts.

JPL is managed for NASA by the California Institute of
Technology, Pasadena. For more information on the Genesis
mission, visit the Internet at: