Celestial Superhighway: The Interplanetary Transport Network

Image via NASA

(Image in public domain)

The Interplanetary Transport Network (ITN) sounds like the stuff of science fiction writers like H.G. Wells or even George Lucas, but it is actually real, and has already been used.  Simply put, the ITN is a collection of pathways through the solar system, governed by gravity and predicted by chaos theory, that require little energy for an object to traverse them.  It has been likened to a celestial superhighway winding around the sun, planets and moons that could dramatically cut the amount of fuel needed by spacecraft to explore the solar system.

Image via NASA

(Image in public domain)

Douglas L. Smith, editor of Engineering and Science Magazine at Caltech, points out that the ITN is more akin to scenic routes like the Pacific Coast Highway than the interstates – not the fastest, most direct routes between Point A and Point B, but a more winding, leisurely path.  Dr Smith simplifies it by saying: “The quickest paths in outer space are all toll roads (it costs a lot of rocket fuel to use them), while you can ride the Interplanetary Superhighway almost for free. Gravity does the driving, so the system is really more like an elaborate set of Hot Wheels tracks. all you have to do is let go of the car at the right place.”

Image by NASA, retouched by Xander89

(Original in public domain.  Retouched image licensed under Creative Commons Attribution 3.0 Unported)

The ITN uses the gravitational pull between celestial bodies. In many cases, the competing forces cancel each other out, leaving positions called “Lagrange points“, essentially balancing points, where a small object can be stationary relative to two larger objects, such as the Earth and Moon.  A set of five Lagrange points (above), also called liberation points, exist between every pair of massive bodies.  They are peculiar in that they allow objects to orbit around them, despite the absence of any material object (like a planet) within.  They can then redirect trajectories through space (low energy transfers), creating corridors for ships to travel using little or no fuel.

Images by NASA

(Images (clockwise from top left) 1, 2, 3 in public domain)

In 1978 the International Sun/Earth Explorer 3 (ISEE-3) spacecraft became the first to orbit one of Earth’s Lagrange points (L1).  Taking advantage of the unique gravity environment, it proved that suspension between two gravitational fields was possible using little fuel.  Mission accomplished, it was then redirected through the geomagnetic tail of a comet and subsequently renamed the International Cometary Explorer (ICE).

Image via Canada-France-Hawaii Telescope Corporation

(Image licensed under Creative Commons Attribution-ShareAlike 2.5 Generic )

NASA’s recent Genesis mission also made use of a low energy transfer via the ITN.  Orbiting the Sun-Earth L1 point for over two years while collecting samples of the solar wind, the craft was redirected to the L2 Lagrange point before finally being sling-shot back to Earth.  SMART-1 of the European Space Agency was the most recent craft to use a low energy transfer, on this epic twisting journey along the Interplanetary Transport Network.  SMART-1 impacted the lunar surface as planned on September 3, 2006, bringing its mission to an end (above).

Image by Dcoetzee

(Image in public domain)

As we fast approach our one year anniversary, it’s fair to say that up until now, Urban Ghosts Media has been firmly entrenched within the Earth’s atmosphere.  And that’s how it will stay for the most part.  But now that we’ve broken through the boundaries of terrestrial existence, we too might find occasion to explore the final frontier!

For a better understanding of the Interplanetary Transport Network, read the full article by Douglas L. Smith of Caltech.

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