Saturday, 26 September 2009

Ticket To Ride (To Mars)

This Blog has followed space exploration with some interest, as it believes this planet has a very small window in which to establish outposts of humanity off planet before Earth civilisation collapses at the end of this century ...... so the news that Mars harbours vast amounts of water ice just under the surface is vastly encouraging.

Water-ice is seen to fade over time in this 12m crater within Arcadia Planitia  (Nasa/JPL-Caltech/University of Arizona)
Water-ice is seen to fade over time in this 12m crater within Arcadia Planitia

Now, if we can just crack the transportation propulsion method, then we have it sorted, cos a new road map has also been discovered.

This computer image shows gravitational 'corridors' which could help spacecraft ply the solar system like ships borne on ocean currents, and US scientists are trying to map the twisting tubes so they can be used to cut the cost of space travel. Each one acts like a gravitational Gulf Stream, created from the complex interplay of attractive forces between planets and moons.

Inter-planetary tube map
Inter-planetary tube map

The pathways connect sites called Lagrange points where gravitational forces balance out.

Professor Shane Ross, from Virginia Tech in the US, said: "Basically the idea is there are low energy pathways winding between planets and moons that would slash the amount of fuel needed to explore the solar system. These are freefall pathways in space around and between gravitational bodies. Instead of falling down, like you do on Earth, you fall along these tubes.
"Each of the tubes starts off narrow and small and as it gets further out it gets wider and might also split. I like to think of them as being similar to ocean currents, but they are gravitational currents. So if you're in a parking orbit round the Earth, and one of them intersects your trajectory, you just need enough fuel to change your velocity and now you're on a new trajectory that is free."

Riding one of the gravitational currents was unlike exploiting the "slingshot" effect of a planet or moon's gravity, a routine space travel technique, he explained. "Its not the same as a slingshot," said Prof Ross. "Slingshots don't put you in orbit round a moon, whereas this does."

Just one US mission so far has made use of the concept. The Genesis spacecraft was launched in 2004 to capture solar wind particles and return them to Earth. Following the gravitational pathways allowed the amount of fuel carried by the probe to be cut 10-fold.

The corridors were especially useful for voyaging between a planet's moons, said Prof Ross, speaking at the British Science Festival at the University of Surrey in Guildford. "Once you get to another planet that has its own tubes you can use them to explore its moons," he added. "You could travel between the moons of Jupiter essentially for free. All you need is a little bit of fuel to do course corrections."

However there is a catch, which is the length of time to make journeys, attempting to get a free tube ride from Earth to Mars would take thousands of years. ..... It would take a few months just to get round the Jovian moon system, so interplanetary travel would always require some fuel.

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