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article imageRosetta: Next step, hitching rides on comets across the cosmos?

By Stephen Morgan     Nov 13, 2014 in Science
No, its not a new sequel to the Hitchhiker's Guide to the Galaxy, its a serious possibility and the successful landing of the Philae probe could be a first step towards it. In fact, NASA has already funded research to look into its feasibility.
Some scientists are suggesting that the future of space travel, at least in our own Solar System, may be hitching a ride on a comet or an asteroid. The aim would be to reduce flight time, enable manned missions, save fuel and money, and most importantly protect astronauts against harmful radiation.
Eight years ago, an engineering physics undergrad from the University of Arizona, Daniella Della-Giustina, received NASA's Advanced Concepts Student Fellows Prize for her project entitled "The Martian Bus Schedule: An Innovative Technique for Protecting Humans on a Journey to Mars."
At the time, ran an article about this entitled “Harnessing Asteroids and Comets to Travel the Solar System.” It explained that Daniella's NASA sponsored research would investigate two possibilities for using asteroids. “The first” it says, “would involve spacecraft actually hitching a ride on asteroids that cross the orbits of both Earth and Mars” and the other would be to simply use them as a sort of "radiation parasol”, whereby the spacecraft just travelled alongside in their shadow.
National Geographic also ran an article in 2011 entitled “Astronauts Could Ride Asteroids to Mars, Study Says” and explained the problems and possible solutions in more detail.
The problem, it said was that Mars astronauts would be exposed to a prolonged period of dangerous radiation and that 18 months in space would cause cataracts, affect DNA and increase the chance of them getting cancer by up to 20%.
The thin aluminium shields, which spaceships currently have would be useless on such a long journey and could even cause secondary cancer. Furthermore, the current radiation shields on Earth are just too heavy and, in any case, would also be ineffective.
In its article, it refers to a paper, written by Gregory Matloff, a professor of physics at the New York City College of Technology, who believes he has found the solution.
Matloff says that an asteroid could block this radiation, if a spaceship parked in one of its craters, allowing astronauts to get to Mars unharmed. The asteroid itself would act much as the Earth shields astronauts in the orbiting space stations today.
In his paper published in the journal Acta Astronautica, Matloff argues that time and money would be better spent on redesigning a spacecraft to hop onto comets rather than trying to engineer a new kind of shield.
Matloff has calculated that an asteroid "taxi" would only have to be about 33 feet (10 meters) wide to be effective. However, the orbit of the comet or asteroid would need to pass within a few million miles of both Earth and Mars to make hopping aboard feasible.
So far, the earliest known Mars “asteroid taxi” arrives in 2037 and there are four others which will pass by us before the end of the century. The good news is they could make it to Mars within one year. But, the fly in the ointment is that it might be a one-way ticket.
Astronauts would have to wait until the asteroids turned round in its orbit and flew back towards Earth and that could be 5 years later. Still, the data base of these space rocks is increasing all the time and there are now some 7,000 contenders to sift through, some of which might have a better “timetable.”
But it has been suggested that the way to get round this would be to give the asteroid a bump before landing on it. The aim would be to change its course so that it cycles Earth and Mars in an orbit which would be a suitable time span for the return journey. Matloff suggests this could be done with a solar sail or gentle propulsion. Then you just hop on it, he says.
Would this stop at Mars missions? Who knows? Halley’s comet, for example, travels to the edge of our solar system. Therefore, in theory, we could jump off along the way to explore other planets and their moons.
NASA's experts working on the Space Radiation Shielding Project say Matloff's idea would work in theory, although they are looking at other ways to get around the radiation problem.
More about rosetta mission, Comets, Asteroids, hitching
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