November 18, 2010

Scientists Envision Martian Vehicles Propelled By CO2

Researchers say that nuclear decay-driven machines could gather gases from the atmosphere of Mars for propulsion.

A new design concept outlines an approach to compress CO2 and liquefy it.

The liquid would be heated similar to a standard rocket by expanding violently into gas to propel the machines to great distances.

The authors suggest this is a better strategy to see more of Mars.

Vehicles that are powered by the sun and get around on wheels are limited in their overall range of exploration.

The Opportunity rover, which has been on the Martian surface for nearly seven years, passed the 15-mile mark this week.

Researchers have been looking into means of getting farther with future robotic missions to Mars.  Ideas like landers with wings or lighter-than-atmosphere balloons have been proposed, or even "inflatable tumbleweeds" that are blown across the landscape.

However, according to a recent BBC News report, Hugo Williams and his colleagues at the University of Leicester argue that a lander that can gather up its own fuel is best.  They are currently working on propulsion ideas for a lander project including aerospace giant Astrium.

At the heart of the idea is a radioisotope-based generator, which is a piece of radioactive material that heats up as it regularly spits out tiny subatomic particles.

"Nuclear batteries" employing the same principle have been in use in long-term space missions since the Pioneer craft of the early 1970s.

In the proposed hopper design, heat from the decay is collected and used to run a compressor.

Some of the heat is channeled into another block of material that is used as a storage heater.  When the hopper needs a boost, liquid is allowed to contact the block, quickly turning back into a gas and heating up.

The expanding CO2 gas provides thrust that can launch a lander and provide a soft landing when it "hops" to its new location.

"The advantage is that the radioisotope source is long-lived and not dependent on solar energy," Williams explained to BBC News.

"You can operate for a long time, and in areas of Mars where the amount of sunlight is relatively small. Because you're collecting your propellant from the Martian atmosphere you're not limited by having to take propellant out from Earth."

The idea would require a week to gather sufficient propellant for a hop of a little over a half a mile.


Image Caption: This mosaic of images from the navigation camera on NASA's Mars Exploration Rover Opportunity shows a 90-degree view centered toward the east following a 93.3-meter (306-foot) drive east-northeastward during the 2,382nd Martian day, or sol, of Opportunity's mission on Mars (Oct. 6, 2010). Image Credit: NASA/JPL-Caltech


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