NASA fires micro-bullets at Mars sample-return orbiter's meteoroid shield

NASA engineers are firing micro-bullets at squares of anti-meteoroid shield material that will protect a Mars sample return orbiter during its journey back to Earth. 

During the tests, which take place at NASA's remote White Sands Test Facility near Las Cruces, New Mexico, the shield has to withstand projectile punches coming at such high speeds that if an aircraft traveled as fast, it would get from New York to San Francisco in less than 5 minutes, Dennis Garcia, a test engineer at White Sands said in a statement. 

These speeds, however, are still not as fast as those of meteoroids and space junk fragments that orbit in space, so the engineers have to use computer models to simulate the actual velocities, which can reach over 50 miles per second (80 kilometers per second). At such speeds, "even dust could cause damage to a spacecraft," Bruno Sarli, an engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who oversees the tests, said in the statement. 

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The Remote Hypervelocity Test Laboratory, where the tests take place, has been serving NASA since the space shuttle era, enabling engineers to develop materials that protect the International Space Station, commercial crew vehicles and space cargo freighters against impacts by debris and rock fragments in space. 

The gun used to fire the space-like micro-bullets at the shield material has two stages, the first of which uses conventional gun powder to propel a projectile. The second stage gives the projectile an extra boost by pushing highly compressed hydrogen gas into a smaller tube like a car piston. The pressure in the gun, the researchers said in the statement, is so high that it would destroy the building if it were to explode.  

The engineers found that, instead of relying on one thick block of metal to ward off the projectiles, the shield offers better protection when it's made of multiple thin layers, Sarli said. 

The Mars Sample Return Orbiter to be built jointly by NASA and the European Space Agency (ESA) will bring to Earth precious samples of Martian rocks that NASA's Perseverance rover is currently collecting on the planet's surface. The operation will be the first of its kind and will for the first time allow scientists to hold in their hands rocks freshly extracted from another planet. Martian meteorites sometimes fall to Earth, but these rocks have spent millions or billions of years in space and have been altered by its harsh environment and radiation. Mars meteorites are also contaminated by Earth life when they fall on our planet, making it tough to search them for signs of Red Planet organisms.

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