With a daring plan to collect rock and soil from the surface of Mars in the pipeline, NASA engineers are starting to move the necessary pieces into place here on Earth. The shielding that will protect these precious samples during the journey will play no small part in the mission’s success, and a round of high-speed projectile testing at a remote facility has edged it closer to lift off.
The Mars Sample Return mission is slated for launch later this decade but is already underway in a sense, with the Mars Perseverance rover at work collecting samples on the Red Planet’s surface. These samples will be stored safely in a container for later retrieval from another rover. This rover will palm the samples off to a rocket that will blast into Mars orbit and pass them to the Earth Return Orbiter spacecraft, which will bring them back to Earth sometime next decade.
Regarded as one of the most ambitious in the history of spaceflight, this daisy-chain of a mission has many moving parts, and many of those parts are still in the design phase. Among them is the Mars Earth Entry System, a disk-shaped vehicle that would safely carry the samples through the extreme environment of the Earth’s atmosphere.
NASA engineer Bruno Sarli is leading the development of the shields to protect the Mars Earth Entry System not just during this re-entry phase, but on its journey to the Red Planet and back aboard the Earth Return Orbiter. He explains that the program has very specific requirements when it comes to the issue of backward contamination, referring to the risk of hazardous biological materials being brought back to Earth.
“The Mars Sample Return program has unique Backward Planetary Protection requirements since it is the first NASA mission since the Apollo program that would be categorized as a “Restricted Earth Return” Category V,” Sarli told New Atlas.
This small category of Earth-return missions encompasses visits to bodies deemed to have significant risk of backward contamination, with the Jupiter moon Europa and Saturn moon Enceladus the others on the list. This class of mission calls for highly secure containment of the unsterilized samples, and for engineers like Sarli this means keeping them safe from rocks and dust in space.
“High reliability is the key engineering driver for the design of the Mars Earth Entry System in order to meet NASA’s stringent safety criteria, and fully contain the returned samples,” he explained. “The system would use a micrometeoroid shield to protect it from micrometeorites and space debris during the entire mission of the Earth Return Orbiter.”
Micrometeorites can travel at up to 50 miles (80 km) a second, meaning even tiny specks of dust can cause significant damage and potentially break apart the containment vessel. To simulate these impacts, Sarli and his team used computer modeling and two-stage gas guns at NASA’s Remote Hypervelocity Test Laboratory to fire small pellets at their shield materials at speeds as fast as can be achieved on Earth, at more than five miles (8 km) per second.
"At that speed, you could travel from San Francisco to New York in five minutes," said test conductor Dennis Garcia.
The team spent three days setting up the experiment, which lasted all of one second, and watched on from the bunker as pellets were fired into their experimental shielding materials at 25 times the speed of a .44 Magnum bullet. These projectiles travel through a highly pressurized gun barrel so long that it sticks out of the building, exiting into a small vacuum-sealed chamber to impact the target in an environment simulating space.
“One of the interesting things that we learned is that a massive piece of metal does not offer the same level of protection as really thin pieces of metal stacked together,” said Sarli. “What we’re doing is, we have very light layers of material, and those layers function by progressively breaking the particles, until the very last layer receives all the energy and stops them right there.”
The Earth Return Orbiter is scheduled to launch for Mars in 2027. You can hear from Sarli and see the high-velocity shield testing in the video below.
Source: NASA
