Pasadena, California – NASA has successfully landed on Mars nine times, relying on state-of-the-art parachutes, massive airbags and jetpacks to bring spacecraft safely to the surface. Now engineers are testing whether or not the easiest way to reach the Martian surface is to crash.
Rather than slowing a spacecraft’s high-speed descent, an experimental lander design called SHIELD (Simplified High Impact Energy Landing Device) would use an accordion-shaped collapsible base that acts as the crumple zone of a car and absorbs the energy of a hard impact. .
New design could drastically reduce the cost of landing on Mars by simplifying harrowing entry, descent and landing process and expanding options for possible landing sites.
“We think we could go to more dangerous areas, where we wouldn’t want to risk trying to land a billion dollar rover with our current landing systems,” said the SHIELD project manager, Lou Giersch of NASA’s Jet Propulsion Laboratory in Southern California. “Maybe we could even land several in different hard-to-reach places to build a network.”
Car crashes, Mars landings
Much of SHIELD’s design borrows from work done for NASA Mars sample return campaign. The first stage of this campaign involves the Perseverance rover take rock samples in sealed metal tubes; a future spacecraft will bring these samples back to Earth in a small capsule and crash-land safely in a deserted location.
Studying approaches to this process led engineers to wonder if the general idea was reversible, said Velibor ?ormarkovi?, a SHIELD team member at JPL.
“If you want to land something hard on Earth, why can’t you do the reverse for Mars?” he said. “And if we can make a hard landing on Mars, we know SHIELD could work on planets or moons with denser atmospheres.”
To test the theory, engineers had to prove that SHIELD could protect sensitive electronics during landing. The team used a drop tower at JPL to test the strength of Perseverance’s sample tubes during a hard landing on Earth. Standing nearly 90 feet (27 meters) tall, it features a giant sling – called an arc launch system – that can launch an object to the surface at the same speeds achieved when landing on Mars.
?ormarkovi? previously worked for the automotive industry, testing cars fitted with crash dummies. In some of these tests, the cars run on sleds that are accelerated to high speeds and crashed into a deformable wall or barrier. There are several ways to accelerate sleds, including using a sling similar to the bow launch system.
“The tests we did for SHIELD are kind of like a vertical version of the sled tests,” ?ormarkovi? said. “But instead of a wall, the sudden stop is due to an impact in the ground.”
On August 12, the team gathered at the drop tower with a full-size prototype of SHIELD’s collapsible attenuator – an inverted pyramid of shock-absorbing metal rings. They hung the attenuator from a grappling hook and inserted a smart phone, radio and accelerometer to simulate the electronics a spacecraft would carry.
Sweating in the summer heat, they watched as SHIELD slowly climbed to the top of the tower.
“Hearing the countdown gave me goosebumps,” Nathan Barba, another member of Project SHIELD told JPL. “The whole team was excited to see if the objects inside the prototype would survive the impact.”
In just two seconds, the wait was over: the bow launcher slammed SHIELD into the ground at around 110 miles per hour (177 kilometers per hour). It is the speed a Mars lander reaches near the surface after being slowed by atmospheric drag from its initial speed of 14,500 miles per hour (23,335 kilometers per hour) when it enters the atmosphere Of March.
Previous SHIELD tests used a dirt “landing zone”, but for this test the team laid a 2-inch (5 centimeter) thick steel plate on the ground to create a harder landing than a spacecraft on Mars. The onboard accelerometer later revealed that SHIELD had been hit with a force of approximately 1 million newtons – comparable to 112 tons crashing into it.
High-speed camera footage from the test shows SHIELD impacted at a slight angle, then bounced about 3.5 feet (1 meter) in the air before flipping over. The team suspects that the steel plate caused the kickback, as no kickback occurred in previous tests.
After opening the prototype and retrieving the simulated electronic payload, the team discovered that the onboard devices – even the smart phone – had survived.
“The only hardware that was damaged was plastic components that we weren’t worried about,” Giersch said. “Overall, this test was a success!”
The next step? Designing the rest of a lander in 2023 and seeing how far their concept can go.