Want to learn about something in space? Crash into it.

2022-11-17

NASA engineers devote lots of time and effort to make sure spacecraft are durable enough to survive the hazards of space. Sometimes, though, rockets or probes are designed to crash on purpose!

In 2022, there have been a number of notable space crashes, both planned and unplanned. While unexpected events can be dangerous, planned crashes can provide important information about our solar system—revealing features as diverse as a planet’s atmosphere or the chemicals in an asteroid’s surface. They pave the way for future space missions by testing new technologies, too. And crashing a machine into a space rock can even give data that could one day be used to protect Earth from a threatening asteroid.

The history of space exploration is rich with crashes—humanity’s early voyages to the moon relied on impacts to study the lunar surface in detail, like the Russian Luna 2 that became the first spacecraft to touch the surface of the moon in 1959, and the NASA Ranger program that returned the first close-up images of the moon in the 1960s. This decades-old tradition is carried on by modern missions, from Deep Impact smashing into a comet in 2005 to DART knocking around an asteroid in 2022. It’s very likely there will be more deliberate crashes in the future, too.

The NASA lander designed to crash

One of the riskiest parts of a mission to Mars is the landing. Many mechanical parts and software programs have to work properly to avoid such a situation—a computer glitch caused a European Mars lander to catastrophically crash in 2016. So far, NASA has dealt with this through a variety of technologies: giant bouncing airbags, parachutes designed to slow down the craft in the thin Martian atmosphere, and even their complicated sky crane system—essentially a jetpack that gently lowers a lander to the surface—that the Perseverance rover used.

As successful as these technologies are, they’re also expensive. Engineers at NASA’s Jet Propulsion Lab (JPL) are working on a new technique that may reduce costs—a device intended to crash, known as SHIELD. They call it an impact attenuator, something that’s made to absorb all the force of the crash and protect the sensitive electronics inside. It’s made of steel, with the shape of an upside-down wedding cake. When it hits the ground, it crumples, absorbing the shock of the impact just like the “crumple zone” of modern cars.

While the largest and most ambitious missions will always need traditional landing gear, they also take a long time to prepare. SHIELD’s tech allows for smaller, more frequent missions in addition to those. Lou Giersch, a mechanical engineer at JPL and leader of the SHIELD project, says this device could “increase the rate of scientific discovery” by making missions to Mars speedier and cheaper. “It’s sort of a complement to the more conventional Mars landing,” Giersch adds.

The team tested SHIELD at full Mars-landing speed–a whopping 110 miles per hour–for the first time in August 2022, strapping a smartphone to it. The smartphone survived and remained fully functional, even after hitting a two-inch-thick steel plate, which is much harder than actual Martian dirt.

NASA hopes this sort of tech will allow it to send more small missions to Mars, maybe even establishing a network of probes across the Red Planet. These could be like the local weather stations we use on Earth. One day, atmospheric scientists might tell you the local daily forecasts for Olympus Mons or Schiaparelli Crater. Being able to monitor the whole globe at once could reveal more about Mars’ dust, its atmosphere, and even marsquakes—and it all may happen after repeated successful crash landings.

A mysterious rocket on the moon

Astronomers puzzled over a surprise crash this year, when a piece of rocket debris smashed into the moon on March 4. NASA’s Lunar Reconnaissance Orbiter (LRO) later spotted a strange double crater created by the impact. Although some astronomers hoped this impact may be able to give them new information about the lunar surface, nothing much came of it besides a hunt for the wayward rocket’s culprit.

Astronomer Bill Gray first identified it as a SpaceX part, but later realized it was actually part of a 2014 Chinese test mission, called Chang’e 5-T1. Chinese officials deny this was their booster, though, so its origin remains somewhat of a mystery. The biggest takeaway here is how alarming it is that no one was sure exactly what this piece was, or where it came from—and that there are many other lost hunks of space debris just like it.

Although this crash was a loss for lunar scientists, there have been intentional impacts on the moon before—notably LCROSS, a mission to hit a permanently shadowed crater on the moon’s south pole in 2009. NASA astronomers sent one spacecraft to strike the surface, followed shortly after by a probe containing scientific instruments to measure the materials stirred up by the impact. This mission helped confirm a fact we now take for granted—the existence of water ice on the lunar surface.

University of Hawaii planetary scientist Chiara Ferrari-Wong notes that LCROSS data is still keeping scientists busy—the materials it revealed on the moon are strikingly different from those on Mercury, which is similarly cratered. “We are working to untangle what happened in each planet’s unique history that makes them similar yet different,” she says.

Knocking around asteroids

A clear highlight of this year in space crashes comes from DART, NASA’s Double Asteroid Redirection Test, a spacecraft that smacked an asteroid to nudge its orbit. This was the first test of planetary defense technology meant to protect Earth in the event we find an asteroid hurtling toward us.

“Thankfully, no known asteroid big enough to penetrate our atmosphere is a threat to impact Earth at any time in the next century,” says Angela Stickle, planetary scientist at Johns Hopkins Applied Physics Lab and DART team member. But if an as-yet undiscovered asteroid is on a collision course with Earth, she adds, “we want to be prepared.”

DART targeted an asteroid known as Dimorphos, which orbits another bigger asteroid called Didymos. By measuring the change in the time it takes for Dimorphos to orbit Didymos, before and after the impact, astronomers could determine how big of a punch their impacting spacecraft packed. The spacecraft changed the asteroid’s orbital period by 32 minutes, more than 25 times the goal time NASA set for a successful mission. “This was incredibly exciting and the team is still working on the details of why and how,” Stickle says.

This mission taught scientists about Didymos itself, which is actually a loose collection of rocks known as a rubble pile, showing how diverse the population of asteroids really is. For future asteroid diversions to be successful, astronomers need to know what each asteroid is made of, so they know how big of a push it needs.

This isn’t the first time scientists have hit an asteroid, though—the Japanese Hayabusa2 mission shot a small cannon into the asteroid Ryugu in 2019, blowing up the surface just enough to expose the lower layers of dirt and to fling debris toward the main spacecraft for sample collection. But that impact was on a much smaller scale than DART, and meant for a totally different purpose.

Now, Hayabusa2 is beginning a new mission, one that will contribute to DART’s goals of planetary protection. It’s hurtling toward a little-studied asteroid named 2001 CC21. They won’t collide; instead, the spacecraft is going to experiment with precision navigation around a fairly unknown target, a crucial skill for an asteroid-targeting planetary defense mission.

“My ideal next mission would be a spacecraft hitting an asteroid with one spacecraft watching the whole thing happen,” Stickle said about DART’s impact. “The more times we can test this technology, the better we will get.”

Popular Science, 17 November 2022
; https://popsci.com