July 3, 2022

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Why exposure to space dust is an inevitable aspect of space travel

Why exposure to space dust is an inevitable aspect of space travel

On June 8, NASA revealed that its powerful new space observatory, the James Webb Space Telescope, now has a small dome in one of its primary mirrors after it was pelted by larger-than-expected microscopic meteors in deep space. The news came as a bit of a shock because the impact occurred just five months into the space telescope’s tenure — but strikes like these are simply an inevitable aspect of space travel, and more attacks are sure to come.

Despite what its name suggests, the space isn’t completely empty. Within our solar system, tiny bits of space dust travel through the regions between our planets at gigantic speeds that can reach tens of thousands of miles per hour. These tiny meteorites, no larger than a grain of sand, are often small pieces of asteroids or comets that broke up and now orbit the sun. They are everywhere. A rough estimate of small meteorites in the inner solar system Their combined total mass is estimated at 55 trillion tons (If they were all combined into one rock, it would be about the size of a small island.)

This means that if you send a spacecraft into deep space, your instruments are sure to bump into one of these little bits of space rock at some point. Knowing this, spacecraft engineers will build their vehicles with certain protections to guard against micro-meteorite strikes. Often they incorporate something called Whipple shielding, which is a special, multi-layered barrier. If the shield is hit by a small meteor, the particle will pass through the first layer and fragment further, so the second layer will collide with smaller particles. This shielding is typically used around sensitive components of a spacecraft to provide additional protection.

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But with NASA’s James Webb Space Telescope, or JWST, it’s more complicated. Gold-coated telescope mirrors must be exposed to the space environment in order to properly collect light from the distant universe. And while these mirrors are built to withstand some impact, they’re somewhat of a sitting duck for larger micrometeoroid strikes, like the one that hit JWST in May. Although the micrometeorite was still smaller than a grain of sand, it was larger than NASA had expected — enough to damage one of the mirrors.

Spacecraft operators are modeling the assemblages of microscopic meteorites in space to get a better understanding of how often a spacecraft might be hit in any given part of the solar system — and what size particles might strike its instrument. But until then, it’s not a foolproof system. “It’s all a possibility,” says David Malaspina, an astrophysicist at the University of Colorado who focuses on the effects of cosmic dust on spacecraft. the edge. “You can just say, ‘I have a chance of hitting that size of a particle. “But whether you do it or not, it is due to chance.”

Examples of different types of Whipple shielding
Photo: NASA

Micrometeorites have a wide range of origin stories. They could be leftover products from high-speed collisions in space, which smash space rocks into tiny pieces. Asteroids and comets are also bombarded over time by space particles and photons from the Sun, causing tiny bits of shreds. The asteroid can also come close to a planet as large as Jupiter, where the strong gravitational pull stretches bits of rock. Or an object could get too close to the sun and get very hot, causing the rocks to expand and break into pieces. There are even microscopic interstellar meteorites just passing through our solar system from distant cosmic neighborhoods.

The speed at which these particles move depends on the region of space they are in and the path they take around our star, averaging about 45,000 miles per hour, or 20 kilometers per second. Whether or not it will hit your spacecraft also depends on where your spacecraft lives and how fast it is moving. For example, NASA’s Parker Solar Probe is the closest man-made object to the sun at the moment, moving at a top speed of more than 400,000 miles per hour. “It’s up to the 4-yard line, compared to Earth being all the way down at one end region,” says Malaspina, who has focused on studying the effects of micrometeorites on the Parker Solar Probe. It’s also moving through the densest part of a region called the zodiac cloud, which is a thick disk of space particles that permeates our solar system. So the Parker Solar Probe is under sand blasting more frequently than JWST – and it collides with these particles at incredibly high speeds than a telescope would.

The Parker Solar Probe gives us a better understanding of the micrometeoroids around the Sun, But we have a good understanding of the population around the Earth, too. When a small meteor hits the upper atmosphere around our planet, it burns up and creates meteor smoke – tiny, measurable smoke particles. The amount of this smoke can tell us how much dust is hitting the Earth over time. In addition, there were experiments on the International Space Station, where the material was installed on the outer surface of the orbiting laboratory to see how often it was bombed.

Art display of NASA’s Parker Solar Probe
Photo: NASA

While JWST lives about a million miles from Earth, it’s still relatively close. Scientists also have an idea of ​​what’s out there based on other missions that have been sent into an orbit similar to that of JWST. Most of the things that hit the telescope are not that important. “Spacecraft hit young children all the time,” Malaspina says. “By little, I mean fractions of a micron — much smaller than a human hair. And for the most part, spacecraft don’t even notice it.” In fact, JWST was already hit by four small meteors before it hit the larger micrometeorite in May.

NASA modeled the environment of micrometeorites before the JWST launch, but in light of the recent impact, the agency has put together a new team to improve their models and better predict what might happen to the telescope after future impacts. Modeling of current micrometeorites will attempt to predict things like how debris will spread through an orbit if an asteroid or comet crashes. This type of wreck is more dynamic, Malaspina says, which makes it more difficult to predict.

However, at the end of the day, prediction will simply give you more knowledge about it when A spacecraft could hit a large speck of dust. One-time effects like this are simply inevitable. The JWST eruption would continue over time, but this was a possibility that NASA had always prepared for. “You just have to live with the possibility that you will eventually bump into some dust-sized particles, and you do your best with engineering,” Malaspina says.