Why space dust is an inevitable aspect of space travel

On June 8, NASA revealed that its new powerful space observatory, the James Webb Space Telescope, now has a small dimple in one of its main mirrors after being dropped by a larger-than-expected micrometeroid into deep space. The news was a little shocking, as the impact came just five months after the telescope was used in space – but such strikes are simply an inevitable aspect of space travel, and there are certainly more to come.

However, as its name suggests, the space is not entirely empty. Within our solar system, small chunks of cosmic dust move through the regions between our planets at enormous speeds that can reach tens of thousands of miles per hour. These micrometeoroids, no larger than a grain of sand, are often small pieces of asteroids or comets that have broken away and are now orbiting the Sun. And they are everywhere. Rough estimate of small meteoroids in the inner solar system determines their total mass of about 55 trillion tons (If they were all combined into one rock, it would be the size of a small island).

This means that if you send a spaceship into deep space, your hardware will certainly be hit by one of these small pieces of space rock at some point. Knowing this, spacecraft engineers will design their vehicles with certain protections to protect against micrometeoroids. These often include something called Whipple shielding, a special multi-layer barrier. If the shield is hit by a micrometeoroid, the particle will pass through the first layer and fragment even more, so that the second layer will be hit by even smaller particles. Such shielding is typically used around sensitive spacecraft components for added protection.

But with NASA’s or JWST’s James Webb Space Telescope, it’s more complicated. The golden mirrors of the telescope must be exposed to the cosmic environment in order to properly collect light from the distant universe. And while these mirrors are designed to withstand certain shocks, they are more or less seated ducks for larger micrometeorological shocks, such as the one that hit JWST in May. Although the micrometeoroid was still smaller than a grain of sand, it was larger than NASA expected – enough to damage one of the mirrors.

Spacecraft operators are modeling the population of micrometeroids in space to gain a better understanding of how often a spacecraft can hit a part of the solar system – and how large the particles can hit their hardware. But even then, this is not a reliable system. “It’s all probability,” said David Malaspina, an astrophysicist at the University of Colorado who focuses on the impact of space dust on spacecraft. On the edge. “You can just say, ‘I have this chance of being hit by a particle of this size.’ But whether you ever do it or not depends on chance. ”

Examples of different types of Whipple shielding
Image: NASA

Micrometeoroids have a wide range of origin stories. They can be the remnants of high-velocity collisions in space that shatter space rocks into small pieces. Asteroids and comets are also bombarded over time by cosmic particles and photons from the Sun, causing small pieces to break off. The asteroid may also get too close to a large planet like Jupiter, where strong gravity pulls wrenches from pieces of rock. Or an object may get too close to the Sun and become too hot, causing the rock to expand and fall apart. There are even interstellar micrometeroids that simply pass through our solar system from more distant space quarters.

How fast these particles move depends on which region of space they are in and the path they travel around our star, averaging about 45,000 miles per hour or 20 kilometers per second. Whether they will encounter your spaceship or not also depends on where your vehicle lives in space 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, traveling at a top speed of more than 400,000 miles per hour. “This comes down to the 4-yard line compared to Earth, which is entirely in one extreme zone,” said Malaspina, who has focused on studying micrometeorological effects on the Parker solar probe. It also moves through the densest part of a region called the zodiacal cloud, a thick disk of cosmic particles that penetrates our solar system. So Parker’s solar probe is sandblasted more often than JWST – and it strikes 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 also have a pretty good understanding of the population around the Earth. Every time a micrometeroid hits the upper atmosphere around our planet, it burns and creates meteoric smoke – fine smoke particles that can be measured. The amount of this smoke can tell us how much dust hits the Earth over time. In addition, there have been experiments at the International Space Station, where materials were mounted outside the orbital laboratory to see how often they were bombed.

Artistic depiction of NASA’s Parker solar probe
Image: NASA

While JWST lives about 1 million miles from Earth, it is still relatively close. Scientists also have an idea of ​​what is based on other missions sent to a similar orbit as JWST. And most things that fall into the telescope are not such a big deal. “Spaceships are hit by small children all the time,” says Malaspina. “By a little I mean parts of a micron – much, much, much smaller than human hair. And for the most part, spacecraft don’t even notice them. “In fact, JWST had already been hit by small micrometeroids four times before being hit by a larger micrometeroid in May.

NASA is modeling the micrometeorological environment before the launch of JWST, but in light of the recent impact, the agency has convened a new team to refine its models and better predict what could happen to the telescope after future impacts. Current modeling of micrometeoroids will try to predict things like how debris will spread through orbit if an asteroid or comet decays. This type of debris is more dynamic, says Malaspina, making it harder to predict.

At the end of the day, however, the forecast will just give you more knowledge about when a spaceship can be hit by a big speck of dust. One-off impacts like this are simply inevitable. JWST will continue to explode over time, but this was a case that NASA has always been prepared for. “You just have to live with the probability of being hit by large dust particles in the end and just do the best you can with engineering,” says Malaspina.

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