Can we deflect an asteroid by hitting it? NASA will try

Next week, a spacecraft will deliberately collide with an asteroid to see if its orbit can be changed. Dr. Stefania Soldini explains the reason for this test and how it will work.

A version of this article was originally published by Conversation (CC BY-ND 4.0.0 Update)

NASA agency Double Asteroid Redirection Test (DART) The spacecraft is designed to be a wonder like no other. Its days will end with a collision with an asteroid at 24,000 km / h on September 26.

I got off the ground In November 2021DART is roughly the size of a bus and was created to test and prove our ability to defend Earth from a dangerous asteroid.

It is not easy to make a direct hit at a target from a distance of 11 meters. But while that sounds far off, the asteroid was actually chosen by NASA because it is relatively close to Earth. This will give engineers the opportunity to test the spacecraft’s ability to operate on its own in the final stages before impact, as it crashes independently.

The asteroid is called the target Dimorphos, an object with a diameter of 163 meters and orbiting an asteroid 780 meters wide called Didymus. This binary asteroid system was chosen because Demorphos is in orbit around Didymus, which makes it easy to measure the outcome of the impact due to the resulting change in its orbit. However, Dimorphos currently pose no threat to Earth.

Regardless, NASA is trying nothing short of a large-scale planetary defense experiment to alter the asteroid’s path. The technique used is called the “kinetic effect,” which changes the asteroid’s orbit by colliding with it. This is basically what’s known as a safety shot in snooker, but it’s played on a planetary level between the spacecraft (like the main ball) and the asteroid.

The tiny deflection could be enough to show that this technology can indeed alter the trajectory of an asteroid on a collision course with Earth.

But the DART spacecraft will completely explode due to the collision because it will explode An effect equivalent to about three tons of TNT. In comparison, the atomic bomb dropped on Hiroshima was equal to 15,000 tons of TNT.

So, with this level of destruction and distance, how will we be able to see the breakdown?

Fortunately, the DART spacecraft does not travel alone in its quest – it carries LICIACube, a small, shoebox-sized spacecraft known as a cubesat, developed by the Italian space agency and aerospace engineering company Argotec. This little companion recently detached from the DART spacecraft and is now traveling alone to witness the impact at a safe distance of 55 kilometers.

Diagram showing the impact plans of LICIAcube and DART over the course of Dimorphos.

Graph showing the effect of the DART effect over the course of Dimorphos. Photo: NASA/Johns Hopkins APL

A cube launcher has never worked around asteroids, so this offers potential new avenues for future space exploration. The effect will also be observed from Earth using telescopes. Combined, these methods will enable scientists to confirm whether the process has been successful.

However, it may take weeks for LICIACube to send all the images back to Earth. This period will be quite nerve-wracking – waiting for good news from the spacecraft is always an emotional time for an engineer.

what happened after that?

An investigation team will look into the repercussions of the accident. These scientists will aim to measure changes in the motion of Demorphos around Didymus by observing the orbital period. This is the time Demorphos passes in front of and behind Didymus, which will happen every 12 hours.

Ground-based telescopes aim to capture images of the Demorphos eclipse as it is happening. To cause a sufficiently large deflection, a DART . must be generated At least 73 seconds orbital period change After Impact – Visible as changes in eclipse frequencies.

These measurements will ultimately determine how effective the kinetic impact technique is at deflecting the path of a potentially dangerous asteroid – we simply don’t know yet.

This is because we actually know very little about the composition of the asteroid. The great uncertainty about how powerful the Dimorphos will be has made designing a spacecraft with a bullet, a truly formidable engineering challenge. Based on ground observation, the Didymos system is suspected to be a rubble pile It is made up of many different rocks, but its internal structure is unknown.

There are also great doubts about the outcome of the effect. Substances that are then ejected will contribute to the impacts of the collision, providing additional strength. We don’t know if the crater will be formed by the impact or if the asteroid itself will suffer significant deformation, which means we can’t be sure how much force the impact will release.

futuristic missions

Our exploration of the asteroid system does not end with DART. The European Space Agency is set to launch Hera’s mission In 2024, reach Didymus in early 2027 for a closer look at the impact’s remaining effects.

By observing the distortions caused by the effect of DART on Dimorphos, the Hera spacecraft will gain a better understanding of their formation and formation. Knowing the internal properties of things like Didymus and Demorphos will also help us better understand the danger they might pose to Earth in the event of a collision.

Ultimately, the lessons learned from this mission will help investigate the mechanisms of the high-velocity impact. While lab experiments and computer models can indeed help validate scientists’ predictions of impact, large-scale experiments in space such as DART are the closest to the full picture. Discovering as much information as possible about asteroids will help us understand the force we need to hit to keep them away.

The DART mission has led to a global collaboration between scientists hoping to address the global issue of planetary defense, and with my colleagues on the DART investigation team, we aim to analyze the effects of the impact. My special focus will be on studying the motion of matter kick out of influence.

The spacecraft impact is scheduled for Monday (September 26) at 19.14 p.m. EDT (0.14 a.m. UTC +1 on September 27). You can follow Impact on NASA TV.


by Dr. Stefania Soldini

Dr. Stefania Soldini is a lecturer in Aeronautical Engineering at University of Liverpool.

10 things you need to know straight to your inbox every day of the week. Sign up for daily summarySilicon Republic summary of basic science and technology news.