DART MISSION: HUMANITY’S FIRST STEP TOWARDS PLANETARY DEFENSE
Introduction:
As we gaze into the night sky, we may marvel at the wonders of space, but we must also acknowledge that, beyond our fragile world, the universe operates on rules that can be as unforgiving as they are magnificent. Each tremor beneath our feet and every whisper of the wind reminds us just how fleeting our time here is, and reminds us over and over that our time here is momentary, and our existence hangs by a thread in the vastness of the universe.
The Chelyabinsk Incident:
One such incident dates back to February 15th. The city of Chelyabinsk in Siberia awoke to an ordinary winter day, unaware that it was about to be in the pages of history. Just before 9:20 am, a blinding flash tore across the sky, brighter than the Sun, soaring through the Earth’s atmosphere at a staggering speed of over 10 miles per second (18 kilometres per second). The atmospheric entry of what was later found to be a small meteor had created a shockwave that rippled through the air and sent a deafening sonic boom echoing through the city. In an instant, windows shattered, buildings trembled, and over 1,500 people were injured from flying glass and debris. Shards of echoes and the sounds of panic and confusion had filled the streets of Chelyabinsk[1].
This incident served as a wake-up call to the world that something as small as a car could wreak havoc on an entire city and that apocalypses don’t always announce themselves with a bang; they can sneak up on us in the form of fragments of rock and metal hurtling through space at staggering speeds, ready to deliver a blow with insane amounts of momentum. At this time, scientists started to pay closer attention to the risk of hazardous near-Earth objects, particularly asteroids – the rocks considered failed planets but could unleash devastation on other planets and alter their course of history.
The Need for Planetary Defense:
While the asteroid that passed over Chelyabinsk had been relatively small, larger ones with the potential to cause global catastrophes are still out there, hiding and floating silently through the void, leaving us uncertain of their arrival. While the scars of that fateful day would heal, the question remained: How prepared are we to face the next asteroid threat? Because the threat of disaster exists in every piece of metal and rock that hurtles through the solar system.
These are not merely speculations; this has happened in the past. The most popular example concerns the extinction of dinosaurs[2], the reptiles that ruled the world, which were wiped off by an asteroid 66 million years ago.
And humanity could meet the same fate if we don’t heed the warning signs of our time. And this answers the question of why planetary defense becomes the need of the hour. Although humanity still has a long way to go, we’ve just taken the first step in planetary defence – a mission named DART, short for the Double Asteroid Redirection Test, was a groundbreaking effort (quite literally), aimed at demonstrating our ability to protect Earth from potential asteroid threats
DART’s Ideation and Initiation:
Its goal was simple, yet profound: to determine whether an asteroid’s trajectory might be altered by the kinetic energy and momentum that a spaceship delivered. The target was the binary asteroid system Didymos, which was discovered in 1996 and consisted of a bigger asteroid that was roughly 780 meters wide and a smaller partner called Dimorphos, which was about 160 meters wide. The selection of Didymos and Dimorphos for the mission was mostly based on their relative proximity to Earth as it is just 2.7 Astronomical Units away from Earth, as compared to more popular bodies such as Ceres which lie over 3.25 AU. Furthermore, the asteroids were big enough to be seen from Earth, which guarantees that variations in their orbits can be monitored clearly.
Now that the target was locked, it was time to develop a mission that could potentially alter the course of Didymos. To test several asteroid deflection techniques, NASA and the European Space Agency embarked on their own independent asteroid deflection missions in 2015. But as fate would have it, the agencies came together, giving birth to the AIDA initiative—a plan featuring two spacecraft, the European Asteroid Impact Mission (AIM), and the American counterpart named DART. While the objective of AIM was to orbit Didymos to study its composition and the characteristics of its moonlet, Dimorphos, the latter was tasked to collide with Dimorphos and test the feasibility of asteroid deflection missions.
But as the project unfolded, there was a twist in the tale: AIM was cancelled for certain reasons, and its place was taken by another mission named Hera, which would also study the aftermath of DART’s impact years later. However, the DART team, with its share of ups and downs, had moved from paper to prototype by June 2017.
The Engineering of DART:
It was a rather simple mission with several instruments.
SMART NAV (Small body Maneuvering Autonomous Real-Time NAVigation) and DRACO (Didymos Reconnaissance and Asteroid Camera for Optical navigation) were the cameras used to take close-up pictures of Didymos and Dimorphos as the spacecraft passed by.
DART also used the Roll Out Solar Array (ROSA) technology, the same technology used on the ISS. This also incorporated the Transformational Solar Array technology, featuring high-efficiency SolAero Inverted Metamorphic (IMM) solar cells and reflective concentrators to generate up to three times more power compared to traditional solar arrays, ensuring that the spacecraft has the necessary energy to perform its operations.
DART also uses a Spiral Radial Line Slot Array (RLSA) high-gain communication antenna that operates at X-band frequencies. It also was supposed to feature the NEXT-C gridded ion thruster, a solar electric propulsion system, until early tests indicated higher than expected current loads, leading the mission team to decide against its use for regular operations[3]. Hence DART relied on conventional thrusters powered by hydrazine, and this ion thruster was kept as a contingency option.
Development and Launch:
The team had to overcome some obstacles while working on the mission, including tight schedules, financial constraints, and technological difficulties. But as the saying goes, each setback is a setup for a comeback. Following years of planning and collaboration with space agencies around the world, DART was finally ready to make history.
On November 24th, 2021, the spacecraft lifted off from Vandenberg Space Force Base in California aboard a SpaceX Falcon 9 rocket, beginning its journey of over 6.8 million miles (11 million km) journey. The payload, stored in Falcon 9’s second stage, was propelled directly into a heliocentric orbit. Over the next nine months, it would be making a few course adjustments with its chemical thrusters. By mid-2022, as DART got closer, it started sending back stunning images of the asteroids, revealing their surfaces in incredible detail. To ensure DART was ready for the important impact, the mission crew monitored its systems closely
The big day:
Then, on September 26, 2022, the big moment arrived. In the hours leading up to the collision, DART made its final manoeuvres, with Dimorphos gradually growing larger in the spacecraft’s view. At 7:14 PM UTC, DART collided with Dimorphos at a remarkable speed of approximately 14000 miles per hour (22500 kmph). The head-on impact of the DART spacecraft, travelling at 6.6 km/s (4.1 miles/s), imparted an energy equivalent to about 11 gigajoules, roughly the same as three tonnes of TNT[4].
Soon after the impact, telescopes all around the world sprung into action. In eager anticipation, scientists began collecting data to monitor any changes in Dimorphos’ orbit around its sister asteroid, Didymos. According to scientists, more than a million kilograms of dusty ejecta were pushed into space by DART’s impact. The ejecta created a tail that extended at least 30000 kilometres (about 19000 miles) with a mass of at least 1000 tonnes[5]. Initial observations indicated that DART had successfully altered the asteroid’s trajectory, and upon further observations, it was calculated that the impact significantly altered Dimorphos’s orbit, reducing its orbital period from 11 hours and 52 minutes by approximately 33 minutes.
According to the analysis of the data, DART’s impact had a measured momentum enhancement factor of 3.6, meaning that roughly 3.6 times as much momentum than what would have happened if the asteroid had merely absorbed the spacecraft without ejecting any material. This also suggests that future missions might use smaller impactors or shorter lead times to effectively nudge asteroids off their paths.
The DART mission showed that the impact reduced Dimorphos’s speed by about 2.7 millimetres per second right away. Furthermore, the change in momentum was amplified by 2.2 to 4.9 times, highlighting how important the material kicked up by the impact was in enhancing that momentum change. Although the orbital shift was small, it could add up over time to make a significant difference. This wasn’t just a win for NASA; it was a major step forward in our efforts in planetary defense.
Conclusion:
As the data continued to pour in, the scientific community had been abuzz with enthusiasm. Scientists from all over the world exchanged their research, examining the makeup of the material that was expelled and its impact on the dynamics of Didymos. The mission demonstrated that humanity could change an asteroid’s course, giving optimism that similar tactics can be used in the future to defend Earth from any dangers.
As we reflect on the accomplishments of the DART mission, it is clear that our approach to space threats has evolved, and this is just the beginning of humanity’s efforts to protect Earth. In addition to accomplishing its main objective, DART has inspired a new era of planetary defense research and cooperation, provided hope to future generations, and served as a reminder that we are not powerless against the forces of nature. It also signalled a revolutionary change in humanity’s profound connection with the cosmos. Through the challenges and lessons learned, the DART mission paved the way for a new era in planetary security, one in which the steadfast spirit of human ingenuity would light the way forward. And the work doesn’t stop here – this is just the beginning of a new era in space exploration, where we continue to actively shape our destiny among the stars.
References
Author: Aakaash A