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DART: Inside NASA’s $300m Mission to Save the World

Written by Morris M.

https://flic.kr/p/2mMm7AH

It’s probably the most-epic mission in recent NASA history.

On September 26, 2022 at 23:14 UTC, a $325 million craft went screaming through the void at over 6 km per second, headed straight for an asteroid some 11 million kilometers from Earth. 

Known as DART, the craft looked like little more than a small box with wings. A minor entry in the pantheon of NASA probes. But there’s nothing minor about what it did next. 

Using its onboard automatic sensor, DART locked onto the moonlet orbiting this asteroid. Then it dived in and – taking pictures all the way – smashed into the moonlet’s surface at incredible speed. 

On Earth, over 40 major telescopes stopped to watch the impact. In space, both Hubble and the James Webb Space Telescope turned to witness it. All of them scanning to see if DART had completed its mission: to change the asteroid’s trajectory. To knock this chunk of space rock off-course.

To demonstrate how we might one day deflect an asteroid coming to wipe out human civilization.

In today’s episode, Mega Projects is digging into Earth’s first-ever planetary defense test… and marveling at the sheer engineering genius that allowed us to impact this far-off asteroid.

Kinetic Impact

66 million years ago, a ball of fire appeared in the sky above modern-day Mexico. 

The size of a city, and traveling at 40 times the speed of sound, it impacted the Yucatan peninsula with such force that more energy was released than if the entire planet’s nuclear arsenal detonated a thousand times over.

Known as the Chicxulub asteroid, it is thought to have been what KO’ed the dinosaurs. 

Or how about the ball of fire that appeared above Siberia in 1908? 

A mere fraction of the size of the ancient dino killer, this meteor nonetheless exploded in the sky with a force equivalent to a 10 megaton bomb.

That’s the same yield as the first thermonuclear device ever tested by the USA: the great destroyer of worlds known as Ivy Mike. The fireball flattened an area of forest the size of Rhode Island. Had it exploded over a city, the Tunguska meteor could’ve killed thousands. 

It was incidents like these – and others we recently learned of – that were behind the thinking that led to DART. 

In 1998, NASA began trying to track every asteroid in our solar system bigger than 1km across – enough to end civilization as we know it. 

In 2010, that goal was revised to finding every rock with a diameter above 140m. Still big enough to destroy a medium-sized city.

The good news is that NASA found a whole bunch of them. As of 2022, it’s thought we’ve located every 1km-plus planet killer, and some 40% of potential city destroyers. The doubly good news is that none of their orbits will bring them crashing into Earth in the next 100 years.

But that still leaves over half of all danger-sized asteroids in our solar system unaccounted for. Hence NASA’s 2016 founding of the Planetary Defense Coordination Office (or PDCO) – to figure out what to do if we did uncover a hidden asteroid racing toward our world. 

Their solution? DART.

An acronym for Double Asteroid Redirection Test, DART was an attempt to demonstrate how we might knock a killer rock off course using kinetic impactor technology – a fancy way of saying “crashing a spacecraft into it really damn fast”. 

If you’ve watched Armageddon, you might be wondering why kinetic energy was chosen, rather than – say – a Bruce Willis triggered nuclear explosion.

Well, it turns out exploding an asteroid approaching Earth wouldn’t be very helpful. 

Rather than having one giant rock hit us, you’d instead get a steady bombardment of smaller rocks. The destruction would be more spread out, but it would still be destructive. 

Hence the DART spacecraft, and the plan to simply nudge a threatening rock off course. 

Not that there was anything threatening about NASA’s target for this test. You’d be hard-pressed to find a more-benign asteroid system than Didymos.

Discovered in 1996, Didymos is a common S-Type asteroid, leftover from the formation of the solar system. 

With a diameter of 780 meters (or nearly half a mile), it’s certainly big enough to be dangerous. But luckily its path never brings it closer than 11 million kilometers from Earth – for an asteroid to be considered hazardous, it needs to get more than twice as close.

From a testing standpoint, that meant there was no possible way DART could accidentally imperil Earth by interfering with Didymos’s course.

But there was an additional reason Didymos was chosen. 

It’s one of the 150 or so asteroids known to have their own moon. 

Orbiting just 1.18 km from its host, Dimorphos is a little speck of a thing: a bouldered gray dot with a diameter of only 160 meters. 

Prior to September 26, 2022, Dimorphos orbited Didymos every 11 hours and 55 minutes. We say “prior,” because DART’s goal was to change all that. 

Rather than knock the moonlet out its orbit, NASA wanted to simply test their theory: that a kinetic impact could alter an asteroid’s trajectory. In this case, by shortening Dimorphos’s orbit by anywhere from 73 seconds to 10 whole minutes. 

That’s a tiny amount in the grand scheme of things. A minor demonstration to prove a point. 

But, as we’re about to see, there was nothing minor about the DART mission.

To get to the impact stage required not only intricate planning… but also some bad ass engineering.

https://flic.kr/p/2mLGpXB

Kamikaze Craft   

Perhaps understandably for a suicide craft, one of NASA’s main goals with DART was to make it as cheap as possible. After all, there’s no point outfitting your probe with loads of fancy instruments if all you’re gonna do is crash it. 

In this, they succeeded: the entire mission cost $325 million. 

If that still sounds a lot, just compare it to the price tag of other recent missions. Perseverance Mars Rover: $2.7 billion. Europa Clipper: $5 billion. James Webb Space Telescope: $10 billion. 

Against these astronomical sums, DART’s bill was little more than spare change. The sort of money Jeff Bezos finds down the back of his sofa.

But just because DART was cheap doesn’t mean it was boring. Despite its low cost, the probe came with all sorts of interesting flourishes.

Perhaps the most-interesting of all was the solar array known as ROSA.

Two rows of panels each stretching out 8.5 meters – or nearly 28 feet – DART’s array looked like nothing less than giant wings, carrying the probe through the void. 

Given the measurements of the spacecraft itself, “giant” really is the right word. At a mere 1.8 meters in width and 1.9 meters in length, the body of the craft was comparatively tiny. 

But this is MegaProjects. We don’t mention vast solar arrays just so we can point and go “wow! Look how big they are!” 

No, DART’s “wings” are noteworthy for another reason, a reason hinted at in their full name. 

ROSA, see, stands for Roll-Out Solar Array. And that’s exactly what they did: unfurling to their full length only when DART was in space.

First tested on the International Space Station in 2017, roll-out solar panels are a massive boost to space exploration: a way to reduce bulk for cheaper launches. 

DART was the first craft to actually use them on a mission. More than just a proof-of-concept for redirecting asteroids, the probe was also proof of concept for these sorts of advances. So many, in fact, that ROSA contained a second.

Out on one of the solar arrays sat a tiny patch of experimental light-absorbing cells. 

Known as Transformational Solar Array technology, these cells were testing a new system of power generation. One that promises to use sunlight to generate three times as much power as current solar arrays.

This is important because – right now – sending probes beyond Jupiter means going so far from the Sun that solar power becomes impractical. 

That in turn means expensive fixes, like nuclear power sources. Perfect the Transformational Solar Array, and visiting the outer solar system suddenly becomes cheaper.

Already, then, we can see just how many bits of new tech NASA rolled into DART as a testing ground for future missions. And this is only scratching the surface.

There was also the NEXT-C ion propulsion system.

Ion propulsion is a concept NASA has been playing with for decades, first being used on a mission in the 1990s.

Closer to our time, ion propulsion was what allowed the Dawn probe to navigate its way to dwarf planet Ceres. A more-powerful version made by the European Space Agency is currently included onboard the BepiColombo craft heading for Mercury.

But DART was NASA’s chance to show off its next generation of ion thrusters, demonstrating their increased power.

Now, “power” here is a relative concept. The actual thrust even the most-powerful ion propulsion system can exert is equivalent to the power needed for you to hold up a sheet of paper – an amount so tiny you’d barely notice it on Earth.

In space, though, the lack of friction means even a gentle push like this can alter a craft’s trajectory if sustained, allowing for complex and delicate maneuvers that would otherwise be impossible.

Yet, for all ion thrusters and futuristic solar arrays might be awesome, the real impressive kit lay under DART’s hood. 

Yep, it’s time for us to leave our exploration of the spacecraft’s body behind… 

…and go diving into its mind.

https://flic.kr/p/2mLxKAP

Like A Missile  

Although we have zero evidence to prove it, we like to think at least one team working on DART consisted of Harry Potter fans. 

That’s because the only instrument the probe carried was a camera known as the Didymos Reconnaissance and Asteroid Camera for Optical navigation. 

The acronym it was better known by? DRACO.

Regardless of whether it was named for everyone’s favorite Slytherin or not, there’s no doubt DRACO was an integral part of DART.

Modeled on the camera New Horizons carried to Pluto, DRACO was designed to send back beautifully detailed, high-resolution images of the twin asteroid system it was aiming for. 

More than that, it was designed to aid in the probe’s ultimate destruction. 

Remember how we said the moonlet that DART was meant to impact was a mere 160m in diameter?

Well, it turns out that hitting a 160m space rock over 11 million km from Earth is a little on the tricky side. 

How tricky? Well, mission systems engineer Elena Adams described it to reporters as like standing at JFK International in New York, and throwing a dart so it would hit a bullseye at Dulles International in Washington, DC. 

For non-American viewers, that’s a distance of 361 km – further than that between Paris and London. 

Oh, and now imagine your dart is only 2.5 millimeters long. And the bullseye is somehow moving around, and you’re not even 100% sure where it is. 

In short, doing this mission conventionally would’ve been impossible. Try and preprogram the necessary maneuvers or send commands in real time, and DART would’ve gone sailing past Dimorphos.

Which is how NASA came to rely on SMART Nav.

Yet another acronym – this time for Small-body Maneuvering Autonomous Real Time Navigation – SMART Nav was the software that made sure the probe hit its bullseye.

Based on missile guidance systems developed by the Applied Physics Laboratory, the algorithm’s job was to use the DRACO camera to observe Didymos and its moonlet Dimorphos and figure out which was which.

That done, it had to lock onto the smaller object and – ignoring the bigger asteroid – direct DART right at Dimorphos.

Said aloud, it sounds simple. But making sure SMART Nav could pull such a move off was a real challenge. Especially since missing the target would effectively mean flushing $325m down the galactic toilet.

Still, for all its utility, DRACO wasn’t the only camera the probe carried onboard. 

There was also LICIACube. 

Provided by the Italian Space Agency, LICIACube hitched a ride on DART, purely to watch the NASA probe smash itself to pieces. 

A tiny satellite known as a Cubesat, the idea was to deploy it fifteen days before impact, giving it time to set itself up to record everything with its two onboard cameras. 

And while we may not know for certain if DRACO was built by Harry Potter nerds, we’re pretty confident saying LICIACube’s architects were Star Wars geeks. Its two cameras were named LUKE and LEIA. 

OK, so that’s the DART craft itself. The $300m science missile NASA sent flying off to alter an asteroid’s orbit. 

Now for the really interesting part. 

What happened when DART finally launched?

https://flic.kr/p/2mLMBTQ

Quick and Dirty

On November 23, 2021, a SpaceX Falcon 9 flared to life on the launch pad of California’s Vandenberg Space Force Base, before streaking off into dark evening sky. 

Onboard was the 610 kilogram cube that would soon unfold its solar array and become the DART probe. Ahead of it lay a ten month mission. One that would – hopefully – end in its destruction. 

“Hopefully”, because NASA needed the craft to hit Dimorphos at a specific time. Miss the moonlet this time around, and the space agency wouldn’t be able to try again until 2024. 

The problem was that DART was only intended to gently alter Dimorphos’s orbit. That meant some intense observations would be required after impact to make sure it had actually worked. 

Since Dimorphos is so small, no Earth telescopes exist capable of just zooming right in and watching it spin. Instead, observations have to be done by monitoring Didymos’s brightness. 

Every time Dimorphos passes in front or behind its parent asteroid, their combined brightness in the night sky dims. By examining that dimming before and after DART’s impact, scientists could figure out if the probe had changed the moonlet’s orbit. 

Hence why NASA wanted to reach the asteroid in September, 2022 – the point it would be closest to Earth. And therefore, easier to monitor.

As DART’s onboard navigation software guided it through the darkness of space, the flight team carried out tests to make sure SMART Nav would focus on the right target.

In July, 2022, that meant using DRACO to watch moonrise at Jupiter. Monitoring as the bright, ice world of Europa crept out from around its parent planet, like a shy kid hiding from a visitor behind daddy’s legs.

When SMART Nav successfully locked onto the much smaller object, the team gave a sigh of relief. 

If the system could differentiate a small moon beside a vast planet, it should have no trouble homing in on Dimorphos.

The asteroid finally came into view in September. 

Early in the month, the Italian LICIACube detached, scooting off into position to watch the fireworks. 

Only a couple of weeks later, the Hubble and James Webb Space Telescopes likewise turned to observe, training their powerful lenses. Hoping to catch the show in visible and non-visible wavelengths. 

Nor were they the only ones.

The NASA spacecraft LUCY – enroute to Jupiter to study Trojan asteroids – was also close enough to be among the spectators. And that was just in space.

On Earth, nearly 40 telescopes were either monitoring the crash, or dividing up telescope time to study its aftermath. Teams based in Chile, California, West Virginia and scores of other places prepared to witness the kamikaze craft.

If you’re a bit of a space geek – and, since you’re reading this, you probably are – you may have already seen the posts of what came next.

11 million kilometers from Earth, DRACO caught sight of Didymos, a great, gray blob in space. And, beyond it, a smaller speck: Dimorphos.

As the hours passed, the two grew bigger. More distinct. Images of ridges and shadows began to coalesce on Didymos. 

Then, fifty minutes before impact, SMART Nav kicked to life. DART refocused on the tiny moonlet. Swung past Didymos.

And so the final countdown began.

Slowly at first – and then suddenly – Dimorphos grew until it dominated DRACO’s eye. Until it became a gravelly world littered with jagged boulders. Boulders that got clearer and clearer until the screen went blank.

At 23:14 universal time on September 26, DART smashed into Dimorphos at 6.6km per second – equivalent to nearly 15,000 miles per hour. 

In a fraction of a second, the craft was destroyed. DRACO, the SMART Nav, the experimental solar array and ion thrusters were all reduced to fragments.

At the same time, a plume of debris was blown into space. Dust and bits of rock, kicked up by the impact, resolving into a tail billowing behind the asteroid – one stretching for 10,000 km. 

It was a moment of awe-inspiring destruction. Creation and obliteration, carried out on a cosmic scale. 

It was also the moment that the real work began.

https://flic.kr/p/2nQTBZN

Only You Can Save Mankind

At time of writing this post, the first photos from DART’s impact have already been released: grainy close-up images from LICIACube; and glorious long-distance shots by Hubble and James Webb. 

Doubtless by the time you see this, even more will have filtered in. Our production process takes a little time, and NASA has a treasure trove of images they’ll be keen to get out to the public over the next few weeks. 

But, of course, the reason for the DART mission wasn’t to create a load of awesome photos. It was to try and alter Dimorphos’s orbit with a kinetic impact. To test drive what would happen if we ever needed to knock a killer asteroid off course.

It’ll take several weeks, if not months, before we know how well it worked.

Right now, dozens of scientists are pouring over all the data DART beamed back in its last moments. Comparing it with ground-based observations, and trying to figure out what effect this asteroid redirection test had. 

The goal is for Dimorphos’s orbit to have been reduced by a minimum of 73 seconds. But some think it may have been put back a whole ten minutes.

Either way, it would mark the first time humanity has ever redirected an asteroid’s path. 

It would also have laid the ground for endless future missions.

One of those is already in the works. In 2024, the ESA is going to launch a probe called Hera designed to fly to the Didymos system, and examine up close what DART’s impact did.

The goal is to use its findings to beef up planetary defense strategies, just in case a rouge asteroid is out there, ready to threaten Earth. 

And, if one is, chances are we’ll soon find it. 

Separately to the DART mission, two fascinating telescopes are about to go online that will expand our knowledge of our cosmic backyard in mind-blowing ways.

In 2023, the Vera Rubin Observatory in Chile is expected to begin work: an unbelievably powerful telescope that will scan the entire night sky every few days and is expected to discover thousands of new asteroids.

Three years later, NASA will launch the NEO Surveyor: a space telescope specifically designed to find and track all Near Earth Objects that might pose a threat.

Importantly, it will be able to detect asteroids normally hidden by the glare of the Sun. Ones we stand no chance of seeing from Earth.

If it finds anything hazardous then – with DART behind us – humanity will already be prepared.

https://flic.kr/p/2mLKBcH

(Ends).

Sources:

Jet Propulsion Laboratory, in-depth mission overview: https://dart.jhuapl.edu/Mission/index.php 

JPL, craft overview: https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php 

JPL, Planetary Defense: https://dart.jhuapl.edu/Mission/Planetary-Defense.php 

Nat Geo, the story of DART:  https://www.nationalgeographic.com/magazine/article/nasa-intentionally-slams-dart-spacecraft-into-asteroid 

Italian Space Agency, their contribution: https://www.asi.it/en/planets-stars-universe/solar-system-and-beyond/liciacube/ 

NYT, what we learned from NASA’s DART mission: https://www.nytimes.com/live/2022/09/26/science/nasa-dart-asteroid-mission 

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