Arguably NASA’s most important mission is one you’ve probably never heard of. Returning to the Moon and aiming for Mars are inspiring goals—but neither may matter as much as answering a far more urgent question: what would we do if a killer asteroid were headed for Earth?

For a long time, that question lived in science fiction. But in 2022, NASA tested a real solution with the Double Asteroid Redirection Test (DART)—the first mission designed to change the motion of an asteroid.

DART spacecraft illustration — **Figure 1:** Artist’s illustration of the DART spacecraft approaching its target. Credit: NASA/Johns Hopkins APL

Why Asteroids Matter

Asteroids are rocky leftovers from the formation of the solar system about 4.6 billion years ago. While most orbit safely between Mars and Jupiter, some cross Earth’s orbit and pose a risk.

Chicxulub Impact Event (66 million years ago)

About 66 million years ago, a massive asteroid slammed into Earth near what is now the Yucatán Peninsula in Mexico, creating the Chicxulub crater. This event is widely accepted as the primary cause of the mass extinction that wiped out the non-avian dinosaurs.

Even relatively small asteroids can cause serious damage:

Chelyabinsk (2013): A small asteroid exploded over Russia, injuring over 1,000 people
Tunguska (1908): Flattened forests across a massive area
Meteor Crater: A ~50-meter asteroid created a crater over 1 km wide

Meteor Crater Arizona — **Figure 2:** Meteor Crater in Arizona shows the damage even a relatively small asteroid can cause. Credit: NASA

Side Quest: Interested in seeing how an asteroid impact can affect your home town? Try this impact simulator here – https://neal.fun/asteroid-launcher

The DART Spacecraft: Design, Systems, and Key Facts

DART spacecraft with solar arrays — **Figure 3**: The DART spacecraft with its extended Roll-Out Solar Arrays (ROSA). Credit: NASA/Johns Hopkins APL

The Double Asteroid Redirection Test (DART) spacecraft was a compact, highly efficient robotic spacecraft built to demonstrate how a spacecraft could physically alter the motion of an asteroid.

Rather than carrying a wide range of scientific instruments, DART was designed around precision navigation, autonomous targeting, and efficient propulsion.

Spacecraft Overview

Type: Kinetic impactor spacecraft
Launch Mass: ~610 kg (about 1,340 lbs)
Structure: Box-shaped central bus with extended solar arrays
Primary Function: Autonomous navigation and high-speed impact targeting

Core Spacecraft Systems

Autonomous Navigation (SMART Nav)

DART used an onboard guidance system called SMART Nav (Small-body Maneuvering Autonomous Real Time Navigation). This system enabled the spacecraft to identify and track its target in real time without human intervention.

This capability is essential for deep-space missions, where communication delays prevent real-time control from Earth.

DRACO Camera

DART carried a single primary instrument: the DRACO (Didymos Reconnaissance and Asteroid Camera for Optical Navigation).

Based on imaging technology used on NASA’s New Horizons mission
Provided high-resolution images for navigation
Enabled autonomous targeting during final approach

Power System (ROSA Solar Arrays)

DART was powered by Roll-Out Solar Arrays (ROSA), a modern solar panel design that is lighter and more compact than traditional rigid panels.

Each array deployed after launch
Lightweight and highly efficient design
Provided power for spacecraft systems and propulsion

Propulsion System (NEXT-C Ion Engine)

**Figure 6**: NASA NEXT-C Ion propulsion engine. Credit: NASA/Johns Hopkins APL

DART used NASA’s NEXT-C ion propulsion system, an advanced electric propulsion technology.

Uses xenon gas to generate thrust
Significantly more fuel-efficient than chemical propulsion
Provides continuous, low-thrust acceleration over long durations

This propulsion system allowed DART to make precise trajectory adjustments over millions of miles.

Spacecraft Design Highlights

Minimalist payload: Focused on navigation rather than scientific instruments
Autonomous targeting: No manual control required during final approach
Efficient propulsion: Enabled long-duration maneuvering with limited fuel
Lightweight structure: Optimized for speed and impact effectiveness

Supporting Technology

DART also deployed a small companion satellite called LICIACube, provided by the Italian Space Agency. While separate from the main spacecraft, it was used to capture images of the impact and resulting debris.

The Target: A Binary Asteroid System

DART targeted a pair of asteroids known as Didymos and Dimorphos.

Didymos – the larger asteroid (~780 meters wide)
Dimorphos – a smaller moon (~160 meters wide)

Dimorphos orbits Didymos, which made it possible to measure any change in its orbit after the impact.

How DART Worked

The concept behind DART was simple but powerful:

Crash a spacecraft into an asteroid to slightly change its path.

The spacecraft weighed about 1,500 pounds (676 kg) and struck Dimorphos at roughly 14,000 miles per hour.

In its final moments, DART used an onboard camera and autonomous navigation system to guide itself directly into the asteroid.

Dimorphos close-up before impact — **Figure 4:** One of the final images of Dimorphos taken by DART just seconds before impact. Credit: NASA/Johns Hopkins APL

The Impact

On September 26, 2022, DART successfully impacted Dimorphos.

The collision blasted a huge amount of material into space, forming a long, comet-like tail stretching tens of thousands of kilometers.

DART ejecta plume — **Figure 5:** The ejecta plume captured by the LICIACube spacecraft shortly after impact. Credit: ASI/NASA

Did It Work?

Yes—and even better than expected.

Expected orbital change: at least 73 seconds
Actual change: 33 minutes

This proved that a spacecraft can measurably alter the motion of an asteroid.

Why This Matters

If we discover a hazardous asteroid early enough, even a tiny change in its speed can cause it to miss Earth entirely.

DART showed that planetary defense is not science fiction—it’s something we can actually do.

Final Thoughts

DART represents one of the most important milestones in modern space science.

For the first time, humanity has changed the motion of a natural object in space—and that capability could one day protect our planet.

As a NASA Solar System Ambassador, my goal is to bring missions like DART to the public—because understanding space is the first step toward protecting Earth.

DART: Humanity’s First Planetary Defense Test