Voyager 1’s Long-Dead Thrusters Fire Again After 20 Years – Just in Time

Against all odds, NASA engineers brought back to life a set of Voyager 1’s thrusters thought to be dead since 2004.

With the spacecraft now in deep interstellar space, the fix was driven by growing concerns that its currently used thrusters might soon fail. Racing against time before a long communications blackout, the team made a daring and intricate attempt to restore the dormant system. Their creative theory paid off, turning a nearly-forgotten system into a mission-saving backup, just in time.

Reviving “Dead” Voyager 1 Thrusters

In a remarkable engineering feat, NASA scientists at the Jet Propulsion Laboratory (JPL) in Southern California have reactivated a set of thrusters on the Voyager 1 spacecraft that hadn’t worked since 2004. These thrusters had been considered out of commission for two decades. Restoring them wasn’t easy—it took a mix of clever thinking and some risk, but the team wanted a reliable backup. That’s because the main thrusters currently in use are showing signs of clogging from residue, which could stop them from working as soon as this fall.

The timing was critical. NASA needed to revive these backup thrusters before May 4, when the powerful Earth-based antenna responsible for sending commands to Voyager 1 and its twin, Voyager 2, would go offline for several months of scheduled upgrades.

Navigating Interstellar Roll Control

Launched back in 1977, both Voyagers are now flying through interstellar space at speeds of around 35,000 miles per hour. To stay in touch with Earth, they use small thrusters to adjust their orientation, keeping their antennas aimed precisely at our planet so they can send and receive signals.

Each Voyager has a set of primary thrusters that control movements in multiple directions, along with separate thrusters for a specific type of movement called roll motion. From Earth’s perspective, this roll looks like the antenna spinning like a vinyl record. That subtle motion helps the spacecraft lock onto a guide star to stay properly aligned.

The spacecraft also carry backup thrusters for roll control. A third set, which was originally used during their planetary flybys, was brought back online in 2018 and 2019. However, those thrusters aren’t capable of handling roll adjustments, which are crucial for maintaining contact with Earth.

Thruster Failure and Backup Strategy

To manage the clogging tubes in the thrusters, engineers switch between the sets of primary, backup, and trajectory thrusters of both Voyagers. But on Voyager 1, the primary roll thrusters stopped working in 2004 after losing power in two small internal heaters. Engineers determined the broken heaters were likely unfixable and opted to rely solely on Voyager 1’s backup roll thrusters to orient the star tracker.

“I think at that time, the team was OK with accepting that the primary roll thrusters didn’t work, because they had a perfectly good backup,” said Kareem Badaruddin, Voyager mission manager at JPL, which manages the mission for NASA. “And, frankly, they probably didn’t think the Voyagers were going to keep going for another 20 years.”

New Theory Rekindles Old Hope

But without the ability to control the spacecraft’s roll motion, a variety of issues would arise that might threaten the mission, so the engineering team decided to reexamine the 2004 thruster failure. They began to suspect that an unexpected change or disturbance in the circuits that control the heaters’ power supply had effectively flipped a switch to the wrong position. If they could turn the switch back to its original position, the heaters might work again, enabling them to reactivate the primary roll thrusters and use them if the backup roll thrusters that have been used since 2004 become completely clogged.

Risky Restart Under Tight Timeline

The solution required some puzzle-solving. The team would have to turn on the dormant roll thrusters, then try fixing and restarting the heaters. If, during that time, the spacecraft’s star tracker drifted too far from the guide star, the long-dormant roll thrusters would automatically fire (thanks to the spacecraft’s programming). And if the heaters were still off when they fired, it could trigger a small explosion, so the team needed to get the star tracker pointed as precisely as possible.

Why Only One Antenna Could Save the Day

It would be a race, and the team faced additional time pressure: From May 4, 2025, through February 2026, Deep Space Station 43 (DSS-43), a 230-foot-wide (70-meter-wide) antenna in Canberra, Australia, that’s part of NASA’s Deep Space Network, would be undergoing upgrades. It would be offline for most of that time, with brief periods of operation in August and December.

Although the Deep Space Network has three complexes equally spaced around the globe (in Goldstone, California, and Madrid, in addition to Australia) to ensure constant contact with spacecraft as Earth rotates, DSS-43 is the only dish with enough signal power to send commands to the Voyagers.

“These antenna upgrades are important for future crewed lunar landings, and they also increase communications capacity for our science missions in deep space, some of which are building on the discoveries Voyager made,” said Suzanne Dodd, Voyager project manager and director of the Interplanetary Network at JPL, which manages the Deep Space Network for NASA. “We’ve been through downtime like this before, so we’re just preparing as much as we can.”

The team wanted to make sure the long-dormant thrusters would be available when the dish is back online briefly in August, by which time the thrusters currently in use on Voyager 1 might be completely clogged.

A 20-Year-Old Long Shot Pays Off

The advance work paid off: On March 20, the team watched as the spacecraft executed their commands. Because of Voyager’s distance, the radio signal takes over 23 hours to travel from the spacecraft to Earth, meaning everything the team saw happening had occurred almost a day earlier. If the test had failed, Voyager might already have been in danger. But within 20 minutes, the team saw the temperature of the thruster heaters rise dramatically and knew they had succeeded.

“It was such a glorious moment. Team morale was very high that day,” said Todd Barber, the mission’s propulsion lead at JPL. “These thrusters were considered dead. And that was a legitimate conclusion. It’s just that one of our engineers had this insight that maybe there was this other possible cause and it was fixable. It was yet another miracle save for Voyager.”

More About Voyager

Voyager 1 and 2 are NASA’s iconic deep space explorers, launched in 1977 to study the outer planets—Jupiter, Saturn, Uranus, and Neptune. Now located about 15 billion miles (Voyager 1) and 13 billion miles (Voyager 2) from Earth, the spacecraft have traveled farther than any human-made objects in history.

After completing their planetary missions, both Voyagers became the first and only spacecraft to enter and transmit data from interstellar space—the vast region beyond our solar system’s planets and outside the heliosphere, the Sun’s protective bubble of particles and magnetic fields. Their ongoing journey continues to provide groundbreaking insights into the distant boundaries of our solar neighborhood.

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