Revived ‘Dead’ Thrusters Spark New Life for Farthest Spacecraft From Earth

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Engineers at NASA report that they have successfully restarted thrusters onboard
Voyager 1
, the most distant spacecraft from Earth, just in time before a scheduled communication shutdown.

As a result of enhancements made to an Earth-based antenna responsible for transmitting instructions to both Voyager 1 and its sibling, Voyager 2, the communication hiatus might have been triggered when the probe encountered a significant problem—a malfunctioning thruster—leaving NASA with no means to salvage this iconic mission. This recent adjustment to the craft’s initial roll thrusters, which had not functioned since 2004, may facilitate continued operations of the seasoned spacecraft until they can reconnect with Earth next year.

Launched in September 1977, Voyager 1 utilizes multiple sets of thrusters for proper operation. The main thrusters precisely adjust the orientation of the craft to maintain alignment between its antenna and Earth. This enables the transmission of collected scientific data from its unparalleled vantage point located 15.5 billion miles (25 billion kilometers) deep within interstellar space, along with receiving instructions issued by the Voyager control team.

Included within the main set are extra thrusters designed to manage the spacecraft’s roll, allowing Voyager 1 to maintain focus on a guiding star and thus stay correctly oriented in space.

If Voyager loses control of its rolling movement, the entire mission might be at risk.

However, as the thrusters operate, minute quantities of propellant residue have accumulated gradually. Until now, engineers have prevented blockages by instructing Voyager 1 to alternate between its primary and secondary thrusters for attitude control, along with using another set of thrusters employed to alter the probe’s course during planetary encounters in the 1980s. Nonetheless, these latter thrusters play no role in controlling the craft’s spin.

Voyager 1’s original roll thrusters stopped working more than two decades ago after power was lost in two internal heaters, which means the spacecraft has been relying on the backup roll thrusters to remain pointed at a guide star ever since.

I believe at that point, the team was fine with acknowledging that the main roll thrusters weren’t functioning since they had reliable backups,” explained Kareem Badaruddin, Voyager mission manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, in an official statement. “Honestly, they likely did not anticipate that the Voyagers would continue operating for yet another two decades.

Currently, the engineers working on Voyager 1 are worried that blockage from the residue might lead to the spacecraft’s secondary roll thrusters ceasing operation as early as this autumn, so they needed to address this issue.
get creative
, and also take risks, to reactivate the long-dormant main roll thrusters.

Repairing malfunctioned devices in outer space

In 2004, when the heating systems for the main roll thrusters malfunctioned, experts believed them to be irreparable. However, faced with the potential hazard of blockages, the crew went back to the design phase to investigate what had caused the issue.

Engineers contemplated the idea that an anomaly within the circuits managing the power to the heaters may have caused a switch to be toggled incorrectly—and resetting this switch to its initial state could potentially relight the heaters, subsequently activating the main roll thrusters.

However, this was not an easy fix for a mission taking place at such vast distances. The spacecraft is presently outside the heliosphere—the region dominated by the Sun’s magnetic field and particles that stretches far past Pluto’s orbital path.

The mission team decided to take a chance by activating Voyager 1’s primary roll thrusters prior to trying to repair and reactivate the heaters. This was necessary because the heaters would only work once these thrusters were turned on.

If Voyager 1 strayed too far from its reference star, the onboard system would activate the roll thrusters; however, if the heaters hadn’t been activated at that time, this automated process might have caused a minor explosion.

A nail-biting test

Along with the risks involved, the team commenced their work earlier this year under strict time limitations. An enormous ground-based telescope located in Canberra, Australia, ceased operations on May 4th for extensive upgrade activities scheduled to last until February 2026. The NASA Deep Space Network facilitates communication between the space administration and all its spacecraft; however, the Canberra station stands as the sole facility possessing sufficient signal power required to transmit instructions directly to the Voyager probes.

These enhancements to the antennas are crucial for upcoming manned lunar missions and will boost communication capabilities for our scientific endeavors in deep space,” stated Suzanne Dodd, who serves as both the Voyager project manager and the director of the Interplanetary Network at JPL. The Jet Propulsion Laboratory oversees the Deep Space Network for NASA. “Some of these missions aim to expand upon the findings from Voyager,” she added. “We’ve experienced similar downtimes previously, so we’re making all necessary preparations.

Although the antenna will function temporarily in both August and December, mission team members decided to instruct Voyager 1 to check its long-idle thrusters prior to losing contact with the craft. By doing this, should they require activating the thrusters in August, the team can ensure that using them remains an available choice.

On March 20, the team waited to see the results return from Voyager 1 after sending a command to the probe the day before to activate the thrusters and heaters. It takes more than 23 hours for data to travel back from Voyager 1 to Earth due to the sheer distance between the two.

If the test had failed, Voyager 1 might have already faced risks. However, as the team monitored the incoming data, they observed the temperatures of the thruster heaters increasing significantly, confirming that it was successful.

It was an incredibly wonderful moment. The team spirit was exceptionally high that day,” stated Todd Barber, who led the propulsion efforts for the mission at JPL, in a press release. “These thrusters were thought to be non-functional. That assessment was valid. However, one of our engineers speculated there might have been another underlying issue and believed it could be resolved. This turned out to be yet another miraculous recovery for Voyager.

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