Reviving ‘Dead’ Thrusters: The Farthest Spacecraft from Earth Comes Back to Life

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Revival of Voyager 1’s Thrusters

NASA engineers have successfully revived thrusters on Voyager 1, the farthest spacecraft from Earth, just in time to prevent an anticipated communications blackout. This achievement comes as a result of upgrades to a terrestrial antenna that sends commands to both Voyager 1 and its twin, Voyager 2. The failure of its thrusters could have left the agency without a means to sustain this historic mission.

Launched in September 1977, Voyager 1 relies on multiple thruster sets for navigational control. The primary thrusters are designed to orient the spacecraft correctly, ensuring its antenna remains pointed at Earth. This alignment allows Voyager 1 to transmit valuable data collected from a remarkable distance of 15.5 billion miles (25 billion kilometers) away, deep within interstellar space.

Importance of Thruster Functionality

Voyager 1’s primary thrusters are essential for maintaining the spacecraft’s orientation to receive commands and relay data back to mission control. There are additional thrusters responsible for controlling roll, which helps the probe remain allocated towards a guide star, ensuring proper navigation in the vastness of space. If these systems fail, the entire mission faces considerable risk.

The original roll thrusters ceased functioning over two decades ago due to the failure of two internal heaters. Consequently, Voyager has relied on its backup roll thrusters for orientation. Since engineers initially accepted the failure, they didn’t foresee the spacecraft operating for another 20 years, but the need for reliability has now become critical.

The Challenge of Residue Buildup

Engineers face a significant challenge with the buildup of propellant residue in the thrusters. To mitigate clogging, they have smartly commanded Voyager 1 to alternate between its primary and backup thrusters, as well as using trajectory thrusters employed during its planetary flybys in the 1980s. However, while the trajectory thrusters assist in changing direction, they are ineffective in supporting the spacecraft’s roll.

The backup roll thrusters could face the risk of failure due to this residue buildup, which poses an imminent threat to the mission. To address this, engineers embarked on an innovative approach to revive the original roll thrusters, previously deemed irreparable after the heater failures.

Innovative Solutions for Space Challenges

After realizing the potential consequences of relying solely on the backup systems, the engineering team re-evaluated the situation. They contemplated that a circuitry disturbance affecting the power supply could potentially restart the heaters if the circuits were returned to their original position.

However, executing this fix is far from straightforward given Voyager 1’s current position beyond the heliosphere, the sun’s protective magnetic bubble. To carry out the fix, engineers had to take a risk by activating the primary roll thrusters while also attempting to fix the heaters. The heaters could only function if the thrusters were turned on, highlighting the delicate nature of the operation.

A High-Stakes Procedure

The risk was considerable, as if Voyager 1 drifted off too far from its guide star, the spacecraft’s built-in programming would activate the roll thrusters, which could result in catastrophic failure if the heaters had not yet been restored. The engineering team understood the stakes involved, especially with a significant Earth-based antenna in Canberra, Australia, undergoing upgrades, which would limit their ability to communicate with Voyager 1 until February 2026.

Despite the logistical challenges, the team was determined to command Voyager 1 to test the thrusters before a long communication blackout. The upcoming maintenance on the antenna presented a critical window for action.

Successful Thruster Activation

On March 20, the moment of truth arrived. The team sent commands to Voyager 1 to activate both the thrusters and heaters, waiting anxiously for the anticipated data transmission, which takes over 23 hours to reach Earth due to the immense distance.

As the signals began to flow back, the data indicated a significant rise in heater temperatures, confirming the success of their efforts. The team was overwhelmed with joy as they realized they had revived components long assumed to be defunct.

Celebrating a Milestone

The successful activation of the thrusters marked a triumphant moment for the engineering team. With so much uncertainty surrounding the mission, their determination and innovative thinking have set a precedent for future challenges in deep space exploration. The revival of these critical systems highlights the resilience of both technology and the dedicated teams behind such pioneering missions.

NASA continues to monitor Voyager 1 closely, ensuring it remains operational as it continues its extraordinary journey through the cosmos. This accomplishment reinforces the commitment to exploration and discovery, showing that even the oldest spacecraft can be revitalized against all odds.