NASA's Voyager 1 spacecraft has undergone a critical thruster swap to maintain its alignment with Earth. The thrusters are essential for keeping the spacecraft oriented so it can receive commands, send engineering data, and continue gathering unique scientific information. However, after 47 years in space, some of its fuel tubes have become clogged with silicon dioxide—a byproduct of aging rubber diaphragms in the spacecraft’s fuel tanks. This clogging diminishes the efficiency of the thrusters.
To address the issue, engineers meticulously planned and executed a switch to a different set of thrusters. These thrusters use liquid hydrazine, which is converted into gas and released in brief bursts to gently adjust the spacecraft’s antenna towards Earth. Normally, a healthy thruster would need to perform around 40 of these bursts daily.
Voyager 1 is equipped with three sets of thrusters: two for attitude control and one for trajectory correction. During the spacecraft's planetary flybys, both types of thrusters were used as needed. Now that Voyager 1 is on a stable path out of the solar system, its thruster needs are simplified, and any of the thruster sets can be used to keep the spacecraft pointed at Earth.
In 2002, engineers at NASA’s Jet Propulsion Laboratory observed clogging in the attitude control thrusters and switched to a secondary set. By 2018, those too showed signs of clogging, leading to a switch to the trajectory correction thrusters. However, these are now even more clogged than the previous sets, with the tube openings reduced to about half the width of a human hair. As a result, the team decided to revert to one of the earlier attitude control thruster sets.
Switching thrusters, once a straightforward task, now faces additional challenges due to the spacecraft’s advanced age, especially related to power and temperature management. The spacecraft’s dwindling power supply, generated by decaying plutonium, has led to the shutdown of non-essential systems, including heaters. This has caused the thrusters to become very cold, risking damage if activated in their current state.
To overcome this, engineers needed to warm the thrusters before the switch. This required turning on previously deactivated heaters, but given the limited power supply, they had to find a way to do this without disrupting critical systems. After careful consideration, the team decided to temporarily turn off one of the main heaters to provide enough power for the thruster heaters. This strategy proved successful, and on August 27, the team confirmed that the new thruster set was operational and realigned Voyager 1 towards Earth.
“Every decision we make now involves more analysis and caution than before,” said Suzanne Dodd, Voyager’s project manager at the Jet Propulsion Laboratory.
Voyager 1 continues its journey through interstellar space, beyond the Sun's protective bubble, exploring regions no other spacecraft are likely to visit for a long time. The mission team remains dedicated to keeping the spacecraft operational to further our understanding of the interstellar environment.
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