On August 27, 2024, Voyager 1 engineers successfully fixed a clogged fuel line on the spacecraft while working 24.6 billion kilometers from Earth.
The fuel pipeline allows the spacecraft’s propulsion system to keep Voyager 1’s antenna pointed back toward Earth to receive commands and transmit data from scientific instruments as it continues its mission in the interstellar space.
While the blocked fuel line could be fixed by simply switching to another thruster system, which should be a simple matter since Voyager 1 had three thrusters in total, considering that the spacecraft was built in the 1970s, has been in space for 47 years, and has had its systems shut down to conserve energy and maximize its mission life, fixing the problem is not an easy task.
Voyager 1’s propulsion system consists of two directional thrusters, which are used to orient the spacecraft to explore objects or image planets in the Solar System, and one orbital-adjusting thruster, which is used to adjust the spacecraft’s position in space, such as to orient the spacecraft to Jupiter and Saturn.
When NASA decided to extend the Voyager 1 mission after its Saturn flyby in 1980, they used directional thrusters as their primary propulsion system to turn the satellite’s antenna back to Earth, before switching to another directional thruster in 2002 and then to orbital correction thrusters in 2018, where they have been since.
Voyager 1’s three propellants used liquid hydrazine, which was converted to a gas to provide a gentle thrust to slowly orient the satellite’s antenna toward Earth as it moved away at 16.9995 kilometers per second.
But over decades of continuous operation, the fuel delivery tubes began to become clogged with silicon dioxide. Mission engineers discovered the blockage in the fuel delivery tubes through gasification, reducing the 0.25-millimeter diameter of the delivery tube to just 0.035 millimeters for liquid hydrazine delivery. This made the orbital-direction thrusters less efficient than the previous directional thrusters.
That led engineers to make the decision to revert to a directional thruster, which was both challenging and risky, as Voyager 1’s heaters and non-essential equipment were turned off to conserve energy, leaving the spacecraft exposed to freezing temperatures, as were two other thrusters that were shut down.
Engineers had to find a way to turn on the heaters to help get the thrusters up to temperature and ready for use without risking damage. But turning on the heaters would be energy-intensive, so some systems had to be shut down to compensate. Every system on Voyager 1 that’s currently on is essential to the mission.
The mission team on Earth had made it a point not to shut down the science probe at all, given the risk that it would not function again, so engineers decided to shut down Voyager 1’s core heater for an hour to save energy and keep the thrusters warm.
Finally, the mission team received data from Voyager 1 confirming that the directional thrusters had resumed, having waited more than 45 hours for the round-trip transmission at the speed of light, and allowing Voyager 1 to point its antenna back to Earth with precision.
“Every decision we make now will require more careful analysis and data than ever before,” said Suzanne Dodd, Voyager project manager. That’s because Voyager 1 and Voyager 2 are both more than 47 years old and are currently operating in a region of space beyond the Sun’s magnetic field, where no other spacecraft will travel in the near future. The mission team will need to find a way to maximize the duration of the two spacecraft’s data transmissions back to Earth.
And while the mission team is working on this problem, or as you read this article, Voyager 1 is moving away from Earth by 16.9995 kilometers with every passing second, never to return to the solar system.
picture: NASA / JPL
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