Considering how the odds were stacked against it, Voyager 1’s new lease on life, even if just three years at most, is nothing short of a miracle. The spacecraft has been traveling space for 40 years and, since 2012, has left our solar system, becoming the first and so far only man-made interstellar object. So when crucial parts of it start failing, there is almost no hope. Fortunately, Voyager 1 seems to refuse to give up the ghost and its backup thrusters have been successfully fired up, even after being left unused for 37 years.
Voyager 1 doesn’t actually need thrusters to continue drifting through space. It does need them, however, to orient itself in order to communicate with Earth. These “attitude control thrusters”, as they are called, have been degrading for three years now, expending a greater amount of energy and shortening Voyager 1’s mission lifespan.
Fortunately, those aren’t the only thrusters onboard. Voyager 1 also has “trajectory correction maneuver” thrusters or TCMs, but they worked differently and were used for a different purpose, despite having the same build. The main thrusters fired off in pulses called “puffs” to subtly rotate the spacecraft. The TCMs, on the other hand, fired off continuously when in use.
The TCMs haven’t been in use since 1980, however, when it was needed to stabilize the Voyager 1 during its fly bys of Jupiter, Saturn, and their moons. NASA scientists and propulsion experts weren’t also sure if the thrusters would work in short bursts, if they worked at all. Having slept for nearly four decades, the odds seemed low.
You can then imagine their mixed incredulity and glee when, on November 29, they received data that Voyager 1’s backup thrusters worked flawlessly in a test run. Sure, each of the four the thrusters would need to be heated individually, which would consume even more energy than they normally would. The alternative, however, would be to give the Voyager 1 an early retirement. NASA plans to switch to the backup thrusters in January and when there’s no longer enough power for those, switch back to the main ones. They also plan to perform a similar test on the younger Voyager 2, in the eventuality that its still perfectly functioning main thrusters give out.