Engineers of the NASA managed to activate a set of thrusters that Voyager 1 hadn’t used it for decades to solve a problem that could prevent the 47-year-old spacecraft from communicating with Earth being billions of kilometers away.
When Voyager 1 launched into space on September 5, 1977, no one expected the probe to still be operational today. As a result of its exceptionally long mission, the spacecraft has faced problems as its parts age in the icy regions beyond our Solar System.
When a problem arises, engineers at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, have to get creative, paying close attention to how the spacecraft will react to any changes.
Voyager 1 is currently the most distant spacecraft from Earth, at about 15 billion miles away. The spacecraft operates beyond the heliosphere — the bubble of the Sun’s magnetic fields and particles that extends far beyond the orbit of Pluto — where its instruments collect samples directly from interstellar space.
Earlier this year, engineers identified a problem when a fuel tube on one of Voyager’s thrusters became clogged. If these parts are clogged, they can’t generate enough thrust to keep the spacecraft stable.
Voyager’s thrusters keep the spacecraft oriented so it can communicate with Earth.
If the spacecraft is not positioned so that its antenna is pointed toward our planet, the spacecraft will not be able to “hear” commands from mission control or send data back, according to Calla Cofield, a media relations specialist at JPL.
“If the thrusters that keep the antenna pointed at Earth get clogged, that would be the end of the mission,” she said.
The team realized they would have to send commands to the spacecraft to switch to another set of thrusters, but the fix wouldn’t be simple.
A recurring problem
This isn’t the first time Voyager 1 has had to switch to a different set of generators in recent decades. Fortunately, the spacecraft has three thruster groups: two for attitude control and one dedicated to trajectory correction maneuvers.
Voyager 1 used the thrusters for a variety of purposes while flying past planets such as Jupiter and Saturn in 1979 and 1980, respectively.
The spacecraft is now traveling on an unchanging trajectory away from our solar system, so it needs only a set of thrusters to keep its antenna pointed toward Earth. To power these thrusters, liquid hydrazine is converted to gas and released in about 40 small thrusts a day to keep Voyager 1 properly oriented.
Over time, engineers discovered that a fuel tube inside the thrusters could become clogged with silicon dioxide, a byproduct of the tank’s rubber diaphragm aging. As the generators became clogged, they delivered less power.
In 2002, the crew commanded Voyager 1 to switch to the second set of attitude control thrusters when the first began to show signs of clogging. Engineers switched back to the trajectory correction engine group in 2018 when the second set also showed signs of clogging.
However, when the team recently checked the status of Voyager’s trajectory correction instruments, they were even more clogged than the previous two sets.
When the team initially switched to trajectory correction thrusters six years ago, the tube opening was 0.25 millimeters in diameter. Now, clogging has reduced it to 0.035 millimeters — half the width of a human hair, according to NASA.
It was time to return to one of the attitude control generator sets.

Making a challenging exchange
As Voyager 1 and its twin probe, Voyager 2, aged, the mission team slowly turned off nonessential systems on both spacecraft to conserve power, including heaters.
As a result, Voyager 1’s components are cooler now, and the team knew they couldn’t simply send a command to immediately switch to one of the attitude control thrusters without first warming them up.
However, Voyager 1 doesn’t have enough power to turn on the heaters without turning off something else, and its science instruments are too valuable to shut down because they may never work again, the team said.
After rethinking their strategy, the team realized they could turn off one of the spacecraft’s main heaters for about an hour, allowing engineers to turn on the thruster heat generators and make the switch safely.
That plan worked, and by August 27, Voyager 1 was back to relying on one of its original sets of engines to stay in contact with Earth.
The team has taken steps to use the thrusters less frequently and expects the original set to last another two to three years, said Todd Barber, Voyager’s propulsion engineer.
Once the spacecraft exhausts that set of generators, Voyager 1’s only remaining option will be the other set of attitude control thrusters that are already obstructed.
“Every decision we have to make from now on will require much more thought and caution than ever before,” Suzanne Dodd, Voyager project manager, said in a statement.
Voyager 2 also underwent thruster swaps in 1999 and 2019, and “the situation there is less critical,” Todd Barber said. Voyager 2 has traveled more than 20 billion kilometers from Earth.
The information collected by these long-lasting probes is helping scientists understand the comet-like shape of the heliosphere and how it protects Earth from energized particles and radiation in interstellar space.
This content was originally published in NASA activates Voyager 1 thrusters to avoid communication problems on the CNN Brasil website.
Source: CNN Brasil

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