After almost five decades sailing through space, NASA is trying to squeeze a few more years out of the venerable Voyager 1 deep space probe by swapping a wonky thruster system for a disused secondary one to ensure the craft can keep its radio antenna pointing at the Earth.
One of the two oldest active powered spacecraft still in existence, Voyager 1 is an incredible piece of engineering – especially when you consider that it was designed when the microchip was still a breakthrough technology and it was only supposed to operate for four years. Instead, for 47 years it has continued to function as it flies on its one-way trajectory out of our solar system.
Now some 15.2 billion miles (24.5 billion km) from Earth, Voyager 1 is the farthest-traveled human-made object ever launched into space. It's so distant that a radio signal takes 22.5 hours to reach it, which makes for very long pauses in conversations.
One of the reasons for Voyager's longevity is how NASA engineers at the Jet Propulsion Laboratory (JPL) in Pasadena, California have worked to nurse its failing systems along. This is pretty impressive when you consider that the original engineers are all dead or retired and the operating manuals are yellow with age.
The most recent problem with Voyager 1 is with one of the three thruster systems aboard. The one currently being used is the trajectory correction maneuver thruster system, which is fueled by liquid hydrazine that passes over an iridium-coated aluminum oxide catalyst and spontaneously decomposes into nitrogen and hydrogen. This results in tens-of-milliseconds-long puffs of gas at a rate of about 40 per day to keep the probe's main radio antenna pointed at Earth so it can send and receive signals.
The problem is that this system is suffering from clogging in some of the fuel lines. This is due to a rubber diaphragm in the fuel tank that's deteriorating with age, depositing silicon dioxide in the tubing. This is narrowing the tube diameter and interrupting the proper flow.
To deal with this, the engineers decided to bring another thruster system back online to take over the job. Ironically, the trajectory correction maneuver thruster system was given the job in 2018 when the attitude propulsion thrusters were clogging. Now NASA has switched back.
According to the space agency, this swap isn't a matter of just flipping a switch. In recent years, many heaters and pieces of equipment have been shut down to conserve the power from Voyager's failing nuclear generator.
The disused thrusters are now too cold to be treated lightly and would be damaged from simply turning them on. Worse, there isn't rough power left aboard to turn on a heater for the attitude thrusters without endangering the entire spacecraft.
The answer was familiar to anyone who's tried to coax an ancient car to life in the middle of winter. Do something daft. In this case, the engineers switched off one of Voyager's main heaters for an hour to free up power for the thruster heaters. On August 27, Mission Control confirmed that the gamble had paid off and the thrusters were back online after six years.
"All the decisions we will have to make going forward are going to require a lot more analysis and caution than they once did," said Suzanne Dodd, Voyager’s project manager at JPL.
Source: NASA
