The routes the Voyager spacecraft have
taken since launch.

Because of an increasing number of clogged thrusters on the almost half-century old Voyager-1 spacecraft, now flying just beyond the heliosphere of the solar system, engineers needed to switch thrusters recently, and successfully did so in a complex dance of engineering.

They had to switch from one thruster, in which a fuel line has become increasingly clogged in the last few years due to age, to an another thruster in a different system. The switch however required other careful preparations, since Voyager-1’s nuclear power supply has dropped to a point where they have been forced to shut down almost all operations. Thus, the thrusters are not getting heated as they once were, and turning on the replacement thruster in this condition could damage it.

The team determined that the best option would be to warm the thrusters before the switch by turning on what had been deemed non-essential heaters. However, as with so many challenges the Voyager team has faced, this presented a puzzle: The spacecraft’s power supply is so low that turning on non-essential heaters would require the mission to turn off something else to provide the heaters adequate electricity, and everything that’s currently operating is considered essential.

Studying the issue, they ruled out turning off one of the still-operating science instruments for a limited time because there’s a risk that the instrument would not come back online. After additional study and planning, the engineering team determined they could safely turn off one of the spacecraft’s main heaters for up to an hour, freeing up enough power to turn on the thruster heaters.

It worked. On Aug. 27, they confirmed that the needed thruster branch was back in action, helping point Voyager 1 toward Earth.

While Voyager-1 still can do some science, the primvary purpose of this work is engineering. The goal is to keep the spacecraft running for as long as possible, until its power supply finally drops so low that it finally dies, something that is expected sometime in the next two years.

If this goal is achieved, it will be a masterpiece of exploration. Launched in 1977 along with its twin, Voyager-2, both spacecraft have been functioning non-stop now for almost a half century. Both have the longest continuously operating computer systems, and both are now beyond the edge of the solar system as influenced by the Sun’s solar wind. To get to 2027 and a full half century will be a magnificent testament not only to the engineers operating each now, but to the American engineers who built the spacecraft in the 1970s.