The tenuous power situation onboard the veteran Voyager 1 spacecraft has required engineers to perform a delicate balancing act while switching between thrusters as fuel lines gradually become clogged.

The Voyagers have three sets of thrusters: two sets of attitude propulsion thrusters and one set of trajectory correction maneuver thrusters. As the mission has stretched beyond the wildest imaginations of the original engineers, the fuel lines have become clogged.

In 2002, the mission engineering team noticed that some of the fuel tubes in the attitude propulsion branch were clogging. Not a problem - the team switched to the second branch. Then that branch began to suffer the same, so the team switched to the trajectory correction thrusters instead.

The thrusters are designed to point the spacecraft's antenna to Earth. Gas produced from liquid hydrazine is used to generate pulses measured in milliseconds to gently tilt the Voyagers to the proper orientation.

However, now the correction thruster tubes are also clogged, even more than the original branches. "Where the tube opening was originally only 0.01 inches (0.25 millimeters) in diameter, the clogging has reduced it to 0.0015 inches (0.035 mm), or about half the width of a human hair," NASA said.

The clogging is caused by silicon dioxide, a byproduct that appears with age - the Voyagers are approaching half a century in space - from a rubber diaphragm in the spacecraft's fuel tank.

Switching to different thrusters would have presented no problem in decades past. Now, however, the dwindling power is presenting challenges for engineers. Over time, the Voyager team has been turning off non-essential systems, including some heaters, to eke out the electrical power a little longer.

This has worked well yet has also resulted in the spacecraft getting colder. And it means that firing the attitude thruster branches could damage them. However, the heaters for those branches were turned off for a reason, and turning them back on would further drain the remaining electrical power.

Could one of the remaining science instruments be turned off temporarily to free up some power? No - engineers worried that the instrument would not come back online afterward.

In the end, the Voyager team turned off one of the spacecraft's main heaters for an hour to free up enough power to warm the thrusters.

It worked, but highlights how tenuous the power situation has become aboard the veteran spacecraft.

Suzanne Dodd, Voyager's project manager at the Jet Propulsion Laboratory (JPL), said: "All the decisions we will have to make going forward are going to require a lot more analysis and caution than they once did."

We asked Dr Garry Hunt, one of the original Voyager scientists for his thoughts on the latest engineering feat. He replied with one word: "Brilliant." ®

https://www.theregister.com//2024/09/12/voyager_power_issues/