Voyager 1 staff accomplishes tough thruster swap

Engineers engaged on NASA’s Voyager 1 probe have efficiently mitigated a difficulty with the spacecraft’s thrusters, which hold the distant explorer pointed at Earth in order that it could actually obtain instructions, ship engineering knowledge, and supply the distinctive science knowledge it’s gathering.

After 47 years, a gas tube contained in the thrusters has grow to be clogged with silicon dioxide, a byproduct that seems with age from a rubber diaphragm within the spacecraft’s gas tank. The clogging reduces how effectively the thrusters can generate drive. After weeks of cautious planning, the staff switched the spacecraft to a distinct set of thrusters.

The thrusters are fueled by liquid hydrazine, which is changed into gases and launched in tens-of-milliseconds-long puffs to softly tilt the spacecraft’s antenna towards Earth. If the clogged thruster have been wholesome it will have to conduct about 40 of those brief pulses per day.

Each Voyager probes function three units, or branches, of thrusters: two units of perspective propulsion thrusters and one set of trajectory correction maneuver thrusters. Through the mission’s planetary flybys, each sorts of thrusters have been used for various functions. However as Voyager 1 travels on an unchanging path out of the photo voltaic system, its thruster wants are less complicated, and both thruster department can be utilized to level the spacecraft at Earth.

In 2002 the mission’s engineering staff, primarily based at NASA’s Jet Propulsion Laboratory in Southern California, seen some gas tubes within the perspective propulsion thruster department getting used for pointing have been clogging, so the staff switched to the second department. When that department confirmed indicators of clogging in 2018, the staff switched to the trajectory correction maneuver thrusters and have been utilizing that department since then.

Now these trajectory correction thruster tubes are much more clogged than the unique branches have been when the staff swapped them in 2018.

The clogged tubes are situated contained in the thrusters and direct gas to the catalyst beds, the place it’s changed into gases. (These are completely different than the gas tubes that ship hydrazine to the thrusters.) The place the tube opening was initially solely 0.01 inches (0.25 millimeters) in diameter, the clogging has decreased it to 0.0015 inches (0.035 mm), or about half the width of a human hair. Because of this, the staff wanted to change again to one of many perspective propulsion thruster branches.

Warming up the thrusters

Switching to completely different thrusters would have been a comparatively easy operation for the mission in 1980 and even 2002. However the spacecraft’s age has launched new challenges, primarily associated to energy provide and temperature. The mission has turned off all non-essential onboard techniques, together with some heaters, on each spacecraft to preserve their step by step shrinking electrical energy provide, which is generated by decaying plutonium.

Whereas these steps have labored to cut back energy, they’ve additionally led to the spacecraft rising colder, an impact compounded by the lack of different non-essential techniques that produced warmth. Consequently, the perspective propulsion thruster branches have grown chilly, and turning them on in that state may injury them, making the thrusters unusable.

The staff decided that the most suitable choice could be to heat the thrusters earlier than the change by turning on what had been deemed non-essential heaters. Nevertheless, as with so many challenges the Voyager staff has confronted, this introduced a puzzle: The spacecraft’s energy provide is so low that turning on non-essential heaters would require the mission to show off one thing else to supply the warmers sufficient electrical energy, and all the things that is at the moment working is taken into account important.

Learning the problem, they dominated out turning off one of many still-operating science devices for a restricted time as a result of there is a threat that the instrument wouldn’t come again on-line. After further examine and planning, the engineering staff decided they might safely flip off one of many spacecraft’s essential heaters for as much as an hour, releasing up sufficient energy to activate the thruster heaters.

It labored. On Aug. 27, they confirmed that the wanted thruster department was again in motion, serving to level Voyager 1 towards Earth.

“All the choices we should make going ahead are going to require much more evaluation and warning than they as soon as did,” mentioned Suzanne Dodd, Voyager’s mission supervisor on the Jet Propulsion Laboratory which manages Voyager for NASA.

The spacecraft are exploring interstellar space, the area outdoors the bubble of particles and magnetic fields created by the solar, the place no different spacecraft are prone to go to for a very long time. The mission science staff is working to maintain the Voyagers going for so long as potential, to allow them to proceed to disclose what the interstellar surroundings is like.