Old Voyager 1 engine restarted: Operation of the probe increasingly difficult
One of the Voyager 1 probe's engines has been successfully launched. It was actually out of order due to performance problems, but NASA is now relying on it.
A graphic of the Voyager 1 probe in space: NASA has reactivated one of the engines.
(Image: NASA)
The US space agency NASA's Voyager 1 space probe has successfully launched its engines. NASA employees first had to shut down several other important systems on board – due to a lack of power. The engine itself had already failed once before. The age of Voyager 1, which was launched in 1977, is increasingly presenting NASA with challenges.
The process was crucial for Voyager 1's communication with Earth: the now activated engine ensures that the probe's antenna is permanently pointed towards Earth while Voyager 1 explores the outer regions of our solar system. This is necessary so that the probe can receive commands and send scientific and technical data.
Clogged fuel pipe caused problems
The background to this complicated undertaking was a clogged fuel pipe. After 47 years of operation, silicon dioxide had accumulated in it, a by-product that is produced over time from a rubber membrane in the probe's fuel tank. The clogging means that the thrusters can generate less thrust, NASA writes in a press release.
According to the press release, all three thrusters on the probe are powered by liquid hydrazine, which they convert into gases and release in bursts lasting around ten milliseconds in order to gently tilt the spacecraft's antenna towards Earth. When intact, the engine would have to emit around 40 of these short bursts per day.
Activated engine has already been switched off once
Voyager 1 has a total of three thrusters. One is used to control the probe's course, the other two are intended to align the space probe correctly. However, the further the probe flies out into the solar system, the simpler the demands on the thrusters become, so that the purposes of the thrusters can vary.
The engine that has now been activated was also originally used to align the probe, and has already been switched off once due to a clogged fuel pipe. The mission's engineering team in southern California first noticed in 2002 that one of the two alignment thrusters was losing power due to a clogged fuel pipe. From then on, they used the second engine of this type.
When it showed the same signs of failure in 2018, the engineers shifted the task to the engine originally used for course corrections instead. Here, however, the clogging problem occurred much more quickly – so that the team was now faced with the same problem again.
The affected pipes are located in the engine itself and guide the fuel to the catalyst bed. The original diameter of around 2.5 millimeters is now just 0.0381 millimeters – roughly the diameter of a human hair.
Less and less power on board
Apparently, the engine, which has now been reactivated, now meets the requirements for aligning the probe, which should become simpler as the mission progresses.
The age of Voyager presented NASA with challenges when switching on the engine. The three radioisotope generators on board supply less and less electricity –, which they convert from the heat generated by the decay of plutonium-238 fuel blocks. After 47 years, however, this radionuclide battery is producing less and less energy, which is why NASA has already switched off many systems on board, including some radiators.
A "puzzle" of challenges
This had also cooled down the engine, which was to be switched back on. In its press release, NASA itself described the activation under the current conditions as a "puzzle": it had to be heated up beforehand so that it would not be damaged during the launch. To do this, a radiator had to be activated, and the electricity required for this had to be saved elsewhere.
To achieve this, the engineers temporarily switched off one of the scientific measuring instruments still in use, as well as the main radiators of Voyager 1. After thorough analysis, operation without the main heating elements was possible for a maximum of one hour. NASA writes in its press release that there was also a risk that the measuring device could not be put back into operation if it was switched off for too long.
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The attempt was successful: on August 27, NASA engineers reported the successful launch of the engine. However, working with Voyager 1 will remain tricky in any case: "All future decisions will require significantly more analysis and caution than before," said Voyager project manager Suzanne Dodd.
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