If you tried to light a car that sat in a garage for decades, you may not expect the engine to respond, but a set of thrusters aboard NASA's Voyager 1 ship was successfully activated after 37 years of no use.
Voyager 1, NASA's farthest and fastest spacecraft, is the only man-made object in interstellar space, the environment among the stars.
The spacecraft, which has flown for 40 years, relies on small devices called impellers to orient themselves so they can communicate with the Earth.
These thrusters fire in tiny pulses, or "blows", that last just milliseconds, to subtly rotate the spacecraft so that its antenna points to our planet. Now, the Voyager team can use a set of four backup thrusters, dormant since 1980.
"With these thrusters still running after 37 years of use, we can extend the life of the Voyager 1 spacecraft by two or three years, "said Suzanne Dodd, Voyager's project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.
Since 2014, engineers have noticed that the Voyager 1 propellers have been using them to orient the spacecraft, called "attitude control thrusters," they have been degrading. Over time, the propellers require more puffs to emit the same amount of energy.
At 13 billion miles from Earth, there is not a mechanical shop nearby to do a set-up.
The Voyager team assembled a group of propulsion experts at NASA's Jet Propulsion Laboratory in Pasadena, California, to study the problem. Chris Jones, Robert Shotwell, Carl Guernsey and Todd Barber analyzed the options and predicted how the spacecraft would respond in different scenarios.
They agreed on an unusual solution: to try to give orientation work to a set of propellants that had been asleep for 37 years.
"The Voyager flight team unearthed data from decades ago and examined the software that was encoded in an obsolete assembly language, to ensure we could test the propellers safely," said Jones, JPL chief engineer.  In the first days of the mission, Voyager 1 flew by Jupiter, Saturn and important moons of each one. To accurately fly and point the craft's instruments at a heterogeneous mix of targets, the engineers used "trajectory correction maneuver" or TCM, propulsors identical in size and functionality to the attitude control boosters, and are located in the back of the spacecraft. But because the last planetary encounter of Voyager 1 was with Saturn, the Voyager team did not need to use the TCM thrusters since November 8, 1980. At that time, the TCM thrusters were used in a more continuous firing mode ; they had never been used in the brief bursts needed to orient the spacecraft.
All the Voyager propellers were developed by Aerojet Rocketdyne. The same type of propeller, called MR-103, also flew in another NASA spacecraft, such as Cassini and Dawn.
On Tuesday, November 28, 2017, Voyager engineers fired the four TCM thrusters for the first time. in 37 years and proven his ability to orient the spacecraft with pulses of 10 milliseconds. The team waited anxiously as the test results traveled through space, taking 19 hours and 35 minutes to reach an antenna in Goldstone, California, which is part of NASA's Deep Space Network.
Behold, on Wednesday, November 29, they learned that the TCM thrusters worked perfectly, and as well as the attitude control boosters.
"The Voyager team got more and more excited with each milestone in the propulsion test." The mood was one of relief, joy and disbelief after witnessing how these well-rested thrusters lifted the cane as if it had not happened. time, "said Barber, a propulsion engineer at JPL.
The plan going forward is to change the TCM boosters in January. To make the change, Voyager has to turn on an impeller heater, which requires power, a limited resource for the aging mission. When there is no longer enough power to operate the heaters, the equipment will return to the attitude control boosters.
The propulsion test was so good that the team will probably do a similar test on the TCM thrusters for Voyager 2, the Voyager 1 twin spacecraft. The attitude control thrusters currently used for Voyager 2 are not yet as degraded as Voyager 1.
Voyager 2 is also on the way to entering interstellar space, probably in the coming years.
The Voyager spacecraft was built by JPL, which continues to operate both. JPL is a division of Caltech in Pasadena. The Voyager missions are part of NASA's Heliophysics System Observatory, sponsored by the Division of Heliophysics of the Directorate of Scientific Mission in Washington. For more information on the Voyager spacecraft, visit: