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Engineers extend Voyager-2’s life by tapping into reserve power supply

Engineers have begun using a backup power supply on the Voyager-2 spacecraft — launched in 1977 and presently traveling in interstellar space — in order to extend the life of one of its five instruments one additional year.

To help keep those instruments operating despite a diminishing power supply, the aging spacecraft has begun using a small reservoir of backup power set aside as part of an onboard safety mechanism. The move will enable the mission to postpone shutting down a science instrument until 2026, rather than this year.

The solution is only temporary, as the end of the mission is inevitable as its radioisotope thermoelectric generator (RTG) was only designed to provide power for about a half century (!). As time passes its power supply slowly declines, forcing engineers in recent years to shut down other systems to allow the science instruments to operate. That all the other systems on both Voyager-1 and Voyager-2 remained operational until the end of their RTGs tells us how well these spacecraft were built by their 1970s creators.

Assuming this works, engineers will do the same thing on Voyager-1 sometime next year. In both cases, however, power from the RTGs will likely run out entire sometime in the next 5-10 years, ending the missions.

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On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

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  • Gealon

    Hmmmm. I have done extensive reading on Voyager and I don’t recall anything about a power reserve. Any battery technology of the time, even Nickel Hydrogen batteries, would have perished long before now. I suspect that this reserve is a reserve in software only, allowing the engineers of today, to violate a safety margin put in by the original designers. I don’t want to cast a cloud of doom, but I certainly wouldn’t be fooling around with such a safety margin, especially on a spacecraft that has only one power supply… And upon actually reading the article, mid way through typing up my thoughts, it confirms right away what I suspected. I still wouldn’t be fooling around with the spacecraft’s safety settings just to get another year out of any single instrument. I would rather get ten years more science out of four instruments then two years of science out of five, and end up killing the spacecraft because I messed with the power supply. But I treat my own machinery very conservatively, I guess other engineers are more slipshod with theirs. I hope for the best though. If memory serves, both voyagers are due to run out of fuel before their power supplies completely die, so with luck, they will expend their fuel before the RTG’s can no longer power any of the instruments.

  • Lee S

    Hi Gealon,

    A question, do the voyagers actually have any fuel left, and if so, for what?

    I can’t imagine they need anything for course change…. to keep alignment with the deep space network?

    This is fascinating stuff, and any links would be appreciated!

    The Jupiter flyby inspired my love of space as a young lad, and Saturn, even more so! ( I collect national geographic space editions, and the voyager editions are extra special… It’s somehow so much better seeing those fantastic images in glossy colour than in pixels on a screen!)

  • Gealon

    Hello Lee;

    The Voyager spacecraft both have a large, spherical tank of Hydrazine at their center, surrounded by the equipment bus. The fuel was used for minor course adjustments during the interplanetary part of the mission and for orienting the spacecraft. Now it is used solely for orienting the spacecraft. Every once in a while the vehicles have to perform a roll so that the magnetometers can be re-calibrated, that’s the single largest use of fuel now, if memory serves. Also if memory serves, they have enough fuel to last into the 2030’s. After that they won’t be able to keep their antennas pointed at Earth.

    I would have to dig up some of the old research I did years ago in order to provide links. There was a great website that provided weekly reports of both Voyagers power and fuel status. I know the JPL website has some good stuff too. Like this one, that I totally did just dig up while typing:

    Robert, go ahead and check the link out first, if you are filtering anything.

  • Jay

    It is not an additional power supply, but power management. There are few items they have turned off, one article mentioned some heaters, and they are still within their supply vs. demand numbers.

  • Chris

    So Voyager 1 and 2 were launched in 1977. When is the next program going to be started?
    Will it have launches of more devices to travel to more locations both along the protoplanetary disk and to offset vectors from the disc.
    Will it have better instrumentation to provide better measurements of the interstellar medium?
    Will each of these last longer? Will they have better communications equipment? Will they be re-programmable to allow for mission alteration?
    Will it be part of a continuing program of vessels to continuously reach further out from our solar system?

    Will all the money just go into a black hole like SLS?

  • Edward

    I used to work in a space sciences laboratory, where we built scientific instruments for spacecraft. The scientists made the decisions about the science, and we engineers made it happen. The scientists were in charge during the mission. and we engineers were assigned to other projects. For Voyager, the principal investigator (lead scientist) most likely met with his other project scientists to set the priorities on what they wanted to do and to study, what to turn off and what to leave or turn on. This was the scientists’ choice, not the engineers. The engineers make it happen, not make the priority.

  • Jeff Wright

    Edward, I want to run this by you and see if you agree. Apollo tech too clunky-new chips too sensitive…but late-70’s tech hit the sweet spot.

  • Tom

    Jeff, the computers on V1 & V2, the two oldest continuously operating CPUs known to man, were remnants of the Apollo program. As for the instruments, they certainly benefitted from Apollo-era lessons learned.


  • Edward

    Jeff Wright,
    I’m not sure what you mean.

    Apollo tech was used because the engineers understood it and it worked for their purposes. If it works, use it, and don’t fix it if it isn’t broken. Airplanes with internal combustion engines still use magnetos because they work reliably.

    If the late 1970s tech was the sweet spot, then why is the tech still being improved?

    For half a century, rockets were improved in order to take more mass to orbit. These days, they are being improved in order to take mass to orbit more economically. The economics is currently the broken part of rocketry, and this is being fixed. The economic Falcon 9 is currently the most frequently flown rocket, flying almost twice per week (around once every 4-1/2 days).

  • wayne

    ST: TOS se02ep13
    >Spock will handle the power…

  • Lee S

    @Gealon, thank you! Every day I learn something is a good day. Today is a good day! :-)

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