back to article NASA's gamma-ray-burst alert satellite put into safe mode after suspected reaction wheel failure

NASA has put its orbiting Neil Gehrels Swift Observatory into safe mode due to a suspected faulty reaction wheel, the first time this type of failure has occurred in its 17 years of operation. NASA this week confirmed Swift was powered down on January 18. A team of scientists and engineers from Pennsylvania State University …

  1. HildyJ Silver badge
    Pint

    17 years

    NASA designs and builds to last. Swift has been providing data without a hitch since 2004.

    I have no doubt that if the reaction wheel cannot be restarted the boffins, many of whom hadn't made it to university when it was launched, will figure out a way to make do with five. A pint for the old boffins and another for the new ones.

    My car's parts should last so long

    1. Spherical Cow

      Re: 17 years

      "My car's parts should last so long"

      Many parts in my car are still going strong after 62 years. However, some are not and I've been able to replace them easily because the car is in my garage and not in orbit (or worse still on its way to L2). The thing about spacecraft is that even a single bad part can spell disaster, whereas car parts don't need to be so robust.

    2. Joe W Silver badge
      Pint

      Re: 17 years

      I totally can echo that sentiment (the car parts) - however considering the economy involved we are out of luck. People[*] want cheap and buy cheap, and you get what you pay for.[0]

      Great that scientific instruments are not built that way!

      --> I toast the engineers involved in building the equipment!

      [*] most, but admittedly not all, and some of us actually think long and hard about a purchase, but in the end there is an intersection between the lines of "costs this much to manufacture for that reliability" and "I'm willing to pay this much over the projected lifetime - or in total". That sweet spot is different for all of us, but I am pretty certain that the probability distribution can be modelled as bivariate normal (cost, reliability), as a decent approximation - it is so far from the origin that the needed cut-off at zero cost can be safely ignored[+]

      [+] this shows that I am no mathematician

      [0] Edited to add: and Sperical Cow (who judging from the handle might be a physicist?) is totally right about the ease of swapping out parts. You are willing to spend more and overengineer more when you cannot just swap out parts, because it is inconvenient or impossible.

    3. werdsmith Silver badge

      Re: 17 years

      I don’t know the arrangement for the axis control in this bird, but three wheels are required for three axis positioning, and a fourth for redundancy is enough normally. Maybe a 1500 kg mass lump needs a bit more torquing to respond quickly to detected events.

      1. ClockworkOwl
        Go

        Re: 17 years

        It's got no thrusters, it needs pairs of wheels to pass angular momentum from one to another, it can't unload excess momentum using linear thrust...

        1. werdsmith Silver badge

          Re: 17 years

          Allowing the angular momentum to unwind by allowing the spacecraft to controlled rotate on any axis winding the wheels up in the other direction, if the thing doesn't need constant attitude anyway.

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