back to article Plucky Playmonaut bails out of smoking Vulture 2

Our plucky Playmonaut has decided to take a long weekend off after a servo meltdown during a ground avionics test of our Vulture 2 spaceplane prompted a sharpish exit from the vehicle. Here's the scene immediately after the scare, as emergency crews rushed in to cordon off the area, douse the offending kit with foam and gave …

COMMENTS

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  1. AndrueC Silver badge
    Joke

    The server...controls one of the canards

    I can 'ardly believe it went up in smoke.

    1. I ain't Spartacus Gold badge
      Happy

      Uh oh! The puns are coming any second now. Duck!

      [I, of course, would never stoop so low.]

      1. Vulch
        Coat

        At least it's not a serious Mallard'y.

        It's a nice day, I won't need my coat...

        1. Michael H.F. Wilkinson Silver badge
          Coat

          Luckily the story is supported by evidence

          otherwise it would be seen as a canard about a canard

          OK, OK, I'm off!

          1. Anonymous Coward
            Anonymous Coward

            Re: Luckily the story is supported by evidence

            >controls one of the canards and its horn can just be seen here poking out

            Shurley that should be peking out

            1. Lester Haines (Written by Reg staff) Gold badge

              Re: Re: Luckily the story is supported by evidence

              Right, I'm getting really ducked off with this puntastic tomfoolery.

              1. kmac499

                Re: Luckily the story is supported by evidence

                Judging by the amout foam used... Plucky Playmonaut had a close shave....

              2. AndrueC Silver badge
                Joke

                Re: Luckily the story is supported by evidence

                Right, I'm getting really ducked off with this puntastic tomfoolery.

                It's Friday. We're all a bit quackers :)

                1. Adam Foxton
                  Coat

                  Re: Luckily the story is supported by evidence

                  Water fowl load of puns those are!

                  1. M Gale

                    Re: Luckily the story is supported by evidence

                    What, you don't like bird jokes?

                    Well this is hawkward.

  2. Benjol

    Sorry if someone already noticed, but

    I thought that name rang a bell. It's he of git 'fame' (http://en.wikipedia.org/wiki/Git_%28software%29).

  3. Vinyl-Junkie
    Coat

    Playmonaut down!

    1. graeme leggett Silver badge
      Coat

      Is there a relief crewman in case he doesn't turn up on the day?

      [Personally speaking, given the size of the Playmonaut, you could get three classic spaceman Lego minifigs in the same space. Mines the one with plans for 928 Space Cruiser in the pocket]

      1. Lester Haines (Written by Reg staff) Gold badge

        Lego? You speak in jest, surely?

        1. I ain't Spartacus Gold badge
          Happy

          After bricking it, the Playmonaut would be off for a few beers, and then to get his legover with some young lady with nice dimples, at the bar.*

          A few technicolour yawns later. Then his hangover recovery would be some nice Danish bacon.

          I think I'm out of Lego puns at this point.

          * Why didn't you include a reconstruction of this bit - it could have been like 'The Right Stuff'? One of my favourite films / books.

          1. Irony Deficient

            a reconstruction of this bit

            I ain’t Spartacus, that asterisked bit was perceived and foretold (but not reconstructed) here.

      2. John Brown (no body) Silver badge
        Flame

        " Lego minifigs"

        BURN THE HERETIC!!!!

  4. Ed 13

    Which bit failed?

    Have you dissected the servo yet, I presume it was the motor itself that let out the magic smoke?

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: Which bit failed?

      Yeah, the motor's burnt out. Pain the the backside, but at least we caught a potentially terminal problem while the Vulture's on the ground.

      1. Neil Hawkins

        Re: Which bit failed?

        That's what ground testing is all about! ... so the rumour goes....

        1. I ain't Spartacus Gold badge

          Re: Which bit failed?

          Testing? Testing!

          Oi Mods! Over here! Someone's swearing over here. Ummmm. You should tell them off...

      2. Ed 13

        Re: Which bit failed?

        Also the heat dissipation in thinner air is lower (that's how some vacuum gauges work), so it would have got hotter faster at high altitude.

        The problem with a zener is that it'll dissipate heat too in a over voltage situation, and excess heat is not something you want in Vulture 2 at altitude. The Lithium cells can deliver a lot of current in to something if it fails (as your late and lamented servo appears to have discovered).

        Are you logging the current consumption from the APM?

        1. Lester Haines (Written by Reg staff) Gold badge

          Re: Re: Which bit failed?

          Once I've got the canards rigged, we be firing everything up and doing a bit of logging, to see what's what with all elements of the system.

          1. Ed 13
            Joke

            Re: Which bit failed?

            "Once I've got the canards rigged, we be firing everything up..."

            Given what's just happened, isn't that a poor choice of words?

        2. Return To Sender

          Re: Which bit failed?

          Ref the Zener - yup, that's the catch; they clamp the voltage, but the excess energy's got to go somewhere, and that's heat. You could end up with the Zener burning out, closely followed by the motor. Might want to consider some sort of switching regulator; not as cheap as the Zener, but not wildly expensive either - and it's mission-critical after all. Not sure what oomph you need, but a TI LM2569 for example would support 3A at 5v for around a tenner with all the bits 'n bobs. wouldn't need a lot of space either.

  5. Vladimir Plouzhnikov

    Fire on the pad?

    This is beginning to look like a real space program more and more...

    1. cookieMonster Silver badge
      Pint

      Re: Fire on the pad?

      this IS a real space program

  6. Chris G

    Playmonaut

    Wot's his name and why doesn't he have an ejector seat?

    1. ukgnome

      Re: Playmonaut

      His name is Plucky - although that might be just his call sign.

      I believe they ejected his ejector seat to make for a lighter load.

  7. Boris the Cockroach Silver badge
    Mushroom

    Why are you

    still using playmonauts?

    Swap out the pilot to Jeb from Kerbal space program and he NEVER bails out regardless of the disaster about to befall him

    1. M Gale

      Re: Why are you

      He's also immortal, and ready to jump back into the pod even before you've finished scraping his remains out of the smouldering crater left by the last pod. I don't feel that our Playmonaut is quite so psychotically happy about a hypersonic splashdown.

      Maybe we should set the Playmonaut's BadS flag to true.

  8. Gordon 10
    Boffin

    Weight

    Any danger Lohan has been overeating as well as overheating?

    Have your boffins done the lift calculations?

  9. imanidiot Silver badge

    Overstimulation

    Was the servo hooked up to the control board and actively being "instructed"? Perhaps the PID algorithms need some tinkering and are overstimulating the servo with very small adjustments. (I'd suggest putting in an averaging period buffer on the output). This could quickly overheat the motor since it's constantly getting instructed to move one way, then the other. This can be heard as (possibly quite soft) buzzing or rattling coming from the servo.

  10. Don Jefe

    Thou Shalt Not

    Replace control horns without cycling the system and zeroing out any trim with nothing attached to the servo. Failure to do so virtually guarantees a mechanical binding situation with predictable results.

    Smoking a servo motor from with a random voltage spike is really, really unlikely. Overloading a servo by getting a linkage in a mechanical bind is an everyday occurance. You should be able to tell what happened by looking inside the toasted servo.

    Hubris of the engineering team and ground crew has killed many test pilots. There's no need for that here :)

  11. Anonymous Coward
    Coat

    I assume the Playmonaut was listening to Drake on his iPod?

    Ok, ok, I'm leaving!

  12. Kevin McMurtrie Silver badge
    Mushroom

    Hot Zeners

    Zener diodes by themselves are terrible shunt regulators so you'd be wasting lots of power with very little regulation. Zener diodes have more of a precision change in resistance than the perfect shunting that people imagine. One would probably incinerate in thin air. At low voltages, forward driven power LEDs will do much better at shunting. Three pin regulator ICs are even better.

    What you might actually need is good old aluminum electrolytic capacitors. Their combination of very high capacity, low resistance, and high AC losses make them perfect for smoothing out a glitchy power rail. This not only protects you from high voltage surges, but also low voltage surges that can cause damaging reverse currents from on-board capacitors. Look for the higher priced compact capacitors to keep the weight down.

    1. Stoneshop
      Boffin

      Re: Hot Zeners

      Quite. Although in this case it wouldn't really need to regulate, just spring in to action when the voltage on the servo rail would be spiking, so a nominal zener voltage anything from a few 100mV to maybe one volt over the nominal servo feed voltage. But a TVS (Transient Voltage Suppressor) is actually the part you want there.

      But I doubt that a brief voltage spike can kill a servo motor. You need a fair bit of excess voltage over several seconds to be problematic, and at that point a zener will have already lost its magic smoke, or its bonds with the circuit (I've had that happen: underspecced MOSFETs in a heating controller would themselves get so hot that they would melt the solder on their legs and drop out of the circuit board). I'm with Don Jefe that probably something was restricting the servo travel.

      Capacitors are a better solution than that zener anyway, a couple of low-esr electrolytics (1000..2200uF) with a 100nF ceramic parallel each.

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