back to article Clever girl: SpaceX's Mars-bound Raptor engine looks like it works just fine

Over the past week in space, SpaceX pressed go on the first flight Raptor, the Lucy mission inched closer, and the ISS crew battled with some dodgy plumbing. SpaceX fires up the first flight engine for Starship Ol' Musky was justifiably chuffed with his band of boffins as a team of engineers fired up the first flight Raptor. …

  1. Anonymous Coward
    Anonymous Coward

    Green

    It's burning a bit of copper when it gets up to power. Good for a first test though, and that's what testing and tuning is all about.

    1. ArrZarr Silver badge

      Re: Green

      Could the rocket scientists in the viewrship explain what you do to fix it? I assume that the main change you can make at this stage is based upon the alloy of the bell rather than modifying positions of anything.

      1. Persona Bronze badge

        Re: Green

        As a first step you tune the LOX/CH3 mixture ratios, pressures and indirectly the temperatures on both of the pre-burners and the combustion chamber.

      2. Anonymous Coward
        Anonymous Coward

        Re: Green

        "Could the rocket scientists in the viewership explain what you do to fix it?"

        Hard to say unless you know what the problem is. The Haynes manual for the Saturn V rocket explains that Rocketdyne's J2 hydrogen fuelled engines burnt their solid copper injector plates in the early versions. The fix was to make the injector plates out of sintered metal, so as to make them porous. That way, the entire injector plate could be cooled by gaseous hydrogen seeping through it: it says here that 3.5% of the hydrogen fuel entered the combustion chamber that way.

        The fix had previously been discovered by Pratt and Whitney in developing its RL-10 engine, but Rocketdyne didn't want to know due to "not invented here" syndrome. NASA did the required arm-twisting.

        But I suspect that isn't the problem in this case. The green tinge to the flame doesn't look "spectacular" as described in the Haynes Saturn V book, and in any case I'm sure Musk's rocket engineers are more than a little bit better informed about rocket engines than me so wouldn't have repeated a mistake from the 1960s.

        The effect could indeed be a camera artefact, or maybe there's a little bit of rough copper burning off somewhere inside? If there is a real problem, I'd be willing to bet a decent sum of money that the engineers will be able to fix it without much bother. I do wonder if it's a problem with the spark plugs - even ordinary road vehicle piston engines can melt spark plugs if they're the wrong sort, or if the fuel/air ratio's lean (i.e., low on fuel). Certainly the suggestion from "Persona" that adjusting the fuel/oxidiser ratio is a good place to start is a definite maybe.

        I very much doubt that it's a problem with the nozzle (bell, whatever you want to call it): SpaceX's early engines were ablatively cooled, but they've been actively cooled using fuel for some years now and that's a very mature technology which has been in use since the 1930s.

        1. kurios

          Re: Green

          SpaceX' vacuum engines (second stage) are radiation cooled. No ablative, no regenerative circulating coolant. Just radiation to the 4°K background.

      3. kurios

        Re: Green

        It of course depends on the root cause.

        If copper is vaporizing, you'd look to cool it better as one fix.

        a) Make the copper liner *thinner*, which would reduce thermal resistance between the hot liner surface and embedded regenerative cooling channels.

        b) Redesign the size/shape/placement of the cooling channels for the same reason as in a).

        c) Maybe it's cavitation bubbles in the coolant channels inhibiting heat transfer, in which case, modeling and redesign to eliminate cavitation would be the thing.

        1. Gustavo Fring

          Re: Green

          scott manley on YT ?? says its to prevent oxidation damage to the bell (I think).

          see also curious droid

    2. Sorry that handle is already taken. Silver badge

      Re: Green

      If the copper is being exposed in that short a time then yes, they have a problem.

      My initial thought was residual starter fluid.

      1. Vulch

        Re: Green

        The flight engines are supposed to be using spark ignition rather than the TEA-TEB mix used on the Merlins. Tests of the prototype Raptors have used TEA-TEB though, so the spark igniton may still be coming Soon (TM).

        1. rg287 Silver badge

          Re: Green

          The flight engines are supposed to be using spark ignition rather than the TEA-TEB mix used on the Merlins. Tests of the prototype Raptors have used TEA-TEB though, so the spark igniton may still be coming Soon (TM).

          I believe Musk indicated that this test was using spark ignition - which is why he narrowed the green to either camera saturation or burning copper, not TEA-TEB.

          This is more or less a flight-spec engine (albeit this specific one may never fly if they continue to tweak the design, or may only be used for "hopper" tests), as opposed to the previous Raptor tests which were using scaled-down test articles and did indeed use hypergolics for ignition.

          What's in that rig is a full-scale Raptor in (more or less) its final form. Which is awesome.

      2. imanidiot Silver badge

        Re: Green

        If I understand correctly the copper is actually the direct lining of the combustion chamber and throat, so what is happening is probably a bit of engine rich combustion.

        What can be done to fix it can involve many things. Among them: Changing fuel/oxidizer mixture ratios, changing the flow balance in the wall to improve cooling in the hotspots, altering wall thickness (either thinner or thicker, depending on what is happening), changing the injector pattern or slightly altering the flow in certain spots.

        There is no TEA/TEB being used in the full size Raptor, so it's definitely not the starter system causing the tinge. On top of that the flame starts out yellow and then turns green. It'd be the other way around if it was ignition fluid.

        I also doubt it's the camera as different angles show the same discoloration, and I'd find it strange if several cameras with different lenses, at different angles all showed exactly the same sensor saturation issue.

    3. Hurn

      Re: Green

      Another thought would be this: rather than "saturation," many (video) cameras can "see" Infra Red, but report the color as green. Since the flame is hot, there's a lot of IR being released.

      Example: point a hand held, IR LED remote control at a video camera lens and push the remote button. While the Mk I Mod 0 eyeball won't see anything, the camera will see the LED(s) light up green.

      Presumably, even with an IR filter covering the lens, which would be a sensible precaution given the heat, some hot things may still show green.

      1. Sorry that handle is already taken. Silver badge

        Re: Green

        Another thought would be this: rather than "saturation," many (video) cameras can "see" Infra Red, but report the color as green.

        IR is passed by the green filters and blocked by the red ones?

        1. Andy The Hat Silver badge

          Re: Green

          I believe what he's saying is that the green sensors are more sensitive to the infra red leaking onto the sensor than the red ones ... Seems odd but what is suggested works - try it.

  2. Ali Dodd
    Alien

    Are Nasa taking the piss?

    "Lucy is a Discovery class mission led by principal investigator Harold "Hal" Levison"

    DISCOVERY-class mission led by HAL?

    Nothing inspired by 2001 then at all.

    1. Aladdin Sane Silver badge

      Re: Are Nasa taking the piss?

      Nominative determinism at its finest.

    2. Alister Silver badge

      Re: Are Nasa taking the piss?

      I used to have a Land Rover Discovery, and part of it's registration were the letters HAL, I wish I'd kept that plate now...

      1. JJKing Silver badge
        Facepalm

        Re: Are Nasa taking the piss?

        I'm sorry but I can't let you can't do that Alister.

  3. Alister Silver badge

    Clever Girl

    Nice Jurassic Park reference there...

    1. Anonymous Coward
      Meh

      Re: Clever Girl

      Whenever I see that line, I try to visualize (in the real world) a large meat-eating predator pausing during its final lunge to gloat. As I say, I try. Doesn't work tho. Not even human predators do that, except for the brain damaged ones, and wannabe trope villains.

  4. Alistair Silver badge
    Windows

    Trojans

    I can't recall if it was the leading trojans or the trailing trojans that were causing all the problems in Mote.

    I'm sure we'll figure that all out when Lucy gets there.....

    Speaking of which, I need to make more coffee.

    1. AdamT

      Re: Trojans

      If the coffee tastes suspiciously good, then you may have a problem ...

  5. Anonymous Coward
    Anonymous Coward

    Bill, we need to relight the engine. Pass the kale.

    As Musk explains, the engine uses "Gaseous CH4/O2 & heavy duty spark plugs. Basically, a [Dashing Away Emoji] of insane power" to ignite the igniter torches.

    Clever design for a crewed vehicle. Don't need to carry much of the stuff if you've got some methane-producing bio reactors already on board.

    1. phuzz Silver badge
      Happy

      Re: Bill, we need to relight the engine. Pass the kale.

      "methane-producing bio reactor"

      Flatterer, that's the nicest thing anyone's called me all week.

    2. Anonymous Coward
      Unhappy

      Re: Bill, we need to relight the engine. Pass the kale.

      > "Don't need to carry much of the stuff if you've got some methane-producing bio reactors already on board."

      Won't work. The propellant mass would have to be beans or maybe brussels sprouts, and the sulphur in the beans is dead weight, dramatically reducing efficiency.

    3. quxinot Silver badge

      Re: Bill, we need to relight the engine. Pass the kale.

      The bigger question is which is better/worse to have onboard: Those who produce hot air vs those who produce methane....

  6. Milton Silver badge

    Green

    Can't vouch for the footage myself but I note that elsewhere someone stated that the entire image had "greened"—i.e not just the exhaust flame but some shiny stuff elsewhere in the frame, unlit by the flame, had also changed hue. If that is correct, we're over-analysing things.

    The design and engineering teams deserve some serious kudos, whatever: a test that ends with an intact engine is a good result. In these days of general pessimism about the state of the world (and the abject f**king w**kers that run things, not to be too rude) it is heartening to see so many really serious-minded and practical ventures in spaceflight. I'm a child of the late 50s, so of course I still believe that humanity's real future, and assurance of longevity as a species, is Out There. If I could see a Moon- or Marsbase in my lifetime, I'd consider myself very lucky.

    (And if Richard Branson's dumb stunt in the desert doesn't kill him, he should consider himself very lucky ... Spaceflight, it ain't.)

  7. This post has been deleted by a moderator

  8. Spherical Cow Bronze badge

    Ford Prefect was right

    and the ISS crew are discovering how useful a towel can be in space.

  9. Andy The Hat Silver badge

    Urine Transport System

    As this is presumably the input section of the Urine Processor Assembly, would the UTS be commonly referred on Earth as a "pipe"?

  10. A Nonny Moose
    WTF?

    Blue Origin first?

    "Blue Origin beat SpaceX to the fiery-end-down-landing-first crown"

    Are you sure about that El Reg? Weren't SpaceX doing fiery-end-down-landings with Grasshopper long before Bezos launched his rocket-powered dildo?

    1. Andy The Hat Silver badge

      Re: Blue Origin first?

      I thought Blue Origin had "hops" in 2006, Grasshopper wasn't given launch permits for that until 2011 ...?

  11. This post has been deleted by its author

  12. Anonymous Coward
    Anonymous Coward

    Re. Kale

    Re. Kale

    Why does it cause such severe gastrointestinal symptoms (to wit: Stinky rancid gas) ?

    Never had anything like it.

    It was in the reduced pile but I can't see any reason for such an extreme reaction.

    Not intolerance per se as had a similar reaction to hot curry with lentils.

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