Aug 302014
 

Shazam:

[youtube nyveRd36FR8]

Tested at NASA-MSFC, a LOX/LH2 rocket of 20,000 lbs thrust with a 3d printed injector head.

Using traditional manufacturing methods, 163 individual parts would be made and then assembled. But with 3-D printing technology, only two parts were required, saving time and money and allowing engineers to build parts that enhance rocket engine performance and are less prone to failure.

I can see pluses and minuses here. The obvious plus is that a printed part can be hideously complex, geometrically, and thus performance can be high and weight very low. But the parts count thing *might* work against it. Especially if the goal is a reusable engine. Because if there’s any damage… well, ya gotta toss the whole thing.

Years ago I designed and tested a series of increasingly capable liquid rocket engines that used off the shelf spray nozzles in the injector. Weighed more, sure. But the injector head itself was, eventually remarkably simple to design and machine out of simple aluminum, and the injectors could be simply threaded in and out. Easy.

But had I been able to simply 3d print a regen-cooled nozzle and/or combustion chamber… wow, would that have been handy!

 Posted by at 2:50 am
  • Jon Risque

    Have you ever thought about doing model rockets? Not tiny ones but the big LDRS ones.

    • Anonymous

      Yes. But the ones I want to do would make me unpopular with my neighbors, inspire the attention of the BATFE and put me deep into debt.

  • Jon Risque

    yes, When I lived in Ventura there was a guy who built motors in his garage and used the local city college’s machine shop while in class. He was visited several times by the gubmnet, this was in 1992, I can’t imagine what it’d be like today.

    Still, you could rent a shop and try Kickstarter…you won’t know until you try

    • Anonymous

      I’d build engines rather than motors, given my druthers and a sufficient budget. But the real problem would be testing, not machining. Given that even a small engine would blow up about like a hand grenade if things go wrong, my five acres would be far too small for adequate separation from the civilians. Plus, the launch: the FAA gets involved in such things. Build yourself a small rocket a meter in diameter and ten meters long, it could certainly get itself into space (if not orbit); but the FAA would take considerable interest. As would NORAD.

  • se jones

    If I were a multi-billionaire, I’d build a horizontal take off & landing SSTO using a SCAAT (Supersonic Core Air-Augmented Thrusting) engine. With no turbomachinery or fancy pre-coolers, you get free supplementary oxidizer from zero to mach 8-10, then pure rocket without the complex/heavy switching propulsion systems.
    AM (Additive Manufacturing) finally makes this doable. This engine is super simple in principle, it’s just a exercise in very complex plumbing.
    I’d be very surprised and disappointed if the SCAAT isn’t being built & tested in the black program office.

    For SSTO to orbit you’d need aerial “refueling” (the oxidizer) and swing wings (like Triamese) and all composite airframe.
    Or…if SSTO is too ambitious, a vertical take off stage one may be the hot ticket.

    • Anonymous

      Well, that’s certainly going about space launch the hard way. But if you’e a bagrillionaire spending your own money… go for it. You might generate some interesting and useful technologies before the larger program collapses under the many layers of unnecessary technological complexity.

      • se jones

        >>unnecessary technological complexity
        Perhaps.

        The engine itself is the essence of engineering elegance and simplicity and aerial refueling is more-or-less routine (though always dangerous fer sure) but the devil is in the other details.
        Integrating the engine into the airframe so the engine is shielded from the entry plasma is a complication, and of course the mass and complexity of the wing pivots is a downside. A lifting body or the North American strait wing design would be preferable if low speed performance was good enough for the refueling (re-oxidizer) opps.
        Despite the (I predict) success of SpaceX’s reusability scheme, people will continue to push for aircraft-like, single stage, horizontal takeoff and landing.

        • Anonymous

          > The engine itself is the essence of engineering elegance and simplicity and aerial refueling is more-or-less routine

          Neither seem simpler than simply going straight up under rocket power.

          > Integrating the engine into the airframe so the engine is shielded from the entry plasma is a complication

          As it making the airframe anything other than a wingless cylinder.

          > people will continue to push for aircraft-like, single stage, horizontal takeoff and landing

          Sure, just as people continue to push for VTOL supersonic transports. And while such things are certainly possible, that’s doing things the hard way. Interestingly, airbreathing boosters are the *slow* way to space compared to simple rockets. While that doesn’t make a whole lot of difference as far as cargo transport to space goes, it *does* play havoc with the airframe. Rocket go straight up and get out of the atmosphere ASAP, and do most of their hard acceleration and high speed above the sensible atmosphere. But airbreathers *have* to plow throw the air at ridiculously fast speeds. This has a tendency to turn most structural materials into garbage.

          • se jones

            Yes of course – but: straight up under rocket power, SSTO is, as you well know, really really not likely because of the outrageous mass fraction required.
            There is a legitimate desire for winged entry and landing for human passengers, for obvious reasons I think.
            My desire is to make the wings more than just dead weight during ascent.
            Yes of course, most of your LEO energy is kinetic and is gained above sensible atmosphere.
            In a nutshell: you have to have rockets to accelerate to Mach 25.
            With SCAAT engines, you’re basically just putting your RL-10 sized engines in a long metal tube with a translating inlet spike, annular fuel injector and variable area exhaust nozzle.

            The SCAAT engine gives you an airbreathing engine at zero velocity by using the rocket engines in place of heavy and complex turbomachinery.

            For runway takeoff and flight up to the tanker, the rockets are throttled down and run rich as you get most of the thrust from the air augmentation.
            I don’t think an engine like this has ever been made, using the venturi effect of a rocket to suck air into an annular combustor. It’s hard to wrap your head around it at first.

            By using aerodynamic lift, you can get off the ground without the full fury of all the rocket engines which has advantages for ground opps.
            Then, by having aerodynamic lift, you can takeoff with less than a full oxidizer load (which lowers the mass of landing gear, wing boxes etc.) and fly up to a tanker to take on oxidizer.

            Once topped-off, you begin the race to orbit. The mix ratio of the RL-10s and the air-augmenters is constantly adjusted to optimize performance. As the vehicle goes supersonic the inlet spikes translate to optimize ram pressure and from mach 1 to ~mach 5 the the RL-10s are throttled to almost idle as most of the thrust is ramjet. Since elaborate cooling schemes are to be avoided, at ~ mach 5 the inlet spikes translate to closed and the RL-10s take over completely for acceleration to orbit.

            You start serous accelerating on pure rocket power, up past the knee of the curve, with nearly full oxidizer tanks and from mach 5 up in the stratosphere, which is nice. Yes, you are lugging along wings and landing gear as dead weight, but the assumption is you want those anyway, so put them to work on early ascent.

            The mass of the SCAAT system is minimal, remember – no turbomachinery, just some metal tubes and 3D printed hollow struts, fuel injectors and inlet spike.

            Complex. Hell yes. But then, so is Naval aviation in general which goes on every day, rain or shine (yes for lots $$$$)

            Too complex? For now – yes. But eventually when LEO zero g hotels are a thriving business, alternate ways of up-going are sure to spring up.

          • Christopher James Huff

            LOX is cheap and dense, oxidizer costs are a minuscule fraction of launch costs. You are adding to the most expensive parts of space launch, operations and the cost and complexity of the vehicle, to slightly reduce the least expensive part. This is not going to reduce launch costs.

            The desire for horizontal takeoff and landing is driven by cargo cult imitation rather than analysis of the problem. Actually deriving a benefit from air breathing requires unrealistically good hypersonic L/D ratios or thrust levels that can’t be achieved with air breathing.

          • se jones

            >>oxidizer costs are a minuscule fraction

            That’s a straw man, this has nothing to do with the actual cost of fluid and I never said so.

            >>analysis of the problem

            The problem is one we don’t have yet, but we all hope we will have someday. The problem of SO much passenger traffic to LEO that an alternative to cramming a handful of people in a capsule on top of a rocket is desired.

            >>unrealistically good hypersonic L/D >>thrust levels that can’t be achieved

            You completely miss the point. This is not NASP, the SCAAT engine air-augmentation signs-off at high supersonic, the majority of the acceleration to orbit uses the methane fueled RL-10 derived engines.

            Really, this is an attempt to substitute a first stage with air-augmentation and aerial oxidizer tanking so you can have a SSTO aerospace plane.

            The mistakes people make when commenting on this concept are: I’m dissing SpaceX and claiming there’s a better way. Not True, at this point in the game, SpaceX’s solution is perfect. But mission models and requirements will evolve as the traffic to LEO increases and technology improves.

            >>cargo cult? So was the development of the current generation of regional jets driven by a cargo cult? ATR42s, Dash 7s & 8s get better fuel mileage, but the flying public hates propellers, so now turboprop regional airlines are endangered species. The paying public’s taste matters.

          • Anonymous

            > Really, this is an attempt to substitute a first stage with
            air-augmentation and aerial oxidizer tanking so you can have a SSTO
            aerospace plane.

            So do it simpler and build something like Black Horse or Pathfinder.

          • se jones

            Well of course, the idea started out from Black Horse.
            But Black Horse is just a reusable, suborbital first stage to pitch an upper stage payload.
            I’ve always been fascinated with the SCAAT engine, and when I saw the progress in AM (additive manufacturing for those in Rio Linda) engine powerhead components, making the complex SCAAT parts now seems within reach.
            Black House takes off with jet engines or rocket engines (or a combination of both). With SCAAT you have the “combination” WITHOUT the heavy and complex turbomachinery of jet engines.
            The SCAAT engine is dirt simple, it just looks complex.
            I’m hoping to buy enough performance with SCAAT

  • Peter Hanely

    “But the parts count thing *might* work against it. Especially if the
    goal is a reusable engine. Because if there’s any damage… well, ya gotta
    toss the whole thing.”
    Which presumes the single piece part isn’t far more reliable than the complex assembly. Every last junction where parts are fitted together is a potential point of failure. Not that an injector face strikes me as a common point of failure if designed well.

  • Randino2001

    Didn’t Elon Musk at SpaceX say they were using this exact manufacturing technique for their Dragon module thrusters? Months ago?