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Carmack's Throatless Rocket Engine 351

Posted by CmdrTaco
from the this-is-just-strange dept.
Baldrson writes "John Carmack is working a potentially disruptive technology: A throatless rocket engine. Its made from plain aluminum pipes with few machined fittings. Carmack says: "The great thing about these engines is that it only takes me two nights to machine the parts, so we can test two engines a week if necessary." It scales too: "If this line of tube engine development works out, we can make a 5,000 lbf engine with very little more effort than the test engine." This is what makes disruptive technology development work: Cheap, fast turnaround on on redesign producing technologies that scale. If this works, the NASCAR guys may really start entering space competitions like the X-Cup."
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Carmack's Throatless Rocket Engine

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  • pipedream (Score:5, Funny)

    by Anonymous Coward on Sunday August 07, 2005 @10:59AM (#13263756)
    the Pipedream finally becomes reality.
  • by Thakandar2 (260848) on Sunday August 07, 2005 @11:00AM (#13263762)
    I mean, why have a genius like Carmack working on shooting rockets into space, when what the world really needs is a better personal rocket launcher... for shooting rockets into other people.
  • by Anonymous Coward on Sunday August 07, 2005 @11:00AM (#13263763)
    In an effort to propel himself high enough to reach the Quad Damage, John Carmack fragged himself with his own rocket launcher. He will be remembered by a rabid community of gamers. We will all miss you John.
  • by Skyshadow (508) * on Sunday August 07, 2005 @11:04AM (#13263793) Homepage
    I'm getting the impression that Armadillo might never get anywhere further than a few cool but short flight tests.

    Not that I'm one to criticize (large liquid-prop rockets built by Skyshadow: 0), but everytime they get an engine together and start encountering difficulties it seems like they scrap it and just go to another design. Assuming that rockets are anything like the mechanical things that I understand (cars), this just isn't how you can go about these things -- you've got to settle on a promising, well thought-out design and then dedicate your efforts towards ironing out the kinks or you'll perpetually be just past "go".

    Anyhow, just the impression I get from reading the updates.

    • Were pretty much engines jury rigged on to carriage bodies. That's approximately the state of the art for spacecraft at the moment. To make space travel as accessible as road travel, it has to become cheap.

       
    • by cr_nucleus (518205) on Sunday August 07, 2005 @12:00PM (#13264069)

      I think that what Carmack is trying to do is actually to explore a lot of options in terms of engine design, trying to find out if he can come up with one that is actually symple and efficient.

      Of course, there's absolutely no assurance that he'll actually find one, but that's the the risk of any kind of research.

      The whole point is to actually move away from the existing methods, so he can't possibly use them.

    • Isn't that like Linux/OS development?

      You need the experimentation to find out what is promising in the first place!
    • by Anonymous Coward
      You're thinking like a mechanical engineer working on a tight deadline, not a software engineer playing around in his spare time.

      This is, I think, one of the advantages that Armadillo has. They're refactoring their design as they go, trying to come up with the cleanest and most elegant approach. The only way to do that is to try one thing, see what the problems are, try to improve on it - and repeat. Repeat, repeat, repeat, repeat - and eventually an "ideal" design (based on the general technologies that th
    • by everphilski (877346) on Sunday August 07, 2005 @02:05PM (#13264683) Journal
      The problem was hydrogen peroxide. His first engines were built around the stuff. The way hydrogen peroxide works is you catalyze it - that is run it through a mesh of material that reacts with it to liberate steam and hot oxygen, which you then combust with a fuel. Hydrogen Peroxide is a nasty beast. It's hard to find vendors to sell to you (at rocket grade concentrations, 90-98%), and combustion is tricky. After a lot of experimenting (and he himself will tell you - a lot of valuable data gained; he was able to test at rates higher than using other fuel combos) they gave up on it.

      Now they are using liquid oxygen as an oxidizer. They aren't stalled. They are exploring their options. If you look at NASA they have really only done things one way, the convergent-divergent regeneratively cooled nozzle, using O2 and H2, occasionally kero. He's sticking his neck out trying something new, it just takes awhile with limited funds. He's not stalled now.

      -everphilski-
      • NASA did things based on previous research by Goddard, Von Braun, and others. H2/LOX fueled engines didn't materialize until the Apollo program. Kero/LOX was the status quo for big liquid fueled boosters before that. And it is still used by the Russians. Is your argument that NASA has only done things one way, and hasn't explored other options? What about the Soviet space program, did they steal the design from NASA, or did the also come up with it through research? If alien cultures ever made cars, d
      • If Doom3 would have been better, perhaps he would have more funding.

          Oh wait, there's always Quake4. ;)
  • I read TFA but... (Score:4, Insightful)

    by zr-rifle (677585) <zedr&zedr,com> on Sunday August 07, 2005 @11:10AM (#13263826) Homepage
    since I'm not a rocket scientist, I fail to understand the importance of what John is doing (or has discovered? surely throatless engines aren't an entirely new concept are they?).

    I understand that this *might* impact manufactoring costs, but exactly how is this revolutionary, or going to affect us? Are we going to sport some pocket engines in the future? Are they more environmental friendly? Do they scale well? Will it run Linux?

    Seriously, after reading the story and the article a few times I haven't yet understood half of it.
    • Re:I read TFA but... (Score:5, Informative)

      by Gorobei (127755) on Sunday August 07, 2005 @12:31PM (#13264210)
      It's more what he's doing than what he has discovered (which is nothing.)

      For amateur rocket work, you spend about $1000 to burn $1 worth of propellant. Think about the logistics: site costs, setup costs, safety planning, data acquisition, etc.

      Streamlining the process is where you make big wins: accept a 2% ISP loss, and test 10x more frequently. This is how you gain knowledge fast and avoid expensive dead-ends. A lot of this work is just learning skills -- build, launch, avoid dying, repeat.

      More tech (GPS, computers, digital video) makes the process much easier: John is now doing 1970s era work after starting at a 1950's level a few years ago. There's a good chance that he will be able to reach earth-orbit level within a decade.
      • by dufke (82386) on Sunday August 07, 2005 @01:18PM (#13264457)
        John is now doing 1970s era work after starting at a 1950's level a few years ago.

        Thought: Is ANYONE doing rocketry at a 2000's level today? Most of the recent developments in orbit access (x-prize, china, india) seem have been people 'cathing up' to where the US and USSR where in the 60's or so (not that that lessens the achivements). And NASA's advanced projects tend to make the news mainly when they are cancelled...
        • Re:I read TFA but... (Score:3, Informative)

          by AJWM (19027)
          Is ANYONE doing rocketry at a 2000's level today?

          Nobody is even doing it at a 1990's level. Or even 1980's.

          Shuttle is pretty much 1970's technology, although the SSME (Space Shuttle Main Engine) is about the only part that isn't 1960's technology, at least as far as the launch phase goes. Aerospike SSTO designs were being explored (on paper) in the 1960s, with some limited engine testing in the early 1970s. Some early nuclear engine testing (NERVA, too low thrust for launch) was done in the 1960s, with
        • by iendedi (687301) on Sunday August 07, 2005 @10:06PM (#13266508) Journal
          NASA is a sham, a front, a cover for the real space program. The real U.S. space program exists in military black-projects and that is where 2000s level technology is being developed and used. You think UFOs are alien? Ha!

          Do your own research, but I will present you with the basic idea that ZPE and antigravity are a reality within military black-ops and has been for decades.
    • Re:I read TFA but... (Score:5, Informative)

      by garyrich (30652) on Sunday August 07, 2005 @12:33PM (#13264221) Homepage Journal
      It impacts manufacturing costs, but in an interesting way. If you are NASA or General Dynamics, it would be a little bit cheaper to make, but no big deal. The interesting bit is that you should be able to make a decent nozzle with 1/10th the manufacturing/machining capability. It reduces the costs of entry, probably down to the level of a NASCAR crew's machine shop.

      So, not truly revolutionary, but "disruptive" tech in the sense that it puts the ability to make decent nozzles in the hands of many many more people.
      • So, not truly revolutionary, but "disruptive" tech in the sense that it puts the ability to make decent nozzles in the hands of many many more people.

        Don't tell Dubya...

        The terrorists are sure to use this against us...
    • by stienman (51024) <adavis@u[ ]ics.com ['bas' in gap]> on Sunday August 07, 2005 @01:24PM (#13264494) Homepage Journal
      A problem with the current shuttle fleet is that they were designed to be mass manufactured and maintained. We were supposed to have a *fleet* of space shuttles. The cost of the shuttle would, under the original plan, be very small. We only ended up with a few of them and pretty much every part is custom made. Each shuttle has differences which exacerbate this problem.

      However, it is very efficient in a number of parameters.

      Armadillo Aerospace is attempting to produce a design which is easy to produce by limiting the use of custom parts and specialized work in both manufacture and maintenance. They are trading off a marginal amount of performance for a lot of manufacturability.

      There the analogy ends since the space shuttle and the immediate goal of Armadillo have two completely different purposes.

      The science of engines and propellants has matured, but there are so many combinations (propellant x engine design x vehicle design x etc) that it can be difficult to find exactly the kind of research you are looking for. Further, a lot of it is secret since most of this stuff was done for missile design.

      Some may call this "seat of your pants" engineering, as opposed to design engineering. You try something, improve it until you find the optimum, then redesign it completely and start over. It is non-optimal for time and effort, but is low cost. It is enough to get started with something that works but has low efficiencies. Once one has a working design one can scale it only so far before having to go back to the redesign and test phase. At that point it often makes more sense to hire engineers capable of design engineering so the trial phase is shortened since the design is near optimal on the first try.

      Many startups operate succesfully this way. Many have a mix of the two. Many fail when they invest all their money in engineering design, and then try to get more funding to build a prototype - it's much harder to sell an unproven paper design than it is to sell a working product that has flaws.

      -Adam
      • Fleet?!? (Score:3, Informative)

        There was never suppose to be a fleet of shuttles. They were supposed to have such a fast turnaround that the capital cost of each shuttle would be amortized over zillions of launches. It was originally sold to Congress as having a turnaround of a week. It was never sold as being cheap to mass produce a fleet of them. You wouldn't need a fleet if they had a one week turnaround.
  • before/after (Score:2, Informative)

    by biff-mo (681452)
    Before [armadilloaerospace.com].....


    After [armadilloaerospace.com].
  • by bubbaprog (783125) on Sunday August 07, 2005 @11:15AM (#13263852)
    I think Mr. Carmack has a bit of a Pygmalion complex with Commander Keen. To the heavens!
  • He reports only an ISP only in the low 200s, this is not efficent enought to get to orbit.
    • Yep. The old "good thrust, who cares about Isp" mentality.

      There is a reason pretty much all chemical rocket engines have throats, wonder why he fails to see it.
      • You've got your judgement of Carmack's mentality exactly backwards. From the Armadillo site:

        "A chamber with no contraction ratio at all will lose 20% of its thrust due to pressure losses from accelerating gasses in the straight section, but the Isp loss is only 1.5%."
    • by Viadd (173388) on Sunday August 07, 2005 @11:49AM (#13264021)
      He reports only an ISP only in the low 200s, this is not efficent enought to get to orbit.

      TFA is unavailable due to slashdotting, but low 200's will get you ~5km/s with a 90% mass ratio. It's plenty for sub-orbital work, and useful for the first stage if you're not trying for Single Stage To Orbit.

      The shuttle SRBs have an ISP of 273 seconds.
    • Yes, I'd say his Internet Service Provider is in the low 200s as well.
  • by angrist (787928) on Sunday August 07, 2005 @11:25AM (#13263895)
    From the site ...

    "Too many users... blah blah blah

    Probable cause: http://www.slashdot.org/ [slashdot.org]

    Try again in a few seconds...

    -xian@idsoftware.com"

    That has to be the best 'server down' message I've seen in years
  • But... no throat, no supersonic flow... sooooo much energy being lost there...
    • Re:Throatless? (Score:5, Informative)

      by WolfWithoutAClause (162946) on Sunday August 07, 2005 @12:07PM (#13264109) Homepage
      It's actually a misnomer; provided the chamber pressure is more than 2.7x the atmospheric pressure (which it always will be if you stuff enough propellant in through the injectors) then a throat spontaneously forms near where the nozzle widens out. The throat is defined to be the place in the combustion chamber where the gas goes faster than sound. Normally that would happen at the narrowest point of the nozzle, but in this case it may even move around in the combustion chamber, but it can't leave because the nozzle widening out stops it.
  • by standards (461431) on Sunday August 07, 2005 @11:37AM (#13263957)
    If this line of tube engine development works out, we can make a 5,000 lbf engine with very little more effort than the test engine."

    Interestingly enough, as a kid I made my own alcohol fueled rocket motor, based around a bottle filled with a alcohol/oxygen mix, a small orifice, and an ignition source.

    If thing were the way I'd like them to be, I could have scaled it up to be something like twice the power of the Saturn V rocket. But after the first successful test, I was unable to scale the device.

    Best of luck to John, may he do better than I did.
    • Interestingly enough, as a kid I made my own alcohol fueled rocket motor, based around a bottle filled with a alcohol/oxygen mix, a small orifice, and an ignition source.

      Taking a large swig of 190 proof vodka, putting a lighter up to your mouth, and spitting out the vodka [divineimagination.com] does not count as building your own rocket motor. ;)
  • by simonbp (412489) on Sunday August 07, 2005 @11:47AM (#13264009) Homepage
    This "throatless" engine seems more useful for testing injectors than actually extracting impluse (propulsion). The narrow throat of engine followed by a expanding nozzle allows for the chamber pressure to be high (good) while the exhaust pressure is lower (also good). This site [aol.com] explains much this and in fact says, "If the pressure ratio (and thus expansion ratio) [like Carmak's design] is 1, then F = 0. The only thrust produced by such a nozzle is the pressure thrust, or Ftotal = (Pe-Pa)Ae. Such a nozzle, of course, would have no divergent portion, since A*/Ae=1, and would be a badly designed rocket nozzle!"

    Simon ;)
  • Would someone please be kind enough to copy-n-paste it?
  • The Article (Score:5, Informative)

    by Rhoon (785258) on Sunday August 07, 2005 @12:08PM (#13264111) Homepage
    From Mirror:
    http://www.mirrordot.org/stories/8f5373b24e35f5c45 3edf914cc953eff/index.html [mirrordot.org]

    Armadillo Aerospace News Archive

    >
    Servo regulator, Throatless engines, Hold down test

    Aug 4, 2005 notes

    Despite not having time to do an update for a while, we have been steadily working...

    Servo regulator

    When we last worked with it, the setup showed what seemed to be a valve lash problem - flow would begin when the high pressure ball valve reached 15% open, but it wouldn't shut off until it was closed all the way back to 5%. Since we had fabricated our own actuator to valve adapter, we thought we might have allowed too much lash into the coupling. We built a new mount using helical beam couplers with zero lash, but that turned out not to help. The coupling seems tighter, with the valve following every little jitter of the actuator, but the flow behavior seems to be an aspect of the seals in the ball valve, not the linkage between the actuator and the valve.

    This cracking problem is only really an issue at very low flow rates, so we were able to do some flow tests at roughly the performance levels that our single-man space shot vehicle will use. With a single large nitrogen bottle feeding the servo regulator, we did the following test:

    2700 psi initial bottle pressure

    60 gallons of water at 230 psi and 215 gpm flow rate

    1800 psi final bottle pressure

    2" plumbing, 1" valve

    The small fittings at the bottle valve became the limiting factor as the pressure dropped below about 2200 psi, with the servo valve eventually going wide open and still not quite being able to keep up. Our flight vehicle pressurant tanks will manifold directly out of bottle necks with a -10 fitting, so they won't become flow limited at all. When our new 36" hemispheres arrive, we will be welding up the full tankage and pressurization system for the big vehicle and doing water flow tests in preparation for testing a 5,000 lbf class engine.

    Speaking of spheres, here are a couple pictures of the tear area on the burst one:

    http://media.armadilloaerospace.com/2005_08_03/tor nSphere.jpg [armadilloaerospace.com]

    http://media.armadilloaerospace.com/2005_08_03/tor nSphere2.jpg [armadilloaerospace.com]

    Throatless engine

    I was recently looking at the table in Sutton regarding losses due to small chamber to throat contraction ratios, and they weren't as significant as I had remembered them. A chamber with no contraction ratio at all will lose 20% of its thrust due to pressure losses from accelerating gasses in the straight section, but the Isp loss is only 1.5%. The text mentions "throatless rockets" being used in some missile applications to minimize chamber length and dry mass at the expense of Isp. The text doesn't say if these were liquids or solids, but I assume they were solids.

    However, this does open up the question of building liquid engines like that. If L* remained constant, you would have an extremely long engine that would probably be impossible to cool, but I could imagine the accelerating, high speed flow could reduce required combustion stay times significantly. A 1.5% Isp loss is utterly meaningless for our purposes, so a configuration that traded that for fabrication benefits could be quite useful.

    We fired a few crude throatless lox / ethanol chambers, and the results were surprisingly encouraging. With a very crude injector (a spray nozzle for the lox and four straight horizontal jets for the ethanol), we measured a 190 Isp from a 12" long straight pipe combustion chamber. It melted in a couple seconds, but this was still very impressive. With a 3:1 expansion cone added, performance should increase about 15% to around 220 Isp. That would be right at theoretical va
  • by snorklewacker (836663) on Sunday August 07, 2005 @12:25PM (#13264174)
    We all know what this administration does to people who purchase large numbers of aluminum tubes.

    That, and he makes video games! Ones that might possibly have boobie-enabling mods!

    • John Carmack is a threat to Democracy, and has already proven that he is willing to devote massive amounts of time and development dollars to the pursuit of weapons of mass distraction, like Quake, Doom, and his .plan file.

      Because of this, I ask the Congress to give me the authority to invade John Carmack. Failing that authorization, I'll just do it anyway.

      Thank you, and good night.
    • Yeah, but knowing the id software crew, any boobie mods would involve either a) decomposing zombie boobies, or b) flying boobies with fangs. It's really just best not to think about it too much.

  • Finally an opportunity to promote my website!

    Piiiiipppesss! [Bill Cosby]
  • can it run doom3?

  • I myself try to stay with DD-cup or smaller.
  • Its strange how positive experimentation such as this is dubbed distruptive.
  • According to the X Cup Schedule [xpcup.com], Armadillo will be conducting a demo flight out in New Mexico. (Check out Oct 9th activities).

    I wonder if he'll be showing off the BFG as well... =p

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