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Inside the Tech of SpaceX's Homegrown Rocket Engine 82

An anonymous reader writes with this excerpt from a look at the engine behind SpaceX's Falcon rocket, the Merlin: "The rockstar of SpaceX may be Elon Musk, but the lead man behind the fire power is Tom Mueller. He is the Vice President of Propulsion Development and founding employee at SpaceX. Musk sought Mueller out in 2001 when Musk decided to build his own rockets instead of buying some from the Russians. Musk caught wind of a rocket engine Mueller built in his garage and 'apparently had a religious experience' once he saw it. If you didn't know, Elon Musk used $100 million of his Paypal money to start SpaceX. That money was used to build the Merlin engine Mueller had designed. The Merlin engine is the first new American booster engine in ten years and only the second in the last 25 years."
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Inside the Tech of SpaceX's Homegrown Rocket Engine

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  • by vlm ( 69642 ) on Tuesday January 15, 2013 @10:59AM (#42591087)

    No religious experience here (then again, never seen in person) but everything I've read is the Merlin series is all about Chapman's "simplify and add lightness" which a lot of the old time aerospace pioneers used to use before they became profit munching incumbent contractors.

    Pintle injector for throttling, stability, and some wall cooling. Damn good idea.

    Don't wanna run a completely isolated hydraulic system and include a zillion new single points of failure? Hmm how bout using the fuel as the hyd fluid. How bout pressurize the hydraulic "fluid" using the main turbopump. Damn good idea.

    The vacuum model uses radiative cooling. I'm sure a fat cat modern contractor would try for regenerative just to boost the contract cost / profit, but they're the "simplify and add lightness" people so simple radiative. Hardly a new idea for vacuum nozzle cooling, but a damn good one anyway.

    They also show great judgment in knowing their own limitations, they buy their turbopumps from a specialist. Things that need to be custom they do, things that can be COTS are COTS.

    I hope they can stay on task with the whole "simplify and add lightness" thing. The X and XX sound a little more like something you'd see from the incumbents rather than startups. Unless they have secrets up their sleeves, which is certainly possible.

    Maybe the standard /. car example is the Merlin is as minimal as can possibly be made that'll work, like a 60s muscle car engine or a race car engine, whereas the incumbents are more like a modern engine which is mostly an elaborate emissions control system, oh and with an engine bolted onto it almost as an afterthought.

  • by Teancum ( 67324 ) <robert_horning AT netzero DOT net> on Tuesday January 15, 2013 @11:04AM (#42591119) Homepage Journal

    Controlled fusion power has not really been practical. There is certainly some program with project like ITER [] where a whole bunch of money is being poured into that kind of research (a total waste from my viewpoint, but some physics research may happen in spite of all of that money dumped down that rat hole).

    Some other much more promising approaches include the Polywell [] and Focus Fusion [] concepts that seem to have some real theoretical potential, but none of these devices have been able to work out all of the engineering issues in terms of getting them to be producing usable energy of any kind. About the only real approach that might work and has been at least proven in terms of engineering is the original Project Orion [] concept. Unfortunately that uses thermonuclear warheads and is something only very large spacecraft would ever use. If you don't mind having nuclear weapons as a propulsion system, I suppose it could work.

    I don't know much about the system you are suggesting here, which I think is in a similar shape to other nuclear fusion power devices of any kind. A nice theory and perhaps a different approach that could be useful. Nuclear rocket engines of any kind (fission or fusion) have the potential of a very high specific impulse (the amount of thrust they can produce given a certain amount of mass for fuel + engine) and in the long run I think most interplanetary spacecraft will be using nuclear engines of some sort or another. Chemical energy is just too inefficient to be practical. The raw physics for nuclear propulsion has been more or less worked out, but coming up with a practical design that actually works is where the real problem lies.

  • by nojayuk ( 567177 ) on Tuesday January 15, 2013 @11:23AM (#42591307)

    I'm surprised you're so down on tokamak research which has actually produced large quantities of energy in tests (22MJ thermal in 1.5 seconds from the JET run in 1997, for example) while describing the con-artists like Polywell and Focus (zero joules in several years of funding and self-promotion) as "promising". At least you're not carrying a (fusion) torch for Fleischman and Pons.

  • by theNAM666 ( 179776 ) on Tuesday January 15, 2013 @12:33PM (#42592431)

    Goddard wanted to build spinning engines which used the rotary pressure to increase thrust-to-fuel ratio; visible in his posthumous patents.

    Some basic info at (follow the links): []

  • by Karrde45 ( 772180 ) on Tuesday January 15, 2013 @06:32PM (#42597325)
    The Vacuum optimized Merlin 1C is both regenerative and radiatively cooled. The main copper chamber is regen, and the columbium extension is radiative.

    In general, the Merlin as a booster engine is far lighter and much cheaper than hydrolox booster engines (but much more inneficient). They are slightly lighter and much cheaper than typical russian kerolox booster engines (and slightly less efficient than them).

    I wouldn't say the Merlin is horribly inefficient, more that it's focused on optimizing cost and thrust to weight ratio rather than ISP. There really hasn't been much in the way of American development of kerolox engines lately. Most people focus on hydrolox development or buy Russian kerolox.

"Never face facts; if you do, you'll never get up in the morning." -- Marlo Thomas