Carmack's Throatless Rocket Engine 351
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."
Armadillo seems stalled, engine-wise... (Score:5, Insightful)
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.
I read TFA but... (Score:4, Insightful)
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.
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Re:There's a lot more to a rocket engine... (Score:2, Insightful)
That is good to hear, that another pro from that SPECIFIC field is seconding his designs, and as far as thinking things out (when it comes to this guy, Mr. Carmack)?
I believe you.
E.G.=> Ever heard of "Carmack's Reverse"? If not, look it up, & check it out... this showed me this guy can THINK, & "outside of/above & beyond the box"...
Not every computer scientist has things like that to his credit!
IMO, these types of things (engines/algorithms) to overcome limitations ARE the mark of what others called him here:
A genius.
IMO, he is.
After all, his wares from IDSoftware & contributions in the OpenSource world show it. There's little arguing with that & little arguing with success.
*
APK
P.S.=> I wish him the best of luck to be quite blunt & honest about it...
Like he himself has said (not a direct quote):
Once you've accomplished a decent amount in 1 particular field? It's good to take a "hard right turn" into another one that interests you and make a career of it!
In his case it would NOT surprise me one iota if he does not end up becoming a breakthru maker in it as he did in computer science...
People like these, just give them time & experience: They're the types that always come thru!
Yes, this is "intellectual/technical hero worship" & he is one of the few out there I give that much credit to!
He, along with Mr. Anders Hejlsberg (of Borland (TurboPascal/Delphi designer) & Microsoft (C# & Visual Studio improvements) fame)... they're 2 of the 'outstanding' individuals in THIS field (computers) out there now, truly outstanding ones.
There IS a diff. between pretty good, good, great, & absolutely outstanding/in a league of their own.
Never underestimate folks like those, they often surprise... apk
Great. (Score:1, Insightful)
Re:There's a lot more to a rocket engine... (Score:2, Insightful)
Change the unreliable bits to something else, and see if it breaks. If you kill off the most unreliable part of your design each time, I guess you can work out what happens.
I'm not saying that you shouldn't use simulations or calculate anything at all. Use them as guiding hands, but don't let them alter the process. The problem is many people think that it is easy to create some sort of `breakthrough' design. It isn't; if it was, then everyone would have them.
Re:Science? (Score:4, Insightful)
but he doesn't work for NASA
Neither does Burt Rutan.
Re:Armadillo seems stalled, engine-wise... (Score:3, Insightful)
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 they're using) should fall out of the bottom.
Their throatless rockets may not be the most efficient, it sounds like they'll be far more maintainable and almost bulletproof - which is far more important to them at the moment than raw power.
Re:Obscure unit (Score:1, Insightful)
is that so?
keep in mind that the US had to "borrow" german scientists like and Werner von Braun from the third reich nazi regime in order to develop the technology.
no need to tank me for reminding...
Re:I read TFA but... (Score:4, Insightful)
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:5, Insightful)
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
Re:ISP Still very low (Score:3, Insightful)
"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%."
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Re:Obscure unit (Score:3, Insightful)
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Re:I read TFA but... (Score:1, Insightful)
I'm thinking Carmack is heading for a cell next to Jose Padilla if he keeps telling people how easy it is to make a delivery vehicle for weapons of mass destruction. I mean Al Qaeda could be reading Carmack's article right now and warming up the machine tools to build a rocket to lob chemical and biological weapons at American cities. The carnage.....where is the Fox News coverage of the imminent danger.
Re:Obscure unit (Score:2, Insightful)
Yes! For the slight inconvenience of having to work with four different length units (inch, foot, yard, mile) with easily remembered conversion factors, we can finally express lengths of 1/3 or 1/6 inch as umm... 10.667/32 in, or... 0.3333 mill. Better example: Highway exit signs. The Englisch system is obviously superior, since we can easily say 1/4 mile, where you only need to divide 1760 by 4 to get yards. Easy! Converting something like 1/4 kilometer to meters would involve dividing 1000 by 4: Totally ARBITRARY!
You win, I'm switching over to Imperial today.
chl
PS: Is 543 yards plus 1563 yards longer than 1-1/4 mile? I lost my calculator.
PPS: Sarcasm is not funny. Mod this insightful.
Re:You don't understand rocketry (Score:3, Insightful)
That's the NASA myth, and why they build crappy spacecraft.
Certainly weight reduction is important, but if you don't keep looking at the overall system, and the trade-offs, you'll fuck up the design. The focus on Isp is a symptom of that. The Shuttle is a prime example of it.
Sure, high Isp means you need less weight of propellant per unit of impulse (thrust * time), which sounds great. So the propulsion guys start focusing on Isp and design exotic high-pressure engines that use fuels like LH2 which is really light and gives you an engine with a 400-range Isp. Never mind that you have to practically rebuild the thing after every flight. (It also gives you a relatively low thrust to weight ratio, so you end up having to augment it at launch with something with high thrust even if crappy Isp, like SRBs)
The propellant guys figure LH2 is cool too -- highest energy per unit weight, and all that.
And the airframe guys just build the lightest structure they can to hold what the propulsion and propulsion guys give them.
All of which leads to a suboptimal design.
LH2 is about the lowest density liquid around. High density urethane foam would sink in the stuff, it's about the same density as lighter weight foams. Which means you need a bloody big tank to put the stuff in. The Shuttle uses 8 times, by weight, as much LOX as LH2, but the LH2 tank is about three times bigger than the LOX tank.
Tankage is heavy. The portion of airframe weight devoted to tankage scales as the volume of the propellant, not the weight.
Replace LH2 with something like liquid methane and your tankage -- and its weight -- becomes much less, which ends up improving your fuel fraction, even with the slightly lower Isp of methane-LOX.
The original Atlas launch vehicle, which used LOX and kerosene and stainless steel tankage, could reach orbit without shedding any stages. (Although it did shed two of its three engines.) It also couldn't carry much payload that way, but we're talking late 1950s technology.
NASA technology is fragile and unreliable because they're more interested in engineering projects for the sake of engineering projects, and then have to hack it back because of budget limitations. Anyone in software development who has seen a project get designed with all sorts of bells and whistles and the designers' favorite new technlogies, only to be turned into some ugly hacks toward the end when deadlines are looming and the budget has run out, will understand this.
Try 100 times...? (Score:1, Insightful)
With Carmack is trying many different technologies, I presume that he is learning from each problem/difficulty with each model he works with. This shall eventually result in him having a broad and deep knowledge of the technologies involved, and give him the ability to achieve his goal, given enough time.
Re:You don't understand rocketry (Score:2, Insightful)
I do love this old chestnut: it's perfectly true, and yet so misleading.
Helpful Hint #1: How long does it take to fly the 747 to Australia? What would happen if you took that long getting to orbit?
Helpful Hint #2: What is the difference between energy and power? If two machines release the same total energy, but machine #2 must release it much more quickly with equal or greater precision, which is likely to be more complex and expensive?