Carmack's Throatless Rocket Engine

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."

Comments

Armadillo seems stalled, engine-wise...

[Skyshadow]

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.

Re:Armadillo seems stalled, engine-wise...

[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 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.

I read TFA but...

[zr-rifle]

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...

[dufke]

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...

[stienman]

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

Re:Obscure unit

[DigiShaman]

No, we are not "stubborn". And yes, the standard system SUCKS. The reason we haven't moved to metric is that we have too much momentum built up in society for anyone to switch over. What needs to happen in America is a migration. This is slowly being done, but it will take many more generations beyond me.

I was tought the metric system in grade school. However, I only use it personally when working on cars. Most of the time GM will have a mix of standard and metric bolts these days.

Re:Science?

[cyber_rigger]

but he doesn't work for NASA

Neither does Burt Rutan.

Re:ISP Still very low

[BiggerBoat]

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%."

Re:There's a lot more to a rocket engine...

[jcr]

How much *design* is actually going into these if they are expecting to build 2-3 a week???

What does it matter? Rapid turnaround means he can develop a lot of them, and pick the best performers.

Maybe John, as brilliant as he is, should go to school for awhile to learn a bit about fluid dynamics and thermal dynamics and the equations that govern those sciences.

Why would you assume that he doesn't already know a great deal about these subjects?

I really don't get the knee-jerk reaction around here. Whenever someone does something interesting and potentially significant, there's always this chorus of people looking for something to bitch about to try to look cleverer than the guy who's acually doing something.

-jcr

Re:There's a lot more to a rocket engine...

[jcr]

The Russian approach to rocket science was along the lines of "let's see how it blows up and make sure it blows up in a different way next time".

That's a complete crock. The Russians, just like the USA, started from the V2s they captured, and applied the best engineering practices that were known at the time. They blew up a lot of rockets, and so did anyone else who every tried to build a rocket.

The fact that they got Sputnik into orbit first, and got Gagarin into space before anyone else is a testament to their skill.

-jcr

Re:What a crock!

[jcr]

This idiot should stick to games.

Well, thank you for that well-reasoned critique of his efforts.

I have to wonder, what is it about achievement, or even effort, that brings people like you out of the woodwork? Why are you so jealous of him?

'Disruptive' is one of those buzzwords that business school types throw around when they are trying to deceive investors.

It's also a term that describes any number of scientific and technological advances that came from private effort like John's. In any case, he's doing this with his own money, so what's it to you?

What is the advantage of this engine design? What are the reactants, ISP?

Hey, here's a wild idea: why not RTFA and find out?

Meaningful details like that don't get you posted on slashdot I guess.

The same could be said for meaningful critiques. Better luck next time.

-jcr