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Carmack's Throatless Rocket Engine

CmdrTaco posted about 9 years ago | from the this-is-just-strange dept.

Space 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."

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Throatless rocket engine? (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#13263742)

Ugh. This isn't a sexual euphemism of some sort, is it?

Re:Throatless rocket engine? (0)

Anonymous Coward | about 9 years ago | (#13263970)

Does it matter? You aren't gonna get any regardless.

just great... (0, Troll)

teh_mykel (756567) | about 9 years ago | (#13263743)

oh great, just what we need: more amatures building shit we dont need :/

Re:just great... (0)

Anonymous Coward | about 9 years ago | (#13263962)

It's spelled amateur.

Re:just great... (1)

LinuxInDallas (73952) | about 9 years ago | (#13264020)

Well, considering that HE is the one building this thing YOU don't need I don't see what your gripe is...

I GOT A GREASED UP YODA DOLL SHOVED UP MY ASS! (-1, Flamebait)

Anonymous Coward | about 9 years ago | (#13263747)

GO LINUX!

Oh no!!! (0)

chadamir (665725) | about 9 years ago | (#13263750)

He's going to set his beautiful hair on fire, I just know it. Don't do it john!

Re:Oh no!!! (1)

tlozano (902110) | about 9 years ago | (#13263772)

Beautiful Hair? I think you may be thinking of John Romero.

Re:Oh no!!! (1)

Luigi30 (656867) | about 9 years ago | (#13263780)

That would be John Romero, no?

Re:Oh no!!! (0, Troll)

sgant (178166) | about 9 years ago | (#13264096)

the NASCAR guys may really start entering space competitions like the X-Cup.

So you mean rednecks named Cooter are gonna be going into space?

Yeah, I have no idea about NASCAR and just preying on stereotypes...so sue me.

X-Cup? (0)

AtariDatacenter (31657) | about 9 years ago | (#13263753)

I thought it was the X-Prize? Or did I miss something?

Re:X-Cup? (1)

negaluke (893108) | about 9 years ago | (#13263792)

...you missed something; namely, the link in the article.

Re:X-Cup? (5, Informative)

MindStalker (22827) | about 9 years ago | (#13263858)

If you read the link, the X-Prize people are talking about starting the X-Cup, a regular space competition.

Re:X-Cup? (1, Funny)

Anonymous Coward | about 9 years ago | (#13264064)

X-Cup?

Hell, A D- or DD-Cup's about all I'm after.

pipedream (5, Funny)

Anonymous Coward | about 9 years ago | (#13263756)

the Pipedream finally becomes reality.

5,000 lbf engine? (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#13263758)

5,000 lbf engine

But on Vista it will only be 2,500lbf - that crap

Carmack's Dream... (2, Funny)

Mastadex (576985) | about 9 years ago | (#13263760)

..is to eventually make a fully working version of the BFG. This is just the first setp.

Wasted Talent (5, Funny)

Thakandar2 (260848) | about 9 years ago | (#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.

Game God rocketjumps himself to death (5, Funny)

Anonymous Coward | about 9 years ago | (#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.

Re:Game God rocketjumps himself to death (1)

Meagermanx (768421) | about 9 years ago | (#13263859)

I bet I could survive a rocket jump... Hey, I think I'm gonna go grab my leftover fireworks and try to jump onto the garage!

Re:Game God rocketjumps himself to death (1, Funny)

Anonymous Coward | about 9 years ago | (#13264083)

Before you do so please tell us wether you have kids so we know wether to order a darwin award.

Standby (1)

gaanagaa (784648) | about 9 years ago | (#13263782)

Carmack's UAC Rocket getting ready for its first flight. NASA, Beware!

There's a lot more to a rocket engine... (-1, Troll)

SCHecklerX (229973) | about 9 years ago | (#13263783)

...than building it. How about the nozzle designs? Unless Carmack is properly matching a nozzle to the back pressure generated by his engine such that the shock wave is optimal (at the nozzle exit), I'm not impressed. If you have shock waves inside the nozzle or if you blow the shock out the end, you are losing energy, and potentially wrecking equipment.

Re:There's a lot more to a rocket engine... (5, Informative)

everphilski (877346) | about 9 years ago | (#13263808)

If you would have read through armadillo's website you would see that he has been putting a serious effort in. As an aerospace engineer who has been keeping tabs on John for several years I can assure you he's got his design well thought out.

Throatless rockets aren't new... they've been around for awhile. They aren't as efficient as a throated rocket but they offer some operational advantages (namely in throttling, which is nice for a powered reentry).
-everphilski-

Re:There's a lot more to a rocket engine... (2, Insightful)

Anonymous Coward | about 9 years ago | (#13263898)

"If you would have read through armadillo's website you would see that he has been putting a serious effort in. As an aerospace engineer who has been keeping tabs on John for several years I can assure you he's got his design well thought out." - by everphilski (877346) on Sunday August 07, @11:07AM

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

Re:There's a lot more to a rocket engine... (2)

jericho4.0 (565125) | about 9 years ago | (#13264177)

I always thought one of the more interesting things about Carmack wasn't his original work (which is impressive) but his ability to mine academic papers for techniques useful to him. Most of the really cool things he introduced to the gaming world came from research in CGI and such (BSP's, etc). The point is, while everyone else was writing what they know, John was learning what he needed to know to make his vision.

Re:There's a lot more to a rocket engine... (1)

RayBender (525745) | about 9 years ago | (#13263920)

Throatless rockets aren't new... they've been around for awhile. They aren't as efficient as a throated rocket but they offer some operational advantages

How much loss of efficiency are we talking? (presumably Isp). Would that pretty much kill any chance if using them for space launch vehicles?

Re:There's a lot more to a rocket engine... (2, Interesting)

Wolfkin (17910) | about 9 years ago | (#13263989)

Per Carmack's writeup, 1.5% ISP loss, which is lost in the noise for their purposes. He also mentions that he thinks he can get about a 15% increase over their initial tested ISP, which was about 190 seconds, and that that would put the ISP very close to the maximum value for the propellant of 220 seconds.

Re:There's a lot more to a rocket engine... (-1, Redundant)

SCHecklerX (229973) | about 9 years ago | (#13263815)

To follow up to my previous post (yeah, bad form, I know)... How much *design* is actually going into these if they are expecting to build 2-3 a week??? It seems that Carmack is taking the hobbyist programmer approach to engineering. I won't argue how right or wrong this is, but my thoughts are towards the latter. Sure, you need to test *some*, but eventually you should be able to actually have an idea about how something will work without having to build the damned thing first. 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.

Re:There's a lot more to a rocket engine... (0)

Anonymous Coward | about 9 years ago | (#13263931)

rtfa and/or stfu. noob.

Re:There's a lot more to a rocket engine... (2, Insightful)

Anonymous Coward | about 9 years ago | (#13263987)

I know it sounds crazy, but sometimes it is much easier to evolve a nice solution to an engineering problem than to calculate one. For example calculating robustness and reliability is very difficult. It is much easier to simply measure it.

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:There's a lot more to a rocket engine... (1)

biglig2 (89374) | about 9 years ago | (#13264080)

Didn't someone once say "Release early, release often"?

Re:There's a lot more to a rocket engine... (1)

SA Stevens (862201) | about 9 years ago | (#13264139)

Maybe IBM will step in and straighten some of it out for Carmack. Outside experts 'stepping in' has certainly salvaged Linux. . .

math vs reality (1)

redcone (838393) | about 9 years ago | (#13264158)

There are times when the physics points to previously unimagined possibilities--think Einsteins equations and the atomic bomb--and there are other times when actual results contradict our understanding of the physics involved--think ceramic high-temperature superconductors...most 1980s era physicists would have dismissed the idea out of hand....but they worked and the physics had to be revisited to try and explain why.

Re:There's a lot more to a rocket engine... (1)

neksys (87486) | about 9 years ago | (#13263818)

... this is the same guy that made a serious bid for the X-Prize. I think he knows how not to blow his nozzles.

You don't understand economics (1)

Moderation abuser (184013) | about 9 years ago | (#13263929)

It doesn't have to be great, it doesn't even have to be good, it only has to be good enough.

The very first internal combusion engines could barely drive a horseless carriage at 10mph just a century ago. Today, Formula 1 are capable of 220+ mph and can go round bends with 5G of lateral acceleration.
 

Re:You don't understand rocketry (4, Interesting)

Animats (122034) | about 9 years ago | (#13264128)

It doesn't have to be great, it doesn't even have to be good, it only has to be good enough.

Unfortunately, no. Chemically fueled rockets are just barely capable of making it to orbit. They're mostly fuel tankage. Single stage to orbit craft must have at least a 90% fuel fraction. At least. Any serious inefficiency or weight growth kills the design, as happened for Rotary Rocket.

Staging helps. Two stages will get you to low earth orbit. Beyond low orbit usually requires three. This reduces the fuel fraction, but by less than one would hope. The Shuttle's fuel fraction is around 89%.

So space flight is all about weight reduction. Which is why everything is so fragile and unreliable. If you could build a launch system with a fuel fraction of 50%, which is roughly where most aircraft live, it would be a straightforward job.

Re:There's a lot more to a rocket engine... (1)

deglr6328 (150198) | about 9 years ago | (#13263958)

Yeah, exactly, there's nothing revolutionary or "disruptive" about it. Its crap. If he were really looking for a useful new design he'd be looking at something like this [wikipedia.org] that automatically adjusts for maximum efficiency as external pressure changes.

Re:There's a lot more to a rocket engine... (5, Informative)

WolfWithoutAClause (162946) | about 9 years ago | (#13264011)

Cough-bullshit-cough. Hint: you can't fake rocket science on Slashdot; there's real rocket scientists here!

Ok, first, you don't get shockwaves in nozzles- not unless you've got a rough nozzle surface, which is a bad idea, because the hot gas comes to a screaming halt ("stagnates") and the local temperature goes way up, and then the nozzle melts. And yeah, Carmack knows that a nozzle and throat needs to be smooth, this isn't the first bipropellent engine he's built, and he's widely known not to be stupid. :-).

Oh yeah and actually, even these 'throatless' engines has a throat, but it's kinda hard to spot :-), the gas makes up its own mind where to put the throat, in realtime- the throat is defined to be where the gas goes sonic, and this always happens when the combustion pressure is more than 2.7 times the ambient.

You mainly get shockwaves in air inlets in jet engines, not in the nozzle. You also get shockwaves in the exhaust plume of rocket engines where the exhaust kinda bounces of the external atmosphere, but that's harmless (actually kinda pretty google on "mach diamonds"), and they form wayyy downstream of the exit. Oh yeah, and a rocket launching, once it passes about mach 0.85 gives transonic shockwave around its nosecone, and then later supersonic shockwaves there, those can cause damage, but they rarely do.

So, these non existent shockwaves can't damage any equipment, or waste any energy. Oh yeah, and did I mention there aren't any shockwaves? :-)

Obscure unit (-1, Flamebait)

David Horn (772985) | about 9 years ago | (#13263788)

What the hell is a lbf? Is North America really so backwards and stubborn they refuse to use units that the rest of the world is perfectly happy with.

PS. Miles don't count. I can think in miles. I can't think in pounds, and I especially can't think in pound-feet, which is what this author expects me to do.

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13263816)

lbf is pounds-force it is still the international standard for the thrust an engine will produce. Like the trent 900 RR engine will produce upto and including 90,000lb of thrust

The other unit for this is just plain NEWTON or N

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13263820)


s North America really so backwards and stubborn they refuse to use units that the rest of the world is perfectly happy with

yes

Re:Obscure unit (1)

bryerton (524453) | about 9 years ago | (#13264163)

No. Canada's official system of measurement is metric.

Re:Obscure unit (3, Funny)

zero time ghost (699927) | about 9 years ago | (#13263836)

I'm miffed that he didn't express it in stone-furlongs.

Re:Obscure unit (1)

whopis (465819) | about 9 years ago | (#13263847)

I thought they always measured rocket motor efficiencies in rods/hogshead.

Re:Obscure unit (1)

SA Stevens (862201) | about 9 years ago | (#13264151)

I'm just pissed that the French Revolutionaries didn't also succeed in imposing the decimal calendar.

I mean, WTF? Why can't there be 100 days in a year? It's as arbitrary as any other aspect of the Metric system.

Re:Obscure unit (1)

nusuth (520833) | about 9 years ago | (#13264220)

Actually the correct units would be stone.furlongs/(fortnight.fortnight) grandparent got his dimensions wrong.

Re:Obscure unit (4, Insightful)

DigiShaman (671371) | about 9 years ago | (#13263850)

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:Obscure unit (1)

denis-The-menace (471988) | about 9 years ago | (#13264103)

The only industry that has made a full switch is the drug industry, both legal (mg=Miligrams) and illegal (Grams and kilos).

Re:Obscure unit (1)

TeknoHog (164938) | about 9 years ago | (#13264155)

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.

How come Europe has been able to switch over to metric? We did use some backward measuring systems in the past, and I'm sure we had problems converting.

Re:Obscure unit (2, Informative)

Waffle Iron (339739) | about 9 years ago | (#13263867)

I especially can't think in pound-feet, which is what this author expects me to do.

Well then, that's no problem, as lbf means "pounds-force", not pounds*feet (which would be a measure of torque).

Here's a hint: a serving of beer weighs about a pound. One lbf is how much force you must use to hold it up (assuming you're drinking it somewhere on Earth).

It's also equivalent to about 4.44 newtons, but that unit is too small to provide a satisfactory serving.

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13263871)

So you cant think in Pound-feet? can you think in Newtons? which is the other unit to describe thrust?

I might be a Metric European BUT for THrust I just hate the Newton

Pound-foot, tells you how many pounds can be moved a foot, simple

lbf = pounds force (1)

TerranFury (726743) | about 9 years ago | (#13263894)

I think that "lbf" here is just for "pound force."

There are two similar versions of the U.S. customary system. The more consistent of the two uses the pound as the unit of force and the slug as the unit of mass. All the equations you know and love work well in this system. In these units, for example, F=mg where g = 32 lbs/slug = 9.81 N/kg

There's also a second system in which the unit of mass is not the slug but the pound -- in which case there needs to be a distinction made between "pounds mass" and "pounds force." So you get two units, "lb" for mass, and "lbf" for force. This is what you're seeing here.

Unfortunately the second system has a way of screwing up equations; you need to throw in extra 1/32 conversion factors to lots of equations that relate forces to masses, and it's generally a pain to work with.

Re:Obscure unit (-1, Troll)

Gerad (86818) | about 9 years ago | (#13263913)

If North America is so backwards, why are you wastisng your time trolling on a North American news site?

Re:Obscure unit (0, Offtopic)

tripslash (683760) | about 9 years ago | (#13264037)

I know I'll get modded up for this, but ...

maybe not.

Re:Obscure unit (4, Funny)

Planesdragon (210349) | about 9 years ago | (#13263945)

What the hell is a lbf? Is North America really so backwards and stubborn they refuse to use units that the rest of the world is perfectly happy with.

Yes. We are able to use non-decimal units because, quite frankly, most applications call for non-decimal units.

Once you've been to the moon and back, THEN maybe we'll consider your ideas on measurement. ;)

Re:Obscure unit (5, Funny)

paniq (833972) | about 9 years ago | (#13264000)

Re:Obscure unit (1)

$RANDOMLUSER (804576) | about 9 years ago | (#13264110)

Damn that's funny. Wish I had mods today.

Re:Obscure unit (1)

Beryllium Sphere(tm) (193358) | about 9 years ago | (#13263954)

Not only was it non-intuitive, it even led you to the wrong conclusion! It stands for pounds of force, which are equal to about 4.45 newtons. The "f" stands for "force" to distinguish it from pounds as a unit of mass.

For anyone having trouble getting used to metric, think of one newton as the amount of force required to lift an apple off the ground.

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13263973)

Not really.

1N is defind as lifting 1kg 1m

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13264084)

OMG you're a retard. A unit of force doesn't describe WORK, numbnuts.

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13264180)

Very little of anything that has to do with the Metric system defines real work, for that matter.

Just diddling around with test tubes, and 32-hour-week bloated loafers in the provinces of France.

Re:Obscure unit (5, Funny)

Qzukk (229616) | about 9 years ago | (#13264119)

Is North America really so backwards and stubborn they refuse to use units that the rest of the world is perfectly happy with.

Ok, it's a 5klbf engine. Happy?

Re:Obscure unit (4, Interesting)

Dr. Zowie (109983) | about 9 years ago | (#13264156)

lbf is "pounds-force", a slightly more specific unit than "lb", which could refer to a mass (0.454 kg) or a force (4.54 N).

As a scientist I think in SI these days though it took years to unlearn the training of my youth, and I still vascillate between F and C for my preferred temperature unit.

Nobody uses perfect units. Why aren't you measuring your car's efficiency in inverse square millimeters?

Re:Obscure unit (0, Redundant)

Cecil (37810) | about 9 years ago | (#13264167)

lbf is "pounds of force", not pound-feet, which would be typically be shown as lb-ft or lb*ft.

And yes, we are that backwards and stubborn. Jet and rocket engines are usually measured in pounds of thrust, not in newtons. Although they are the same class of unit (measures of force).

Re:Obscure unit (0)

Anonymous Coward | about 9 years ago | (#13264188)

I can't think in pounds, and I especially can't think in pound-feet, which is what this author expects me to do.

You can't think very well.

It's pounds of force, which you could have discovered by doing a minimal amount of research. All praise the consistency of the metric system, it gives you so many choices (CGS, ESU, EMU, Gaussian, MKS, MKSA, SI) for systems of units.

Armadillo seems stalled, engine-wise... (4, Insightful)

Skyshadow (508) | about 9 years ago | (#13263793)

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.

The first cars (1)

Moderation abuser (184013) | about 9 years ago | (#13263978)

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.

 

Re:Armadillo seems stalled, engine-wise... (4, Informative)

cr_nucleus (518205) | about 9 years ago | (#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.

Re:Armadillo seems stalled, engine-wise... (0)

Anonymous Coward | about 9 years ago | (#13264105)

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".

Thats what NASA thought too, and now we have the shuttle. It's time to come up with something new, and to do that, you have to try and fail a lot of things.

Debbies does Engines. (0)

Anonymous Coward | about 9 years ago | (#13263809)

"John Carmack is working a potentially disruptive technology: A throatless rocket engine."

So I guess the porn industry will not be funding this?

Pfh (1)

czarangelus (805501) | about 9 years ago | (#13263825)

This isn't rocket science you know.

I read TFA but... (3, Insightful)

zr-rifle (677585) | about 9 years ago | (#13263826)

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... (1)

SA Stevens (862201) | about 9 years ago | (#13264195)

John is a hero in these parts because he embodies the hacker spirit. No need for theoretical work ahead of time, or an architecture. Just keep hacking away at it. Weekly builds, trial and error. That sort of thing.

It most definitely will 'run Linux' btw.

Re:I read TFA but... (4, Informative)

Gorobei (127755) | about 9 years ago | (#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.

before/after (2, Informative)

biff-mo (681452) | about 9 years ago | (#13263839)

Before [armadilloaerospace.com] .....


After [armadilloaerospace.com] .

Science? (0)

tlozano (902110) | about 9 years ago | (#13263843)

If this was new rendering technology, I would probably take a second look, but what new innovation can Carmack add to rocket science. I akin this to some guy figuring out a cool new way to launch a potato from a pvc pipe, but not innovative science. He is a brilliant guy, but he doesn't work for NASA... well on second thought maybe he should.

Re:Science? (4, Insightful)

cyber_rigger (527103) | about 9 years ago | (#13264127)


but he doesn't work for NASA

Neither does Burt Rutan.

Someone call George Bernard Shaw (3, Funny)

bubbaprog (783125) | about 9 years ago | (#13263852)

I think Mr. Carmack has a bit of a Pygmalion complex with Commander Keen. To the heavens!

ISP Still very low (1)

mikejz84 (771717) | about 9 years ago | (#13263884)

He reports only an ISP only in the low 200s, this is not efficent enought to get to orbit.

Re:ISP Still very low (1)

Manhigh (148034) | about 9 years ago | (#13263972)

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.

Re:ISP Still very low (3, Informative)

Viadd (173388) | about 9 years ago | (#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.

Re:ISP Still very low (0)

Anonymous Coward | about 9 years ago | (#13264029)

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,

Bad ISP all right!

Re:ISP Still very low (3, Informative)

mikejz84 (771717) | about 9 years ago | (#13264100)

Yes, However the Shuttle's 470ish ISP SSMEs do most of the work in getting it to orbit. If he could get the rating around 250 I would say he has a chance at maybe a first stage.

Toasted the Server Already (5, Funny)

angrist (787928) | about 9 years ago | (#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

Re:Toasted the Server Already (1)

allanc (25681) | about 9 years ago | (#13264190)

Oh no! If all of those people from slashdot click that link, we'll slashdot Slashdot!

Great. (1, Insightful)

Anonymous Coward | about 9 years ago | (#13263907)

Now "disruptive technology" will become the new buzzword. Suddenly AJAX will be called disruptive technology. Linux will be called disruptive technology. The next P2P file sharing protocol will be called disruptive technology. Fuck!

Throatless? (1)

dev_alac (536560) | about 9 years ago | (#13263928)

But... no throat, no supersonic flow... sooooo much energy being lost there...

Re:Throatless? (4, Informative)

WolfWithoutAClause (162946) | about 9 years ago | (#13264109)

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.

Home made rocket motors (3, Funny)

standards (461431) | about 9 years ago | (#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.

Expanstion ratio counts (3, Informative)

simonbp (412489) | about 9 years ago | (#13264009)

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 ;)

I'd like to RTFA.. (1)

RM6f9 (825298) | about 9 years ago | (#13264079)

Would someone please be kind enough to copy-n-paste it?

The Article (5, Informative)

Rhoon (785258) | about 9 years ago | (#13264111)

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 values, and MUCH better than we have been seeing in our engines so far.

Side note: it turns out that our flow distribution to cooling channels and injector ports has been Really Bad with our previous designs. The test that demonstrated this dramatically for us was to cut off the top of an engine so the cooling channels were exposed, and flow water through it. With our original manifolds, there was a 2:1 difference in height between the highest and lowest flowing channels, and the high point moved around the engine as flow rates changed. We are now using taper milled manifolds that maintain a constant flow velocity around the ring, and flow rates are essentially the same. Unfortunately, this doesn't seemed to have helped the engines in any perceptible way.

Our second revision to the engine didn't work out so well. We wanted to incorporate two of our new tapered flow manifolds with the same injection points we have been using on the other engines, but I wasn't about to try machining them out of stainless to weld onto expendable pipe stages. Instead, I machined the engine top parts out of brass, and we tried brazing them together and onto a section of straight pipe.

This didn't work out for two independent reasons. Most obviously, because the brass top section had a smaller ID than the stainless pipe below it, the step section served as an excellent flameholder, and the pipe burned itself off right under the injector before the rest of the pipe even started glowing. Second, the burn-off wasn't completely even, so we flowed water through the injectors and found out that almost half of the LOX holes weren't flowing anything at all. We cut the engine up and found that brazing flux had snuck in and plugged most of them up.

http://media.armadilloaerospace.com/2005_08_03/bra zed_before.jpg [armadilloaerospace.com]

http://media.armadilloaerospace.com/2005_08_03/bra zed_after.jpg [armadilloaerospace.com]

Watching the disposable chambers glow red hot gives us lots of good information on the evenness of our burning and the required L* of the engine, but we decided to go ahead and make a regen cooled pipe engine, because we could just make the entire thing out of aluminum. A 2" aluminum pipe with only light external machining can be a slip fit inside a 2.5" tube section, which lets us make these engines without any boring at all.

http://media.armadilloaerospace.com/2005_08_03/reg enThroatless.jpg [armadilloaerospace.com]

http://media.armadilloaerospace.com/2005_08_03/tes tingRegen.jpg [armadilloaerospace.com]

The first test engine was a bit shorter than the expendable ones, with a 12" total engine pipe length, and 9.5" of cooling channels below the injector. 20 cooling channels of 3/16" width, tapering from 0.030" deep at the nozzle end to 0.060" deep at the injection point.

Isp performance wasn't good. There was about 30% less L* on this motor, but it may turn out that our "crappy, cobbled together" injector for the expendable engine was actually a lot better than the 20 hole version we moved to. We have been using very low velocity injectors because we had a lot of smooth running engines even without high pressure drop, and I feared that relying on the pressure drop for stability would give us problems when deep throttling, However, the hand-made injector did have four very high velocity streams impinging reasonably accurately, and that may have been the key to the performance, more so than the straight tube nature of the engine.

Since we didn't have much else to do with the first regen tube engine, we made a couple more full throttle runs, then did a run without any ethyl silicate mixed in the fuel. At about the 25 second point, fuel flow rose and the engine note changed. We had burned through one of the cooling channels. That was the type of back-to-back confirmation that I was looking for, showing that the ethyl silicate really is making a difference, and we aren't just putting it in as a random hope. We are currently using 1 oz of ethyl silicate per gallon of ethanol.

The next test engine has much higher injection velocity, and 3" more chamber length. 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.

We got to see a new failure mode on this one - the internal chamber buckled, then melted through. We have been making the outer jacket a tight press fit over the inner chamber, but the thermal expansion of the chamber, coupled with the extra pressure drop, apparently caused the inner chamber to buckle instead of stretching the jacket.

The next test engine will use a pressure drop intermediate between the last two, use a looser fit outer jacket (inner machined to 2.345") to allow a bit of thermal expansion, and will bring the propellant impingement points farther out towards the side. I used to have issues with wandering drill bits during injector drilling, but now I am spotting everything with a larger diameter carbide spotting drill, and manually applying cutting fluid to every hole as the mill runs. The 1/32" holes in the last engine came out perfectly straight.

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.

Hold down test

We swapped out the valve actuators on the vehicle from 1.5 second to 0.5 second speeds. On the previous vehicles we had moved to slower valves to reduce the bobbing at hover effect that we got from the overshoots due to latency between moving the valve and vehicle acceleration, but now that all the motor drives use PWM for variable speed, I can control this much better in software. Having valves that shut off fast is good in general - 1.5 seconds feels like a very long time when you notice something is on fire and you want to shut down the engine.

We moved the flow meters from the test stand to the vehicle in preparation for calibrating throttled mixture ratios in-situ. This involved some contorted plumbing, and we are still having some leakage problems. I finally got around to finding a supplier (Aircraft Spruce stocks them) of the little conical seal caps you can put on AN fittings to improve sealing, so hopefully that will help. Plumbing 1" and over is much more difficult to seal than smaller stuff. We are moving more and more towards welding practically everything together. It is tempting to move to elastomer seals for the fuel side sometimes.

Another thing we have started to do is put some red food coloring in our ethanol when it has been mixed with ethyl silicate, so we don't accidentally forget it, mix too much in, or confuse fuel drained out of tanks with pure fuel. This has the side benefit of leaving evidence where fuel leaks have been, even if the ethanol has evaporated away.

We welded the gimbal arms on the latest converging / diverging engine, and mounted it up under the vehicle. We fired up the engine and gimbaled it around for a few seconds, which should be more heat load than the vehicle will see during liftoff and landing on an actual flight. There was a little bit of fire on the bottom of the legs' silica insulation, which we think was some of the RTV that holds it on burning, but it could also have just been methanol from the engine that came out during the initial very rich throttle up. The main heat shield and the rest of the legs were cooler than we expected, we probably worried more than necessary.

The one surprise was that the vehicle clearly pulled the support chains taut, which we didn't expect at the pressure we were running. With propellant, the vehicle was over 400 pounds, and at the pressure we ran it, the engine should have made under 350 pounds of thrust. My working theory is that the big flat heat shield allowed the vehicle to get some "ground effect" lift since it was only 3' off the ground.

http://media.armadilloaerospace.com/2005_08_03/hol dDownTest.jpg [armadilloaerospace.com]

http://media.armadilloaerospace.com/2005_08_03/hol dDownTest.mpg [armadilloaerospace.com]

I spent a while double checking the GPS integration with the new electronics box orientation, and getting the startup self-test functioning with the new electronics layout. Since the exact same electronics box runs both the test stand and the vehicle, we have had a few problems with forgetting to add the command line parameter to specify the vehicle valve calibrations. To fix that, I made a stub connector for one of the sensor values that isn't used on the vehicle (the load cell sensor) that just ties the signal line to ground, so I read a hard zero from that channel. I now use that to fail the self test if the state of that line doesn't match the specified configuration.

The vehicle is ready to fly, as soon as we are comfortable with the throttling and reliability of our engines. Worst case, we can just make an engine with really crappy Isp and still do our flights while we are figuring out how to make a reliable, higher Isp engine.

Dr. Carmack says... (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#13264131)

Carmack says: NOTHING you idiot Carmack is dead he's locked in my basement.

He'd best watch his back (3, Funny)

snorklewacker (836663) | about 9 years ago | (#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!

Why use a rocket? (0)

Anonymous Coward | about 9 years ago | (#13264176)

Why are scientists still determined to use rockets?
Why not just move the universe around the craft? It works for Professor Hubert Farnsworth! Nothing's impossible; not if you can imagine it!

</obligatory groening reference>

Very promising (0)

Anonymous Coward | about 9 years ago | (#13264193)

We've been long-needing another faulty, nonfunctional technology to replace the "lie detector".

Piping (1)

pipingguy (566974) | about 9 years ago | (#13264201)


Finally an opportunity to promote my website!

Piiiiipppesss! [Bill Cosby]

nice design, but... (1)

Savatte (111615) | about 9 years ago | (#13264202)

can it run doom3?

Boy, he's swimming against the tide now... (0)

johnny cashed (590023) | about 9 years ago | (#13264215)

I mean, hundreds of years years of rocket nozzle development is just thrown out the window. Remember, fireworks were developed in China a long time ago, and they had tapered nozzles. Oh, and all that research by Goddard and Von Braun et al, was just a waste of time I guess. I couldn't read the article because it tanked, but it sounds as though he is trying to make an easy to manufacture engine work, instead of making a better design easy to manufacture. CNC? Robotic welding? Sure they are expensive, but it looks as though his "disruptive" technology may just be disruptive to Armadillo Aerospace. How high a price can you put on failure? I guess the sky is the limit. Maybe it is time to hire some more (or better) engineers. Best of luck with your tubular nozzle. Maybe he should look into spike rocket nozzles. They look to be easier to manufacture.
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