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New Rocket Engine Successfully Tested
inetsee writes "XCOR Aerospace announced that their new methane-oxygen rocket engine has been tested successfully. This is reported to be the first successful test of an engine using the combination of methane and oxygen as fuel. The fuel has higher specific impulse than kerosene and oxygen, but until now has been thought to have too much 'technology risk'."
Do I have to be the first to point out that methane doesn't have a smell. This is the natural gas that gets piped into peoples homes - the smell is added so you can detect leaks.
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There hasn't been much use, because rocket design has been on a different track than XCOR. Kerosine engines are primarily used for their high thrust to weight ratios, which help get a rocket off the ground. Once the rocket is in flight, the first stage is usually dropped in favor of a more powerful engine, such as Liquid Hydrogen/Oxygen engines. LHOx has the highest specific impulse of any fuel deployed to date; even more efficient than the methane-oxygen engines they're proposing.
The problem is that XCOR is working on a different track than NASA and the large rocket manufacturers. They're focusing on winged takeoff and landing, where high thrust to weight ratios aren't as important, and can be sacrificed for greater efficiency. (For comparison, the kerosine F-1 engines on the Saturn V produced 1.5 million lbf compared to the 7,500 lbf targetted by this engine.) So the methane-oxy engine development has less to do with politics, and more to do with the practical matters of meeting the targetted design goals.
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By far the most critical aspect of this for me is its practicality for use in Mars exploration or, more to the point, colonization. While it's obviously too soon to colonize anything at a reasonable price (and real colonization will only occur when we can get some prospect of a return commensurate to the colossal investment) but the sooner the requisite technologies enter wide use, the sooner their price starts to drop, the more hospitable the cost/benefit balance sheet begins to look. Little things like this could make ten years worth of difference.
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...and the cow jumped (?) over the moon...
Methane gas is utterly renewable. You can make it from shit, literally, and without any special equipment. The only special thing you need is a way to compress it to store it... say 200 psi tops? The only thing I can't find is a small compressor suitable for this purpose on a household scale. You can actually just run your waste into the bottom of a pond along with a steady flow of water, tent it, and capture methane - you bubble it through water to purify it. The compressing is the only issue left...
Side note: While searching for goodies I found this url which attempted to root my computer. No idea how successful it was, I'm off to go run defender and spybot.
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So the methane-oxy engine development has less to do with politics, and more to do with the practical matters of meeting the targetted design goals.
No, it has more to do with the subcontract they have with ATK to do research for NASA LINK. This pays the bills while they play with their winged rocket-plane.
For comparison, the kerosine F-1 engines on the Saturn V produced 1.5 million lbf compared to the 7,500 lbf targetted by this engine.
They were also pumping a lot more fuel and oxidizer per second (much larger m_dot). This is a small engine mounted to the back of a trailer. You could (almost) wrap your hands around it. The F-1's chamber is quite a bit bigger.
Armadillo Aerospace is considering exactly the same fuel. Some of the advantages are relatively high ISP (lower that LH2, but with a much smaller volume) and the fuel and the oxidizer (LOX) have more or less the same volume which can be a very good thing, depending on your vehicle configuration.
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Will this be rated in cowpower?
I can see it now - "Where do you stupid bovines think you're going? The mooooooooooon?"
'risk' isn't quite what people are making it out to be. Risk is the fact that a methane engine hasn't been built and operated before. By building and operating a methane engine, and improving its design (making it regeneratively cooled, using cryogenic methane as a fuel, passing x-thousand lights without incident, etc) reduces its relative risk.
NASA uses a scale called Technology Readiness Levels (TRL) which you can read about if you like. Operating this device and documenting it can help raise the TRL of methane engines.
Additionally, it is a 'risk reduction' effort because it could be a replacement for the engine of the CEV which right now is (I think) kerosene+LOX. If that falls through for some reason (what, I don't know...) there is a second option on the table. Again, reducing risk.
And yes, according to Zubrin, we can manufacture methane on Mars where the CEV will be headed in 15-20 years, so an adaptation of this might be a retrofit to the CEV someday. (but please, be critical thinkers when you read Zubrin...)
That is all.
NASA only has so much money to spread around to different projects -- and much of where it goes is mandated by congress. Consequently, there's only so much engine research that they can finance.
Methane engines are interesting, but they're no panacea. Methane lines on the spectrum between kerosene (dense, comparatively high temperature, moderate ISP) and hydrogen (sparse, extremely low temperature, high ISP). Specifically:
Hydrogen@20K: 70kg/m^3 (fuel**), 358kg/m^3 (bulk**), 455.9 (ISP sec@100:1/20MPa)
Methane@112K: 423kg/m^3 (fuel), 801kg/m^3 (bulk), 368.3 (ISP sec@100:1/20MPa)
Kerosene-based (RP-1)@298K: 820kg/m^3 (fuel), 1026kg/m^3(bulk), 354.6 (ISP sec@100:1/20MPa)
Note that it's a rather small ISP gain over kerosene -- not close to the performance of hydrogen -- yet its density is halfway between kerosene and hydrogen. While a small gain in ISP can be a big boost in performance, that's a pretty big density hit.
A fuel that I find interesting is propane. While at its boiling point, it's not that interesting:
Propane@231K: 582kg/m^3 (fuel), 905kg/m^3 (bulk), 361.9 (ISP sec@100:1/20MPa)
But cool it to 100K, and you get:
Propane@100K: 782kg/m^3 (fuel), 1014kg/m^3 (bulk), 361.9 (ISP sec@100:1/20MPa)
Not only are these attractive numbers, but since the propane is similar in temperature to the LOX, they can share a common bulkhead. Of course, it can't go too much below that, or its viscosity will rise too much (at 100K, it's similar to kerosene).
To make methane significantly more dense, you have to go pretty darn cold (well below your LOX temps), and it's probably not worth hydrogen complexity for a fuel with an ISP like methane.
** - Fuel density is the density of the fuel alone. Bulk density is the density of the fuel plus stochiametric amounts of liquid O2.
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NASA is paying for the research through a contract with ATK. XCOR is a subcontractor.
See, XCOR can't make money flying their rocket-planes around so they have to have government contracts to foot the bills. It was like this before the X-prize and will remain to be.
Now the X-prize itself and the X-cup? Yes, cool. But credit where credit is due. This is NASA research, not X-Prize stuff.
Oh, forgot to mention: this assumes that the tanks aren't pressurized beyond the vapor pressure from the fuel (i.e., we're dealing with turbopump-driven rockets). Increasing pressure means a simpler turbopump (or even no turbopump) and denser fuel, but it gives you heavier tanks. Now, the pressure can help support the weight of the rocket better, but you only need so much structural support. In fact, I like SpaceX's notion for rocket design: when unpressurized, the rocket has just enough strength to be transported and brought into launch configuration, but not to withstand the forces of launch. Pressurization gives it the strength to launch.
Speaking of pumps -- what do others think of the flometrics design? I have to say, I like it.
Yes, I've read a poem. Try not to faint.
Actually, the gas that makes flatulence stink is hydrogen sulfide. There's not enough to hurt you in the average fart, but it's still pretty poisonous, and it can build up to dangerous levels in the manure pits from animal farms. Methane itself, CH4, is odorless.
Sure you could do that... if your goal was to simulate the blast effects of a small nuclear explosion.
Different kind of risk.
The risk being talked about here is program risk... ie... the risk that using unproven technology will result in cost and schedule impacts to the project due to unforeseen problems. Not the risk of things going boom (although that can impact cost and schedule too... XD) Using proven, well-understood technologies reduces risk.
Think of it this way... if you're given a task to develop a program for $C dollars inside of Y months, are you going to use a well-established programming language or are you going to go with some new half-developed (but really nifty) one where you're playing debug the compiler as you work on your project?
Nope. It's so that the hearing impaired can enjoy them, too.