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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.
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.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
'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.
Yes, I've read a poem. Try not to faint.
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.