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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.
I am the one true god. However, as an atheist, I don't believe in myself. I guess I have a self-esteem problem.
...as in the completely undefined "technology risk".
(I mean, as in, let me go combine hydrogen with carbon and oxygen, and see what happens......)
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Guess he meant the smell of 'Natural' Methane.
If the astronauts run out of rocket fuel and get stranded they can always eat beans.
...and the cow jumped (?) over the moon...
I actually have a crapload of methane to donate, whom do I contact?
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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.
Having one organization, with one budget (NASA) works fine when you've got a big enough budget. However, politics and manpower constraints limit the number of avenues you can explore. Like with computers, having a monolithic space technology architecture can lead to a single point of failure.
What if a component is outlawed, or becomes extraordinarily expensive to produce? You end up with mountains of unusable applied technology.
This test demonstrates that the practical science behind space flight is getting diversified, and that can only be a good thing for ensuring the future of space flight.
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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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If we develop methane engine technology, could it possibly be used to return a space mission from planets with an abundance of frozen methane?
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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.
the smell is added so you can detect leaks.
Same reason god made farts smell - for the benefit of others.
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.
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Bison are starting to replace cows as a reliable meat source
.019% of the global market. I wouldn't worry about methane production.: for every bison being raised for meat, there are 5,200 cattle.
I'm sure they are, for small-scale organic ranchers catering to prestige restaurants. For the other 99.98% of the market, cattle are still king. Compare the numbers: roughly 1.3 billion head of cattle worldwide (100m in the US), compared to only 350,000 bison remaining in the world, with 250,00 being raised for meat.
That means that bison have about
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Another chemical engine. Been there, done that. Where are all those cool nuclear and ion engines I've been reading/hearing about for the last 30 years? You know the ones that promised us that mars was a couple weeks away and Jupiter was just a couple of months?
We tried out that ion engine a few years ago. If I remember it worked perfectly. Why haven't we put that in to service. The last probe we launch, pluto express, still used the tried and true brute force approach. It will take it about 20 years to get there. Where if we had strapped a nuclear powered plasma rocked they have been testing for the last 20 years I could already be bitch'n about how dull pluto is.
Come on guy's you've had the plasma rocket in a bottle for 10 years. Lets take it up, strap it to something, and see what the bitch can do.
Yes, I know nuclear plasma and ion can't get us off the ground so we'll still need chemical for that, for now. And I know you have to crawl before you can walk, but we've been crawling for 60 years now. Hell, we are still using the same basic technology that the nazi's where lobbing into London.
Let's get off the can and do something new for once.
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One of the nice things about methane (like LOX, and unlike kerosene or for practical purposes hydrogen) is that it's potentially self-pressurizing; keep the tank at the right temperature, and you can maybe dispense with the pumps entirely. Depending on your cost-sensitivity and the performance you're trying to hit, this might or might not be a big win...
Here's a link to an old plan for Mars operations leveraging the ease of obtaining methane and oxygen on Mars.
I am the one true god. However, as an atheist, I don't believe in myself. I guess I have a self-esteem problem.
Someone I know refers to it a "cow-milker" :-P
I think it is interesting, huge weight savings over a pressure fed with none of the high-speed parts of a turbopump. Flowmetrics wasn't the first to come up with the idea although they were the first to put it on a rocket and have patented several ideas relating to it. I'd like to see it running in a bigger concept than the SDSU rocket though. (Steve and Carl, faculty advisors for the projects work at Flowmetrics)
(They were pumping martinis at the Joint Propulsion Conference 2 years ago... very nice... and yummy)
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.
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Now, is "crapload" the metric unit?
At atmospheric pressure, methane freezes at a temperature about half a kelvin above that at which oxygen boils (about 90.7 kelvins and 90.2 kelvins, respectively, if I've looked things up correctly).
:) It's hard enough to design systems with two tanks. Designing a methane/LOX system with one? Perhaps it's counterintuitive to many, but at the *very* least, it would be *significantly* more difficult, but I suspect it would not even be possible.
Obviously, I know nothing about the operational pressure ranges, but one can easily infer that mixed-phase flows would likely result if you tried to use both from a single tank. I wouldn't want to see what that would do to a rocket engine turbopump. (Well, actually, since high-speed cameras are fairly cheap these days... um...)
Rocket science is already rocket science.
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?
That appeared to me to be a nice illustration of "shock diamonds".
:)
You can get some really interesting designs out of high-speed flows, especially when you throw in some bright combustion.
I am partial to US technology in most matters but South Korea successfully tested a 20,000lb thrust methane engine last year. I believe that Japanese have something similar.
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Great info! I just want to add, because people tend to forget, that Isp and Thrust are related but separate quantities. Heavy hydrocarbons and polymers are good first-stage propellants because they give high thrust (F=ma). They use the big thrust to get up off the pad, then drop those stages for the higher-Isp propellants.
Nope. It's so that the hearing impaired can enjoy them, too.
>Does anybody have any idea what this guy's talking about?
:-)
It isn't rocket science
The most important concept being taken for granted here is "specific impulse" or I(subscript)sp. It's pounds (force) of thrust divided by fuel burn rate in pounds (weight) per second. If you have an Isp of 300, then (oversimplifying outrageously) you'd use 1/300th of your fuel to hover for a second.
Higher Isp is very good. It appears in an exponent in the "rocket equation" (see Wikipedia). Small improvements make big differences in what you can accomplish. To get a high Isp for a given energy content, you want the fuel to be really really light.
One tradeoff is that the lightest fuel we have is hydrogen, which takes up ridiculous amounts of room, which means the tanks are larger and heavier. Plus you have the fun of pumping and storing something only 20 degrees from absolute zero. Sometimes a denser fuel with lower Isp gives you a better system design.
The Saturn V first stage burned kerosene and oxygen. It didn't have to lift its own weight very far. The upper stages had to be light and were hydrogen/oxygen.
Here's why.
Isp relates pretty directly to exhaust velocity. The difference is a unit conversion and some small correction factors.
Speed and force are separate ideas. Thrust is proportional to Isp *times the mass flow rate*. Throwing something heavy out the exhaust gives you more kick, but lifting and carrying something heavy is inefficient.
Ion drives show the tradeoff really well. They have spectacular Isp but the mass flow rate is a trickle. They have tiny amounts of thrust, but great fuel efficiency.
Specific impulse is what you need for efficient deep space travel. Thrust is what you need in order to correct the mistake of being on a planetary surface.
The bottom line is that NASA has rocket engines that can do everything they want. The relevant point is, different rocket engines do some tasks better than others. Methane has its selling points, which the article notes, but it doesn't simply put all other fuels to shame or anything like that.
NASA has wanted to have a methane engine option for quite a while, but since they have other functional options, they haven't been willing to take money away from other projects to develop it. It's a risk in the sense that it's not a proven design (see my final two paragraphs). As such, they haven't made a commitment to it for any particular project. Now they've finally funded ATK (who sub-contracted X-Cor) to develop the engine, I believe with funding from the Constellation program.
The first studies that NASA did for the Orion CEV had it using a methane/oxygen engine for the extra performance. However, because of the timeline involved and the challenge in getting reliable performance from a non-hypergolic engine in deep space, they chose the safer and cheaper route from an engineering perspective of using a proven hydrazine fueled engine (from the Boeing Delta 2 upper stage) like the shuttle and apollo craft. It sounds like a methane engine may still be used for the new Lunar Surface Access Module (lander), which is on a slower development timeline than the Orion, and as an upgrade to the CEV.
I want to note that almost all flight-restartable rocket engines (off-hand, the only exception I know of is the old Saturn V J-2 second stage engine) use hypergolic fuels. Hypergolics are fuels which spontaneously ignite when combined. The shuttle uses methyl-hydrazine and nitrogen tetroxide, which has a performance not far below kerosene and oxygen, the major drawback being its instability and toxicity.
The reason for accepting the drawbacks of hypergolics is they ignite with incomparable reliability. Before NASA is willing to commit to having a manned mission 150,000 miles from earth depend entirely on a non-hypergolic engine, they have to be absolutely sure that when they pour frigid oxygen and methane together together in the cold of space and throw a spark that it will ignite reliably and controllably. You can't just send an astronaut back there with a Zippo and a can of carb cleaner and hope for the best.