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'."
So this is why UFO's come to earth and probe our cattle... I guess in the next decade or so you won't see countries being invaded for oil, but farmland being taken over for fuel and a glass of milk.
'Cows' make milk. At the end of their useful milk-producing life they're WAY over the 30-month limit for sending them to slaughter. The animals used to make beef are almost exclusively bulls because you only need one, (or possibly two for genetic diversity) on your farm (as they're only use is getting the cows pregnant) and you send the rest of them off to become burgers (again, before they're 30 months old) so they don't get to produce much methane anyway.
Bison are starting to replace cows as a reliable meat source
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.019% of the global market. I wouldn't worry about methane production.: for every bison being raised for meat, there are 5,200 cattle.
The fuel has higher specific impulse than kerosene and oxygen, but until now has been thought to have too much 'technology risk'
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.
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 [xcor.com]. 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.
No, it has more to do with the subcontract they have with ATK to do research for NASA LINK.
Good catch. But it's still not being developed for a traditional launch system. According to their website, this engine would be used for the lunar -> LEO transfer stage on the CEV. Which again makes the thrust to weight ratio less important, and again non-comparable to kerosine engines. (From what I understand the Apollo Service Module used a hydrazine engine for the transearth injection.)
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.
Agreed. However, I don't have the actual Thrust to Weight ratios for the XCOR engine, so all I can do is point out the differences in their thrust. If you have the actual ratios, feels free to chip in.
But it's still not being developed for a traditional launch system.
CEV/Constellation is becoming our "traditional" launch system.
If you have the actual ratios, feels free to chip in.
Hehe... no I don't. XCOR is keeping the numbers close to their chest. As they should... the numbers belong to NASA under contract. But you can back out a rough guesstimate since they gave you the thrust.
CEV/Constellation is becoming our "traditional" launch system.
No, they're the new hotness! *sizzle*:P
Sorry, when I refer to "traditional launch system", I mean a vertical take off rocket. The CEV program covers a huge number of vehicles and engines. What I'm referring to is that the methane engine is not planned for use as the first stage of a vertical takeoff; which is the area where kerosine is most commonly used.
Hehe... no I don't. XCOR is keeping the numbers close to their chest. As they should... the
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
That's misleading. "This engine" is strictly a prototype so they can develop a much larger version. Comparing a production engine with an early, heavy in development prototype simply does not make sense. From the article, "The 7,500 lbf engine is the first of its kind...", and, "Currently, the engine is a workhorse prototype...". I don't see what their target thurst is, but one can assume it's much larger than 7,500lbf.
I don't see what their target thurst is, but one can assume it's much larger than 7,500lbf.
7,5000 lbf is the target for this engine. It builds upon the 50 lbf XR-3M9 [xcor.com] and 10,000 lbf 5M12. As pointed out by another poster [xcor.com], XCOR claims "the new Orion Crew Vehicle main engine design will be an interpolation between these recent designs."
Additionally, XCOR is advertising their engine developments as a possible base for methane-breathing Jet engines that would work in Mars atmosphere. (A very interesting development, indeed!)
BTW, if you have the projected thrust to weight ratios, please share them. I hate having to use the thrust values, because it can be (as you said) misleading. Unfortunately, I don't have the values for the XCOR engine. What I can say is that LHOx > methane > kerosine in terms of specific impulse/efficiency. In terms of thrust to weight, the formula is exactly reversed where kerosine > methane > LHOx. There are very few cases where both the thrust to weight and specific impulse are high. (Orion Project and MPD thrusters [wikipedia.org] are the two I'm aware of.) Otherwise, they tend to be inversely proportional.
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.
Methane gas is utterly renewable. You can make it from shit [colostate.edu], literally, and without any special equipment [motherearthnews.com]. The only special thing you need is a way to compress it [repp.org] 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 [sodalitasart.com] which attempted to root my computer. No idea how successful it was, I'm off to go run defender and spybot.
Compressed natural gas is a common fuel used to power stoves on sailboats and fleet vehicles. You can buy it at the fuel docks at many marinas. Typically you exchange a tank, empty tank for full tank and pay about $20. The tanks look like steel SCUBA tanks and are filled to between 2400 to 3000 PSI. (about 200 BAR if you like metric) It really does need to be compress to 200 Bar or so to make it a usful otherwise the tanks are huge compared to the energy they contain. At 1 bar a small car might use 1 c
Well I'm not talking about the compressed/liquid, I'm just talking about compressing it beyond atmospheric for storage and use for cooking, welding, stuff like that. They actually make methane digesters that can be installed under your house and the outputs are processed waste and methane. The processed waste is now less nasty and can be used for fertilizer - humanure (as disgusting as the concept may be) is the most valuable fertilizer around. The methane could then be used for household purposes - it can
The fuel has higher specific impulse than kerosene and oxygen, but until now has been thought to have too much 'technology risk'.
Really, this is sweet. Not necessarily the rocket technology itself, but the fact that the X-Prize has accomplished what it was meant to do: Foster distributed research in space technology.
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.
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.
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.
Ion engines are very efficient, problem is they don't generate much thrust and therefore don't really help with "getting there faster". Deep space one [wikipedia.org] pioneered ion propulsion technology. Can't do nuclear propulsion like Project Orion [wikipedia.org] due to international treaties and what not. Basically anything other than chemical propulsion is experimental and no one is willing to foot the bill to make the technology mature.
I am partial to US technology in most matters but South Korea successfully tested [hobbyspace.com] a 20,000lb thrust methane engine last year. I believe that Japanese have something similar.
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.
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.
No, crapload is imperial. The metric unit is "ass ton", not to be confused with the imperial "asstonne", which is roughly equivalent to.9 ass tons and is exactly equal to a gross craploads.
FWIW, I think it's a good thing that companies like XCOR are exploring other engine options. NASA only targets developments that are useful to NASA, potentially leaving behind massive swaths of rocketry that could prove useful in the future. By having more third parties working on rocket technology, we're increasing the experience in the industry, lowering costs through economics, and hop
'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 [nasa.gov]) 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...)
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 sen
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:
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:
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.
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 [flometrics.com] design? I have to say, I like it.
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...
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 [sdsu.edu] 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)
>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 dif
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.
Armadillo Aerospace [armadilloaerospace.com] is considering exactly the same fuel [armadilloaerospace.com]. 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.
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?
Methane? (Score:5, Funny)
Re: (Score:2)
Re:Methane? (Score:4, Informative)
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
Parent
Little bit disingenuous (Score:5, Interesting)
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.
No (Score:5, Interesting)
No, it has more to do with the subcontract they have with ATK to do research for NASA LINK [xcor.com]. 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.
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Re: (Score:2, Funny)
Are they contemplating the Final Solution for trailer trash or something?
First they came for the trailer trash and I didn't say anything because I wasn't trailer trash.
Then they came for the phone sanitizers . . .
On the other hand it's a free ride into space. Maybe I'll get a mullet and rip the sleeves off my t-shirts or something. Take that Ansari.
KFG
Re:No (Score:4, Interesting)
Good catch. But it's still not being developed for a traditional launch system. According to their website, this engine would be used for the lunar -> LEO transfer stage on the CEV. Which again makes the thrust to weight ratio less important, and again non-comparable to kerosine engines. (From what I understand the Apollo Service Module used a hydrazine engine for the transearth injection.)
Agreed. However, I don't have the actual Thrust to Weight ratios for the XCOR engine, so all I can do is point out the differences in their thrust. If you have the actual ratios, feels free to chip in.
Parent
Re: (Score:3, Interesting)
CEV/Constellation is becoming our "traditional" launch system.
If you have the actual ratios, feels free to chip in.
Hehe... no I don't. XCOR is keeping the numbers close to their chest. As they should... the numbers belong to NASA under contract. But you can back out a rough guesstimate since they gave you the thrust.
Re: (Score:3, Interesting)
No, they're the new hotness! *sizzle* :P
Sorry, when I refer to "traditional launch system", I mean a vertical take off rocket. The CEV program covers a huge number of vehicles and engines. What I'm referring to is that the methane engine is not planned for use as the first stage of a vertical takeoff; which is the area where kerosine is most commonly used.
Re: (Score:2, Insightful)
Holy Christ, are we still allowed to do that? Why didn't I get the memo?
Now all we have to do is do something about the design goals and we're set.
KFG
Re:Little bit disingenuous (Score:4, Insightful)
That's misleading. "This engine" is strictly a prototype so they can develop a much larger version. Comparing a production engine with an early, heavy in development prototype simply does not make sense. From the article, "The 7,500 lbf engine is the first of its kind...", and, "Currently, the engine is a workhorse prototype...". I don't see what their target thurst is, but one can assume it's much larger than 7,500lbf.
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Re:Little bit disingenuous (Score:4, Interesting)
7,5000 lbf is the target for this engine. It builds upon the 50 lbf XR-3M9 [xcor.com] and 10,000 lbf 5M12. As pointed out by another poster [xcor.com], XCOR claims "the new Orion Crew Vehicle main engine design will be an interpolation between these recent designs."
Additionally, XCOR is advertising their engine developments as a possible base for methane-breathing Jet engines that would work in Mars atmosphere. (A very interesting development, indeed!)
BTW, if you have the projected thrust to weight ratios, please share them. I hate having to use the thrust values, because it can be (as you said) misleading. Unfortunately, I don't have the values for the XCOR engine. What I can say is that LHOx > methane > kerosine in terms of specific impulse/efficiency. In terms of thrust to weight, the formula is exactly reversed where kerosine > methane > LHOx. There are very few cases where both the thrust to weight and specific impulse are high. (Orion Project and MPD thrusters [wikipedia.org] are the two I'm aware of.) Otherwise, they tend to be inversely proportional.
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Mars exploration (Score:5, Interesting)
Old idea waiting on execution (Score:3, Informative)
Love the scare quotes.... (Score:3, Insightful)
(I mean, as in, let me go combine hydrogen with carbon and oxygen, and see what happens......)
Methane rocket (Score:5, Funny)
Wonderful! (Score:5, Informative)
Methane gas is utterly renewable. You can make it from shit [colostate.edu], literally, and without any special equipment [motherearthnews.com]. The only special thing you need is a way to compress it [repp.org] 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 [sodalitasart.com] which attempted to root my computer. No idea how successful it was, I'm off to go run defender and spybot.
Re:Wonderful! (Score:5, Funny)
M-
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Protestor sign of the future (Score:4, Funny)
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Re: (Score:3, Informative)
Re: (Score:3, Informative)
Really, this is sweet. (Score:3, Insightful)
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.
Um. Hate to bust your bubble (Score:5, Informative)
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.
Parent
Cattle powered (Score:5, Funny)
I can see it now - "Where do you stupid bovines think you're going? The mooooooooooon?"
Just a wild thought.. (Score:3, Interesting)
Yawn! (Score:3, Interesting)
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.
Re:Yawn! (Score:4, Informative)
Parent
Done already by South Korea (Score:4, Informative)
I am partial to US technology in most matters but South Korea successfully tested [hobbyspace.com] a 20,000lb thrust methane engine last year. I believe that Japanese have something similar.
Re:risk? (Score:5, Informative)
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Re:risk? (Score:4, Funny)
If the astronauts run out of rocket fuel and get stranded they can always eat beans.
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Re:risk? (Score:5, Informative)
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Re: (Score:2, Funny)
Same reason god made farts smell - for the benefit of others.
Re:risk? (Score:5, Funny)
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Re: (Score:2, Funny)
I actually have a crapload of methane to donate, whom do I contact?
Bumper sticker: Save Gas - Fart In A Jar
Metric or Imperial? (Score:4, Funny)
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Re: (Score:3, Funny)
Re:Metric or Imperial? (Score:4, Funny)
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Re: (Score:2)
See my post [slashdot.org] for an explanation.
FWIW, I think it's a good thing that companies like XCOR are exploring other engine options. NASA only targets developments that are useful to NASA, potentially leaving behind massive swaths of rocketry that could prove useful in the future. By having more third parties working on rocket technology, we're increasing the experience in the industry, lowering costs through economics, and hop
Interpretation of 'risk' (Score:5, Informative)
NASA uses a scale called Technology Readiness Levels (TRL [nasa.gov]) 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.
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They want it, not need it. (Score:3, Informative)
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 sen
Re:Why hasn't it been worked on? (Score:5, Informative)
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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Re:Why hasn't it been worked on? (Score:5, Informative)
Speaking of pumps -- what do others think of the flometrics [flometrics.com] design? I have to say, I like it.
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Re:Why hasn't it been worked on? (Score:4, Informative)
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Re:Why hasn't it been worked on? (Score:4, Interesting)
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 [sdsu.edu] 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)
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Re: (Score:3, Informative)
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 dif
Re:Isp vs. Thrust (physics) (Score:3, Informative)
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.
Speci
Armadillo too is considering methane (Score:5, Interesting)
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Re: (Score:3, Insightful)
Re:Risk? (Score:5, Interesting)
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?
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Re:Additional cost savings? (Score:5, Funny)
Sure you could do that... if your goal was to simulate the blast effects of a small nuclear explosion.
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