Critical Milestone in Liquid Oxygen-Liquid Methane Engine

[rlb2]

<font color="yellow">NASA, industry and the U.S. Air Force have achieved a major milestone in the development of next-generation spaceflight technologies, successfully completing a 103-second hot-fire test of an engine fueled by liquid oxygen and liquid methane. <br /><br />"As a result of these tests, NASA engineers have learned a great deal about different configurations for LOX-methane propulsion systems," said David Stephenson, project manager for the Radial Segmented Launch Vehicle at the Marshall Center. The benefits of LOX-methane engines, Stephenson said, stem from their strong performance in supporting missions with heavy payloads. "Compared to engines powered by traditional storable hypergolic liquid fuels, LOX-methane engines have additional capabilities in supporting a large spacecraft's descent and landing on a planetary surface."<br /><br />http://www.spaceref.com/news/viewpr.html?pid=19608<br /></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[barrykirk]

This is very encourging news indeed.<br /><br />NASA needs an alternative to LH2/LOX, SRB, and hypergols.

 

[john_316]

Yeah saw that at spacedaily.com as well...<br /><br /><br />3 more tests they say and they are confident they have mature analysis criteria (R&D/QA/QC) in place. Sounds like they have been working on this behind closed doors when they are pretty advanced in the program like this....<br /><br /><br />What makes it more interesting is that part about a flight test article. (Ummmm means perhaps after testing and some more developing a production version will be ready) <br /><br />Again sounds like advanced stages to me.......<br /><br /><br />Anyone know what versions of engines they have been working on? Any of them from former DC-X designs?<br /><br /><img src="/images/icons/smile.gif" /><br /><br />

 

[scottb50]

The biggest problem is the ISP of methane compared to Hydrogen, then there is carrying virtually useless Carbon. Might be a good way to get carbon out of the atmospsphere though.<br /><br />When it gets to the defining reaction Oxygen and Hydrogen combine. I see little reason to carry Carbon to carry the Hydrogen, Carbon is nearly as heavy as Oxygen.<br /><br />That's why LH2/LOX is the only reasonable alternative. transport it as water and use solar power to convert it. <div class="Discussion_UserSignature"> </div>

 

[henryhallam]

<font color="yellow"> That's why LH2/LOX is the only reasonable alternative. transport it as water and use solar power to convert it. </font><br />The energy requirements are just ridiculous. Wouldn't it be better to transport them cryogenically and spend the energy budget on active refrigeration? After all even if you did electrolyse water you'd still have to liquify the H2 and O2 so you'd be carrying most of the same equipment.

 

[rlb2]

NASA needs an alternative to LH2/LOX, SRB, and hypergols. <br /> <br />I agree, more mass to kick out the rear end and less coolling system needed Cryogenics to cool the liguid hydrogen but what is even more interesting is:<br /><br /><font color="orange">engines have additional capabilities in supporting a large spacecraft's descent and landing on a planetary surface." <br /></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[john_316]

Sorry Mclumber1 When I was in the Navy I never worked nuclear power but I am aware of cavitation and such as I was in the anti-submarine field.<br /><br />But I assume as you said using a basic turbopump you could reduce cavitation then again I dont know much about the pumps employed on these type of motors. So for me to make any asumptions isnt a good idea for me.<br /><br />Now is cavitation a specific criteria in such testing for a pump on these motors? I dont know if there is worry on backfeed in the line or that either with the fuel or the gas that pressure feeds the system.<br /><br />Now are they using carbon for the pressure feed system for the methane? Or both the Methane and LOX?<br /><br />Wouldnt Nitrogen or Helium feed lines be a stable to do that as well? Not sure on the reactants of those gases with Methane or LOX in a high pressure system. Any thoughts by anyone knowledgeable would be enlightning.<br /><br /><br /><img src="/images/icons/smile.gif" /><br /><br />

 

[rlb2]

<font color="orange">Wouldn't it be better to transport them cryogenically and spend the energy budget on active refrigeration?<font color="white"><br /><br />Don't know if this can be done with the pressure needed but imagine storing liquid methane in methane hydrides like at the bottom of the oceans, then you can transport water and fuel at the same time....good candidate for a moon landing...</font></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[rlb2]

<font color="orange">Again sounds like advanced stages to me.......<font color="white"><br /><br />What gives that away is the work they are doing with the Air force....it does sounds like a Phantom or Skunk works project...</font></font> <div class="Discussion_UserSignature"> Ron Bennett </div>

 

[scottb50]

You can use the same electricity to liquify Hydrogen and Oxygen or you could use Hydrogen and Oxygen to run fuel cells to produce the electricity. If you re-use Modules you could refill them as needed. I would also think you could use gasses for the majority of uses, liquids would be needed for high powered propulsion but thrusters to fuel cells work just fine on gas.<br /><br />I also don't see where the energy requirements are any more rediculous than any other means of power. Water has to be one of the easiest materials to carry. Methane, kerosene and hypergolics would need would all be heavier and LOX and Methane would need cryogenics anyway.<br /><br />One advantage in Space is much simpler insulation requirements and the other is the abundance of solar energy. Why carry heavy insulated tanks when you could carry much more water to LEO? <div class="Discussion_UserSignature"> </div>

 

[john_316]

Scott so your saying if we lift 90-125 tons of water to space and catylize it there and make electricity and fuel from it that would be better than using LOX and Methane? <br /><br />How much water is it going to take to make that LOX and LH2 needed for off planet use?<br /><br />Just a few Q's for you..<br /><br /><img src="/images/icons/smile.gif" /><br />

 

[propforce]

<font color="yellow">How do these turbopumps get around cavitation? Working in the nuclear navy, this issue was really harped on in power school. To get rid of cavitation in a high speed centrifugal pump with high temperature water, we had to increase the pressure at the eye of the impeller to prevent cavitation. Do they do the same thing with LOX and LH2, pressurize the tank and then force feed the fluid into the pump to prevent cavitation? </font><br /><br />This particular engine is a "pressure-fed", meaning that they do not use turbopumps to increase its pressure. <br /><br />But I think your question is regarding to the rocket engine turbopumps in general. We do this by design pump's inlet diameter (inducer) and shaft operating speed such way to stay out of cavitation range, based on specified pump inlet propellant NPSP (net positive suction pressure). <br /><br />An excellent article on liquid rocket engine turbopump can be found here:<br /><br />http://www.engineeringatboeing.com/articles/turbopump.htm<br /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">...Water has to be one of the easiest materials to carry. Methane, kerosene and hypergolics would need would all be heavier ....</font><br /><br />Where are you getting these stuff from? <img src="/images/icons/laugh.gif" /><br /><br />Methane, kerosene and mono-methyl-hydrazine are all <i>lighter</i> than water. Nitrogen tetroxide is heavier than water. <br /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

Yes, it's complicated in the sense that one needs to design a new turbopump specifically for methane. But it's not as difficult as the LH2 because LCH4 (liquid methane) has a higher density therefore easier to pump through than LH2. Kerosene is easiest because it has a density that closer to LOX thus making the design of turbopump easier. <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">One advantage in Space is much simpler insulation requirements and the other is the abundance of solar energy. Why carry heavy insulated tanks when you could carry much more water to LEO?</font><br /><br />I can see the merit of what you're proposing, using water as a method of long term storage of H2/O2 propellant in space, e.g., a propellant depot in orbit. The trouble with storing LH2 is with the continuous boil-off due to the heat continually drawn in from structures. LOX has a lesser problem because its boiling point is ~100 deg. F higher than LH2.<br /><br />Storing water has a different problem, that is keeping it from freezing. But with solar panel with 'unlimited' heat source available, it's a lesser problem.<br /><br />The trouble you may encounter is the "system complexity" of separating water to gaseous H2 and O2, then needing the pumps to pressurize, then chill them down to cryogenic temperature and store them. That system may just be too complex for today's robotic space technology, even though it's common industrial practice on Earth today. Nobody wants to transport GH2 and GOX, they takes too big of lines and tank volumes -- even for the Mars direct Space Truck.<br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"I see little reason to carry Carbon to carry the Hydrogen"</font><br /><br />For starters, methane is almost as good hydrogen carrier as water (measured by percentage of liquid's mass being H). Second, once primitive moon base is up and running, carrying oxygen to there is coal to Newcastle. Regolith is loaded with oxygen and it's one of the easiest lunar commodities to extract. Third, in order to become more sophisticated, selfsufficient the base needs fodder to jumpstart viable carbonchemistry. Regolith contains only trace amounts of C so at least initially it has to be shipped from Earth.<br /><br /><font color="yellow">"That's why LH2/LOX is the only reasonable alternative. transport it as water and use solar power to convert it."</font><br /><br />If you want completely solar powered propulsion with thrust levels higher than electric thrusters provide then ditch the water, put only LH2 in the tanks and enjoy close to 1000s Isp of solar thermal propulsion.

 

[tap_sa]

<font color="yellow">"Kerosene is easiest because it has a density that closer to LOX thus making the design of turbopump easier."</font><br /><br />Doesn't the mixture ratio affect things too? LOX is about 2.7 times denser than methane, and LOX-LCH4 mixture ratio is about 3, so about same volume of both propellants should be pumped into combustion chamber. This would mean a good chance to fit LOX and LCH4 pumps of almost equal size on a common shaft, no?

 

[propforce]

<font color="yellow">Doesn't the mixture ratio affect things too? LOX is about 2.7 times denser than methane, and LOX-LCH4 mixture ratio is about 3, so about same volume of both propellants should be pumped into combustion chamber. This would mean a good chance to fit LOX and LCH4 pumps of almost equal size on a common shaft, no? </font><br /><br />You make a good point. Volumetric flow wise, LCH4 and LOX is very closely matched. Vapor pressure of LCH4 and LOX are also close which means they can be designed with the same shaft speed. However; a common shaft turbopump design is more of a Russian heritage rather than the U.S., though I wish we learn more from the Russians and do more of this type of design though. Afterall, we learned the oxidizer-rich combustion technology and nozzle channel wall cooling from them, why not a single-shaft turbopump? <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[scottb50]

It will take less water than any other propellant, the ISP of LH2/LOX is higher than other alternatives. The point being somehow you have to have enough propellant to do what needs to be done and the onlny way to get it into LEO is to carry it from the surface, regardless of its makeup.<br /><br />Another advantage of water is what is used for producing electricity can be re-used indefinitely, once in orbit it does not have to be replaced like batteries.<br /><br />How much water is needed? It depends on what you want to do and where you want to go, either way if you are going to do it water offers the safest, least expensive and lightest means of producing both electrical and propulsive power in Space. <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

<blockquote><font class="small">In reply to:</font><hr /><p><font color="yellow">You make a good point. Volumetric flow wise, LCH4 and LOX is very closely matched. Vapor pressure of LCH4 and LOX are also close which means they can be designed with the same shaft speed. However; a common shaft turbopump design is more of a Russian heritage rather than the U.S., though I wish we learn more from the Russians and do more of this type of design though. Afterall, we learned the oxidizer-rich combustion technology and nozzle channel wall cooling from them, why not a single-shaft turbopump?</font>p><hr /></p></blockquote><br /><br />This may be a case of "close is not good enough". <br /><br />A working rocket engine is finely balanced between an bomb and fuel sprayer. <div class="Discussion_UserSignature"> </div>

 

[webtaz99]

<blockquote><font class="small">In reply to:</font><hr /><p><font color="yellow">It will take less water than any other propellant, the ISP of LH2/LOX is higher than other alternatives. The point being somehow you have to have enough propellant to do what needs to be done and the onlny way to get it into LEO is to carry it from the surface, regardless of its makeup.<br /><br />Another advantage of water is what is used for producing electricity can be re-used indefinitely, once in orbit it does not have to be replaced like batteries.<br /><br />How much water is needed? It depends on what you want to do and where you want to go, either way if you are going to do it water offers the safest, least expensive and lightest means of producing both electrical and propulsive power in Space.</font>p><hr /></p></blockquote><br />Water can only be used for electricity once more energy than it can produce has been added. So using it for electricity is wateful compared to other methods (which would be needed for splitting water anyway).<br /><br />And for propulsion, ion or plasma engines will provide much better ISPs than any combustion process. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

>Second, once primitive moon base is up and running, carrying oxygen to there is coal to Newcastle. Regolith is loaded with oxygen and it's one of the easiest lunar commodities to extract. Third, in order to become more sophisticated, selfsufficient the base needs fodder to jumpstart viable carbonchemistry. Regolith contains only trace amounts of C so at least initially it has to be shipped from Earth.<br /><br />I've read that ammonia is an even better option than methane to provide H2 for use with Lunar O2. Mainly because ammonia can be kept liquid in near-earth space via passive means due to it's high boiling point. Methane is slightly harder to liquify than LOX. The moon is very short on nitrogen as well - and astronauts need N2 to breath. It'll be a long time before space industry has gotten to the point where they need raw carbon beyond what we're already sending in the form of food.<br /><br />This site talks more about storability and ammonia, though their focus seems more geared towards providing storable fuel to satelites than high-isp fuel for manned ventures. http://www.permanent.com/t-mikesc.htm

 

[propforce]

<font color="yellow">This may be a case of "close is not good enough". </font><br /><br /><br />How's so ?<br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

<font color="yellow">"Methane is slightly harder to liquify than LOX."</font><br /><br />It's the other way around, at ntp methane freezing and oxygen boiling point are about the same. Other than that I agree what you wrote about ammonia/nitrogen. N will be needed as buffer gas, food production etc.

 

[tap_sa]

<font color="yellow">"Afterall, we learned the oxidizer-rich combustion technology and nozzle channel wall cooling from them, why not a single-shaft turbopump?"</font><br /><br />Trade them the integrated powerhead 'full flow' to get single shaft tech? <img src="/images/icons/smile.gif" />