A Simple Question to the Rocket Scientists

[arobie]

How simple or hard would it be to design a rocket engine for the propellant CH4/O2? What would be the difficulties in doing so?<br /><br />[Edit]Oops, I meant to say CH4/CO2 for the propellant.

 

[nacnud]

Methane? I think JAXA is trying it.

 

[henryhallam]

I think it would have relatively low Isp and a sooty exhaust, leading to contamination of engine parts. Better to split the CO2 electrically or chemically, methane/lox is quite a good propellant combination.

 

[najab]

I really didn't do too well in chemistry, but would methane even burn in carbon dioxide?

 

[henryhallam]

Based on a quick experiment I just did with a natural gas stove and a fire extinguisher, I'm going to go with "no". <img src="/images/icons/wink.gif" /><br /><br />Not many things will burn in CO2, some of the more reactive metals being an important exception. I dread to think what the Isp would be like for those, though.

 

[arobie]

<font color="yellow">I really didn't do too well in chemistry, but would methane even burn in carbon dioxide?</font><br /><br />Hmmm....That could be a problem. <br /><br />Ok then, I'll go back to:<br /><br />What difficulties, or lack there of, would there be designing and building a CH4/O2 rocket engine?

 

[drwayne]

I read where the RL-10 was tested some years ago with CH4/LOX.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[arobie]

drwayne,<br /><br />Do you know the results or where I could find the results of that?

 

[drwayne]

I have not found definitive figures on the RL-10 experiments. I have seen figures for ISP thrown about in the range of 300 - 400 seconds, but most of these pop up in peoples proposals, so you have to take it with a grain of salt.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

Example:<br /><br />http://www.aeronautics.ru/archive/reference/Russian_Space_Engines/Russian_Space_Engines_21.htm<br /><br />http://yarchive.net/space/rocket/fuels/fuel_table.html<br /><br />http://www.astronautix.com/props/loxlch4.htm<br /><br />Wayne<br /> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[arobie]

Thank you, that's excellent! <img src="/images/icons/cool.gif" />

 

[drwayne]

http://www.bonus.com/contour/spsattle/http@@/lifesci3.arc.nasa.gov/SpaceSettlement/Nowicki/SPBI1LF.HTM<br /><br />Is a Bruce Dunn table that has some interesting data, including oxidizer / fuel ratio<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[Blur]

CO2 is not an oxidizer. It is oxidizED. It would be like using H2O for your fuel just because it has hydrogen in it. (H2O=water)

 

[yevaud]

<blockquote><font class="small">In reply to:</font><hr /><p>Based on a quick experiment I just did with a natural gas stove and a fire extinguisher, I'm going to go with "no".<p><hr /></p></p></blockquote><br /><br />Excellent! An experimentalist! <br /><br /><img src="/images/icons/wink.gif" /><br /> <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[tap_sa]

<font color="yellow">"CO2 is not an oxidizer"</font><br /><br />CO2 can be an oxidizer if there is powerful enough reducing agent to burn, such as magnesium.<br /><br />Experimental CO2/Mg rocket engine

 

[najab]

><i>It would be like using H2O for your fuel just because it has hydrogen in it.</i><p>I can't off hand think of a combination that would let you use water as your fuel, but it can make a handy oxidizer - think powdered lithuim.</p>

 

[najab]

Though, thinking about it, the exhaust of a lithium-water rocket would be hydrogen, add some oxygen and there you have it. Water as both fuel and oxidizer.

 

[Blur]

I know chemistry. Sodium will react with water, too. Don't confuse the guy- stick with the basics for a question like this.

 

[drwayne]

I probably drove him/her away with all the ISP links.<br /><br /><img src="/images/icons/frown.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[tap_sa]

He/she said 'stick with the basics'. In rocket science I_sps <i>are the basics</i> <img src="/images/icons/wink.gif" />

 

[spacester]

<font color="yellow">I probably drove him/her away with all the ISP links.</font><br /><br />I seriously doubt it. Arobie is very curious and a quick learner. It's more likely that he's putting the numbers to good use.<br /><br />The CO2 discussion is my fault. It's a typo in one of my Mars Settlement posts, I changed it to O2 in a later post.<br /><br />The point of Arobie's initial question is to determine the difficulty of developing engines to utilize all-Martian derived propellants. I'm happy to see it's not completely new to rocket science. I tried briefly to find the info at Mark Wade's site but came up empty.<br /><br />Thanks for the links, drwayne! <div class="Discussion_UserSignature"> </div>

 

[drwayne]

My observation about the ISP links by the way was me making fun of me.<br /><br />You may have noticed, when there is a topic of some interest to me, I tend to get "excited" and shotgun information in sometimes badly dis-organized ways.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[arobie]

Drwayne, <br /><br />Those links with Isp, thrust, and fuel ratios are exactly what I was looking for. Your shotgunning of information is appreciated. It's needed information. How would I calculate anything using the engine if I don't know it's stats? I'm asking about CH4/LOX engines out of application of the information rather than just curiosity. <img src="/images/icons/cool.gif" /><br /><br />To all again, <br /><br />Don't worry about going over my level. That's how I learn. If I don't understand something said, I'll either look it up, or ask about it. <img src="/images/icons/wink.gif" /><br /><br />Just to tell you a bit about myself, I'm a highschool student in the 10th grade. I take chemistry next year, but what's been said in this thread has not gone over my head. I'm very curious like Spacester said and also a quick learner, I soak up <b>alot</b> from these forums. I like to figure things out.<br /><br />As to my knowledge about rockets, I know the basics. I understand Isp's (and the rest of the information in the links from Drwayne) and the rocket equation. I'm always looking to learn more though...such as the basics to rocket engine design. So if this thread were to now migrate over to designing a rocket engine with the propellant CH4/LOX, I would not be upset.<br /><br />Oh yeah, and I'm a guy to clear up any confusion on that. <img src="/images/icons/smile.gif" /><br /><br />Spacester,<br /><br />I'm glad you found this thread. I'm sorry to dissapoint you, but I have not been able to put this information to use <b>yet</b>. I've been at school all day...disecting pigs in biology(Whoa! The brains were awesome!), talking about Hitler and Mussolini in history, and building polyhedrons (for my group, an icosahedron with twenty triangle-based pyramids -one on each side of the icosahedron-) in geomety are a few of the more interesting things that I did today. <br /><br />I promise, I didn't ask about this without intending to use any information I gained. I'll put it all to use. <img></img>