Space Storable Propellants

[halman]

spacester,<br /><br />Definitely, you have been thinking outside the box. The Sterno corporation will be thrilled to find out that they have a new lease on life! Of course, there will be some retooling involved, in order to produce cans in the 200 kilogram size.<br /><br />But seriously, you have a concept worth investigating. I believe I understand you to be saying that the paraffin would be warmed during the day cycle, until it is molten and about to combust, and then it is wrapped in insulation, to be exposed when the temperature in the habitat begins to drop below the survival level. I realize that paraffin can hold a tremendous amount of heat energy, and radiate it back slowly.<br /><br />As far as using it for rocket fuel, I guess that it could be liquified, and then atomized, so as to allow complete combustion. <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[willpittenger]

What about temperatures in the shadows of Earth and the Moon? Moving in and out of shadows was the main reason why Hubble's original solar panels had to be replaced. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[propforce]

Spacester,<br /><br />You know the word "paraffin" is just a chemistry word that desribes a family of "linear chain" hydrocarbons, don't you?<br /><br />As such, it goes from the simple methane to the regular unlead gasoline (octane), polyethylene (plastic), and onto candle wax, etc. <br /><br />Is there anything more specific that you have in mind?<br /> <div class="Discussion_UserSignature"> </div>

 

[spacester]

Yes, I know that. That's why I have used the word 'wax' several times expecting the organic chemists among us to realize I'm talking about Pure Paraffin, candle wax.<br /><br />By "linear chain", you refer to normal alkanes, not isoalkanes aka isoparaffins, right? <img src="/images/icons/wink.gif" /><br /><br />To answer another question, as a rocket propellant, the idea would be to pour molten wax into hybrid motor casings, casting new delta V capability on demand from a bulk, multi-use commodity. LOX/Wax hybrid rockets would provide adequate specific impulse for hopping around the lunar surface, with very simple storage and operations logistics.<br /> <div class="Discussion_UserSignature"> </div>

 

[propforce]

<font color="yellow">To answer another question, as a rocket propellant, the idea would be to pour molten wax into hybrid motor casings, casting new delta V capability on demand from a bulk, multi-use commodity. LOX/Wax hybrid rockets would provide adequate specific impulse for hopping around the lunar surface, with very simple storage and operations logistics. </font><br /><br />Sounds like you're referring to the concept developed by the Standford University. I visited them and watched a "live-firing" at the nearby NASA facility. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

I can see a benefit in a hybrid motor using parafin in that it can be stopped in an emergency by shutting off the Oxygen flow. As for restart I would think the melting and resolidification would make it pretty hard to determine required burn times due to the random surface area available. Another consideration would be the reduced performance of hydrocarbons that are solid at relatively high temperatures. Light a candle or a can of sterno and it burns a lot slower than if you throw a match at a puddle of kerosene and even slower that if you throw it in a puddle of gasoline. <br /><br />I would also think the same problems encountered with the rubber used in the SS-1 would be a problem in a hybrid motor, though because it would be liquid it would have a better chance of combusting at lower temperatures than creating chunks that could clog nozzles.<br /><br /><br /> <div class="Discussion_UserSignature"> </div>

 

[vulture2]

Just my opinion, but if the vehicle is going to have any sort of cryogenic cooling for oxygen, then little more complexity is required to use methane as the fuel, and the combination is more energetic than heavier hydrocarbons. If cooling is not available and the vehicle is unmanned and not returning to earth, hypergolics are reasobable. But for manned or reusable systems, the cost of dealing with toxic propellants is _much_ higher than it at first appears; there are complex procedures, protective equipment, training, contingency planning, decon, etc. If cryogenic cooling is not available N2O and propane would be a good choice; they are stable (unlike peroxide) and nontoxic and the lower cost of operation is well worth the performance hit.

 

[scottb50]

I would think you could operate on the moon with Hydrogen and Oxygen gas without cryogenics, just like you could use station keeping thrusters in orbit or Space. Leaving the moon to lunar orbit and returning would require liquid Hydrogen and Oxygen, but if you could fill it on the moon and also in orbit yo would not need cryogenic capabilities in the vehicle itself.<br /><br />methane is the simplest hydrocarbon, an atom of Carbon and four atoms of Hydrogen, butane is four Carbon atoms and 10 Hydrogen atoms, octane is eight atoms of Carbon and 18 atoms of Hdrogen. Nitrous oxide and propane would need to pressurized and the Nitrogen and Carbon are only along for the ride. Not only do you have to have containers strong enough to carry the propellants you have to carry.<br /><br />Nitrogen weighs 14.0067 g/mol, Oxygen 15.9994 g/mol and Carbon 12.0107 g/mol. Hydrogen weighs 1.00794 g/mol. If you plan to use methane as a fuel you would need two atoms of Oxygen to accept the Hydrogen atoms in a perfect world. Normally you get carbon dioxide produced also, explaining the difference in ISP compared to Oxygen and Hydrogen. The same holds true with using nitrous oxide you still have to deal with the Nitrogen, it competes with the Hydrogen for the Oxygen.<br /><br />Bottom line whatever propellant you use comes down to combining Hydrogen and Oxygen, its simply a matter of how you get them to the point of the fire. Combine them with other elements and you lose energy separating them during the reaction as well as adding complexity and dead weight in transporting them, not to mention the containment requirements. <div class="Discussion_UserSignature"> </div>

 

[willpittenger]

After reading all the posts so far, I have compiled a list of items for our "ideal" fuel wishlist for a lander that might sit on the lunar surface for months before being called on and might be reused. In replies, please indicate which item you are talking about by the number.<br /><ol type="1"><li>Hybrid design -- allows for shut off and yet you have half the stability of solid fuels<li>Hypergolic -- I don't know if any hybrid hypergolics have been even conceived of, but the Apollo lander used ordinary hypergolics for a very good reason: no moving parts when used with the Helium pressurization system (which would need replaced for storability reasons)<li>All fuels and pressurization systems must be stable at all ambient temperatures available on the moon. Please note that this would vary depending on where on the moon you are going. (Equator vs. Poles). As mentioned in older posts, this might require use of something like NOX rather than LOX. One user also suggested using parafin wax for the solid fuel.<li>For later missions with a reusable lander: fuels, oxidizers, and pressurization compounds must be something that we can make on the Moon from regolith.<li>Primary engines on manned and heavy cargo landers will require a relatively high ISP. That might rule out something like parafin wax and straight NOX.<li>Minimal toxicity -- Even if the fuel is made and used on the moon, this must be a concern in case a fuel line ruptures such that an astronaut gets sprayed. Furthermore, the exhaust should also be nontoxic so no one is hurt during testing of the engines.</li></li></li></li></li></li></ol><br /><br />Did I miss anything? Do we know of anything that meets all goals?<br /><br />Edit: added Minimal toxicity requirement <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[rybanis]

You know, looking at your list, it seems to be pretty complete.<br /><br />With hypergolics:I wonder if you could substute the He pressurization with something that would last longer and not boil off? <div class="Discussion_UserSignature"> </div>

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>With hypergolics:I wonder if you could substute the He pressurization with something that would last longer and not boil off?<p><hr /></p></p></blockquote><br />That's why I had to ask. I assume that another noble gas would be ideal, but...<br /><br />BTW: You will note that I thought of something else. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>With hypergolics:I wonder if you could substute the He pressurization with something that would last longer and not boil off? <p><hr /></p></p></blockquote><br /><br />Helium is presence as a gas. It does not boil off and will last a long time assuming no leaks.<br /> <div class="Discussion_UserSignature"> </div>

 

[willpittenger]

Actually, the helium system on Apollo 13 failed after, what, 10 days? That does not qualify as "storable" in my book. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[gunsandrockets]

About N20...<br /><br />"Nitrous oxide ...would need to pressurized and the Nitrogen ...[is] only along for the ride."<br /><br />Not true.<br /><br />First off N2O is self-pressurizing. Space Ship One did not have a pressurization system for the Nitrous Oxide tank. Because of self-pressurization the N2O was used for the cold-gas thruster reaction control system in addition to use in the hybrid rocket engine of SS1.<br /><br />Secondly N20 is energetic stuff. From what little research I've done you could consider N20 as the equivalent of hydrogen peroxide! You see at the right temperature when N20 hits the right catalyst it disassociates exothermically. Just like hydrogen peroxide, N20 can be used as a hot monopropellant. There's plenty of energy stored in the N20 chemical bond just waiting to be released. That Nitrogen isn't just along for the ride. <br /><br />Used as a monopropellant, N20 can have an ISP of 180 seconds.<br />When used with a hydrocarbon fuel, an N2O bipropellant rocket engine can have an ISP of over 300 seconds. Lots of people are looking at the rocket engine possibilites of N2O. This potential is even being investigated by the Chinese.

 

[gunsandrockets]

"Just my opinion, but if the vehicle is going to have any sort of cryogenic cooling for oxygen, then little more complexity is required to use methane as the fuel, and the combination is more energetic than heavier hydrocarbons."<br /><br />Methane is a favorite combination with LOX for many good reasons. Highest ISP next to Hydrogen, much better density and higher liquid temperature compared to Hydrogen and the possibility of producing methane on Mars from the CO2 in the Martian atmosphere. That's why NASA likes it.<br /><br />Yet I like propane fuel better than methane fuel. Why? Methane has a rather narrow temperature range where it remains liquid (about 20 degrees C), wheras propane won't freeze solid if in contact with liquid oxygen which means the propellant tanks could share a bulkhead and save weight. And though methane has a higher ISP than propane, it isn't by very much. Wheras LOX chilled liquid propane is so much denser than liquid methane that a spacecraft with the same volume tanks has much higher performance using propane than with methane. Finally the higher carbon to hydrogen ratio of propane compared to methane could ease the production of fuel on Mars because less hydrogen feedstock would have to be carried to Mars to produce the equivalent amount of fuel.<br /><br />So for storability, performance and ISRU reasons I prefer propane to methane.

 

[willpittenger]

As I understand it, the failure was in the lander, which had no fuel cells. Furthermore, I remember Lovell's book, <i>Lost Moon</i>, mentioned not being able to fire Aquarius's main engine once the system failed. (The failure was expected and it was only a matter of when that remained unknown.) <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[holmec]

Can't be Apollo 13. The lander never made it to the moon. Maybe some other mission? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[willpittenger]

Apollo 13 is correct. The failure happened on the way home. Remember, Aquarius was used as a lifeboat. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[scottb50]

Maybe you should rent the movie.<br /><br />The problem happened on the way to the moon and instead of entering orbit they swung around the moon and headed back to Earth. <div class="Discussion_UserSignature"> </div>

 

[willpittenger]

You appear to be mixed up. The event on the way to the Moon was in the SM. One of the oxygen tanks blew. Once the helium system went, the main Aquarius engine was useless. However, it fired while behind the moon and once on the way back. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

I thought I said that. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

At that point though, the main engine was useless, correct? Hence, the system would not qualify as "storable." <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

Wrong failure. We are talking about the burst disk in the helium pressurization system. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[willpittenger]

You misunderstand. We are talking about the loss of pressurization in the lander for its main descent engine. That counts as a failure with regards to "storability." <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[holmec]

>Wrong failure. We are talking about the burst disk in the helium pressurization system. <<br /><br />Got a quote and page number of what your talking about? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>