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How about this-
instead of burning hydrogen with oxygen, as is done in regular liquid rockets, fluiurine and carbon. Fluorine is a liquid at ~85 k, which is 3 or 3 degrees cooler than Oxygen. However, carbon is a solid, from, I believe, 1700 C. There's definitely an advantage there. F2 could be burned with crushed graphite (C2), to ge the product, CF4, Carbon Fluoromethane, a gas at normal temperatures. Because CF4 is Polar Covalant (1.45), while F2 and C 2 are covalent, and will go to the lower energy bond CF4.
-Josh
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How about this-
instead of burning hydrogen with oxygen, as is done in regular liquid rockets, fluiurine and carbon. Fluorine is a liquid at ~85 k, which is 3 or 3 degrees cooler than Oxygen. However, carbon is a solid, from, I believe, 1700 C. There's definitely an advantage there. F2 could be burned with crushed graphite (C2), to ge the product, CF4, Carbon Fluoromethane, a gas at normal temperatures. Because CF4 is Polar Covalant (1.45), while F2 and C 2 are covalent, and will go to the lower energy bond CF4.
Do we want that stuff in our atmosphere? What happens if you breath that in your lungs? My guess is nothing good, but I'm not a chemist.
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Tetrafluoromethane is a gas that contributes to the greenhouse effect. It is very stable and lasts a long time in the atmosphere and is a very powerful greenhouse gas. Its atmospheric lifetime is 50,000 years and global warming factor is 6500 (carbon dioxide has 1).
Inhalation of tetrafluoromethane can cause, according to concentration, headache, nausea, dizziness and damage of cardiovascular system (mainly heart). Long-terming exposure can cause heavy heart damage.
Because of its heavier density, it can fill up ground area and in non-ventilated places can cause asphyxiation.
from wikipedia
As it's denser than the Earth Atmos, Hopefully it will sink to where it can be captured. If not, some sort of valley, artificial or real, may be used, or this can be used in space
-Josh
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That could be worse. Poison gas used in World War I was often heavier than air so that it would sink into the trenches and concentrate killing the soldiers inside. Chlorine is an example of a heavier than air poison gas. Also you'd want the exhaust product of a rocket to be light to increase the ISP, but perhaps the rocket fuel you mention might be easier to store, so there may be advantage in that.
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Burning carbon with fluorine is not that powerful as you think. Burning hydrogen by fluorine is very powerful, significantly more (theoretically) than burning it by oxygen. But the advantages of burning carbon by fluorine are less, possibly even absent, in relation to burning by oxygen. I've once found that out by using a simulation program.
But the disadvantages of fluorine are very severe. It must by stored in heavy tanks, boil-off has is not allowed, so there is some system needed to keep the temperature below 85K. The tank with fluorine has to be equipped with some kind of sophisticated recovery system to keep the fluorine from leaking in case of a launch failure. Beside that, fluorine is not allowed to use on a first or second stage because of the pollution (HF). Think also about risks when filling the tanks.
The only application I could possibly imagine is in case of high stages for large spacecrafts on interplanetary flights.
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I've thought of another fuel- Ammonium Nitrate. It decomposes to N2O and H2O extremely exothermically when put in water. It's a solid, w/ a melting temp of either 169 or 191 celcius, and decomposes around 210, so once the reaction is started, you might ot even need a catylist. It's pretty simple to synthesyse, for more information go to http://en.wikipedia.org/wiki/NH4NO3
-Josh
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The problem with using Fluorine as a oxidiser is it is highly toxic. While a H-F combustion reaction gives you a slightly higher ISP then H-O reaction, the difficulties in handeling Fluorine are conciderable. Flourine is the most electronegative and reactive of all the elements. In its pure elemental state it will burn with practicaly anything, including water and most metals, and is virtualy impossible to extinguish. As noted before it is both toxic and corrosive, and frankly an all around nasty stuff to handle in large quantities. Furthermore it is relativly expensive, much more so then liquid oxygen certianly. And even after it is burned it produces hydrofluoric acid, which is also nasty, toxic, and corrosive. Sometimes small quantites of Lithium are also proposed as an aditive to H-F rockets for even greater ISPs, but again toxicity is a problem.
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As for Ammonium Nitrate, it's not unknown as a rocket fuel. It's performance is similar to that of and Ammonium Perchlorate which is more commenly used (such as in the shuttles SRBs). I belive Ammonium Perchlorate is perfered generaly for its longer burning times and slightly higher performance, but the two come pretty close. Both are obviously considerably inferior to H-O rockets, or even Kerosene/Ox, but supperior in terms of thrust.
He who refuses to do arithmetic is doomed to talk nonsense.
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Here is an interesting propellant. Coffee Creamer. When I served in the military and we went out on our camping trips into the woods we would take the coffe creamer, which was in a solid granular state, open the small packet up and pour the contents slowly out. Next we held a lighter about an inch or so away from the creamer as is poured out. If the lighter was positioned just right in relation to the lighter the coffee creamer would
ignite unitl the flame traveled to the opening where the flame then went out.
Perhaps this type of chemical reaction when used in conjunction with a pressurized system could provide a means of thrust. Maybe not on the main booster engine scale but maybe as a minature manuvering thruster system.
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What about flour? That explodes. If mixed with a solid powdered oxidiser...
Use what is abundant and build to last
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What about flour? That explodes. If mixed with a solid powdered oxidiser...
Wouldn't this type of fuel eventually lead back to solid rocket boosters?
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Solid rocket Boosters.
Advantages.
No trouble with storing fuel under pressure. Leaks don't cause massive explosions.
Disadvantages.
They have to burn themselves out, they can't be turned off.
The best kind of rocket will be the solid/liquid mixture rockets that Virgin Galactic will run on.
Use what is abundant and build to last
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Hydron Peroxide (H2O2)? No there's an idea. It reacts with most metals and produces steam and another element (presumably the Metal Oxide.)
Use what is abundant and build to last
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Actually, I was thinking of using it as a monopropellant, for design simplicity.
Although it probably burns w/ most metals, this would add complication that isn't really needed. But doesb anyone know how many kgs of fuel it takes to get 1 kg of fuel from leo to lmo (low martian orbit)
-Josh
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Oxygen and Hydrogen will remain the first choice for rockets, because of the thrust to weight limitation of chemical rockets. It has the highest thrust with the least amount of weight to that thrust that we can possibly have. It also generates the least amount of pollution that we can possibly generate giving the choices of any other fuel that we could possibly use. So there really is no reason to consider any other fuel source as for rocket taking off from Earth. As to Mars and whether we would have a ready supply of Oxygen and Hydrogen at our disposal would be another question altogether. But, if we could get it on Mars, that is Oxygen and Hydrogen in sufficient quantities, then that would be our first choice there too and for the same reason that we would use it on the Earth as our first choice. If there were no ready supply of both Oxygen and Hydrogen, then we might look for another type of fuel to do that job, but it would be a second choice fuel supply at best. Because, of the lower energy output to weight constraints of those other fuel supplies if they were used as alternate fuels, instead of using Oxygen and Hydrogen fuel which has about the ratio to weight energy output.
So why would we want to use other fuels?
It would also require more fuel to get the same output that we would get using Oxygen and Hydrogen fuel supply.
Larry,
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I meant on mars, as part of ISRU ideas. Of course it would be better to use H and O, but I don't think we will have that kind of capacity. For design simplicity of a monopropellant, and the fact that H2O2 is already there, I thought we might use that.
-Josh
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Good link publiusr.
Here is an interesting propellant. Coffee Creamer. When I served in the military and we went out on our camping trips into the woods we would take the coffe creamer, which was in a solid granular state, open the small packet up and pour the contents slowly out. Next we held a lighter about an inch or so away from the creamer as is poured out. If the lighter was positioned just right in relation to the lighter the coffee creamer would
ignite unitl the flame traveled to the opening where the flame then went out.
What about flour? That explodes. If mixed with a solid powdered oxidiser...
Both are possible, but neither make particularly good rocket fuel. The ISP for both is lower than the Ammonium Perchlorate used in most SRB. Or if we are talking about burning it with liquid oxygen, it is generaly betten out by Kerosene. Solid fuels are denser, but they are difficult to mix/burn with the LOX and their ISPs are generally worse.
For maneuvering thrusters chemical hypergolic bi-propellants are favored because they are easy to fire, turn off, and are very reliable. Their ISP isn't that great, and lots of them are toxic, but thats not that important for maneuvering thrusters.
Hydron Peroxide (H2O2)? No there's an idea. It reacts with most metals and produces steam and another element (presumably the Metal Oxide.)
Hydrogen Peroxide has by used as rocket fuel (oxidiser) many a time. It can be used as a mono-propellant or an oxidiser. As a mono-propellant its ISP is not that great (~150ish) but it has the advantage of being totally non-toxic and fairly simple to use. In the presences of a metal catalysts (not sure what they use, I've used calcium in some experiments) it decomposes rapidly into oxygen and water at fairly high temperatures.
As a bi-propellant its ISP is better (~350) but you have a more complicated engine. Typically something like hydrogen peroxide-kerosene is used. Its denser and potentially easer to handle the liquid oxygen, but more expensive and its ISP isn't as great.
Thats not to say high-concentration H2O2 is easy to handle. The stuff is pretty toxic, and highly reactive. It poses a high fire risk (a VERY strong oxidizer, just not so great per unit weight). And of course if introduced to a catalyst it can (and will) decompose on you (ie explode). Then again its not cryogenic, so thats a point in its favor.
Anyways H2O2 is a decent fuel/oxidiser. Its in use in satellites as a maneuvering thruster and I believe the guys from ID are using in there rocket. I know it has been used as a rocket fuel before.
He who refuses to do arithmetic is doomed to talk nonsense.
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I believe that hydrogen reactes exothermically with CO2. This would appear to be a good airbreathing fuel on Mars, especially for aircraft which do not need to store LH2 for long periods.
Silane is another good fuel that will burn in CO2 and is generally a lot more storable than hydrogen.
CO2 itself would be a good propellant if a nuclear heat source were avilable.
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Check out designs for rocketbelts (commonly called jet packs.) They use Hydrogen Perioxide reacted with silver for fuel.
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While I'm not completely certain that you could not burn silver with H2O2 under the right conditions, I am sure that it is not used as a fuel in jet packs. Silver is heavy, not very reactive, and would probably for some sort of solid after reacting with H2O2. Oh, and it would probably be deadly toxic (breathing heavy metals in is bad). Most likely what is happening is that silver is being used as a catalysts to decompose the hydrogen peroxide. I know platinum can be used, so I would not be totally surprised if silver (which has some similar properties) could be used as well. Or possibly the source just has it wrong and platinum is in fact being used as the catalysts.
I believe that hydrogen reactes exothermically with CO2. This would appear to be a good airbreathing fuel on Mars, especially for aircraft which do not need to store LH2 for long periods.
It does, most any oxidizer (such as CO2) will burn with hydrogen, which is a very strong reducing agent. The problem with this reaction is that it is not especially powerful (you lose a great deal of energy converting CO2 to CO and burning that) and that it tends to produce carbon dust which hurts your performance ever more.
I believe that if you are going to go to the trouble of using liquid H2 (a very demanding cryogenic) that you might as well use a more powerful cryogenic oxidiser such as LO2.
Silane is another good fuel that will burn in CO2 and is generally a lot more storable than hydrogen.
Silane also suffers from much the same performance problems that CO2-H does, but does have the advantage of being dense and storeable.
CO2 itself would be a good propellant if a nuclear heat source were avilable.
Blegh, CO2 would be a pretty terrible propellant. For a NTR molecular weight is THE key to performance. So CO2 (molecular weight 44) performs pretty terribly.
Better choices for a NTR are Hydrogen (obviously), Ammonia (NH4 atmoic weight 18) which breaks down readily to Nitrogen and Hydrogen which improves your average to 8. Or even water (18) or oxygen (32). CO2 is about the worst you could get.
He who refuses to do arithmetic is doomed to talk nonsense.
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Silver was a catalyst.
Use what is abundant and build to last
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