New rocket fuel
Discussion
The US Air Force have developed a new fuel to replace the highly toxic, unstable, and very difficult to handle hydrazine used in many rockets at present. It is an 'ionic fluid' that is reportedly less toxic to humans than caffeine, easy to handle, more efficient, and it's combustion products are also relatively benign - only problem is that it's combustion temperature is so much higher that no current engine could burn it without melting 
I'm sure they'll soon develop engines that can use it though
http://www.space.com/21185-new-rocket-fuel-helps-n...
I'm sure they'll soon develop engines that can use it though
http://www.space.com/21185-new-rocket-fuel-helps-n...
More important than 'greeness', what about power-to-weight ratio?
Secondly, the chemistry:
'The main ingredient in M315E is hydroxyl ammonium nitrate.'
'when combusted, M315E only throws off nontoxic gasses like water vapor, hydrogen and carbon dioxide'.
So where does all the nitrogen from the ammonium and the nitrate go?
Secondly, the chemistry:
'The main ingredient in M315E is hydroxyl ammonium nitrate.'
'when combusted, M315E only throws off nontoxic gasses like water vapor, hydrogen and carbon dioxide'.
So where does all the nitrogen from the ammonium and the nitrate go?
I've done a bit more searching, and while I can't find an actual figure for the specific impulse of M315E, it is variously reported as being denser than hydrazine ( so smaller tanks or more performance for same tanks ), higher specific impulse than hydrazine, and offering nearly twice the energy density of hydrazine. There are also some vague quotes that is will give a 50% improvement in propulsion efficiency.
That article suggests that this stuff is hard to get to ignite, surely a large part of the point of using hydrazine is that it goes bang at the drop of a hat. While potentially useful this new stuff isn't looking like any kind of substitute for hydrazine to me. Plus "green" when it's combustion products are water vapour and CO2? Can't see the AGW zealots considering it green under those circumstances.
ETA: Further research suggests that in use the reaction is catalysed, so new thruster designs but could replace hydrazine potentially.
ETA: Further research suggests that in use the reaction is catalysed, so new thruster designs but could replace hydrazine potentially.
Edited by Einion Yrth on Saturday 18th May 12:45
Again the article doesn't mention whether the new fuel can be used in both roles that hydrazine is used in i.e. as a monopropellant with a catalyst or as a bipropellant with an oxidiser. If it can be used as a monopropellant then the ignition of it isn't an issue. Only if it is used as a bipropellant does ignition become a factor, and then only if it isn't hypergolic with the oxidiser in the way that hydrazine ( or more accurately MMH or UDMH in rocket applications ) is.
wiki said:
Hydrazine was first used as a rocket fuel during World War II for the Messerschmitt Me 163B (the first rocket-powered fighter plane), under the code name B-Stoff (hydrazine hydrate). When mixed with methanol (M-Stoff) and water it was called C-Stoff.[citation needed]
Hydrazine is also used as a low-power monopropellant for the maneuvering thrusters of spacecraft, and the Space Shuttle's auxiliary power units (APUs). In addition, monopropellant hydrazine-fueled rocket engines are often used in terminal descent of spacecraft. Such engines were used on the Viking program landers in the 1970s as well as the Phoenix lander and Curiosity rover which landed on Mars in May 2008 and August 2012, respectively.
In all hydrazine monopropellant engines, the hydrazine is passed by a catalyst such as iridium metal supported by high-surface-area alumina (aluminium oxide) or carbon nanofibers,[30] or more recently molybdenum nitride on alumina,[31] which causes it to decompose into ammonia, nitrogen gas, and hydrogen gas according to the following reactions:[citation needed]
1.3 N2H4 ¨ 4 NH3 + N2
2.N2H4 ¨ N2 + 2 H2
3.4 NH3 + N2H4 ¨ 3 N2 + 8 H2
Reactions 1 and 2 are extremely exothermic (the catalyst chamber can reach 800 ‹C in a matter of milliseconds,[30]) and they produce large volumes of hot gas from a small volume of liquid,[31] making hydrazine a fairly efficient thruster propellant with a vacuum specific impulse of about 220 seconds.[32] Reaction 3 is endothermic and so reduces the temperature of the products, but also produces a greater number of molecules. The catalyst structure affects the proportion of the NH3 that is dissociated in Reaction 3; a higher temperature is desirable for rocket thrusters, while more molecules are desirable when the reactions are intended to produce greater quantities of gas[citation needed].
Other variants of hydrazine that are used as rocket fuel are monomethylhydrazine, (CH3)NH(NH2) (also known as MMH), and unsymmetrical dimethylhydrazine, (CH3)2N(NH2) (also known as UDMH). These derivatives are used in two-component rocket fuels, often together with nitrogen tetroxide, N2O4, sometimes known as dinitrogen tetroxide. These reactions are extremely exothermic, and the burning is also hypergolic, which means that it starts without any external ignition source.
Hydrazine is also used as a low-power monopropellant for the maneuvering thrusters of spacecraft, and the Space Shuttle's auxiliary power units (APUs). In addition, monopropellant hydrazine-fueled rocket engines are often used in terminal descent of spacecraft. Such engines were used on the Viking program landers in the 1970s as well as the Phoenix lander and Curiosity rover which landed on Mars in May 2008 and August 2012, respectively.
In all hydrazine monopropellant engines, the hydrazine is passed by a catalyst such as iridium metal supported by high-surface-area alumina (aluminium oxide) or carbon nanofibers,[30] or more recently molybdenum nitride on alumina,[31] which causes it to decompose into ammonia, nitrogen gas, and hydrogen gas according to the following reactions:[citation needed]
1.3 N2H4 ¨ 4 NH3 + N2
2.N2H4 ¨ N2 + 2 H2
3.4 NH3 + N2H4 ¨ 3 N2 + 8 H2
Reactions 1 and 2 are extremely exothermic (the catalyst chamber can reach 800 ‹C in a matter of milliseconds,[30]) and they produce large volumes of hot gas from a small volume of liquid,[31] making hydrazine a fairly efficient thruster propellant with a vacuum specific impulse of about 220 seconds.[32] Reaction 3 is endothermic and so reduces the temperature of the products, but also produces a greater number of molecules. The catalyst structure affects the proportion of the NH3 that is dissociated in Reaction 3; a higher temperature is desirable for rocket thrusters, while more molecules are desirable when the reactions are intended to produce greater quantities of gas[citation needed].
Other variants of hydrazine that are used as rocket fuel are monomethylhydrazine, (CH3)NH(NH2) (also known as MMH), and unsymmetrical dimethylhydrazine, (CH3)2N(NH2) (also known as UDMH). These derivatives are used in two-component rocket fuels, often together with nitrogen tetroxide, N2O4, sometimes known as dinitrogen tetroxide. These reactions are extremely exothermic, and the burning is also hypergolic, which means that it starts without any external ignition source.
It actually says 'the catalyst chamber can reach 800 ‹C in a matter of milliseconds' - it doesn't say what the eventual temperature is.
MartG said:
Yes - the shuttle engines used regeneratively cooled nozzles, but until now I guess hydrazine is too unstable to use for nozzle cooling
Hydrazine as a coolant?Simpo Two said:
I may have the wrong end of the stick but are you saying that the same chemical is both rocket fuel AND coolant? And if so, that you burn some to go forwards and spray a bit more, unburnt, on the nozzle...?
Yes - many rocket engines use fuel as a coolant ( F-1, J-2, SSME, etc. ) - the nozzle is actually made up of hundreds of small tubes, through which the fuel passes before returning to the top of the engine and being injected into the combustion chamber
Edited by MartG on Thursday 23 May 10:51
MartG said:
Yes - many rocket engines use fuel as a coolant ( F-1, J-2, SSME, etc. ) - the nozzle is actually made up of hundreds of small tubes, through which the fuel passes before returning to the top of the engine and being injected into the combustion chamber
Some of the fuel, not all of it.Edited by MartG on Thursday 23 May 10:51
ETA: Some engines don't bother to return the fuel and just drop it out the bottom of the bell.
Hmm. HAN is notorious in rocketry circles. It's lovely and stable and you can handle it no problem. The difficulty is that as it degrades it autocatalyses. Ie the degredation products contain catalyst. So it'll sit there for ages behaving and then suddenly your experiment is all over the ceiling. At very high concentrations it also supercools easily. One minute it's liquid and seconds later solid.
If I remember right Iron is a favorite catalyst but the stuff can be safely used with stainless steel of the right grade. A fair amount of research has been done jnto HAN as it is very attractive as a rocket propellant (and can function as a monopropellant or oxidiser). I wonder if the US have found a way of taming the stuff at last. If they have it's a big leap forward.
If I remember right Iron is a favorite catalyst but the stuff can be safely used with stainless steel of the right grade. A fair amount of research has been done jnto HAN as it is very attractive as a rocket propellant (and can function as a monopropellant or oxidiser). I wonder if the US have found a way of taming the stuff at last. If they have it's a big leap forward.
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