deltaH
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An alternative to toxic 1,1-dimethylhydrazine (aka UDMH) as hypergolic rocket fuel
Hydrazine and derivates, such as 1,1-dimethylhydrazine (aka UDMH), are extensively used as hypergolic rocket fuels (1), however, they are extremely
toxic and carcinogenic.
I have worked with cyanamide chemistry many years ago and drawing from that experience, I want to propose a hypothetical candidate as a safer
alternative, notwithstanding NASA's work into hydroxylammonium nitrate based monopropellants (3):
1,1-dimethylcyanamide
From Sigma-Aldrich (2)
b.p. = 161-163 °C
SG = 0.867
While I haven't investigated whether it is hypergolic with high test peroxide, red fuming nitric acid or dinitrogen tetroxide, hypothetically, it
should be due to the high reactivity of the cyanamide functional group.
References
(1) http://en.wikipedia.org/wiki/Unsymmetrical_dimethylhydrazine
(2) http://www.sigmaaldrich.com/catalog/product/aldrich/213802?l...
(3) http://www.livescience.com/38120-nasa-green-rocket-fuel-test...
EDIT (additional references)
A patent for preparing dimethylcyanamide from dimethylamine and cyanogen chloride:
http://www.google.com/patents/EP1072585B1?cl=en
[Edited on 9-12-2014 by deltaH]
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Bert
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2 out of 3 referances posted in OP are not related to this proposed substitute... And the catalogue listing has little information related to the
proposed use.
So- Until there is more solid information/relevant referances- I will put this one into beginnings.
Show us the numbers:
Co$t!
Specific impulse
Physical characteristics, density.
Shelf life
Reactivity? How does it affect commonly used airframe & propulsion system materials... and human technicians?
[Edited on 9-12-2014 by Bert]
[Edited on 9-12-2014 by Bert]
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Bert
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Thread Moved
9-12-2014 at 08:55 |
deltaH
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The density is reported in the "little information related to the proposed use" which I quote as 0.867 
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CuReUS
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read this book ,you may find it useful
http://library.sciencemadness.org/library/books/ignition.pdf
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deltaH
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Thanks CuReUS, will do...
Bert, assuming you prepare it by the methylation of cyanamide, the cost would be related to cyanamide, which is about $2000-3000/ton
as a 50% solution according to Alibaba suppliers, though calcium cyanamide, a slow release fertiliser is sold for much less (~$500-$700). You would
also need a methylating agent, for example dimethyl sulfate (price varies greatly $500-$3000/ton) and finally a base.
It would be neat if a process could be developed to react calcium cyanamide (the cheap fertiliser) with dimethylsulfate directly to make calcium
sulfate and dimethylcyanamide, but that's a purely speculative point at this stage.
As for toxicity, Sigma's MSDS says it is toxic, with an acute oral toxicity LD50 (rat) = 146mg/kg and an inhalation toxicity LC50 (rat) = 2.500
mg/m^3.
Its flash point is reported by Sigma to be 65°C, which is really nice.
As for it's behaviour towards metals, I cannot find specific info (too obscure a material it would seem), but I doubt it would be particularly
corrosive. Also, the cyano group of cyanamide tends to decreases the basicity of amines, so I don't expect it to be a particularly strong base.
[Edited on 9-12-2014 by deltaH]
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Bert
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I have read Ignition!-
The list/classes of fuels previously tried is amazing. Not that chemical engineering has stood still, and economic considerations have likely changed
since the author's day.
I'd still like to see the rest of those numbers...
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Bert
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I got as far as "emits cyanide gas on contact with water".
UDMH starts to sound pretty good about there...
The linked "green propellant" article is short on hard information too.
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franklyn
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@ deltaH
This is about as bad as Methyl cyanic acid. Anything fluid having a nitrile group is automatically
environmentally toxic and also a likely carcinogen at low exposure. That's just basic chemical physiology.
Have you even bothered to read the Material Safety Data Sheet for this. It's at the upper left side on the link you cited here _
http://www.sigmaaldrich.com/catalog/product/aldrich/213802
From
http://pubchem.ncbi.nlm.nih.gov/compound/Dimethylcyanamide#s...
9.1 Safety and Hazard Properties
" A few whiffs of the gas or vapor could cause death; or the gas, vapor, or liquid could be fatal on penetrating the fire
fighters' normal full protective clothing "
Comparatively UMDH is only caustic.
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deltaH
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Franklyn, please explain your rationale in regards to the severe toxicity. The
" A few whiffs of the gas or vapor could cause death; or the gas, vapor, or liquid could be fatal on penetrating the fire fighters' normal full
protective clothing " seems odd considering the LD numbers and the fact that it boils at 161-163C.
Cyanamides do not form cyanides physiologically AFAIK. Cyanamide hydrolysis to urea biologically. Also, calcium cyanamide is a fertiliser, so I don't
get the "automatically environmentally toxic".
Bert
| Quote: | | I got as far as "emits cyanide gas on contact with water". |
Nonsense unless somebody provides me with strong evidence to the contrary, I'll quote from Wiki for cyanamide:
| Quote: |
Environmental aspects
Cyanamide degrades via hydrolysis to urea, an excellent fertilizer. Fungi, like Myrothecium verrucaria, accelerate this process utilizing the enzyme
cyanamide hydratase.[3]
Safety
Cyanamide has a modest toxicity in humans.[4] Workplace exposure to hydrogen cyanamide sprays or exposure in people living in the vicinity of
spraying have been reported as causing respiratory irritation, contact dermatitis, headache, and gastrointestinal symptoms of nausea, vomiting,
or diarrhea.
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Ammonia is worse 
Again, I think this is a strong case of MSDS writer chemophobia... ooh it has a cyano group, it MUST be very bad 
[Edited on 9-12-2014 by deltaH]
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franklyn
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Denial is not a river in Egypt
Earth to @ deltaH , earth to @ deltaH ,
you're not making sense ,
circulate your air through the CO2 scrubber.
.
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deltaH
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Quote: Originally posted by franklyn  | Earth to @ deltaH , earth to @ deltaH ,
you're not making sense ,
circulate your air through the CO2 scrubber.
. |
What exactly doesn't make sense Franklyn?
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Bert
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Let's keep this to science & engineering, ideally that involved with OP's subject?
These are the first lines of the first reference I found. I deduce from the order it was mentioned in, this is information the writer thought
important:
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB934...
| Quote: |
DIMETHYLCYANAMIDE Chemical Properties,Usage,Production Chemical Properties
CLEAR COLORLESS TO YELLOWISH LIQUID
General Description Clear liquid.
Air & Water Reactions Reacts with water to form cyanide gas
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Perhaps it would be best to research the specific material, rather than draw broad conclusions on a related compound or a whole class of compounds?
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Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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deltaH
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I understand Bert, but I simply do not see how this is possible for this specific compound. I think, as is often the case with MSDS',
they look at the class of compounds when the compound itself hasn't been well studied, in this case, probably nitriles and friends, which I agree are
very nasty chemicals indeed.
From that same link you posted:
| Quote: | Reactivity Profile
Nitriles, such as DIMETHYLCYANAMIDE, may polymerize in the presence of metals and some metal compounds. They are incompatible with acids;
mixing nitriles with strong oxidizing acids can lead to extremely violent reactions. Nitriles are generally incompatible with other oxidizing agents
such as peroxides and epoxides. The combination of bases and nitriles can produce hydrogen cyanide. Nitriles are hydrolyzed in both aqueous acid and
base to give carboxylic acids (or salts of carboxylic acids). These reactions generate heat. Peroxides convert nitriles to amides. Nitriles can react
vigorously with reducing agents. Acetonitrile and propionitrile are soluble in water, but nitriles higher than propionitrile have low aqueous
solubility. They are also insoluble in aqueous acids. DIMETHYLCYANAMIDE reacts with oxidizers, water, or steam. |
See how they paint this with a generic brush, that of nitriles. That is where all these chemophobic statements stems, other nitriles, not cyanamides.
By the way, in aqueous solution, cyanamide condenses to form 2-cyanoquanidine and ultimately melamine. The urea hydrolysis must be a biological
specific hydrolysis. I've done this reaction, but it's also explained in wiki for cyanamide.
Now I have already quoted the specific toxicological data for this specific compound above and explained how cyanamides in general are not
particularly toxic or bad for the environment.
Now if you can provide me with a reputable reference of just one reaction where any cyanamide or cyanamide derivative is on the LHS of the
equation and HCN is on the RHS of the equation, other than one with HCN on the LHS and other than a MSDS referring to nitriles in general, then I might start to believe it!
I've also added a patent that discusses the synthesis of dimethylcyanamide in the opening post. The trend seems to be to prepare it by reacting
dimethylamine and cyanogen chloride, so perhaps I was mistaken that it can be made simply by the alkylation of cyanamide.
Anyhow, the cost still wouldn't be too bad as these are industrial reagents, BUT cyanogen chloride is nasty stuff, so not exactly friendly chemistry.
*******************
I found this Russian reference with potentially more detailed toxicological info about dimethylcyanamide, specifically. I'll put in a request in the
appropriate sub-forum... Here, for completeness, is the citation in the meantime:
[Toxicity of dimethylcyanamide], Gurova AI, Alekseeva NP, Gorlova OE, et al. Gig Tr Prof Zabol 1975 Nov; (11) :23-7
[Edited on 10-12-2014 by deltaH]
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deltaH
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Okay, started with the process of estimating the specific impulse (ISP) using a reasonable model [1].
Step one I think is the hardest step... to estimate the adiabatic flame temperature of the rocket fuel combustion. To do this, I have installed an
open chemical engineering software package called Coco [2].It is really outstanding, I recommend it to all. Anyway, in Coco, on can select a unit
operation called a 'Gibbs reactor', it's a special type of theoretical equilibrium reactor where the software automatically equilibrates all or
selected components in a stream, so eazy-peezy, feed your fuel and oxidant into it and set the reactor to have a heat flow of zero (for adiabatic) and
you can read the adiabatic flame temperature as well as the composition of the exhaust. This is really nifty because you can also have components like
hydrogen in the exhaust and the program will work out for you the amount of it that will form at very high temperature. Also not all carbon goes to
CO2, there will be large amounts of CO as well because of the very high temperatures. Anyhow, having all these equilibria worked out gives realistic
flame temperatures.
Okay, so back to my result. The component databank with this software is limited to typical process engineering chemicals, mostly pertrochem stuff. So
I had to approximate my dimethylcyanamide fuel as being an equimolar mixture of nitrogen and propylene for the sake of the simulation. As such, the
fuel has the right number of each element and enthalpically, is probably close enough to my fuel. Anyway, the enthalpy of the fuel is not of major
importance because the products (CO2, CO, H2O, etc) have a far larger effect on the energy balance for this system.
Anyhow, long story short, I decided to burn my trimethylcyanamide with red fuming nitric acid, why... because besides for oxygen, that was what
oxidant was available. Well not specifically RFNA, but NO2 and HNO3 was available, so I decided to declare a 'standard mix' according to wiki for RFNA
consisting of 13% NO2, 85% HNO3 and 2% H2O on a weight basis.
I then manually varied the amount of fuel fed until I got a maximum flame temperature.
The adiabatic flame temperature is about 2750C +-50C operating at 1000psi in the combustion chamber. The composition of my feed was on a mole fraction
basis (some rounding off):
Propylene (20.7%)
Nitrogen (20.7%)
Water (3.7%)
NO2 (9.5%)
HNO3 (45.4%)
Giving the following mass fractions for the combustion products (some rounding off):
Nitrogen (28.0%)
Carbon dioxide (23.7%)
Water (26.5%)
Hydrogen (0.7%)
Carbon monoxide (21.0%)
Sadly, I could not get the reactor to work when allowing the formation of nitric oxide, methane and acetylene. These may form in small amounts in an
equilibrium mixture at such extremely high temperatures, maybe even not so small amounts, but I will have to assume they don't.
Plugging these numbers into the exhaust velocity equation and assuming a chamber pressure of 1000psi expanding to atmospheric, I get:
Ve = 2527m/s
Since Isp = Ve/g
I get Isp = 258/s (EXCEL sheet of calculation attached below).
or Isp = 308/s with Ve = 3021m/s for expansion into space (e.g. as maneuvering thrusters).
References:
[1] http://www.thespacerace.com/forum/index.php?topic=1481.0
[2] http://www.cocosimulator.org/
EDIT 1 I'm attaching my Coco file in case anybody wants to see how it's done.
Attachment: rocket2.fsd (241kB)
This file has been downloaded 574 times
EDIT 2: Changed basis on composition of exhaust to mass fractions, it's just easier to interpret results that way and also for subsequent
calculations.
EDIT 3: Added EXCEL sheet of Ve and Isp calculations.
Attachment: ISP calculation.xlsx (12kB)
This file has been downloaded 404 times
[Edited on 12-12-2014 by deltaH]
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Bert
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Thread Moved
12-12-2014 at 12:38 |
DubaiAmateurRocketry
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Dosnt look bad, however, a note on eyeing the gas production of a fuel.
in HNCO propellants, i have tip of a easy way of telling the gas production between 2 fuels could be guesstimated easily from simply looking at the
chemical formula of the 2 fuels.
First, C and N would make almost same gas production at optimum oxygen level for CO production, second, H2O expands much more than CO and N2. The fuel
candidate you proposed, it has 2.82% of H2O present after combustion, twice less than UDMH, therefore the gas production would be less than UDMH
unless the combustion temperature is significantly higher which is not very nice for the engine.
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deltaH
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Yes hydrazines are great because of hydrogen content, that's one of the reasons they are used, the idea here is to come close to hydrazines but with
less toxicity and still have excellent hypergolicity... still waiting for that Russian paper in requests to hopefully pin that answer, yes or no.
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deltaH
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These two patents teach the use of cyanamide in granular form and dimethylcyanamide diluted in water as pesticides and herbicides for agricultural
crops.
Solid formulations of hydrogen cyanamide for agricultural applications
United States US 8,197,834
http://www.google.com/patents/US8197834
Pesticidal Applications of Dimethyl Cyanamide
United States US 20090275474 A1
http://www.google.com/patents/US20090275474
Anne Gordon, is one of the two inventors in both. She is an Associate Professor at Auburn University and the patents are well researched. Since she
has researched their use on crops in fairly high concentrations, I doubt they are particularly toxic, well unless you're a roundworm or a weed getting
drenched in it as herbicide 
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