Can I start an amateur rocket using nitrous oxide as either oxidizer or monopropellant, using a hypergolic slug of something reasonable for use by an amateur rocketeer? What substance could it be?
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$\begingroup$ This is a bit broad and opinion based as "safe" and "obtainable" are subjective. I'd suggest defining some parameters $\endgroup$– GdDFeb 27, 2017 at 15:09
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$\begingroup$ I would suggest reading 'Ignition' if you have not already done so. It covers many fuels and their safety (but not their obtainability by the general public). $\endgroup$– OrangePeel52Feb 27, 2017 at 15:14
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$\begingroup$ GdD: Is there a wide range of even remotely safe and remotely obtainable substances that fit the bill? $\endgroup$– SF.Feb 27, 2017 at 15:14
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$\begingroup$ @OrangePeel52: I checked Ignition! before posting this question. No hypergolics were mentioned in use with $N_2O$ and the substance only appeared as two scarce mentions, one for early experimental rocketry as monopropellant or hybrid motor oxidizer (no ignition mechanism mentioned) and one as temperature depressant with $N_2O_4$ (failed). $\endgroup$– SF.Feb 27, 2017 at 15:16
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$\begingroup$ Triethylaluminium is the best i have so far, and surely does not meet safety limits. hindawi.com/journals/ijae/2014/269836 $\endgroup$– OrangePeel52Feb 27, 2017 at 15:23
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3 Answers
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This is a mix that apparently could work.
"When passed over a warm ruthenium catalyst bed, gaseous nitrous oxide and an ethylene-ethane gaseous blend combust instantly"
Supplies could be found for the following:Ruthenium and Ethane
But I could not find sources for Ethylene, but it seems to be available for industrial uses. This could disqualify this combination depending on the meaning of 'available'.
The safety sheets for ethane and ethylene list only that the gases are very flammable, but unlike Triethylaluminium will not combust on contact with air... so thats a step up.
The safety data for ruthenium seems to list is as quite poisonous, so that could disqualify this combination depending on the meaning of 'safe'.
answered Feb 27, 2017 at 15:39
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$\begingroup$ Thanks. One serious problem: how would one go about making a hypergolic slug out of ethane and ethylene? $\endgroup$– SF.Feb 27, 2017 at 16:06
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$\begingroup$ I agree that could be challenging, I have stuck to answering the title question because i dont know much about how rockets are plumbed. $\endgroup$ Feb 27, 2017 at 16:40
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$\begingroup$ A hypergolic slug is a small piece of solid (may be a swab of cloth/cotton/paper coated in liquid) placed in the combustion chamber. Upon contact with the propellant/oxidizer it combusts spontaneously, initiating combustion with actual fuel - essentially, it's a chemical ignitor. It's pretty safe even when using pretty nasty hypergols because of the minuscule amounts used. Ethane and ethylene are gases in room temperature though. $\endgroup$– SF.Feb 27, 2017 at 16:45
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$\begingroup$ Rather than a slug, it might make more sense to use a torch igniter -- something like a tiny welding torch / rocket chamber that fires into the combustion chamber. Obviously this means more plumbing and valves, but is better for restarts. $\endgroup$– ikraseApr 4, 2020 at 3:40
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$\begingroup$ Also the ruthenium you linked is a compound, not the metal itself which is probably safer. $\endgroup$– ikraseApr 7, 2020 at 11:30
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Most if not all hypergolic fuels are toxic to varying degrees. Hydrazine, mono- methyl hydrazine, and unsymmetrical dimethyl hydrazine are all in this category. Virgin Galactic Space Ship One used nitrous oxide with aluminum grain but needed an igniter. A venting problem on Apollo-Soyuz return knocked out one astronaut and all three had to be hospitalized for a time. I would avoid hypergolic fuels. They are not for the amateur rocketeer.
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$\begingroup$ As long as it's poisonous through ingestion, and not e.g. through skin contact, or inhalation, that's not such a big problem. Also, recognize the difference between hypergolic fuel and hypergolic slug. $\endgroup$– SF.Feb 27, 2017 at 16:21
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$\begingroup$ If there was a reasonable hypergolic chemical that was only toxic from ingestion, don't you believe that NASA or Space X would be using it ? $\endgroup$– BobK99Feb 27, 2017 at 16:58
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$\begingroup$ With nitrous oxide? 150s of specific impulse as monoprop; 1 mole of $O_2$ for two moles of $N_2$ as oxidizer? Absolutely not. No matter how friendly and safe the hypergol, it doesn't make up for lousy performance of the oxidizer. $\endgroup$– SF.Feb 27, 2017 at 17:05
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$\begingroup$ This isn't really an answer, as some hypergols are clearly more dangerous than others and exotic possibilities haven't necessarily been exhausted when hydrazine/nitrogen tetroxide works reasonably welll. $\endgroup$– ikraseApr 4, 2020 at 3:42
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My advice is to synthesize some Chromyl Chloride from a oxidized salt of Chromium as it is hypergolic with methanol and sulfur. You can also get about a liter of the liquid with just a days work and it isn’t too toxic to handle. Sadly I couldn’t find a reliable propellant mix using n2o.
