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Is there any such thing as a non-cryogenic, liquid, "green" hypergolic bipropellant, where green means environment friendly and non-toxic?

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    $\begingroup$ Hypergolic and Amateur do not go together. Rocket fuel is already hazardous to work with, materials that explode on contact are even more so. $\endgroup$
    – GdD
    Mar 20 at 13:59
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    $\begingroup$ You should really ask your TA these kinds of questions if this is in a university setting. Otherwise, join an amateur rocketry club. Rocket fuels are stupendously dangerous at times, and we really don't want to help people blow themselves up. $\endgroup$
    – Polygnome
    Mar 20 at 14:50
  • $\begingroup$ We have a close reason for asking dangerous questions about blowing yourself up. I understand you don't want to do that and are not asking how to. I've adjusted the wording of the question a bit to keep answers more generic, Please do not play with rocket fuel! Even if someone on the internet tells you it's safe, you're asking for something that's hypergolic, which means it's "ready to go off" at any moment as soon as it's mixed with something, and you may not know all the things it can react with. Run away! Run away!... $\endgroup$
    – uhoh
    Mar 20 at 15:20
  • $\begingroup$ Possibly also relevant if this is an assignment, does this rocket have to actually fly (thrust/weight>1)? There are probably many reactions that could be used for a bench demonstration of pumps and control systems that are relatively benign, starting with baking soda and vinegar. $\endgroup$ Mar 20 at 23:49
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    $\begingroup$ Edited question to emphasize "bipropellant". $\endgroup$
    – Kozuch
    Mar 21 at 18:52
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Supposedly Rocket Lab is using such a fuel for their kick stage using the Curie rocket engine. Likely it is using their proprietary Viscus Liquid Mono-propellant.

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  • $\begingroup$ The question is about hypergolics (two or more things that react with each other when mixed in certain proportions) which is different than a monopropellant's behavior when exposed to a non-reactive catalyst. $\endgroup$
    – uhoh
    Mar 21 at 9:08
  • $\begingroup$ There is a bi-propellant version of the Curie engine, and I assume it is similar, although very little is known about that, even less than their green mono-propellant... $\endgroup$
    – PearsonArtPhoto
    Mar 21 at 12:22
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It depends what you mean by green. All rockets end up producing vast quantities of greenhouse gases of a variety of types and degrees of harmfulness to the environment (even water vapor is a greenhouse gas). But apart from greenhouse gas emissions many fuels are also dangerous chemicals in their own right that leave toxic residues or pose leak risks or have non green manufacturing processes.

Some rocket propellants produce relatively benign water vapor and carbon dioxide such as RP1, ethanol and methane when combined with liquid oxygen or hydrogen peroxide. But these don’t tend to be hypergolic. However some work has been carried out in an attempt to rectify this situation.

It is possible to make kerosene and high test peroxide into a hypergolic combination if the kerosene is treated with small quantities of a solid energetic activator dispersed throughout with a gelling agent.

https://www.intechopen.com/books/aerospace-engineering/green-comparable-alternatives-of-hydrazines-based-monopropellant-and-bipropellant-rocket-systems

This area is currently being actively investigated by several different teams around the world:

https://www.esa.int/Applications/Observing_the_Earth/Green_Propellant_for_Space_Propulsion

https://www.nasa.gov/directorates/spacetech/green_fuel

https://jewishbusinessnews.com/2020/12/02/israeli-startup-newrocket-is-making-green-rocket-engines/

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