Building a liquid engine

Hi!

I've been studying liquid rocket engines for a few months now and increasingly get the feeling that I have to build one. I'm aware this is not something to do overnight in my shed. I'm aware some ingredients of this cake need special care and not all ingredients are easy to get your hands on.

In my professions over the years as a mechanical engineer i've worked with/designed cryogenic systems, high pressure systems and steam turbines. So i have some basic knowledge what might be useful in these rocket engines, but most of it is still to learn.

So i'm curious, are there people here who've build one? What fuel/oxidizers did you use? and why? how accessible are these chemicals for armatures? What problems did you face?

What is my goal here? Build a study engine to learn as much about these engines.
For those who ask why? Because i want to learn more about rocket engine. Not necessarily want to put a rocket in space (yet! )

You have come to the wrong forum for liquid motors, we specifically deal with solid propellants mostly of the APCP variety or Sugar based fuels and commercial black powder such as Estes. However we do work with all kinds of airframe and fin materials as well as various deployment methods.

The bigger issue is that the discussion of experimental rocket motors is contained in a restricted research forum. You can post your question on reddit (r/rocketry), but people are likely to be a bit curt because they hear this question on practically a daily basis. Still worth a read and the sidebar has links to some further reading material. I'm on r/rocketry under a different username and can give some more details there.

I'm a member of the STAR rocketry team of UC Berkeley. I'm not going to go into overmuch details, but overall building a liquid rocket engine is going to be very expensive and much more complex than you'd expect. The most common method requires access to a metal machine shop and tools such as a metal lathe and mill. Fuel wise, we are using kerosene/lox, but considering other fuel choices too.

rharshberger said:

You have come to the wrong forum for liquid motors, we specifically deal with solid propellants mostly of the APCP variety or Sugar based fuels and commercial black powder such as Estes. However we do work with all kinds of airframe and fin materials as well as various deployment methods.

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Rocket501 said:

The bigger issue is that the discussion of experimental rocket motors is contained in a restricted research forum. You can post your question on reddit (r/rocketry), but people are likely to be a bit curt because they hear this question on practically a daily basis. Still worth a read and the sidebar has links to some further reading material. I'm on r/rocketry under a different username and can give some more details there.

I'm a member of the STAR rocketry team of UC Berkeley. I'm not going to go into overmuch details, but overall building a liquid rocket engine is going to be very expensive and much more complex than you'd expect. The most common method requires access to a metal machine shop and tools such as a metal lathe and mill. Fuel wise, we are using kerosene/lox, but considering other fuel choices too.

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Thanks for the response! I'm going to checkout reddit for this! I hope to find some more information about it there. The fact that its mainly in restricted research forums might explain why its so hard to find good in dept discussions about this subject.

I'm aware that it's costly and complex, but the last one is one of the reasons of doing it. If it isn't hard it isn't fun.

I'm having a good amount of metalworking tools/machines including a (cnc converted) mill and lathe. And at work I have access to tools that might be useful as well.

It might be advisable to start your journey with hybrid motors before you take on bi-propellant liquid motors. There’s a thread on this forum discussing hybrids that is not restricted.

https://www.rocketryforum.com/threads/hybrids-2019.150103/

Check out Aerocon Systems website at https://aeroconsystems.com/cart/rockets-motors-supplies-page-5/ where they have publications and simulation software.

You might like to check out the Systeme Solaire SS67B3 system.

You didn’t mention what experience you’ve had in rocketry with standard BP or APCP motors.

The guys you want talk to are: Rocket Research Society - www.rrs.org

They have been doing liquid stuff since 1943 and are very helpful.

I get nervous when people say they want to do something as complex as a liquid fuel rocket motor and they can't spell correctly in their first post (numerous mistakes by the way). Not a good first impression.

Do you plan on actually launching this? If so, you need to figure out where and how. You can't show up at a NAR launch with this as it would be rejected. Some Tripoli launches MIGHT allow it, but it might be outside their scope too. Liquid fuels are much more dangerous than solid fuels, so most of us don't want to deal with them. You can always secure your own launch area and get the FAA to approve it, but that can be tricky.

Zeus-cat said:

I get nervous when people say they want to do something as complex as a liquid fuel rocket motor and they can't spell correctly in their first post (numerous mistakes by the way). Not a good first impression.

Do you plan on actually launching this? If so, you need to figure out where and how. You can't show up at a NAR launch with this as it would be rejected. Some Tripoli launches MIGHT allow it, but it might be outside their scope too. Liquid fuels are much more dangerous than solid fuels, so most of us don't want to deal with them. You can always secure your own launch area and get the FAA to approve it, but that can be tricky.

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No TRA sanctioned launches permit liquid rocket motors.

Zeus-cat said:

I get nervous when people say they want to do something as complex as a liquid fuel rocket motor and they can't spell correctly in their first post (numerous mistakes by the way). Not a good first impression.

Do you plan on actually launching this? If so, you need to figure out where and how. You can't show up at a NAR launch with this as it would be rejected. Some Tripoli launches MIGHT allow it, but it might be outside their scope too. Liquid fuels are much more dangerous than solid fuels, so most of us don't want to deal with them. You can always secure your own launch area and get the FAA to approve it, but that can be tricky.

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For what it's worth, I'm not a native so if my spelling and grammar is somewhat wrong sorry for that.

My goal isn't to launch a rocket, but to build an engine. So no i'm not planning on launching one. If i get to a point where i feel like i'm ready to launch a rocket (if ever) I know i probably have to get some special permissions, but that isn't something to worry about in the upcoming years.

I know people are afraid of working with these chemicals (and they should). But as someone who worked professionally in the chemical/gas industry for a while i'm aware of the risks, but also have a good understanding of how to handle most of them. And that is one of the reasons i feel like i'm able to experiment "in a safe way" with these kind of engines.

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I someone has good sources of information about this kind of engines but don't feel comfortable sharing it with the public, feel free to send a DM.

With solid rocket motors, when something goes wrong in a test, the motor will typically CATO. This is simply an over-pressurization event causing structural failure of the motor. In the process there are pieces of metal and/or other materials strewn about and chunks of burning or extinguished propellant thrown around. Some cleanup required, and moderate safety distances are highly encouraged. But as long as you don't start a fire it isn't too bad if you follow general safety practices.

With hybrid rocket motors, when something goes wrong, what happens and what needs to be done about it afterwards is going to depend on the oxidizer choice (assuming typical solid fuel liquid oxidizer scenario). There are scenarios which can result in a low explosive detonation of the oxidizer, but otherwise failures are RELATIVELY benign. For most oxidizer choices, leave well alone until it finishes doing its thing, then go do the cleanup. Highly recommend to not use less than the recommended standoff distances for solid motors of the same size. If using N2O, I recommend greater standoff distances.

With liquid rocket motors, when something goes wrong, the initial failure of the motor can lead to mixing of the fuel and the oxidizer possibly in a gaseous state. The result, depending on the mixing ratio, is a variant on a fuel-air bomb. It can potentially be quite violent and high explosive. The required stand-off distances are greater and the debris field can be much larger. There may no longer be any test apparatus evident as it leaves the area at high speed and random directions, in pieces.

The only liquid motors allowed at TRA launches are research motors using Nitrous Oxide (specifically N2O not any of the others) and Alcohol (specifically Methanol or Ethanol). But realize it is not necessarily all that easy to get approval to burn or launch a research hybrid motor at a TRA launch. It will be a lot harder to burn or launch a research liquid at a TRA launch, even if allowed by NFPA 1127 and by Tripoli in a generic sense.

Gerald

G_T said:

The only liquid motors allowed at TRA launches are research motors using Nitrous Oxide (specifically N2O not any of the others) and Alcohol (specifically Methanol or Ethanol).

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Good to see, I am reading some papers of N2O / Alcohol motors as we speak.

[QUOTE = "johnu, post: 1962135, member: 1679"] Los chicos con los que quieres hablar son: Rocket Research Society - www.rrs.org

Han estado haciendo cosas líquidas desde 1943 y son muy útiles. [/ QUOTE]

Hola. Por qué no utilizar peróxido de hidrógeno como combustible?
Se ahorrarían mucho dolores de cabeza en el mane válvulas y la presurización.

El peróxido de hidrógeno es muy peligroso en las altas concentraciones que se requieren para un motor de cohete eficiente.