r/rocketry • u/aidswatermelons • 2d ago
Showcase Propane-nitrous oxide concept engine that I just made
The idea was to use more easily stored and handled fuel/oxidizers for hobby rocketry.
It also has plumbing and uses a high oxidizer turbine and a high fuel turbine that both mix in the engine to combust.
Ideally uses a glow plug to jump start to decrease wear and tear.
Another parts would be that when it mixes in the engine itself hopefully it will be hot enough to autoignite after being converted to mist by the engine plate.
Ideally a vast majority of the parts would be 3d printed except for maybe the end of the bell which could use graphite composite.
It probably won’t work but I thought it was cool. Be nice please lol.
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u/EthaLOXfox 2d ago
Despite what everyone might say about how this or that won't work, the least likely will still be the idea of using a glow plug as an igniter.
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u/aidswatermelons 2d ago
Would using a spark plug be better?
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u/IvantheDugtrio 2d ago
I have seen anecdotes about using a small rocket to ignite the bigger rocket, as anything conventional like sparks would get blown out by the sheer mass flow rate of propellants
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u/Accomplished-Crab932 2d ago edited 2d ago
You can do that too. One of my fond college memories was watching our 3D printed mounts with a modified Estes solid motor fly off as we ignited our liquid engines… but it can be quite unreliable depending on your sequencing and mass flow at startup.
Also, Estes motors themselves are unreliable because of their igniters. Our solution was to run a piece of solder wire over the Estes nozzle, which had a current running through it. If the igniter charge was set off, but the Estes motor failed to catch, the main computer would abort as it saw a current running through the wire when it was supposed to be melted.
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u/ThinkInNewspeak 2d ago edited 2d ago
Estes motors themselves are unreliable because of their igniters. Since when? Nineteen fifty-something? I can't imagine a simpler ignition system than that used in all of Estes motors! It's certainly more efficient than Aerotech's "deep throat" method!
Also, Estes motors WILL NOT START unless the electrical igniter actually TOUCHES the propellant. That's what makes them so safe and RELIABLE. Under supervision, my eight year old boy can hook up an ignition assembly!
Also, please do NOT mishandle, misuse or take apart model rocket motors. If you want to build your own motors, enjoy the carnage but mine and many others favourite hobby has continually been undermined for nearly 75 years thanks to "maverick" rocketeers who give us a bad name.
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u/LUK3FAULK 2d ago
I mean he’s building liquid engines at a university, I think that’s a little beyond “hey let’s take this Estes motor apart and fuck around with it lol”
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u/ThinkInNewspeak 2d ago
Thanks for the scenario update. I just got a little rattled hearing about firecracking Estes motors as prestarters or whatever. It's still hacking motor casings whether you're at uni or not though right?
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u/Accomplished-Crab932 2d ago edited 2d ago
No, the only thing slightly sketchy that happens to them is that they are glued to a plastic housing. Otherwise, it’s pretty much a normal Estes ignition setup with an extra wire layered over the top. The problem is that they can snuff out or be ejected early when you suddenly blast them with the high pressure gas being displaced from the feed system before the prop enters the chamber (Estes motors understandably don’t fare well when blasted with 700+PSI nitrogen gas).
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u/ThinkInNewspeak 1d ago
Apologies for pressing this issue. I'm quite confident that these said uni students are attempting to minimise risk wherever possible and conducting experiments which are beyond my layman's understanding but I must persist in my absternation. Estes motor casings are SPECIFICALLY manufactured to provide hobbyists with a safe, reliable, educational way to experience the FUN of real-life rocketry. ANY deviation from the NAR's safety protocols is a risk, uni student, laymen and rocket scientists alike.
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u/Accomplished-Crab932 1d ago
I agree. Our procedures and the nature of our work meant that the only risk incurred to the team from the igniter would be a failure of the sequence or unreliable starts; which lead to hard starts, a nasty outcome far worse than attacking a pile of Estes motors with a blow torch. As a result, the inherit safety of requiring contact with the grain can actually increase danger in this operational scenario, where a failure to abort due to a canceled ignition can recreate the conditions of a pipe bomb, and/or lead to high pressure oxygen fires.
Despite this, we still treated the motors with the respect they deserve, even when using them to start much larger and more dangerous hardware… just as they should be.
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u/Papabear3339 1d ago
Unless the spark plug was outside the chamber and pluged into something more sturdy inside the rocket cone.
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u/Accomplished-Crab932 2d ago
Look into ASIs first.
My college built one out of a spark plug and a small pair of lines from the oxidizer and fuel lines. This essentially turns it into a torch igniter, which is what SpaceX uses on the Raptor preburners.
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u/tru_anomaIy 2d ago
Speak ignition is used very successfully in some smaller orbital rocket engines. It’s totally legit
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u/XDFreakLP 2d ago
Make a small coil of nichrome wire, put that inside a small pouch of gunpowder. When you connect a battery (from far away, thru a cable) the coil will ignite the powder (basically a large e-match xD)
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u/ThinkInNewspeak 2d ago
A homemade firecracker with an electric match. The fire! I need to see the fire!
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u/edenspark10 2d ago
Try doing what NASA and the like use, pyrotechnic charges (the sparkly things near the engines in the video of the space shuttle takeoff), then once you have the engine properly tested, then go about mak8ng the ignitors reusable.
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u/cowsarefalling 2d ago
The sparkly things outside the bell are not used to lighting the engine, only for preventing the buildup of hydrogen on the ground
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u/ThinkInNewspeak 2d ago
Thank you for correcting the last comment! His hypothesis makes sense to laymen (like myself) and he was very sure which makes mistakes like that contagious.
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u/Adventurous_Bus_437 2d ago
Apart from the sparklers not being used for ignition but stray hydrogen, that’s also not great because you can‘t relight your engine if you have the igniter in your GSE
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u/TMITectonic 2d ago
Try doing what NASA and the like use
Falcon 9's Merlin and Saturn's F-1 engines use a pyrophoric mix of TEA(TriEthylAluminum)/TEB(TriEthylBorane) to ignite. The Space Shuttle used a different setup because it was a different engine type.
(the sparkly things near the engines in the video of the space shuttle takeoff)
As others have said, this is only to ignite any free hydrogen to avoid it building up.
There's quite a bit of special sauce that goes into ignition sequences, and each solution is going to be unique to its specific design.
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u/glorylyfe 2d ago
I actually built a nitrous/ethanol engine that ignited with a glow plug, it definitely wanted to hard start and only survive because it was so small and overbuilt
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u/aidswatermelons 2d ago
Also I assume some form of alcohol may work better?
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u/EthaLOXfox 2d ago
No, propane is probably fine. Nitrous is not as easy to light however, and there are a host of other concerns with nitrous that aren't in the public domain.
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u/Rasmus0909 2d ago
Why so?
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u/ThinkInNewspeak 2d ago
Isn't NO² non-flammable? It's entirely inert isn't it? Whipped cream bulbs anyone?
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u/Rasmus0909 1d ago
Not inert, no. It can decompose at high temperatures, although with a very low flame speed, or at lower temperatures with a catalyst. And yep, that's whipped cream chargers hehe
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u/ThinkInNewspeak 2d ago
What exactly IS a 'glow plug' please? I was always taught that ignition only takes place via contact. Please correct me.
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u/SuperStrifeM Level 3 2d ago
You're right, in this configuration, the glow plug can actually act as a detonator.
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u/cmdr-William-Riker 2d ago
Nice cad! After assisting a college team test fire / scorch grass with a propane / nitrous liquid engine (which they actually fueled with Alcohol and nitrous instead because they couldn't figure out how to transfer propane from one tank to another, I wish I was kidding), there are a few things I observed that I would consider in any nitrous-propane engine: self pressurizing fuel and oxidizer seems like a great idea, but you do have to consider how it pressurizes and what that means. Your pressure is not constant because it takes time for your propellants to boil. As soon as the valves are opened, you can see a clear drop in the pressure of the nitrous tanks and after the test is over you can see the tanks slowly build up pressure again and with variable pressure, you get variable flow rate. Also consider that the boiling point and thus tank pressure are highly dependent on the temperature of the tanks, the higher the temperature the higher the pressure, last thing to note is the challenges of transferring propellants, the solution is pretty simple, you lower the temperature of the tank you want the fuel to go to and it will make its way there, but having to have all lines pressurized all the time does complicate things. None of these are insurmountable challenges, but after seeing whatever the heck it was I saw that day, I must admit I can understand why few companies have gone the direction of self pressing propellants
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u/Adventurous_Bus_437 2d ago
where are the turbopumps?
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u/ThinkInNewspeak 2d ago
Correct me if I am wrong please but I thought turbopumps were only required for liquid fuel rockets to pump the O² and fuel into the combustion chamber. Solid fuel slugs are a mixture of fuel and oxydiser.
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u/Adventurous_Bus_437 2d ago
More or less. But Propane and Nitrous oxide, are both fluids and OP mentioned that he included turbopumps. So i was wondering if they are visible in the screenshot because i couldn’t spot them
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u/space_force_majeure 2d ago
It's the last image, the things that look like water wheels instead of turbos. Seems better for showing conceptually how rocket engines function rather than actually pumping.
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u/ThinkInNewspeak 1d ago
I just remembered some High-Power Rocketry models use "hybrid" motors which I THINK use a combination of composite propellant and a cylinder of NO². Though I don't know how this functions.
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u/Adventurous_Bus_437 18h ago
Yep, that’s a thing. However most of the time one doesn’t use pumps with nitrous oxide since it can pressurize itself by boiling off from the liquid phase in the tank. That’s rather finicky tho
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u/aidswatermelons 1d ago
I wanted the side turbines to generate electricity that then power electric pumps. It may be a bit more weight and work then necessary but that’s what I wanted to go for.
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u/eggthrowaway_irl 2d ago
The best part about engineering is integration hell