Loki graphite nozzles

Yep, i saw that video a few times.

conman13 said:

I believe he's using neither of those as oxidizers and rather GOX, I believe....

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GOX is O2! GOX == Gasious Oxygen. It is pressurized oxygen, which is a poor candidate simply because of the difficulty of getting the mass flow rate high enough given that it's a gas. GOX may be fine for a demonstrator bolted to a lab bench, but not so fine for a flight motor. LOX (Liquid Oxygen) is the better of the choices for O2, as the density is far higher than GOX at any sane pressure, but of course has its own (numerous) issues. N2O is used by amateurs since it is a self-pressurizing liquid. As such, getting the mass flow rate sufficient for rocket propulsion to deliver meaningful thrust is no big deal. Being a monoprop, it is also comparatively insensitive to O:F ratio which makes the design and firing conditions much less critical.

But of course, N2O has its own issues. Being a monoprop and being VERY sensitive to contamination with most anything oxidizable, it can go monoBOOM. It can do so in the gas phase as pure N2O. It can do so in the liquid phase if contaminated with most anything that can be burnt. It is also a minor solvent... Hopefully you get the picture. A very clean flight tank is required, along with careful consideration of any materials the N2O could potentially come into contact with.

N2O is a COMPRESSIBLE liquid, which is uncommon. N2O decomposes exothermically if you get it to about 600 degrees. It can do so at (I've read) as low as about 150C if sufficiently contaminated with the wrong stuff. Now think about that compressible part... Recall PV=nRT? It doesn't take a whole lot of compression to raise the temperature a fair bit. Plumbing, valves, water hammer... That's blown up stuff before.

Unlike most anything else we might use for rocket propulsion as amateurs, N2O actually IS an explosive under the right (wrong) conditions. That's why I'm harping on the safety issues. N2O looks superficially so safe, and used correctly, generally it is. But it is not truly safe.

Safer in some ways is nitrox, but it isn't among the oxidizers we can use under NFPA 1127. We're limited to N2O under those rules. Otherwise it is Class 3 I presume. Nitrox is a mix of N2O and O2. The O2 dilutes the N2O sufficiently that the N2O can now no longer generate enough energy exothermically under decomposition [2(N2O) -> 2(N2)+O2 + heat] to warm up the mix sufficiently to propagate the decomposition. So, it can no longer explode, at least in uncontaminated form. It can be made to rupture a tank under overpressurization just like any high pressure gas or liquid but that is a different beast than a detonation. Our solid propellant motors CATO via overpressurization. A pipe bomb detonates; it is much more violent. Nitrox is also a superior oxidizer, is mildly cryogenic, and self-pressurizes to a higher pressure allowing greater combustion chamber pressure therefore greater ISP.

Nitrox is what you might get at a dental visit or in the hospital. The O2 was added to help prevent the chance of asphyxiation.

N2O can be diluted with other gasses such as He or N2 or some other inert gas, to also render it not detonatable in the absence of fuel contamination. But N2 isn't so useful for rocket propulsion, and though He is light, and perhaps interesting as it could probably be used as an auxiliary pressurant, it is not chemically useful. So IMHO Nitrox is a better choice for the diluted N2O options.

Believe it or not, CO2 can be used as an oxidizer in a hybrid [heat + 2(CO2) -> 2(CO) + O2, the heat coming from the combustion of something else with the O2]. Too bad performance is mediocre as decomposition is endothermic, and it is very picky of O:F ratio and the type of fuel. Otherwise, that would be about as safe a self-pressurizing oxidizer as we could get. Until it is burned of course... Then, not so safe.

Gerald

PS - https://farm4.static.flickr.com/3590/3541796526_eb22fa25bb.jpg There was a much more spectacular one I was looking for, which turned the flight tank to confetti, but I couldn't find it.

rcktnut said:

[YOUTUBE]cG7M1urxjB4[/YOUTUBE]

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Honestly videos like that really tick me off. I am all for experimenting and learning something new but this is just downright irresponsible. I know that this probably comes off as negative but videos like the one above only cause problems for this hobby. I assure you that anyone watching those yahoos in the video above would not be able to differentiate between what they're trying to do and what we do in this hobby. The wrong person gets injured doing this kind of thing and I assure you that there will be some "new rules and regulations" which I am sure will not make flying rockets easier.

I am excited that some of the younger crew on this forum are bursting with energy and excitement to learn about making propulsion systems. After all, this excitement is what fuels discovery and gives me hope for the future. However, with age comes experience and good judgment. I have to say that this video is exactly what everyone on the forum wants to avoid - a VERY dangerous setup which could have been far worse (honestly man! putting your face next to a nearly-flaming O2 tank!!). This bad judgment is why I can see most of the more experienced people avoiding commenting on this post because they do not want to even come close to being considered responsible for anything that goes wrong.

Littlemisterbig - I am sure that you're a bright guy. I am sure that you're enthusiastic about rocketry and propulsion. At the risk of sounding like a curmudgeon, I strongly, strongly urge you to find a mentor to work with. From what I can tell on here you have read some stuff and probably have an idea of what is going on but are still a way off on pulling this off safely and successfully. There are many experienced rocketry hobbyists in new England whom I am sure would be happy to explain and likely demonstrate N20 hybrid motors to you. I am nearly positive that none of them would even consider discussing GOX motors with you. In the rocketry world you need to learn to walk before you run because when things go wrong they can go really wrong.

In closing, I think that Scott at Loki says it best at the top of his products page:
Rocket Motors are safe & predictable only when properly used by responsible persons.

Please, please reconsider whatever you are thinking about doing and find an experienced mentor to help you understand amateur rocketry and experimental motor design.

Yeah, i wasnt planning on attempting this by myself. Dartmouth college which has quite a renowned engineering department is located in the town where i live, so i could probably find a mechanical engineer who would be willing to help me.

I concur like I said above. You need a mentor. This is dangerous. There is a reason why we rarely use GOX

cwbullet said:

I concur like I said above. You need a mentor. This is dangerous. There is a reason why we rarely use GOX

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And in case that isn't clear enough, in this case "we" means "almost no one," and "rarely" means "pretty much never."

For this sort of thing, there are a few VERY sharp knives in the drawer and the rest of us watch from a very far off, safe distance (like neighboring states).

For someone under 18, you should simply read this as, "Just Don't. Period."

If you remain in rocketry, there will be plenty of time for this when you have the skills and the education to learn how to do it safely. For now, you have no idea just how much you don't know.

cwbullet said:

I am pretty sure Making motors for static texting still requires a TRA level 2 cert if you are a club member!

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Only if you plan on firong at a TRA launch. I'm not sure about the legality, but there's nothing I know of to prohibit test firing on your own property

edwinshap1 said:

Only if you plan on firong at a TRA launch. I'm not sure about the legality, but there's nothing I know of to prohibit test firing on your own property

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You might be right but there are local laws. In many states, manufacturing and launching fireworks has limitations. I would suspect pyrotechnics is limited to adults in most.

Mods, if you think anything I've posted should be removed, let me know, or just go ahead and blank it out.

Gerald

cwbullet said:

You might be right but there are local laws. In many states, manufacturing and launching fireworks has limitations. I would suspect pyrotechnics is limited to adults in most.

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I agree it would have to be an adult who takes responsibility, and i don't think many insurance companies would be too approving if you claimed a rocket blew up your garage...

G_T said:

Mods, if you think anything I've posted should be removed, let me know, or just go ahead and blank it out.

Gerald

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I did not. We have to watch these discussion with adolescents. The GOX discussion should always start with don' t use or do this. I suspect it would be hard for them to acquire it any way.

cwbullet said:

I did not. We have to watch these discussion with adolescents. The GOX discussion should always start with don' t use or do this. I suspect it would be hard for them to acquire it any way.

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Really now? https://www.bernzomatic.com/item.html?id=49

littlemisterbig said:

Really now? https://www.bernzomatic.com/item.html?id=49

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I would be surprised if they sold it to a teen under 18.

I'm going to be the jerk who closes this thread. It's going to happen for a few of reasons...

First, it's a minor who's asking about making motors. Asking without the involvement of a parent or mentor, and no mentor should be helping a minor with making motors without parental approval.

Second, we're not having a discussion about GOX or LOX. They're an entirely different animal than anything we deal with in this hobby. You want to investigate that? Go to California and get in with the FAR crowd -- they kinda sorta know what they're doing, and they destroy a lot of hardware in learning what they know. GOX and LOX are not to be trifled with.

Minors are the future of our hobby, but they need to be involved at an appropriate level. Diving into making their own motors without a responsible, knowledgeable adult (and educated parental approval) in advance is not the appropriate way to do it.

-Kevin