britishrocket's bipropellant GOX/ethanol thread

[Johansson]

To continue on the route mator is taking, why even considering GOX when NOX is readily available? It feels like there is one single route we amateur rocket builders can take and that is the NOX/whaterver fuel available route.

I read in my rocket development book that the russians used a 25% mix of water in their LOX/alcohol engines, your statement confirms that water is a great way of lowering the combustion temperature without sacrificing too much energy in the combustion. I´ll try a 75/25% methanol/water mix to begin with and hope that the engine doesen´t melt...

[ernie wrenn]

Johansson

Are you using NOS over Liquid ox mixed with 25% methanol? How do you mix the LOX with methanol with out it freezing solid?

ernie

[Johansson]

Ehh, what? I will use liquid NOX as the oxidiser and a blend of 75% methanol and 24% water as the fuel. The last percentage will be a concentrate of lucky thoughts and grinded wish bones to keep the engine from melting...

[mator]

Big thanks for you Carl!!! Now I understand that LOX is very dangerous. But there is unexplained force that is truying to reduce distance between me and LOX )))
russians also used 40% mix alcohol with water and called it vodka)))) I check, it is burning!!!!
And NOX is 10 times more expensive than GOX and LOX.

[britishrocket]

Hello Mator and Johansson,

Thanks for your comments. When looking at starting to build a LPRE I was heavily influenced by Leroy Krzycki's paper "How to Design, Build and Test a Small Liquid Fuel Rocket Engine". He advised using GOX. I already had equipment/regulators for dealing with GOX and it is cheaply and easily available. It is much cheaper than Liquid NOX and available in greater quantity, which for testing I thought would be a good thing. As I have said befor you can read more on this in my "Fuel Concerns" post on the blog. I understand your pull towards LOX Mator; I've felt it too but I just can't safely and legally store it, despite the fact that I have great experience with it. My workshop is essentially part of the house and my house insurance premiums couldn't take it! Even if i had commercial premises I would have to jump through so many hoops to satisfy the UK legislation on storage and use that it would be an economic disaster. In short, it would kill the project. Being a Brit of course as far as Rocket Engines are concerned I have a massive pull towards Hydrogen Peroxide. Again, I can't obtain it at sufficient concentration (HTP) or store it. So GOX represents the best option in terms of cost and availability right now. I don't want to dampen your enthusiasm for LOX Mator, but I think a Russia without Mator and these boards without Mator would be very much poorer places.

I take it that is GP Sutton's book you are quoting from Johansson? Do you also have his "Rocket Propulsion Elements"? An absolute must for the likes of us. Better to get an earlier edition...much more practical information included and more of a pioneering spirit. Early British Rockets (for example the Beta Project) used methanol and water mixes too. In "Fuel Concerns" I quote from a 1950s RAE report on this method of reducing the cooling load. I hear what you are saying about Vodka Mator! It has crossed my mind, as I live in a part of the UK where almost all the single malt whisky is made! I suppose you could also toast the success of the engine by drinking some of the fuel!

Alexander Ponomarenko has some great Rocket Engine performance prediction software that if you aren't using yet is worth a look. Its called "Rocket Propulsion Analysis" There is a link to it on my blog. You can input fuel/oxidiser combinations and it will give you a full performance analysis. You can choose alcohol water mixes and see the effect these have on hot gas temperature and C*. It is similar to PROPEP but easier to use, in my opinion.

Hope I've answered some of your questions,

British Reaction Research

[wolfdragon]

another reason for GOX over LOX is the price and storability, GOX doesn't boil off, so when you buy X cubic meters of it, you still have X cubic meters of it a week from now (provided you kept the tank valve shut)

a VERY easy way to get GOX is from a welding supply company

[britishrocket]

Hello Wolfdragon,

Good point. I have an account with the British Oxygen Company (BOC) anyway, for my welding gases. Always comes back to availability and ease of storage.

Best Wishes,

British Reaction Research.

[mator]

Mar 31, 2012 6:48:37 GMT -5 britishrocket said:

Hello Mator and Johansson,

I don't want to dampen your enthusiasm for LOX Mator, but I think a Russia without Mator and these boards without Mator would be very much poorer places.

I hear what you are saying about Vodka Mator! It has crossed my mind, as I live in a part of the UK where almost all the single malt whisky is made! I suppose you could also toast the success of the engine by drinking some of the fuel!

I don't understand the first sentence. Can you write with another words, by way that I could understand it.

On second: )))) And oxygen I can breath))) And in steam rocket I can drink fuel by litres every day and be sure in my health)))

[britishrocket]

Hi Mator,

Sorry for the misunderstanding Mator. I meant that I am not trying to tell you not to use LOX, I just would not want to see you have an accident and get hurt.

Best Wishes,

British Reaction Research.

[Johansson]

Ok, then I understand why you chose GOX. The regulators needs to be pretty special to manage those kind of flows and still keep it well regulated, right?

Yup, I have the Sutton book History of LPRE. The Rocket Propulsion Elements book I don´t have, I will try to find an early edition of it somewhere.

I will check that rocket design software, I assume it won´t work on my macbook but I have an old stationary PC at home that I can use.

One thing I have been thinking about is building a thrust chamber from doped carbon fibre, a swedish guy has built several valveless pulsjet engines from carbon fibre weave saturated with a high temp composite glue and they run red hot without any damage to the material.



In case the throat area is too hot for the carbon fibre a graphite nozzle could be fitted to the carbon fibre TC by wrapping a couple of layers around it during construction, but in case carbon fibre could be used for the entire engine it would be really easy to make a bell shaped nozzle and a nicely curved throat by making a plug from wood that can be split at the nozzle throat and removed once the treated carbon weave is cured.

Well worth a try I think!

Cheers!
/Anders

[britishrocket]

Hello Anders,

A very interesting idea and one that is definitely worth a try. The video footage of the pulse jets is amazing. They look and sound just like the power plant of a World War 2 German V1 flying bomb (Vergeltungswaffe, translates in English to something like "revenge weapon"). Quite something to see them running.

It would be a good experiment to try building a rocket thrust chamber in this way. I like the idea of including a graphite liner. It seems to me that a rocket thrust chamber is the perfect application for composite materials.

A copy of GP Suttons Rocket Propulsion Elements would be worth getting, it goes into the theory and practice of thrust chambers and nozzles in quite some depth. It is not inaccessible though. Many early rocket engines were a lot like the devices we build, and although in depth explanations are given the practical is never far away. The earlier editions are much better. I have a second and a seventh edition. The latest edition is extremely expensive and in my opinion it is somewhat "dumbed down". You should be able to pick up an early edition second hand on the web, quite easily.

[britishrocket]

Hi again Anders,

Yes you are right about the regulator for oxygen. I'm looking at using a dome loaded type.

Thanks,

Carl.

[Johansson]

Hi Carl,

The problem would be that no external means of chamber cooling would be possible, so I would have to rely on film cooling to keep the TC from overheating.

Not easy to do when dealing with the small fuel requirements, a single 1mm hole for film cooling would almost double the amount of injected fuel and a full circle of holes would be needed to get a decent film flowing down the chamber walls.

Unfortunately we have no nearby deserts or any other remote location where high altitude rockets can be safely launched, it would be interesting to build a disposable rocket engine consisting of a graphite/carbon fibre thrust chamber and aluminum propellant tanks and see how high it could go.

I found a 2nd edition book on Ebay and have emailed the seller about postage to Sweden, hopefully he´ll get back to me in a day or so.

Cheers!
/Anders

[britishrocket]

Hi Anders,

You won't regret buying Suttons book if you are in any way interested in the engineering of rockets.

No deserts here either unfortunately. I can see what you mean with regard to cooling of the composite rocket chamber. Could be difficult. The man in the video clip is much braver than I am, holding the pulse jet in his hand while it is running!

Have you heard of a material called Macor? It is machinable glass ceramic. It is made by DuPont and was used to make the heat shield tiles on the space shuttle. It is capable of withstanding very high temperatures but apparently machines like aluminium. It can be got in
all the standard shapes of usual materials. It is very expensive however.

I have long wanted to make a thrust chamber from this material, I think it would need no cooling. Perhaps once my test engine is completed and run and I have more experience I will be in a better position to do that.

It would be interesting to see how high a composite rocket could go. I hope you enjoy your book when you get it. You should set aside a few days to spend with it!

Carl.

[Johansson]

I found a 100mm long 20mm Macor rod on Ebay, the seller wants £126 for it so I don´t even want to know what a lenght of 100mm diameter rod would cost...

I think it would be worth while to make an uncooled composite thrust chamber and run it just to find out how much heat it can take before burning through. Perhaps later when the test rig is finished and I find some spare time, by the time I retire most likely.

Cheers!