Which oxidiser ?

[siddly]

Hi folks, been lurking here for a while and decided to join in.
I'm English by birth but now live in Spain, something which will become relevant in a very short while.

I would like to build a liquid fuel rocket motor, or maybe a hybrid at a push. It doesn't have to be flight weight, it's just for fun.
The construction of the motor will be relatively straightforward as I have a lathe, mill, pillar drill etc etc.

What I'm unsure of is which oxidiser to use. I live in the boonies, on a little farm in the mountains and sourcing anything which isn't related to growing olives is pretty difficult. No car customisation shops for N2O, nowhere I can easily get GOX

I'm actually considering ordering some of the little N2O canisters and attaching a few of them to a common manifold.

The other plan is to concentrate H2O2, which seems...problematic.
Searching for information on this has led me to various chemistry forums which seem to be populated either by mouthy kids who don't have a clue or knowledgeable individuals who won't tell you anything because they consider HTP to be too dangerous to contemplate.

So the question is, if you had my limited resources which oxidiser would you use ( not limited to HTP or N2O ) ?

Or would you just give up ? ;D

[wolfdragon]

You can get LARGE bottles of GOX at welding suppliers, you are out in the boonies in farm country, someone is selling the farmers oxy-fuel torun torches to fix things...

[Johansson]

Hi and welcome to the forum!

You could build a small home lab and make red fuming nitric acid, that is probably one of the better oxidisers although not the healthiest to handle.



How large engine do you want to build? If you can settle with a small one you could use compressed air, a 2x15L 200bar scuba tank should provide air for a couple of seconds of hard running.

Why not consider using olive oil soaked cotton as fuel in a hybrid rocket engine? That would be fun since you can grow the fuel yourself.

Cheers!
/Anders

[siddly]

Wolfdragon - pretty much all the farming here is human powered ! I expect the local garages have oxy\acetylene gear. It's an option if I can persuade one of them to sell me a bottle, or maybe make something they could decant it into.

Anders - what a Nerdlinger that guy in the video is I kept waiting for him to say " HOYVIN GLAVIN !! " like Professor Frink out of the Simpsons
Apart from the handling difficulties I don't think I could make enough RFNA to have fun with.

The size of the motor is dictated by my machinery, which unfortunately is pretty small. An EMCO Compact lathe and an X-2 mini mill. I had a full size machine shop back in the UK ( I was a gunsmith ) but it was too heavy to ship out here
Probably 50mm is a realistic outside diameter for the casing.

I like the idea of olive oil hybrid fuel, we have 90 olive trees so oil is something we aren't short of

I think I'll do some more research on H2O2, see if I can't get a straight answer on concentrating it.

Love your project by the way...

[wolfdragon]

you should be able to find out where the local garages are getting their oxy-fuel bottles refilled or swapped out and just go there yourself

GOX is stored in a green high pressure bottle, you don't really want to blow that into another bottle for transport, it's a gas laws thing and it just doesn't work in your favor when your source is only 15-30 cubic feet

typical size bottles are the knee high variety with anywhere between 15-30 cubic feet in them at 1800? psi

you can usually buy a bottle already filled for around 50-75 USD and then just swap bottles with the supplier at ~25-35 USD for the gasses in the fresh bottle

If you want a real bottle, say the 200-300 cubic foot range like I have for my welding gasses, you're talking a bottle that is about shoulder high and ~10 inches around, these are also high pressure. The easy way to handle these is to rent/lease the bottle (there are legal things with these big guys so it usually works out better for you in the long run) for ~50-100USD a year and then you can swap it for a full bottle when it runs out, which will be ~60-100 USD for the gas in a fresh bottle

I know all these numbers are for myself here in the states, but they shouldn't be that far off...

Example of how I got my 300's and how I get them replenished:
Sign paperwork and pay the man for the lease on the tank (mine is currently for 3 years at ~50USD a year)
Load the full/fresh bottle into my truck and drive to my shop, install tank, hookup welder, weld...
When the pressure gauge is indicating the tank pressure is getting low, go back to weld supply with the empty tank
Go in, pay the man the ~60USD for 300 cubic feet of argon (each gas has it's own price)
Leave my empty tank, take a fresh/full tank back to the shop

Repeat process through duration of lease, at which point you either renew the lease or return the tank

It really should be that simple to get GOX for your engine...

[siddly]

Sad thing is that I gave away 2 full size and two small ( Portapack ) bottles before I emigrated together with regulators and flashbacks, the whole 9 yards

Thinking about it there is a friend of a friend in the nearest town who runs a custom bike shop, I bet he's got oxy-acetylene. I can go and ask him the exact procedure for getting a bottle.

I still do like the idea of H2O2 though...

[Johansson]

May 2, 2012 16:17:39 GMT -5 siddly said:

Anders - what a Nerdlinger that guy in the video is I kept waiting for him to say " HOYVIN GLAVIN !! " like Professor Frink out of the Simpsons
Apart from the handling difficulties I don't think I could make enough RFNA to have fun with.

The size of the motor is dictated by my machinery, which unfortunately is pretty small. An EMCO Compact lathe and an X-2 mini mill. I had a full size machine shop back in the UK ( I was a gunsmith ) but it was too heavy to ship out here
Probably 50mm is a realistic outside diameter for the casing.

I like the idea of olive oil hybrid fuel, we have 90 olive trees so oil is something we aren't short of

I think I'll do some more research on H2O2, see if I can't get a straight answer on concentrating it.

Love your project by the way...

Thanks!

Making red fuming nitric acid might be a bit overkill for this project, just thought I should mention it since you were talking about making your own oxidiser.

I think you should try to make highly concentrated H2O2, knowing that you wanted to but didn´t do will haunt you for the rest of your days so I say go for it!

It will also make a very interesting project thread in case you want to share the build with us, I haven´t seen any amateur hybrids run on H2O2 so you will be breaking new ground.

A guy here in Sweden ran a factory that concentrated H2O2, rumor has it that something went wrong and it blew up on him but there is very little information on the homepage other than that they no longer produce H2O2. Check the site out, it is very informative with lots of fun stuff about catalyst rocket engines!

www.peroxidepropulsion.com/

Cheers!
/Anders

[siddly]

Thanks for the link. You Swedes are all crazy Which is good of course, the world needs crazy people

I think I'll start by evaporating some low strength H2O2, see what happens. I have read that one problem with the evaporation method is preventing dust falling into the solution. That seems very strange to me - how difficult can it be to arrange a dust trap ? I can think of several ways. Maybe chemists have no mechanical skills or I'm missing something. Probably the latter

I'll probably go back to lurking again until I have something to report.
If you hear a muffled explosion coming from the direction of Spain then that will be me ;D

[Johansson]

I am looking forward to the progress reports!

[wolfdragon]

Just remember to watch out what all comes into contact with the H2O2, that stuff tends to get rather pissy about metallic ions and common salts when the concentration starts to get useful

[britishrocket]

Hello Siddly,

Hello. Interesting your search for oxidisers. I eventually opted for GOX purely because it was easy to obtain and relatively safe. I go into my choice of oxidiser at more length in my blog post "Fuel Concerns".

I tried a few years ago to concentrate H2O2. wanting to make a British rocket I thought to use the classic Brit oxidiser. I used the method of heating the H2O2 to boil off the water and leave the pure product. It was rather hairy...I stopped my concentration experiment as I was afraid of having a nasty accident. Vapour detonation can easily occur the more it is heated. Another idea might be to freeze it. The H2O2 freezes at -0.43 degrees celsius, so just less than water. If you watch for the ice crystals forming you might be able to extract the still liquid Peroxide. Seems a bit tedious mind.

I don't have my Sutton to hand just now but I'm sure you have to catalyse the peroxide to get the useful oxygen from it anyway, with something like silver nitrate. What might be interesting would be to build a steam rocket by catalysing the H2O2 with Potassium Permanganate. This produces steam and was the system used by the Germans to run the turbopump in the V2. The Germans called the H2O2 "T Stoff" and the Permanganate "Z Stoff". I imagine they did this to prevent us finding out what they were; it didn't work.

Best of luck,

Carl.

[siddly]

Hi Carl - I actually found your blog before I found this forum. Great stuff.

I think you should give your rocket a rainbow codename ( for the benefit of non British aerospace enthusiasts\geeks that was the naming system for secret projects in the 1950's heyday of research ) - Blue or Black something maybe ?

I'm thinking of using the HTP with a fuel, rather than as a monopropellant. A 'hot' motor if you like.
I do have a small library of books from the 40's and 50's on rocket technology and there is a lot of information on the German Walther motors ( and to a lesser extent British JATO's using HTP )
Not that I could replicate one of course, even if it would scale down to small size. But it's useful nonetheless.

The idea of heating H2O2 worries me as well. I'm sure I read that bad things can happen at 70C vapor temp, which doesn't seem to leave much room for maneuver.
Freezing seems a good plan, I'm familiar with the technique from using it to extract the alcohol for otherwise failed and undrinkable homemade wine experiments

( Edited to get Carls name right )

[britishrocket]

Hello Siddly,

Hi and thanks for your kind comments about my project. It is a good idea to use a rainbow code name, like Blue Streak or Black Knight/Black Arrow. I have affectionately dubbed my engine project "Thunderchild", after the Dreadnought in HG Wells' War of the Worlds, that takes out one of the martian fighting machines. I thought the name suitably British whilst conjuring up the image of a noisy, small thing.

I think you probably could replicate one of those Walther motors, I have seen examples of them at Cosford. The machining and welding is fairly straightforward. You have to bear in mind too that the Germans were on the bones of their arses when they built them, and they used a lot of cleverly simple design features. A lot of that stuff was likely built in workshops not too dissimilar to the average amateur one these days. Lots of interesting stuff at Cosford like a sectioned De Havilland Spectre and a double Spectre.

I wonder if you could directly buy H2O2 of sufficient strength. Chemical laboratories use it and you can buy it from chemical supply outlets. Not sure on the concentration though.

Interesting your freezing the wine to get the alcohol out of it. You could use that as your fuel.

What books do you have from the 40s and 50s on Rocket technology? Would be interested to know the titles, so I can try to get hold of them. I have a copy of a paper on a British rocket engine from the early 50s, called "The Beta Project". It used H2O2 and what they called "C Fuel" which was C Stoff, i.e. Methanol, Water and Hydrazine Hydrate. It makes very interesting reading. The Beta engine was built by the Royal Aircraft Establishment and was designed to power a large model aircraft for supersonic research. If you have an email address I could send you a copy of it.

Best Wishes,

Carl.

[siddly]

Hi Carl, I wasn't aware of the Thunderchild reference and now you explain it I think it's very appropriate. Afraid I haven't read WOTW.

The books are part of what is left of a large collection of military technology and aerospace titles that were too bulky and heavy to ship out here in toto.

I don't think there would be much in them that you could learn from, given your knowledge, but the historical context is interesting.

Rockets, Missiles and Space - Willy Ley, Chapman and Hall
Men, Rockets and Space - Lloyd Mallan, Cassell
The Viking Rocket Story - Milton Rosen, Faber
Development of the Guided Missile - Gatland, Flight Publications
Rockets and Guided Missiles - Humphries, Benn
Principles of Jet Propulsion and Gas Turbines - Zucrow, Chapman and Hall
The Jet Engine Manual - Mangham and Peace, Newnes
The Lonely Sky - Bill Bridgeman, Cassell ( doesn't really belong in this category but a great book )

I collected them ( and many other aerospace titles ) from charity shops mostly. The price is right and the cause is usually good.

I would actually like to replicate a Walther motor, but I reckon the turbopump alone would be a huge challenge - a project in it's own right. Steam turbines don't seem to scale very well and I know that model engineers who have tried to use them in boats have had all kinds of problems.

I have had some more thoughts about HTP. Given that during June, July and August the daytime temps are 40-50C here with very low humidity I'm thinking about an accelerated form of evaporation by placing the H2O2 in a black painted container and letting the sun do the work for me.
Wine would make a good raw material for the fuel on grounds of cost - 90p per litre ! but ethanol is cheap as well and easily available.

If I could get lab grade HTP it would have to be from the UK. We do have a friend who runs a van between Spain and the UK a few times a year, but I'm not sure if he'd want to carry it. On his next run he'll be bringing me a 5kg bag of white powder that might cause a few raised eyebrows if customs search his van I hope they can easily tell the difference between anyhdrous borax flux and...other white powders

I'd love a copy of that paper Carl - what I'll do is check my profile and see if I enabled forum members being able to send me emails ( or if it's possible )

Cheers !

Edit - I think you can now email me by clicking on the leftmost icon under my username. I think

[britishrocket]

Hello Siddly,

Thank you for the list of titles, I have searched them and found most of them so I am going to try to get them I agree with your sentiments on charity shops as good sources of books.

Ethanol is indeed cheap and it can be mixed with water to lower the combustion chamber temperature.

I have emailed you two papers, the first is the RAE report on the Beta Rocket Motor and the second is the RAE report on the aircraft it was designed to power.

Best Wishes,

Carl.