10 replies to this topic

[icarus]

 bitumen is cheap and readily available from many larger builders merchants and one block purchased will be more than a lifetimes supply .

It is easily casteable when hot. There has been a lot of research using it as a fuel with a solid powdered oxidising agents including ammonium perclorate  (ref  gilsonite )

it functions well  as a reliable  fuel  when oxygen or nitrous oxide is blown through it ,

I am hoping to obtain a large nitrous oxide cylinder shortly to research burn rate and thrust .

I have oxygen on tap as a comparison.

The reason for this sudden interest is I have found a source of small disposable cylinders of nitrous oxide .

Thee cylinders are slightly larger than the disposable co2 cylinders used for soda syphons

They are purchased in packs of 5 or 25

Using these cylinders for rocket motor research would be costly hence the larger nitrous oxide cylinder I propose to rent for a year .

The question is  can a viable model rocket be launched using a disposable NO2 cylinder and bitumen motor????.

 

If this work fails to produce a viable model rocket engine due to size/weight  thrust and duration constraints  I have the basis to build a variable controllable thrust large rocket motor for a bicycle or trike ride !!!!

if anyone has any  tech info  or would like to take part or borrow the cylinder or  for example does anyone know how oxygen and NO2 compare as  research using  bitumen and oxygen is a very cheap option as I have a large oxygen bottle and regulator for gas cutting on the workshop outside wall. do post or pm

 

 

 

 

 

 

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[Arthur Brown]

Nitrous oxide is suited because a relatively low pressure (70 Bar) holds 16g but sadly 16g wouldn't produce much impulse, it's just too small. A decent cylinder would weigh a few kilos than you need a lot of rocket to launch it and a lot of place for it to land.

 

I fear that the trail of dense black smoke would be a good indicator of the launch site. The telemetry would have to be good or the data may well be lost, Composite High Performance rockets usually make a good altitude or a very long range or both.

[cooperman435]

Are the disposable cylinders liquid or gas filled though Icarus?

 

I may be wrong but I was under the impression that the rocket lads use Nos in it liquid state to both reduce the pressure requirements of the rocket storage tank (its vented so constantly blows off pressure once its filled) whilst still carrying vast amounts of energy for that short period of time.

 

I suspect that the tanks your looking at therefore have to be heavier than desired as they hold full pressure for a proper length of time.

[JamesB]

There's a rather cool video from where "Bang Goes The Theory"  made something similar using peanut butter and toffee as a fuel, with nitrous oxide as an oxidiser, the results were rather impressive:

 

Separately, I've been assembling some nitrous injection hardware for my bike, the standard setup uses a refillable bottle containing the liquid (picked up via a dip tube in the gas bottle), which is injected into the intake, having the additional bonus of cooling the air as the liquid boils. Gas bottle specified linked below:

http://www.noswizard...s-brackets.html

 

I think the whole liquid / gas bottle argument isn't quite right, as if memory of physics classes serves me right, once you go beyond a certain pressure, the gas condenses to a liquid anyway, and conversely, a cylinder of liquid nitrous will always maintain the same pressure (at constant temperature), with more of the liquid boiling into a gas as the tank is emptied. Output pressure only drops when the tank is about to run out.

 

Anyhow, sounds like an awesome idea, very happy to help with any telemetry equipment that needs building!

[cooperman435]

You are correct James however when you consider a hybrid rockets short storage requirements it can alter slightly.

1 most gasses do yes indeed liquefy at pressure but this is often at higher pressures than are required to maintain that state

1 the tank is filled and then used straight away so never has to "hold" pressure or at least full pressure. It's essentially a liquid container able to hold only modest pressure to help slow down the boiling off of the liquid. This means you can store the same amount of liquid with a far thinner walled / lighter weight tank than if you had to hold it indefinitely at full pressure.

[Arthur Brown]

To determine whether a disposible Nitrous oxide capsule is enough, weigh the contents, work out the stoichemetry of the reaction and see how much bitumen that would use.

 

Then see whether that's the size rocket that you want/can fire

[icarus]

the disposable tanks are commercially for spray food catering creme,  and are very similar to the larger disposable co2 cartridges used by paintball and some airguns. They are heavier than needed but there should be sufficient thrust, I will check the weight of no2 held .

I normally home refill many canisters if they have a recent pressure test stamp on them .First having weighed them the air or residual gas is evacuated with a vacuum pump. They are then connected to my larger donor cylinders which are inverted if necessary for liquid withdrawal they are then check weighed . this works well with propane and butane their vapour pressure is about 200psi I can lower this dramatically especially for butane by putting the donor cylinders into a chest freezer before use . If I am going to make a filling rig for NO2 cylinders   then pressure handling of 100 bar or more will be necessary . so its time to consult the hydraulics catalogue unless anyone out there knows of a design using off the shelf hydraulic fittings and pipe .

 

Meanwhile i can set up a metal test bench with a nitrous oxide supply of variable pressure delivery  with on off solenoid control  and cctv monitor camera along with a horizontal track and strain guage to measure thrust .If anyone else out there would like to test hybrid fuels they are welcome to use it' Location  n W Leicestershire  600M from nearest building +  CCTV  is painless if you have a cato!.

 

Thanks JamesB for the link to the video.   The nozzle is either pressed out of bentonite in an iron reducing fitting or moulded and baked in fireclay . I also have fine powdered porcelain available from a local refractory brick company if anyone wishes to try it as a component to aid wear reduction in rocket nozzles. I havent had time to experiment with it yet as pyro is my winter hobby  

[cooperman435]

Ahhh now I think I understand. We are refering to the small capsule cylinders, the same used by the "youth" of today to get a high from as published by the media recently?

 

In which case it is a gas capsule not liquid and would hold far too little gas to create a reaction energetic enough to justify the weight of the capsule.

[Arthur Brown]

To get the rate of heat/thrust production needed it's necessary to have liquid flow into the fuel element. N2O is used as the gas compresses to liquid at a relatively low pressure enabling a light weight vessel to contain enough oxidant for flight. Liquid Oxygen is also used (LOX) but this requires refrigerating the liquid to keep the triple point low enough, also LOX is much more hazardous than N2O -almost everything burns in liquid oxygen -metals and organics probably some rocks too

[digger]

Not sure what the triple point has to do with anything, I don't think anyone was talking about blocks of oxygen.

 

There should be no reason why you can't get enough gaseous oxidiser into a combustion chamber to produce good thrust, it just won't be able to carry the oxidiser cylinders due to their weight.

 

The other engineering issue is the heat produced by the reaction, the temperature experienced in an oxygen motor will be much higher than a N20 motor as there is no heating of inert N2 exhaust and change of state. 

 

In liquid motors the fuel and oxidiser can be used to cool the chamber wall using the heat of vaporisation. If you look at large motors they even use the liquid to cool the bell and nozzle.

 

But I don't see why a demonstration motor can't be produced with a few clever approaches to cooling. Water to steam?

 

I may not fly to the moon, but could push a cart (not sure I would want to ride it though).

 

It does have to be said liquid N20 has a large number of very useful properties for the amateur, which make easy to build simple motors.

 

Maybe we can exchange designs in the future Icarus. I am hoping to have a play next year, but I want to build something a bit different. So I am hoping to build a fuel injected areospike motor based on kerosene and HTP(high test peroxide). But only a small bench scale motor.

 

"once you go beyond a certain pressure, the gas condenses to a liquid anyway" almost right, gases have a critical temperature above which they will always exist as gas for oxygen it is -118C

[icarus]

thanks for the excellent suggestions .I am going to make a motor test bench up with a nitrous oxide feed, and an  oxygen feed  from commercial cylinders with gauges and control solenoids plus a wheeled  cart on a track  with strain gauge  to strap motors to and measure thrust, Also a cctv camera behind a clear screen , perhaps a large fan  to suck and direct the smoke ?? Has anyone any experience or advice in this area????        it can become part of the safe test area I am hoping to build up.