30 replies to this topic

[Dragonsinger]

Hi Guys

I have joined this forum in order to research slow burn propellants. I will most probably never darken your message board again after I have done this.

I am coming at this from a different angle to most of you since I am not amazingly interested in developing new and super efficient formulae. What I really want to do is develop, learn to produce, a small solid fuel rocket motor which is capable of powering small scale free flight and R/C model aircraft. These things are normally weighed in Grams and usually well under 250 Grams so I do not need high power and fast burn rates. Have a look"HERE" to see what I mean.


I need something with a long, 20 seconds upwards, burn and a thrust of between 50 and 200 Micro Newtons. It must be a simple mix and achievable without the necessity of having to replace my garden shed if it goes wrong.

The “normal” tool would be either a Jetex motor or a Rapier solid fuel rocket, both of which were developed to provide thrust in the minute quantities required for this kind of model but due to the increasing paranoia about terrorist action there are problems with postage of the Rapier and the Jetex has once again gone out of production.

So there you have the problem. Can anyone help?



Regards

Jim

[a_bab]

Your problem is that the fuel is not only supposed to burn slowly, but also with a low temp. Jetex barely went over 450 degrees C I guess.
Rocket fuels are of several kinds, but the usual oxidizer/fuel mixtures burn past 1000 degrees C and the use of a metal case (as in Jetex) is strictly forbidden due to a serios explosion hazard.


"Jetex" type engines used guanidine nitrate as a fuel. I really doubt you'd be able to get your hands on it, as it's really an elusive chemical and a HE, so you're going to raise more then some eyebrows. However it can be synthesized with the proper determination as the precursors are easy to find.

As an alternative you can probably use nitrocelulose. There are different grades available, and it's used in the paint industry. A plastic called "celluloid", still in use can also be seen as a weak, slow rocket fuel in my childhood rocketry experience. Ping pong balls are made of it (althogh I have seen some that are not). A "good" ping pong ball can be easily recognised as being made of celluloid by scratching it with the finger nail; a mentholated smell is then detected (it's camphor, as celluloid is a mixture of camphor and nitrocellulose).

An interesting read you may know about: http://www.jetex.org...?num=1254520818

[Dragonsinger]

Hi a_bab

Many thanks for the reply.
I do know about Jetex.org but I still have to come back to the non- availability problem. The Rapier rockets are still manufactured but it has become illegal to send them through the post so if I want to go to the Check Republic to collect them I can. The Rapier uses a cardboard casing but I have no idea about the burn temperature. I have to assume that the cardboard casing acts as an insulator and the exhaust is always channelled away from any flamable bits of the airframe so I may be able to overcome the temperature problem. I have found an article on using fuses to make a small rocket. If I can work out how to put a .PDF on the board. I will publish it. It looks as though I may be able to adapt this to decrease the power so it will be worth a look. I'm not too far from Standard [Black Cat) in Huddersfield so I might get some info from them.
Thanks again
Jim

Edited by Dragonsinger, 05 December 2011 - 04:12 PM.

[a_bab]

You are welcome Dragonsinger.

From the discussion link I posted you can see that the Rapier uses a ammonium perchlorate/zinc kind of compo, that would burn with high temperatures. Please do read it as it clears down many questions you may have. The cardboard casing is designed such that it could whitstand the temperature during the burning time.

[Dragonsinger]

Hi Again
Had a read through the link and it looks as though it will need to be a home built Rapier substitute.
Since I have never done any of this before does anyone know the ease of availibility of the necessary chemicals in the UK?

Regards
Jim

[Mortartube]

If it needs to be low thrust and easy to make Zinc/Sulphur may serve your pupose. It does need a thick case though as it burns hot.

[Mortartube]

If it needs to be low thrust and easy to make Zinc/Sulphur may serve your pupose. It does need a thick case though as it burns hot.

[Deano 1]

If it needs to be low thrust and easy to make Zinc/Sulphur may serve your pupose. It does need a thick case though as it burns hot.

The things some of you do to get your post count up, tttttttut

[Mortartube]

The things some of you do to get your post count up, tttttttut

Consider it my Christmas bonus

[Dragonsinger]

Hi Guys
Has anyone tried "THIS" and can we get the Visco fuse here in the U.K?

Thanks
Jim

[whoof]

The loss of Jetex is a real pain, i have several models stuck in the attic.
Did some experiments with Estes motors which were generally disastrous.

Aluminium reloadable APCP rockets are available,
I did wonder if the core or slot were somehow filled in, it would create an end burner which would give an extended lower power thrust.
APCP burns relativley slowly.
Not tried it practically though

[whoof]

So there you have the problem. Can anyone help?
Regards

Jim

This UK co does one of the Rapier rockets.
http://www.google.co...oSCiP0jw6D65o8Q

As he probably has regular order/ supplies you could ask him to get whatever it is you are after.
Not used him myself but i managed to get a special from another supplier once, albeit i had to wait 3 months.

Edit.
Oops that is italian based although they do ship.
Try
http://www.google.co...GxOCRP37nV5F-bA

http://www.google.co...Q_FwhDB5cA8sLCg

He travels to rocket meets occasionaly with a mobile shop, which is handy for avoiding costs of ADR provided you can collect.

Edited by whoof, 06 December 2011 - 07:31 PM.

[starseeker]

Hi Guys
Has anyone tried "THIS" and can we get the Visco fuse here in the U.K?

Thanks
Jim

To answer your question,visco is easily obtained in the uk and perfectly legal to own/store.

[dr thrust]

this looks promising

A slow burning propellant. Great for sustainer engines.
Ammonium Nitrate 70%
Ammonium Perchlorate 10%
Polyester Resin 18%
Powdered Charcoal 2%
Not very powerful but useful. The charcoal helps keep the combustion steady.

[Mortartube]

Hi Guys
Has anyone tried "THIS" and can we get the Visco fuse here in the U.K?

Thanks
Jim

I have tried this, and they work. But only burn for about 2 seconds.