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Propellant and propellant manufacturing

Zinc-Sulphur

Zinc and sulphur propellant was used from the beginning 1965 to 1973 when it was abandoned for much more powerful propellants. Both zinc and sulphur is a powder that is mixed  by hand. This propellant is easy to start with, but is a very low-energy propellant. The zinc is very sensitive to oxidation and therefore you can not fully control its behaivour. By adding a few % of aluminum powder you can increase it's performance. Not used by professionals. More smoke and fire that power!!

Asphalt - Potassiumperchlorate

Many tests was made during 1971-1973 with this propellant. But Potassiumperchlorate is wellknown to have a high "burningrate exponent" and therefore is rather complicated for amateurs. A high "burningrate exponent" of 0-6-0.8 is a figure that describe the propellants sensitivity to different pressure in the combustionchamber.

PVC - Ammoniumperchlorate

In 1971 we started experimenting with PVC and ammoniumperchlorate (AP) propellants. AP is wellknown to have a low "burningrate exponent" and is therefore less sensitive to different pressure in the combustionchamber. One disadvantage is that PVC need a curingtemperature of 150 degrees celsius. There is a risk by heating the whole motor filled with propellant to this temperature. HTPB reduce this risk mostly.

 
Vacuummixer deassembled 

Vacuummixer assembled 

Filling the mould from the vacuummixer by pressurized nitrogen. The slowly floating propellant can be seen in the clear plastic tube.  Propellant i white.

Heatoven for curing PVC-AP propellant. Curing-temp=150-155 degrees Celsius. Heatingup time is several hours. The oven can be remotly controlled and up to five motors can be cured at same time.

Vacuummixer with capacity of 5 kg propellant

 


Vacuummixer

 

Hydroxyl Terminated Poly Butadien (HTPB) and Ammoniumperchlorate

A couple experiments and launchings carried out with success. Curing/hardening of HTTPB takes longer time, but require lower temperature (=security for amateurs).

Thiokol and Ammoniumperchlorate

Some experiments carried out with success.

The Strandburner ("Crafoordbomb") to meausure burning rate vs. pressure.

A Strandburner was developed and built end of 1973. This equippment is used to cheap and easily find out burningcharacteristics of propellant. In a closed pressurized chamber a thin string av actual propellant is ignited from the end. The strand of propellant have a couple of thin metallstrings that is burnt off by the flames. By measuring the time and distance between these metallstrings then the burningrate can be calculated. Different propellant mixtures tested at different pressure will let yopu know the exact behaivour of your propellant.

One small problem is to find/construct a valve that keep the pressure be constant during the test. Even a short thin strand of propellant will create a large amount of gas. Nitrogen is used to achieve the desired pressure. The strandburner must also be connected to a automatic or manuel system that measure the time.
 


The 4 mm thin propellandstrand is mountet in the middle. The very thin metalsstrings can also be seen on this photo. Nitrogen is used for gaspressurizing.

Here the complete strandburner is ready for a test, but on this photo the exhaust valve is not mounted. This valve must keep unchanged pressure in the chamber.
   
   


 

Copyright (c) Raketgruppen IRA/UT 2004.
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Last updated: november 09, 2005.

 

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