>The one time we did try making a rocket, potassium chlorate and sugar formed
>the fuel mix. It reacted too quickly.... Fortunately, we had 1) used a heavy
>cardboard tube as the engine case, and 2) given it lotsa room to do its thing.

I've tried that too, but without any success. The rocket either doesn't fly
at all or it flies rapidly in every directions. The latter is more likely to
happen. I have always tried with sodium chlorate ( it's another favorite 
chemical of mine), since it cost only one dollar a kilogram and is readily 
available in 50 kg drums. Potassium compounds are expensive and hard to get
in technical grade here. I have come to the conclusion, that all mixtures 
of chlorate with any porous fuel (pulver) yield a kind of a powder, which can 
only explode or burn very slowly if not confined. But, if the fuel is not 
porous, it is possible to make rocket fuels of sodium chlorate.

The answer is a composite fuel dense enough to prevent a full detonation.
I have used polyurethane and polyester resins. So far the best I've found
is polyurethane. The specific impulse of the fuel lies around 120 to 180 s,
depending on the recipe. (Higher with aluminum mixtures). As an example
a 40 gram motor lifts a 150 gram load up to about 300..400 meters. The
engine burns about 1 to 1.5 seconds. Without any payload (except the stick)
an engine reaches supersonic speeds for sure, at least it makes a bang when
passing by. 

I have used these small engines to bring up different kinds of stars, bombs,
etc. i.e. as a fireworks rockets. They could readily be used for model
rocketry as well, in fact I have made stickless rockets, which I launch
from a 0.5 meter long tube. They fly like bullets, I have only the engine
and small aluminum fins behind it. The best of all, they cost 10 to 15 cents 
each.

However, these engines have their drawbacks. They reach the maximal
thrust towards the end and you have to take a long tube with heavier
loads to allow the rocket accelerate enough. Also, they produce an
intense yellow light, it is something like flying sodium lamps. The
light may prevent you from seeing the stars in the payload, if the
engine still burns after the stars have been ignited.

Again, the Greenpeace should approve these engines, they produce only
carbon dioxide, water vapour and sodium chloride in their smoke!
(theoretically, of course)

3P