longest burning rocket propellant

[darrel.h]

Hello all,

I have finally completed my sun seeker rocket and have gotten clearance(from the government) to fly it. Now I need to make the propellant. Does anyone know of any propellant that burns long? It also need to be low speed because if the rocket goes too fast, the control fins will shear off. I need the propellant to last about 20 seconds or so. FYI, the rocket will be traveling at about 120 to 150 KPH (yes it is a bit slow). The rocket motor is 2 feet long and 2 inches in diameter. Any help would be greatly appriciated!

Darrel

[Zippiot]

Take a look at a cross section of the space shuttle's boosters. They run for 2 mins, but i donno have a pic...

Keep in mind (as I am sure you know) propellant will burn at a constant (or predictable) rate, so the larger the engine the longer it can be made to burn. Ammonium percholrate is the propellant most used b/c it yeilds lots of oxygen for its weight.
Percholates are hard to ignite
Chlorates are dangerous and unpredictable
Nitrates are cheap and easy but yeild lower than the others
Calcium sulfate is a great high temp oxidizer, but I donnot know of the particular fuel for using with it, most likely aluminum or magnesium. It is common plaster of paris, so if it can be made to work it is cheap and common.

Magnesium sulfate (epsom salts) will slow the burn of rocket fuel, but I have noticed it choking the nozzle if too much is used.

Maybe used a bates grain, and have each grain have a different styled core and burn rate modifiers:
http://www.nakka-rocketry.net/oxidex.html
So lets pretend you are using Candy fuel (kno3 and sugar). Have the first grain have an uninhibited grain with iron oxide as the modifier, the second grain be regular candy, and the third have magnesium sulfate as a modifier to slow its burn down.


Or just stage it...

[darrel.h]

I am looking for about 75 newtons of impulse. I can't use the Rocsim because I am using Linux and I have removed DOS.

[MJD]

I am looking for about 75 newtons of impulse. I can't use the Rocsim because I am using Linux and I have removed DOS.

In a 2" motor this can easily be achieved using a fairly fast burning composite propellent in an end burning configuration, but if you are new to motor making you have quite a ways to go before you're ready to design and build such a motor. You will need substantial case insulation and a nozzle that will not erode into nothing over the burn time. Good luck!

[Jim Berquist]

If you can come up with a 2" motor that will burn 20 seconds and loft a rocket, Your the Man!!!! Using Known propellants, Big and large means long burn time...Going back to the Estes Rocket motor, A D8-0 burn time is about a second. Are you talking Impulse time or continuous thrust. You don't get continuous from a solid motor that I know...Liquide fuel and Ox gives you a flat line on thrust for a while. Then it curves and tapers off like solide...