Posted on July 7, 2016
Building a model rocket can be fun, but what's more fun than that, an intercontinental ballistic missile. But to save on time I'll just simplify it and make it not explode. The basic concept is a rocket with an IMU that can adjust itself in real-time and make course corrections.Specs
By melting down aluminum cans and other various aluminum pieces, I was able to pour the resulting molten metal into steel cans to form cylinders that could be turned on a lathe to form very nice aluminum chunks.
The injector body design is loosely based on the design found here.
The angle of the injector ports is 15 degrees. Next, the combustion chamber and injector cap.
There were two main types of fuel I had to decide on, solid or liquid fuel. A hybrid engine was out of the question. If I had chosen solid, it probably would have been a mix of sugar and KNO3. A better choice would be liquid though. The propellant would be some hydrocarbon i.e gasoline and the oxidizer would end up being H2O2 since obtain liquid oxygen did seem very easy.
Hydrogen Peroxide bought from a store only contains 3% Hydrogen Peroxide and the rest is water. I need that concentration to be a little higher. Since the boiling point of water is 100C and the boiling point of H2O2 is 150C, I could just boil off the water. The other alternative would have been to freeze the water off, but since there is less than a degree difference in freezing points, this seemed difficult.
I wanted there to exist some degree of control over the rocket. I also wanted there to be some data logging as well. I designed an AVR based control module that uses accel and gyro data to control servos that move the rocket engine to keep the rocket upright. Below is the original control module schematic.
After finding a few suitable pieces of aluminum, I turned them down to the size and shape I need. I then used a mill to drill the nessessary holes in the sides for the bolts. Having the outer holes larger and then tapping the inner holes makes short work of the rotational mechanism. This design allows for movement in two axes. This is controlled by two servos attached with connecting arms. The rocket engine will be connected in the center ring.
By using data from a gyroscope and an accelerometer, the current angle of the rocket can be determined and the servos can be adjusted to counteract any rotation.