Automatic reloading solid fuel rocket.
Copy write 2004 by William Arden. Redistribution is allowed provided that this notice is included

Phase 1
Rocket Test 1 Smokeless powder and pressure regulator

1         Overview

Rocket efficiency increases with higher pressures, however this requires stronger casings. This means that it would be better to have a small casing and load more fuel into the rocket as it is used.

The concept is to make one small engine and load individual grains into it while it fly's. I know this has been tried before, however I plan on combining several different concepts. Each grain would burn for 1-3 seconds and then a small motor will breach load a new grain. The thrust of the engine would then cause the fuel grains to move down the tube and small flaps would prevent them from moving back up the tube as the shuttle moves back.

Next I want to explore high pressure engines since the chamber is so small a high pressure can be handled without making it very heavy.
The only problem is "detonation". I plan on making an automatically adjusting aerospace engine to control the pressure as the fuel increases it's burn rate.

Rocket and nozzle

Click for a larger image.

The fuel pellet would have a hole in the center and would burn on both the outside and the inside.
A small amount of heat sensitive starter material would be added to the end of the pellet.
Ablative coatings would prevent the shell from overheating.

Pros: higher thrust.
Cons: More complex, changes balance point.

Rocket Test 1 Smokeless powder and pressure regulator

This first test is designed to test the pressure regulator to see if it can regulate the pressure at a specific point regardless of the fuel's burn rate.

The feedback control mechanism must be stable to prevent oscillations, however there are two factors working against it.
  1. The mass of the valve causes a small delay, which will make it oscillate at some frequency.
  2. The fuel burn rate increases with pressure so that when the pressure is too high it will get higher.
  3. Opening the valve will temporally increases thrust, which will apply more force to the assembly.
To overcome these a mechanism must be added that can change the valve position based on the rate of change of pressure.

The mechanical version (to the right) works by allowing some of the high pressure gasses to push a piston, which reduces the required spring pressure. Then when a pressure change occurs the small hole prevents the piston from changing pressure and the valve opens or closes faster.

March 18 2006 update