16Litre Tri Booster Multi-Stage Rocket
The largest rocket I have built to date. The rocket is multi-stage, designed so that the booster section disconnects once it has de-pressurised and allows the top half of the rocket, the sustainer, to then shoot off and achieve even higher altitudes.
The booster section is comprised of 3 booster segments. Each booster segment is made with two 2L bottles joined at their bases with Robinson couplings. A PVC tube is gaffa taped along the length of the boosters to provide a skeleton to booster section. On top of this central skeleton is the staging mechanism. The staging mechanism is made with a garden hose connector with the spring removed. Instead Springs are attached to the hose connector to pull it down when the servo removes the latch. One of the booster segments has a pressure switch screwed on the top, this is used to detect when the booster section de-pressurised. Both the servo and the pressure switch are connected via audio connectors and wires to the flight control circuit housed in the sustainer. Audio connectors are used because they pull apart easily when the rocket separates.
The sustainer is based on a standard 4L rocket design and is flown with the optical apogee detector used on other rockets. However the circuit has been modified to also trigger the servo on the booster section when the pressure switch engages.
Due to the 3 boosters a special launcher had to be made. The launcher is made from 3 hose connectors with the outside cover removed, this would normally mean that nothing would be holding down the rocket and stopping it from shooting off. However a metal peg is placed through a hole in the central skeleton pool on the booster segment to hold the rocket down onto the launcher. 6mm copper pipes are also inserted into the hose connectors, the copper pipes are high enough that they are above the water fill level in the rocket. The pipes are there to make sure that whilst air can equalise between the boosters, important since 1 booster feeds the sustainer and would otherwise be low on pressure, water cannot. Without the pipes either water levels or air pressure would be different between each booster segment, this would make the rocket veer off to one side during flight.