On May 10th 2015 Copenhagen Suborbitals tested the first version of the BPM5 engine, a 5 kN liquid bi-propellant rocket engine running on liquid oxygen and ethanol. It turned out to be the most efficient liquid propellant engine we have ever made, this is the short story of how we designed, build and tested it.
The main components of the engine are the LOX dome, the injector and the regeneratively cooled combustion chamber. The gas inside the chamber is about 2300 degrees centigrade, so proper cooling is essential!
The combustion chamber and cooling jacket shell are both made by metal spinning. This is a process where a solid steel cylinder is machined to the desired shape such that it can be used as a mandrel. A steel tube is then pressed onto this and simply shaped by pressing the tube against the mandrel.
After spinning the parts were test assembled. The flange and the LOX dome were fabricated in house but for 5 axis CNC milling of the injector we had to ask for help from Protobuild.
After nickel plating the parts were fitted together...