Half Cat Static Test 5 - March 23, 2021

• Success

• Full data acquired

• Changes from previous test: None with the engine (Substantially more weight added to test stand legs)

The final static test was successful in all regards, especially photography, which provided excellent imagery of the Mach diamonds at various stages of operation. For whatever reason, Half Cat has several distinct phases which includes the extremely fiery portion that appears in every test and temporarily obscures the Mach diamonds in this video. Counterintuitively, this fiery phase corresponds to the period of highest thrust. The exact mechanisms behind the thrust curve aren’t well understood (notably, what causes the distinct plateaus in thrust) but a leading theory is that the pressurization piston does not slide consistently down the length of the tube, leading to varying fuel pressure.