3Cat/8

THRUST: 75 lbf

FUEL: isopropanol

OXIDIZER: NITROUS OXIDE

bURN TIME: 10 - 15 SECONDS

3Cat/8 was a rocket of similar architecture to 1Cat/4, but designed for much higher performance. It had a pair of pneumatic Half Cat valves triggered by a cable cutter severing the pilot line, and was ignited by a cartridge igniter that fired through the injector face.

3Cat/8 featured a regeneratively cooled combustion chamber called “Tabby”. This style of regen circuit was made to maximize manufacturability, and is easily produced with a lathe and mill. For survivability, the pressure and temperature in the chamber were kept low, allowing the aluminum chamber to withstand steady-state conditions without film cooling. No damage was observed on its flights, where the motor burned for ~11 seconds.

Tests & Launches

Launch 1: 8750’

Launch 2: 1419’

LAUNCH 3: 9850’

No static test has been conducted on 3Cat/8, since its purpose was to demonstrate that relatively good performance liquid rockets are attainable with a modest budget and manufacturing capability. Most of 3Cat/8’s length was exposed propellant tank, but the airframe was lightweight hand-laid composite taken from an older rocket designed for commercial solid motors.