on liquid bipropellant rocket engines. Specifications Number flown: 77 (Delta 2000 configuration) Dry mass: 300 pounds with columbium (niobium) nozzle extension installed Length: 51 inches – gimbal attachment to nozzle tip (minus nozzle extension) Maximum diameter: 34 inches (minus nozzle extension) Mounting: gimbal attachment above injector Engine cycle: pressure fed (15.5 atm reservoir) Fuel: 50:50 NO/UDMH (Aerozine 50) at 8.92 kg/s Oxidizer: dinitrogen tetroxide at 5.62 kg/s Oxidizer:fuel ratio: 1.60 Thrust, vacuum: 42.923 kN Specific impulse, vacuum: 303s Expansion ratio: 16:1 without nozzle extension; 43:1 with nozzle extension Cooling, upper thrust chamber: film Cooling, lower thrust chamber: ablative quartz phenolic; Cooling, nozzle extension: radiative Chamber pressure: 7.1atm Ignition: hypergolic, started by 28V electrical signal to on/off solenoid valves Burn time: 500s for total of 5 starts; 10 × 350-s single burn Delta usage The TR-201 engine was used as the second stage for 77 Delta launches between 1972 and 1988. The engine had a 100% reliability record during this 15 year operational period. References Rocket engines using hypergolic propellant Rocket engines using the pressure-fed cycle