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Gas Generator and Exhaust System
This system consists of the gas generator, gas generator control valve, turbine exhaust system and exhaust manifold, heat exchanger, and oxidizer turbine bypass valve.
GAS GENERATOR
The gas generator is welded to the fuel pump turbine manifold, making it an integral part of the fuel turbopump assembly. It produces hot gases to drive the fuel and oxidizer turbines and consists of a combustor containing two spark plugs, a control valve containing fuel and oxidizer ports, and an injector assembly.
When engine start is initiated, the spark exciters in the electrical control package are energized, providing energy to the spark plugs in the gas generator combustor. Propellants flow’ through the control valve to the injector assembly and into the combustor outlet and are directed to the fuel turbine and then to the oxidizer turbine.
GAS GENERATOR CONTROL VALVE
The gas generator control valve is a pneumatically operated poppet-type that is spring-loaded to the closed position. The fuel and oxidizer poppets are mechanically linked by an actuator. The gas generator control valve controls the flow of propellants through the gas generator injector.
When the mainstage signal is received, pneumatic pressure is applied against the gas generator control valve actuator assembly which moves the piston and opens the fuel poppet. During the fuel poppet opening, an actuator contacts the piston that opens the oxidizer poppet. As the opening pneumatic pressure decays, spring loads close the poppets.
TURBINE EXHAUST SYSTEM
The turbine exhaust ducting and turbine exhaust
hoods are of welded sheet metal construction. Flanges utilizing dual (Naflex) seals are used at component connections. The exhaust ducting conducts turbine exhaust gases to the thrust chamber exhaust manifold which encircles the thrust chamber approximately halfway between the throat and the nozzle exit. Exhaust gases pass through the heat exchanger and exhaust into the main thrust chamber through 180 triangular openings between the tubes of the thrust chamber.
HEAT EXCHANGER
The heat exchanger is a shell assembly, consisting of a duct, bellows, flanges, and coils. It is mounted in the turbine exhaust duct between the oxidizer turbine discharge manifold and the thrust chamber. It heats and expands helium gas for use in the third stage or converts liquid oxygen to gaseous oxygen for the second stage for maintaining vehicle oxidizer tank pressurization. During. engine operation, either liquid oxygen is tapped off the oxidizer high – pressure duct or helium is provided from the vehicle stage and routed to the heat exchanger coils.
OXIDIZER TURBINE BYPASS VALVE
The oxidizer turbine bypass valve is a normally open, spring-loaded, gate type. It is mounted in the oxidizer turbine bypass duct. The valve gate is equipped w’ith a nozzle, the size of which is determined during engine calibration. The valve in its open position depresses the speed of the oxygen pump during start, and in its closed position acts as a calibration device for the turbopump performance balance.
Control System
The control system includes a pneumatic system and a solid-state electrical sequence controller packaged with spark exciters for the gas generator and the thrust chamber spark plugs, plus interconnecting electrical cabling and pneumatic lines.
PNEUMATIC SYSTEM
The pneumatic system consists of a high-pressure helium gas storage tank, a regulator to reduce the pressure to a usable level, and electrical solenoid control valves to direct the central gas to the various pneumatically controlled valves.