H-1 Engine Facts:
Length 8.5 ft Width 5.5 ft Thrust (at sea level) 200,000 lb Specific Impulse 263 sec Rated Run Duration 155 sec Flowrate: Oxidizer 526 lb/sec (3330 gpm) Flowrate: Fuel 236 lb/sec (2092 gpm) Mixture Ratio 2.23:1 oxidizer to fuel Nominal Chamber pressure 633 psia Weight, flight config: Inboard 1780 lb Weight, flight config: Outboard 2020 lb Expansion Area Ratio 8:1 Note: these figures are for engines used on SA 205 and previous
H-1 ENGINE DESCRIPTION
Each H-1 engine is rated at 200,000 pounds of thrust. The eight-engine cluster used on the S-IB stage produces a total of 1.6 million pounds of thrust. While these eight engines are basically the same design, there are important differences between the four inboard and the four outboard engines. Outboard engines are equipped with two component systems which are not employed on the inboard engines: an aspirator and gimbal outriggers. Components of the engine are mounted on a single, regeneratively-cooled thrust chamber of stainless steel, tubular wall construction.
H-1 ENGINE SYSTEMS DESCRIPTION
Major systems common to both inboard and outboard engines are: thrust chamber and gimbal assembly, exhaust system, gas generator and control system, propellant feed system, turbopump, fuel additive blender unit, and electrical system.
Thrust Chamber and Gimbal
The thrust chamber and gimbal assembly includes a gimbal, LOX dome, injector and hypergol container, and thrust chamber body. The thrust chamber receives the propellants under turbopump pressure, mixes and burns them, and imparts a high velocity to the expelled combustion gases to produce thrust for vehicle propulsion. The H-1 engine thrust chamber also serves as a mount or support for all engine and certain vehicle hardware.
GIMBAL
The gimbal secures the thrust chamber to the vehicle thrust frame and is mounted on the thrust chamber dome and elbow assembly. The gimbal is essentially a universal joint consisting of a cross-shaped unit incorporating bearing surfaces, upper and lower retainers, pillow blocks, and thrust vector aligning slides.
Purpose of the gimbal bearing assembly on the outboard engines is to permit a thrust chamber pivotal movement, which results in a maximum angle of 10 degrees from the normal (14 degrees when both actuators are extended) in the plane of the actuators as thrust vector control actuation movement is transmitted to the thrust chamber gimbal outriggers. The gimbal provides for positioning and thrust alignment capabilities.
OXIDIZER DOME
The oxidizer dome encloses the forward end of the thrust chamber combustion area, provides a mount for gimbal and thrust chamber assembly, and transmits engine thrust forces to the vehicle structure. Oxidizer from the turbopump enters the thrust chamber through the elbow of the dome assembly. The elbow is also the takeoff port of the gas generator oxidizer bootstrap line.
THRUST CHAMBER INJECTOR
The purpose of the injector is to meter the amount of propellants entering the thrust chamber combustion area and inject these propellants in a prescribed pattern, thereby ensuring satisfactory combustion. The injector incorporates 21 concentric circular passages (rings). Fuel and oxidizer are distributed through alternate rings; fuel flows through the outermost ring and in each alternate ring.
Propellants flow through angled orifices in the rings and into the thrust chamber causing the propellants to impinge in the combustion area in a like-on-like pattern (oxidizer-on-oxidizer and fuel-on-fuel).
Baffles, consisting of six copper fins and a copper hub, are mounted on the face of the injector. The hub is mounted over the fourth fuel ring. The six fins extend radially from the hub to the outer diameter of the injector face to divide the area equally. Holes drilled in the baffles mate with corresponding holes in the fuel and oxidizer rings allowing fuel and oxidizer to flow through the baffles into the combustion area. The baffled configuration results in increased combustion stability.
The welding of the hypergol container to the injector plate assembly has created the unitized injector and hypergol container. Pyrophoric fluid flows from the hypergol container through seven passages in the injector to the igniter fuel housings brazed into the face of the injector.
The injector is the primary thrust-experiencing component. Combustion zone pressure acts upon the injector face area, producing a thrust force which is transmitted from the injector to the oxidizer dome, to the gimbal, and subsequently, to the vehicle structure.
THRUST CHAMBER BODY
The thrust chamber body is a deLaval nozzle (100% bell) and consists of a combustion section, a converging throat section, and a diverging section through which combustion gases are expanded and accelerated. The chamber body wall is constructed of longitudinal stainless steel tubes joined together by furnace brazing and retained by external stiffening rings and tension bands. The tubes are of orthogonal cross section and are shaped to conform to thrust chamber contours. This type of construction permits thrust chamber regenerative cooling during engine operation by fuel flow through the tubes. A tapered fuel manifold gives equal flow to each dowm tube, providing a more even fuel flow through the thrust chamber cooling tubes. On inboard engines the thrust chamber body incorporates an improved design to accommodate the installation of the inboard turbine exhaust system.
Exhaust System
The engine exhaust system on the outboard engines consists of a turbine exhaust duct, heat exchanger, heat shield, and a heat exchanger LOX supply line. The thrust chambers on all outboard engines have an aspirator installed to distribute the exit flow of exhaust gases. Inboard engines have an engine-mounted turbine exhaust system consisting of a turbine exhaust hood, heat exchanger, turbine exhaust duct, heat shield, and heat exchanger LOX supply line.
TURBINE EXHAUST HOOD
The turbine exhaust hood is a stainless-steel, welded elbow assembly incorporating two mating flanges, two doubler rings, a bellows section, and an integral liner to protect the bellows section. The bellows permit the degree of movement required by the system.
TURBINE EXHAUST DUCT
The turbine exhaust duct is a curved, stainless-steel assembly consisting of mating flange, forward support bracket, bellows section, curved duct, and aft support bracket. The bellows section permits the degree of movement required.
HEAT EXCHANGER
The heat exchanger is a welded, stainless-steel assembly consisting of an outer shell, an inlet flange, an outlet flange, a helix-wound four-coil system, and coil inlet and outlet manifolds. Turbine exhaust gases passing through the shell heat the coils. Liquid oxygen, under turbopump pressure, enters three coils of the four-coil system to be converted to gaseous oxygen for pressurizing oxygen tanks.
ASPIRATOR
The exhaust gas aspirator is a welded, Hastelloy C shell assembly installed over, and extending beyond, the thrust chamber exit on all outboard engines. The aspirator prevents recirculation of fuel-rich gas generator exhaust gases into the missile boattail during flight, by directing these gases into the exit flow stream. The aspirator is welded to the thrust chamber forward channel and located approximatelv 20 inches forward of the thrust chamber exit.
Gas Generator and Control System
The gas generator and control system consists of the liquid propellant gas generator, ignition monitor valve, purge check valve, orifices, bootstrap lines, and the hose and line assemblies which make up the series control line. The gas generator and control system control engine start sequencing and supply power to drive the turbopump.
LIQUID PROPELLANT GAS GENERATOR
The liquid propellant gas generator (GG) produces combustion gases, during mainstage operation, to drive the two- stage turbine, which in turn supplies power through a reduction gear train to drive the propellant pumps.
The assembly consists of the gas generator control valve, injector assembly, and combustion chamber. The control valve oxidizer poppet and fuel poppet are opened by pressure sensed at the thrust chamber fuel injector manifold when main propellant ignition is established. The propellants flow through the open poppets, through separate manifolds and orifices in the injector to the combustion chamber. The propellants are ignited by the solid propellant gas generator hot gases augmented by the two auto-ignition igniters. The gas generator injector is a uniform mixture- ratio type featuring two fuel streams impinging on a single oxidizer stream.
GAS GENERATOR CONTROL VALVE
The control valve is a normally. closed valve with linked poppets to control the flow of propellants to the gas generator injector and combustion chamber. The valve contains a fuel poppet, oxidizer poppet, piston, fuel poppet spring, and oxidizer poppet bellows assembly. These units are contained on a single housing which is bolted to the injector.
The control valve is opened by control (fuel) pressure at main propellant ignition. This pressure, sensed at the thrust chamber fuel injector port, forces the piston on the fuel side of the valve down to open the fuel poppet. A yoke integral with the piston opens the oxidizer poppet. During engine shutdown, the control pressure decays, and the fuel and oxidizer poppets are closed by spring pressure.
The propellant injector cavity design permits an oxidizer lead during start to prevent detonation, and the yoke design ensures a fuel-rich cutoff to eliminate the possibility of turbine burning.
IGNITION MONITOR VALVE
The ignition monitor valve (IMV) is a three-way, pressure-actuated valve that physically senses satisfactory thrust chamber ignition before directing control (fuel) pressure to open the main fuel valve. The valve is mounted on the main fuel valve and is connected to the main fuel valve opening port by a close-coupled orifice fitting.
During engine start, the main LOX valve opens the igniter fuel valve which directs igniter fuel to the hypergol container and fuel pressure to the ignition monitor valve inlet port for subsequent main fuel valve actuation. When satisfactory thrust chamber ignition has been achieved, the pressure buildup sensed at the thrust chamber fuel injector manifold will open the ignition monitor valve. If ignition is not established, ignition monitor valve actuation pressure will not be available; therefore, the main fuel valve will not open.
During engine shutdown, decreasing pressures allow the main fuel valve actuator spring to close the valve and the ignition monitor valve to vent and close.
SOLID PROPELLANT GAS GENERATOR
The solid propellant gas generator (SPGG) is a solid propellant cartridge that bolts to the liquid propellant gas generator flange and supplies power to the turbine for engine starting. It is a disposable unit that cannot be reloaded or reused. The mounting end is closed by a burst diaphragm and an orifice retaining plate. Threaded bosses are provided for two initiators which activate the solid propellant gas generator.
The engine start signal energizes both solid propellant gas generator initiators. As the solid propellant grains start to burn, the burst diaphragm ruptures (pressure is approximately 650 psi) releasing a gas flow rate of approximately 4.68 pounds per second; it will maintain this constant flowrate for approximately 1.0 second. These gases spin the turbine, which in turn drives the LOX and fuel pumps until fuel control pressure opens the liquid propellant gas generator control valve.
The liquid propellant gas generator begins to receive bootstrap propellants from the turbopump propellant discharge ducts as solid propellant grains are consumed. Ignition of liquid propellant gas generator propellants is accomplished by solid propellant grain, which burns approximately 100-200 milliseconds after LOX and fuel enter the combustor. Ignition of liquid propellants is ensured by the use of two auto-ignition igniters.
MAIN LOX VALVE CLOSING VALVE
Closing the main LOX valve and subsequent shutdown of the engine is accomplished by firing a single-body opposed, pyrotechnic-actuated, control valve (CONAX valve). This valve is designed so that actuation of either one or both trigger assemblies will allow fuel pump outlet pressure to flow through the valve body to the closing port of the main LOX valve. Each section of the valve is self-contained and pyrotechnic-actuated. Valve operation is two way and it is normally closed.
Upon receipt of an electrical signal for engine shutdown, the explosive charges within the valve igniter produce the mechanical force required to shear the metal membrane in the valve body, alIowing high-pressure control fuel to flow through and on to the closing control port of the main LOX valve. Normal shutdown will result with the operation of only one pyrotechnic actuator.
HYPERGOL CONTAINER
The unitized hypergol container is an integral part of the thrust chamber injector and includes a cylindrical housing to accommodate a six-cubic-inch hypergol cartridge and a hypergol-installed detector switch. A lockpin is provided to secure the cartridge or closure in the container.
GAS GENERATOR IGNITERS AND SOLID PROPELLANT GAS GENERATOR INITIATORS
Igniters and initiators are pyrotechnic devices used to initiate burning of the propellants in the liquid propellant gas generator and the solid propellant gas generator for engine starts.
Igniters
The gas generator auto-ignition igniter is a pyrotechnic device used to ensure ignition of the liquid propellant mixture in the gas generator combustion Two igniters are required on the gas generator.
Initiators
The solid propellant gas generator initiator is a pyrotechnic device used to initiate burning of the solid propellants in the solid propellant gas generator. Two initiators are used, each consisting of a two-pin electrical receptacle and a moisture sealed cartridge assembly housing a pyrotechnic material. An electrical impulse of 500 vac, 1.50 amperes minimum, is required to close the circuit through means of a spark gap. Closing of the circuit causes a nichrome wire to turn red hot, thus igniting the pyrotechnic "match-head mix" material. Maximum no-fire voltage is 250 vac.
SYSTEM CHECK VALVES AND COUPLINGS
The check valves on the engine are used to limit the flow of fluids to one direction. Quick-disconnect couplings are used on system fill ports and for system drains.
Propellant Feed System
The propellant feed system consists of the main fuel valve, main oxidizer ignition control valve (consisting of the main LOX valve and the igniter fuel valve), propellant high-pressure ducts, turbopump, check valves, and orifices. The purpose of the propellant feed system is to supply the propellants to the thrust chamber and gas generator.
MAIN LOX VALVE
The main LOX valve (MLV), which is used for controlling the flow of oxidizer to the thrust chamber, is installed between the thrust chamber inlet elbow and the high-pressure duct. The actuation cylinder on the main LOX valve is equipped with a blanket-type heater to prevent abnormal valve operation due to the low temperature of the oxidizer. An acceptable temperature range is 70 to 130 degrees F.
The valve actuation pressure, supplied by the fuel pump discharge, enters the opening port and applies force on the actuation piston. This pressure overcomes the spring pressure and moves the piston toward the open position. As the piston moves to the valve open position, the piston rod linked to a crank rotates the valve shaft and gate 90 degrees to the open position.
The main LOX valve is closed by firing a pyrotechnic-actuated main LOX valve closing control valve which permits fuel pressure to flow to the closing port of the main LOX valve. This equalizes fuel pressure on both sides of the actuation piston, allowing spring force and the difference in area ratios to actuate the valve to the closed position.
IGNITER FUEL VALVE
The igniter fuel valve (IFV) is attached to, and operated by, the main LOX valve. During engine start, the igniter fuel valve is used to sequence the flow of ignition fuel. The igniter fuel valve is actuated by a cam located on the main LOX valve gate shaft. During engine start; the igniter fuel valve leaves the closed position when the main LOX valve reaches 60 degrees of gate rotation and reaches the full-open position when main LOX valve is open 80 degrees.
The igniter fuel valve remains open, permitting fuel flow to the hypergol container and to the inlet port of the ignition monitor valve for main fuel valve actuation. During engine shutdown, as the main LOX valve starts to close, the igniter fuel valve closes, shutting off fuel flow to the thrust chamber igniter fuel spray disks and to the ignition monitor valve. The main fuel valve then closes by spring action and vents into the igniter fuel system.
MAIN FUEL VALVE
The main fuel valve (MFV) is used to control the flow of fuel to the engine and is located between the thrust chamber fuel inlet manifold and the high-pressure fuel duct. The main fuel valve is a butterfly-type with a balanced gate 4.25 inches in diameter and is nearly identical to the main LOX valve except for the difference in the closing control and the absence of the heater assembly and the cam for igniter fuel valve actuation.
When satisfactory ignition has been achieved, the pressure buildup sensed at the thrust chamber fuel injector manifold will open the ignition monitor valve which directs fuel actuation pressure to the opening port of the main fuel valve for valve actuation.
During engine shutdown, main fuel valve closing is accomplished by decreasing pressure allowing the main fuel valve to start closing and the ignition monitor valve to vent actuation pressure into the igniter fuel system. The main fuel valve closes under spring tension.
Turbopump
The turbopump is a turbine driven, dual-pumping unit consisting of an oxidizer pump, a fuel pump, a reduction gearbox, an accessory drive adapter, and a turbine. To simplify the engine system high-pressure plumbing, the turbopump is mounted on the side of the thrust chamber with the main shaft at right angles to the thrust vector. This mounting provides a high-pressure duct routing with minimum pressure drop, reducing the requirements for development of high pump-outlet pressures. The outlets of the oxidizer pump and the fuel pump are integral parts of the respective pump volutes. These outlets are attached to the main propellant ducting.
During engine operation, the turbopump supplies oxidizer and fuel to the thrust chamber at the required pressures and flowrates. The turbopump also supplies the liquid propellant gas generator with the required flow of oxidizer and fuel.
Design refinements incorporated in the latest configuration turbopump include increased volute strength, integral diffuser vanes, high-strength bolting arrangement, and tapered inducer vanes. The gearbox has increased rigidity through use of additional dowels and bolts in the area of the turbine mount. Wider gear teeth and higher purity of material of the intermediate gear and high speed pinion have been incorporated.
Integral accessory drive pads, internal lube passages for all bearings, and adjustable lube pressure by means of a fixed orifice are additional changes made to the gearbox. Turbine seal design is improved; and an electronic tachometer, which uses a single element magnetic pickup to sense turbine shaft speed by means of holes in the inner bearing spacers, is incorporated.
OXIDIZER AND FUEL PUMPS
The turbopump incorporates two single-entry, centrifugal propellant pumps mounted back to back, one on each side of the gearbox. The fuel pump is bolted to the gearbox, and the oxidizer pump is secured to the gearbox by radially inserted steel pins. The steel pins allow the oxidizer pump housing to expand and contract during the extreme temperature changes without distortion and misalignment. Both pumps are driven by a common shaft, and each pump has an axial-flow inducer, a radial-flow impeller, and diffuser vanes.
The oxidizer pump and the fuel pump pressurize the propellants for thrust chamber and gas generator combustion. The axial-flow inducers increase the pressure at the impeller inlet and allow a lower net positive suction head. Hollow- vaned, radial-flow pump impellers are used for pumping the propellants. The propellants pass from the inducers into the impeller inlets, through the impeller slinger vanes to stationary diffuser vanes on the pump adapter and into the pump volutes. The diffuser vanes give uniform distribution of pressure and reduction of fluid velocity around the impellers.
GEARCASE
The turhopump gearcase includes a series of full-depth reduction gears with integral hearing inner races; gear carrier and main shaft bearings; accessory drives; pump shaft hearing seals; and on the oxidizer pump shaft, a gearing heater. The drain manifold is designed for horizontal drainage and includes internal passages for fuel additive lubrication. The turbopump gearcase reduces the speed between the turbine and the pump shaft.
TURBINE
The turbopump turbine is an impluse-type, two-stage, pressure-compounded unit used to drive the turbopump. The turbine is bolted to the fuel pump housing and consists of an inlet manifold, first- and second-stage turbine wheels and nozzles, a turbine shaft, and a splined quill shaft connecting the turbine shaft to a high-speed pinion gear.
A calibrated, liquid propellant gas generator system controls the flow of hot gases which drive the turbine. The turbine inlet manifold distributes the gases to the first-stage turbine wheel. After passing through the first-stage turbine wheel, the gases increase in velocity by passing through the second nozzle and the second-stage turbine wheel. The gases then leave the turbine through the exhaust ducting. A seal, installed between the first and second- stage wheels, prevents the hot gas from bypassing the second-stage nozzle. Two-stage sealing also prevents high- temperature gases from heating the turbine shaft bearings.
Fuel Additive Blender Unit
A fuel additive blender unit is incorporated into the engine system to reduce weight by eliminating the oil tank, pressurizing equipment, plumbing, and controls which were required by previous lubrication systems. Extreme- pressure additive RBO140-006 (Rocketdyne) is injected into, and mixed with, RP-1 fuel from the fuel pump discharge. This mixture is introduced into the turbopump gearbox where it lubricates and cools the gearbox components.
ELECTRICAL SYSTEM
The engine electrical system consists of armored and unarmored electrical harnesses, switches, component heaters, and thrust-OK pressure switches. The thrust-OK pressure switch will commit launch automatically and signal that the engine has attained mainstage operation. In flight this system will provide a cutoff signal in the event thrust falls below a predetermined operating level. The electrical system will condition and check out the engine and control engine start, flight, and cutoff.
ENGINE OPERATION
Ignition Stage
When engine prefiring preparations are complete, the engine firing switch is manually actuated, sending an electrical signal to the solid propellant gas generator initiators, which ignite the solid propellant charge. Burning of the solid propellant accelerates the turbine, causing turbopump discharge pressures to increase against the closed propellant valves. Fuel pressure tapped off the fuel high-pressure duct by the series control line is directed to the igniter fuel valve inlet, fuel additive blender unit inlet, opening port of the main LOX valve, and the closing control manifold.
When fuel pump discharge pressure attains 70 to 110 psig, the fuel additive blender unit opens to permit lube flow to the turbopump bearings and gears. When fuel pump discharge pressure reaches 300 +/- 50 psig, the main LOX valve opens and the LOX dome, injector, LOX bootstrap, and heat exchanger supply lines start to prime.
The igniter fuel valve is opened by a cam on the main LOX valve gate shaft when the main LOX valve is opened. This directs fuel pressure to the hypergol container inlet and to the inlet port of the ignition monitor valve.
When fuel pressure at the hypergol inlet reaches approximately 300 psig, the hypergol cartridge burst diaphragms rupture and pyrophoric fluid, followed by ignition fuel flows through the thrust chamber injector igniter fuel spray housings and into the combustion area where it contacts the LOX, ignites, and burns, completing the ignition phase of engine starting.
Transition
If a satisfactory thrust chamber ignition has been achieved, a pressure increase in the thrust chamber fuel injector manifold will be sensed at the ignition monitor valve control port. Sufficient pressure at the control port will open the ignition monitor valve which allows fuel control pressure to open the main fuel valve.
Fuel, under turbopump pressure, flows through the open main fuel valve, to the fuel bootstrap line, through the thrust chamber fuel jacket, through the injector, and into the thrust chamber combustion zone where main propellant ignition is accomplished.
Increasing fuel pressure, resulting from main propellant ignition and sensed at the thrust chamber fuel injector manifold, opens the liquid propellant gas generator control valve. Bootstrap propellants enter the liquid propellant gas generator with a slight LOX lead and are ignited by hot gases from the solid propellant gas generator and the two auto-ignition igniters. The turbopump accelerates, the thrust builds up, and rated operation is attained.
Engine Cutoff
Engine shutdown is achieved by an electrical cutoff signal which fires a pyrotechnic-actuated valve to close the main LOX valve, cutting off LOX flow to the thrust chamber and gas generator. Closing the main LOX valve allows the igniter fuel valve to close, shutting off fuel pressure to the hypergol container inlet, ignition monitor valve inlet, and the main valve opening port. When the main fuel valve actuation pressure decays to approximately 200 psig, the main fuel valve closes under spring pressure, completing engine shutdown approximately 1 second after cutoff signal. A fuel-rich shutdown is provided to prevent a temperature spike in the liquid propellant gas generator. A natural fuel-rich shutdown occurs in the thrust chamber.
Copyright 1997-2005 by John
Duncan |
