ORBITER ENVIRONMENTAL CONTROL & LIFE SUPPORT (ECLSS.)

Oxygen storage.-A vehicle fuel cell oxygen storage system has been selected for providing the primary oxygen requirements.

Pressure and composition control.-A pressure-regulated nitrogen and oxygen two-gas control is being designed for maintaining the proper pressure and atmospheric composition in the cabin.

Atmosphere controls.-Carbon dioxide, humidity and temperature controls will be required to assure good performance during all mission phases, including reentry and atmospheric flight. Heat exchangers and water separators will be required for the cabin temperature and humidity control functions.

Atmospheric contaminant control.-Conventional methods using charcoal, metallic adsorbents, particle and bacteria filters will be used.

Heat rejection.-Space radiator panels required for avionics cooling (see figure 141) will also be used as the main heat sink for the crew and passenger compartments during the on-orbit mission phase. An evaporator with either water or ammonia will be used for transient periods of high heat load, to supplement the radiator heat sink. Thermal control (air conditioning) consists of two coolant loops a nontoxic (water) circuit inside the cabin and a coolant circuit external to the cabin.

Water management.-Bladderless tanks will be used for potable water storage for increased reliability and to greatly reduce maintenance problems. Pasteurization and/or sterilization will be used to control microbiological problems.

Waste management.-The waste management system will be designed to accommodate both male and female crew members. It will employ vacuum drying components, which make it unnecessary to jettison waste products.

SPACE SHUTTLE MAIN ENGINE (SSME)

The Space Shuttle orbiter vehicle will be boosted into low Earth orbit by the Space Shuttle main engine (SSME) operating in parallel with twin solid rocket boosters (SRB). Simultaneous operation of the two solid propellant booster rockets and the three high pressure liquid oxygen/liquid hydrogen Orbiter main engines will provide the thrust necessary to insert the Orbiter into the desired ellipical Earth orbit. Main engines continue to burn until the desired orbit is achieved.

The main engines are located in the Orbiter aft fuselage in a triangular pattern (figure 142). The engine spacing allows adequate clearance for maximum gimbal deflection for thrust vector control during the launch phase.

The engines, which operate at a rated thrust level of 2 million newtons (470,000 lbs.), are designed to use a staged combustion cycle in which propellants entering the engine are raised to high pressure by turbopumps powered by preburners. The exhaust from the preburners is supplemented by the fuel used for cooling the engine and additional oxidizier; this mixture is then burned in the main combustion chamber and flows through the nozzle with an expansion ratio of 80: 1 (figure 143) (see p. 420).

Design and development of the SSME has been underway at Rocketdyne, a division of Rockwell International, since spring 1972.

This contract provides for delivery of 3 propulsion test engines and 24 flight engines. During the D.D.T. & E. phase of the Orbiter, seven engines will be delivered, the first three of which are scheduled for installation in the orbiter to be used in the first manned orbital flight in calendar year 1978 (figure 144) (see p. 420). The critical design review (CDR) scheduled for calendar year 1976 will insure that design has progressed sufficiently to permit release of engine drawings to manufacturing. Flight engines will be approved for manned flight prior to first manned orbital flight (FMOF) by means of flight certification reviews. This will insure that deliverable engines conform to contract end item specifications.

Fiscal year 1973 effort was devoted primarily to engine design and the start of component tests. The overall engine preliminary design review (PDR) was held in September 1972. Specific fiscal year 1973 tasks included: release of component and subsystem design drawings for major test items; preparation of design drawings for fabrication of hydraulic servoactuator mechanisms; laboratory and bench tests involving the preburner oxidizer system, oxidizer turbomachinery, thrust chamber, hot gas manifold, heat exchanger, and interconnect devices; and start of fabrication of components and subsystems for test programs including the ignition system, preburners, injection system, combustion chamber and nozzle assembly, oxidizer turbopump, fuel turbopump, and controller assembly.

Engine components developed by the engine contractor, as for example the hydrogen mixer hardware, are currently being tested. The liquid hydrogen used to cool the nozzle of the SSME is mixed through this hardware with the liquid hydrogen that bypasses the cooling circuit before entering the preburner injector. Those tests are designed to evaluate the mixer performance and operating characteristics. Other tests are used to determine the effectiveness of liquid hydrogen in cooling the combustion chamber. Temperature rise is measured along the chamber walls having contours similar to the SSME combustion chamber (figure 145).

Ignition system tests are being conducted to evaluate preburner performance and the effect of the design and fabrication process on the flow characteristics (figure 146) (see p. 422).

Two major subcontracts were awarded in FY 1973 by Rocketdyne, one to Minneapolis-Honeywell, Inc. of Minneapolis, Minnesota, for the controller and the other to Hydraulic Research Inc., of Los Angeles, California for the hydraulic actuator and filter assembly.

FY 1974 funding will provide for the continuation of engine design and test activities now underway and the initiation of others. Specific areas of effort will include: installation and checkout of component and subsystem test equipment; assembly and delivery of components and subsystems, including the liquid oxygen/ liquid hydrogen turbines, inducers, ignition system, bearings, preburner assembly, combustion chamber and nozzle assembly, fuel turbopump, and the controller assembly; ignition system tests; initiation of preburner, turbopump, and thrust chamber subsystems testing; release of engine assembly drawings procurement of long-lead hardware for deliverable test engines; start of fabrication of the engine controller subsystem and hydraulic servoactuator mechanism; start of fabrication of the engine test units for the first hot firing in early CY 1975; design and procurement of servoactuators to support engine contractor testing at the Mississippi Test Facility; and the construction and operation of the engine avionics breadboard. The first test engine will be delivered to the Mississippi Test Facility in preparation for the first engine test firing in 1975.

Other development tasks will be directed toward extending engine life and reusability. Additionally, fiscal year 1974 funding will provide for propellants to support development and component testing.