6. The Launch Vehicle

With the retirement of the Saturn launch vehicle It is launched from the U.S. Air Force Eastern Test system following the Apollo-Soyuz mission in sum- Range at Cape Kennedy Air Force Station, Com- mer 1975, the Titan III E Centaur is the United plex 41. State’s most powerful launch vehicle (Figure 6-1). It became operational in February, 1974.

FUNCTION

The function of the Titan III E Centaur launch vehicle is to lift the total Viking spacecraft into Earth orbit, then boost it into a trajectory that will take it to Mars. The three Titan stages and an initial burn of the Centaur upper stage place the spacecraft in a 90 nautical mile high parking orbit around Earth. Then, at the proper moment between six and 30 minutes later, the Centaur fires again to push the spacecraft on the proper course to Mars.

VEHICLE

The two Titan III E Centaur vehicles (Figure 6-2) that launch the Vikings on their trip to Mars, are a combination of the Titan III E booster and the Cen- taur D-1T upper stage. This is a new combination of two systems that have been used extensively in other combinations. This vehicle is well suited for high performance deep space missions, and for placing large space- craft in synchronous orbit. The most visible change to the standard Titan III appearance is the enlarged payload shroud neces- sary because the diameter of the Centaur with its shroud is greater than the diameter of the Titan main core.

The Titan III E consists of the O-stage, which is two solid rocket motors strapped to the center core, and liquid propelled stages one and two which make up the center core. The Centaur is the fourth stage.

The Titan family of launch vehicles began with the Titan I, Air Force and includes the Titan II, the Titan Gemini launch vehicle, Titan IIIB, IIIC, IIID and now the IIIE.

Figure 6-1 Titan Centaur Launch Vehicle The Titan III E Centaur is 159 feet tall.

Ill-73 Stage 0

Contractor: United Technologies Corporation Chemicals Systems Division Sunnyvale, California

Initial thrust for the Titan IIIE at liftoff is pro- vided by two identical, segmented solid propellant rocket motors.

These 10 foot diameter motors are mounted 180 degrees apart on the liquid propellant core vehicle. They are 85 feet tall with the nose fairing, and each weighs more than 500,000 pounds. Together they produce 2.4 million pounds of thrust and burn for 122 seconds. The solid rocket motor propellant case is con- structed of heat-treated steel with a strength of 195,000 pounds per square inch. The motors burn solid propellant which contains powdered aluminum as fuel and ammonium chlorate as the oxidizer. The propellant also con- tains polybutadiene acrylic acid acrylonitrile as a binding agent. The solid rocket motors are steered by a liquid injection thrust vector control system mounted vertically alongside each engine. This system is capable of changing the vector angle of the thrust by 5 degrees using a maximum side force of 110,000 pounds on each motor. The system injects nitrogen tetroxide pressure fed into the engine noz- zle by nitrogen gas. The thrust vector control sys- tem tanks are 22 feet long, 3.5 feet in diameter and carry 8424 pounds of nitrous oxide and 636 pounds of nitrogen each.

Stage 1

t or: Martin Marietta Aerospace Denver, Colorado

The firs stage of the liquid propellant core vehicle ignites about 112 seconds after liftoff. About 12 seconds later, the solid rocket motors are jetti- soned over the Atlantic Ocean.

Thrust for this stage is provided by a single Aerojet General liquid rocket engine. The single engine is technically two engines attached to a single frame and operates simultaneously from a single control Figure 6-2 Titan IllE Centaur Cutaway View system.

III-74 The engine is hydraulically balanced and requires control is provided by turbine exhaust no thrust controls. Pitch and yaw control are pro- through a swiveled roll control nozzle adjacent to vided by pivoting the thrust chambers indepen- the engine. The hydraulic cylinders that control dently on their gimbal mounts. A gas generator the direction of the engine thrust receive their con- mounted near the engine provides roll control. The trol signals from the launch vehicle flight control hydraulic cylinders that control the direction of system. the engine thrust receive their control signals from the launch vehicle flight controls system. The second stage propellant is a mixture of equal parts of hydrazine and unsymmetrical The first stage propellant is a mixture of equal hydrazine as fuel, and nitrogen tetroxide as oxi- parts of hydrazine and unsymmetrical dizer, the same as Stage I. hydrazine as fuel, and nitrogen tetroxide as oxidizer. The second stage is 10 feet in diameter and 23 feet tall. Fueled, it weighs 73,000 pounds, provides These propellants ignite spontaneously 101,000 pounds of thrust and burns for 210 sec- on contact, eliminating the need for an ignition onds. system and related checkout and support equip- ment. Before launch, Stage I and II tank pressuriza- tion is provided by ground-supplied pressurized nitrogen. During flight, pressurization is supplied Centaur D-1T by gas generators in the rocket engine system. Contractor: General Dynamics, Convair Division The first stage is 10 feet in diameter and 63 feet San Diego, California tall. Fueled, it weighs 273,000 pounds, it provides more than 520,000 pounds of thrust and burns for The Centaur (Figure 6-3) begins its first burn about 146 seconds. eight minutes after liftoff to provide the final thrust to put the Viking spacecraft into a parking The core vehicle structure (Stages I and I is a orbit. This first burn occurs 10.5 seconds after frame-stabilized, aluminum skin that provides Stage II separation. structural strength by using stringers and frames attached to the inner surface. The Centaur D-1T is a high energy upper stage which includes major improvements in its guidance An ablative-coated heat shield assembly protects and payload systems over earlier versions. Earlier the Stage I engine from the high temperatures gen- versions of the Centaur in various configurations erated by the solid rocket motors. The heat shield have been launched with the Atlas launch vehicle. encloses the engine from the thrust chamber up- wards. The Centaur is 31.5 feet tall and 10 feet in diam- eter, excluding the shroud which protects it atop Stage II the launch vehicle.

Contractor: Martin Marietta Aerospace The Centaur shroud (Figure 6-4) is 58 feet tall and Denver, Colorado 14 feet in diameter, 4 feet in diameter larger than the liquid propellant core of the Titan III on which Stage II of the liquid propellant core ignites about it rests. Shortly after Stage II ignition, a signal 4.3 minutes after liftoff when the Stage I propel- from the guidance system severs and jettisons the lant is exhausted. About one second later Stage I shroud exposing the Centaur. separates from Stage II. The Centaur weighs 35,000 pounds including pro- Thrust for this stage is provided by an Aerojet Gen- pellants. It burns cryogenic fuels, liquid oxygen eral engine similar in construction and operation to and liquid hydrogen. The propellants are delivered a single engine in Stage I. to the two Pratt and Whitney engines by boost pumps that are driven by turbines fueled by hydro- Pitch and yaw steering control are provided by gen peroxide. Engine thrust is 30,000 pounds (in pivoting the engine on its gimbal mounting. Roll vacuum).

III-75 Centaur Shroud

Viking Lander

Viking Orbiter

Equipment Modu

Tank

Tank

Boost Pump

Helium Bottles

Main Engines

Figure 6-4 Centaur Shroud Cutaway with Viking Figure 6-3 Cen taut- D- 7 T Upper Stage Spacecraft Atop Centaur

III-76 The Centaur has two identical and separate platform rotates from the inertial reference, the power systems that steer the two main engines. gyros sense the error and send a signal which moves They receive their control signals from the guid- the platform back to its proper orientation. ance and control system. Rate data is provided to the flight computer by During coast, separation and retro-firing, the atti- three accelerometers mounted on the platform. tude of the Centaur is maintained by small engines, They continuously monitor velocity of the vehicle each with 6 pounds thrust, mounted on the bot- and send signals to the computer for its flight up- tom of the vehicle. They are hydrogen peroxide date information. fueled. Telemetry-The function of the instrumentation Guidance and Control-The purpose of the guid- and telemetry system is to collect, digitize and ance and control system is to determine the ve- send measurement signals to the ground from the hicle’s correct position and velocity, and send the launch vehicle during countdown and during flight. appropriate signals to correct navigational errors. Capability is 1536 individually addressed measure- ments. The entire system includes a Teledyne Ryan digital computer with a 16,384 word random access The system transmits PCM digital information over ory, a Honeywell inertial reference unit and elec- the S band to the ground station network operated tronics required to support the system. by the Eastern Test Range, that includes ground stations, ships and aircraft. The system is mounted in an equipment area atop the Centaur, and provides navigation and control In addition to the PCM system, an AM/FM system for the entire Titan IIIE Centaur launch vehicle. is installed on the Centaur stage to transmit analog data from the Viking spacecraft. Computer-The digital computer plays a role in several functions: navigation, guidance, control, propellant control and pressurization, in- Range Safety-Titan IIIE Centaur range safety is strumentation and telemetry. provided by two subsystems. One of those is a self-contained receiving system which can receive a The computer receives and processes data from the command signal from the range safety officer to launch vehicle according to a prestored program, shut down the engines and destroy the vehicle. and sends the proper commands to control the ve- hicle. The second subsystem is independent of ground control. It is a wired circuit that senses any vehicle Inertial Reference Unit-The Centaur inertial refer- breakup that would prevent reception of a destruct ence unit contains a four gimbal, three axis stable signal from the ground, and sends the proper platform that is stabilized by three gyros. If the destruct signal to the vehicle.

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