THIRD STAGE

STAGE DESCRIPTION

Basically, the Saturn V third stage, the S-IVB, is an aluminum air-frame structure powered by a single, J-2 engine, which burns liquid oxygen and liquid hydrogen. The engine has a maximum thrust of 225.000 pounds. The structure has a bipropellant capacity of 228,000 pounds of fuel and oxidizer.

STAGE FABRICATION AND ASSEMBLY

The third stage structure consists of a forward skirt assembly, propellant tank assembly, thrust structure assembly, aft skirt assembly, and aft in­terstage assembly. The propellant tank assembly consists of a single tank separated by a common bulkhead into a fuel compartment and an oxidizer compartment.

Forward Skirt Assembly

The forward skirt is a cylindrical aluminum skin and stringer structure that provides a hard attach point for the instrument unit. In addition, the for­
ward skirt provides an interior mounting structure for electrical and electronic equipment that requires environmental conditioning, as well as range safety and telemetry antennas mounted around the ex­terior periphery. Environmental conditioning for electronic equipment is provided by cold plates which utilize a coolant supplied from the IU thermo­conditioning system.

Propellant Tank Assembly

Structural elements of the propellant tank assembly are a cylindrical tank section, common bulkhead, aft dome, and forward dome. Seven segments are machined from aluminum alloy plate to form the tank section. A waffle pattern is then machine – milled into each segment to reduce weight and pro­vide shell stiffness. The formed segments are joined into a complete cylinder by single-pass internal weld on a Pandjiris welding machine.

Aft and forward domes are made by forming "orange peel” segments on a stretch press. Orange peel segments are then joined in a dome welder. Each

DAC161S3

Third Stage Production Sequence

6-і

D-NRV-40

Slosh Baffle…. Horizontal rings are installed inside LH2 tank for

propellant stabilization during flight.

D-NRV-42

Third stage vehicles reach end of assembly sequence with final assembly and checkout in 115-foot vertical towers.

Engine I nstalled—J-2 engine is attached to stage in final assembly tower at Huntington Beach.

Final installation of various subsystem components is performed in a checkout tower, along with the installation and alignment of the,1-2 engine. The stage is in a vertical position in the tower where a complete stage checkout of subsystems and systems is conducted except for actual ignition of engine. After satisfactory checkout, the stage is removed from the tower, placed on a dolly, and ground sup­port rings are installed at each end of the stage. It is then painted, weighed, and prepared for ship­ment to the Douglas Sacramento Test Center for simulated and static firing of APS engines and J-2 engine.