Thrust Chamber Body

The thrust chamber body provides a combustion chamber for burning propellants under pressure and an expansion nozzle for expelling gases produced by the burned propellants at the high velocity re­quired to produce the desired thrust. The thrust chamber is tubular-walled and regeneratively fuel – cooled, and the nozzle is bell-shaped. There are four sets of outrigger struts attached to the exterior of the thrust chamber; two sets of the struts are turbo­pump mounts and the other two are attach points for the vehicle contractor’s gimbal actuators. The thrust chamber incorporates a turbine exhaust manifold at the nozzle exit and a fuel inlet manifold at the injector end which directs fuel to the fuel down tubes. Brackets and’studs welded to the re­inforcing “hatbands” surrounding the thrust cham­ber provide attach points for thermal insulation blankets.

Fuel enters the fuel inlet manifold through two diametrically opposed inlets. From the manifold, 70 per cent of the fuel is diverted through 89 alter­nate CRES “down” tubes the length of the chamber. A manifold at the nozzle exit returns the fuel to the injector through the remaining 89 return tubes. The fuel flowing through the chamber tubes pro­vides regenerative cooling of the chamber walls during engine operation. The thrust chamber tubes are bifurcated; that is, they are comprised of a primary tube from the fuel manifold to the 3:1 ex­pansion ratio area. At that point, two secondary tubes are spliced into each primary tube. This is necessary to maintain a desired cross-sectional area in each of the tubes through the large-diameter belled nozzle section.

The turbine exhaust manifold, which is fabricated from preformed sheet metal shells and which forms a torus around the aft end of the thrust chamber body, receives turbine exhaust gases from the heat
exchanger. Upon entering the manifold, the gases are distributed uniformly. As the gases are expelled from the manifold, flow vanes in the exit slots pro­vide uniform static pressure distribution in the nozzle extension. Radial expansion joints compen­sate for thermal growth of the manifold.

Thrust Chamber Nozzle Extension

The thrust chamber nozzle extension increases the expansion ratio of the thrust chamber from 10:1 to 16:1. It is a detachable unit that is bolted to the exit end ring of the thrust chamber. The interior of the nozzle extension is protected from the engine ex­haust gas environment 15800 Fahrenheit) by film cooling, using the turbine exhaust gases (1200 Fahrenheit) as the coolant. The gases enter the extension between a continuous outer wall and a shingled inner wall, pass out through injection slots between the shingles, and flow over the sur­faces of the shingles forming a boundary layer lie – tween the inner wall of the nozzle extension and the hotter exhaust gases exiting from the main en­gine combustion chamber. The nozzle extension is made of high strength stainless steel.

Hypergol Cartridge

The hypergol cartridge supplies the fluid to produce initial combustion in the thrust chamber. The car­tridge, which is cylindrical and has a burst diaphragm welded to either end, contains a hypergolic fluid consisting of 85 per cent triethylborane and 15 per cent triethylaluminum. As long as the fluid is in the hermetically sealed cartridge, it is stable, but it will ignite spontaneously upon contact with oxygen in any form. During the start phase of operation, increasing fuel pressure in the igniter fuel system ruptures the hurst diaphragms. The hypergolic fluid and the fuel enter the thrust cham­ber through a segregated igniter fuel system in the injector and contact the oxidizer. Spontaneous com­bustion occurs and thrust chamber ignition is estab­lished.

Pyrotechnic Igniter

Pyrotechnic igniters, actuated by an electric spark, provide the ignition source for the propellants in the gas generator and re-ignite the fuel-rich tur­bine exhaust gases as they exit from the nozzle ex­tension.

Thermal Insulation

The thermal insulation protects the F-l engine

SATURN V NEWS REFERENCE

from the extreme temperature environment (2550 Fahrenheit maximum) created by radiation from the exhaust plume and backflow during clustered- engine flight operation. Two types of thermal in­sulators are used on the engine—foil-batt on com­plex surfaces and asbestos blankets on large, simple surfaces. They are made of lightweight material and are equipped with various mounting provi­sions, such as grommeted holes, clamps, threaded studs, and safetywire lacing studs.