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Jul 10, 2012

LEM RCS, Lunar Module Reaction Control Subsystem (Part 7, Apollo Control Systems)

The Reaction Control Subsystem (RCS) consisted of 4 clusters of thrusters (16 all together), fuel feeding system and its control electronics and computers.

Lunar Module (LM) Reaction Control Subsystem (RCS) Thrust Chamber Assembly Clusters (4)

You might also include the left TTCA (Thrust / Translation Controller Assembly) and the right ACA (Attitude Controller Assembly) hand controllers to that subsystem.

LM Attitude Controller Assembly ACA

LM Thrust / Translation Controller Assembly TTCA

Most RCS components were doubled

More detailed schematic of the RCS control section

The thrusters were more or less directly controllable by the joysticks but they were also fully computer controllable by both onboard computers (the MIT LGC and the TRW AGS). There were many automatic and semiautomatic computer flight modes which needed more or less pilot interference.

Engine cluster assembly

Single thruster

RCS thruster cutt-away

Maybe later thruster cutt-away

Thruster heater (see above cutt-away)

All RCS thrusters were ON/OFF type. The amount of impulse was controlled by the duration of the impulse since the amount of thrust could not be controlled. As soon as the fuels were pressurized by helium the full amount of flow was used to create thrust. Fuels were so designed that they ignited as soon as they were mixed.

"The RCS thrusters are radiation-cooled pressure-fed, bipropellant rocket engines that operate in a pulse mode to generate short thrust impulses for fine attitude corrections or in a steady-state mode to produce continuous thrust for major attitude or translation changes. In the pulse mode, the thrusters are fired intermittently in bursts of less than 1-second duration - the minimum pulse may be as short as 14 milliseconds - however, the thrust level does not build up to the full 100 pounds that each thruster can produce. In the steady-state mode, the thrusters are fired continuously (longer than 1 second) to produce a stabilized 100 pounds of thrust until the shutoff command is received." /1/

Various Thruster Test Videos

Some additional photos.


/1/ Grumman - LMA790-2 - Lunar Module Vehicle Familiarization Manual - LM 10-14

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