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1. Space ShuttleReaction Control System Kavan Eldredge
21 October 2004
2. RCS Overview The Space Shuttle Reaction Control System (RCS) is the primary flight control system at altitudes above 70,000 feet.
3. System Components and Capabilities RCS thrusters are located in the forward RCS module in the orbiter nose section and in each of the 2 Orbital Maneuvering System (OMS) pods in the orbiter tail section
4. System Components and Capabilities Monomethyl hydrazine used as fuel, nitrogen tetroxide used as oxidizer
Each thruster combustion chamber made of columbium with columbium-disilicide coating
Thruster nozzles cooled by radiation; insulation protects orbiter structure from up to 2400 °F
Each thruster is fired by 2 solenoid-operated poppet valves, one each for fuel and oxidizer
5. RCS Primary Thrusters Total of 38 primary thrusters
14 located in forward RCS, 12 in each OMS pod
Performance capabilities per thruster:
870 lb vacuum thrust using oxidizer to fuel ratio 1.6:1
100-mission min. service life with 20,000 starts and 12,800 sec. total firing time
150-sec. max. single continuous burn
Enough primary thrusters to allow for redundancy
6. Vernier Thrusters Used for finite maneuvers and long-term attitude hold
Total of 6 vernier thrusters
2 located in forward RCS, 2 in each OMS pod
Performance capabilities per thruster:
24 lb vacuum thrust using oxidizer to fuel ratio 1.6:1
Service life of 330,000 starts, 125,000 sec. total firing time
125 sec. max. single continuous burn
Vernier thrusters not redundant
7. Fuel and Oxidizer Systems Each RCS module has a separate, self-contained fuel, oxidizer, and helium system
Each module has one fuel tank and one oxidizer tank
Each spherical, titanium tank has a 39 in. diameter
Forward tanks each weigh 70.4 lb empty
Aft tanks each weigh 77 lb empty due to additional components needed for operation at 2.5 g re-entry acceleration
Typical full load is 1464 lb per oxidizer tank and 923 lb per fuel tank
Heaters used to maintain propellant operating temperatures
8. Helium Pressurization System Helium system pressurizes fuel and oxidizer tanks
Each module has two 18.71 in. diameter spherical helium tanks
Each tank is made of titanium-lined Kevlar and weighs 24 lb empty
Pressurization is controlled by a valve system including redundant pressure regulators
10. Operations and Operating Procedures, Launch to On-orbit Used to maintain attitude during External Tank separation and to translate orbiter away from ET
Used for attitude hold between OMS burns of a 2-burn orbital insertion, can also be used to supplement OMS-gimbaling for attitude hold during OMS burns if necessary
Used for attitude hold and orbital maneuvers
RCS controlled by Translational/Rotational Hand Controllers and Digital Autopilot
11. Operations and Operating Procedures, De-orbit and Re-entry Places orbiter in tail-first orientation prior to re-entry
Used to attain entry interface attitude after OMS de-orbit burn
Front RCS deactivated at 400,000 ft, aft RCS used for attitude hold
RCS roll thrusters deactivated at dynamic pressure = 10 psf
Pitch thrusters deactivated at dynamic pressure = 20 psf
Yaw thrusters deactivated at about Mach 1 and 45,000 ft
12. Modifications Addition of sniff line in RCS valves to monitor and restrict fuel and oxidizer during ground operations
Injector solenoid valve wiring wrapped around combustion chambers to remove power from valves in case of primary RCS thruster instability; in such a case, thruster would be deactivated for remainder of mission
13. Questions?