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→The OMS engines
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The OMS engines are located at the rear of the spacecraft in pods attached to the fuselage. Two of the RCS clusters are attached to the OMS pods, one is located at the spacecraft nose. | The OMS engines are located at the rear of the spacecraft in pods attached to the fuselage. Two of the RCS clusters are attached to the OMS pods, one is located at the spacecraft nose. | ||
=== The | === The Orbital Maneuvering System engines === | ||
The two OMS engines provide a thrust of 6,000 lb and, using the propellant reserves of 7,773 lb of nitrogen tetrozide and 4,718 lb of MMH can induce a total velocity change of about 1000 ft/sec if all propellant is spent. Typically half of this is used to push the OV into a proper orbit after ET separation and for the de-orbit burn, the rest is available for orbital maneuvers such as inclination adjustments. | The two OMS engines provide a thrust of 6,000 lb and, using the propellant reserves of 7,773 lb of nitrogen tetrozide and 4,718 lb of MMH can induce a total velocity change of about 1000 ft/sec if all propellant is spent. Typically half of this is used to push the OV into a proper orbit after ET separation and for the de-orbit burn, the rest is available for orbital maneuvers such as inclination adjustments. | ||
Once in orbit, in FG throttle control is transferred to both OMS engines. They can be throttled from zero to 100% of nominal thrust and are automatically vectored by the flight controls through the CoG of the orbiter. The real shuttle has a DAP for thrust vectoring of the OMS engines as well as the option of using a single engine with partial thrust vectoring, neither option is currently modeled. | |||
=== The Reaction Control System === | |||
The RCS system consists of three modules, one forward at the nose and two at the OMS pods. The forward module contains 14 primary and 2 secondary thrusters, each aft module carries 12 primary and two secondary thrusters. Propellant reserves in each module are 1,477 lb of oxidizer and 928 lb of MMH. Each primary thruster has 870 lb of thrust with an ISP of 289 s, the secondary vernier thrusters produce a mere 24 lb each with an ISP of 228 s. Due to geometric constraints, the thrusters are not aligned with the main spacecraft axes or in the same plane (for instance, there is no purely downward firing nose thruster, as its nozzle would have to fire through the heat shield). | |||
As of May 2015, this assembly has been simplified in FG as follows: Thrusters are located at their correct position (nose and aft pods), resulting in approximately correct yaw, pitch and roll moments when fired. Each basic direction in which a thruster can fire from a module is modeled as a single effective thruster (for instance, no thruster can fire backward through the shuttle from the nose module, pod thrusters can't fire towards each other) with the combined thrust of all real thrusters at the module into that direction, resulting in a total of 13 individually controlled RCS thrusters and RCS-generated control moments very close to the real assembly. | |||
== Glossary of acronyms == | == Glossary of acronyms == | ||