RCS

RCS (reaction control system) uses small thrusters to rotate a vehicle and make translation corrections. Translation changes velocity without requiring the nose to point along the desired motion. Rotation changes pitch, roll or yaw. Both can use the same nozzles, so their maximum capabilities cannot simply be added together.

The installation and numerical limits below apply to the W-6 Manx, E-10 Saint and E-11 Saint. Other vehicles' drive systems and RCS installations have their own limits. Main-engine VTOL is separate from RCS.

Controls and directions

Directions are relative to the aircraft: forward is toward the bow, right is the aircraft's right side, and up is toward its roof. Exhaust points opposite the force on the aircraft. For example, firing a left-side jet pushes the aircraft right; an underside jet pushes it up. Turning the aircraft changes how these body directions relate to the horizon or a station.

The following are default keyboard bindings; use F1 to check the current bindings. The front/back and left/right jet names describe the firing side, not the direction the aircraft accelerates.

Default input	Request / effect
Home	Front/bow exhaust; backward translation, away from the bow.
End	Rear/aft exhaust; forward translation, toward the bow.
Numpad 7	Left-side exhaust; rightward translation.
Numpad 9	Right-side exhaust; leftward translation.
F9	Upward demand. The propulsion system uses available main-engine vertical thrust and bounded RCS assistance; this is not an RCS-only key.
F8	Downward RCS demand outside TVM's ground-reference BCL descent mode. In that TVM mode it commands the descent schedule instead.
Shift+A	Toggle thrust augmentation, which assists attitude/rate control within available authority.
K / J	Toggle TVM / DOR respectively; these modes change who commands translation and attitude.

Use the normal pitch, roll and yaw controls to request rotation. Releasing a translation key removes the manual request; it does not by itself cancel the velocity already acquired. Leave time and distance for braking, especially with a heavy aircraft or when the same jets are correcting attitude.

TVM and DOR

TVM combines velocity-matching requests with the available main engines and RCS. With a ground reference in BCL, F8 requests DES, key release requests HOVER, and F9 requests maximum upward thrust / CLIMB. Hover requests do not establish an unlimited lift capability or select a fixed desired altitude. See TVM vertical landings for the descent schedule and mode conditions.

While DOR is engaged, manual translation-RCS keys are inhibited. This does not mean all RCS is disabled: DOR can use attitude jets and small automatic corrections. In a normal orbital WAIT/COAST with released attitude axes, the pilot can turn to look around without cancelling the route. During ALIGN or active powered guidance, manual attitude input takes over and disconnects DOR. Read the FMA and Orbit page; blank attitude cells caused by invalid guidance or Flight Freeze are not permission to assume normal free-coast operation. Disengage DOR to take over translation manually.

Installed nozzles and ratings

Each of the three aircraft has 16 physical RCS nozzles, arranged as 14 directional groups controlled through seven signed channels. One sign selects one direction; the opposite sign selects the opposing outlet. Opposite directions of a single channel do not fire together.

Channel group	Channels	Physical nozzles	Healthy rated output in either selected direction
Front-left, front-right, rear-left and rear-right vertical pairs	4	8: one upper and one lower at each station	80 kN per nozzle, per station
Front and rear lateral pairs	2	4: one left and one right at each station	80 kN per nozzle, per station
Fore/aft translation	1	4: two bow-facing and two aft-facing nozzles	160 kN per firing pair; 80 kN at each nozzle

80 kN means 80,000 newtons of force from one fully delivering nozzle. It is not an acceleration, a whole-vehicle rating, or the amount available independently to every control axis. Power, equipment condition, wear and competing commands reduce available or delivered output. The RCS model uses the same nominal nozzle force in atmosphere and vacuum; main-engine atmospheric performance is separate.

Handling and shared limits

The normal angular-acceleration command ceilings are:

Axis	Command ceiling
Pitch	6°/s²
Roll	8°/s²
Yaw	6°/s²

Degrees per second squared describes how quickly rotation rate changes, not the rotation rate itself. These ceilings do not guarantee that the installed jets can achieve them at every weight. A heavier aircraft has more rotational inertia, nozzle distance from the CG determines leverage, and simultaneous translation or trim uses part of the same capacity. Aerodynamic forces and external disturbances can also produce acceleration beyond a normal command ceiling.

With healthy equipment at maximum gross weight and no competing demands, the E-10 and E-11 have approximately 2.33°/s² and 1.98°/s² of pure RCS yaw authority respectively, below the 6°/s² ceiling. These are isolated axis references, not simultaneous maneuver guarantees.

Net vertical RCS translation is limited to approximately 52.50 kN for the W-6 and 119.09 kN for each E-series aircraft before availability reductions. Each is about 0.5 m/s² at its aircraft's maximum gross mass, before gravity and other forces. Lower mass increases acceleration. Zero-net-force attitude couples can use opposing jets without adding net lift. RCS does not replace the main lift needed to hover.

E-series main-thrust trim

At the nominal model CG, the E-10 and E-11 each have about 3.42 MN·m of pure pitch-RCS torque with zero net translation. Full forward vacuum main thrust produces approximately 4.84 MN·m on the E-10 and 5.49 MN·m on the E-11. Consequently, full axial output cannot be assumed trimmable by RCS alone in vacuum. The trim allocator can reduce delivered main thrust to respect available control moment. The aft main engine remains fixed axially; augmentation does not make it vector.

EICAS, plumes and fuel

EICAS RCS indications and the W-6 RCS indications show delivered nozzle output, not simply the pilot's requested input.

• 100% uses a common 80 kN-per-nozzle scale on all three aircraft. The two arrows in a fore/aft pair repeat the same per-nozzle fraction; their combined force is twice the per-nozzle value.
• Cyan arrows indicate the emitting side and exhaust direction. A cyan + in a circle means body-up force; − means body-down force. Ring fill shows output on the common scale.
• At or below 2% (1.6 kN per nozzle), the outlines remain gray and the circles have no + or −. Small physical stabilizing corrections can still occur below this display threshold.
• RCS plume extension follows the same delivered-force fraction. Main-engine bars and plumes have their own rating scale.
• Opposing jets can cancel net translation while still producing torque, visible exhaust, sound and fuel consumption. A stationary aircraft can therefore be using RCS. Fuel consumption follows emitted output, not just the remaining net force.

Atmosphere, space and VTOL

RCS is useful on the ground, in hover, atmospheric flight, ascent, suborbital coast, orbit and re-entry, subject to power, fuel, equipment condition, docking/containment and control-mode ownership. There is no separate RCS altitude or vacuum cutoff for these installations. Aerodynamic forces still affect the aircraft in air.

With thrust augmentation enabled, ordinary AFCS on the W-6, E-10 and E-11 gives the available aerodynamic control surfaces priority. RCS supplies the remaining turning or trim demand when the surfaces cannot provide it. Jets can also assist while a surface is moving to its required position. This depends on actual airflow, surface condition and control travel, not a single airspeed or altitude cutoff. Weak airflow, stalled or damaged surfaces, and simultaneous translation can therefore still require substantial RCS. Manual augmentation, TVM and DOR retain their own control modes.

The W-6's 4,000/3,200 Pa dynamic-pressure interlock protects its main-engine lift doors; it is not an RCS door restriction. When those outlets are inhibited, vertical translation relies on the much smaller RCS capability. The E-10/E-11 use their tilting wing-engine outlets for main vertical thrust. See VTOL operating limits for sequencing and the distinction between main thrust and RCS.

In orbit, holding F9 can build body-up velocity using the mains much faster than body-down RCS can remove it. Do not assume equal upward and downward braking capability near a station. A reference to nominal thrust or command limits does not establish a safe departure, hover weight, docking approach or re-entry trajectory.

See also

• EICAS
• TVM
• VTOL
• Orbit and Autoflyte
• W-6 Manx, E-10 Saint and E-11 Saint