Editing Thrust vectoring (section)

=== Rockets and ballistic missiles ===
[[File:En Gimbaled thrust diagram.svg|thumb|[[torque|Moments]] generated by different thrust gimbal angles]]
[[File:Gimbaled thrust animation.gif|thumb|Animation of the motion of a rocket as the thrust is vectored by actuating the nozzle]]Nominally, the [[line of action]] of the thrust vector of a [[rocket nozzle]] passes through the vehicle's [[centre of mass]], generating zero net [[torque]] about the mass centre. It is possible to generate [[Aircraft principal axes#Principal axes|pitch and yaw]] moments by deflecting the main rocket thrust vector so that it does not pass through the mass centre. Because the line of action is generally oriented nearly parallel to the [[Aircraft principal axes#Longitudinal axis (roll)|roll]] axis, roll control usually requires the use of two or more separately hinged nozzles or a separate system altogether, such as [[fins]], or vanes in the exhaust plume of the rocket engine, deflecting the main thrust. Thrust vector control (TVC) is only possible when the propulsion system is creating thrust; separate mechanisms are required for attitude and [[flight path]] control during other stages of flight.

Thrust vectoring can be achieved by four basic means:<ref name="Sutton ">George P. Sutton, Oscar Biblarz, ''Rocket Propulsion Elements'', 7th Edition.</ref><ref>Michael D. Griffin and James R. French, ''Space Vehicle Design'', Second Edition.</ref>

* [[Gimbaled thrust|Gimbaled]] engine(s) or nozzle(s)
* Reactive fluid injection
* Auxiliary "Vernier" thrusters
* Exhaust vanes, also known as jet vanes

====Gimbaled thrust====
{{main|gimbaled thrust}}
Thrust vectoring for many [[liquid rocket]]s is achieved by [[gimbaled thrust|gimbal]]ing the whole [[rocket engine|engine]]. This involves moving the entire [[combustion chamber]] and outer engine bell as on the [[Titan II]]'s twin first-stage motors, or even the entire engine assembly including the related [[fuel pump|fuel]] and [[oxidizer]] pumps. The [[Saturn V]] and the [[Space Shuttle]] used gimbaled engines.<ref name="Sutton" />

A later method developed for [[solid rocket propellant|solid propellant]] [[ballistic missile]]s achieves thrust vectoring by deflecting only the [[rocket nozzle|nozzle]] of the rocket using electric actuators or [[hydraulic cylinder]]s. The nozzle is attached to the missile via a [[ball joint]] with a hole in the centre, or a flexible seal made of a thermally resistant material, the latter generally requiring more [[torque]] and a higher power actuation system. The [[UGM-96 Trident I|Trident C4]] and [[UGM-133 Trident II|D5]] systems are controlled via hydraulically actuated nozzle. The [[Space Shuttle Solid Rocket Booster|STS SRB]]s used gimbaled nozzles.<ref name=RSRM-ALCS>{{cite journal |title=Reusable Solid Rocket Motor—Accomplishments, Lessons, and a Culture of Success |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001536.pdf |website=ntrs.nasa.gov |date=27 September 2011 |access-date=February 26, 2015 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304210207/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001536.pdf |url-status=live }}</ref>

====Propellant injection====
Another method of thrust vectoring used on [[solid rocket propellant|solid propellant]] [[ballistic missile]]s is liquid injection, in which the [[rocket nozzle]] is fixed, however a fluid is introduced into the [[Exhaust gas#Jet engines and rocket engines|exhaust]] flow from injectors mounted around the aft end of the missile. If the liquid is injected on only one side of the missile, it modifies that side of the exhaust plume, resulting in different thrust on that side thus an asymmetric net force on the missile. This was the control system used on the [[LGM-30 Minuteman#Minuteman-II (LGM-30F)|Minuteman II]] and the early [[SLBM]]s of the [[United States Navy]].

====Vernier thrusters====
An effect similar to thrust vectoring can be produced with multiple [[vernier thruster]]s, small auxiliary combustion chambers which lack their own turbopumps and can gimbal on one axis. These were used on the [[Atlas missile|Atlas]] and [[R-7 (rocket family)|R-7]] missiles and are still used on the [[Soyuz rocket]], which is descended from the R-7, but are seldom used on new designs due to their complexity and weight. These are distinct from [[reaction control system]] thrusters, which are fixed and independent rocket engines used for maneuvering in space.

====Exhaust vanes====
[[File:Antwerp V-2.jpg|thumb|Graphite exhaust vanes on a V-2 rocket engine's nozzle]]One of the earliest methods of thrust vectoring in rocket engines was to place vanes in the engine's exhaust stream. These exhaust vanes or jet vanes allow the thrust to be deflected without moving any parts of the engine, but reduce the rocket's efficiency. They have the benefit of allowing roll control with only a single engine, which nozzle gimbaling does not. The [[V-2 rocket|V-2]] used graphite exhaust vanes and aerodynamic vanes, as did the [[PGM-11 Redstone|Redstone]], derived from the V-2. The Sapphire and Nexo rockets of the amateur group [[Copenhagen Suborbitals]] provide a modern example of jet vanes. Jet vanes must be made of a refractory material or actively cooled to prevent them from melting. Sapphire used solid copper vanes for copper's high heat capacity and thermal conductivity, and Nexo used graphite for its high melting point, but unless actively cooled, jet vanes will undergo significant erosion. This, combined with jet vanes' inefficiency, mostly precludes their use in new rockets.