Editing Rocket (section)

==Design==
A rocket design can be as simple as a cardboard tube filled with [[black powder]], but to make an efficient, accurate rocket or missile involves overcoming a number of difficult problems. The main difficulties include cooling the combustion chamber, pumping the fuel (in the case of a liquid fuel), and controlling and correcting the direction of motion.<ref>{{Citation |author= Richard B. Dow |title=Fundamentals of Advanced Missiles |year=1958 |location=Washington (DC) |publisher=John Wiley & Sons |id=loc 58-13458}}</ref>

===Components===
Rockets consist of a [[rocket propellant|propellant]], a place to put propellant (such as a [[propellant tank]]), and a [[rocket engine nozzle|nozzle]]. They may also have one or more [[rocket engine]]s, [[Spacecraft attitude control|directional stabilization device(s)]] (such as [[fins]], [[vernier engine]]s or engine [[gimbal]]s for [[thrust vectoring]], [[gyroscope]]s) and a structure (typically [[monocoque]]) to hold these components together. Rockets intended for high speed atmospheric use also have an [[aerodynamic]] fairing such as a [[nose cone]], which usually holds the payload.<ref>{{Citation |author=United States Congress. House Select Committee on Astronautics and Space Exploration |title=Space handbook: Astronautics and its applications : Staff report of the Select Committee on Astronautics and Space Exploration |url=http://www.hq.nasa.gov/office/pao/History/conghand/spcover.htm |chapter=4. Rocket Vehicles |chapter-url=http://www.hq.nasa.gov/office/pao/History/conghand/vehicles.htm |series=House document / 86th Congress, 1st session, no. 86 |year=1959 |location=Washington (DC) |publisher=U.S. G.P.O. |oclc=52368435 |url-status=dead |archive-url=https://web.archive.org/web/20090618163819/http://www.hq.nasa.gov/office/pao/History/conghand/spcover.htm |archive-date=2009-06-18 |access-date=2009-07-20 }}</ref>

As well as these components, rockets can have any number of other components, such as wings ([[rocketplane]]s), [[parachute]]s, wheels ([[rocket car]]s), even, in a sense, a person ([[rocket belt]]). Vehicles frequently possess [[Automotive navigation system|navigation systems]] and [[guidance system]]s that typically use [[satellite navigation]] and [[inertial navigation system]]s.

===Engines===
{{Main|Rocket engine}}
[[File:Viking 5C rocketengine.jpg|thumb|upright|[[Viking (rocket engine)|Viking 5C]] rocket engine]]

Rocket engines employ the principle of [[jet engine|jet propulsion]].<ref name="RPE7"/> The rocket engines powering rockets come in a great variety of different types; a comprehensive list can be found in the main article, [[Rocket engine]]. Most current rockets are chemically powered rockets (usually [[internal combustion engines]],<ref>{{cite web |author=Charles Lafayette Proctor II |url=http://concise.britannica.com/ebc/article-9368065/internal-combustion-engine |title=internal combustion engines |publisher=Concise Britannica |access-date=2012-12-10 |url-status=dead |archive-url=https://web.archive.org/web/20080114004538/http://concise.britannica.com/ebc/article-9368065/internal-combustion-engine |archive-date=2008-01-14 }}</ref> but some employ a decomposing [[monopropellant]]) that emit a hot [[exhaust gas]]. A rocket engine can use gas propellants, [[Solid-fuel rocket|solid propellant]], [[liquid-propellant rocket|liquid propellant]], or a [[hybrid rocket|hybrid mixture of both solid and liquid]]. Some rockets use heat or pressure that is supplied from a source other than the [[chemical reaction]] of propellant(s), such as [[steam rocket]]s, [[solar thermal rocket]]s, [[nuclear thermal rocket]] engines or simple pressurized rockets such as [[water rocket]] or [[cold gas thruster]]s. With combustive propellants a chemical reaction is initiated between the [[fuel]] and the [[oxidizer]] in the [[combustion]] chamber, and the resultant hot gases accelerate out of a [[rocket engine nozzle]] (or [[nozzle]]s) at the rearward-facing end of the rocket. The [[acceleration]] of these gases through the engine exerts force ("thrust") on the combustion chamber and nozzle, propelling the vehicle (according to [[Newton's third law]]). This actually happens because the force (pressure times area) on the combustion chamber wall is unbalanced by the nozzle opening; this is not the case in any other direction. The shape of the nozzle also generates force by directing the exhaust gas along the axis of the rocket.<ref name="RPE7"/>

===Propellant===
{{Main|Rocket propellant}}
[[File:Gas Core light bulb.png|thumb|left|Gas Core light bulb]]

Rocket propellant is mass that is stored, usually in some form of [[propellant]] tank or casing, prior to being used as the propulsive mass that is ejected from a [[rocket engine]] in the form of a [[fluid]] [[jet (fluid)|jet]] to produce [[thrust]].<ref name="RPE7"/> For chemical rockets often the propellants are a fuel such as [[liquid hydrogen]] or [[kerosene]] burned with an oxidizer such as [[liquid oxygen]] or [[nitric acid]] to produce large volumes of very hot gas. The oxidiser is either kept separate and mixed in the combustion chamber, or comes premixed, as with solid rockets.

Sometimes the propellant is not burned but still undergoes a chemical reaction, and can be a 'monopropellant' such as [[hydrazine]], [[nitrous oxide]] or [[hydrogen peroxide]] that can be [[catalyst|catalytically]] decomposed to hot gas.

Alternatively, an inert propellant can be used that can be externally heated, such as in [[steam rocket]], [[solar thermal rocket]] or [[nuclear thermal rocket]]s.<ref name="RPE7"/>

For smaller, low performance rockets such as [[attitude control thruster]]s where high performance is less necessary, a pressurised fluid is used as propellant that simply escapes the spacecraft through a propelling nozzle.<ref name="RPE7"/>

=== Pendulum rocket fallacy ===
[[File:Pendulum rocket fallacy.png|thumb|Illustration of the pendulum rocket fallacy. Whether the motor is mounted at the bottom (left) or top (right) of the vehicle, the thrust vector (T) points along an axis that is fixed to the vehicle (top), rather than pointing vertically (bottom) independent of vehicle attitude, which would lead the vehicle to rotate.]]

The first [[liquid-fuel rocket]], constructed by [[Robert H. Goddard]], differed significantly from modern rockets. The [[rocket engine]] was at the top and the fuel tank at the bottom of the rocket,<ref>{{cite book |url=http://dln.nasa.gov/media/storage/DNY9-12activities.pdf |publisher=NASA |title=Discover NASA and You |archive-url=https://web.archive.org/web/20100527221503/http://dln.nasa.gov/media/storage/DNY9-12activities.pdf |archive-date=2010-05-27 |url-status=dead }}</ref> based on Goddard's belief that the rocket would achieve stability by "hanging" from the engine like a [[pendulum]] in flight.<ref>{{cite AV media |people=[[Scott Manley]] |title=The Pendulum Rocket Fallacy |medium=[[YouTube]] |url=https://www.youtube.com/watch?v=Tx4cjP-GRAY | archive-url=https://ghostarchive.org/varchive/youtube/20211030/Tx4cjP-GRAY| archive-date=2021-10-30|access-date=2020-10-02}}{{cbignore}}</ref> However, the rocket veered off course and crashed {{convert|184|ft}} away from the [[launch pad|launch site]],<ref>{{cite book|last=Streissguth|first=Thomas|title=Rocket man: the story of Robert Goddard|publisher=Twenty-First Century Books|year=1995|pages=[https://archive.org/details/rocketmanstoryof00stre/page/37 37]|isbn=0-87614-863-1|url-access=registration|url=https://archive.org/details/rocketmanstoryof00stre/page/37}}</ref> indicating that the rocket was no more stable than one with the rocket engine at the base.<ref name="Sutton">{{cite book|last=Sutton|first=George P.|title=History of Liquid Propellant Rocket Engines|year=2006|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Virginia|pages=267, 269}}</ref>