Rocket
26301
226182979
2008-07-17T05:37:58Z
DonPMitchell
160791
/* Theories of interplanetary rocketry */ Mention REP in 1912. Only Goddard's space/Moon rocket idea was ridiculed, not the bulk of the work.
{{otheruses1|vehicles powered by rocket engines}}
[[Image:Soyuz rocket ASTP.jpg|thumb|right|A Soyuz rocket, at Baikonur launch pad.]]
[[Image:Chinese rocket.gif|thumb|right|Early Chinese rocket.]] A '''rocket''' or '''rocket vehicle''' is a [[missile]], [[aircraft]] or other [[vehicle]] which obtains [[thrust]] by the [[Reaction (physics)|reaction]] of the rocket to the ejection of fast moving [[fluid]] from a [[rocket engine]]. Chemical rockets work by the action of hot gas produced by the combustion of the [[propellant]] against the inside of [[combustion chamber]]s and [[Rocket engine nozzle|expansion nozzle]]s. This generates forces that accelerate the gas to [[hypersonic|extremely high speed]] and exert a large thrust on the rocket (since [[Newton's third law|every action has an equal and opposite reaction]]).
The history of rockets goes back to at least the [[13th century]].<ref name="NASAEARLY">[http://history.msfc.nasa.gov/rocketry/tl1.html Rockets in Ancient Times (100 B.C. to 17th Century)]</ref> By the [[20th century]], they have enabled human [[spaceflight]] to the Moon. In the [[21st century]], they have made commercial [[space tourism]] possible.
Rockets are used for [[fireworks]] and weaponry, as [[launch vehicle]]s for [[artificial satellite]]s, [[human spaceflight]] and [[Space exploration| exploration]] of other planets. While inefficient for low speed use, they are, compared to other propulsion systems, very lightweight and powerful, capable of attaining [[escape velocity|extremely high speeds]] with reasonable efficiency.
Chemical rockets store a large amount of energy in an easily-released form, and can be very dangerous. However, careful design, testing, construction, and use minimize the risks.
== History of rockets ==
{{seealso|Timeline of rocket and missile technology}}
=== In antiquity ===
The availability of black powder ([[gunpowder]]) to propel projectiles was a precursor to the development of the first solid rocket. [[9th century|Ninth Century]] [[Chinese people|Chinese]] [[Taoist]] [[Alchemy|alchemists]] discovered black powder while searching for the [[Elixir of life]]; this accidental discovery led to experiments in the form of weapons like [[bomb]]s, [[cannon]], incendiary [[fire arrow]]s and rocket-propelled fire arrows.
Exactly when the first flights of rockets occurred is contested. Some say that the first recorded use of a rocket in battle was by the Chinese in 1232 against the Mongol hordes. There were reports of fire arrows and 'iron pots' that could be heard for 5 [[leagues]] (15 miles) when they exploded upon impact, causing devastation for a radius of 2,000 feet, apparently due to shrapnel.<ref>[http://www.solarviews.com/eng/rocket.htm A Brief History of Rocketry]</ref> The lowering of the iron pots may have been a way for a besieged army to blow up invaders. The fire arrows were either arrows with explosives attached, or arrows propelled by gunpowder, such as the Korean [[Hwacha]].<ref><small>
(正大九年)其守城之具有火砲名「震天雷」者,铁罐盛药,以火点之,砲起火发,其声如雷,闻百里外,所爇围半亩之上,火点著甲铁皆透。(蒙古)大兵又为牛皮洞,直至城下,掘城为龛,间可容人,则城上不可奈何矣。人有献策者,以铁绳悬「震天雷」者,顺城而下,至掘处火发,人与牛皮皆碎迸无迹。又「飞火枪」,注药以火发之,辄前烧十余步,人亦不敢近。(蒙古)大兵惟畏此二物云。(Rough Translation: [Year 1232] Among the weaponry at the defense city [Kaifeng] are the "thundercrash", which were made of iron pot, and filled with drugs [black powder], when lighted with fire, it exploded, making a noise like thunder. It could be heard over 100 ''li'', and could toasted more than a third of an acre, moreover it could penetrate the armours and iron. The [Mongol] soldiers employed a siege carriage cloaked with cowskin and advance to the city below, they grubbed a niche on the city-wall, which could spare a man between. The [Jin] defenders atop did not know what to do, later an advice had offered. The pot was then dropped with an iron string from the fortress, it reached to the niche area and exploded, men and carriage were blown to pieces without trace. They also have the "flying fire-lance", which was infused with drug [black powder] and ignited it, it flames within a range of over ten paces on the front, men are not dare to near. It is say that the [Mongol] soldiers only terrify by these two objects.) History of Jin ch. 113</small></ref>
Less controversially, one of the earliest devices recorded that used internal-combustion rocket propulsion was the 'ground-rat,' a type of [[firework]], recorded in 1264 as having frightened the Empress-Mother Kung Sheng at a feast held in her honor by her son the [[Emperor Lizong]].<ref>{{cite book | last = Crosby | first = Alfred W. | title = Throwing Fire: Projectile Technology Through History | year = 2002 | publisher = Cambridge University Press | location = Cambridge | id = ISBN 0521791588 | pages = 100–103}}</ref>
Subsequently, one of the earliest texts to mention the use of rockets was the ''[[Huolongjing]]'', written by the Chinese artillery officer [[Jiao Yu]] in the mid-14th century. This text also mentioned the use of the first known [[multistage rocket]], the 'fire-dragon issuing from the water' (huo long chu shui), used mostly by the Chinese navy.<ref name="needham volume 5 part 7 510">Needham, Volume 5, Part 7, 510.</ref> Frank H. Winter proposed in ''The Proceedings of the Twentieth and Twenty-First History Symposia of the International Academy of Astronautics''<ref>Frank H. Winter, "The `Boun Bang Fai' Rockets of Thailand and Laos:," in Lloyd H. Cornett, Jr., ed., History of Rocketry and Astronautics - Proceedings of the Twentieth and Twenty-First History Symposia of the International Academy of Astronautics, AAS History Series, Vol. 15 (Univelt Inc.: San Diego, 1993), pp. 3-24.</ref> that southern China and the [[Laos|Laotian]] community [[Rocket Festival|rocket festivals]] might have been key in the subsequent spread of rocketry in the Orient.
=== Spread of rocket technology ===
[[Image:Genghis Khan.jpg|thumb|[[Genghis Khan]]'s Mongols spread Chinese technology]]
Rocket technology first became known to [[Europe]]ans following their use by the [[Mongol]]s [[Genghis Khan]] and [[Ögedei Khan]] when they conquered parts of Russia, Eastern, and Central Europe. The Mongolians had acquired the Chinese technology by conquest of the northern part of China and also by the subsequent employment of Chinese rocketry experts as [[mercenaries]] for the Mongol military. Reports of the Battle of Sejo in the year 1241 describe the use of rocket-like weapons by the Mongols against the [[Magyars]].<ref name="nasa">{{cite web|url=http://science.ksc.nasa.gov/history/rocket-history.txt|title=NASA Spacelink - "A brief history of rocketry"|accessdate=2006-08-19}}</ref> Rocket technology also spread to [[Korea]], with the 15th century wheeled [[hwacha]] that would launch [[singijeon]] rockets. These first Korean rockets had an amazingly long range at the time, and were designed and built by Byun Eee-Joong. They were just like arrows but had small explosives attached to the back, and were fired in swarms.
Additionally, the spread of rockets into Europe was also influenced by the [[Ottoman Empire|Ottomans]] at the siege of [[Constantinople]] in 1453, although it is very likely that the Ottomans themselves were influenced by the Mongol invasions of the previous few centuries. They appear in literature describing the capture of Baghdad in 1258 by the Mongols.<ref name="nasa"/>
In their history of rockets published on the Internet, [[NASA]] says “the Arabs adopted the rocket into their own arms inventory and, during the [[Seventh Crusade]], used them against the French Army of King [[Louis IX]] in 1268.".<ref>[http://www.solarviews.com/eng/rocket.htm A Brief History of Rocketry]</ref>
The name ''Rocket'' comes from the [[Italian language|Italian]] ''Rocchetta'' (i.e. ''little fuse''), a name of a small firecracker created by the Italian artificer Muratori in 1379.<ref>Von Braun, Wernher & Frederick I. Ordway, III. ''HISTORY OF ROCKETRY AND SPACE TRAVEL'', 1966</ref>
"''Artis Magnae Artilleriae pars prima''" ("Great Art of Artillery, the First Part", also known as "The Complete Art of Artillery"), first printed in [[Amsterdam]] in 1650, was translated to [[French language|French]] in 1651, [[German language|German]] in 1676, [[English language|English]] and [[Dutch language|Dutch]] in 1729 and [[Polish language|Polish]] in 1963. For over two centuries, this work of [[Polish-Lithuanian Commonwealth]] [[szlachta|nobleman]] [[Kazimierz Siemienowicz]]<ref name="Nowak182">Tadeusz Nowak "''Kazimierz Siemienowicz, ca.1600-ca.1651''", MON Press, [[Warsaw]] 1969, p.182</ref> was used in [[Europe]] as a basic artillery manual. The book provided the standard designs for creating rockets, [[fireball]]s, and other [[pyrotechnic]] devices. It contained a large chapter on caliber, construction, production and properties of rockets (for both military and civil purposes), including [[Multistage rocket|multi-stage]] rockets, batteries of rockets, and rockets with [[delta wing]] [[Stabilizer (aircraft)|stabilizer]]s (instead of the common guiding rods).
In 1792, [[iron]]-cased rockets were successfully used militarily by [[Tipu Sultan]], Ruler of the [[Kingdom of Mysore]] in [[India]] against the larger [[British East India Company]] forces during the [[Anglo-Mysore Wars]]. The British then took an active interest in the technology and developed it further during the 19th century. The major figure in the field at this time was [[William Congreve (inventor)|William Congreve]].<ref name="congreve">Stephen Leslie (1887) ''Dictionary of National Biography'', Vol.XII, p.9, Macmillan & Co., New York [http://books.google.com/books?id=YTcJAAAAIAAJ&pg=PA9&lpg=PA9&dq=a+concise+account+of+the+origin+and+progress+of+the+rocket+system&source=web&ots=Ckd6Dx5VJL&sig=cf_2GUuMbboUCnwJfE2hHuXCD3o Congreve, Sir William,]</ref> From there, the use of military rockets spread throughout Europe. At the [[Battle of Baltimore]] in 1814, the rockets fired on [[Fort McHenry]] by the [[rocket vessel]] [[HMS Erebus (1807)|HMS ''Erebus'']] were the source of the ''rockets' red glare'' described by [[Francis Scott Key]] in [[The Star-Spangled Banner]].<ref>[http://www.nps.gov/history/history/online_books/hh/5/hh5l.htm British Rockets] at the US National Parks Service, Fort McHenry National Monument and Historic Shrine. Accessed February 2008.</ref> Rockets were also used in the [[Battle of Waterloo]].<ref>[http://www.napoleonic-literature.com/Articles/Rockets/History_of_Rockets.htm History of the Rocket - 1804 to 1815 by Gareth Glover]</ref>
=== Accuracy of early rockets ===
[[Image:Congreve rockets.gif|thumb|The Congreve rocket]]
Early rockets were very inaccurate. Without the use of spinning or any [[gimbal]]ling of the thrust, they had a strong tendency to veer sharply off course. The early British [[Congreve rocket]]s<ref name="congreve"/> reduced this somewhat by attaching a long stick to the end of a rocket (similar to modern bottle rockets) to make it harder for the rocket to change course. The largest of the Congreve rockets was the 32-pound (14.5 kg) Carcass, which had a 15-foot (4.6 m) stick. Originally, sticks were mounted on the side, but this was later changed to mounting in the center of the rocket, reducing drag and enabling the rocket to be more accurately fired from a segment of pipe.
The British were greatly impressed by the [[Mysore]]an [[Rocket artillery]] made from iron tubes used by the armies of [[Tipu Sultan]] and his father, [[Haidar Ali]]. Tipu Sultan championed the use of mass attacks with rocket brigades in the army. The effect of these weapons on the British during the [[Second Anglo-Mysore War|Second]], [[Third Mysore War|Third]] and [[Fourth Mysore War]]s was sufficiently impressive to inspire William Congreve to develop his own rocket designs. Several Mysore rockets were sent to England, and after thoroughly examining the Indian specimens, from 1801, William Congreve, son of the Comptroller of the Royal Arsenal, Woolwich, London, set on a vigorous research and development programme at the Arsenal's laboratory. Congreve prepared a new propellant mixture, and developed a rocket motor with a strong iron tube with conical nose, weighing about 32 pounds (14.5 kilograms). The Royal Arsenal's first demonstration of solid fuel rockets was in 1805. The rockets were effectively used during the Napoleonic Wars and the War of 1812. Congreve published three books on rocketry.
In 1815, [[Alexander Dmitrievich Zasyadko]] began his work on creating military gunpowder rockets. He constructed rocket-launching platforms, which allowed to fire in salvos (6 rockets at a time), and gun-laying devices. Zasyadko elaborated a tactic for military use of rocket weaponry. In 1820, Zasyadko was appointed head of the Petersburg Armory, Okhtensky Powder Factory, pyrotechnic laboratory and the first Highest Artillery School in Russia. He organized rocket production in a special rocket workshop and created the first rocket sub-unit in the Russian army.<ref>[http://www.globalsecurity.org/military/library/report/1987/MAF.htm Marine Corps Artillery Rockets: Back Through The Future]</ref>
The accuracy problem was mostly solved in 1844 when [[William Hale (British inventor)|William Hale]]<ref name="SMITH">{{cite web |url=http://www.nasm.si.edu/research/dsh/artifacts/RM-Hale24pdr.htm |title=Smithsonian article on Hale rockets}}</ref> modified the rocket design so that thrust was slightly [[thrust vectoring|vectored]], causing the rocket to spin along its axis of travel like a bullet. The Hale rocket removed the need for a rocket stick, travelled further due to reduced air resistance, and was far more accurate.
===Early manned rocketry===
According to legend, a manned [[rocket sled]] with 47 gunpowder-filled rockets was attempted in [[China]] by [[Wan Hu]] in the 16th Century<ref name="zim">[http://www.amazon.com/dp/B0007DXH14 ''Rockets and Jets'' by [[United States|American]] author [[Herbert S. Zim]] in 1945]</ref>. The alleged flight is said to have been interrupted by an explosion at the start, and the pilot did not seem to have survived (he was never found). There are no known Chinese sources for this event, and the earliest known account is an unsourced reference in a book by an American, [[Herbert S. Zim]] in 1945<ref name="zim"/>.
In [[Ottoman Turkey]] in 1633, [[Lagari Hasan Çelebi]] took off with what was described as a cone-shaped rocket, glided with wings through [[Bosporus]] from Topkap Palace, and made a successful landing, winning him a position in the [[Ottoman Empire|Ottoman]] army.<ref>Winter, Frank H. (1992). "Who First Flew in a Rocket?", Journal of the British Interplanetary Society 45 (July 1992), p. 275-80</ref> The flight was accomplished as a part of celebrations performed for the birth of Ottoman Emperor Murat IV's daughter and was rewarded by the sultan. The device was composed of a large winged cage with a conical top with 7 rockets filled with 70 kg of gunpowder. The flight was estimated to have lasted about 200 seconds and the maximum height reached around 300 metres.
===Theories of interplanetary rocketry===
[[Image:Tsiolkovsky.jpg|thumb|left|Konstantin Tsiolkovsky published the first work on space travel]]
In 1903, high school mathematics teacher [[Konstantin Tsiolkovsky]] (1857–1935) published ''Исследование мировых пространств реактивными приборами''<ref>[http://epizodsspace.testpilot.ru/bibl/dorev-knigi/ciolkovskiy/issl-03st.html Tsiolkovsky's Исследование мировых пространств реактивными приборами - ''The Exploration of Cosmic Space by Means of Reaction Devices'' (Russian paper)]</ref> (''The Exploration of Cosmic Space by Means of Reaction Devices''), the first serious scientific work on space travel. The [[Tsiolkovsky rocket equation]]—the principle that governs rocket propulsion—is named in his honor (although it had been discovered previously<ref>Johnson W., "Contents and commentary on William Moore's a treatise on the motion of rockets and an essay on naval gunnery", International Journal of Impact Engineering, Volume 16, Number 3, June 1995, pp. 499-521</ref>). His work was essentially unknown outside the Soviet Union, where it inspired further research, experimentation and the formation of the Cosmonautics Society.
In 1912, [[Robert Esnault-Pelterie]] published a lecture on rocket theory and interplanetary travel. He independantly derived Tsiolkovsky's rocket equation, did basic calculations about the energy required to make round trips to the Moon and planets, and he proposed the use of atomic power (i.e. Radium) to power a jet drive.
[[Image:Robert Goddard.jpg|thumb|right|Robert Goddard]]
In 1920, [[Robert Goddard (scientist)|Robert Goddard]] published ''[[A Method of Reaching Extreme Altitudes]]''<ref>[http://www.clarku.edu/research/archives/pdf/ext_altitudes.pdf A Method of Reaching Extreme Altitudes- Goddard 1919]</ref>, the next serious work on using rockets in space travel after [[Tsiolkovsky]]. The work included remarks about sending a rocket to the Moon, which attracted worldwide attention and was both praised and ridiculed. A New York Times editorial famously expressed disbelief that it was possible at all as it stated that: ''"after the rocket quits our air and really starts on its longer journey it will neither be accelerated nor maintained by the explosion of the charges it then might have left"'' and suggested that Professor Goddard actually: ''"does not know of the relation of action to reaction, and the need to have something better than a vacuum against which to react"'' and talked of ''"such things as intentional mistakes or oversights."''
Goddard, the Times declared, apparently suggesting bad faith, ''"only '''seems''' to lack the knowledge ladled out daily in high schools."''<ref>{{cite news |first= |last= |authorlink= |coauthors= |title=Topics of the Times |url=http://it.is.rice.edu/~rickr/goddard.editorial.html |quote=As a method of sending a missile to the higher, and even highest, part of the earth's atmospheric envelope, Professor Goddard's multiple-charge rocket is a practicable, and therefore promising device. Such a rocket, too, might carry self-recording instruments, to be released at the limit of its flight, and conceivable parachutes would bring them safely to the ground. It is not obvious, however, that the instruments would return to the point of departure; indeed, it is obvious that they would not, for parachutes drift exactly as balloons do. And the rocket, or what was left of it after the last explosion, would have to be aimed with amazing skill, and in dead calm, to fall on the spot where it started. |publisher=[[New York Times]] |date=[[January 13]], [[1920]] |accessdate=2007-06-21 }}</ref>
After these and other scathing criticisms, Goddard began working in isolation, and avoided publicity.
Nevertheless, in Russia, Tsiolkovsky's work was republished in the 1920s in response to Russian interest raised by the work of Robert Goddard and Hermann Oberth. Among other ideas, Tsiolkovsky accurately proposed to use liquid oxygen and liquid hydrogen as a nearly optimal propellant pair and determined that building staged and clustered rockets to increase the overall mass efficiency would dramatically increase range.
In 1923, [[Hermann Oberth]]<ref name="ianzer">{{ro icon}} Jürgen Heinz Ianzer, [http://www.aspera.ro/dl/oberth.pdf ''Hermann Oberth, pǎrintele zborului cosmic'' ("Hermann Oberth, Father of the Cosmic Flight")], p. 3, 11, 13, 15.</ref> (1894–1989) published ''Die Rakete zu den Planetenräumen'' ("The Rocket into Planetary Space"), a version of his doctoral thesis, after the University of Munich rejected it.
=== Modern rocketry ===
====Pre-World War II====
[[Image:Goddard and Rocket.jpg|thumb|Robert Goddard and the first liquid-fueled rocket.]]
Modern rockets were born when Goddard attached a supersonic ([[de Laval nozzle|de Laval]]) nozzle to a liquid fuelled rocket engine's combustion chamber. These nozzles turn the hot gas from the combustion chamber into a cooler, [[hypersonic]], highly directed jet of gas, more than doubling the thrust and raising the engine efficiency from 2% to 64%<ref>Goddard, Robert H., Rockets [Mineola, N.Y.: Dover Publications, 2002], pp. 2, 15.</ref><ref>Clary, David A., Rocket Man: Robert H. Goddard and the Birth of the Space Age [N.Y., N.Y.: Hyperion, 2003], pp. 44-45.</ref>. Early rockets had been grossly inefficient because of the thermal energy that was wasted in the exhaust gases. In 1926, Robert Goddard launched the world's first liquid-fueled rocket in [[Auburn, Massachusetts]].
[[Image:AMBA Pioneers.jpg|300px|thumb|left|Hermann Oberth (in front) with fellow [[Army Ballistic Missile Agency|ABMA]] employees. Left to right: Dr. [[Ernst Stuhlinger]], Major General [[Holger Toftoy]], [[Hermann Oberth|Oberth]], Dr. [[Wernher von Braun]], and Dr. [[Robert Lusser]].]]
During the 1920s, a number of rocket research organizations appeared in the United States, Austria, Britain, Czechoslovakia, France, Italy, Germany, and Russia. In the mid-1920s, [[Weimar Republic|German]] scientists had begun experimenting with rockets which used liquid propellants capable of reaching relatively high altitudes and distances.
1927 the German car manufacturer [[Opel]] began to research with rockets together with Mark Valier and the rocket builder Friedrich Wilhelm Sander. In 1928, Fritz von Opel drove with a rocket car, the Opel RAK1 on the Opel raceway in Rüsselsheim, Germany. In 1929 von Opel started at the Frankfurt-Rebstock airport with the Opel-Sander RAK 1-airplane. This was maybe the first flight with a manned rocket-aircraft.
In 1927 and also in Germany, a team of amateur rocket engineers had formed the ''[[Verein für Raumschiffahrt]]'' (German Rocket Society, or VfR), and in 1931 launched a liquid propellant rocket (using [[oxygen]] and [[petrol|gasoline]]).<ref>[http://www.daviddarling.info/encyclopedia/V/Verein_fur_Raumschiffahrt.html HISTORY OF ROCKETRY: Verein für Raumschiffahrt (VfR)]</ref>
From 1931 to 1937, the most extensive scientific work on rocket engine design occurred in Leningrad, at the Gas Dynamics Laboratory. Well-funded and staffed, over 100 experimental engines were built under the direction of [[Valentin Glushko]]. The work included [[regenerative cooling]], [[hypergolic propellant]] ignition, and [[fuel injector]] designs that included swirling and bi-propellant mixing injectors. However, the work was curtailed by Glushko's arrest during [[Great Purge|Stalinist purges]] in 1938. Similar work was also done by the Austrian professor [[Eugen Sänger]] who worked on rocket powered spaceplanes such as [[Silbervogel]] (sometimes called the 'antipodal' bomber.)<ref>[http://www.astronautix.com/data/saenger.pdf A Rocket Drive For Long Range Bombers by E. Saenger and J. Bredt, August 1944]</ref>
On November 12, 1932 at a farm in Stockton NJ, the American Interplanetary Society's attempt to static fire their first rocket (based on German Rocket Society designs) fails in a fire.<ref>{{Citation
| last1 = Winter| first1 = Frank H
| last = van der Linden| first2 = Robert
| title = Out of the Past
| magazine = Aerospace America
| date = November 2007 | year = 2007 |pages=p39}}</ref>
In 1932, the ''[[Reichswehr]]'' (which in 1935 became the ''[[Wehrmacht]]'') began to take an interest in rocketry. Artillery restrictions imposed by the [[Treaty of Versailles]] limited Germany's access to long distance weaponry. Seeing the possibility of using rockets as long-range [[artillery]] fire, the Wehrmacht initially funded the VfR team, but seeing that their focus was strictly scientific, created its own research team. At the behest of military leaders, [[Wernher von Braun]], at the time a young aspiring rocket scientist, joined the military (followed by two former VfR members) and developed long-range weapons for use in [[World War II]] by [[Nazi Germany]], notably the [[Aggregate series|A-series of rockets]], which led to the infamous [[V-2 rocket]] (initially called A4).<ref>[http://www.russianspaceweb.com/a4.html The V-2 ballistic missile]</ref>
====World War II====
[[Image:V-2 Rocket On Meillerwagen.jpg|left|thumb|A German V-2 rocket on a [[Meillerwagen]].]]
[[Image:V-2 rocket diagram (with English labels).svg|thumb|right|Layout of a V2 rocket]]
In 1943, production of the [[V-2 rocket]] began. The V-2 had an operational range of 300 km (185 miles) and carried a 1000 kg (2204 lb) warhead, with an [[amatol]] explosive charge. Highest point of altitude of its flight trajectory is 90 km. The vehicle was only different in details from most modern rockets, with [[turbopump]]s, [[Guidance system|inertial guidance]] and many other features. Thousands were fired at various [[Allies|Allied]] nations, mainly England, as well as Belgium and France. While they could not be intercepted, their guidance system design and single conventional warhead meant that the V-2 was insufficiently accurate against military targets. The later versions however, were more accurate, sometimes within metres, and could be devastating.<ref>[http://www.v2rocket.com/start/deployment/mobileoperations.html A4/V2 Mobile Firing Operations 1944-45]</ref> 2,754 people in England were killed, and 6,523 were wounded before the launch campaign was terminated. While the V-2 did not significantly affect the course of the war, it provided a lethal demonstration of the potential for guided rockets as weapons.
Under ''Projekt Amerika'' Nazi Germany also tried to develop and use the first [[submarine-launched ballistic missile]] (SLBMs) and the first [[intercontinental ballistic missiles]] (ICBMs) [[Aggregate series|A9/A10 ''Amerika-Raketen'']]<ref>[http://www.astronautix.com/lvs/a9a10.htm A9/A10]</ref> to bomb New York and other American cities. The tests of SLBM-variants of the A4 rocket was achieved with [[U-boat]] submarines towing launch platforms. The second stage of the A9/A10 rocket was tested a few times in January, February and March 1945.
In parallel with the guided missile programme in Nazi Germany, rockets were also being used for aircraft, either for rapid horizontal take-off ([[JATO]]) or for powering the aircraft ([[Me 163]],etc) and for vertical take-off ([[Bachem Ba 349]] "Natter").
====Post World War II====
[[Image:Dornberger-Axter-von Braun.jpg|thumb|Dornberger and Von Braun after being captured by the Allies]]
At the end of World War II, competing Russian, British, and U.S. military and scientific crews raced to capture technology and trained personnel from the German rocket program at [[Peenemünde]]. Russia and [[United Kingdom|Britain]] had some success, but the United States benefited the most. The US captured a large number of German rocket scientists (many of whom were members of the [[National Socialist German Workers Party|Nazi Party]], including von Braun) and brought them to the United States as part of [[Operation Paperclip]]<ref>http://www.archives.gov/iwg/declassified-records/rg-330-defense-secretary/ Joint Intelligence Objectives Agency. U.S. National Archives and Records Administration]</ref>. In America, the same rockets that were designed to rain down on [[United Kingdom|Britain]] were used instead by scientists as research vehicles for developing the new technology further. The V-2 evolved into the American [[Redstone rocket]], used in the early space program.
After the war, rockets were used to study high-altitude conditions, by radio [[telemetry]] of temperature and pressure of the atmosphere, detection of [[cosmic rays]], and further research; notably for the [[Bell X-1]] to break the sound barrier. This continued in the U.S. under von Braun and the others, who were destined to become part of the U.S. scientific complex.
[[Image:Semyorka Rocket R7 by Sergei Korolyov in VDNH Ostankino RAF0540.jpg|left|thumb|250px|R-7 8K72 "[[Vostok rocket|Vostok]]"]]
Independently, research continued in the [[Soviet Union]] under the leadership of the chief designer [[Sergei Korolev]]<ref>[http://www.nmspacemuseum.org/halloffame/detail.php?id=15 International Space Hall of Fame: Sergei Korolev]</ref>. With the help of German technicians, the V-2 was duplicated and improved as the [[R-1 (rocket)|R-1]], [[R-2 rocket|R-2]] and [[R-5 (rocket)|R-5]] missiles. German designs were abandoned in the late 1940s, and the foreign workers were sent home. A new series of engines built by Glushko and based on inventions of [[Aleksei Mihailovich Isaev]] formed the basis of the first ICBM, the [[R-7 (rocket)|R-7]].<ref>
{{cite web | url = http://www.energia.ru/english/energia/launchers/rocket-r7.html | title = Rocket R-7 | publisher = S.P.Korolev RSC Energia}}</ref> The R-7 launched the first satellite, and [[Yuri Gagarin]], the first man into space and the first lunar and planetary probes, and is still in use today. These events attracted the attention of top politicians, along with more money for further research.
Rockets became extremely important militarily in the form of modern [[intercontinental ballistic missiles]] (ICBMs) when it was realised that [[nuclear weapons]] carried on a rocket vehicle were essentially not defensible against once launched, and ICBM/Launch vehicles such as the R-7, [[Atlas (rocket family)|Atlas]] and [[Titan (rocket family)|Titan]] became the delivery platform of choice for these weapons.
[[Image:As10-27-3881.jpg|thumb|The Apollo 10 Command Module in orbit around the moon]]
Fueled partly by the [[Cold War]], the 1960s became the decade of rapid development of rocket technology particularly in the Soviet Union ([[Vostok rocket|Vostok]], [[Soyuz launch vehicle|Soyuz]], [[Proton rocket|Proton]]) and in the United States (e.g. the [[X-15]]<ref>[http://history.nasa.gov/monograph18.pdf (PDF) ''Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane'' (NASA SP-2000-4518, 2000)]</ref> and [[X-20 Dyna-Soar]]<ref>{{cite book |last=Houchin |first=Roy |title=U.S. Hypersonic Research and Development: The Rise and Fall of Dyna-Soar, 1944–1963 |year=2006 |publisher=Routledge |location=New York |id=ISBN 0-415-36281-4}}</ref> aircraft). There was also significant research in other countries, such as Britain, Japan, Australia, etc. and their growing use for [[Space exploration]], with pictures returned from the far side of the [[Moon]] and unmanned flights for [[Mars exploration]].
In America the manned programmes, [[Project Mercury]], [[Project Gemini]] and later the [[Apollo programme]] culminated in 1969 with the first manned [[Moon landing|landing on the moon]] via the [[Saturn V]], causing the New York Times to retract their earlier editorial implying that spaceflight couldn't work:
''"Further investigation and experimentation have confirmed the findings of Isaac Newton in the 17th century and it is now definitely established that a rocket can function in a vacuum as well as in an atmosphere. The Times regrets the error."''<ref>New York Times 17 June 1969 - A Correction</ref>
In the 1970s America made further lunar landings, before abandoning the Apollo launch vehicle. The replacement vehicle, the partially reusable '[[Space Shuttle]]' was intended to be cheaper, but this large reduction in costs was largely not achieved. Meanwhile in 1973, the expendable [[Ariane (rocket)|Ariane]] programme was begun, a launcher that by the year 2000 would capture much of the geosat market.
==== Current day ====
Rockets remain a popular military weapon. The use of large battlefield rockets of the V-2 type has given way to guided [[missiles]]. However rockets are often used by [[helicopter]]s and light aircraft for ground attack, being more powerful than [[machine gun]]s, but without the recoil of a heavy [[cannon]]. In the 1950s there was a brief vogue for [[air-to-air rocket]]s, ending with the [[AIR-2]] 'Genie' [[Nuclear weapon|nuclear]] rocket,<ref>[http://www.museumofaviation.org/aircraftCollection/missiles_drones/04-air2a.htm Mcdonnell Douglas AIR-2A "Genie" rocket]</ref> but by the early 1960s these had largely been abandoned in favor of [[air-to-air missile]]s.
[[Image:SpaceShipOne Nose.jpg|thumb|SpaceShipOne]]
Economically, rocketry is the enabler of all [[space technology|space technologies]] particularly satellites, many of which impact people's everyday lives in almost countless ways, [[global positioning system| satellite navigation]],<ref>[http://www.losangeles.af.mil/library/factsheets/factsheet.asp?id=5311 GLOBAL POSITIONING SYSTEMS WING]</ref> [[communications satellites]] and even things as simple as [[weather satellites]].
Scientifically, rocketry has opened a window on our universe, allowing the launch of [[space probe]]s to explore our [[solar system]], [[Earth observation satellite|satellites to view the Earth]] itself, and space-based [[telescopes]] to obtain a clearer view of the rest of the [[universe]].<ref>[http://www.nasa.gov/audience/forstudents/postsecondary/features/F_NASA_Great_Observatories_PS.html NASA's great observatories]</ref>
However, in the minds of much of the public, the most important use of rockets is perhaps [[manned spaceflight]]. Vehicles such as the [[Space Shuttle]] for scientific research, the [[Soyuz spacecraft|Soyuz]] for orbital tourism and [[SpaceShipOne]] for suborbital tourism may show a trend towards greater commercialisation of manned rocketry,<ref>[http://www.futron.com/resource_center/space_tourism/download_form.htm Futron report]</ref> away from government funding, and towards more widespread [[space access|access to space]].
== Types ==
There are many different types of rockets, and a comprehensive list of the basic engine types can be found in [[rocket engine]] — the vehicles themselves range in size from tiny [[model rocket|models]] such as [[water rocket]]s or small solid rockets that can be purchased at a [[hobby store]], to the enormous [[Saturn V]] used for the [[Apollo program]], and in many different vehicle types such as [[rocket car]]s and [[rocket plane]]s.
[[Image:Ksc-69pc-442.jpg|thumb|[[Saturn V]] is the biggest rocket to have successfully flown]]
Most current rockets are chemically powered rockets (usually [[internal combustion engines]]<ref>[http://concise.britannica.com/ebc/article-9368065/internal-combustion-engine Concise Britannica- internal combustion engines]</ref>, but some employ a decomposing [[monopropellant]]) that emit a hot [[exhaust gas]]. A chemical [[rocket engine]] can use gas propellant, [[Solid rocket booster|solid propellant]], [[liquid rocket|liquid propellant]], or a [[hybrid rocket|hybrid mixture of both solid and liquid]]. 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 [[nozzle]] (or nozzles) 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 (in accordance with Newton's Third Law). See [[rocket engine]] for details.
Rockets in which the heat is supplied from a source other than a propellant, such as [[solar thermal rocket]]s, can be classed as [[external combustion engines]]. Other examples of external combustion rocket engines include most designs for nuclear powered rocket engines. Use of [[hydrogen]] as the propellant for such engines gives very high exhaust velocities (around 6-10 km/s).<ref>[http://internet.cybermesa.com/~mrpbar/rocket.html Nuclear Rocket Technologies]</ref>
[[Image:Empty Water Rocket.png|left|thumb|Water rockets are flown for recreational purposes]][[Steam rocket]]s, are another example of non chemical rockets. These rockets release very hot water through a nozzle<ref>[http://www.tecaeromex.com/ingles/vapori.html tecaeromex- steam rockets]</ref> where, due to the lower pressure there, it instantly flashes to high velocity steam, propelling the rocket. The efficiency of [[steam]] as a rocket propellant is relatively low, but it is simple and reasonably safe, and the propellant is cheap and widely available. Most steam rockets have been used for propelling land-based vehicles but it formed the basis of [[Evel Knievel]]'s skycycle, and a small steam rocket was tested in 2004 on board the UK-DMC [[satellite]], as an alternative, with higher performance, to [[cold gas thruster]]s for attitude jets. There are even proposals to use steam rockets for interplanetary transport using either nuclear or solar heating as the power source to vaporize water collected from around the [[solar system]], at system costs that are claimed to be orders of magnitude lower than electrolysis-based hydrogen systems.<ref>[http://www.neofuel.com/ Neofuel-new fuel: Near Earth Object fuel]</ref>
{{-}}
== Uses ==
Rockets or other similar [[reaction engine|reaction devices]] carrying their own propellant must be used when there is no other substance (land, water, or air) or force ([[gravity]], [[magnetism]], [[light]]) that a [[vehicle]] may usefully employ for propulsion, such as in space. In these circumstances, it is necessary to carry all the [[propellant]] to be used.
However, they are also useful in other situations:
[[Image:Xmim-115a.jpg|thumb|A Boeing MIM-115 [[surface-to-air missile]]]]
===Weaponry===
{{main | Missile}}
In many military weapons, rockets are used to propel [[warhead|payload]]s to their targets. A rocket and its payload together are generally referred to as a missile, especially when the weapon has a [[guidance system]].
[[Image:Bumper.jpg|thumb|left|A [[Bumper (rocket)|Bumper]] sounding rocket]]
===Science===
{{Main | Sounding rocket}}
{{See also | Space probe}}
Sounding rockets<ref>{{cite web | last = Marconi | first = Elaine M. | date = [[April 12]] [[2004]] | url = http://www.nasa.gov/missions/research/f_sounding.html | title = What is a Sounding Rocket? | work = Research Aircraft | publisher = NASA | accessdate = October 10 | accessyear = 2006}}</ref> are commonly used to carry instruments that take readings from {{km to mi | 50 | precision = -1}} to {{km to mi | 1500 | precision = -1}} above the surface of the Earth, the altitudes between those reachable by [[weather balloon]]s and satellites.
===Spaceflight===
[[Image:Atlantis taking off on STS-27.jpg|thumb|[[Space Shuttle]] ''Atlantis'' during launch phase, showing both solid (SRBs) and liquid fueled (Shuttle) rocket engines in use.]]
{{main | Spaceflight}}
Due to their high exhaust velocity (Mach ~10+), rockets are particularly useful when very high speeds are required, such as orbital speed (Mach 25+). Spacecraft delivered into orbital trajectories become artificial [[satellites]] which are used for many commercial purposes.
Indeed, rockets remain the only way to launch [[spacecraft]] into orbit and beyond.<ref>[http://spaceflightnow.com/tracking/index.html Spaceflight Now-worldwide launch schedule]</ref> They are also used to rapidly accelerate spacecraft when they change orbits or de-orbit for [[landing]]. Also, a rocket may be used to soften a hard parachute landing immediately before touchdown (see [[Soyuz spacecraft]]).
===Hobby, sport and entertainment===
Hobbyists build and fly [[Model rocket]]s of various types and rockets are used to launch both commercially available [[fireworks]] and professional fireworks displays.
[[Hydrogen peroxide]] rockets are used to power [[jet packs]],<ref>[http://www.transchool.eustis.army.mil/Museum/Jetbelt.htm THE ROCKET BELT]</ref> and have been used to power [[rocket car|cars]] and a rocket car holds the all time [[drag racing]] record.<ref>[http://www.eurodragster.com/news/news1002.asp?Story=oct30#oct30 Sammy Miller]</ref>
==Components of a rocket==
Rockets at minimum have a place to put propellant (such as a [[propellant tank]]), one or more [[rocket engine]]s and [[rocket engine nozzle|nozzle]], [[attitude control|directional stabilization device(s)]] (such as [[fins]], [[attitude jet]]s or engine [[gimbal]]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]].
As well as these components, rockets can have any number of other components, such as wings ([[rocketplane]]s), wheels ([[rocket car]]s), even, in a sense, a person ([[rocket belt]]).
==Noise==
For all but the very smallest sizes, rocket exhaust compared to other engines is generally very noisy. As the [[hypersonic]] exhaust mixes with the ambient air, [[shock wave]]s are formed. The [[sound intensity]] from these shock waves depends on the size of the rocket. The sound intensity of large rockets could potentially kill at close range.<ref name="CR566">[http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660030602_1966030602.pdf NASA CR-566]</ref>
The [[Space Shuttle]] generates over 200 [[dB(A)]] of noise around its base. A [[Saturn V]] launch was detectable on [[seismometer]]s a considerable distance from the launch site.
Generally speaking, noise is most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the plume, as well as reflecting off the ground. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the plume and by deflecting the plume at an angle.<ref name="CR566"/>
For manned rockets various methods are used to reduce the sound intensity for the passengers as much as possible, and typically the placement of the astronauts far away from the rocket engines helps significantly. For the passengers and crew, when a vehicle goes supersonic the sound cuts off as the sound waves are no longer able to keep up with the vehicle.<ref name="CR566"/>
== Physics ==
===Operation===
{{main|Rocket engine}}
[[Image:Motor foguete.svg|thumb|right]]
In all rockets, the exhaust is formed from [[propellant]]s carried within the rocket prior to use.<ref name="RPE7">[Rocket Propulsion Elements - 7th edition, chapter 1]</ref> Rocket thrust is due to the rocket engine, which propels the rocket forwards by exhausting the propellant rearwards at extreme high speed. <!-- We avoid duplicating too much material covered by rocket engine article, but if it refers to the performance of the vehicle, it's appropriate to have it here -->
[[Image:rocketThrust.svg|thumb|right|Rocket thrust is caused by pressures acting on the combustion chamber and nozzle]]
In a closed chamber, the pressures are equal in each direction and no acceleration occurs. If an opening is provided at the bottom of the chamber then the pressure is no longer acting on that side. The remaining pressures give a resultant thrust on the side opposite the opening; as well as permitting exhaust to escape. Using a nozzle increases the forces further, in fact multiplies the thrust as a function of the area ratio of the nozzle, since the pressures also act on the nozzle. As a side effect the pressures act on the exhaust in the opposite direction and accelerate this to very high speeds (in accordance with [[Newton's Third Law]]).<ref name="RPE7"/>
If propellant gas is continuously added to the chamber then this disequilibrium of pressures can be maintained for as long as propellant remains.<ref name="RPE7"/>
It turns out (from [[conservation of momentum]]) that the speed of the exhaust of a rocket determines how much momentum increase is created for a given amount of propellant, and this is termed a rocket's ''[[specific impulse]]''.<ref name="RPE7"/> Because a rocket, propellant and exhaust in flight, away from any external perturbations, may be usefully considered as a closed system, then the total momentum is constant at all times. Therefore the faster the net speed of the exhaust is in one direction the greater the speed of the rocket itself in the opposite direction can become, and even more so because the rocket mass is typically far lower than the final total exhaust mass.
As the remaining propellant decreases, the vehicle's becomes lighter and acceleration tends to increase until eventually it runs out of propellant, and this means that much of the speed change occurs towards the end of the burn when the vehicle is much lighter.<ref name="RPE7"/>
===Forces on a rocket in flight===
[[Image:Rktfor.gif|thumb|right|Forces on a rocket in flight]]
The general study of the forces on a rocket or other spacecraft is called [[astrodynamics]].
Flying rockets are primarily affected by the following:<ref>[http://www.grc.nasa.gov/WWW/K-12/VirtualAero/BottleRocket/airplane/rktfor.html NASA- Four forces on a model rocket]</ref>
*[[Thrust]] from the engine(s)
*[[Gravity]] from [[celestial bodies]]
*[[Drag (physics)|Drag]] if moving in the atmosphere
*[[Lift (force)| Lift]]; usually relatively small effect except for [[rocket-powered aircraft]]
In addition, the [[centrifugal force (fictitious)|inertia/centrifugal pseudo-force]] can be significant due to the path of the rocket around the center of a celestial body; when high enough speeds in the right direction and altitude are achieved a stable [[orbit]] or [[escape velocity]] is obtained.
During a rocket launch, there is a point of maximum aerodynamic drag called [[Max Q]]. This determines the minimum aerodynamic strength of the vehicle.
These forces, with a stabilizing tail present will, unless deliberate control efforts are made, to naturally cause the vehicle to follow a trajectory termed a [[gravity turn]], and this trajectory is often used at least during the initial part of a [[rocket launch|launch]]. This means that the vehicle can maintain low or even zero [[angle of attack]]. This minimizes transverse [[Stress (physics)|stress]] on the launch vehicle; allowing for a weaker, and thus lighter, launch vehicle.<ref name=space-sourcebook>{{Cite book | last = Glasstone | first = Samuel | title = Sourcebook on the Space Sciences | publisher = D. Van Nostrand Company, Inc | date = 1965 | pages = 209 or §4.97 | url = http://books.google.com/books?id=K6k0AAAAMAAJ&q=gravity+turn&dq=gravity+turn&pgis=1}}</ref><ref name=thesis>{{Cite journal | first = David W. | last = Callaway | title = Coplanar Air Launch with Gravity-Turn Launch Trajectories | journal = Masters Thesis | date = March 2004 | url = https://research.maxwell.af.mil/papers/ay2004/afit/AFIT-GAE-ENY-04-M04.pdf}}</ref>
[[Image:NozzleExpansion.svg|thumb|right|275px|Due to the supersonic nature of the exhaust jet the exit pressure can be different to atmospheric pressure. Nozzles are said to be underexpanded (higher than ambient pressure), ambient or overexpanded (below ambient pressure). If under or overexpanded then loss of efficiency occurs, grossly overexpanded nozzles lose less efficiency, but the exhaust jet is usually unstable. Rockets become progressively more underexpanded as they gain altitude. Note that almost all rocket engines will be momentarily grossly overexpanded during startup in an atmosphere.<ref>{{cite book|author=Huzel, D. K. and Huang, D. H.|title=NASA SP-125, Design of Liquid Propellant Rocket Engines|edition=2nd Edition|publisher=NASA|year=1971|url=http://ntrs.nasa.gov/search.jsp?Ntt=sp-125&Ntk=all&Ntx=mode+matchall}}</ref>]]
===Net thrust===
The thrust of a rocket is often deliberately varied over a flight, to provide a way to control the airspeed of the vehicle so as to minimize aerodynamic losses but also so as to limit [[g-force|''g''-forces]] that would otherwise occur during the flight as the propellant mass decreases, which could damage the vehicle, crew or payload.
Below is an approximate equation for calculating the gross thrust of a rocket:
:<math>F_n = \dot{m}\;V_{e} + A_{e}(P_{e} - P_{amb})</math><ref>Rocket Propulsion Elements seventh edition eq-2-14</ref>
where:
:<math> \dot{m} =\,</math>propellant flow (kg/s or lb/s)
:<math>V_{e} =\,</math>jet velocity at nozzle exit plane (m/s or s)
:<math>A_{e} =\,</math>flow area at nozzle exit plane (m<sup>2</sup> or ft<sup>2</sup>)
:<math>P_{e} =\,</math>static pressure at nozzle exit plane (Pa or lb/ft<sup>2</sup>)
:<math>P_{amb} =\,</math>ambient (or atmospheric) pressure (Pa or lb/ft<sup>2</sup>)
Since, unlike a jet engine, a conventional rocket motor lacks an air intake, there is no 'ram drag' to deduct from the gross thrust. Consequently the net thrust of a rocket motor is equal to the gross thrust.
The <math>\dot{m}V_{e}\,</math> term represents the momentum thrust, which remains constant at a given throttle setting, whereas the <math>A_{e}(P_{e} - P_{amb})\,</math> term represents the pressure thrust term. At full throttle, the net thrust of a rocket motor improves slightly with increasing altitude, because the reducing atmospheric pressure increases the pressure thrust term.
===Specific impulse===
As can be seen from the thrust equation the effective speed of the exhaust, Ve, has a large impact on the amount of thrust produced from a particular quantity of fuel burnt per second. The thrust-seconds ([[impulse]]) per unit of propellant is called [[Specific impulse|Specific Impulse (Isp) or effective exhaust velocity]] and this is one of the most important figures that describes a rocket's performance.
'''Vacuum Isp'''
Due to the specific impulse varying with pressure, a quantity that is easy to compare and calculate with is useful. Because rockets [[choked flow|choke]] at the throat, and because the supersonic exhaust prevents external pressure influences travelling upstream, it turns out that the pressure at the exit is ideally exactly proportional to the propellant flow <math> \dot{m}</math>, provided the mixture ratios and combustion efficiencies are maintained. It is thus quite usual to rearrange the above equation slightly:
:<math> Fvac = C_f \dot{m} c^*</math><ref>Rocket Propulsion Elements seventh edition eq-3-33</ref>
and so define the ''vacuum Isp'' to be:
:<math>V_{evac} = C_f c^*</math>
Where:
:<math>c^* =\,</math> the speed of sound constant at the throat
:<math>C_f =\,</math> the thrust coefficient constant of the nozzle (typically between 0.8 and 1.9)
And hence:
:<math> F_n = \dot{m} V_{evac} - A_{e} P_{amb}</math>
[[Image:Deltavs.svg|thumb|A map of approximate [[Delta-v]]'s around the solar system between Earth and [[Mars]]<ref>[http://www.pma.caltech.edu/~chirata/deltav.html table of cislunar/mars delta-vs]</ref><ref>[http://www.strout.net/info/science/delta-v/intro.html cislunar delta-vs]</ref>]]
===Delta-v (rocket equation)===
{{main|Tsiolkovsky rocket equation}}
The [[delta-v]] capacity of a rocket is the theoretical total change in velocity that a rocket can achieve without any external interference (without air drag or gravity or other forces).
The delta-v that a rocket vehicle can provide can be calculated from the [[Tsiolkovsky rocket equation]]<ref>[http://www.projectrho.com/rocket/rocket3c.html Choose Your Engine]</ref>:
:<math>\Delta v\ = v_e \ln \frac {m_0} {m_1}</math>
where:
:<math>m_0</math> is the initial total mass, including propellant, in kg (or lb)
:<math>m_1</math> is the final total mass in kg (or lb)
:<math>v_e</math> is the effective exhaust velocity in m/s or (ft/s) or <math>V_e = I_{sp} \cdot g_0</math>
:<math>\Delta v\ </math> is the delta-v in m/s (or ft/s)
Delta-v can also be calculated for a particular manoeuvre; for example the delta-v to launch from the surface of the Earth to [[Low earth orbit]] is about 9.7 km/s, which leaves the vehicle with a sideways speed of about 7.8 km/s at an altitude of around 200 km. In this manoeuvre about 1.9 km/s is lost in air drag, gravity drag and gaining altitude.
[[Image:Rocket mass ratio versus delta-v.png|thumb|left|The Tsiolkovsky rocket equation gives a relationship between the mass ratio and the final velocity in multiples of the exhaust speed]]
===Mass ratios===
Persons not familiar with spaceflight rarely realize that almost all of a rocket's launch mass consists of propellant.<ref>[http://www-istp.gsfc.nasa.gov/stargaze/Srockhis.htm]</ref> Mass ratio is the ratio between the initial fuelled mass and the mass after the 'burn'.<ref>[http://exploration.grc.nasa.gov/education/rocket/rktwtp.html Rocket Mass Ratios]</ref> Everything else being equal, a high mass ratio is desirable for good performance, since it indicates that the rocket is lightweight and hence performs better, for essentially the same reasons that low weight is desirable in sports cars.
Rockets as a group have the highest [[thrust-to-weight ratio]] of any type of engine; and this helps vehicles achieve high [[mass ratio]]s, which improves the performance of flights. The higher this ratio, the less engine mass is needed to be carried and permits the carrying of even more propellant, this enormously improves performance.
Achievable mass ratios are highly dependent on many factors such as propellant type, the design of engine the vehicle uses, structural safety margins and construction techniques.
The best mass ratios are generally achieved with liquid rockets. Liquid propellants generally have densities not dissimilar to water (with the notable exceptions of [[liquid hydrogen]] and liquid [[methane]]), and these types are able to use low pressure tanks and commonly run [[turbopumps]] to force the propellant into the combustion chamber. Low pressure tanks permit much thinner, lighter walls to be used.
Some notable mass fractions are found in the following table (some aircraft are included for comparison purposes):
{{Mass fraction table}}
[[Image:Artistsconcept separation.jpg|thumb|right|Staging involves dropping off unnecessary parts of the rocket to reduce weight]]
===Staging===
{{main|Multistage rocket}}
Often, the required velocity (delta-v) for a mission is unattainable by any single rocket because the [[propellant]], tankage, structure, [[Guidance system|guidance]], valves and engines and so on, take a particular minimum percentage of take-off mass.
The mass ratios that can be achieved with a single set of fixed rocket engines and tankage varies depends on acceleration required, construction materials, tank layout, engine type and propellants used, but for example the first stage of the Saturn V, carrying the weight of the upper stages, was able to achieve a mass ratio of about 10, and achieved a specific impulse of 263 seconds. This gives a delta-v of around 5.9 km/s whereas around 9.4 km/s delta-v is needed to achieve orbit with all losses allowed for.
[[Image:Ap6-68-HC-191.jpg|left|thumb|Apollo 6 while dropping the interstage ring]]
This problem is frequently solved by [[Staging (rocketry)|staging]] — the rocket sheds excess weight (usually empty tankage and associated engines) during launch to reduce its weight and effectively increase its [[mass ratio]]. Staging is either ''serial'' where the rockets light after the previous stage has fallen away, or ''parallel'', where rockets are burning together and then detach when they burn out.<ref>[http://exploration.grc.nasa.gov/education/rocket/rktstage.html Rocket staging]</ref>
Typically, the acceleration of a rocket increases with time (if the thrust stays the same) as the weight of the rocket decreases as propellant is burned. Discontinuities in acceleration will occur when stages burn out, often starting at a lower acceleration with each new stage firing.
[[Image:PropulsiveEfficiency.GIF|left|thumb|Rocket [[propulsive efficiency]] as a function of vehicle speed divided by effective exhaust speed]]
===Energy efficiency===
Rocket launch vehicles take-off with a great deal of flames, noise and drama, and it might seem obvious that they are grievously inefficient. However while they are far from perfect, their energy efficiency is not as bad as might be supposed.
The energy density of rocket propellant is around 1/3 that of conventional hydrocarbon fuels; the bulk of the mass is in the form of (often relatively inexpensive) oxidiser. Nevertheless, at take-off the rocket has a great deal of energy in the form of fuel and oxidiser stored within the vehicle, and it is of course desirable that as much of the energy stored in the propellant ends up as [[kinetic energy|kinetic]] or [[potential energy]] of the body of the rocket as possible.
Energy from the fuel is lost in air drag and [[gravity drag]] and is used to gain altitude. However, much of the lost energy ends up in the exhaust.<ref name="RPE"/>
100% efficiency within the engine (<math>\eta_c</math>) would mean that all of the heat energy of the combustion products is converted into kinetic energy of the jet. [[Heat_Engine#Efficiency|This is not possible]], but the [[rocket engine nozzle|high expansion ratio nozzles]] that can be used with rockets come surprisingly close: when the nozzle expands the gas, the gas is cooled and accelerated, and an energy efficiency of up to 70% can be achieved. Most of the rest is heat energy in the exhaust that is not recovered.<ref name="RPE"/> This compares ''very well'' with other engine designs. The high efficiency is a consequence of the fact that rocket combustion can be performed at very high temperatures and the gas is finally released at much lower temperatures, and so giving good [[Carnot efficiency]].
However, engine efficiency is not the whole story. In common with many [[jet engine|jet-based engines]], but particularly in rockets due to their high and typically fixed exhaust speeds, rocket vehicles are extremely inefficient at low speeds irrespective of the engine efficiency. The problem is that at low speeds, the exhaust carries away a huge amount of [[kinetic energy]] rearward. This phenomenon is termed [[propulsive efficiency]] (<math>\eta_p</math>).<ref name="RPE"/>
However, as speeds rise, the resultant exhaust speed goes down, and the overall vehicle energetic efficiency rises, reaching a peak of around 100% of the engine efficiency when the vehicle is travelling exactly at the same speed that the exhaust is emitted. In this case the exhaust would ideally stop dead in space behind the moving vehicle, taking away zero energy, and from conservation of energy, all the energy would end up in the vehicle. The efficiency then drops off again at even higher speeds as the exhaust ends up travelling forwards behind the vehicle.
From these principles it can be shown that the propulsive efficiency <math>\eta_p</math> for a rocket moving at speed <math>u</math> with an exhaust velocity <math>c</math> is:
:<math>\eta_p= \frac {2 \frac {u} {c}} {1 + ( \frac {u} {c} )^2 }</math><ref name="RPE">Rocket Propulsion elements- seventh edition, pg 37-38</ref>
And the overall energy efficiency <math>\eta</math> is:
:<math>\eta= \eta_p \eta_c</math>
Since the energy ultimately comes from fuel, these joint considerations mean that rockets are mainly useful when a very high speed is required, such as [[ICBM]]s or [[Orbital spaceflight|orbital launch]], and they are rarely if ever used for general aviation. For example, from the equation, with an <math>\eta_c</math> of 0.7, a rocket flying at Mach 0.85 (which most aircraft cruise at) with an exhaust velocity of Mach 10, would have a predicted overall energy efficiency of 5.9%, whereas a conventional, modern, air breathing jet engine achieves closer to 30% or more efficiency. Thus a rocket would need about 5x more energy; and allowing for the ~3x lower specific energy of rocket propellant than conventional air fuel, roughly 15x more mass of propellant would need to be carried for the same journey.
Thus jet engines which have a better match between speed and jet exhaust speed such as [[turbofans]] (in spite of their worse <math>\eta_c</math>) dominate for subsonic and supersonic atmospheric use while rockets work best at hypersonic speeds. On the other hand rockets do also see many short-range ''relatively'' low speed military applications where their low-speed inefficiency is outweighed by their extremely high thrust and hence high accelerations.
== Safety, reliability and accidents ==
{{Main | Space disaster}}[[Image:Challenger explosion.jpg|thumb|right|250px|[[Space Shuttle Challenger]] was torn apart 73 seconds after launch when hot gases escaped the [[SRB]]s]]
Rockets are not inherently highly dangerous. In military usage quite adequate reliability is obtained.
Because of the enormous chemical energy in all useful [[rocket propellant]]s (greater energy per weight than explosives, but lower than [[gasoline]]), accidents can and have happened. The number of people injured or killed is usually small because of the great care typically taken, but this record is not perfect.
== See also ==
<div style="-moz-column-count:2; column-count:2;">
'''Lists'''
* [[List of spaceflights]]
* [[Timeline of rocket and missile technology]]
* [[Chronology of Pakistan's rocket tests]]
* [[List of rockets]]
* [[Sounding rocket]]
* [[Spacecraft propulsion]] - describes many different propulsion systems for spacecraft
'''General rocketry'''
* [[Bipropellant rocket]] - two-part liquid or gaseous fuelled rocket
* [[Tripropellant rocket]] - variable propellant mixes can improve performance
* [[Hot Water Rocket|Hot Water rocket]] - powered by boiling water
* [[Hybrid rocket]] - solid rocket burnt by second fluid propellant
* [[Pulsed Rocket Motors]] - solid rocket that burns in segments
* [[Rocket fuel]]
* [[Rocket launch]]
* [[Rocket launch site]]
* [[Rocket engine nozzles]] - De Laval nozzles
* [[Solid rocket]]
* [[Tsiolkovsky rocket equation]] - equation describing rocket performance
'''Recreational rocketry'''
* [[Model rocket]] - small hobby rocket
* [[High-powered rocket]]
* [[Water rocket]] - toy rocket launched for recreational purposes using water as propellant
* [[Balloon rocket]]
'''Recreational pyrotechnic rocketry'''
* [[Bottle rocket]] - small firework type rocket often launched from bottles
* [[Skyrocket]] - fireworks that typically explode at apogee
'''Weaponry'''
* [[Rocket propelled grenade]] - military use of rockets
* [[Fire Arrow]] - one of the earliest types of rocket
* [[Shin Ki Chon]] Korean variation of the Chinese fire arrow
* [[Katyusha rocket launcher]] - rack mounted rocket
* [[VA-111 Shkval]] - Russian rocket propelled [[supercavitation]] torpedo
'''Rockets for Research'''
* [[Disappearing rocket]] - rocket that disintegrate if fired from the ground for safety reasons
* [[Rocket plane]] - winged aircraft powered by rockets
* [[Rocket sled]] - used for high speeds along ground
* [[Sounding rocket]] - suborbital rocket used for atmospheric and other research
'''Misc'''
* [[Rocket mail]] - an ill-fated attempt to commercialise rocketry
* [[Pulse jet engine]] - an airbreathing jet engine
</div>
{{Portal | Spaceflight | RocketSunIcon.svg}}
== External links ==
{{Commons|rocket}}
; Governing agencies
* [http://ast.faa.gov/ FAA Office of Commercial Space Transportation]
* [http://www.nasa.gov/ National Aeronautics and Space Administration (NASA)]
* [http://www.nar.org/ National Association of Rocketry (USA)]
* [http://www.tripoli.org/ Tripoli Rocketry Association]
* [http://www.ukra.org.uk/ United Kingdom Rocketry Association]
* [http://www.canadianrocketry.org/ Canadian Association of Rocketry]
* [http://www.isro.org/ Indian Space Research Organisation]
; Information sites
* [[Encyclopedia Astronautica]] - [http://www.astronautix.com/lvs/ Rocket and Missile Alphabetical Index]
* Gunter's Space Page - [http://space.skyrocket.de Complete Rocket and Missile Lists]
* [http://www.pwrengineering.com/data.htm Rocketdyne Technical Articles]
*[http://www.relativitycalculator.com/rocket_equations.shtml Relativity Calculator - Learn Tsiolkovsky's rocket equations ]
== Notes ==
*{{cite book |last=Harford |first=James |authorlink= |coauthors= |others= |title=Korolev: How One Man Masterminded the Soviet Drive to Beat America to the Moon |year=1997 |publisher=John Wiley & Sons |location= |id=ISBN 0-471-14853-9 }}
== References ==
{{reflist|2}}
{{Aviation lists}}
[[Category:Rocket-powered aircraft]]
[[Category:Rocketry]]
[[Category:Space launch vehicles|Space launch vehicles]]
[[Category:Traditional Chinese objects]]
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