Editing Gravity assist (section)

==Historical origins==
In his paper "To Those Who Will Be Reading in Order to Build" ({{lang|ru|"Тем, кто будет читать, чтобы строить"}}),<ref>Kondratyuk's paper is included in the book: Mel'kumov, T. M., ed., ''Pionery Raketnoy Tekhniki'' [Pioneers of Rocketry: Selected Papers] (Moscow, U.S.S.R.: Institute for the History of Natural Science and Technology, Academy of Sciences of the USSR, 1964). An English translation of Kondratyuk's paper was made by NASA. See: NASA Technical Translation F-9285, pages 15–56 (1 November 1965).</ref> published in 1938 but dated 1918–1919,{{efn|In 1938, when Kondratyuk submitted his manuscript "To whoever will read in order to build" for publication, he dated the manuscript 1918–1919, although it was apparent that the manuscript had been revised at various times. See page 49 of NASA Technical Translation F-9285 (1 November 1965).}} [[Yuri Kondratyuk]] suggested that a spacecraft traveling between two planets could be accelerated at the beginning and end of its trajectory by using the gravity of the two planets' moons. The portion of his manuscript considering gravity-assists received no later development and was not published until the 1960s.<ref name="urlib.net">{{cite journal |last1=Negri |first1=Rodolfo Batista |last2=Prado |first2=Antônio Fernando Bertachini de Alme |title=A historical review of the theory of gravity-assists in the pre-spaceflight era |journal=Journal of the Brazilian Society of Mechanical Sciences and Engineering |date=14 July 2020 |volume=42 |issue=8 |doi=10.1007/s40430-020-02489-x|s2cid=220510617 |url=http://urlib.net/8JMKD3MGP3W34R/42T4NAH |doi-access=free }}</ref> In his 1925 paper "Problems of Flight by Jet Propulsion: Interplanetary Flights" ({{lang|ru|"Проблема полета при помощи реактивных аппаратов: межпланетные полеты"}}),<ref>Zander's 1925 paper, "Problems of Flight by Jet Propulsion: Interplanetary Flights" was translated by NASA. See NASA Technical Translation F-147 (1964); specifically, Section 7: Flight Around a Planet's Satellite for Accelerating or Decelerating Spaceship, pages 290–292.</ref> [[Friedrich Zander]] showed a deep understanding of the physics behind the concept of gravity assist and its potential for the interplanetary exploration of the [[Solar System]].<ref name="urlib.net" />

Italian engineer [[Gaetano Crocco]] was first to calculate an interplanetary journey considering multiple gravity-assists in 1956.<ref name="urlib.net" />

The gravity assist maneuver was first used in 1959 when the Soviet probe [[Luna 3]] photographed the far side of the Moon. The maneuver relied on research performed under the direction of [[Mstislav Keldysh]] at the [[Keldysh Institute of Applied Mathematics]].<ref>{{cite web |last1=Eneev |first1=T. |last2=Akim |first2=E. |url=http://www.keldysh.ru/events/fly |title=Mstislav Keldysh. Mechanics of the Space Flight |publisher=Keldysh Institute of Applied Mathematics |language=ru }}</ref><ref>{{cite journal |title=Specific problems of a flight to the moon |journal=[[Physics-Uspekhi]] |first=Vsevolod Alexandrovich |last=Egorov |volume=63 |issue=9 |pages=73–117 |date=September 1957 |doi=10.3367/UFNr.0063.195709f.0073 |doi-access=free }}</ref><ref>{{cite book |url=https://books.google.com/books?id=s8FRVu0blhgC&pg=PA146 |title=Essential Spaceflight Dynamics and Magnetospherics |publisher=[[Kluwer Academic]] |location=[[Dordrecht]], Netherlands |first1=Boris V. |last1=Rauschenbakh |first2=Michael Yu. |last2=Ovchinnikov |first3=Susan M. P. |last3=McKenna-Lawlor |author3-link=Susan McKenna-Lawlor |pages=146–147 |year=2003 |isbn=0-306-48027-1}}</ref><ref>{{cite web |last=Berger |first=Eric |title=All Hail Luna 3, Rightful King of 1950s Space Missions |url=https://arstechnica.com/science/2019/10/all-hail-luna-3-rightful-king-of-1950s-space-missions/ |website=Ars Technica |date=4 October 2019 |access-date=13 October 2023 }}</ref>

In 1961, [[Michael Minovitch]], [[UCLA]] graduate student who worked at NASA's [[Jet Propulsion Laboratory]] (JPL), developed a gravity assist technique, that would later be used for the [[Gary Flandro]]'s [[Planetary Grand Tour]] idea.<ref>{{cite web |title=The Maths That Made Voyager Possible |url=https://www.bbc.com/news/science-environment-20033940 |website=BBC News |date=22 October 2012}}</ref><ref>{{cite magazine |last=Portree |first=David S. F. |title=The Challenge of the Planets, Part Three: Gravity |url=https://www.wired.com/2015/01/challenge-planets-part-three-gravity/ |magazine=Wired |access-date=5 December 2022 }}</ref>

During the summer of 1964 at the NASA JPL, Gary Flandro was assigned the task of studying techniques for exploring the outer planets of the Solar System.  In this study he discovered the rare alignment of the outer planets (Jupiter, Saturn, Uranus, and Neptune) and conceived the Planetary Grand Tour multi-planet mission utilizing gravity assist to reduce mission duration from forty years to less than ten.<ref>{{cite web |last=Flandro |first=Gary |title=Fast Reconnaissance Missions to the Outer Solar System Using Energy Derived from the Gravitational Field of Jupiter |url=http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf |website=GravityAssist.com |access-date=6 January 2024 }}<!--Research carried out under NASA-JPL Contract #7-100--></ref>