Editing Rocket engine (section)

===The era of liquid-fuel rocket engines===
Goddard began to use liquid propellants in 1921, and in 1926 became the first to launch a liquid-fuelled rocket. Goddard pioneered the use of the De Laval nozzle, lightweight propellant tanks, small light turbopumps, thrust vectoring, the smoothly-throttled liquid fuel engine, regenerative cooling, and curtain cooling.<ref name=Sutton/>{{rp|247–266}}

During the late 1930s, German scientists, such as [[Wernher von Braun]] and [[Hellmuth Walter]], investigated installing liquid-fuelled rockets in military aircraft ([[Heinkel He 112]], [[Heinkel He 111|He 111]], [[Heinkel He 176|He 176]] and [[Messerschmitt Me 163]]).<ref>{{cite book|author=Lutz Warsitz|title=The First Jet Pilot – The Story of German Test Pilot Erich Warsitz|publisher=Pen and Sword Ltd.|date=2009|isbn=978-1-84415-818-8}} Includes von Braun's and Hellmuth Walter's experiments with rocket aircraft. [http://www.pen-and-sword.co.uk/?product_id=1762 English edition.]</ref>

The turbopump was employed by German scientists in World War II. Until then cooling the nozzle had been problematic, and the [[V-2 rocket|A4]] ballistic missile used dilute alcohol for the fuel, which reduced the combustion temperature sufficiently.

[[Staged combustion cycle (rocket)|Staged combustion]] (''Замкнутая схема'') was first proposed by [[Aleksei Mihailovich Isaev|Alexey Isaev]] in 1949. The first staged combustion engine was the S1.5400 used in the Soviet planetary rocket, designed by Melnikov, a former assistant to Isaev.<ref name=Sutton>{{cite book|last=Sutton|first=George P.|title=History of Liquid Propellant Rocket Engines|date=2005|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Virginia}}</ref> About the same time (1959), [[Nikolai Dmitriyevich Kuznetsov|Nikolai Kuznetsov]] began work on the closed cycle engine [[NK-9]] for Korolev's orbital ICBM, GR-1. Kuznetsov later evolved that design into the [[NK-15]] and [[NK-33]] engines for the unsuccessful Lunar [[N1 rocket]].

In the West, the first laboratory staged-combustion test engine was built in Germany in 1963, by [[Ludwig Boelkow]].

Liquid hydrogen engines were first successfully developed in America: the [[RL-10]] engine first flew in 1962. Its successor, the [[Rocketdyne J-2]], was used in the [[Apollo program]]'s [[Saturn V]] rocket to send humans to the Moon. The high specific impulse and low density of liquid hydrogen lowered the upper stage mass and the overall size and cost of the vehicle.

The record for most engines on one rocket flight is 44, set by NASA in 2016 on a [[Black Brant (rocket)|Black Brant]].<ref>{{Cite web | url=https://www.space.com/33810-nasa-world-record-most-rocket-engines.html |title = NASA and Navy Set World Record for Most Engines in One Rocket Flight|website = [[Space.com]]|date = 19 August 2016}}</ref>