Editing Opel (section)

===1920–1939===
[[File:Opel RAK1 2.jpg|thumb|Opel RAK.1 – world's first public flight of a manned rocket-powered plane on 30 September 1929]]
[[File:Opel Admiral Cabriolet, Bauzeit 1937-1939 (08.07.2007).jpg|thumb|[[Opel Admiral]] convertible (1937–1939)]]
[[File:1939 Opel Kapitän, Owner Arild Nilssen who, as his lady companion wear matching attire cropped to highlight the car.jpg|thumb|[[Opel Kapitän]] (1938–1940)]]
In the early 1920s, Opel became the first German car manufacturer to build automobiles with a mass-production assembly line. In 1924, they used their assembly line to produce a new open two-seater called the [[Opel Laubfrosch|''Laubfrosch'' (Tree frog)]]. The Laubfrosch was finished exclusively in green lacquer. The car sold for an expensive 3,900&nbsp;marks (expensive considering the less expensive manufacturing process), but by the 1930s, this type of vehicle would cost a mere 1,930 marks – due in part to the assembly line, but also due to the skyrocketing demand for cars. Adam Opel led the way for motorised transportation to become not just a means for the rich, but also a reliable way for people of all classes to travel.

Opel had a 37.5% market share in Germany and was the country's largest automobile exporter in 1928. The "Regent" – Opel's first eight-cylinder car – was offered. The RAK 1 and RAK 2 rocket-propelled cars made sensational record-breaking runs.

Opel as a company and its co-owner [[Fritz von Opel]], grandson of Adam Opel, were instrumental in popularizing rocket propulsion for vehicles and have an important place in the history of spaceflight and rocket technology. In the 1920s, Fritz von Opel initiated together with [[Max Valier]], co-founder of the "Verein für Raumschiffahrt", the world's first rocket program, [[Opel-RAK]], leading to speed records for automobiles, rail vehicles and the first manned rocket-powered flight in September 1929.<ref>{{cite web |url=https://www.airforcemag.com/article/0904rocket/ |first=Walter J. |last=Boyne |title=The Rocket Men |work=Air Force Magazine |date=1 September 2004 |access-date=19 July 2022}}</ref> Months earlier in 1928, one of his rocket-powered prototypes, the Opel RAK2, piloted by von Opel himself at the AVUS speedway in Berlin, reached a record speed of {{cvt|238|kph}} in front of 3,000 spectators and world media representatives, including [[Fritz Lang]], director of ''[[Metropolis (1927 film)|Metropolis]]'' and ''[[Woman in the Moon]]'', world boxing champion [[Max Schmeling]], and many other sports and show business celebrities. A world speed record for rail vehicles was reached with RAK3 at a top speed of {{cvt|256|kph}}.<ref>{{cite web|url=https://www.opelpost.com/05/2018/opel-sounds-in-the-era-of-rockets/|title = Opel Sounds in the Era of Rockets|date = 23 May 2018}}</ref> After these successes, von Opel piloted the world's first public rocket-powered flight using [[Opel RAK.1]], a rocket plane designed by [[Julius Hatry]].<ref>{{cite AV media |title=Das RAK-Protokoll |url=https://opel-tv-footage.com/v/The%20RAK%20Protocoll?p=4&c=86&l=1}} a 25-minute documentary on the Opel RAK program</ref> World media reported these events, including Universal Newsreel in the US, causing "Raketen-Rummel" or "Rocket Rumble" immense global public excitement, particularly in Germany, where, among others, [[Wernher von Braun]] was highly influenced.<ref>{{cite web |url=https://www.airspacemag.com/daily-planet/century-elon-musk-there-was-fritz-von-opel-180977634/ |first=Frank H. |last=Winter |title=A Century Before Elon Musk, There Was Fritz von Opel |work=Air & Space Magazine |date=30 April 2021 |access-date=19 July 2022}}</ref>

[[File:Opel RAK liquid-fuel rocket plane Friedrich Sander.jpg|thumb|Friedrich Sander, Opel RAK technician August Becker and Opel employee Karl Treber (from right to left) in front of liquid-fuel rocket-plane prototype while test operation at Opel Rennbahn in Rüsselsheim]]Opel RAK became enthralled with liquid propulsion, building and testing them in the late 1920s in Rüsselsheim. According to [[Max Valier]]'s account, Opel RAK rocket designer, [[Friedrich Wilhelm Sander]] launched two liquid-fuel rockets at Opel Rennbahn in [[Rüsselsheim]] on 10 and 12 April 1929. These Opel RAK rockets were the first European, and after Goddard, the world's second, liquid-fuel rockets in history. In his book ''Raketenfahrt'' Valier describes the size of the rockets as of {{cvt|21|cm}} in diameter and with a length of {{cvt|74|cm}}, weighing {{cvt|7|kg}} empty and {{cvt|16|kg}} with fuel. The maximum thrust was 45 to 50 kp, with a total burning time of 132 seconds. These properties indicate a gas pressure pumping. The first missile rose so quickly that Sander lost sight of it. Two days later, a second unit was ready to go, Sander tied a {{convert|4000|m|adj=on|sp=us}}-long rope to the rocket. After {{cvt|2000|m}} of rope had been unwound, the line broke, and this rocket also disappeared in the area, probably near the Opel proving ground and racetrack in Rüsselsheim, the "Rennbahn". Sander and Opel also worked on an innovative liquid-propellant rocket engine for an anticipated flight across the English Channel. By May 1929, the engine produced a thrust of 200&nbsp;kg (440&nbsp;lb.) "for longer than fifteen minutes, and in July 1929, the Opel RAK collaborators were able to attain powered phases of more than thirty minutes for thrusts of 300 kg (660-lb.) at Opel's works in Rüsselsheim," again according to Max Valier's account.

The [[Great Depression]] led to an end of the Opel-RAK program, but Max Valier continued the efforts. After switching from solid-fuel to liquid-fuel rockets, he died while testing and is considered the first fatality of the dawning space age. Sander's technology was confiscated by the German military in 1935. He was forced to sell his company and was imprisoned for treason. He died in 1938.

In March 1929, General Motors (GM), impressed by Opel's modern production facilities, bought 80% of the company. The Opel family gained $33.3&nbsp;million from the transaction. Subsequently, during 1935, a second factory was built at [[Opelwerk Brandenburg|Brandenburg]] for the production of "[[Opel Blitz|Blitz]]" light trucks. In 1929 Opel licensed the design of the radical [[Neander (motorcycle)|Neander motorcycle]] and produced it as the Opel Motoclub in 1929 and 1930, using Küchen, [[J.A.P.]], and [[Motosacoche]] engines. [[Fritz von Opel]] attached solid-fuel rockets to his Motoclub in a publicity stunt, riding the rocket-boosted motorcycle at the [[Avus]] racetrack.<ref>'Ernst Neumann-Neander und seine Motorrädder', Trapp, 1996, Heel AG, Schindellegi Schweiz. {{ISBN|3-89365-546-8}}</ref>

After acquiring the remaining shares in 1931, General Motors had full ownership of Adam Opel AG and organized it as a wholly owned subsidiary. In 1935, Opel became the first German car manufacturer to produce over 100,000 vehicles annually. This was because of the popularity of the [[Opel 1,2 Liter|Opel P4]] model. The sales price was 1,650&nbsp;marks and the car had a {{convert|23|PS|kW|lk=on|abbr=on}} 1.1&nbsp;L four-cylinder engine achieving a top speed of {{convert|85|km/h|mph|abbr=on}}.
[[File:Bundesarchiv Bild 183-2007-0910-500, Brandenburg, Lkw-Produktion.jpg|thumb|upright|[[Opel Blitz]] assembly at the [[Opelwerk Brandenburg|Brandenburg plant]], 1936]]
Opel also produced the first mass-production vehicle in Germany with a [[Unibody|self-supporting ("unibody")]] all-steel body, closely following the 1934 [[Citroën Traction Avant]]. This was one of the most important innovations in automotive history.<ref>{{cite book |last1=Nieuwenhuis |first1=Paul |first2=Peter E. |last2=Wells |page=109 |title=The Automotive Industry and the Environment |edition=First |publisher=Woodhead Publishing |date=8 August 2003 |isbn=978-1855737136 }}</ref> Launched in 1935, the [[Opel Olympia|Olympia]] was light and its aerodynamics enhanced performance and fuel economy.

The 1930s was a decade of growth, and by 1937, with 130,267 cars produced. Opel's Rüsselsheim facility was Europe's top in terms of vehicle production, and ranking seventh worldwide.<ref name=OpellautMichaels>{{cite news|url= http://www.zeit.de/1964/08/der-grosse-sprung-nach-vorn/komplettansicht |title="...Mit einer Produktion von 130 267 Fahrzeugen waren sie im Jahre 1937 die größte Automobilfabrik Europas und die siebtgrößte der Welt.|work=Der große Sprung nach vorn: Kann Opel Deutschlands größter Autolieferant werden? |date=21 February 1964 |last=Michaels |first=Heinz |publisher=Die Zeit (online)|access-date=13 September 2015}}</ref>

1938 saw the presentation of the highly successful [[Opel Kapitän|Kapitän]]. With a 2.5&nbsp;L six-cylinder engine, all-steel body, front independent suspension, hydraulic shock absorbers, hot-water heating (with electric blower), and central speedometer. 25,374 Kapitäns were made before the intensification of [[World War II]] brought automotive manufacturing to a temporary stop in the autumn of 1940, by order of the government.

[[File:Bundesarchiv Bild 101I-303-0554-24, Italien, Soldaten auf LKW Opel-Blitz.jpg|thumb|Military Opel Blitz in Italy (1944)]]