The Evolution of The Rocket Engine
When you witness a rocket like the SpaceX Starship soaring into the sky on a massive column of fire, you are observing the pinnacle of modern science and engineering. Rocket engines are among humanity’s most significant inventions, emerging hundreds or even thousands of years ago and continuously evolving alongside human civilization.
The Origins of Rocket Technology
The history of rocket technology dates back to the 9th century in China when alchemists were experimenting with compounds like saltpeter, sulfur, and charcoal, hoping to create gold or an elixir of immortality. Instead, they accidentally discovered gunpowder—the first rocket fuel in history.
During the Song Dynasty (around 1000 AD), gunpowder was used to create “fire arrows”—bamboo tubes filled with gunpowder attached to arrowheads. When ignited, these arrows flew farther than any bow of the time. A significant advancement occurred when Chinese engineers discovered that sealing one end of the bamboo tube while leaving the other open allowed them to control the rocket’s flight direction. This principle reflects Newton’s Third Law, which states that every action has an equal and opposite reaction.
During the Ming Dynasty (14th–17th centuries), rocket technology reached new heights with multi-stage systems. One of the most impressive designs was the “Huo Long Shui Jian” (Fire Dragon Water Arrow)—a rocket about 1.5 meters tall with a carved dragon head at the front. This rocket had two propulsion stages: after the primary engine burned out, the second engine automatically ignited, extending its range and improving accuracy. This design closely resembles modern multi-stage rockets like Russia’s Soyuz. However, the biggest limitation at the time was fuel—gunpowder was not efficient or stable enough to propel rockets to great altitudes.
Breakthroughs in the 20th Century
Rocket technology took a major leap forward in 1903 when Russian scientist Konstantin Tsiolkovsky published a groundbreaking rocket equation. He demonstrated that to reach space, rockets needed liquid fuel instead of gunpowder. His design proposed using liquid hydrogen and liquid oxygen—highly efficient fuels that required extreme cooling (-180°C).
In 1926, American scientist Robert Goddard successfully launched the first liquid-fueled rocket in Auburn, Massachusetts. Though it flew for only 2.5 seconds and reached a height of 12.5 meters, it marked a significant milestone. Goddard continued to refine rocket engines by inventing regenerative cooling, which circulated fuel around the engine walls to prevent overheating. He was also the first to use fuel pumps to maintain stable pressure, making combustion more efficient. By 1935, his rockets could travel over 2,300 meters.
However, Goddard was not fully recognized during his lifetime, and his work only gained true value when the U.S. and German rocket programs advanced later.
World War II and the Birth of the V-2
In Germany, Hermann Oberth’s 1923 book The Rocket into Planetary Space inspired a new generation of engineers, including Wernher von Braun. Von Braun pioneered the development of more powerful rocket engines using liquid oxygen and ethanol as fuel.
In 1944, von Braun successfully developed the V-2 rocket—the first ballistic missile in history. With 25 tons of thrust, it could travel at five times the speed of sound and reach altitudes over 200 kilometers, making it the first human-made object to enter space. The V-2’s engine used advanced fuel injection technology with 18 separate nozzles, ensuring stable combustion. However, its biggest drawback was ethanol production—each launch required 30 tons of potatoes to distill enough fuel.
After World War II, both the Soviet Union and the United States scrambled to acquire German rocket technology. The Soviets obtained V-2 designs, while the U.S. recruited von Braun and his team of engineers.
The Space Race and the Evolution of Modern Engines
By the late 1950s, the Soviet Union had improved V-2 technology to develop the R-7 rocket, the first capable of putting a satellite into orbit. Soviet engineer Valentin Glushko replaced ethanol with kerosene, making production easier. He also designed the RD-107 and RD-108 engines with multiple small combustion chambers instead of a single large one, improving stability.
To control the rocket, Glushko invented vernier thrusters—small engines that could swivel to adjust flight direction. He also implemented the gas generator cycle, which improved fuel pump efficiency but wasted about 3% of the fuel.
In the U.S., NASA struggled to catch up with the Soviets, as it still relied on outdated V-2 designs. However, as the space race intensified, they turned to von Braun to develop a rocket capable of sending humans to the Moon.
Von Braun and his team created Saturn V, the most powerful rocket ever built. Its F-1 engine was the largest single-chamber rocket engine ever flown, with a combustion chamber big enough to fit a Jeep inside. This engine enabled the successful Apollo missions, landing humans on the Moon in 1969.
