1. Why Rockets Can Move Without Air to Push Against
Think about a balloon. When you let go of an inflated balloon, the air inside rushes out, and the balloon flies in the opposite direction. This happens because of the "law of action and reaction." When you push something backward, the reaction pushes you forward.
Rockets work on this same principle. Inside a rocket, fuel is burned to create hot gas. This gas is blasted out the back with great force. The reaction to this backward push drives the rocket forward. Unlike airplane engines, rockets do not need to push against the surrounding air. This is why they can travel through the vacuum of space [1].
2. The Fire Arrow: China’s Early Fire Arrows
An early predecessor of the modern rocket was a weapon called the “fire arrow” (huojian), which appeared in China around the year 1000. Records show that these arrows, propelled by gunpowder, were used in battle against Mongol forces as early as 1232 [1].
This technology eventually traveled from China to India and then to Britain. In the early 19th century, William Congreve developed these ideas into military weapons known as Congreve rockets. They were used in the Battle of Baltimore in 1814. The sight of these rockets is even mentioned in the lyrics of the US national anthem, "The Star-Spangled Banner" [1].
3. Robert Goddard's 1926 Liquid-Fueled Rocket and the Mockery It Faced
On March 16, 1926, American inventor Robert Goddard successfully launched the world’s first liquid-fueled rocket. It flew for only 2.5 seconds and reached a height of about 12 meters (40 feet) [2].
However, in 1920, the New York Times had published an article mocking Goddard’s research. The paper claimed he did not understand basic physical laws. Forty-nine years later, on July 17, 1969, the day after Apollo 11 was launched toward the Moon, the same newspaper published a correction. Under the headline "Correction," the paper admitted its own error regarding Goddard’s work [2].
4. How How the V-2 Rocket Was Used in World War II
During World War II, Germany developed a weapon called the V2 rocket. A young researcher named Wernher von Braun played a central role in its development. The V2 was used to attack many cities, causing significant damage.
On June 20, 1944, one V2 rocket launched during a test flight exceeded an altitude of 100 kilometers (62 miles). This boundary, known as the Kármán line, is considered the edge of space. This event marked the first time a human-made object reached space. A technology developed for war unintentionally opened the door to space exploration [3].
5. The Space Race Between the US and the Soviet Union
On October 4, 1957, the Soviet Union (now Russia) successfully launched the world’s first artificial satellite, Sputnik 1, into space. It was a spherical satellite weighing about 84 kilograms (185 pounds) that orbited the Earth while sending out radio waves [4].
Shocked by this achievement, the United States accelerated its own space program. In 1969, the Apollo 11 mission successfully sent humans to the Moon for the first time. This era of intense rivalry between the Soviet Union and the United States is known as the Space Race.
6. How Modern Rockets Are Reused
In the past, rockets were typically disposable. Once a rocket went to space, it was finished, much like a firework that cannot be used again.
However, on December 22, 2015, the American company SpaceX successfully landed the first stage of a launch rocket on a landing pad [5]. If the same rocket can be used many times, it could significantly reduce the cost of space travel.
7. How to Build a Water Rocket Using the Same Principle
Building a real rocket at home is not realistic, but you can launch a "water rocket" that uses the same principle. Water rockets are widely used in school classes and science projects.
A common design uses a 1.5-liter plastic bottle. You fill it about one-third with water, set it on a special launcher, and pump in air. The pressurized air forces the water out the back with speed, and the reaction pushes the rocket forward [6]. This is exactly the same action-and-reaction mechanism explained in the first section.
Safety Note: Launching a water rocket should always be done with an adult in a large, empty area. Never look into the nozzle while pumping air into the bottle. This is the basic rule for launching safely.
8. Everyday Ways to Feel the Reaction Force Yourself
If you want to learn more, start by feeling the "reaction" with everyday objects.
Blow up a balloon and let it go. Observe which direction it flies. You can also look for water rocket events or science classes near you. Ask an adult to help you find local workshops or science museums that offer these activities.
Safety Note: Ask an adult whether a local science museum or community center is offering a hands-on workshop.
Writing down one word that interests you can be a good starting point for further research. For example, asking "What else did Goddard invent?" is a great question to explore.