What is Rocket Science?: Rocket science involves utilising rocket propulsion to transport anything from fireworks to crewed spacecraft.
The core principle of rocketry is based on Isaac Newton’s Third Law of Motion, which has been recognised for more than 300 years. This law states that for every action, there is an equal and opposite reaction. For example, if you push against a wall with force, you will find yourself moving backward.
Similarly, if you were to stand on a skateboard and throw a heavy object away from you with great force (it’s advised not to attempt this), you would move backward in the opposite direction. When you exert force on an object by pushing it forward, the object exerts an equal force back onto you.
In a rocket, the substance that is expelled is the result of fuel combustion. As the fuel burns, it creates gases that are forcefully ejected from the rocket’s rear. This action of pushing out gases causes the rocket itself to move in the direction opposite to the expelled gases, based on the principle of action and reaction.
Is rocket science complex?
A functioning rocket must achieve three key objectives: initiate its launch (initiate movement), counter the force of gravity, and navigate a path. These requirements are grounded in physical laws that have been established since the era of Newton.
Flying rockets in space is simple, but on Earth, we need to beat the pull of our planet’s gravity. That’s why rockets work much better than big guns. In the 1800s, the story writer Jules Verne thought of using a big gun to shoot a space capsule with three people inside, to the Moon.
A cannon must accelerate its payload to the necessary speed to escape Earth’s gravity, known as escape velocity, before it exits the barrel. Once outside, the only forces affecting it are gravity and air resistance, both of which decelerate it.
Verne’s space capsule reaching the necessary speed of 11.2 km/s would exert extreme force on its occupants, potentially causing harm. However, a rocket can achieve this speed more safely by slowly increasing its velocity over a prolonged period, using its fuel supply to ascend gradually and escape Earth’s gravitational pull.
To chart a trajectory (or the path it takes), we rely solely on Newtonian physics, which enables us to predict how the gravitational forces from the Earth, Sun, and Moon will influence the flight path. While other planets also exert gravitational forces, their effects are minimal for a local journey. Additionally, any propulsion manoeuvers from the rocket’s engine are taken into account.
The challenge of successful rocketry lies more in the engineering than the science itself. The complexity of technology within a rocket makes it exceedingly difficult to guarantee that all components will function as intended.
So, rocket science isn’t as complicated as it’s made out to be?
However, understanding the fundamentals of physics isn’t for everyone. In 1920, when American rocketry pioneer Robert H. Goddard proposed that a rocket could travel from Earth to the Moon, The New York Times evidently did not grasp the principles of rocket operation.
The newspaper editorial remarked: “It’s absurd to think that Professor Goddard, holding a position at Clark College and supported by the Smithsonian Institution, is unaware of the basic principles of action and reaction, and the necessity for a medium to push against rather than a vacuum. Obviously, it appears he’s missing the kind of fundamental knowledge that’s routinely taught in high schools.”
To make simple, the editorial from the newspaper essentially criticises Robert H. Goddard’s idea that a rocket could operate in space, which is a vacuum. The criticism is based on a misunderstanding of how rockets work. The editorial suggests that Goddard, despite his prestigious positions at Clark College and the backing of the Smithsonian Institution, lacks understanding of basic physics principles—specifically, the concept of action and reaction (Newton’s third law of motion) and the mistaken belief that rockets need air or another substance to push against to move, which is a principle taught in high schools. In reality, rockets do not need air to push against; they work in space by expelling exhaust gases in one direction to propel themselves in the opposite direction, a principle Goddard understood well but the editorial misrepresented.
The oversight in the editorial was its failure to grasp that a rocket’s propulsion isn’t about pushing against the atmosphere, but rather it is propelled forward by the expulsion of burning fuel from its rear. In 1969, as Apollo 11 was en route to the Moon, the newspaper issued a ‘correction’ but did not offer an apology for its earlier misunderstanding of Newton’s laws of physics or for the damage done to Goddard’s reputation.
How do Rockets Work?
All rockets operate based on the concept of expelling material from their rear to propel themselves forward, although the specific type of material ejected can differ.
The aeolipile, an early invention by Hero of Alexandria in the 1st Century AD, was one of the first machines to use rocket-like propulsion. It worked by shooting steam out of small tubes, which made a metal ball spin around. This device showed how the force of steam could be used to create movement, similar to how modern rockets use gas to move through space.
Most rockets operate by igniting combustible materials, with the intense energy from the burning process creating exhaust gases that propel the rocket forward. Initially, rockets relied on gunpowder for this purpose. However, contemporary rocket designs have evolved to use specific types of solid fuel or gases, such as hydrogen in its liquid form, to increase the fuel capacity and efficiency of the rocket.
Space rockets need to work in space where there is no air, so they have to carry their own oxygen-like substance to help burn fuel. This could be liquid oxygen or other materials.
The latest advancement in rocket technology is called the ion drive or thruster. It’s a type of electric rocket that uses electricity to speed up charged particles, known as ions, and expel them out the back. This action propels the rocket forward. Instead of burning fuel in the traditional way, it uses electrical energy to move, making it more efficient in space.
The aeolipile, an early invention by Hero of Alexandria in the 1st Century AD, was one of the first machines to use rocket-like propulsion. It worked by shooting steam out of small tubes, which made a metal ball spin around. This device showed how the force of steam could be used to create movement, similar to how modern rockets use gas to move through space
Thrusters are mainly used to steer rockets because they can make very accurate adjustments, even though they’re not very strong. However, they have the potential to be the main source of movement for a rocket built specifically for deep space missions. This is because in the vastness of space, where there is no air resistance or gravity from planets and moons, even a small amount of force can move a spacecraft effectively over long distances.
What is the origin of rocket technology?
Before the Greek steam rockets, the very first rockets were made in China for shows with fireworks and as weapons. These Chinese rockets go back to at least the 1300s.
In the 1800s, people in the West started using rockets made of metal as weapons. They were hard to aim accurately, but they were good at scaring enemies and became popular for shooting from ships. This is because rockets don’t push back when fired, unlike guns.
Francis Scott Key was thinking about rockets being used as weapons, which create a bright red light in the sky, when he wrote about the “rockets’ red glare” in the US national anthem.
Rockets were featured in stories about space travel long before they could actually be used for it.
When America started working on rockets in the 1930s, the military thought it sounded too much like a story from a science fiction book. So, the place where they worked on rockets in Pasadena, California was named the Jet Propulsion Laboratory, even though they only focused on rockets and not jets.
The latest advancement in rocket technology is called the ion drive or thruster. It’s a type of electric rocket that uses electricity to speed up charged particles, known as ions, and expel them out the back. This action propels the rocket forward. Instead of burning fuel in the traditional way, it uses electrical energy to move, making it more efficient in space
Jets use air and fuel to create thrust and can operate within the Earth’s atmosphere. Rockets carry their own oxygen, allowing them to work in space. The rocket packs used to help planes take off from short runways were called ‘JATO’ (jet-assisted take-off) to avoid using the word ‘rocket’.
After World War II, the space rockets made by both the USA and the USSR were based on the German V-2 missile. Wernher von Braun, who developed the V-2, wasn’t really interested in the war. He worked on rockets to turn his dream of traveling to space into reality.
After the war, both the USA and USSR used the V-2 design to make their own missiles. The Atlas rockets, which sent the first American astronauts into space, were first made as missiles to travel across continents. The Saturn V rocket, which was part of the Apollo missions, also came from a family of rockets that started with the Redstone missiles and included the Jupiter series.
Can rockets take in oxygen from the air around them?
Space rockets need something like oxygen or hydrogen peroxide to help the fuel burn in space. But when they first take off, they are still passing through the air.
If they could use the oxygen from the air during this part, the rocket wouldn’t need to carry as much weight from the start. This would make it much easier to take off because they could use the oxygen around them while they can. The issue is that it’s very difficult to do technically.
For a rocket using hydrogen and oxygen, like those NASA often uses, the oxygen needs to be squeezed and chilled to about -140°C before it combines with the hydrogen. This mixing needs to happen very quickly, in about 1/100th of a second, and they must also prevent any ice from forming because of moisture in the air.
The SABRE propulsion system, developed by Reaction Engines, a UK-based company, is poised for application in functional rocket engines. It’s specifically designed for integration with the SKYLON spaceplane.
The SABRE propulsion system, developed by Reaction Engines, a UK-based company, is poised for application in functional rocket engines. It’s specifically designed for integration with the SKYLON spaceplane
Why are large rockets designed with several stages?
A major difference between rockets in old space stories and the real ones that took people to space is that the real rockets have several parts that fall off as they go up into the sky from Earth. The concept was first thought of by Konstantin Tsiolkovsky, a Russian schoolteacher and rocket expert, back in 1903.
The reason rockets have different stages is because they need to carry a lot of fuel to break free from Earth’s gravity. Once a fuel tank is empty, it’s just dead weight that makes it harder to move, using up more fuel. So, when a rocket uses up all the fuel in one stage , it gets rid of that part. This makes the rest of the rocket lighter and it doesn’t need as much fuel to keep going up.
Tsiolkovsky was primarily focused on theory, while it was Goddard who built the first functional experimental rockets with multiple stages.
When spacecraft come back to Earth, they slow down using air resistance, wings (like those on the Space Shuttle), and parachutes during re-entry. This is different from many sci-fi spaceships, which typically land gently using rocket power.
Rockets are employed for landing on bodies like the Moon, where there’s no atmosphere and gravity is weak. However, a spacecraft can’t carry enough fuel to achieve a gentle landing on Earth, as the majority of its fuel is consumed during the initial ascent.
Coming back to Earth using rockets would require a way to refuel in space, something that isn’t possible at the moment.
Where have rockets found application?
We know rockets from fireworks and spaceships, but the military has used rocket technology in wars for many years. This includes everything from simple metal tube rockets in the past to today’s advanced missiles and rocket-powered grenades.
Rockets have also been used to save lives, such as in rescue flares, helping to send a line between ships to pull sailors to safety, and in the ejector seats of military aircraft.
The jetpack featured in the James Bond movie “Thunderball” was actually closer to a rocket pack, and rockets have propelled cars and sleds (vehicles designed for sliding over surfaces, typically ice or snow) to achieve record-breaking speeds. For generating a high amount of thrust in a brief time frame, rockets are frequently the optimal choice.
A space elevator is one option instead of rockets. It works by stretching a very long cable from a satellite to the Earth’s surface. A machine would then move up this cable, carrying cargo into space. This idea is appealing because it could be less expensive than rockets and wouldn’t require carrying fuel
Will Rockets Always Be Used?
Ion engines will probably always be useful. However, it would be great if we could find alternatives to rockets. This would help us leave Earth more easily and travel far, like to the outer parts of our Solar System or even to other stars.
A space elevator is one option instead of rockets. It works by stretching a very long cable from a satellite to the Earth’s surface. A machine would then move up this cable, carrying cargo into space. This idea is appealing because it could be less expensive than rockets and wouldn’t require carrying fuel.
Currently, we lack materials with enough strength to construct a space elevator on Earth. The required cable would need to be almost 38,000 kilometers long. For instance, a 28mm thick steel cable capable of holding about 50 tonnes would itself weigh around 115,000 tonnes. However, we possess materials that could potentially be used to build a space elevator on the Moon.
For traveling in deep space, we might be able to use alternatives to rockets like solar sails, which rely on sunlight pressure to speed up a spacecraft, or mass drivers, which act as external engines to propel the spacecraft.
-The writer is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach out to him at: girishlinganna@gmail.com. The views expressed are personal and do not necessarily reflect the views of Raksha Anirveda
