It’s Rocket Science: Understand basics about rocket technologies
Everything you need to know about rockets if you're investing in space or launching a space startup!
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Space rockets are among the most sophisticated technical devices in the world. Rocket technology has provided mankind with access to space.It is fascinating how military technology, initially serving other purposes, eventually opened up possibilities for exploring new worlds and utilizing peaceful services.
In this article, we will discuss various types of rockets, their components, their main complexities, and the prospects for future rocket development.
Rocket embryos
Most historians attribute the origins of rockets to the Han Dynasty in China (206 B.C. – 220 A.D.) when gunpowder was discovered and first used for entertainment purposes. Fireworks served as the prototypes for the first solid rockets, employing the principle of jet propulsion, which is still used in all modern rockets.
This principle was later described theoretically in the 20th century by scientists such as Konstantin Tsiolkovsky, Robert Goddard, and Hermann Oberth. The principle of reactive motion is based on the movement of a body due to the expulsion of particles from it. In rockets, the combustion components of the fuel are expelled from the nozzle at high speed, causing the rocket to fly in the opposite direction according to the momentum conservation law. Similarly, a balloon flies when inflated with air and released—the balloon moves in one direction, while the pressurized air escapes in another.
This principle was also applied to military missiles. The V2 (German: Vergeltungswaffe 2, lit. 'Vengeance Weapon 2'), technically named Aggregat 4 (A4), became the world's first long-range guided ballistic missile. Intended as Nazi Germany's secret weapon to win World War II, the V2 was launched in large numbers despite its poor accuracy and short range, resulting in significant damage.
After the war ended, scientists led by Wernher Von Braun relocated to the United States, while the rocket samples were sent to the Soviet Union, marking the beginning of the space age. The task for scientists (Von Braun in the USA and Sergei Korolev in the USSR) was initially to replicate the V-2 and subsequently expand on its successes. The USSR then developed the R-7 rocket, the first intercontinental ballistic missile capable of delivering 'cargo' from the USSR to the USA. This rocket launched the first satellite in 1957, and in 1961, after another stage was added, Gagarin ventured into space. Concurrently, Wernher Von Braun advanced his space systems, leading to Alan Shepard becoming the first American in space, and in 1969, the States reached the Moon. The space age had officially begun, remarkably triggered by military technology and the Cold War.
Fundamental questions: what is a rocket and why is it needed?
Let's return to rockets. The primary purpose of a rocket is to transport a payload from one point to another at a specified speed, regardless of whether the cargo is military, a satellite, or a vehicle carrying people. Achieving a specific velocity is necessary to place a spacecraft into orbit, a topic we explore further in this article.
For a spacecraft to overcome the Earth's gravity and begin to revolve around the Earth, it needs an escape velocity of 7.9 km/sec or 28,000 km/h. With this speed, it is possible to fly around the Earth in 1.5 hours.
Multi-stage rockets… Why?
The primary task is to accelerate the vehicle to escape velocity. The rocket consists of several stages that operate sequentially, with only the payload reaching space. Why is this necessary? This design is crucial due to the initial-to-final mass ratio of the rocket.
The more fuel placed in the rocket's tanks and the lighter the empty rocket, the greater its final velocity after fuel combustion, enhancing its efficiency.
Moreover, once a portion of the fuel is consumed, such as half a tank, it becomes a redundant part of the design with no function. Consequently, spent stages are discarded and deorbited to predetermined areas or the ocean, akin to lightening a backpack of potatoes by discarding one at a time along a journey. The closer to the destination, the lighter the backpack becomes, easing its transport.
On the other hand, using too many stages is also inefficient - it will increase the number of engines, which are both heavy and expensive.
Accelerating a spacecraft to escape velocity requires substantial fuel. For standard rockets, only about 2-5% of the rocket mass is the payload! The rest is the mass of the structure + fuel. For example in Russian Soyuz rockets to send a 7-ton ship to the ISS you need a 300-ton rocket. The American Apollo mission for a 47-ton spacecraft (orbiter and landing platform) and sending it to the Moon needed a 3000-ton rocket - about the same ratio. Just imagine the energy needed to launch something into space! It's amazing how people could come up with such a thing!
Returnable stages and reusable ships
A key innovation in rocket technology recently is reusable rocket stages. SpaceX reuses the spent stages and head fairing of the Falcon 9. The spent stages return to Earth and land vertically. Although this technology has been known for a long time, only SpaceX has implemented it on an industrial scale.
Why is this necessary? Imagine that you need to fly an airplane to another city, and after each flight - you need to build a new airplane. That's inefficient. So the next logical step to improve rockets is to reuse elements of the rocket. By the way, it is the same with manned spaceships - mankind is slowly starting to use reusable ships.
While the concept of reusable rockets was discussed for decades it became feasible just recently. Buran and the Space Shuttle were the first reusable rockets, but they were not economically viable. Returning to the first stage makes more sense.
Rocket classification
Depending on the mass of the payload to be launched, the following types of rockets are classified:
Super-heavy lift vehicle: > 50,000 kilograms (110,000 lb) - e.g. Saturn V, Starship.
Heavy-lift launch vehicle: > 20,000 to 50,000 kilograms (44,000 to 110,000 lb) - e.g. Ariane 5.
Medium-lift launch vehicle: > 2,000 to 20,000 kilograms (4,400 to 44,100 lb) - e.g. Soyuz.
Small-lift launch vehicle: < 2,000 kilograms (4,400 lb) - e.g. Vega
*Ultra Small-lift vehicle: ~100-300 kg (220 lb) - e.g. Electron by Rocket Lab - (a subset of small-lift rockets).
The type of rocket depends on the mission and the economic model of the company. If it is a state-owned company engaged in manned flights, it is from medium-class rockets and above (because manned spacecraft weigh a lot). The same rockets most often have unmanned modification - for launching spacecraft into space (for example, Soyuz and Falcon rockets have an unmanned and manned version).
Private companies build rockets depending on the market niche they want to cover, namely the mass of the spacecraft to be launched. For example, RocketLab and their Electron rocket (see our article about RocketLab) cater the growing niche of small payloads up to 100-150 kg. While the cost per 1 kg is higher you can launch them more frequently. Their goal is to launch small spacecraft quickly and efficiently, which were typically associated with payloads on larger rockets, thus extending the launch procedure.
The opposite example is SpaceX and its huge Starship rocket. This rocket is of a Super-heavy class, which is designed to launch both spacecraft and spaceships, including toward Mars. The key feature of this rocket is the low price of launching payloads (Elon Musk has repeatedly stated that the price will be around $100 per kg of payload in orbit). This will make it much cheaper to launch satellites, which means that it will be possible to make vehicles heavier , etc. For more details on how the launch services market will change with the appearance of the Starship rocket, see our article on this rocket. We also recommend another article - Jet Propulsion Overview.
Control system - key technology
Of course, one of the key systems of a rocket is the control system, which performs the primary task of delivering the payload to a specified point and speed. Typically, the trajectory of the launch vehicle is pre-calculated and stored in the onboard computer as a nominal trajectory, and the control system's job is to maintain this path.
The main challenges are the rocket's mass and the high speed and thrust, which can cause significant deviations from the nominal trajectory due to minor perturbing factors like wind. Additionally, the engines operate non-ideally and asymmetrically, issues that the in-flight control system must correct.
These problems ruined the Soviet lunar program. Running parallel to the American mission Apollo, the Soviet lunar program developed the N-1 rocket. The main difficulty was that the rocket had as many as 30 engines on the first stage. There were 4 launches of the rocket and all were unsuccessful - the control system that existed at that time could not handle so many engines. In comparison to the N-1, the Saturn 5, which took the Apollo spacecraft to the moon - had several 5 powerful engines. It was much easier to control.
By the way, if you look at the Starship engine layout - It is similar to the N-1…
And how does the rocket control?
Two basic principles. The first involves thrusters; rockets can have special steering engines that are smaller in size and thrust but sufficient for maneuvering. Additionally, some main engines may be movable rather than fixed, allowing for control of the thrust vector's direction.
Another method - aerodynamic rudders (Grid fin, for example, or other types of rudders). Their deflection leads to a change in the trajectory of the rocket. Similar to an airplane's elevator - the rudders rotate, changing the direction of the airflow, which causes a control force that can be used to steer the rocket launcher. In addition to these principles, other types of missiles (ultra-small rockets, for example) may use special types of controls. For example, gas rudders on the nozzle slice and other.
The choice of control method depends on the rocket's mass and flight speeds.
Future and prospects
Technology is constantly advancing, with new rockets and principles being developed. The introduction of the Falcon 9 rocket with a reentry stage has transformed the launch services market, nearly monopolizing it for SpaceX. RocketLab's Electron rocket demonstrates success in targeting small payloads.
What's next?
Humanity is nearing its technological peak in rocket launches. Currently, the focus is on constructing larger rockets, like Starship, enhancing rocket components (such as the reentry stage of Falcon 9), and refining economic models (e.g., RocketLab's Electron rocket, which uses 3D-printed parts). Despite these advancements, fundamentally new technologies for rocket launches remain undeveloped (we wrote about it in this article 2 years ago). Given the current jet propulsion technology, a Mars journey takes about half a year. To improve space travel efficiency, breakthrough technologies are essential.
Several companies are pioneering these innovations. For instance, SpinLaunch (they raised $146M in total including $71M series B in September 2022). is an innovative new space technology company that has created an alternative method for putting 200-kilogram class satellites into low earth orbit. They launch spacecraft by spinning them using a special technology on Earth. Due to centrifugal force, the spacecraft flies into the tube at high speed and reaches the desired orbit, where the upper stage is switched on. And the company Space Perspective offers to fly tourists to space on specialized cylinders (balloons).
Of course, despite all this, there is a lot of new and interesting technology. We are all waiting for the launch of Starship, which will probably open the way to Mars and make it cheaper to launch satellites into space.
We at Space Ambition believe that for interplanetary and intergalactic travel our descendants will use other physical principles so we need to keep doing research in fundamental physics. Check out our previous article about new physics and the importance of astronomy in this task.
Perhaps right now somewhere a scientist in a lab is developing a new type of engine that will revolutionize the science of space and take us to other solar systems. And all we have to do is love space, support scientists, and just wait :)
What do you think - how will we launch satellites and people into space in the future?
What do you think about Nuclear Thermal propulsion, isn’t NASa/DARPA working on one? Or something else like the Reaction Engines SABRE for responsive launch? Thanks