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Launch vehicle

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A launch vehicle is a powerful machine designed to carry a payload into space. A payload is the actual cargo being transported, such as satellites or a crewed spacecraft.

Soyuz TMA-5 launch
Soyuz TMA-5 launch

Most launch vehicles use rocket propulsion to leave the Earth's surface. While many look like large, multi-stage missiles, the term also includes different designs like the Space Shuttle. These vehicles require complex support systems to function. They typically operate from a launch pad, which is connected to a launch control center. These facilities manage critical tasks like vehicle assembly and fueling.

To reach space, a vehicle must follow a very specific flight path. It must first travel vertically to exit the thick part of the atmosphere. Once it reaches a certain height, it must accelerate to a high horizontal velocity. This sideways speed is necessary to prevent the payload from falling back to Earth. For an orbital launch, the vehicle must reach a specific speed to stay in orbit. If the vehicle does not reach this speed, it is considered a suborbital launch. Suborbital vehicles carry payloads to lower velocities or launch at different angles.

Rocket engines generate power using various chemical propellants. These substances provide the reaction forces needed to move in the vacuum of space. Common propellants include liquid hydrogen, kerosene, and liquid oxygen. Some rockets use solid fuel for thrust. Others use hypergolic propellants, which ignite upon contact. The physics of these flights often require a multistage design. In a multistage rocket, different parts of the vehicle drop away as they run out of fuel. This reduces the total mass the remaining engines must carry.

Space Launchers
Space Launchers

NASA classifies launch vehicles based on their payload capacity to Low Earth Orbit (LEO). This helps engineers understand the scale of different missions. Small-lift launch vehicles can carry payloads between 0 and 2 tons. Medium-lift vehicles carry between 2 and 20 tons, such as the Soyuz ST. Heavy-lift vehicles carry between 20 and 50 tons, like the Ariane 5. Finally, super-heavy lift vehicles carry more than 50 tons. The Saturn V is a famous example of a super-heavy vehicle.

世界最大固体运载火箭引力一号成功首飞1
世界最大固体运载火箭引力一号成功首飞1

Some very small rockets, called sounding rockets, do not even reach orbit.

Launch vehicles are also categorized by whether they can be used more than once. Most traditional rockets are expendable launch vehicles. These are designed for one-time use, and their boosters usually disintegrate upon reentry or impact. In contrast, reusable launch vehicles are designed to be recovered intact. As of 2023, all operational reusable vehicles have been partially reusable. This means companies recover specific parts, like the first stage, while other parts are lost. The Space Shuttle is an example of partial reuse. It recovered its solid rocket boosters and its orbiter, but it did not reuse the large external fuel tank.

In recent years, private companies have revolutionized how rockets return to Earth. After 1980, the Space Shuttle and the Soviet Buran demonstrated horizontal landing capabilities. However, newer technology focuses on vertical landing. SpaceX began developing the ability to vertically land the first stage of the Falcon 9. They achieved their first successful landing in December 2015. Since 2017, rocket stages have routinely landed on pads near the launch site or on platforms at sea.

Space Launchers
Space Launchers

Blue Origin has also demonstrated this with its New Shepard suborbital vehicle. Blue successfully reflown and landed the same booster five times by October 2016.

Modern space exploration is also moving toward a concept called distributed launch. This involves using multiple launches to achieve a single large goal. For example, the International Space Station was built by assembling different modules while in orbit. This method allows for massive structures that a single rocket could not carry. Newer designs, such as the SpaceX Starship, are being built with integrated distributed launch capabilities. This includes the ability to refuel spacecraft in low Earth orbit. Such technology will allow much heavier payloads to travel to deep space or even other planets.

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File:Soyuz TMA-5 launch.jpg
Soyuz TMA-5 launch.jpg
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The Challenges of Outer Space NASA 1955.webm
File:世界最大固体运载火箭引力一号成功首飞1.png
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