A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage rocket, but the term is more general and also encompasses vehicles like the Space Shuttle. Most launch vehicles operate from a launch pad, supported by a launch control center and systems such as vehicle assembly and fueling. Launch vehicles are engineered with advanced aerodynamics and technologies, which contribute to high operating costs. An orbital launch vehicle must lift its payload at least to the boundary of space, approximately 150 km (93 mi) and accelerate it to a horizontal velocity of at least 7,814 m/s (17,480 mph). Suborbital vehicles launch their payloads to lower velocity or are launched at elevation angles greater than horizontal. Practical orbital launch vehicles use chemical propellants such as solid fuel, liquid hydrogen, kerosene, liquid oxygen, or hypergolic propellants. Launch vehicles are classified by their orbital payload capacity, ranging from small-, medium-, heavy- to super-heavy lift.
History
Mass to orbit
Launch vehicles are classed by NASA according to low Earth orbit payload capability:
Small-lift launch vehicle: < 2,000 kilograms (4,400 lb) – e.g. Vega Medium-lift launch vehicle: 2,000 to 20,000 kilograms (4,400 to 44,100 lb) – e.g. Soyuz ST Heavy-lift launch vehicle: 20,000 to 50,000 kilograms (44,000 to 110,000 lb) – e.g. Ariane 5 Super-heavy lift vehicle: > 50,000 kilograms (110,000 lb) – e.g. Saturn V Sounding rockets are similar to small-lift launch vehicles, however they are usually even smaller and do not place payloads into orbit. A modified SS-520 sounding rocket was used to place a 4-kilogram payload (TRICOM-1R) into orbit in 2018.
General information
Orbital spaceflight requires a satellite or spacecraft payload to be accelerated to high velocity. In the vacuum of space, reaction forces must be provided by the ejection of mass, resulting in the rocket equation. The physics of spaceflight are such that rocket stages are typically required to achieve the desired orbit. Expendable launch vehicles are designed for one-time use, with boosters that usually separate from their payload and disintegrate during atmospheric reentry or on contact with the ground. In contrast, reusable launch vehicles are designed to be recovered intact and launched again. The SpaceX Falcon 9 is an example of a reusable launch vehicle. As of 2023, all reusable launch vehicles that were ever operational have been partially reusable, meaning some components are recovered and others are not. This usually means the recovery of specific stages, usually just the first stage, but sometimes specific components of a rocket stage may be recovered while others are not. The Space Shuttle, for example, recovered and reused its solid rocket boosters, the Space Shuttle orbiter that also acted as a second stage, and the engines used by the core stage (the RS-25, which was located at the back of the orbiter), however the fuel tank that the engines sourced fuel from, which was separate from the engines, was not reused. For example, the European Space Agency is responsible for the Ariane V, and the United Launch Alliance manufactures and launches the Delta IV and Atlas V rockets.
Launch platform locations
Launchpads can be located on land (spaceport), on a fixed ocean platform (San Marco), on a mobile ocean platform (Sea Launch), and on a submarine. Launch vehicles can also be launched from the air.
Flight regimes
A launch vehicle will start off with its payload at some location on the surface of the Earth. To reach orbit, the vehicle must travel vertically to leave the atmosphere and horizontally to prevent re-contacting the ground. The required velocity varies depending on the orbit but will always be extreme when compared to velocities encountered in normal life. Launch vehicles provide varying degrees of performance. For example, a satellite bound for Geostationary orbit can either be directly inserted by the upper stage of the launch vehicle or launched to a geostationary transfer orbit (GTO). A direct insertion places greater demands on the launch vehicle, while GTO is more demanding of the spacecraft. Once in orbit, launch vehicle upper stages and satellites can have overlapping capabilities, although upper stages tend to have orbital lifetimes measured in hours or days while spacecraft can last decades.
Distributed launch Distributed launch involves the accomplishment of a goal with multiple spacecraft launches. A large spacecraft such as the International Space Station can be constructed by assembling modules in orbit, or in-space propellant transfer conducted to greatly increase the delta-V capabilities of a cislunar or deep space vehicle. Distributed launch enables space missions that are not possible with single launch architectures. Mission architectures for distributed launch were explored in the 2000s and launch vehicles with integrated distributed launch capability built-in began development in 2017 with the SpaceX Starship design. The standard Starship launch architecture is to refuel the spacecraft in low Earth orbit to enable the craft to send high-mass payloads on more energetic missions.
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