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A launch vehicle or carrier rocket is a rocket-propelled vehicle used to carry a payload from Earth's surface to space, usually to Earth orbit or beyond. A launch system includes the launch vehicle, launch pad, vehicle assembly and fuelling systems, range safety, and other related infrastructure.[not verified in body]
Orbital launch vehicles can be grouped based on many different factors, most notably payload mass, although price points are a major concern for some users. Most launch vehicles have been developed by or for national space programs, with considerable national prestige attached to spaceflight accomplishments. Payloads include crewed spacecraft, satellites, robotic spacecraft, scientific probes, landers, rovers, and many more.
Orbital spaceflight is difficult and expensive, with progress limited by the underlying technology as much as human and societal factors.
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.
Orbital spaceflight requires a satellite or spacecraft payload to be accelerated to very 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 vehicle boosters are designed to be recovered intact and launched again. The Falcon 9 is an example reusable launch vehicle.
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 (GEO) 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 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 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 much more energetic missions.
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