- published: 13 Apr 2016
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In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad, and other infrastructure. Although a carrier rocket's payload is often an artificial satellite placed into orbit, some spaceflights, such as sounding rockets, are sub-orbital, while others enable spacecraft to escape Earth orbit entirely.
Earth orbital launch vehicles typically have at least two stages, and sometimes as many as four or more.
Expendable launch vehicles are designed for one-time use. They usually separate from their payload and disintegrate during atmospheric reentry. In contrast, reusable launch vehicles are designed to be recovered intact and launched again. The Space Shuttle was the only launch vehicle with components used for multiple orbital spaceflights. SpaceX is developing a reusable rocket launching system for their Falcon 9 and Falcon Heavy launch vehicles. A second-generation VTVL design was announced in 2011. The low-altitude flight test program of an experimental technology-demonstrator launch vehicle began in 2012, with more extensive high-altitude over-water flight testing planned to begin in mid-2013, and continue on each subsequent Falcon 9 flight.Non-rocket spacelaunch alternatives are at the planning stage, although it is known that some companies are developing actual launch platforms, such as the Spanish zero2infinity with their rockoon-based launcher "bloostar".
Space launch is the earliest part of a flight that reaches space. Space launch involves liftoff, when a rocket or other space launch vehicle leaves the ground, floating ship or midair aircraft at the start of a flight. Liftoff is of two main types: rocket launch (the current conventional method), and non-rocket spacelaunch (where other forms of propulsion are employed, including airbreathing jet engines or other kinds).
Space has no physical edge to it as the atmospheric pressure gradually reduces with altitude; instead, the edge of space is defined by convention, often the Kármán line of 100 km. Other definitions have been created as well, in the US for example space has been defined as 50 miles.
Therefore, by definition for spaceflight to occur, sufficient altitude is necessary. This implies a minimum gravitational potential energy needs to be overcome: for the Kármán line this is approximately 1 MJ/kg. W=mgh, m=1 kg, g=9.82 m/s2, h=105m. W=1*9.82*105≈106J/kg=1MJ/kg