<Tr> <Td> Shuttle </Td> <Td> 1981 </Td> <Td> 135 </Td> </Tr> <Tr> <Td> Shenzhou </Td> <Td> 2003 </Td> <Td> </Td> </Tr> <P> Orbital spaceflight from Earth has only been achieved by launch vehicles that use rocket engines for propulsion . To reach orbit, the rocket must impart to the payload a delta - v of about 9.3--10 km / s . This figure is mainly (~ 7.8 km / s) for horizontal acceleration needed to reach orbital speed, but allows for atmospheric drag (approximately 300 m / s with the ballistic coefficient of a 20 m long dense fueled vehicle), gravity losses (depending on burn time and details of the trajectory and launch vehicle), and gaining altitude . </P> <P> The main proven technique involves launching nearly vertically for a few kilometers while performing a gravity turn, and then progressively flattening the trajectory out at an altitude of 170 + km and accelerating on a horizontal trajectory (with the rocket angled upwards to fight gravity and maintain altitude) for a 5 - 8 minute burn until orbital velocity is achieved . Currently, 2 - 4 stages are needed to achieve the required delta - v. Most launches are by expendable launch systems . </P>

Speed a rocket has to be accelerated to in order to launch a satellite into orbit of the earth