module to Earth, as the flight path took the module through the atmosphere, using atmospheric drag to reduce velocity. The test flights in Earth orbit required retrograde propulsion, which was provided by the large Service Propulsion Engine on the service module. The same engine was used as a retrorocket to slow the spacecraft for lunar orbit insertion. The Apollo Lunar Module used its descent stage engine to drop from orbit and land on the Moon. Retrorockets were used to back the S-IC and S-II stages off from the rest of the vehicle after their respective shutdowns during the Saturn V's launch to Earth parking orbit. Space Shuttle program The Space Shuttle Orbital maneuvering system provided the vehicle with a pair of powerful liquid-fueled rockets for both reentry and orbital maneuvering. One was sufficient for a successful reentry, and if both systems were to fail, the reaction control system could slow the vehicle enough for reentry. Launch vehicle staging To ensure clean separation and prevent contact, multistage rockets such as the Titan II, Saturn I, Saturn IB, and Saturn V may have small retrorockets on lower stages, which ignite upon stage separation. Meanwhile, the succeeding stage may have ullage rockets, both to aid separation and ensure good starting of liquid-fuel engines. Landers Retrorockets are also used in landing spacecraft on other astronomical bodies, such as the Moon and Mars, as well as enabling a spacecraft to enter an orbit around such a body, when otherwise it would scoot past and off into space again. As pointed out above (in connection with Project Apollo) the main rocket on a spacecraft can be re-oriented to serve as a retrorocket. The Soyuz capsule uses small rockets for the last phase of landing. Reusable launch systems New uses for retro-thrust rockets emerged since 2010 for reusable launch systems. After second stage separation, the first stage of SpaceX's Falcon 9 and Falcon Heavy rockets uses one to three of the main engines in order to decelerate for propulsive landing. The first stage is then recovered, refurbished and prepared for the next flight. The boosters of other orbital rockets are routinely destroyed after a single use by atmospheric reentry and high-speed impact in the ocean. Companies like Blue Origin with their New Glenn, Link Space with their New Line 1 and national projects like the European Commission's RETALT project and the China National Space Administration's Long March