The aeroshell's retrorockets fired to begin the lander de-orbit maneuver. After 18 orbits, Soyuz 1 fired its retrorockets and reentered the Earth's atmosphere. The spacecraft tested its instrumentation, posigrade rockets, retrorockets and recovery system. Cooper fired the retrorockets on the 120th orbit. The capsule carried live separation rockets, but dummy retrorockets. Like the 1970s era "Viking" spacecraft, "Phoenix" used retrorockets for its final descent. At 6 minutes 54 seconds after launch, retrorockets were fired. It then encountered strong winds as it descended, which caused uneven firing of the retrorockets. Therefore, it is critical that spacecraft have extremely reliable retrorockets. Its heat shield and retrorockets functioned as expected. The retrorockets would be kept on. Retrorockets on the back shell can slow descent. Two solid motor retrorockets were located inside each of the four conical engine fairings. SA-3 also featured the first use of retrorockets on Apollo hardware. Retrorockets on the side of the car slowed the vehicle.