To escape earth's gravity the " slingshot effect" was used whereby the vehicle orbited the earth with increasing speed and then as it reached escape velocity extra thruster rockets were fired to go out of orbit . For landing on the moon once again the lander module detached from the orbiter and retro thrusters were used to slow down and land on a preplanned spot on the moon,s surface which was fixed by earlier observation of the moon's surface by fly-by space vehicles many times.on the.For returning , rockets were fired on the lander module into the moon orbit where it joined up with the orbiter and returned to earth .
