Apollo 6 (AS -502 ) was the last unmanned test flight of a Saturn rocket as part of the Apollo program. For the second time the three-stage Saturn V was used, which is now both the Apollo spacecraft and a non- functioning Lunar Module led as payload, - the same configuration as it was also provided for the flight to the moon.
The launch took place on April 4, 1968 at 12:00 UTC clock from the Kennedy Space Center in Florida. However, he did not go smoothly. Violent vibration loaded the design, while the first stage was on fire. A manned flight would have led to termination. After separation of the first stage then occurred much greater problems in the second stage, caused by the vibration at the start of the launch. Two of the five engines switched off too early, what is the focal length of the remaining engines had to be extended by 58 seconds. The vibrations some supply lines were broken, the cause of the first failure. The second engine was the control system mistakenly disabled because the control lines between the two engines were vertausch. The third stage therefore had to burn longer. Rather than in a circular orbit of 160 km above the Earth's surface Apollo 6 was now in an elliptical orbit with 167 km perigee and 367 km apogee.
After two orbits, the third stage should be fired a second time, to simulate the bullet in a car to the moon, but did not succeed. The plan was a simulation of a crash during the transfer to the moon. This also speeds during re-entry should be achieved, which corresponds to a return from the moon. Here, the main engine of the Apollo spacecraft had to compensate to achieve the planned level of 22,000 km. The longer focal length of the engine of the service module of the test of the heat shield had to drop out partially. The capsule could not be brought to the required speed for lack of fuel.
The capsule splashed down on the same day at 22:23 UTC clock in about 80 km from the recovery ship USS Okinawa in the Pacific and was finally rescued from her.