Apollo 203 (Saturn SA-203)

Apollo 203 [GDK]

Although named Apollo 203, this mission did not carry any real Apollo hardware. The purpose of Apollo 203 was to check out the behaviour of the fuel inside the Saturn-4B stage in weightlessness, which was crucial to allow the reignition of the stage.

The prime payload consisted of two cameras, which looked inside the fuel and oxidizer tanks.

Additionally in the 1680 kg nose cone, which remained attached, a cryogenic nitrogen experiment was carried. It was to verify how cryogenic liquid nitrogen would behave under weightless conditions in support of future fuel cell system development. For the experiment, liquid nitrogen was chosen to serve as a surrogate for liquid oxygen, as it possesses similar properties and it is safer to handle.

The two-stage Saturn-1B launch vehicle boosted a payload into a 188 km circular orbit with a period of 88.21 minutes and an inclination of 31.94°. The S-IVB engine burned once in the Earth's atmosphere and then was shut down. The engine's capability to restart after coast was demonstrated. Flight information was obtained on venting and chill down systems, attitude and guidance control, thermal control, and performance of the propellant tanks. Two cameras were mounted to take photos to record the behavior of the liquid hydrogen fuel in the tanks. One of the cameras failed before launch, the other transmitted images to Earth. During the fourth orbit internal pressures built up in the S-IVB stage while a pressure differential test was being performed. The pressures built up well in excess of design values and the stage fragmented. However, all mission objectives were achieved. Subsequent study of the telemetry confirmed the bulkhead failure and destruction of the S-IVB stage had occurred at about the same pressure differential as had happened during ground testing.