The flight passed over the far side of the Moon at an altitude of 254 kilometers (137 nautical miles) from the lunar surface, 400,171 km (248,655 mi) from Earth, a …show more content…
He assigned them to the backup crew simply because of a lack of flight-qualified manpower in the Astronaut Office at the time the assignment needed to be made.[2] Slayton felt Cooper had a very small chance of receiving the Apollo 13 command if he did an outstanding job with the assignment, which he did not. Despite Eisele's issues with management, Slayton always intended to assign him to a future Apollo Applications Program mission rather than a lunar mission, but this program was eventually cut down to only the Skylab …show more content…
An anomaly occurred when the second-stage, center (inboard) engine shut down about two minutes early. The four outboard engines and the third-stage engine burned longer to compensate, and the vehicle achieved very close to the planned circular 100 nautical miles (190 km) parking orbit, followed by a normal translunar injection about two hours later.[5][9]The engine shutdown was determined to be caused by severe pogo oscillations measured at a strength of 68 g and a frequency of 16 hertz, flexing the thrust frame by 3 inches (76 mm). The vehicle's guidance system shut the engine down in response to sensed thrust chamber pressure fluctuations. Pogo oscillations had been seen on previous Titan rockets, and also on the Saturn V during Apollo 6,[10] but on Apollo 13, they were amplified by an unexpected interaction with turbopump cavitation.[11] Later missions implemented anti-pogo modifications that had been under development. These included addition of a helium-gas reservoir to the center engine liquid oxygen line to damp pressure oscillations, an automatic cutoff as a backup, and simplification of the propellant valves of all five second-stage