near to its orbital ground track and helped pull PFS-2 into the Moon. Mission events Elements of the spacecraft and launch vehicle began arriving at Kennedy Space Center in July 1970, and all had arrived by September 1971. Apollo 16 was originally scheduled to launch on March 17, 1972. One of the bladders for the CM's reaction control system burst during testing. This issue, in combination with concerns that one of the explosive cords that would jettison the LM from the CSM after the astronauts returned from the lunar surface would not work properly, and a problem with Duke's spacesuit, made it desirable to slip the launch to the next launch window. Thus, Apollo 16 was postponed to April 16. The launch vehicle stack, which had been rolled out from the Vehicle Assembly Building on December 13, 1971, was returned thereto on January 27, 1972. It was rolled out again to Launch Complex 39A on February 9. The official mission countdown began on Monday, April 10, 1972, at 8:30 am, six days before the launch. At this point the SaturnV rocket's three stages were powered up, and drinking water was pumped into the spacecraft. As the countdown began, the crew of Apollo 16 was participating in final training exercises in anticipation of a launch on April 16. The astronauts underwent their final preflight physical examination on April 11. The only holds in the countdown were the ones pre-planned in the schedule, and the weather was fair as the time for launch approached. Launch and outward journey The Apollo 16 mission launched from the Kennedy Space Center in Florida at 12:54 pm EST on April 16, 1972. The launch was nominal; the crew experienced vibration similar to that on previous missions. The first and second stages of the SaturnV (the S-IC and S-II) performed nominally; the spacecraft entered orbit around Earth just under 12 minutes after lift-off. After reaching orbit, the crew spent time adapting to the zero-gravity environment and preparing the spacecraft for trans-lunar injection (TLI), the burn of the third-stage rocket that would propel them to the Moon. In Earth orbit, the crew faced minor technical issues, including a potential problem with the environmental control system and the S-IVB third stage's attitude control system, but eventually resolved or compensated for them as they prepared to depart towards the Moon. After two orbits, the rocket's third stage reignited for just