Moon. He stayed around the platform-the "front porch" as the astronauts called it-by that hatch for about three-quarters of an hour, checking the handholds and the lights that had been trained on specific portions of the spacecraft. Scott, mean time, had opened the command module hatch and clambered partially outside, st hooked to the spacecraft through a life-support umbilical system. Schweickart was using a portable life-support system in his EVA, checki for the first time outside. Both men detailed their experiences, took some graphs, and retrieved some thermal samples, testing the maneuverability space suits and the accessibility of the sample locations on the spacecraft planned to have Schweickart move externally from the LM to the comman to verify a way of getting from one spacecraft to the other if the tunne available. This step was not completed beyond evaluating the specific would have been necessary to such a transfer. THE LM ON ITS OWN The fifth day of the Apollo 9 mission was the crucial test for and McDivitt entered the LM, powered it up, and prepared command module. They released the craft, and the astron the LM. They backed away and rotated the module so th module, could see that all the legs were down and ext no physical failures in the craft itself. Then they fired t to move the LM into a parallel orbit about three n module. The mechanics of the orbit were such th: twice during each swing around the Earth, the tw that Scott could initiate rescue operations should For nearly six hours the two astronauts in of the lunar approach and departure. They fired the descent engine again, then jettiso ascent engine for the first time in space miles below and 80 miles behind the c to a rendezvous and docking, much th on Apollo 11. The first phase of thei a 100 ft separation, so that both spa a solid and clean joining that veri docking and locking mechanism its engine to insert it into a hi From here on, the rest performance of the spacecr complete with landing and the remaining five days i sion system, once to lo staging system, and c series of landmark t were observed an 192 APOLL obtain pictures in different ther augmented by pictures sing conventional films. firing of the service propulsion on their target in the Atlantic, by Navy helicopters. o the Moon-or at least within 11 mission. There had been some have landed, having gotten so close. ible for that lunar module to land. lunar landing, or, to be more precise, back to the command module. It was a that was the way it was used. Besides, Buch that no crew would have made such o 10 mission commander, with command module pilot Eugene A. Cernan. They were on May 18, 1969, about two and one-half Its successful test flight. As the establishment of the Earth parking orbit that and approval from Mission Control, the crew fired the parking orbit and enter the translunar trajectory. and and service modules from the S-IVB, and turned le. Ejection of the docked spacecraft followed, as the maneuver to increase the distance between the docked stage. Then they eased the S-IVB into a solar orbit by xcess propellants. ectory had been established so precisely that it was not rst midcourse correction, generally a routine step during the ght toward the Moon. Finally, after a little more than a day slunar midcourse correction was done to make the flight path de with the trajectory planned for the Apollo 11 mission. Three away from the launch pad, the crew fired the service propulsion six minutes, inserting the spacecraft into a lunar orbit. Apollo 10 the Moon in a circular flight path about 60 miles above its surface. d Cernan entered the lunar module about six hours later to check the ransferred some needed equipment, and moved back into the command normal sleep period. They then reentered the lunar module to go through ystems check to prepare for the lunar-orbit rendezvous, the final check of echanics of the Apollo mission. after two hours into the fourth day, the two spacecraft were undocked and The crew performed its routine communications and radar checks, and then GETTING IT ALL TOGETHER 195 multiple-camera assembly using different film emulsions to obtain pictures in different portions of the photographic spectrum. These were further augmented by pictures taken almost simultaneously with hand-held cameras, using conventional films. Once out of orbit, following the eighth successive firing of the service propulsion system, the reentry was normal. They landed right on their target in the Atlantic, 241 hours after takeoff, and were recovered quickly by Navy helicopters. Apollo 10 was different, because it did go to the Moon-or at least within 47,000 feet of it-in its rehearsal of the Apollo 11 mission. There had been some speculation about whether or not the crew might have landed, having gotten so close. They might have wanted to, but it was impossible for that lunar module to land. It was an early design that was too heavy for a lunar landing, or, to be more precise, too heavy to be able to complete the ascent back to the command module. It was a test module, for the dress rehearsal only, and that was the way it was used. Besides, the discipline on the Apollo program was such that no crew would have made such a decision on its own in any event. Thomas P. Stafford was the Apollo 10 mission commander, with command module pilot John W. Young and lunar module pilot Eugene A. Cernan. They were launched on schedule at 11:49 a.m., on May 18, 1969, about two and one-half months after Apollo 9 had set out on its successful test flight. THE DRESS REHEARSAL Launching was routine, as was the establishment of the Earth parking orbit that followed. After systems checks, and approval from Mission Control, the crew fired the S-IVB stage engine to leave the parking orbit and enter the translunar trajectory. Then they separated the command and service modules from the S-IVB, and turned to dock with the lunar module. Ejection of the docked spacecraft followed, as the crew performed a separation maneuver to increase the distance between the docked spacecraft and the S-IVB stage. Then they eased the S-IVB into a solar orbit by propulsive venting of its excess propellants. The translunar trajectory had been established so precisely that it was not necessary to make the first midcourse correction, generally a routine step during the early phases of the flight toward the Moon. Finally, after a little more than a day in flight, a single translunar midcourse correction was done to make the flight path of Apollo 10 coincide with the trajectory planned for the Apollo 11 mission. Three days and four hours away from the launch pad, the crew fired the service propulsion system for almost six minutes, inserting the spacecraft into a lunar orbit. Apollo 10 now was orbiting the Moon in a circular flight path about 60 miles above its surface. Stafford and Cernan entered the lunar module about six hours later to check the systems. They transferred some needed equipment, and moved back into the command module for a normal sleep period. They then reentered the lunar module to go through a complete systems check to prepare for the lunar-orbit rendezvous, the final check of the flight mechanics of the Apollo mission. Just after two hours into the fourth day, the two spacecraft were undocked and separated. The crew performed its routine communications and radar checks, and then GETTING IT ALL TOGETHER 195 Stafford and Cernan began their descent toward the lunar surface by firing the descent stage engine. They let down to an altitude of about eight miles above the surface, the closest they were to go in that mission. Over one of the selected landing sites, they checked the landing radar, which worked successfully. After this descent, Stafford and Cernan maneuvered the LM into an elliptical orbit, 11 by 190 miles, to establish the conditions for their rendezvous with Young in the command module. They completed one swing around the Moon, and then staged the lunar module, firing its ascent engine in a simulation of a return from the lunar surface. These words read rapidly, as if the performance they describe were done swiftly. But it must be appreciated that this rehearsal, which was planned to follow the schedule for the Apollo 11 as closely as possible, actually took more than six and one-half hours from the beginning of the descent toward the Moon until both spacecraft had docked for the second time for crew transfer back to the CSM. FLAWLESS RENDEZVOUS The rendezvous was flawless. It began with the usual maneuvering by the LM, using its reaction control system. Young, in the command module, nominally had nothing to do except to wait passively for the docking; the lunar module was expected to be the active seeker and mover in the rendezvous. But in fact he had to be prepared to take over the rendezvous if anything failed on the LM. So he checked the rendezvous every step of the way with sextant observations and ranging with very-highfrequency radio, working out the things he would have to do in the event of a lunar module system failure. The terminal phase of the docking began an hour later, and the lunar module nudged its way into the locking mechanism of the command module. The jubilant crews met back in the command module. For the final day in lunar orbit, Stafford, Young, and Cernan spent their time in a series of experiments that would add to the general fund of Apollo knowledge. They tracked landmarks, worked on alignment exercises for the inertial platform, and took a series of stereo-pair and sequence photographs of the lunar surface, singling out features that would guide future landing-site selections. And then it was time for the return to Earth. They fired the service module engine once again to move out of the lunar orbit and back onto a trajectory toward the Earth, using a fast-return flight path that would bring them back again in 54 hours. The flight path again was established with great precision; the only midcourse correction needed was done just about three hours before the reentry, and it changed the velocity by slightly more than two feet per second, or about one part in 20,000. Fifteen minutes before reentry, they separated the command module from the service module. The command module bearing the crew streaked through the atmosphere; the parachutes deployed and let the spacecraft down on their target coordinates. The astronauts always made much of the accuracy of their landings, with a pool going to the crew landing closest to the target. (In fact, the navigation and guidance accuracy was such that the spacecraft computers pinpointed the target location better than the recovery ships were able to. Later, ships used inertial 196 APOLLO |