Astronaut Buzz Aldrin stands next to the United States flag during the Apollo 11 EVA.
Astronaut Aldrin walks toward the Laser Ranging RetroReflector (LR-3) and Lunar Module after the Passive Seismic Experiment Package was deployed.
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The previous space programs dealt with the mechanics of space travel such as takeoffs, achieving orbits, spacecraft maneuvering, EVAs, rendezvous, dockings, and maneuvering with docked vehicles. These proved essential for traveling to the moon. However, the Apollo program was charged with the task of reaching the moon. This meant developing vehicles capable of that task such as the Saturn V, Service Module, Command Module, and Lunar Excursion Module (LEM). These vehicles, combined with the knowledge and skill of orbiting, spacecraft maneuvering, EVAs, rendezvous, and docking made it possible for the Apollo astronauts to walk on the moon.
However, the Apollo program did suffer a huge setback when fire struck the Apollo 1 Command Module during a preflight test on the launch pad. On Jan. 27, 1967, America lost three of its heroes in astronauts Gus Grissom, Edward White, and Roger Chaffee.
Following the fire, a seven-member board, under the direction of NASA Langley Research Center director Dr. Floyd L. Thompson, conducted a comprehensive investigation to pinpoint the cause of the fire. During the investigation, NASA postponed and suspended several programs until the Control Module was cleared for flight. The final report, completed in April 1967, presented the results of the investigation and made specific recommendations that led to major design and engineering modifications, and revisions to test planning, test discipline, manufacturing processes and procedures, and quality control.
Following the tragedy of Apollo 1, the new spacecraft underwent demonstration during Apollo 7, which was commanded by Walter Schirra and piloted by Donn Eisele and Walter Cunningham in October 1968. It was during this mission that the first live television broadcasts were made from a manned spacecraft.
The Saturn IB, in its first trial with people aboard, provided a perfect launch and its first stage dropped off 2 min., 25 s later. The S-IVB second stage took over, giving astronauts their first ride atop a liquid hydrogen-fueled rocket. About ten and a half minutes after launch, the Apollo 7 spacecraft reached the first stage of its journey, an orbital path 227 by 285 km above the earth. The S-IVB stayed with the spacecraft for about one and a half orbits, then separated. Schirra fired the spacecraft's small rockets to pull 50 ft ahead of the S-IVB, then turned the spacecraft around to simulate docking, as would be necessary to extract a Lunar Module for a Moon landing.
The Service Module, which was critical for propelling future astronauts home from the moon, performed successfully during this mission. There were eight nearly perfect firings out of eight attempts. During the first firing, the crew was taken by surprise at the force and roughness of the flight because the launch of the Saturn vehicle was much smoother.
The Apollo spacecraft, for the most part, performed as expected. Durability was shown for 10.8 days — longer than a journey to the Moon and back. With a few exceptions, the other systems in the spacecraft operated as expected. Occasionally, one of the three fuel cells supplying electricity to the craft developed some unwanted high temperatures, but load-sharing hookups among the cells prevented any power shortage. The chargers for the batteries needed for reentry returned 50 to 75% less energy than expected. The most serious problem was the overheating of fuel cells, which might have failed when the spacecraft was too far from Earth to return on batteries, even if fully charged.
Apollo 7 qualified the use of the command and service modules for the proposed lunar-orbit mission to follow. All that was needed now was a launch vehicle powerful enough to propel the spacecraft to the moon.
The next step was achieving lunar orbit. Apollo 8, manned by astronauts Borman, Lovell, and Anders, demonstrated the capabilities of the Saturn V launch vehicle, translunar injection, spacecraft navigation, communications, and midcourse corrections. The mission, which launched December 21, 1968, also entailed photographing proposed Apollo landing sites and locations of scientific interest, with high-resolution cameras. Apollo 8 lasted six days and three hours and achieved a lunar orbit of 312 km by 111 km.
Apollo 9, flown by astronauts James McDivitt, David Scott, and Russell Schweickart in March 1969, demonstrated all of the lunar hardware in earth orbit and lunar orbit rendezvous mission activities such as transposition, docking withdrawal, intervehicular crew transfer, EVA, SPS and DPS burns, and Lunar Module active rendezvous and docking. The mission lasted for ten days and one hour at an altitude of 192 x 190 km.
The next mission that followed was the dress rehearsal for landing on the moon. In May 1969 Apollo 10, manned by astronauts Eugene Cernan, John Young, and Thomas Stafford, demonstrated the performance of the Lunar Module and the Command/Service Module in lunar gravity. The crew performed docked and undocked lunar navigation with the Lunar Module and Command/Service Module. The Lunar Module was taken to within 50,000 ft of the lunar surface. Upon the conclusion of this mission, every technology developed for travel to the moon had been demonstrated and evaluated, with the exception of the actual landing.
Apollo 11, commanded by astronaut Neil Armstrong, was launched in July 1969 to take the ultimate step in the country's manned lunar program. The Command/Service Module, piloted by astronaut Michael Collins, carried Apollo 11 into lunar orbit, and upon conclusion of lunar activities, transported the crew back to Earth. The first and second burns made in lunar orbit were accomplished successfully. "As we pass behind the Moon, we have just over eight minutes to go before the burn," remembered Collins. "We are super-careful now, checking and rechecking each step several times. When the moment finally arrives, the big engine instantly springs into action and reassuringly plasters us back in our seats. The acceleration is only a fraction of one g, but it feels good nonetheless. For six minutes we sit there peering intent as hawks at our instrument panel, scanning the important dials and gauges, making sure that the proper thing is being done to us. When the engine shuts down, we discuss the matter with our computer and I read out the results: 'Minus one, plus one, plus one.' The accuracy of the overall system is phenomenal: out of a total of nearly three thousand feet per second, we have velocity errors in our body axis coordinate system of only a tenth of one foot per second in each of the three directions. That is one accurate burn, and even Neil acknowledges the fact."
"The second burn to place us in closer circular orbit of the Moon, the orbit from which Neil and I would separate from the Columbia (Command Module) and continue on to the Moon, was critically important," said astronaut Buzz Aldrin, Lunar Module pilot. "It had to be made in exactly the right place and for exactly the correct length of time. If we overburned for as little as two seconds we'd be on an impact course for the other side of the Moon. Through a complicated and detailed system of checks and balances, both in Houston and in lunar orbit, plus star checks and detailed platform alignments, two hours after our first lunar orbit we made our second burn, in an atmosphere of nervous and intense concentration. It, too, worked perfectly."
Separation of the Lunar Module from the Command Module occurred just as planned. The Lunar Module (called Eagle) performed two separate burns to reach the lunar surface, according to Collins. The first burn served to drop Eagle's perilune to 50,000 ft. Upon reaching the eastern edge of the Sea of Tranquility, Eagle's descent engine fired for the last time, and the spacecraft went into a 12-minute computer-controlled descent until it reached a point at which Armstrong took over for a manual landing. During the descent, several warnings sounded within the Lunar Module that almost caused the astronauts to abort the mission. One of the warnings was a sign that the Lunar Module's computer was in an "executive overflow," meaning that it had been called upon to do too many things at once and was forced to postpone some of them. Houston directed astronauts Aldrin and Armstrong to continue with the landing because the warnings were not critical.
Exhaust dust kicked up by the engine made the landing difficult because it degraded the astronauts' ability to determine their altitude and transnational velocities over the ground. "It's quite important not to stub your toe during the final phases of touchdown," said Armstrong. On July 20, 1969 at 4:17 p.m. EDT, Apollo 11 reported: "Houston, Tranquility Base here. The Eagle has landed!"
Shortly after, Astronauts Armstrong and Aldrin conducted the first lunar EVA, which lasted 2 h, 31 min. Armstrong was the first one to make his way out of the Lunar Module. While taking his last step off the ladder onto the moon's surface, he said: "That's one small step for man...one giant leap for mankind." Aldrin followed Armstrong down onto the moon's surface, where they deployed the United States' flag and unveiled a plaque on the Lunar Module descent stage with the inscription: "Here Men From Planet Earth first Set Foot Upon the Moon. July 1969 A.D. We Came In Peace For All Mankind."
The mission was the final step in achieving an aggressive goal set by President Kennedy eight years before. Much had been learned during this effort despite the loss of astronauts Grissom, White, and Chaffee. The knowledge gained from these programs not only served as a model for future developments for space exploration, but the technology is still in service today with our computers, cellular phones, digital television, aircraft, automobiles, and medicine. It has also inspired many new efforts such as the exploration of Mars and the construction of the International Space Station.
