A multi-part series on the history of NASA's Apollo missions.
After Apollo 7, NASA announced a bold plan for Apollo 8, the first manned flight with the Saturn V. This flight was originally planned to test the Lunar Module (LM) in Earth orbit, but progress on the lander was lagging. The LM test would be postponed by one flight. Instead, the next mission, piloted by Frank F. Borman II, James A. Lovell, Jr., and William A. Anders, would orbit the Moon!
Planning began with a proposal during the summer of 1968 by George M. Low, Director of the Apollo Spacecraft Program Office, for Apollo 8 to make a highly eccentric Earth orbiting flight that would loop around the Moon. This soon evolved into serious discussions about the feasibility of orbiting the Moon.
Senior NASA managers felt there was little increase in risk associated with lunar orbit versus the circumlunar proposal and taking this step was the only way to build enough experience to land on the Moon before the end of 1969. There was a political factor affecting the decision as well. The Central Intelligence Agency reported the Soviets were preparing for a piloted Zond flight around the Moon by the end of the year. A manned flight was expected at the mid-December lunar launch window for the Baikonur Cosmodrome, the Soviet launch site in Kazakhstan.
To rendezvous with an object in space, whether it’s another vehicle or the Moon, a spacecraft has to aim where the target will be at the time of rendezvous, not where it is when the craft is launched. For lunar missions, the geographical location of the launch site and position of the Moon in its 28-day orbit around the Earth limit when a launch can occur. This is called a “launch window.” The Apollo 8 Saturn V would not be ready until December 6; NASA’s next launch window after that began December 21. The Soviet launch window opened a week earlier.
NASA employees and contractors worked feverishly to prepare Apollo 8. When mid December passed with no Soviet launch everyone breathed a sigh of relief. Years later it was revealed the unmanned Zond 6 mission in November had actually failed despite official pronouncements of success, which caused the Soviets to postpone (and eventually cancel) the piloted flight.
Borman, Lovell and Anders began their flight on December 21. Despite the tremendous power of the Saturn V, acceleration during boost did not exceed 4 g’s. Two and a half minutes after launch, all the propellants in the first stage were exhausted and it was discarded. The second stage took over. Eight minutes, forty seconds after launch, the second stage was discarded. The third stage placed them in a parking orbit around the Earth and they made sure everything was ready for the “translunar injection,” or TLI, burn.
After a revolution and a half around the Earth, capsule communicator Michael Collins told Apollo 8, “All right, you are go for TLI.” In the night sky over Hawaii, a bright object appeared as the third stage fired for the second time. When it quit five minutes later, the astronauts were traveling more than 24,000 miles per hour, nearly seven miles every second, faster than any humans before them. This was fast enough to break free of Earth’s gravitational pull.
For three days, Borman, Lovell, and Anders coasted through space. The first of several planned mid course corrections -- firings of the Service Propulsion System (SPS) engine to fine-tune their path -- was so accurate that subsequent corrections were not needed.
Early on the morning of December 24, Christmas Eve, Apollo 8 looped behind the Moon. It passed within 69 miles of the surface, an amazing feat of navigation considering the target was about 238,000 miles from the starting point. While flying over the lunar farside, the astronauts fired the SPS engine to slow down and enter orbit. Without the firing, they would simply swing around the Moon and return to Earth. This was called a “free return” trajectory and added a level of safety to the flight. If the SPS engine failed, they were assured of a return trip home. People on Earth had no way of knowing if the lunar insertion burn succeeded until Apollo 8 emerged from the farside. Anxiously, flight controllers watched the clock. As the time approached for Apollo 8 to emerge from the Moon’s shadow, Mission Control began calling them. Finally, Mission Control reported, “We’ve got it! Apollo 8 is in lunar orbit.”
“Good to hear your voice,” replied Lovell.
A second SPS burn put Apollo 8 in a circular orbit 60 miles above the Moon. Anders said, “The color of the Moon looks like a very whitish gray, like dirty beach sand with lots of footprints in it. Some of these craters look like pickaxes striking concrete, creating a lot of fine haze dust.” He further compared the appearance of the lunar landscape to his children’s sand pile.
“The color of the Moon looks like a very whitish gray, like dirty beach sand with lots of footprints in it. Some of these craters look like pickaxes striking concrete, creating a lot of fine haze dust.”
The crew carried a 4.5-pound black and white television camera. That evening, during one of the broadcasts, Borman, Lovell, and Anders made Christmas Eve, 1968, one of the most memorable holidays ever when they read the first ten verses from the Bible. Borman began the reading: “In the beginning, God created the heavens and the Earth.” With the cratered surface of the Moon passing beneath them, the astronauts took turns reading from the Book of Genesis. Borman concluded the broadcast with “God bless all of you -- all of you on the good Earth.”
While circling the Moon, the crew photographed planned lunar landing sites, particularly the Sea of Tranquility, where the first touchdown was scheduled. After orbiting the Moon ten times, the trio prepared to fire the SPS engine again to begin the trip home. Like the lunar orbit insertion burn, this maneuver would take place when they were behind the Moon, out of touch with Mission Control. Apollo 8 emerged on schedule: Borman, Lovell and Anders were on their way home. Following an uneventful return voyage, Apollo 8 began preparations for the critical reentry maneuver.
Building speed as it “fell” towards the Earth, the CM would slam into the atmosphere at nearly 25,000 miles per hour. The angle of its approach was particularly critical. Too steep, and the spacecraft would drop too fast and burn up. Too shallow, and it would glance off the atmosphere back into space, dooming the crew. The astronauts had to hit a “reentry corridor” that was 400 miles wide by 26 miles high at an altitude of 80 miles above the Earth.
Apollo 8 hit the corridor precisely and traced a flaming arc across the sky. Outside, the heatshield reached a temperature of 5,000 degrees Fahrenheit, but inside the cabin remained comfortable. Apollo survived the fiery plunge. At 24,000 feet, two drogue parachutes deployed, followed by the three main canopies at 10,000 feet.
Apollo 8 splashed down in the Pacific Ocean on December 27, less than three miles from the waiting recovery ship U. S. S. Yorktown.
Next month’s installment of the “Season of Apollo” series will feature the Apollo Command and Service Module.