Apollo 8 Earthrise

After the success of Apollo 7 in October 1968, the first test flight of the Apollo Command and Service Module (CSM), NASA announced a bold plan for Apollo 8. This flight, which would be the first manned flight of the Saturn V booster, 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, Apollo 8, piloted by Frank Borman, James Lovell and William Anders, would orbit the moon!

Planning for the circumlunar flight began with a proposal in early August 1968 by NASA Manned Spacecraft Center Deputy Director George M. Low 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 going into orbit around the moon.

Wernher von Braun felt there was little difference as far as the Saturn booster was concerned whether the CSM went into lunar orbit versus the circumlunar proposal; NASA’s Chief Astronaut Deke Slayton believed taking this step was the only way to build enough experience to reach the moon before the end of 1969. Others concurred, contingent upon a successful Apollo 7 flight. With the CSM proven in earth orbit, the group endorsed the plan. Their recommendation went to Acting NASA Administrator Thomas O. Paine. (He became Acting Administrator when James Webb, who had headed the agency for 8 years, retired on August 6.)

There was a political factor affecting their decision as well.  The Central Intelligence Agency reported the Soviets were preparing for a manned Zond flight by the end of the year.  On November 10, they launched Zond 6. Like its predecessor, it looped around the moon, but then flew a radically different reentry approach than Zond 5 had. Zond 6 reentered the atmosphere over the South Pole, skipped back into space then descended a second time for a landing in the Soviet Union.

The g-loading on Zond 5 had been too high for a human crew, but the skip maneuver kept Zond 6’s to a tolerable 4 – 7gs. The flight proceeded well up until the very end. Zond 6’s parachute released prematurely and the craft was badly damaged on landing, but this fact was unknown in the West at the time. A manned flight was expected at the next lunar launch window, which would begin on December 8 for the Baikonur Cosmodrome.

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 would begin December 21. It looked like it would be a neck to neck race to see which nation would send a crew around the moon first.

NASA employees and contractors worked feverishly to prepare Apollo 8. When mid December passed with no Soviet launch, everyone who knew of the CIA report breathed a sigh of relief.  Unknown in the west, after the problems with Zond 6, Vasily Mishin (head of the Soviet design bureau responsible for their manned space program) indefinitely postponed any plans for a piloted circumlunar flight. The Soviets had an L-1, the manned version of the Zond and a Proton booster in the assembly hall at the launch site, but never attempted a launch. Once Apollo 8 took Borman, Lovell, and Anders around the moon, the Soviets quietly canceled the L-1 mission rather than be second.  (Interestingly, the Mission Planner’s Manual for the Proton booster published by the Space Commerce Corporation in 1989 shows that Proton flight #13 was supposed to carry a “manned Zond one man” but was “scrubbed” on December 17, 1968.)

Borman, Lovell and Anders began their flight on December 21, 1968. Gemini 7 veterans Borman and Lovell compared the Saturn V’s lift off to the Titan II. Anders said it felt “like an old freight train going down a bad track.” Despite the tremendous power of the Saturn, acceleration during boost did not exceed 4 g’s. Two and a half minutes after launch, all the propellants in the S-IC first stage were exhausted and the stage was discarded. It had consumed 202,000 gallons of RP-1 kerosene and 329,000 gallons of liquid oxygen. The weight of the propellants used in just the first 151 seconds of the flight was 4.4 million pounds.

The S-II took over. Two minutes later the center engine cut out, which was planned this time, to keep acceleration within the 4-g level. Eight minutes, forty seconds after launch, the S-II was discarded. All three agreed that the S-II ride was rough and were glad when the second stage was finished. The third stage placed them in a parking orbit and they checked the CSM and S-IVB to make sure everything was ready for the “translunar injection,” or TLI, burn.

After a revolution and a half, 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 S-IVB fired for the second time. When it quit five minutes later, the astronauts were traveling 24,400 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.  Apollo 8 was on its way to the moon!

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, they fired the Service Module 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 was an added safety feature of sorts. 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. However, if the burn had not taken place, they would emerge sooner than if it succeeded. 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.

Among the highlights for viewers on earth were the live television transmissions from the spacecraft. The crew carried a 4.5 pound black and white television camera they used to broadcast images several times during the flight. 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: “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 right on schedule: Borman, Lovell and Anders were on their way home.  Following an uneventful return voyage, the Apollo 8 astronauts 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, its SM discarded, hit the corridor precisely and traced a flaming arc across the sky. Twice, the craft was rolled to create lift to skip back up and control the descent.  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, three drogue parachutes deployed, followed by the three main canopies at 10,000 feet.

Apollo 8 splashed down in the Pacific Ocean, less than three miles from the waiting recovery ship USS Yorktown. The landing was actually a bit too precise for comfort. While under canopy, it drifted over the aircraft carrier. NASA officials decided that, in the future, the recovery ships would position themselves a few miles from the center of the target point.

Written by Greg Kennedy on December 20th, 2013 , Space History

Leave a Reply

Your email address will not be published. Required fields are marked *