Fifty years ago, a space mission lifted off that would change our world forever. Born in the depths of the Cold War and launched at a time of national turmoil, Apollo 8 was more than a great scientific and engineering feat. Sending three men to circle the Moon in a fragile capsule involved a string of achievements – they became the first human beings to see the Earth from space as an entire planet, traveled farther from home than anyone in history, and in the process all but ended the Space Race. As you might expect, the story of Apollo 8 is a fascinating one.

When Apollo 8 lifted off from what was then called Cape Kennedy on December 21, 1968, the world was in turmoil. The Cold War was still very much a reality as the West and East fought to determine if the world would be dominated by free-market democracy or totalitarian socialism. Political reforms in Czechoslovakia were met with brutal suppression by Soviet forces. In the West, Paris was plagued by riots and the United States was shocked and polarized by protests against the impasse of the Vietnam War and racial inequality, as well as a series of horrific assassinations.

Even NASA seemed to be trapped in a crisis of confidence. On January 27, 1967, the space program suffered a devastating setback when the crew of Apollo 1 died in a tragic launchpad fire. The subsequent investigation revealed a frightening litany of design flaws, assembly errors, and general mismanagement, but the impact that it had on the space agency's morale and the spirit of the nation when it came to the Space Race would be hard to exaggerate.

This changed on October 11, 1968 when Apollo 7 lifted off from Cape Canaveral. The first flight of the Apollo Command Service Module (CSM), it was just a 10-day flight in low Earth orbit, but the success of the mission and the safe return of the three-man crew was a tremendous boost to both NASA and the public.

But what wasn't known, even to most people on the Apollo project, was that Apollo 7 had a hidden agenda – one that had a profound impact on the Space Race, the Cold War, and history itself.

By 1968, the Apollo program had settled on a plan for reaching the Moon before the end of the decade. After years of back and forth planning, NASA settled on using a giant Saturn V booster bigger than the Statue of Liberty that would launch into orbit carrying two spacecraft.

The first was the Command Service Module, (CSM), which was the main vehicle. The Command Module was the home for the astronauts, the command and control center for the mission, and the reentry vehicle to return the Earth. Meanwhile, the Service Module, which was mated to the Command Module, provided water, electricity, long-range communications and, most important, carried the main engine to place the spacecraft into lunar orbit and returning it to Earth.

For actually landing on the Moon, a second vehicle was required, the Lunar Excursion Module (LEM). This spider-like machine could only operate in the vacuum of space and would be carried to the Moon by the CSM. Two astronauts would then transfer to the LEM, which would undock and descend to the lunar surface while the Command Module Pilot remained with the mothership.

This meant that the early Apollo missions would be a series of baby steps as the astronauts rehearsed the skills needed for operating the CSM/LEM combination. The original plan was that Apollo 7 would test the CSM in low Earth orbit. Apollo 8 would follow with the CSM and the LEM, then Apollo 9 would fly the CSM and LEM to an altitude of 4,600 mi (7,400 km). It would not be until well into 1969 that Apollo 10 made the first flight to orbit the Moon, where it would test the LEM under lunar gravitational conditions in rehearsal for the Apollo 11 landing.

There was only one problem with this neat timetable. By the time Apollo 8 was on the launch pad, the LEM wouldn't be ready to fly.

Built by Grumman Aircraft, the LEM was an engineer's problem child. No one had ever built a craft that was meant to land from space using nothing but rocket power – much less one to do so on the Moon. Any such undertaking was bound to have setbacks and the LEM had them in spades.

In July 1968, the first LEM was delivered to Cape Kennedy. On inspection, it turned out to be full of defects and weighed so much that the landing legs couldn't support it. A final assessment showed that, at best, the lunar lander wouldn't be fit to fly until February 1969.

The question was, what to do? The Soviets weren't standing still and there was every reason to believe that they were gearing up to put a man on the Moon as soon as possible. Without the LEM, Apollo 8 couldn't fly, which would set back the program by months.

Forget the LEM

No one knows who had the idea first, but it was NASA administrator George Low who championed it. He said to forget the low orbit test, forget the LEM, forget the slow, but sure approach. In 16 weeks, send Apollo 8 directly to orbit the Moon.

It was an audacious idea – even more so when you understand how NASA really worked in the 1960s. From the political side, only a handful of officials at the agency knew about Low's idea. Even the top brass of NASA were in the dark at first, and Congress definitely were, until those behind the idea were absolutely sure it was feasible and that they could get support for it.

On the technical side, the shift seemed insane. We like to think of NASA as a cool, calculating organization where everyone checks everything to 10 decimal places before doing anything. There's a lot of truth to that, but during the Space Race, the scientists and engineers weren't just racing to beat the clock, they were also dealing with huge unknowns. In fact, half the time they were making things up as they went along and every mission was an exercise in problem solving and improvisation on the spot.

What these two factors meant was that changing Apollo 8 wasn't a matter of rewriting a couple of diary entries. It was like a general shifting a planned invasion to a completely different continent. Even if everyone was onboard with the idea, the logistics were staggering.

For example, if Apollo 8 was going directly to the Moon, that would require swapping the crews of Apollo 8 and 9. The original Apollo 8 crew were much more advanced in their LEM training and this would have been wasted by leaving the lander behind. On the other hand, the original Apollo 9 crew were further ahead on the CSM training and, equally important, the mission Commander, Frank Borman, had been part of the Apollo 1 investigation and was intimately familiar with safety issues.

Soon, Apollo 8 had its new crew, the Commander was Frank F. Borman II, a US Air Force Colonel who had already commanded the Gemini VII mission. This made him particularly desirable as Gemini VII had lasted as long as a lunar mission would.

Also a veteran of Gemini VII was Command Module Pilot and Navigator James A. Lovell Jr. He'd also flown on the Gemini XII mission and was a replacement for Michael Collins, who was temporarily grounded due to surgery for bone spurs. Rounding out the crew was Lunar Module Pilot William A. Anders. Since there was no LEM for him to pilot, he would act as flight engineer and official photographer.

We need a rocket

But the crew wouldn't be much use if Apollo 8 didn't have the rocket it needed to get to the Moon. The original booster was supposed to be a Saturn Saturn 1B, but now the giant Saturn V was required. That meant getting the legendary rocket pioneer and father of the Saturn, Wernher Von Braun on side.

In the end, Von Braun was delighted by the idea, but there was still a lot of work to be done. The first two Saturn V flights had been uneven. The first had come off without a hitch, and the second had some serious problems, but Von Braun was the determined to make the third perfect. But this meant solving problems like the tendency of the second stage to "pogo" or start to vibrate dangerously in flight. That meant that even as the Saturn V earmarked for Apollo 8 was being assembled in Florida, an intensive program of ground testing was started in Huntsville, Alabama.

And then there were the computer calculations that needed to be done. First there were the calculations to show that the mission was possible, then there were the calculations to find the best launch date and time, and then there were the mind-bogglingly complex calculations of the orbits for the spacecraft getting to the Moon and back safely.

Finally, there was Apollo 7. Even after the engineers, the astronauts, the top brass at NASA, and the government up to the President were in agreement, if Apollo 7 failed, then it was all off. But Apollo 7 did launch, it did come back, and it was declared a success. On November 12, just three weeks after Apollo 7, the public announcement was made that Apollo 8 was going to the Moon.

The launch date was December 21, 1968 at 7:51 am EST from pad LC-39A at the Kennedy Space Center. That was less than 40 days away.

Mission objectives

Aside from getting to the Moon in and of itself, the primary goal of Apollo 8 was to get there before the Soviets. To some, that may seem childish, but it's important to remember that Apollo was not first and foremost about exploration or adventure or science. It was a battle in the Cold War and Apollo 8 Commander Borman saw it in that light. To him, this was a real war and he was fighting it just as much as if he was in a bomber.

This was very much on NASA's mind as the Soviets launched their Zond 5 mission on September 15, 1968, followed by Zond 6 On November 10. Instead of cosmonauts, these unmanned circumlunar probes carried a payload of tortoises and other living things. The Soviets saw these missions as the precursors to a manned mission, and if they had been successful, Apollo 8 might have lost the race.

However, while Zond 5 returned safely to Earth, Zond 6 suffered a malfunction and crashed, delaying the Soviets. Still, the Americans could see that the clock was ticking.

The second objective, and one that helped get approval for Apollo 8, was to conduct a detailed photographic survey of the equatorial regions of the Moon. Even though the near side of the lunar surface had been photographed from Earth for decades, and both the Americans and the Russians had sent probes and orbiters to the Moon in recent years, the results left much to be desired.

Earthbound telescopes could only achieve so much and the electronic imagers used by the spacecraft were painfully primitive even by the standards of the day. A human being with a standard camera loaded with emulsive film was streets ahead and could return the photos needed to find the landing sites for later Apollo missions.

The photos would also help with the third major objective. One disturbing phenomenon that the orbiter missions had discovered was that the gravitational field of the Moon was uneven. This was due to mascons, or concentrations of dense matter resulting from asteroid impacts.

These gravitational anomalies messed with NASA calculations, throwing trajectories off by as much as two miles. Apollo 8's photos and telemetry would help scientists to accurately plot the spacecraft's orbit, allowing them to map the mascons and develop a new set of empirical formulae for future mission navigation.

The dangers of going boldly

But there were dangers for Apollo 8 that the original plan didn't include. The single most important piece of equipment on the CSM was the Service Propulsion System (SPS). That's the main engine and can be seen as the huge bell that sticks out of the stern of the Service Module. This chemical rocket engine would provide the necessary thrust to place Apollo 8 into lunar orbit and send it home again.

The SPS was made as simple as possible. Instead of a complicated line of breakdown-prone pumps, the propellants were pushed through the system by helium and the engine burned hydrazine and tetroxide, which are hypergolic. That is, they don't need an ignitor – the moment they come into contact with each other, they burst into flame. That makes them nasty to handle on the ground, but ideal in space.

The problem was that even with all this fool-proofing, there was only a 50/50 chance that it would work as advertised. If the SPS failed while in lunar orbit, the CSM would be trapped in orbit. In the original mission plan, this wasn't as big a problem because the engines on the LEM could do the job in an emergency. But there wasn't a LEM.

Launch

The lead up to the launch date was almost surreal for the astronauts and their families. On top of the constant training, testing, and anxieties of any spaceflight were piled the attention of the world's press that made the crew's children and wives veritable prisoners in their homes, combined with a White House reception in the middle of an outbreak of the Hong Kong flu that didn't make NASA's flight surgeons very happy.

The night before launch, the three astronauts even had a visit from Charles Lindbergh, the controversial first man to fly solo across the Atlantic Ocean in 1927. While talking to them, the air pioneer made some back of the envelope calculations and said that Apollo 8 would burn 10 times more fuel in the first second of lift off than Lindbergh's Spirit of St Louis did on its entire flight.

On December 21, 1968, the Saturn V SA-503 rocket lifted off on time and without any major malfunctions. After the S-IVB third stage separated, it carried the CSM into an 90-minute orbit 100 miles (160 km) above the Earth. For two hours and 38 minutes, mission control intensely studied telemetry from the booster and the spacecraft before giving the green light for Trans Lunar Insertion (TLI).

Moonward bound

Two hours, 44 minutes, and 30 seconds into the flight, the single engine on the S-IVB fired again for 318 seconds guided by ground computer control, sending it and Apollo 8 on their way to the Moon. Apollo 8 was now moving faster than any human being had ever experienced before at 24,208 mph (38,959 km/h). At the three hour and 35 minute mark, they passed the previous high altitude record of 850.5 miles (1,368.9 km) set by Pete Conrad and Richard Gordon in Apollo XI in 1966.

The three men were farther from home than anyone had ever been.

But Borman and his crew had little time to reflect on this. There was the business of firing the explosive bolts for separating from the S-IVB, the maneuvering to avoid any chance of collision with the rocket, then turning around to monitor the venting of the remaining fuel from the S-IVB's tanks.

Unfortunately, the violent separation didn't do the third stage any good and Borman watched with growing concern as the S-IVB started squirting gases every which way. He wanted to cut the inspection short and keep as far away as he could from the rocket, which might have ended up traveling in any direction.

In the end, the venting was safely achieved, sending the S-IVB on a slingshot orbit around the Moon and into solar orbit. Today, it's one of only five surviving S-IVBs and the only flown one. All the others were burned up in the Earth's atmosphere, crashed into the Moon, or are in museums.

But more significantly, as the Apollo 8 crew turned to watch their booster, they became the first human beings to see the Earth as an entire planet. Even previous space missions could only see the Earth as a giant arc. For the first time, it could now be seen as a globe hanging all alone in the darkness of space.

En route to the Moon

In many ways, Apollo 8 was very different from any previous space mission. There was much less tension than previous flights. NASA tended to micromanage orbital missions with each additional orbit requiring explicit permission and every technical issue discussed in detail. Apollo 8, on the other hand, could not abort once it entered translunar orbit. Even in the most urgent emergency, it wasn't coming home for a week, so there was no point in mission control playing mother hen all the time.

In addition, the Command Module had much more room than other space capsules. It was still like spending two weeks inside an SUV, but it beat being crammed into a can-like cockpit where you couldn't even stretch out straight. There was also a better choice of food and hot water for reconstituting meals and making hot drinks.

And then there was the incredible view. In order to maintain an even temperature and keep the high-gain antenna properly aimed, Apollo 8 was flying backwards and, ironically, the crew never saw the Moon once on the leg out. But they could see the Earth and, as work permitted, the astronauts enjoyed looking back at home.

Another thing that was different was that when they'd achieved TLI, there was no need for the astronauts to wear their bulky space suits, which were stowed away and not even worn for reentry. Instead, the three men wore much more comfortable lightweight flight suits. However, they had to keep on their black and white Snoopy hats because their communications headsets wouldn't stay put.

But not everything was pleasant. Shortly after TLI, Borman took a sleeping pill to help him rest, only to find himself vomiting and suffering a diarrhea attack. As one can imagine, this is even more unpleasant in the confines of a space capsule in zero gravity. Flight surgeons were alarmed, but Borman's condition soon cleared up. Either it was a 24-hour flu, a reaction to the sleeping pill, or an early case of space sickness.

Another health concern were the Van Allen radiation belts that extend up to 15,000 miles (24,000 km) from Earth. These magnetic bands have a high radiation level, but Apollo 8 flew through them so quickly that the crew received only about the equivalent of one chest X-ray – well within safe limits. In all, the astronauts only took a radiation dose of 1.6 mGy for the entire voyage. The average person back on Earth receives up to 3 mGy per year.

A more immediate concern was that Apollo 8 was the first space mission where the crew had to handle navigation. On previous flights, ground tracking stations handled the problems of where the spacecraft was and where it was going, and even in the worst case scenarios, the astronauts could return to Earth inside an hour. But on the lunar mission, the capsule would be out of communication with mission control as it passed behind the Moon and if communications failed entirely, the crew would have to take over all navigation.

Because of this, Lovell spent a large part of the mission down at the navigation station in the stern of the craft taking star sights through the sextant and comparing his results with those from Earth. These fixes were more than just routine. A spaceflight trajectory isn't a precise calculation, but a series of increasingly better estimates, and the data that Lovell collected, helped the computers to zero in on exactly what Apollo 8's orbit was.

Another duty the astronauts had to perform was that of television hosts. Up to seven live transmissions were scheduled during the course of the mission and the increasing distance, time lag, and low bandwidth didn't help any. The first such transmission was a bit shaky with the crew having difficulty setting up the camera, with an attempt to show the Earth from space revealing only a blurry ball of light. But they did provide a tour of their space home and the 17-minute show was well received by the public.

One of the key tasks that the crew had to handle was testing the Service Propulsion System (SPS). It was the single most important system on the craft, so NASA insisted on testing it before reaching the Moon. It was lucky they did because the crew found that the helium used to push the fuel along the pipes had filled the feeds with bubbles, resulting in the engine firing like a sputtering car. Fortunately, the first test cleared the bubbles out, but it didn't bear thinking what would have happened if those bubbles had still been there when Apollo 8 reached the Moon.

Lunar Orbit Insertion

About 64 hours into the mission, Apollo 8, still flying stern-first, was approaching the most dramatic part of the voyage – Lunar Orbit Insertion (LOI). This would involve firing the SPS for four minutes and 13 seconds and the computer-controlled timing had to be exact. Too short a burn, and the spacecraft could be hurled into orbit around the Sun. Too long, and the mission would end with a crash into the lunar surface.

What was so unnerving was that the maneuver had to be done while Apollo 8 was behind the Moon and out of contact with Earth. This meant that mission control and the entire world would have no choice but wait for transmission from the spacecraft to resume. If they didn't, the worst had occurred.

Meanwhile, Jim Lovell became the first human being in history to see the far side of the Moon with his own eyes. Ten minutes before the engine burn, Lovell could see the first shafts of light as they sped toward the sunlight side of the Moon, then he could see what had only been photographed by unmanned probes. By this time, there were only two minutes until ignition.

On December 24, at the 69 hour, 8 minute mark of the flight, the engines fired for what the astronauts later called the longest four minutes in history. But under the guidance of the watchful onboard computer, the burn was successful and Apollo 8 went into an orbit that would last for the next 20 hours and 10 revolutions.

At the predicted second, mission control received the signal from the CSM that the first persons sent to another world had arrived.

The crew of Apollo 8 also set a new record as the farthest anyone had ever traveled from Earth – 234,474 mi (377,349 km). But what the people back home wanted to know was, what was the Moon like? Jim Lovell had the honor of telling them.

"Okay, Houston," said Lovell. "The Moon is essentially gray, no color; looks like plaster of Paris or sort of a grayish beach sand. We can see quite a bit of detail. The Sea of Fertility doesn't stand out as well here as it does back on Earth. There's not as much contrast between that and the surrounding craters. The craters are all rounded off. There's quite a few of them, some of them are newer. Many of them look like – especially the round ones – look like hit by meteorites or projectiles of some sort. Langrenus is quite a huge crater; it's got a central cone to it. The walls of the crater are terraced, about six or seven different terraces on the way down."

Now the main task of the mission began: to photograph the lunar surface and help scout out the best spots to set down the later Apollo mission. As official photographer, Bill Anders busily swapped out cameras as he took pictures out the window While Lovell used the the sextant as a telescope. By the time they finished, they had 700 pictures of the Moon and five reels of 16 mm film.

Earthrise

Incredibly, the most famous photo from Apollo 8 happened almost by accident. NASA was so intent on reconnoitering the Moon that they gave no thought about the Earth, but on the fourth orbit, the spacecraft was oriented so that the crew had their first clear view of the horizon and the Earth rising from it.

Borman exclaimed, "Oh, my God! Look at that picture over there! Here's the Earth coming up. Wow, is that pretty!" At first all three men were stunned by the sight, but then Anders and Lovell scrambled to get color film into a camera and take the shot that for generations has reminded us how small and lonely our planet is.

Very soon, all the excitement was taking its toll on the highly motivated astronauts and Borman ordered Lovell and Anders to sleep through the next two orbits while the cameras were set on automatic.

Christmas at the Moon

The ninth orbit marked another historical event as Apollo 8 made what was one of the most watched television broadcasts in history. It's estimated that one quarter of the Earth's population – a billion people – saw the Christmas broadcast either live, delayed, or heard it on the radio. During this, the three astronauts sent greetings to those back home and read from the first chapter of Genesis before signing off with: "And from the crew of Apollo 8, we close with good night, good luck, a Merry Christmas and God bless all of you — all of you on the good Earth."

Trans-Earth Injection

But the astronauts didn't get Christmas day off. Two and a half hours after the broadcast, it was time to return home. As with the arrival, the Trans-Earth Injection (TEI) burn took place while the spacecraft was behind the Moon. For most people on Earth, this seemed like an anti-climax, but for NASA and the astronauts' families, this was the most frightening part.

If the SPS had failed to fire entirely during the first burn, Apollo 8 would have simply arced around the Moon and coasted back to Earth. But once in lunar orbit, if the SPS failed, the crew would be trapped in lunar orbit, and the Command Module would become their tomb.

Small wonder that everyone involved breathed a sigh of relief when at 89 hours, 28 minutes and 39 sec into the mission, mission control heard Lovell say, "Please be informed, there is a Santa Claus."

Coasting home

For the next two and half days, Apollo 8 was on its way back to Earth. The crew made another television broadcast and enjoyed a Christmas dinner that had been packed for them. This included three airline-size bottles of Brandy, which Borman ordered be left unopened until after landing.

Perhaps this was for the best because, though it seemed like the safest part of the mission, space is still a dangerous place. As if to remind everyone, Lovell accidentally entered the wrong commands into the computer, making it think it was still on the launch pad and it fired the thrusters to set the craft "upright." The problem was soon corrected after considerable debugging, but it showed that even going home, things could go seriously wrong.

Reentry

On December 27, the Command Module fired its explosive bolts and separated from the Service Module. It was another white-knuckle moment, because a manned spacecraft had never hit the Earth's atmosphere at interplanetary speeds before. Under computer control and with Borman ready to take over, the craft did a maneuver where it skipped like a stone on the atmosphere to slow it down. The aerodynamic characteristics of the capsule gave it some lift and it could, within limits, be flown, but the astronauts were still hit with six times the force of gravity.

At 30,000 feet (9,1000 m) the drogue parachute deployed followed by the three main parachutes at 10,000 feet. On December 27 at 10:51 am EST, Apollo 8 splashed down in the North Pacific Ocean just south of the Hawaiian Islands. The capsule was floating upside down, but Borman deployed the floats that quickly righted it.

Forty-three minutes later, the first US Navy frogman arrived. Forty-five minutes after that, the crew of Apollo 8 were standing on the deck of the carrier USS Yorktown.

Aftermath

Apollo 8 was so successful that even the Soviets sent sincere, if grudging congratulations as they realized that they'd lost the Space Race. Unless there was a major mishap, the Americans would be on the Moon within months. Time magazine named the crew "Men of the Year" and the space television broadcasts won an Emmy Award.

At the time, there was a rumor that Borman would be given command of Apollo 11, but he felt that he'd won his Cold War battle and he eventually opted for a career in private industry, as did Anders after serving as executive secretary of the National Aeronautics and Space Council. Only Lovell remained on the mission roster and ended up as the commander of the ill-fated Apollo 13 mission.

Like the voyages of Columbus or Captain Cook, Apollo 8 was undoubtedly a milestone in the annals of human history. However, it did have a more immediate impact. It was a major American victory in the Cold War, it rapidly increased our understanding of the Moon, and it paved the way for the landing of the first men on the Moon in 1969.

But beyond all this, perhaps its greatest achievement is summed up in one little photograph of the Earth rising above the horizon of a dead world, showing our blue, cloud-covered planet hovering in the vast blackness of space and reminding us that this is our home. Perhaps it says something that one of humanity's greatest scientific and engineering achievements left its most profound impact in that single poetic image.

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