Content To Be Decided: NASA’s ‘C-Prime’ Decision

In a view never seen by human eyes before Christmas Eve 1968, the distant Earth rises above the lunar limb. The ‘C-Prime’ decision had paid off in spectacular fashion. Photo Credit: NASA

Seven has long been considered a lucky and mystical number. From the week of Creation in Christian tradition to the number of hills upon which Rome was built and from the Wonders of the Ancient World to its perceived status as a ‘perfect number’, it has been a mainstay in both Western and Eastern consciousness for thousands of years. More than four decades ago, as America strove to land a man on the Moon, the number also played a central part in the process to accomplish the most audacious engineering endeavour in human history. Seven steps had long been part of NASA’s plan to get from Earth orbit to planting boots on the lunar surface, but in August 1968 something remarkable happened…something which turned Apollo’s lucky seven steps on their head and changed history forever.

The original line-up for the missions to reach the Moon were labelled ‘A’ through to ‘G’. First would come unmanned test flights (‘A’) of the command and service module in Earth orbit, which was achieved by Apollo 4 in November 1967. Next, the ‘B’ mission, completed by Apollo 5 in January 1968, was detailed to undertake an unmanned shakedown of the lunar module. Manned flights commenced with the ‘C’ mission, involving the command and service modules in Earth orbit. The final steps were far more complex: ‘D’ was a manned demonstration of the entire lunar craft in Earth orbit, ‘E’ was a high-apogee mission, reaching an altitude of more than 4,000 miles, to test the command module’s re-entry systems and heat shield at near-lunar-return velocities, ‘F’ was a full dress rehearsal around the Moon…and ‘G’ was the long-awaited landing itself.

In March 1966, the first crews were assembled to support these missions. The Apollo 1 crew of Gus Grissom, Ed White and Roger Chaffee and the Apollo 2 crew of Wally Schirra, Donn Eisele and Walt Cunningham would complete the ‘C’ requirements. However, Schirra saw little sense in repeating the same mission and successfully lobbied for the removal of a second C mission; in early December his crew was renamed as Grissom’s backup team and a ‘new’ Apollo 2 was created to fulfil the D mission. Astronauts Jim McDivitt, Dave Scott and Rusty Schweickart had been the original Apollo 1 backups and McDivitt had worked extensively on the testing of the lunar module. These three men were thus assigned to the new Apollo 2. They would launch in the summer of 1967 atop a Saturn IB, after which a second Saturn IB would carry the lunar module into orbit and the pair would rendezvous, dock and perform a series of joint activities. Next up in late 1967 would be Apollo 3, with Frank Borman, Mike Collins and Bill Anders slated to perform the E mission.

Jubilantly relating the events of their mission after splashdown, astronauts Jim Lovell, Frank Borman and Bill Anders had secured their places in history. Lovell (left) was a late addition to Apollo 8; originally, he was on the backup crew, along with Neil Armstrong and Buzz Aldrin, but was moved onto the prime crew after Mike Collins required surgery in July 1968. Photo Credit: NASA

When Grissom’s crew lost their lives in a launch pad fire in January 1967, the other crews remained more or less intact. Schirra’s men would now perform the C mission, McDivitt’s team would execute D and Borman’s crew would fly E. The situation changed in July 1968, when Collins was playing handball…and realised that his legs did not seem to be functioning as they should. His condition steadily worsened. Whenever he walked down stairs, his knees buckled and he felt tingling and numbness.

With typical pilot’s reluctance, Collins sought the advice of the flight surgeon and was quickly referred to a neurologist. The diagnosis was that a bony growth between his fifth and sixth cervical vertebrae was pushing against his spinal column and to relieve the pressure the only corrective option was through surgery. A few days later, Collins underwent an ‘anterior cervical fusion’ procedure, in which the offending growth and some adjoining bone was removed and the two vertebrae were fused together with a small piece of bone from his hip. Flying the E mission was out of the question and Collins’ place was taken by fellow astronaut Jim Lovell.

By this time, the Saturn V booster had completed its triumphant maiden mission and some NASA managers were already talking about expediting the E mission from high-Earth orbit to a lunar distance. The mission’s baselined 4,000-mile apogee would be extended…to more than 240,000 miles. If approved, it would enable humanity’s first visit to another world.

The launch of Apollo 6 in April 1968 was one reason for the reluctance of senior NASA management to approve C-Prime. On this unmanned flight, the Saturn V experienced violent longitudinal oscillations, known as ‘pogo’, which Tom Paine, George Mueller and Jim Webb feared could cause structural damage and impair mission success. Photo Credit: NASA

Key figures in the plan to turn the E mission into something altogether more audacious included Chris Kraft, director of Flight Operations at the Manned Spacecraft Center (MSC) in Houston, and George Low, head of the Apollo Spacecraft Program Office. In April 1968, they proposed turning E into something called ‘E-Prime’, moving the test of the command, service and lunar modules from high-apogee Earth orbit to the vicinity of the Moon. However, the lunar module was experiencing its own development problems – particularly with relation to its troublesome descent and ascent engines – and it quickly became apparent that it would not be ready to fly until the spring of 1969.

It was Low who offered an alternative option that summer. Instead of E-Prime, a mission known as ‘C-Prime’ would be created. This would involve the launch of an Apollo command and service module, without a lunar module, towards the Moon in December 1968.

December 1968.

Less than five months away…

At a meeting in the office of MSC Director Bob Gilruth on 9 August, this astonishing plan was laid out in all its glory. The trajectory and navigation teams, together with the astronauts and their training personnel, could be ready for a December launch and actually entering the lunar sphere of influence would provide real data on orbital mechanics and the ability to develop better gravitational models.

“To Be Decided” was a phrase which remained part of NASA’s official vocabulary for Apollo 8 until after the safe return of Wally Schirra and the Apollo 7 crew. Options included a journey to lunar distance, with a circumlunar ‘loop’ or perhaps a fully orbital mission, with as many as ten circuits, under consideration. Image Credit: NASA

The first problem was NASA Administrator Jim Webb. He was in Vienna, with his Associate Administrator for Space Flight, George Mueller, at a conference at the time, and it was left to Deputy Administrator Tom Paine to conditionally approve the C-Prime plan. Paine was nervous, because the astronauts would need to be launched atop the Saturn V; although this had completed two unmanned missions, its most recent flight, Apollo 6 in April 1968, suffered severe longitudinal oscillations, known as ‘pogo’. He was also worried about the reliability of the Apollo service module’s large engine. However, Paine eventually approved the plan.

So did Mueller.

But Jim Webb wanted nothing to do with it.

In hindsight, Webb’s stance is understandable. He had led NASA through the trauma of the Apollo fire and did not want the agency to be hauled over the Congressional coals if C-Prime failed. Furthermore, in August 1968, Apollo had yet to be flown in Earth orbit with a human crew, let alone as far as the Moon. However, eventually, on the 16th, with many reservations, Webb was won over. Three days later, Apollo Program Director Sam Phillips formally set the wheels in motion. Until Wally Schirra’s crew had flown their Apollo 7 mission, C-Prime would be officially described as representing “an expansion of Apollo 7”, whose “exact content…had not been decided”.

Although the content of the Apollo 8 mission had not been officially decided, the crew certainly had been. On 10 August, Deke Slayton, the head of Flight Crew Operations, called Jim McDivitt into his office and told him that the flight order would be switched. McDivitt’s D mission, with the lunar module in Earth orbit, would become Apollo 9, preceded by Borman’s crew on C-Prime. At no point was McDivitt offered the chance to fly C-Prime. “Over the years,” he wrote in Slayton’s autobiography, Deke, “the story has grown to the point where people think I was offered the flight around the Moon, but turned it down. Not quite. I believe that if I’d thrown myself on the floor and begged to fly the C-Prime mission, Deke would have let us have it. But it was never really offered.”

The four months between the official endorsement of C-Prime and the launch of the mission proceeded at break-neck pace in terms of training and preparation. Here, inside a boilerplate command module, the Apollo 8 crew works through a simulation in October 1968. Frank Borman, saddled with the burden of command, is in the foreground. Photo Credit: NASA

It made sense. McDivitt had been working on the lunar module since late 1965 and his crew of Scott and Schweickart had trained exhaustively on its myriad rendezvous and test-flying commitments. They were best prepared to fly the D mission.

As for Frank Borman, he was at North American’s plant in Downey, California, working on tests of the command module for his E mission, when he received a telephone call. It was Slayton. He wanted Borman back in Houston, right away. Borman explained that he was busy on the spacecraft tests; could Slayton not speak over the phone? No, Slayton, replied, he had to see Borman in person. When Borman got back to Houston, Slayton sat him down and outlined the plan. Already, the CIA had intelligence that the Soviet Union was within weeks of testing its own gigantic lunar rocket. Then Slayton asked Borman if he would command C-Prime. It was a question with only one answer: Yes.

Shortly afterwards, CSM-103 – the command and service module originally assigned to the D mission, but now reassigned to C-Prime – arrived at Cape Kennedy for pre-flight processing. Until Apollo 7 was concluded, the mission was unofficially expected to perform either a circumlunar jaunt or achieve as many as ten orbits of the Moon. For Borman, ‘The Mission’ was all-important. “Some idiot had the idea that, on the way to the Moon, we’d do an EVA,” he told the NASA oral historian with incredulity. “What do you want to do? What’s the main objective? The main objective was to go to the Moon, do enough orbits so that they could do the tracking, be the pathfinders for Apollo 11 and get your ass home. Why complicate it?”

Almost four decades have passed since the call “Go for TLI” committed a team of astronauts to execute the Trans-Lunar Injection burn to chart a course through cislunar space and head for the Moon. The next generation owes it to the heroes of Apollo to return to a robust and vigorous programme of deep-space exploration. Photo Credit: NASA

The four months from August to December were conducted at break-neck pace, with the astronauts virtually living in the Apollo simulator and processing teams in Houston, Florida and elsewhere working around-the-clock, seven days per week, to accomplish C-Prime. The progress made by America in just a handful of years was amply illustrated by an unexpected guest at the Cape Kennedy crew quarters on 20 December, the night before launch. It was Charles Lindbergh, the first man to fly solo across the Atlantic. The legendary aviator and humanity’s first three lunar voyagers – Borman, Lovell and Anders – talked for a time. Then Lindbergh was quiet for a moment. Finally, he spoke.

“You know,” he said quietly, “in the first second of your flight tomorrow, you’ll burn more than ten times more fuel than I did all the way to Paris!”

Four decades after Lindbergh’s flight, it was indeed remarkable how far human technological prowess had advanced. No more than a handful of years earlier, American rockets had exploded more often than succeeded, and a little more than 2,400 days had passed since Al Shepard embarked on a suborbital ‘hop’ in a Mercury capsule. The gutsiness of Chris Kraft and George Low, Tom Paine and George Mueller, Sam Phillips and the astronauts of C-Prime – the men who earned eternal fame as the crew of Apollo 8 – can hardly be underestimated. Back then, as today, with the recent landing of the Mars Science Laboratory, ‘Curiosity’, NASA was demonstrably filled with the best and brightest scientists, engineers, thinkers and technicians of a generation.

As with Curiosity’s recent triumph, Apollo 8 was measured not by words, but by deeds. On Apollo 8, that deed was accomplished in spectacular style. Its achievement directly enabled the first human bootprints on the Moon, a little more than six months later. And its reverberations into the present era are just as strong as they were in 1968. Despite the Obama administration’s insistence upon destinations other than the Moon, internal NASA documentation indicates that one of the earliest missions of the Space Launch System (SLS), perhaps as early as 2019, may once again send humans around the Moon.

“The exact content…had not been decided.” Those words echo with renewed vigour as humanity stands on the brink of perhaps the greatest era of exploration it has ever known. Future exploration beyond low-Earth orbit demands nothing less than the visionaries and ‘can-do’ achievers which continue to form the very heart and stomach of NASA’s proud workforce. Forty-four years ago, this month, the most audacious plan in human history – a plan which carried immense risk, yet balanced against enormous reward – was laid and its groundwork led to something truly remarkable. It can be hoped that NASA’s next steps beyond Earth orbit will be no less bold.

The heroes of Apollo deserve nothing less.


This is part of a series of History articles which will appear each weekend, barring any major news stories. Next week’s article will focus upon Mission 51I, a Shuttle flight in 1985 which triumphantly salvaged a crippled satellite and restored it to health.

Missions » Apollo »


  1. Good article, it’s always interesting to revisit the circumstances behind the C-Prime decision. With the severe pogo problems on Apollo 6, it was a remarkable show of confidence in Von Braun’s team at Marshall, to go ahead with the first manned Saturn V launch. I wonder if the decision would have been the same if the US didn’t have pictures of the Soviet N-1 on the launch pad. After the tragedy of Apollo 1, it sure didn’t take long for NASA to come down with “Go Fever” all over again, didn’t it?

  2. Thank you both for your comments. However, I think ‘boldness’ had everything to do with it in the case of Apollo 8, both before and after the outcome. Barely 18 months had elapsed since the Apollo 1 fire, the Saturn V had suffered potentially damaging pogo which hampered its reliability in the eyes of senior managers and Apollo 7 had yet to fly. To make the decision that was made in August 1968 ‘was’ a bold one.

ISS Boost Ended Earlier Than Planned

MSL’s Descent Captured Via MARDI