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The Launchbox, PoD 5: Christmas Catastrophe - the Disaster of Apollo 8

By Andy Cooke


On Christmas Day, 1968, Apollo 8 entered lunar orbit smoothly - the first manned spacecraft to reach the Moon.


It was the moment that NASA truly recovered from the Fire, and the point where the Space Race was all-but-won. The first true deep-space mission, which blazed the trail to the Moon, proved that people could travel from the Earth to the Moon, returned the famous "Earthrise" photo, and, in the words of an anonymous correspondent, "saved 1968."


And it could have been the worst moment in NASA's history.


The Route to the Moon

As mentioned in the last article, the original plan for the route to landing men on the Moon was an alphabetic series of missions. Each class of mission had to be mastered before the next could be attempted. Ideally, each class would take one mission to master, but it was very possible for multiple missions to be needed.


The Apollo Command-and-Service-Module (CSM) in orbit around the Moon
  • A-mission: Unmanned tests of the launch vehicles (Saturn V rocket) and Command-and-Service-Module (CSM) to prove them ready for manned missions. Carried out on Apollo 4 and Apollo 6

  • B-mission: Unmanned test of the Lunar Module (LM). Carried out on Apollo 5

  • C-mission: Manned test of the CSM in Low Earth Orbit (planned for Apollo 7)

  • D-mission: Manned test of the entire spacecraft assembly (CSM plus LM) in Low Earth Orbit (Planned for Apollo 8)

The Apollo Lunar Module (LM) on the surface of the Moon
  • E-mission: Repeat of manned test of entire spacecraft assembly in High Earth Orbit (Planned for Apollo 9)

  • F-mission: Manned test of entire spacecraft assembly in lunar orbit; full "dress rehearsal" (Planned for Apollo 10)

  • G-mission: First lunar landing (Planned for Apollo 11)

Future lunar missions would be H-class (pinpoint landings - Apollos 12, 13, 14, 15), I-class (lunar science observation - not yet assigned, but potential to do so), and J-class (detailed lunar surface science missions Apollos 16, 17, 18, 19, 20, and 21)


Deke Slayton, head of the Astronaut Office and the man who assigned crews to missions, had developed a "rotation" system during Gemini: when assigned to a backup crew, you could usually rely on being named to the prime crew of the mission three missions later. That is, if you backed up Gemini 3, you would probably fly Gemini 6. Further more, junior members of the crew would likely be named to the backup crew for the mission three after that (eg Gemini 9), which meant they would be in prime position to fly the mission three after that (Gemini 12). This could, of course, also be altered by missions being redesignated or shuffled around, but astronauts were always eager to get into the rotation.


Apollo 7 was assigned to Wally Schirra (one of the last Original Seven astronauts to be still flying), Walt Cunningham, and Don Eisele, with backup crew being Tom Stafford, John Young, and Gene Cernan. The latter three were therefore effectively pencilled in for Apollo 10.


Apollo 8 was assigned to Jim McDivitt, Dave Scott, and Rusty Schweickart, backed up by Pete Conrad, Dick Gordon, and Al Bean. If all went well, Conrad, Gordon and Bean would fly the Apollo 11 flight, pencilled in for the G-mission, and Pete Conrad would be the first man on the Moon.


Apollo 9 was assigned to Frank Borman, Mike Collins, and Bill Anders, backed up by Neil Armstrong, Jim Lovell, and Buzz Aldrin. However, in mid-1968, Mike Collins needed surgery and was pulled off the mission. Jim Lovell moved from backup to main crew, Buzz Aldrin shifted from being backup LM pilot to backup CM pilot, and Fred Haise was brought in to cover the LM, although it was understood that Mike Collins would come back into the rotation in Haise's place after his surgery (Haise, however, was told he'd be backup crew when Armstrong, Aldrin, and Collins flew their prime mission on Apollo 12).


Delays and Decision


The LM for Apollo 5 being mated with the Spacecraft Adapter

Despite Apollo 5 being deemed a success with no further B-mission needed, the LM wasn't in a good place as 1968 wore on. Issues with all elements of it abounded, but, most alarmingly, with the rocket engines. Although NASA didn't want a second B-mission, they did want the LM to be perfect prior to flight, and it was delayed again and again and again. It wouldn't be ready to fly until early 1969.


Meanwhile, following the disaster of Soyuz 1, which killed Vladimir Komarov, the Soviet space programme was showing signs of recovery. They were flying unmanned test articles again - and even a stripped-down version, called Zond, which could be thrown into a lunar-flyby trajectory by the existing Soviet Proton rocket. And a test flight of such had been carried out in March 1968, albeit with re-entry problems.


There was concern at NASA - if the Soviets managed to pull off yet another first in sending a cosmonaut around the Moon - far further out than any manned mission ever before - they might claim victory in the Space Race. Although the last steps - entering lunar orbit, descending to the surface, landing, and recovery to the Earth - were major challenges, the public might not see it that way. Getting to the Moon is getting to the Moon.


But the LM wasn't ready. It had fallen even further behind schedule and wouldn't be ready in time for the December launch window. But then, George Low, Apollo Programme Manager, suggested re-purposing Apollo 8 to carry out a second test of the CSM (another C-mission) - but looping it around the Moon. He checked with Wehrner von Braun, who shrugged and said that when you put men on the Saturn V, it didn't matter how far you wanted to send them; they'd get there. Low suggested it to NASA Administrator Jim Webb - who promptly blew his top.


"Are you out of your mind?!"


They hadn't even flown the first C-mission yet, and Low was proposing a deep-space mission immediately, and without the LM - which was regarded as a potential "lifeboat" in case anything happened with the CSM life support systems, guidance systems, maneouvering systems, or even - potentially - the SM main engine.


But Webb came around, after weeks of patient work showing it was possible. Risky, but possible.


The Switch

When the decision was made, Deke Slayton consulted Jim McDivitt, but McDivitt did not want to give up the first test flight of the LM for a "glorified sight-seeing trip". Slayton accepted his logic and suggested he and Borman's crews swap missions - if Borman was amenable.


Borman agreed instantly. Not only would he get to command the first true lunar mission of any type, he feared the Soviets would snatch the prize (at least arguably) from America at the last moment. Accordingly, his prime and backup crews switched with McDivitt's. He shifted from Apollo 9 to 8 and his backup crew from Apollo 12 to 11. Armstrong, Aldrin, and Collins were now pencilled in for Apollo 11.


Deke Slayton quietly went to Borman and offered to break the rotation and put him and his crew straight onto the G-mission after their (hopefully successful) return. With their experience, and Borman's excellent piloting skills (one of the top pilots in the Astronaut Corps), the chances of Apollo 11 succeeding would be far greater - but Borman rejected it. He didn't think he could turn around his team in time, he'd done his bit, and he wanted out of the training grind.


(In some reports there are claims that Slayton later - very tentatively - then offered the G-mission to Jim McDivitt, who also expressed reservations about turning his team around in time. In the end, Slayton decided to just let the rotation take its turn and prove the truth of his oft-claimed assertion that any of his crews could do any mission).


Thanks to orbital dynamics and the higher latitude of the Soviet's space centre at Tyuratam, the Russians' "launch window" for lunar missions opened earlier in the month for them. The West watched anxiously on December 8th for any manned launches from Tyurutam - Zond could still snatch the first lunar flyby. And none came. The Soviets believed Apollo 8 to be a "risky adventure" with a mere 25% chance of success.


The risky adventure launched shortly after dawn on the winter solstice from the Cape, blasting into the sky on December 21st - the shortest day. Apollo 8 went flawlessly, entering lunar orbit in the early hours of Christmas Eve, carrying out 10 perfect orbits of the Moon, and then firing the SM main engine again to break orbit for return to the Earth. Thanks to orbital mechanics, the "Trans-Earth Injection" burn to come home had to happen on the far side of the Moon from Earth, out if contact with Houston, with radio contact blocked by the immense bulk of the Moon.


The epochal picture of "Earthrise" from the "glorified sightseeing trip" of Apollo 8

Mission Control waited on tenterhooks for Apollo 8 to clear the limb of the Moon and re-establish radio contact in the early hours of Christmas Day. If it came back into contact late, that would indicate that the SM main engine hadn't fired or had shut down too soon and the astronauts would be condemned to circle the Moon until their air ran out.


It was due to reacquire radio contact at Mission Elapsed Time 89 hours, 28 minutes, and 39 seconds. The telemetry came back from Apollo 8 on time to the second, shortly followed by Lovell's voice saying, "Houston, please be informed, there is a Santa Claus." The return to Earth went perfectly, Apollo 8 was an unqualified success, and America had the essential deep-space experience it needed.


Apollo 13

Jim Lovell's next mission was Apollo 13. You may be thinking that the rotation should indicate Apollo 14 - skip two from Apollo 8, back up the third (Apollo 11), skip two, fly the third (Apollo 14). However, when the first astronaut of the Original Seven, Al Shepard, managed to clear his long-standing medical disqualification by an operation to fix his Meniere's Syndrome, he was vaulted straight back to the front of the queue by his old friend Slayton (to the disgruntlement of some of the astronauts).


Shepard was allocated to command Apollo 13, the next mission that had not yet been formally assigned (the pencilled-in support crew of Apollo 10, who could normally expect to fly Apollo 13, were Gordon Cooper (the last of the Original Seven), Don Eisele (who had flown Apollo 7) and rookie Ed Mitchell. Cooper had long been regarded as unserious and a little work-shy, and would not fly again. Eisele had blotted his copybook on the famously bad-tempered Apollo 7 mission with Wally Schirra (none of whom would ever fly again). Ed Mitchell was, however, retained for Shepard's crew, with fellow rookie Stu Roosa added to the roster).


Shepard's many years out of training, however, made the mission challenging. Add in two rookies who had never before flown, and the training burden became huge - and the clock was ticking down for Apollo 13. Some astronauts grumbled that the entire crew had a total of fifteen minutes of flying time in space - Shepard's suborbital lob in Freedom Seven. Reluctantly, Slayton swapped the crews of Apollo 13 and 14 in order to buy some more time for Shepard. It proved an important decision - instead of three inexperienced astronauts, Apollo 13 ended up commanded by the most experienced astronaut in the corps, and one of the few who had flown to lunar orbit before - Jim Lovell.


We all know the story of what happened. The oxygen tank explosion, the crippled spacecraft, loss of power, the LM lifeboat. Why did it happen?

The famous Grumman "Towing invoice", sent to North American Rockwell after the relief of the rescue of Apollo 13. Grumman, tongue-in-cheek, charged for "towing" the CSM 400,000 miles, jump-starting the CSM electrical systems (with a discount for using "customer's jump cables"), provision of oxygen, and accommodation services (noting that the customer had already paid for 2 guests).

The oxygen tanks on the Service Module were crucially important, and thoroughly tested before flight. So what went wrong on Apollo 13?


In one of the tests for an oxygen tank for Apollo 10, there was a minor problem. The test that involved filling the SMs tanks with cryogenic fluids, checking their integrity under pressure and with no trace of a leak at extreme low temperatures, and draining them again - ran into a small issue. The drainage valve wouldn't operate. It appeared that the tank had been jolted and the assembly jammed - it wasn't a major problem; it wasn't supposed to drain in normal operations. And, in any case, there was a trivial workaround: turn on the built-in heaters and the liquid oxygen would warm up - and boil off into gaseous oxygen. The heaters would automatically click off at the target temperature and there would be no risk or danger at all.


No problem. Except there was: the heaters didn't click off when the tank reached the target pressure set by the thermostat. They stayed on for 8 full hours, and the temperature reached a thousand degrees (unnoticed by technicians, because the temperature gauge went no higher than 85 degrees Fahrenheit, as that was the maximum temperature envisaged. The intense hear cracked the insulation on an electric motor which controlled the fan tank. When it was turned on fora routine stirring of the oxygen tanks according to the mission plan - 2 days, 7 hours, 54 minutes into the flight - there was an electrical arc, a fire bloomed in pure liquid oxygen, and the tank exploded like a small bomb.


As it happened, for unrelated reasons involving modifications, the tank was removed from the Apollo 10 spacecraft and placed in the Apollo 13 one (this was prior to whatever jolt had jammed the drainage valve).


Voltage change


The oxygen tanks on Apollo 13 - and Apollos 7, 8, 9, 10, 11, and 12 (they were redesigned for Apollo 14 onwards, unsurprisingly).

The jolt that caused the jamming of that minor valve - that led to the chain of events which culminated in an explosion on Apollo 13 - could have happened on any mission. It happened when the tank was accidentally dropped by two inches - something completely unremarkable on any engineering project of this nature.


It wasn't the valve or the workaround that was the true cause of the accident. It was the malfunctioning thermostat (coupled with the failure to have a temperature gauge that could show the full range of heat that could be experienced.


The thermostat malfunctioned due to a massive overvoltage. It was designed to operate at 28 volts. After all, that was the design rating of the entire Apollo spacecraft - no issues there. Except that the Apollo spacecraft was upgraded to accept 65 volts from ground test equipment and no-one upgraded the thermostat or noticed the problem. The overvoltage caused an arc that welded the electrical contacts shut and it stayed on - with the outcome described above.


The electrical change was made in 1965 - before the entire Block II spacecraft were built. It could easily have happened to any Apollo mission from Apollo 7 onwards.


Including Apollo 8.


The possibility of using the LM as a "lifeboat" in case of problems with CSM life support, guidance, manouevring, or main engine damage had been long held as a potential contingency plan. Extra provision had been added to the LM design specifically for this purpose.


What If...


It was perfectly possible for the Apollo 13 disaster to have occurred on Apollo 8. Let's assume it would have happened at a similar time - with the oxygen tanks stirred to ensure accurate readings at a similar point into the journey.


Without the LM lifeboat, with the fuel cells dead, the CSM would have run down its batteries in about a quarter of an hour and it would have turned into a cold tomb. No air recircling, no oxygen being replenished, no heat, no light - no life. The astronauts would have died before the spacecraft looped around the Moon. As it happened, Apollo 8 was on a "free return" trajectory, where it would have looped around and headed back to Earth automatically if the SM main engine hadn't fired at all. This wouldn't have saved the astronauts in an analogous disaster - it would merely have flung their corpses Earthwards. And, with no further trajectory corrections or the ability to control re-entry (or, for that matter, fire the parachutes), it would either have skipped off the atmosphere into deep space, burned up on re-entry, or slammed into the sea or ground at terminal velocity. With three dead astronauts slumped in their seats.


With only one successful mission since The Fire.


A free return trajectory, as flown on Apollo 8. Would not have saved the crew from an Apollo-13-like disaster, but would have given a chance of the spacecraft at least impacting back on Earth


Apollo would have killed two crews out of three. NASA would have killed six astronauts out of the last nine. JFK's challenge would have been lost - there would certainly have been a lengthy delay similar to the period after The Fire, and Christmas 1968 would be indelibly linked with American humiliation in space, with death and loss.


Would Apollo itself have been scrapped? A lot of time, money, and effort had been expanded, and NASA had a significant number of Saturn V rockets already either delivered or in production. The LMs for the landing mission were being rolled out of Long Island by Grumman. There were several CSMs already built - but would they have been redesigned for a "Block III"? NASA had more than fifty astronauts on the roster and whole centres devoted to manned spaceflight. Importantly, James Webb, the former NASA Administrator who had retired in the aftermath of the Fire and with a change in Administration in the Oval Office, had ensured the "pork" had been spread around, with lucrative contracts employing man people in several Congressional Districts, in his attempt to make Apollo un-cancellable.


Would America really have abandoned the Moon after a second fatal mission in rapid succession? Even with the amount of sunk cost and the efforts of Webb, it had to be conceivable. Even if it hadn't been cancelled, it would have been delayed well into 1970 or 1971 - giving the Soviets a chance to catch up and even snatch a Zond success before JFKs deadline.


What else would have been among the repercussions?


Discuss this article

Andy Cooke has written the sci-fi Endeavour trilogy (The End and Afterwards, Diamond in the Dark, Beyond the Sunset) and the political alternate history Lectern books (The Fourth Lectern, The Fifth Lectern), published by SLP