Four decades ago, this week, NASA almost didn’t land on the Moon. By the spring of 1972, four pairs of Apollo astronauts had left their bootprints in the ancient lunar dust and brought rock and soil specimens back to Earth, which hinted of a long and complex geological history. The inaugural steps of Neil Armstrong and Buzz Aldrin were less than three years old, but with four successful lunar landings in the bag, NASA scientists and trajectory planners had grown increasingly confident over where to the send the final two crews on Apollo 16 and 17. Flat mare were visited on the first two landing missions, then the hilly Fra Mauro region and the spectacular highland site of Hadley-Apennine were explored. With Apollo 16, NASA intended to directly sample the lunar highlands and some scientists had their eyes keenly focused on a single crater: Tycho, an enormous, yawning basin, 80 km wide, easily visible from Earth in the Moon’s southern hemisphere.
Already, unmanned Lunar Orbiter photographs had revealed Tycho to be littered with gigantic boulders, violently ejected from deep within the Moon’s interior. A mission to Tycho might unlock many secrets of early lunar history and evolution…but it was not to be. It was notoriously difficult to reach and its location, many hundreds of kilometres from the equator, meant that a lunar module would have to fly across a hellish patch of rugged terrain and land in a rock-strewn wasteland. Moreover, landing so far south would demand additional fuel reserves, which in turn would cut the amount of scientific payload that could be carried down to the surface. Many NASA managers considered it insane to even contemplate landing at Tycho. When Apollo 13 demonstrated the dangers of flying to the Moon, the prospect of getting approval for Tycho vanished.
So too did another proposal to land on the lunar far side, out of direct contact with Earth, which would have required some sort of relay satellite to enable communications. By the time the Site Selection Board convened in May 1971 to settle on Apollo 16’s landing place, the decision fell in favour of the Cayley Plain, about 50 km south of the crater Descartes and slightly to the west of Mare Nectaris. Deep in the lunar highlands, it was hoped that this location would yield volcanic rocks and that these might offer an insight into the Moon’s physical and chemical evolution. Many geologists were so convinced that Apollo 16 would find volcanic rocks that almost all of the crew’s field training was at volcanic sites on Earth. That crew had a history of ill fortune. Commander John Young would fly to the lunar surface with Charlie Duke, who had earlier been a member of the Apollo 13 backup crew. His German measles led to a last-minute decision to ground Ken Mattingly in April 1970. Now, two years later, the men would fly to the Moon together, with Mattingly remaining in lunar orbit as the pilot of the command module Casper.
There was no problem between Mattingly and Duke, of course, but Apollo 16’s backup commander, Fred Haise, could not resist a little fun on launch morning, 16 April 1972. “We were climbing into the command module on the launch pad,” Duke recalled in his NASA oral history. “I looked over and, taped to the back of my seat, was a big tag that said Typhoid Mary!” Haise grinned. It was light-hearted payback, particularly as Duke had also entered the headlines in January 1972, following a bout of bacterial pneumonia. There was never any chance that Duke would be replaced so close to launch; that, wrote fellow astronaut Deke Slayton in his autobiography, Deke, was one lesson they had learned from Apollo 13. As for Ken Mattingly himself, it would appear that not only did he want to land on the Moon, but that he was offered the chance to do so. In his oral history, Mattingly recounted an offer by Slayton to either be command module pilot on Apollo 16 or lunar module pilot on Apollo 18. Aware of the looming budgetary axe, Mattingly took “the bird in the hand” and Apollo 16 proved to be the right call.
Yet fate almost had another card to play for Mattingly. Shortly before launch, doctors found an elevated level of bilirubin, an indicator of liver function, which possibly indicated hepatitis, in one of his blood tests. (“Billy who?” Mattingly snorted, incredulously. “Who’s he and what’s that?”) His relationship with the doctors in those final days was “about as antagonistic…as you could create”, but he was cleared to fly.
Atop the Saturn V – the most powerful rocket ever brought to operational status – Apollo 16 roared into space at 12:54 pm EST on 16 April 1972 and within hours had begun its four-day voyage to the Moon. For Mattingly, the entire mission was one of fear; not fear of death or fear of mission failure, but fear of having an erasable memory and forgetting one of the grandest adventures in exploration ever undertaken in human history. “If I see one more thing,” he said of this very tangible concern, “it’s going to write over something I just saw and I’ll forget it. I know that’s preposterous, but I had this very palpable fear that if I saw too much, I couldn’t remember. It was just so impressive. These things kept coming for the next ten days. They never stopped.”
At length, late on the evening of 19 April, Casper and the connected lunar module, named ‘Orion’, arrived in lunar orbit. The mission had been flawless, with only an irritating flecking of thermal paint from the lander’s exterior to contend with. This caused a cloud of particles to trail the spacecraft. Shortly after midday EST on the 20th, Casper and Orion undocked and John Young and Charlie Duke readied themselves for a powered descent, riding the fire of their spidery craft’s descent engine down to the Cayley Plain. As they flew in formation with Mattingly, things took a decidedly ugly turn.
One of Mattingly’s first duties was to fire the service module’s big Service Propulsion System (SPS) rocket engine to adjust his orbit around the Moon from an elliptical one into a near-circular one. This would enable a scientific bay of remote-sensing instruments to survey the lunar surface for three days whilst his crewmates were away. He routed electrical power to the engine, activated the gyros and prepared to test the secondary control system..and then, as he touched the yaw thumb-wheel for the gimbal motors, Casper shuddered. Mattingly tried again. The same thing happened. From his perch in the command module, it felt as if he was guiding the command module down a very rough railway track.
“Go ahead, Ken,” replied John Young from the lunar module.
“I have an unstable yaw gimbal No. 2.”
“Oh, boy.” Young and Duke suggested a few options, but they instinctively knew that if the SPS control mechanism was somehow damaged it would spell the termination of their mission. In all likelihood, the next mission, Apollo 17, would probably also be cancelled. Mattingly knew that he could move the nozzle, but was not sure if he could circularise his orbit with it. Mission rules dictated that all four thrusters-vector-control circuits, both primary and secondary, had to be working for the burn to go ahead. The men were out of options. They were forced to fly in formation, whilst the engineers at Mission Control pondered over what to do. A redocking and rescheduling of the landing for the next day was out of the question, because by then the Sun would have risen another 12 degrees in the sky and lighting conditions at the Cayley Plain would be unfavourable.
One hour passed. Then two. Then three.
On the ground, data had been fed into a mockup of the SPS engine and it was concluded that if Mattingly had to use the secondary system to perform the circularisation burn, the engine might shake, but it would be controllable. Watching from Mission Control was former astronaut Jim McDivitt, now Apollo Spacecraft Program Manager. On his Apollo 9 flight, he had performed a test firing of his SPS engine and it responded well, even under duress. McDivitt advised Chris Kraft, director of the Manned Spacecraft Center, that it was safe to proceed. Four and a half hours after the trouble first arose, at 7:00 pm EST, astronaut Jim Irwin, seated at the capcom’s console in Mission Control, radioed the happy news: the landing could go ahead. What no one except Mattingly knew, however, was that all of the SPS control signals – primary and secondary – ran through the same cable. When he learned this fact, months earlier, Mattingly thought little of it. After the flight, though, McDivitt told him that if Mission Control had known about the cable, they would never have sanctioned a lunar landing…
The second part of this three-part article will appear on Friday.Missions » Apollo »