case where a failed switch would set the abort bit in the computer. Thorson’s team had developed a set of instructions to tell the computer to ignore the abort switch. Thorson now reached into his bag of tricks, addressing Griffin: “Flight, I’ve got a software patch for the LM computer that will disable Channel 30, Bit 1, in the computer. It will lock out the abort switch for the landing.”
Griffin listened intently, then frowned as Thorson concluded by saying, “There is only one problem. If the crew has to abort, they will have to use the backup system or the computer keyboard to manually enter the abort program for the primary system.” Griffin was willing to buy the extra risk, and he knew without asking that Shepard would, too. “Dick, dig out the patch,” he instructed, “and run it through SPAN and get with the simulator people. If it works, I’m going to give it a Go.” Astronauts were soon clambering into the simulators, with the results to be relayed instantly to CapCom Haise.
Satisfied with the ongoing action, Griffin called his team to attention, resetting the timeline for the landing. The answers were needed in less than two hours.
In the Flight Dynamics staff room, Jack Garman listened to the conversation. Garman was the computer expert who had helped Steve Bales out of his hole on Apollo 11. Now he had to come up with the answer to a different problem. Jack was normally excitable and when there was an option to use “his” software to save a mission, he leaped into action. Garman talked with every part of his body, eyes and hands constantly in motion. Within seconds, he was on the voice loop to the software team at MIT. Like Griffin, he was worried about the time it would take the crew to make the computer entries if they had to abort. Garman felt that the crew needed a software patch to protect against the switch failure that would still give them the ability to use the abort button. He didn’t know whether such a patch could be developed, but he sure as hell was going to give it a try.
MIT was listening to the astronaut voice loops and had heard the discussion about the software patch to bypass the abort switch. They had already cranked into action. (MIT’s Draper Laboratory developed the guidance and navigation systems for Apollo. To assist in rapid troubleshooting during a mission, the MCC was in direct communications with the lab.) Within an hour the Draper Lab came up with a procedure that gave us an option to bypass the abort switch at engine start and then reenable the switch. The procedure was complex and time-critical. Sight unseen, Griffin elected to give the new procedure a shot.
Communications were a mess during the final front-side pass. Static crackled and punctuated Haise’s instructions to Mitchell. The procedure required the crew to start the engine at a low power, using the acceleration to move the contaminating piece of metal away from the switch contacts. Once the engine was started, Mitchell would insert a string of sixteen computer commands to enable guidance and provide steering.
When this was completed, another string of sixteen commands would disable the abort program, and another fourteen commands would lock into the landing radar and the descent software. This entire sequence would occur as the crew was descending to the Moon. The mission now rested on an emergency patch to the flight software that was less than two hours old, had been simulated only once, and was being performed by a crew that had never practiced it. Every step had to be executed precisely on time and in sequence.
Sitting on the step behind Griffin, I looked into the viewing room. I could see the spectators buzzing. Our words and procedures were gibberish to them. In the mission operations control room, it was just another day, another final exam, as the controllers calmly chipped away at the final procedures and counted the seconds until engine start. The controllers’ ability to focus at times like this was nothing short of a miracle, a miracle of ingenuity, discipline, and training.
Shepard sounded just as he had all those years ago when he first went into space. Marvelously calm, his voice was flat and emotionless as Mitchell read the checklist, verified the switches, and entered data to the computer. With split-second teamwork, we started down to the Moon. Mitchell announced, “Engine start.” Thorson, staring at the abort switch display, added, “Ten percent thrust… throttle up. I see no abort indications.”
Mitchell quickly entered the first string of commands to bypass the abort bit. With the successful entry of the data, you could hear the relief in Shepard’s voice: “Thank you, Houston, nice job down there.”
Just another day at Mission Control.
Thorson’s eyeballs, which had been locked on to the abort bit, now swung over to his engine systems. “Gerry, I’m Go,” he confirmed. “All of the data is in correctly. The abort program is bypassed.” Fred Haise, the Apollo 13 LM pilot, then talked Mitchell through the rest of the workaround procedure.
With a lyrical comment from Alan Shepard—“It’s a beautiful day to land at Fra Mauro”—the LM
But the battle was not over. The team would be challenged once more.
Prior to starting the descent the guidance officer provided the navigation and target data to the lunar module computer for landing. The computer then developed the guidance commands to reach the target during descent. In the final phase of the landing, the LM computer needed more accurate data than that provided by Mission Control. There might be an error of several thousand feet between the altitude data provided by the MCC and the true altitude provided by the LM radar. Mission rules required an abort if the radar data was not obtained before descending to 10,000 feet. Landing without a good hack at the altitude would be worse than landing on a carrier on the ocean on a dark night; there was no good way to judge height. LM landing fuel was tight, so that a “grope and feel” approach would deplete fuel prior to touchdown, leaving the crew in a low-down fire-in-the-hole abort. Not a good situation.
Passing through 32,000 feet, Mitchell started looking for the landing radar data. In Mission Control, guidance officer Will Presley cued up his displays. He had about ninety seconds to make a judgment to accept the data or, if it was not in limits, abort the mission. The radar data did not show up when expected, and Presley in the MCC and Shepard in the LM both had to be thinking, “Where the hell is the radar?”
In a voice lacking conviction, Presley gave Griffin a Go to continue descent at five minutes, knowing that in the next sixty seconds he would have to call an abort if he didn’t get radar. I knew his stomach had to be churning. The LM radar was Thorson’s responsibility. He and Griffin were also watching for the indications that the radar was tracking the surface.
Griffin was the first to move. “Dick, you got anything you want to try?”
Thorson reached into his bag for the only thing that could be done in a few seconds: “Flight, have them cycle the circuit breaker.”
Quickly, Shepard acknowledged, “Cycled.”
Seconds later, a jubilant Will Presley shouted, “Flight, we got radar lockup!” Every controller had been holding his breath. For a few seconds the voice comm was noisy as all exhaled, some even whistled. Presley’s next words were virtually shouted, tripping over each other as he blurted, “Altitude data is Go, accept the radar.” From there on, the landing was a piece of cake.
Of course, Alan Shepard walked on the Moon and left behind two souvenirs for some future explorers to find. Somewhere in the craters of the Moon are two golf balls, the first ever hit in outer space. He attached the head of a Spaulding 6-iron to a tool used to scoop up lunar soil. This was done for the highly scientific purpose of seeing how far a golf ball would travel in gravity that was one sixth the Earth’s. Actually, he duffed his first shot. “It got more dirt than ball,” he confessed to our controllers.
“That looked like a slice to me, Al,” came the reply.
His second shot traveled, by his estimate, “miles and miles.” The experiment did not appear on anyone’s manifest, but Shepard had cleared it with Deke Slayton. The agreement was that he would do it only if the landing had gone well, and it had. Years later, Al would reflect, “I’m probably a lot more famous for being the guy who hit the golf ball on the Moon, than I am for being the first American in space.”
After the post-mission debriefing, Mitchell invited Thorson and several members of the Trench to dinner. Mitchell, the astronaut who be lieved in psychic phenomena, said that he knew moments before the call that Thorson was going to have the crew cycle the landing radar circuit breaker. Griffin and Thorson were never sure whether Ed was kidding them or not. They were just happy it all worked out.
After the debriefing, Shepard took Griffin aside and confided, “I had come too far to abandon the Moon. I would have continued the approach even without the radar.” On Apollo 14 the error in the LM computers’ knowledge of the actual altitude was almost 4,000 feet before the landing radar data update. With an error this great in the computer, Griffin and the Trench were convinced Shepard would have run out of fuel before landing. But everyone who knew Al never doubted he would have given it a shot. We also never doubted he would have had to
