Twenty Seconds
Combating a computer glitch during Apollo 11
Gene Kranz is seated at the Flight Director’s console in Mission Operations Control Room Two. The size of a small theater, the room is on the third floor of Building 30, located off of Avenue C on the NASA Manned Space Center campus. Kranz wears a dark tie and a white long-sleeved shirt under a light-colored vest handcrafted by his wife Marta. His blond hair is tightly cropped in a flattop, a holdover from his time flying F-86 Sabres over the Korean Demilitarized Zone.
Kranz is in charge of the room; his NASA superiors can only overrule his decisions by firing him on-the-spot. His team of Apollo flight controllers is arranged in front of him like an orchestra performing at the Jones Hall in neighboring Houston. Seventy-four authorized visitors observe Kranz and his crew from five rows of seats behind large plate-glass windows. An additional five hundred million people are watching on television. Neil Armstrong and Buzz Aldrin are more than 230,000 miles away, descending to the Moon in the Lunar Module Eagle.
It is Sunday, July 20, 1969, 3:08 PM, Central Daylight Time.
“Okay flight controllers,” says Kranz, his accent betraying his Toledo, Ohio roots. “I’m going around the horn.”
His team checks their data. Each controller is positioned in front of an array of screens, buttons, and status lights. Two floors below, awash in fluorescent light reflected from the white floors and walls, an IBM mainframe receives data from Eagle and streams the information to the controllers’ sage-colored consoles.
Kranz starts the roll call with the Trench, three flight controllers at the front of the room. Farthest to the right of that group is Steve Bales, a twenty-six year old Iowan with dark hair, wearing a dark sports jacket, and sporting black thick-rimmed glasses. As a flight controller, he is also the head of his own team who, collectively, are responsible for watching the Eagle computer. Those colleagues are in the Staff Support Room or—what most everyone calls it—the back room. His main contact there is an even younger man named Jack Garman. Garman is a Michigan Wolverine, having left Ann Arbor three years ago to take a job with NASA. Quick to reply to most anything, he has earned the nickname Gar-Flash.
The Trench is the dimmest part of the room. Five wall displays lit by quartz lamps bathe the area in blue, like a television set left on at night. The controllers like it that way; they can see the displays better in the dark. Kranz calls to his team members, asking each whether they should continue the descent. When he gets to Bales, he hears a resounding “Go!” Kranz chuckles in response to Bales’s gusto.
Kranz continues the poll; the rest of the controllers respond their systems are working well. Kranz then calls on Charlie Duke to inform Armstrong and Aldrin that they are to continue with the mission. An MIT-educated astronaut seated just in front and to the left of Kranz, Duke is the capsule communicator or CAPCOM. He is the lone member of the mission control center that talks directly to those aboard Eagle.
“CAPCOM, we’re go,” says Kranz.
Duke presses a button on his console to open the communication line to the astronauts.
“You are go to continue powered descent,” says Duke in a drawl that only astronauts and test pilots can master.
On-board Eagle, Armstrong is piloting the lunar module toward landing. Aldrin is monitoring the descent. Through the triangular windows of the spacecraft, the astronauts can clearly see the white and blue marble that is their home planet.
Suddenly, a light flashes and an alarm sounds.
“Program alarm,” says Armstrong with an urgency those at NASA rarely hear from him. A little over a year ago, Armstrong ejected seconds before his training simulator crashed in flames. He was back in the office within an hour. He is not the nervous type.
He reads the green on black display of the spacecraft computer. “It’s a 1202,” says Armstrong.
“1202,” repeats Aldrin. Armstrong and Aldrin exchange looks. What’s a 1202?
Back in the Mission Control Center, directly behind Kranz, Chris Kraft, Kranz’s mentor and supervisor echoes the two astronauts, “What the hell is a 1202 alarm?”
Fortunately for the mission, Garman knows. Five days ago, Kranz, Garman, Bales, and the rest of the team conducted their final landing simulation. A simulation is like a dress rehearsal for a Broadway musical except with a crazed phantom periodically knocking over props, disconnecting the stage curtain, and setting the theater on fire. The phantom at NASA is a team led by Dick Koos. They introduce various problems in the landing process to see how the controllers respond.
During this simulation, Bales and Garman were baffled as they tried to contend with multiple strange computer alarm numbers that they did not fully understand. Among the alarms, was the same 1202 code that was now being displayed in the Eagle and on Bales’s console. Bales and Garman were exhausted and spent by the end of the day. After the test was over, Kranz took his two young team members aside.
“I want you to figure out every possible alarm code that can happen in flight so that we’re prepared,” said Kranz.
Garman did. On a sheet of grid paper, he made a list of all the potential alarm codes, their causes, and the proper action in response. Earlier in the week, Garman had placed the paper under the plexiglass of his console in the back room. He is looking at it now.
Alarm code 1202 signaled that the lunar module’s computer lost a battle against time. Every two seconds, the landing software has a list of chores to do to keep the spacecraft on track for touchdown. Unfortunately, due to either an error in training or just a mistake, Armstrong and Aldrin have left on a radar system that is not needed for landing and is now generating too much data. Like a juggler out of his league, the computer could not contend with all that is being sent its way. Eventually, it gave up and rebooted.
Through good engineering design, the computer has immediately returned to where it left off and continues operations. Hence, alarm code 1202 is not a reason to discontinue the landing as long as there is enough time between alarms. Bales considers this. As a flight controller, Bales has the authority to abort the Apollo 11 landing. During the simulation five days earlier, without the knowledge contained on Garman’s sheet of paper, he did exactly that. Not this time.
Garman calls Bales on his headset, “It’s okay.”
“We’re go on that flight,” says Bales.
Kranz responds, “We’re go on that alarm?”
“If it doesn’t reoccur we’ll be go,” says Bales.
Twenty seconds have elapsed since the astronauts called Houston about the program alarm. There has been no reply from Earth. Armstrong sounds restless. Is the mission over?
“Give us a reading on that 1202 alarm,” he says.
“Roger, we are go on that alarm,” replies Duke.
Hearing the transmission to Armstrong, Bales turns his attention back to his console.
The success of Apollo 11 was a result of an estimated 400,000 people who worked on the program. Among those thousands was Adrian Hooke, an engineer who, later in life, was a colleague of mine. Adrian worked for Grumman Corporation as an Automatic Checkout Equipment engineer on the Lunar Module. He was a member of the Red Team, a group of engineers who had to, in Adrian’s words, “sit in a loaded truck (on the wrong side of the fallback area after the Saturn V wet fueling was complete and the rocket was a large bomb waiting to go off) and be prepared to go in and fix the damn thing.” Adrian passed away on Janurary 7, 2013. This essay is a tribute to him and the other men and women who accomplished one of the greatest feats of the 20th Century.
References
Don Eyles, Tales from the Lunar Module Guidance Computer
First Men on the Moon, produced by Thamtech, LLC
Adrian Hooke, email conversation, March 7, 2006
Eric M. Jones, Apollo 11 Lunar Surface Journal
Gene Kranz, “Failure Is Not an Option,” Simon & Schuster
Christopher Kraft, “Flight: My Life in Mission Control,” Dutton
Photos of Mission Control, Steven Michael
