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Randy Cassingham's BlogHistorical Details and Author's Notes from This is True®
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One Small Step for [a] Man
It was 30 years ago Tuesday that Apollo 11 astronaut Neil Armstrong piloted the Eagle -- the first manned lunar-landing spacecraft -- to the surface of the moon. He had to land manually, as the onboard computer couldn't process instructions fast enough as they sped toward a field of boulders; landing on them would have surely meant death. But he settled down with less than 30 seconds of fuel remaining and, after a few hours of rest, stepped onto the surface of our moon, followed shortly by Edwin "Buzz" Aldrin, while Michael Collins circled less than 10 miles overhead in the command module, Columbia.
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Driven by dreams -- and funded by a burning desire to beat the Russians -- the first moon landing on July 20, 1969, was a defining moment in history. Never before had so many people, in so many countries, watched a single event with such awe.
"It was probably the greatest singular human endeavor, certainly in modern times, maybe in the history of all mankind," said former astronaut Gene Cernan last week. Now 65, Cernan was the last of the 12 men to walk on the moon, from Apollo 17 in 1972. In a rare interview last week, Armstrong said that at the time of launch, he guessed their chances of returning alive were about 90 percent, and the chances of a successful landing on the moon were only 50 percent. But they went anyway, and gladly.
Everyone in the program knew there were significant risks -- right up to the top. President Richard Nixon was ready to address the nation in case of failure. Nixon speechwriter William Safire (now a columnist for the New York Times) wrote the words Nixon never had to use: "Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace. These brave men, Neil Armstrong and Edwin Aldrin, know that there is no hope for their recovery ... [and] are laying down their lives in mankind's most noble goal: the search for truth and understanding."
Imagine the pressure they must have felt! But they thought it was important to take such risks. True heroes indeed, and it was worth it: their bold steps inspired an entire generation, not just of Americans, but of the entire human race. Including me -- I started my career as a science writer, with a specialty in explaining complex topics to a lay audience, proudly working at NASA's Jet Propulsion Laboratory for ten years, where I loved being shoulder to shoulder with the people that make our reach toward the stars happen.
For a terrific summary of the Apollo 11 mission -- as told by the astronauts while it was fresh in their minds -- well illustrated with great photos, see NASA's The First Lunar Landing site -- released for the landing's 20th Anniversary!
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Posted by Nigel, Sheffield UK on July 22, 2009:
"He had to land manually, as the onboard computer couldn't process instructions fast enough as they sped toward a field of boulders."
AIUI this is not true. It was always part of the plan that the crew would have and probably use the ability to steer the lander (or as Armstrong put it afterwards, exercise his "God-given right to be wishy-washy about where I was going to land"), but the computer was an essential part of the Apollo flight controls. Attempts were made in the simulator to fly the lander fully manually but they failed - the lunar lander was simply too unstable to be handled without electronic mediation.
It's true that the onboard computer issued alarm codes during descent ("1202 alarms") which indicated it was heavily loaded. However it's important to realise that the computer was a multi-tasking machine and had other roles than mediating the flight controls. One of these was monitoring the lander's 2 radars, one aimed at the lunar surface for the landing, the other aimed back at the command module for docking and undocking.
The exact explanation of what happened is a little unclear but it seems that the computer was only specced to handle the volume of radar data from one radar at once. However during the descent both were active, or at least appeared to be from the computer's point of view, and it was getting swamped. It therefore did what it was designed to do in this situation - drop the lowest priority tasks (the rendezvous radar calculations) in order to ensure the higher priority flight control tasks got the resources they needed. It then popped up an alarm to let astronauts and ground control know what was happening.
I'll end with a few articles which go into the story with more depth and/or eloquence than I've managed above.
http://history.nasa.gov/alsj/a11/a11.1201-pa.html
http://kn.theiet.org/magazine/issues/0912/smart-apollo-0912.cfm
http://blogs.airspacemag.com/daily-planet/2009/07/20/troubleshooting-101-1201-actually-and-1202-too/
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I was being necessarily brief. The computer didn't crash per se, but Armstrong did have to alter the landing location at the last moment because of unanticipated boulders in the way. The 1201 and 1202 alarms were definitely a distraction, and in a simulation 11 days before launch, the flight director, not understanding the alarms (that were included on purpose) aborted the landing. That turned out to be a good thing, since when they popped up during the actual landing, they knew it was a simple overload situation and that it was OK to proceed.
For a more technical description of the LM's onboard computer systems see http://history.nasa.gov/afj/compessay.htm
-rc
Posted by Robert, Beaverton, OR on August 4, 2009:
Thank you for acknowledging that it was indeed "...one small step for a man...". I remember it vividly- I had just returned from Vietnam (and discharged from the USAF) two months previously, and my Mom and I were in the Living Room, glued to the TV, just as we were in Nov., 1963. I always wondered what ever happened to that "a", and what else in our history has been "corrected" that we don't notice!
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I acknowledged that he meant to say "a man". What he actually said, however, was "That's one small step for man, one giant leap for mankind." -- dropping the "a". Analysis of the tapes have shown that it was not dropped from the transmission, but rather not said in the first place. -rc
Posted by Tom in Tucson on August 18, 2009:
On 20July1969, my Marine unit, 1st Battalion, 9th Marine Regiment and I, after having been pulled out of Vietnam by presidential order, diembarked at Okinawa. We found out later that day what happened on the moon.
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Talk about mixed emotions! You missed witnessing fabulous history, but getting out of 'nam is a pretty good reason. -rc