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Path to the Moon

February 22, 2019

During assembly on Friday, February 22, Martha McMahon, chair of the Computer Science Department, spoke about the moon landing in 1969 and the history and technology that made it possible. Here are her prepared remarks and some of the slides she shared:

The first humans from Apollo 11 walked on the moon in the summer of 1969. We’ll be celebrating the 50th anniversary of this amazing feat in just a few short months. It is fascinating to think about all of the combined factors that made it possible — it truly was a beautiful collaboration of technology, thousands of human minds, and a little bit of luck — making the absolute most of what little resources were available. But I’m getting ahead of myself.

Let’s start with why. Why did we even want to go to the moon?

First, space is beautiful! Just one glance at the sky on a clear night with the full moon shining is enough to take anyone’s breath away. Who wouldn’t be captivated by it? For centuries, humans across the planet have looked to the stars, charted and studied them, used them for navigation, marveled and dreamed about them.

It’s also no surprise that space exploration has always been a prevalent topic in pop culture, often focusing on the moon. Some examples the preceded Apollo 11 can be found in literature, movies, TV shows, comic books.

Looking at the moon for centuries, and it being the closest celestial body, natural human curiosity led us to wonder: Is it possible? What would it be like to go there?

The second reason to think about space travel was our capability for flight. For over two hundred years, humans have been using various contraptions and machines to achieve flight — from rudimentary balloons to the Wright Brothers, and then the invention of multi-stage rockets. Progress accelerated in the mid 20th century thanks to WW2 and Germany’s wartime missile designs. In the years following the war, intercontinental ballistic missiles (ICBMs) were developed and tested based on the German models. ICBMs were the rockets used in early space launches.

The third and certainly the reason for the timing of the U.S. going to the moon in 1969 was the Space Race.

In the 25 years leading up to the moon launch, the U.S. and the Soviet Union were engaged in a cold war, a geopolitical battle for supremacy that led the two nations to compete with each other everywhere, space included. In this 1960 Soviet propaganda poster, you see two Soviet astronauts confidently navigating space with ease. They had every right to be arrogant about it, they were winning the space race, to be sure. The U.S. seemed to be just one step behind on each achievement.

First came satellites — the first human-made objects to orbit the earth. The Soviet Union launched the first, Sputnik, in October of 1957, completing 1440 orbits around the Earth. Four months later, the U.S. launched Explorer 1, and while it orbited more than 58,000 times, we were late to the party.

Animal research was essential to the development of the technology to send humans into space, as there was so little known about the biological effects and plausibility of sending a living being into orbit.

A month after Sputnik 1, the Russians launched Sputnik 2, carrying a stray dog named Laika, the first animal to orbit the Earth. Sadly, they knew she would die because they did not know how to bring the satellite back to Earth. In December of 1958, the U.S. sent a monkey named Gordo into space on board a Jupiter rocket, and while he survived most of the flight, he died due to a parachute failure on re-entry. These were just two of many animals that lost their lives to space research.

In August of 1960, the Soviet Union successfully sent two dogs, Belka and Strelka, to orbit the Earth and returned them, making them the first animals to come home unharmed. In January 1961, the U.S. successfully sent a chimpanzee named Ham on a suborbital flight and he came home safely with just one injury, a bruised nose. However, his trip was merely suborbital and it was months after the dogs.

On April 21, 1961, Soviets win once again, sending Yuri Gagarin to space. One hundred and eighty-eight miles above the surface of the earth, he orbited in two minutes and returned safely. The U.S. launched Alan Shepard into suborbital space, but it wasn’t until February 1962 that they finally got John Glenn into orbit: he orbited three times in about five minutes.

It was clear that the U.S. was taking a back seat to the Soviet Union in the space race. In 1962, president Kennedy gave a passionate speech at Rice Stadium in Houston, Texas where he urged our nation to do what seemed impossible: put people on the moon and return them home safely. [McMahon played a clip from the speech] And so the quest for the moon began — with a time limit — Kennedy said “in this decade.” NASA settled in for years of hard work that culminated in the successful deployment and recovery of Apollo 11. So how did they pull it off? Let’s have a look at the computing power that was available on the missions leading up to Apollo.

First and foremost, human brains.

Project Mercury, which ran from 1958 to 1963, was the project that saw NASA’s first attempts to send Americans to space. There was no room on the capsules for computers and they weren’t advanced enough to make the calculations necessary, so NASA used a different kind of computer: women who computed. They were much faster than the first machines. These women monitored the spacecraft and had to calculate its location by receiving the raw radio data, long before computers could do anything similar. Many of these women went on to become the first computer programmers. If you’ve seen the film Hidden Figures, you might know that many of these women were African-American. Being a woman in a scientific field was challenging in the 60s, and being an African-American woman was more so as they were segregated from the rest of their colleagues in a separate building in a room labeled “colored computers." Katherine Johnson calculated and plotted the trajectory of Alan Shepard’s suborbital flight and John Glenn allegedly refused to make his historical flight until Johnson had checked the calculations done by the new computers at NASA.

After a few years of sending one person to space at a time, the Gemini program began sending two-person crews in 1965-66. These were the first missions to carry an on-board guidance computer. Carefully designed by IBM, the CPU only understood 16 different instructions. Programs were recorded onto magnetic tape and then transferred to the computer’s memory. Errors while loading the finished program were an ever-present danger. Imperfections in the tape could, and did, create bad instructions. At the time, the generally accepted standard was one error in 100,000 bits of information. NASA demanded an accuracy of one error in 1,000,000,000. To achieve this, the program was recorded three times and special hardware checked that all three copies were identical on the tape before adding it to memory.

Journalist Elizabeth Howell wrote in a 2014 article about Apollo 11’s technology: “While the Apollo 11 landing was on the cutting-edge of technology in 1969, today it's a demonstration of how much could be accomplished with so little. The computing technology of today’s average cell phone far exceeds the combined computing power of the two spacecraft that got humans to the moon and home safely.”

When we see how rudimentary the technology was, it is just awe inspiring. Apollo 11 is the ultimate example of how teamwork, research and extensive planning really can accomplish seemingly impossible tasks.

To be clear: Color TV was just starting to become mainstream, there were just a few channels to choose from. There was no cable. There were no digital movies, no digital music, no video games, no cell phones. There was no internet — at least not as we know it today — just a small network had been started for some super tech-y people at a handful of universities.

Seriously, at this point, you may be thinking: What did people even do? That’s a different presentation. The point is, technology was nowhere near the advanced state that we enjoy and rely upon today in our daily lives.

So what did we have in the late 60s?

Humans were just discovering how useful computers can be. In the 50s, computer companies estimated that six computers could serve the needs of the entire US. Six. Total. By 1968, there were 50,000 in use. A number of advancements in science and engineering contributed to this exponential growth — primarily progress at MIT and IBM in computer engineering with circuits and memory systems.

IBM had a breakthrough in the late 50s with its 1401 model computer. This giant machine and its successors rapidly became the most popularly used and stayed that way through the 60s as they became the first economical replacement to cumbersome punch card systems. It is considered by many to be the “Model T Ford” of computers. IBM models became the computers to have, and we have IBM to thank for the wide use of computers across the country in the years leading up to the moon launch.

IBM was a crucial contributor to the space program. ... In addition to providing much of the equipment needed, IBM had over 3500 employees involved in the mission from the ground.

Before getting into specifics, it’s important to see the big picture. This was a multi-stage mission with 24 parts, 24 processes that all had to take place in sequence, at the right moments, and each of these 24 stages had multiple components that needed to function properly, both human and technological. There were so many possible points of failure that could have caused at best just an aborted mission, but at worst the death of one or more of the three astronauts involved.

There were three main parts to the Apollo 11 space craft, and each had multiple sub-components. First, the Saturn V multi-stage rocket to get the astronauts into the Earth’s orbit. Second, a two-part Command Service Module (CSM) where the astronauts rode for most of the trip (the top was the command module or CM where the astronauts rode and lived, the bottom was the service module or SM which provided life support and the propulsion system that got them to and from the moon once in space). Third, a two-stage Lunar Module (LM or “lem”) for landing on the moon and taking off to re-attach to the CSM. As the space craft flew, various components in part or whole were jettisoned as they were used up or no longer needed. Parts were flying off and re-attaching throughout the mission.

Now for a “simplified” timeline of the process: Apollo 11 launched into space from Kennedy Space Center in Florida. From there, they entered Earth’s orbit. They exited Earth’s orbit at just the right point to head for the moon. Then, they entered the moon’s orbit. While the CSM orbited the moon, the LM had to detach, land on the moon, allow time for 2 astronauts to go outside for several hours, then re-board the LM and reattach to the CSM to head home. They exited the moon’s orbit, again at just the right spot, to come back to Earth They re-entered Earth’s atmosphere without burning up, and landed in the North Pacific Ocean. On re-entry, only the Command Module was left from the original giant multi-stage spacecraft. The mission was so risky that before they even launched, President Nixon had a speech prepared to deliver to the nation in the event that the astronauts didn’t make it back.

Here is a picture of the astronauts that took this incredible leap of faith, their lives at stake, to make human history for all time.

Pictured here, from left to right: Neil A. Armstrong, commander; Michael Collins, command module pilot; and Edwin E. Aldrin Jr. (“Buzz”), lunar module pilot.

Michael Collins, had to stay in the CSM to orbit the moon while the other two took the LM to the surface. He is often referred to as the forgotten astronaut; however, he played a vital role in the success of the mission! Buzz and Neil completed over 20 hours of work on the surface, collected almost 50 pounds of lunar material to bring home and study, set up a solar wind experiment, took photos, erected an American flag and plaque, participated in a TV broadcast, and talked to President Nixon. After all that, they re-boarded the LM, reunited with the CSM and headed home.

Once back on Earth, the astronauts had to immediately put on bio-hazard suits in case they brought back anything living from the moon. They were then quarantined for 16 days before they could return to their families.

I couldn’t do a talk about the technology involved in Apollo 11 without at least briefly mentioning the suits worn by the astronauts. The lunar spacesuits were an engineering feat in and of themselves. They were designed to provide a life-sustaining environment for the astronaut in space. They permitted maximum mobility and were designed to be worn with relative comfort for up to 115 hours in conjunction with a liquid cooling garment. If necessary, they were also capable of being worn for 14 days in an un-pressurized mode.

So, about the on-board computers: There were actually four computers on the Apollo 11 spacecraft. Many folks think just one. These computers were primitive. There were no fancy graphical user interfaces, screens or mice like we use commonly today. Resources couldn’t be wasted on such luxuries.

The first computer ... was The Launch Vehicle Digital Computer, or LVDC. This was on the rocket. It was a “black box” computer in that it was set up to respond to sensors and required no human interaction. However, it’s job was crucial. It precisely controlled the rocket path from the launch pad to the point at which it was discarded in earth’s orbit. The second (and third) computer was the famous Apollo Guidance Computer (AGC). It was designed by MIT and was fondly referred to by the astronauts as the 4th crew member. There were actually two of these computers, so it was really the 4th and 5th crew members. One was in the command module, and one was in the lunar module. On earlier space missions, navigation could be controlled from personnel on Earth. However, the moon was too far away and NASA’s best signal strength would take two seconds to send instructions to the moon — too long. The flight path needed an exceptional level of precision. Astronaut David Scott said: "If you have a basketball and a baseball 14 feet apart, where the baseball represents the moon and the basketball represents the Earth, and you take a piece of paper sideways, the thinness of the paper would be the corridor you have to hit when you come back."

While the astronauts would most likely have preferred to fly manually, only the AGC could provide the accuracy they needed. In designing the AGC, size was an issue. Just a few years before, the computer power necessary would have taken up the space of a Burroughs classroom — way too big to be carted off to the moon. For this mission, the guidance system for Apollo could not be any more than 70 pounds and could only take up one cubic foot. The AGC provided computation and electronic interfaces for guidance, navigation and control of the spacecraft. Every part had to be tested to withstand the vibration, shock, acceleration, temperature, vacuum, humidity and electronic noise. It also flew the spacecraft for most of the mission and was programmed as a backup to the LVDC.

To save weight, space and power, designers decided to risk using newly invented integrated circuits. In addition to these circuits, the AGC used core memory, as well as read-only magnetic rope memory. The AGC memory was woven together by hand — not produced by a machine.... Perhaps most remarkably, the AGC contained just 36K of storage memory and 2K of RAM for executing commands. To give perspective on this: the Macbooks used by JBS teachers have eight million times the working memory. The AGC had very limited memory space — and it flew the ship.

... Astronauts on Apollo 11 communicated with the computer by punching two-digit codes into the display and keyboard unit (DSKY or “disky”). They had to punch in 10,000 commands on the Apollo 11 mission, and the possible instructions filled a 1000-page manual. Each command required a number of keys to be pressed. In perusing the manual myself in preparation for this talk, I noticed that many of the command listings were very polite and began with “please.” I laughed out loud when I saw “Please enable engine” — as if saying please makes any difference to a computer.

The 4th computer of the mission was the Abort Guidance System or AGS. The back up. It was originally named the Backup Guidance System, but the acronym “BUGS” was not well received for obvious reasons. It is overlooked often because it was barely used on the mission; however, its presence on the lunar module was crucial. It was plan B in the event that there was a problem during landing or takeoff from the moon. ... It had a completely different operating system and instructions from the AGC to avoid duplicate errors in the two machines. It was only used briefly when re-docking to the Command Module, due to a small mistake made by the astronauts in the sequence of rendezvous commands.

So this is actually a more accurate picture of the true flight paths for Apollo 11 .... You may wonder why the moon is shown twice. Well, it wasn’t in the same place when they came back, because it revolves around the earth! Also, if the Sun were in this diagram, you’d see the Earth was also not in the same place on return. If you weren’t already convinced that this was a tough mission, you should be now! These were moving targets, people.

On the morning of July 16, 1969, Apollo 11 took off for the moon. Four days later, it was time for Armstrong and Aldrin to move to the LM and attempt to land on the moon.

Of course, not everything went perfectly. For starters, the communication radio signal with ground control kept going in an out. To make matters worse, at 35,000 feet above the surface of the moon, alarm codes in the AGC went off. Codes 1201 & 1202 sounded. The computer had run out of memory for what it was being asked to do. Remember how I said it had such small memory capacity? It was basically saying, "I have too much to do, so I am going to stop, reboot and start over."

The astronauts had not seen it in their training, and to say they were nervous about it would be putting it mildly. Thanks to the presence of the backup computer if needed, ground control decided not to abort and the mission went ahead.

At 2,000 feet, Armstrong noticed that the area they were headed toward had a crater and large boulders, uh-oh again. They were not in the spot they had planned to be in! Also, they were running dangerously low on fuel. Armstrong manually steered the capsule to avoid the rocky terrain and successfully landed on the Sea of Tranquility with less than 30 seconds left of fuel. Armstrong relayed the message: “Houston, tranquility base here. The eagle has landed.” Armstrong and Aldrin left their lunar lander and walked on the moon on July 20. Four days later, they returned to earth, splashing down in the Pacific on July 24. The whole mission took eight days. The computer systems and the people involved in their operation were unbelievably impressive, but there’s more.

Obviously, if we were to actually pull off this mission, we wanted to record it for all time. Cameras to take still pictures as well as video were a must. Apollo 11 carried a number of cameras for collecting data and recording various aspects of the mission. Cameras to be operated by the astronauts needed to meet special temperature and power requirements due to the moon’s atmosphere, had to be specially engineered for the unique lighting challenges, and of course, had to have big buttons in order for the astronauts to operate them with their giant gloves on! [McMahon showed a few photos taken with these cameras: the first picture taken by Neil Armstrong after setting foot on the moon, Buzz Aldrin setting up a solar wind experiment, Buzz with the American flag, Armstrong in the lunar module after walking on the moon, Earth from Lunar orbit before landing]

Why stop with still photography? While we were at it, how about we take video — and, even better, broadcast some of it on TV!

They had communications systems in place for our earlier space travels, but to go to the moon was much farther. They had to come up with a better and more robust system to reach the moon. The solution was called Unified S-band or USB. Please note, this is not the USB ports that we use today to charge our phones. It was a type of radio signal. It combined tracking, ranging, command, voice and television data into a single antenna on the lunar module. Given that there needed to be room for all of the data transfers, only 700 kHz could be allotted for a television down link. The problem was that this wasn't enough bandwidth for the standard TV video camera of the day, and NASA needed a special, smaller format camera. So they had one specially invented.

The TV broadcast camera was designed by Stan Le-BAR. ... The cameras were small and light weight, designed to withstand the punishing forces of launch, the subsequent sudden weightlessness, and the striking temperature differences in space.

NASA used a scan converter to enlarge the TV camera image to a broadcast standard format. We’ve all seen what it looks like when you take a low-resolution picture and try to make it bigger and it gets all pixelated .... That’s the first reason the broadcast was such low quality. The second reason for the degraded TV image is that the signal was bounced around quite a bit before it reached living rooms. It was sent from the antenna on the LM to three tracking stations, one in California and two in Australia. Then, the tracking stations transmitted the signals to satellites and AT&T landlines to Mission Control in Houston at which point they were broadcast to the world. The daisy chains and translation process left the image significantly degraded, but it was still live footage of the first steps on the Moon, and arguably the biggest television moment of all time.

[McMahon then showed] a split simultaneous video of the recordings of two video cameras — the lunar module sequence camera (on top) and the TV broadcast camera (bottom)., [including the famous: One small step for a man, one giant leap for mankind].

I’ll end with this picture of the plaque that the astronauts left on the moon. It reads: Here men from the planet earth first set foot upon the moon, July 1969, AD. We came in peace for all mankind.

This story does not just belong to the astronauts, however. A description of the 2015 book Team Moon sums it up pretty well:

"For Apollo 11, the first moon landing, is a story that belongs to many, not just the few and famous. It belongs to the seamstress who put together twenty-two layers of fabric for each space suit. To the engineers who created a special heat shield to protect the capsule during its fiery reentry. It belongs to the flight directors, camera designers, software experts, suit testers, telescope crew, aerospace technicians, photo developers, engineers, and navigators."

As I alluded to earlier, and I hope I’ve demonstrated now: it was the perfect combination of human intellect, teamwork, innovation, technology and a little bit of luck — happening on a scale that has yet to be surpassed.