The NASA space project advanced the technological progress of the human
race by leaps and bounds. Examples of these revolutionary developments abound.
But one extra-special item was in its computer.
The Apollo Guidance Computer or AGC was one of the first to use silicon-based integrated circuits.
Their adoption heralded a revolutionary technology about to make a titanic impact on the world.
And the beginning of Silicon Valley as we know it.
I try not to make videos about America because it gets me yelled at but I really like this topic.
In this video, we are going to look at how the silicon integrated circuit
supercharged the AGC and guided us - literally - to the moon.
## Navigating
When President Kennedy challenged America to put a
man on the Moon - and bring him back safely, that part matters! - in 1962,
the United States had about 15 minutes total experience putting humans into space.
There were many unknowns NASA had to solve. But one of the biggest was navigation.
How to guide the spacecraft so that it can travel 400,000 kilometers through space,
and then properly enter orbit 110 kilometers above the surface of the Moon?
The velocity has to be just right.
Miss it by a few percentage points too low and Apollo hits the Moon.
A few percentage points too high and Apollo swings into an erratic orbit that they cannot exit.
To illustrate the enormity of the task, the Pioneer 4 space probe had been launched just a
few years prior to JFK's speech with the intention of taking radiation measurements of the moon.
Pioneer 4 traveled fast enough to exit Earth orbit but a small timing error in the rocket
booster stage swung the little probe too far out. It ended up missing the Moon by about
27,000 kilometers - too far to trigger its photoelectric sensor.
But hey. 27,000 kilometers is no biggie, right?
## Instrumentation
In August 1961, NASA handed out its first contract for the future lunar mission.
That contract went to the Instrumentation Lab at the Massachusetts Institute of Technology,
or MIT for a guidance and navigation system.
The Instrumentation Lab would eventually be renamed the Draper Lab in 1970
and was spun off from MIT in 1973 due to protests regarding their weapons work.
The Lab came up with a system based on their previous work
for the Polaris ballistic missile - which was fired out of a submarine.
Their system is best described as an inertial system - a self contained
system with a basketball-sized sensor with three
gyroscopes at its heart. Gyroscope technology would greatly advance during this time.
The system would also use a general-purpose
computer to calculate the craft's position, orientation and velocity.
Periodically, the astronaut would take star readings using a sextant and feed their
observations into the computer. And to measure drift, astronauts would find a known star,
center the ship's optics towards it, and press a button. The computer does the rest.
This approach was controversial. The astronauts were former pilots,
so they wanted to control their spacecraft just like a military aircraft.
Mission Control, for their part, wanted to guide Apollo themselves from the ground.
Luckily, MIT ended up getting their way. But their solution would require
a general-purpose computer. One that can be relied upon thousands of miles
away from the Earth. Determining how to achieve this led to a lot of heated debate.
## Reliability, Reliability, Reliability
Other options existed for achieving reliability. When Apollo lifted off,
the Apollo Guidance Computer wasn't the only computer onboard. Another,
less sophisticated digital computer was located further down inside the Saturn V rocket.
The Saturn's launch vehicle digital computer had no user interface but nevertheless
fulfilled a critical task. It provided the rocket's guidance and navigation functions,
sending commands to the engines to direct their thrust.
This rocket computer did not use integrated circuits. Its supplier
IBM knew that the technology existed but determined that it was not mature enough
for the task. They opted to stick with more traditional transistor technology.
Rockets are known to be volatile, high-temperature environments
subject to occasional high rates of acceleration. To ensure NASA's standards for reliability,
IBM built something they called TMR - which stands for "Too Much Reliability".
Just kidding, it really meant "Triple Modular Redundancy".
Here, IBM stuffed three identical versions of the launch computer's major circuits.
Then they added a voting circuit that selected the majority output in case one of them failed.
The Triple Modular Redundancy method worked perfectly and the Saturn V guidance computers
never failed during operation. Not even during that one time in November 1969 when lightning
struck the Saturn V after liftoff and wiped out the Apollo Command Module's electronics.
So the method had its supporters. NASA had engaged a branch of AT&T for technical
consulting and those guys recommended that IBM supply the Guidance Computer.
But MIT wanted to go another approach. The Guidance Computer needed to be more flexible,
more generalized. It had to accept inputs from people and other instruments. To achieve this
while meeting NASA's required reliability goals, they turned to an emerging electronics technology.
## Tubes to Transistors
Let us pause a little bit and recount some brief history from Tubes to Transistors to
Integrated Circuits. For a long time, computers depended on the vacuum tube.
Except vacuum tubes suck. They are unreliable, power-hungry, and extremely fragile.
So when the first transistor was invented in 1947, people hailed it as a vacuum tube
replacement for low-power, compact situations. Packaged into individual,
discrete items, you can plug them in to amplify electrical signals or switch them on or off.
But early Germanium-based transistors had their own problems. Manufacturers had trouble
producing these en masse. Furthermore, they were unreliable - breaking when shook or exposed to
extreme temperatures - and had to be connected together by hand. More on this second part later.
Despite these shortcomings, the industry - and particularly the
military - saw that transistors had a lot of potential. In 1953,
IBM debuted their first transistorized digital calculator - the IBM 608.
Armed with 3,000 Germanium transistors, the computer was 50% smaller than its predecessor.
And impressively, it used 90% less electricity.
Eventually, transistors replaced vacuum tubes in the electronics industry - spurred
on by manufacturing improvements that reduced cost and improved reliability.
## Fairchild
In the mid-1950s, the United States military started work on its next
big Intercontinental Ballistic Missile or ICBM - the Minuteman.
The Minuteman was a deterrence weapon designed to provide the United States
with second-strike capability. So if the Soviet Union were to ever nuke the USA,
a nuclear response would be guaranteed with a fast reaction time.
Minuteman needed to be on constant alert, with the ability to fire with less than an hour's notice.
Previous missiles had bigger bombs, but Minuteman compensated for that with a more
accurate guidance system. That guidance system - like Apollo's - was inertial.
In 1958, the US military chose North American Aviation's
Autonetics division as one of the prime contractors for this guidance system.
For their transistors, Autonetics in turn turned to Texas Instruments and a small
semiconductor manufacturing startup in Mountain View, California - Fairchild Semiconductor.
To meet Autonetics' strict reliability requirements, Fairchild put their
silicon-based transistors into centrifuges and subjected them to both hot and cold temperatures.
By 1960, the US military had bought more transistors for its missiles
than its space programs - $52 million to $33 million.
These early tests combined with the military's buying power allowed Fairchild to hone
their techniques and later evolve their transistor business into something bigger.
## Rise of the Integrated Circuit
The integrated circuit takes the transistor idea another
step forward. Remember what I said earlier about connections? Transistors are great,
but then you have to manually connect them together, often by soldering.
A circuit is only as reliable as its weakest link,
so manual errors in connecting them caused short circuits and failure modes.
The reason why an integrated circuit performs so much better
than its predecessors is that it is made of a single crystal of silicon.
Now you can make millions of transistors, resistors, and capacitors - the elements
of a circuit - and cram them together without worrying about the human manual effort element.
You get immense economies of scale, and escalating performance.
Famously, Jack Kilby of Texas Instruments first invented the integrated circuit
in 1958. He shared the Physics Nobel Prize for it in 2000.
But his integrated circuit invention wasn't commercially viable. The circuit's individual
elements - transistor, resistors, so on - were made of silicon. But they were connected with
individual gold wire. And like I said before, a circuit is only as good as its weakest link.
## The Planar Process
Then in 1959, one of Fairchild's founders developed what is called the "Planar" process.
Silicon reacts with the air to create a layer of silicon dioxide.
This layer had previously been a manufacturing nuisance and the layer was frequently removed.
But Fairchild learned to turn this nuisance into a benefit. That layer of silicon dioxide
protected the transistors from the outside environment, making them far more durable.
During manufacturing, you can cut holes in that layer to insert necessary elements.
Combined with the use of photolithography to deposit wires of aluminum for connection,
Fairchild managed to put many circuit elements AND their connections
onto a single piece of silicon - a monolithic Integrated Circuit.
Texas Instruments first invented the Integrated Circuit but Fairchild made it commercially viable.
So the lawyers at the two companies cross-licensed their methods.
Fairchild’s processes soon dominated the industry.
## The IC Difference
Integrated Circuits started making an impact on the industry as soon as they
were invented - if only because of the reliability and performance advantages.
In 1962, the United States military started the Minuteman II project,
a followup ICBM which required an even more powerful guidance system and computer.
For this reason, Autonetics chose to use integrated circuits for their
design - with Texas Instruments and Westinghouse as the main suppliers.
TI developed over two dozen IC designs for the Minuteman II. By 1965 they would be supplying over
15,000 circuits a week for the missile project. Demonstrations of the Minuteman
II guidance computer found that it performed dramatically better than the Minuteman I,
and word spread through the military. That word eventually reached the MIT Lab and NASA.
## Going IC
Apollo mission engineers knew about integrated circuits because they were at the cutting edge
of electronics development. 40% of their booster rocket budget, 70% of their spacecraft budget,
and 90% of its tracking/data budget was spent on electronic components.
MIT had ordered a few Integrated Circuit samples from Texas Instruments in 1959 and
1960 - basically soon after invention - in order to study their potential.
Then in 1961, Fairchild announced their Micrologic product line, selling them to government and
commercial clients at about $120 each, or about $1,200 today. Not an outrageous price at the time.
MIT ordered a few Micrologic products and found that they showed a lot of promise.
The product performed computational operations like multiplication,
addition, and branch logic over twice as fast compared to standard transistor parts.
Furthermore, the new computer would be two-thirds the size and weight.
And it would be cheaper too, reducing the number of unique logic modules inside the
computer from 34 to just one. You benefit from economies of scale.
But incorporating integrated circuits would require a radical and thoughtful
redesign. With integrated circuits, you are doing away with pre-packaged components.
You have to plan out everything the chip has to do before it goes to fabrication.
And there was only one supplier of Micrologic circuits at the time - Fairchild - which is
never a good situation. If Fairchild failed to deliver, then they were up a
creek. Other suppliers were eventually found but procurement would be a persistent pain.
Fortunately, the NASA program had the flexibility and open-mindedness to be
receptive to innovative solutions. In 1962, the MIT Lab engineers received
permission to rebuild the guidance computer based on integrated circuits.
This first iteration of the guidance computer would eventually be referred to as the Block
1. It was built with 4,100 integrated circuits, but all of them the same
circuit type. This was done for reliability and the aforementioned procurement reasons.
## Can We Rely On It?
Despite this decision, the big question remained. Is this thing going to work?
Can a computer based on integrated circuits be relied upon? It sparked a great deal of debate.
As I mentioned before, AT&T had recommended that NASA use the Triple Modular Redundancy approach
for the guidance computer. In their view, it was very likely that the computer would experience
some kind of failure during its trip to the moon. Can the astronauts repair the computer in space?
So NASA contracted IBM to study the Apollo requirements and see whether they would be
able to adapt the Saturn V launch computer to serve as the Apollo Guidance Computer.
IBM was like, "Yeah totally."
MIT engineers knew otherwise, of course. Their computer worked 10 to 20 times faster and
was more flexible. Furthermore, its position and velocity computational outputs were more
accurate than the Saturn computer's by a factor of five. They managed to fend off the notion.
Nevertheless, other parties joined the chorus. Grumman Aircraft was building the lunar module.
They thought the guidance computer wouldn't make it and proposed that
NASA build a fully separate and redundant backup for landing.
Grumman brought political pressure into the deal. Minnesota politician Joseph Karth wrote a letter
to NASA Administrator James Webb - the guy they named a telescope after. In the letter, he wrote:
> There has always been apprehension about the MIT
guidance system achieving the required reliability to ensure a safe mission.
Is there documented test-proven data to show that it will meet the needs of APOLLO/LEM?
He then asked about the backup guidance system.
Twice. In their reply, NASA mentioned that the Apollo mission carried two
guidance computers. And that they can always receive commands from Houston.
In the end, the MIT Lab made its final decision in wake of a near-disaster.
In May 1963, electronics for several critical systems in the Mercury-Atlas
9 - the last American solo orbital flight - failed near the end of the flight.
Pilot Gordon Cooper, like a boss, took manual control, re-entered the atmosphere,
and safely brought the flight back to Earth.
Later on, engineers determined that acids floating around in
the zero-G environment entered the electronics system and ruined them.
## Block 2
When the Mercury incident occurred, MIT engineers were in the midst of
bringing out the next version of the guidance computer - Block 2.
This version would be the one used for all of Apollo's manned missions.
Block 2 showed all the benefits of Moore's Law. It had more integrated
circuits from its predecessor - over 5,500 compared to Block 1's 4,100.
Yet it was smaller - reducing its overall footprint and cutting 17 pounds off the weight.
The 14 Block 1 prototype computers had been very reliable, having accumulated over 38,000
hours of operating time as of 1965. When properly made and sealed, they worked.
MIT thus decided that the best way to address the reliability issue was to seal it off from
the outside environment. Astronauts wouldn't be able to fix the computer if it failed mid-flight,
but those seals would protect it from outside damage.
NASA did build one final backup computer - the abort guidance system.
It was a general purpose computer supplied by a second group of
suppliers - TRW with integrated circuits from Fairchild competitor Signetics.
The abort guidance system was originally built
"just in case". But it was never needed and probably shouldn't have been built.
Later in 1975, NASA reflected that their resources probably would have been better spent reinforcing
the reliability of the primary system rather than creating entirely separate backup systems.
## Conclusion
It has been said that Apollo and the Minuteman II projects
helped fund or kick off the integrated circuit era. I probably wouldn’t go that far.
NASA chose ICs because they were faster, smaller, and eventually proved to be
as reliable as anything made before. But in 1962, at about $20-30 a piece,
they weren't cheaper than the incumbent technology of discrete circuits.
NASA and the military were fine paying these prices,
and they certainly helped the companies involved. But the commercial customers hadn’t yet signed on.
In 1961, Fairchild sold less than 5,000 Micrologic pieces. Texas Instruments
likewise was forced to cut pricing from $435 to just $76 90 days after launch.
The industry didn’t take off until 1964 when Robert Noyce and Fairchild decided to sell
their IC products at below cost - betting that they would make it up with scaling efficiencies.
Fairchild was right, of course. The year before the price cut, the industry sold 2.5 million ICs
in total. After the cut, just one of Fairchild’s orders would be for 500,000 ICs - 20% of that.
A year later in 1965, the same year Gordon Moore makes Moore’s Law, computer-maker Burroughs buys
20 million integrated circuits. By 1966, the whole industry knew that ICs were the future.
So I would argue that Apollo didn't kickstart the silicon revolution.
Rather, they tapped it and rode that rocket all the way to the moon.