Transcriber: Eriko Tsukamoto Reviewer: Hiroko Kawano
There's several parts of my story
that some people find difficult to believe these days.
One of them is the way I got a job working on the Apollo project.
Another is the relationship that sometimes developed
between the coders like me and our end users, the astronauts.
That's my main topic, and I'll get back to it in a minute,
but first, how did I get the job?
Well, it was the summer of 1966,
and I'd just graduated from Boston University a year late
with a not very illustrious degree in mathematics.
I was tramping around town to job interviews
and getting used to being rejected.
I had heard a bit about the MIT instrumentation lab
under the leadership of Professor Charles Stark Draper,
known as Doc Draper.
It had become the world's leading authority in inertial guidance systems.
And in 1961,
it received the first contract of the Apollo program
to provide the primary guidance system for the Apollo spacecraft
that would go to the moon.
"Why would an elite organization like that be interested in a person like me?"
I wondered.
But I didn't have much to lose.
I happened to walk by the lab
on my way back from yet another dispiriting interview.
I said, "Here goes nothing," and walked in and asked for a job.
If my self-esteem had been higher, I would have hesitated for longer.
My timing, it turned out, was lucky:
they needed bodies and were hiring.
I was interviewed on the spot by personnel officer John McCarthy.
And I suddenly realized that he was trying to sell me on the job
instead of the other way around.
(Laughter)
He passed me on to George Cherry,
who ran the programming effort for the computer on the lunar module.
That's the spacecraft - the Apollo spacecraft -
that would fly down from orbit
and plant its not-so-delicate feet in the moon dust.
I had no computer experience,
but George said he'd even hired literature majors.
He said, "Nobody knows much about programming a spacecraft computer,
and nobody knows much about landing on the moon.
We'll be the ones to figure out both."
My starting salary was $640 a month.
My good luck continued
when I was assigned to work with Allan Klumpp,
whose specialty was the powered descent.
That's the very tense 12-minute period
between lunar orbit and a soft landing on the surface.
It's the most dangerous phase of an Apollo mission
and also the most intense for the computer.
How do you land on the moon? Klumpp.
But it was a big job, and Allan needed help.
(Laughter)
We were a good team - his analysis and my code.
I won't dwell now on the limitations of the machine we were working with,
except to say it had 76 kilobytes of total memory,
and a thousand or so Apollo Guidance Computers these days
could be implemented on one chip.
Our first job was Sunburst,
the program for the first unmanned test of the lunar module in Earth orbit,
which flew in January of 1968.
I programmed the lunar landing guidance equation,
the throttle control routine and several other functions.
But we were already looking past Sunburst to Luminary.
That was the program that controlled the LM
when it attempted a real landing.
On November 6, 1967,
I was in my office, staring at a program listing,
when Allan sent someone to ask me to come to the classroom,
the room where we held large meetings.
Our higher-ups and our visitors from NASA sat around tables arranged in a wide U.
I sat down next to Allan Klumpp in the back.
I had heard that astronauts would be there, but where?
There was not a flight suit to be seen,
not even any snazzy knitwear.
(Laughter)
Allan had called me in
because the lunar descent was coming up for discussion - our baby.
A short balding guy in a glen plaid suit seemed to be running the meeting.
I took him at first for a particularly buoyant NASA manager,
but it turned out to be the astronaut Pete Conrad,
who would command the Apollo 12 mission
and be the third person to walk on the moon.
Off to the left sat Neil Armstrong and Jim Lovell,
who would command Apollo 11 and Apollo 13,
in dark business suits.
Armstrong brought up a subject
that would recur again and again over the next years:
fly to versus fly from.
It had to do with which direction to move the control stick
to get the desired result.
The best analogy -
if you have a trackpad on your computer -
is which way you have the scroll set.
Armstrong was bemused by the fact
that an instrument called the "cross pointers"
was mounted vertically
on the instrument panel of the lunar module,
whereas during the final part of the landing,
it was used to indicate velocities in the horizontal dimensions.
For Armstrong, that created an ambiguity.
I thought it was a window into astronaut thinking,
and so was the next item.
For general purpose display of information to the crew,
the computers only means was the display keyboard
that we call the "dis-key,"
and the dis-key had three five-digit registers
for displaying numeric information.
And during the whole course of the lunar landing,
two of those were devoted to the vital numbers:
altitude, as you might expect,
and rate of descent.
So that left one register of five digits for other uses.
The landing was divided into three phases.
There was the long braking phase,
and that was followed by a phase of about a hundred seconds,
when the spacecraft would still be under automatic control
but the surface of the Moon ahead
would be visible through the LM's front windows.
During the visibility phase,
we provided something called the "landing point designator."
The idea was that we would compute and display an angle
that told the commander, who stood on the left side of the cockpit,
where to look along a scale on his window
to see the spot
where the spacecraft would touch down if he took no further action.
The problem
was that Pete Conrad thought that two numbers were actually needed:
not just the look angle, of course,
but he also wanted to know the amount of time remaining
during which a redesignation would be permitted.
Discussion ensued upfront,
but sitting in the back of the room,
I realized that I could easily compute a five-digit number
that had the time remaining in the first two digits
and the look angle in the last two digits.
"I think there's a way of having both numbers," I said aloud.
Allan, next to me, gave a little jump,
and at the front table,
the heads craned around to see who had spoken,
and I explained.
Pete Conrad said, "Are you sure about that?"
"Perfectly sure," I said.
With that, Conrad turned to his fellow astronauts at the table
and said, "We should have had this guy at that meeting last week!"
(Laughter)
There's another reason I remember the date of that meeting.
That evening I had returned to the lab to check on a simulation.
And on my way home, on my motorcycle,
just before midnight,
Conrad's quip still buzzing in my ears,
I was struck on the left side by a turning car.
I came to rest on the pavement
with my left femur displaced
about 30 degrees to the left at the midpoint.
The next afternoon at the Mass General,
Dr. Robert Boyd pounded an intramedullary rod into my femur.
It was a procedure that was invented during the Second World War
by a German surgeon named Küntscher
in order to get pilots back into the air more quickly.
I was off crutches by Thanksgiving
and playing tennis at six months from the injury -
finally something to thank the Luftwaffe for.
(Laughter)
For each mission, we held a crew training meeting
where we briefed the crews
and they had an opportunity to question us.
The meeting for Apollo 11 was held in a big room in Houston,
crowded with spectators.
George Cherry made our presentations.
When it came to the visibility phase and the redesignation capability,
Armstrong said he did not intend to use it except maybe once to show us it worked.
That was sort of disappointing,
but during a break, I saw Armstrong standing by himself in the corridor,
and I walked over.
I told him that we had tested the heck out of the redesignation logic
and he shouldn't hesitate to use it
"if you see something interesting down there."
"Well, Don," said Armstrong,
"any place I can succeed in landing on the moon will be interesting."
(Laughter)
I still cringe a little.
I know now what I should have said:
"First landing, lumpy moon, probability of navigation errors.
You may not be coming down exactly where you expect.
If you use the redesignator early in the phase
to bend your trajectory,
maybe you won't have to scare us all to death
by nearly running out of fuel while you maneuver in the final phase."
(Laughter)
In the event,
Apollo 11 landed about four miles from where it was supposed to land.
It was a triumph: it was the moon.
As Armstrong had said, "Anywhere would be interesting."
I did wonder how he remembered my name, however.
It turned out he'd been reading my memos.
In a book that came out the next year,
he cited one of my memos
as an example of the arcane jargon that was spoken by the computer people.
(Laughter)
I'd written the memo for a very select audience
who would understand every word,
my fellow coders.
The wonder of it was that such a memo
would have crossed the desk of an Apollo mission commander.
At any rate,
on the next mission, Apollo 12,
it was going to be necessary to land to make a pinpoint landing.
That was going to be necessary
in order to go to the places that the geologists were interested in.
And so Pete Conrad, on Apollo 12,
was assigned the goal of landing within walking distance of Surveyor 3,
an unmanned spacecraft that had landed on the moon in 1967.
Some software changes were necessary -
we put in the capability to put in a very last minute correction
based on tracking data
taken when the LM came out from behind the moon
for the last time before it attempted the landing.
And immediately, Conrad invited Allan Klumpp and I
to come down to Cape Canaveral to explain the new capability to him
and also, I think,
to show us what the lunar landing looked like from his point of view.
The best place to do that was the LM mission simulator
at Cape Canaveral.
There it is.
We had our own plywood cockpit in Cambridge,
but here, the cockpit was realistic to the last degree
and accurate views of the lunar surface were provided for the LM's windows.
Allan and I flew a couple of lunar landings,
and later, I flew a few more with Pete Conrad at my left shoulder.
The crew training meeting for Apollo 12 was also at Cape Canaveral,
in a small room in the crew training building.
Pete Conrad wanted to keep away the managers
who had thronged the meeting in Houston.
The astronauts seemed more comfortable at Cape Canaveral
than they did in Houston.
This time, I was one of the presenters.
At one point, Conrad went through the procedures he would go through
if the engine designed to lift him off the lunar surface on the way home
failed to fire - ending -
and if that didn't work, that would spoil our whole day.
(Laughter)
In astronaut speak,
that's as bad as it can ever, ever be.
In the event,
Conrad's mission got off to a brilliant start by -
when the rocket was struck by lightning right after tower clear.
But there was no permanent harm done.
They went on to the moon.
Conrad and his fellow LM crewman Al Bean
brought home pieces of the Surveyor spacecraft.
But there's nothing funnier in the space program, in my opinion,
than listening to Pete Conrad giggle his way into orbit
with practically every warning light in the cockpit lit up.
(Laughter)
It was probably around the time of the crew training meeting
for Apollo 14,
which was right before Apollo 13 flew,
that John Young came over to me and introduced himself.
He had been named to be commander of the Apollo 16 mission,
and he wanted to talk about an idea
that would have made it possible to land the LM in a hatbox.
The idea was to repurpose the look angle
that we had used during the visibility phase.
But this time, it would indicate a spot on the moon
over which the LM would come to a stop
if, at that moment, he switched back to auto control
to let the computer null out any remaining horizontal velocities.
It was a brilliant idea.
We flew a few landings that day.
And then, a month or so later,
now after Apollo 13,
I flew back to the Cape with a big reel of magnetic tape in my bag.
And after a few days
waiting for the big boys to relinquish the simulator,
the Apollo 14 crew,
Young and I flew a series of landings using the new capability.
"It's the slickest thing I ever saw," he said.
The trauma of the nearly disastrous Apollo 13 mission was still very fresh,
and I would not have brought it up,
but Young did.
"I went home and cried," he said,
"I didn't think the guys were coming home."
Of course, soon enough, he was back in the simulator,
helping to verify the procedures
that had to be developed to bring them home.
We never were able to get approval
to put the new capability into the flight code,
but we had advanced
the state of the art for landing on a poorly mapped, airless body.
During Apollo, the coders and the astronauts talked directly.
We worked together to a common goal,
to make landing easier and more accurate.
On our side, within the culture created at the lab by Doc Draper,
we had the freedom to take the initiative.
We had a powerful technology in our hands.
We could go from a new idea
to a program that could be flown in the simulator quite quickly,
and we had plenty of ideas.
We were connected to everything about the mission -
everything from an errant transistor deep in the electronics
to major operational decisions.
But we felt a special kinship with the astronauts
because our thoughts - the thoughts that we'd lent to the computer -
were literally in the cockpit with them, helping to operate the spacecraft.
A junior software engineer on one side, a crack pilot,
an astronaut on the other -
on the astronaut side,
an astronaut with an idea like John Young could corral a willing software engineer
and within a fairly short amount of time
have a customized version of the program that he could play with in the simulator.
What we had in common was the spirit of exploration,
which in my opinion was not so different from the spirit of exploration
that was active in the culture in the 1960s and the early 1970s.
We were primed for adventure.
We valued our freedom more highly than we valued our safety or our income.
Perhaps that same spirit will have to return to the culture
before we can enter a new golden age of space exploration.
Thank you.
(Applause)