NASA’s first software engineer: Margaret Hamilton - Matt Porter and Margaret Hamilton

At roughly 4pm on July 20, 1969,

mankind was just minutes away from
landing on the surface of the moon.

But before the astronauts began
their final descent,

an emergency alarm lit up.

Something was overloading the
computer,

and threatened to abort the landing.

Back on Earth, Margaret Hamilton held
her breath.

She'd led the team developing the
pioneering in-flight software,

so she knew this mission had no
room for error.

But the nature of this last-second
emergency

would soon prove her software
was working exactly as planned.

Born 33 years earlier in Paoli, Indiana,
Hamilton had always been inquisitive.

In college, she studied mathematics
and philosophy,

before taking a research position at the
Massachusetts Institute of Technology

to pay for grad school.

Here, she encountered her first computer
while developing software

to support research into the new
field of chaos theory.

Next at MIT's Lincoln Laboratory,

Hamilton developed software for
America’s first air defense system

to search for enemy aircraft.

But when she heard that renowned
engineer Charles Draper

was looking for help sending mankind
to the moon,

she immediately joined his team.

NASA looked to Draper and his group of
over 400 engineers

to invent the first compact digital flight
computer, the Apollo Guidance Computer.

Using input from astronauts, this device
would be responsible for guiding,

navigating and controlling the spacecraft.

At a time when unreliable computers
filled entire rooms,

the AGC needed to operate without
any errors,

and fit in one cubic foot of space.

Draper divided the lab into two teams,

one for designing hardware and one
for developing software.

Hamilton led the team that built the
on-board flight software

for both the Command and Lunar Modules.

This work, for which she coined the term
“software engineering,"

was incredibly high stakes.

Human lives were on the line,
so every program had to be perfect.

Margaret’s software needed to quickly
detect unexpected errors

and recover from them in real time.

But this kind of adaptable program was
difficult to build,

since early software could only process
jobs in a predetermined order.

To solve this problem, Margaret designed
her program to be “asynchronous,”

meaning the software's more important
jobs would interrupt less important ones.

Her team assigned every task a unique
priority

to ensure that each job occurred in the
correct order and at the right time–

regardless of any surprises.

After this breakthrough,

Margaret realized her software could help
the astronauts work

in an asynchronous environment as well.

She designed Priority Displays

that would interrupt astronaut’s
regularly scheduled tasks

to warn them of emergencies.

The astronaut could then communicate
with Mission Control

to determine the best path forward.

This marked the first time flight software
communicated directly―

and asynchronously―with a pilot.

It was these fail safes that triggered the
alarms just before the lunar landing.

Buzz Aldrin quickly realized his mistake–

he’d inadvertently flipped the
rendezvous radar switch.

This radar would be essential on their
journey home,

but here it was using up vital
computational resources.

Fortunately, the Apollo Guidance Computer
was well equipped to manage this.

During the overload, the software
restart programs

allowed only the highest priority jobs
to be processed––

including the programs
necessary for landing.

The Priority Displays gave the
astronauts a choice––

to land or not to land.

With minutes to spare, mission
control gave the order.

The Apollo 11 landing was about the
astronauts, mission control,

software and hardware all working together
as an integrated system of systems.

Hamilton’s contributions were essential
to the work of engineers and scientists

inspired by President John F.
Kennedy’s goal to reach the Moon.

And her life-saving work went far
beyond Apollo 11––

no bugs were ever found in the in-flight
software for any crewed Apollo missions.

After her work on Apollo,

Hamilton founded a company that uses
its unique universal systems language

to create breakthroughs for systems
and software.

In 2003, NASA honored her achievements
with the largest financial award

they’d ever given to an individual.

And forty-seven years after her software
first guided astronauts to the moon,

Hamilton was awarded the presidential
Medal of Freedom

for changing the way we think
about technology.