-
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.