Margaret Hamilton, the computer science pioneer who led the development of flight software for NASA’s Apollo missions and coined the term software engineering, has died at age 90. Her code famously rescued the Apollo 11 moon landing from a computer overload just minutes before touchdown in July 1969.
Margaret Elaine Heafield was born on August 17, 1936, in Paoli, Indiana, to poet and college professor Kenneth Heafield and high school teacher Ruth Esther Heafield. She studied mathematics at the University of Michigan and Earlham College, graduating with a bachelor’s degree in mathematics in 1958 with a minor in philosophy. In 1959, she moved to Greater Boston with her first husband, James Cox Hamilton, whom she had met at Earlham and who was studying law at Harvard and Brandeis. That same year, she took a job at MIT writing weather prediction software for meteorologist Edward Norton Lorenz, working on LGP-30 and PDP-1 computers at Marvin Minsky’s Project MAC. When she moved on in 1961, she hired and trained Ellen Fetter as her successor. Between 1961 and 1963, she worked on the Semi-Automatic Ground Environment (SAGE) project at MIT’s Lincoln Laboratory, writing software and coding the AN/FSQ-7 prototype computer utilized by the U.S. Air Force to spot potential enemy aircraft, while also contributing to satellite tracking efforts for the Air Force Cambridge Research Laboratories.
Leadership at the MIT Instrumentation Laboratory and the Apollo Software Division
In 1965, Hamilton joined the Instrumentation Laboratory at the Massachusetts Institute of Technology, which secured a contract with NASA in 1961 to develop the onboard flight software for the Apollo program’s command and lunar modules. She initially wrote software for uncrewed Apollo missions before leading development for the crewed program. Recalling her early days at the lab, Hamilton described how upper management gave her team total freedom because software was a complete mystery to them. Because software was a mystery, a black box, upper management gave us total freedom and trust
, she said.
Early in her tenure, Hamilton was handed a notoriously difficult program written by another programmer whose comments were entirely in Greek and Latin. After figuring it out, she wrote a small backup program named Forget It
intended for abort procedures. When an uncrewed flight aborted, the system executed her program, instantly establishing her reputation. It went to [run] this program I had written, which I named Forget It. All of a sudden, I became an overnight expert
, she recalled.
The 1202 Program Alarm During the Apollo 11 Lunar Landing
Because Hamilton and her team had engineered priority-driven software capable of shutting down unnecessary background tasks to preserve vital landing functions, the computer kept running. Computer engineer Jack Garman advised guidance officer Steve Bales that the alarms did not require an abort, and Bales confirmed, We’re go on that alarm
. NASA noted that the software intervention permitted the mission to safely continue, allowing two men to walk on the moon for the first time.
Hamilton Popularized Software Engineering to Gain Professional Respect
While working on the space program, Hamilton popularized the term software engineering
to give code the same level of professional respect afforded to hardware and other traditional engineering disciplines. I fought to bring the software legitimacy so that it — and those building it — would be given its due respect, and thus I began to use the term ‘software engineering’ to distinguish it from hardware and other kinds of engineering, yet treat each type of engineering as part of the overall systems engineering process
, she told El Pais in 2018. She also pioneered defensive programming, a methodology designed to build software capable of anticipating or fixing errors on its own.
Her daughter Lauren’s accidental crash of a prelaunch simulator during a test run inspired Hamilton to build protective backstops into flight software to prevent astronauts from encountering identical software failures mid-flight. Her conceptual frameworks—including asynchronous software, priority scheduling, end-to-end testing, and man-in-the-loop decision capability—became foundational to ultra-reliable software design.
Post-Apollo Entrepreneurship and Later Career
As the Apollo program wound down, the Instrumentation Lab spun out from MIT to become the independent Draper Laboratory. In 1976, Hamilton founded her first software company, Higher Order Software, based on error prevention and fault tolerance principles. A decade later, she founded Hamilton Technologies. In 2016, President Barack Obama presented her with the Presidential Medal of Freedom, the nation’s highest civilian honor. Her career was further recognized when she received the Computer History Museum Fellow Award in 2017, the Intrepid Lifetime Achievement Award in 2019, and admission into the National Aviation Hall of Fame in 2022.
The lifetime achievement honor of the 2025 Michael Collins Trophy was presented to her by the Smithsonian’s National Air and Space Museum.
To say Hamilton was a pioneer – to say she was ahead of her time – would be a dramatic understatement.
Hamilton died on September 30 at CHA Cambridge Hospital at the age of 90. Surviving family members include her daughter Lauren Hamilton, son-in-law Richard Selesnick, two grandsons, four great-grandchildren, and siblings John, David, and Kathryn Heafield. A memorial service is scheduled to take place in the spring in Cambridge, Massachusetts.
Having reached the age of 90, Margaret Hamilton—the computer scientist whose pioneering research enabled NASA astronauts to reach the Moon—has passed away.
A 1969 photograph featuring Margaret Hamilton alongside the code listings created by her team for the Command Module and Lunar Module of the Apollo program
