Margaret Hamilton, computer pioneer who led software development for the Apollo program, dies at 90 | MIT News

“Defensive” programming and priority-driven software take humans to the moon

Hamilton discovered a talent for leadership, as well as a keen instinct for problem solving and critical thinking that proved several times capable of saving the Apollo project.

There was the incident known as “the Lauren mistake”: one day, his daughter Lauren, then four years old, was playing with the command module simulator in the instrumentation lab when she somehow activated a pre-launch program, called P01, while the simulator was in mid-flight – causing the simulator to completely crash. Hamilton created a program add-on in the technical documentation warning users not to launch P01 during flight.

She also proposed a software fix to prevent the error from occurring during a real mission, but it was rejected on the grounds that highly trained astronauts would never make the same mistake. Yet during the Apollo 8 mission in 1968, that’s exactly what happened: Jim Lovell inadvertently launched P01 during flight, causing in-flight navigation data to disappear. Hamilton and his team were called in to resolve the error, and then the proposed changes were incorporated into the program. This was an early example of “defensive” programming, the practice of creating software that can anticipate or correct errors on its own.

Hamilton’s most famous contribution to the Apollo program came during the crucial Apollo 11 mission to land on the Moon in July 1969. Moments before the Eagle module was ready to land on the lunar surface, the onboard computer sounded the alarm. He had detected an error 1202: the computer was overloaded due to a fault in a hardware switch, and the system might not be able to handle the complex landing procedure.

But Hamilton and his team had designed priority-driven software that could stop unnecessary background tasks in order to prioritize critical tasks. Houston trusted Hamilton’s software and allowed the mission to continue, and two men walked on the moon for the first time.

Later career and legacy

Hamilton continued to work at the Instrumentation Laboratory into the 1970s. At the end of the Apollo program, the Instrumentation Laboratory separated from MIT to become the independent Draper Laboratory.

“Margaret left an indelible mark on Draper, and we will be forever grateful,” said Jerry M. Wohletz SM ’97, PhD ’00, Draper’s president and CEO. “Through her leadership and contributions to the development of onboard flight software for NASA’s Apollo guidance computer, she helped ensure that the Apollo astronauts landed safely on the lunar surface and returned home safely. We will forever honor her legacy at Draper.”

Hamilton then established his first software company, Higher Order Software, in 1976. The company was based on Hamilton’s software engineering approach to error prevention and fault tolerance.

A decade later, Hamilton founded another software company, Hamilton Technologies, “to provide products and services to modernize planning, systems engineering, and software development processes to optimize reliability, reduce costs, and accelerate time to market.”

Hamilton Technologies’ flagship product is Universal Systems Language (USL), a systems modeling language and methodology for engineering complex software systems that prioritize error prevention and defensive programming.

Throughout his career, Hamilton worked to gain recognition for software engineering as a dedicated discipline.

“I fought to give software legitimacy so that it – and those who build it – received the respect it was due, and so I began using the term ‘software engineering’ to distinguish it from hardware and other types of engineering, while treating each type of engineering as part of the overall systems engineering process,” Hamilton said. El País in 2018. “When I started using this expression, it was considered quite amusing. It was a joke for a long time. They liked to fool me about my radical ideas. Software eventually and necessarily gained the same respect as any other discipline.”

Among his many awards and honors, Hamilton received the NASA Exceptional Space Act Award for scientific and engineering contributions in 2003; the Computer History Museum Fellow Award in 2017; the Intrepid Lifetime Achievement Award in 2019; and induction into the National Aviation Hall of Fame in 2022.

Later in her life, Hamilton became an icon for women in science and technology, particularly after a now-famous photo, showing her next to a printed copy of her MIT team’s Apollo code, began circulating online. In 2015, the Apollo software she helped develop was added in its entirety to the code-sharing site GitHub. And in 2017, she became an official Lego minifigure after a set originally designed by MIT science communicator Maia Weinstock, in honor of her and several other women in NASA history, became available worldwide.

“Margaret Hamilton was an inspiration to generations of computer scientists and engineers. Her career was dedicated to preventing errors and what she called ‘dealing with the unknown,'” says de Weck. “She exemplified leadership by example and established a software engineering practice based on problem solving and systems engineering from which we all benefit.”

Hamilton is survived by his daughter, Lauren Hamilton; his son-in-law, Richard Selesnick; two grandsons; and four great-grandchildren. A memorial service will be held in the spring in Cambridge, Massachusetts.