'Walking Mom' Programmer Who Achieved Humanity's First Moon Landing Success [Juhyung Lim's Tech Talk]

Margaret Hamilton, Creator of the First Spacecraft Software in the US
Discovered Critical Computer Error While Watching Daughter Play
Prevented Malfunctions with 'Error Avoidance Program' She Developed
Recognized for Moon Landing Success, Awarded Presidential Medal of Freedom in 2016

On July 20, 1969, astronaut Buzz Aldrin is climbing down the ladder of the lunar module onto the surface of the moon. / Photo by Yonhap News

[Asia Economy Reporter Lim Juhyung] According to the Korea Aerospace Research Institute on the 25th of last month, Korea's first lunar probe will leave Earth and enter lunar orbit on August 1, 2022. The lunar probe will orbit the moon for one year, conducting exploration of the surface and atmosphere.

Including the Korean lunar probe, all artificial satellites orbiting satellites and planets beyond Earth today are equipped with state-of-the-art onboard computers. These computers not only manage complex devices such as power control units, distribution units, and data processing units within the probe, but are also crucial for running flight software that ensures the probe safely settles into orbit.

However, in the past, high-performance computers like onboard computers did not exist. In particular, the lunar lander 'Apollo 11,' which was the first to land on the moon's surface, had to rely on the 'Apollo Guidance Computer,' which had much lower performance than modern smartphones.

The Apollo Guidance Computer was a 32kg direct circuit computer that controlled most of the probe's equipment, including telescopes, inertial measurement units, manual gears, control devices, radar, and engines.

This computer stored data through a handcrafted 'core rope memory.' This memory chip was made by weaving copper wires into the chip like a skein of thread, and it could only store 2.5MB of data in a size as large as a large refrigerator.

The Apollo Guidance Computer (above), the onboard computer of Apollo 11, and the core rope memory. / Photo by NASA. Screenshot from the internet homepage

However, the biggest problem was the errors occurring in the guidance computer. At that time, if the guidance computer had to process commands beyond its limit, it would overload and the system would stop working, a fatal issue. While ordinary computers can be 'rebooted' by turning off and on again when a system error occurs, this was practically impossible during the spacecraft's takeoff and landing stages, where every second counted.

The first person to discover these errors in the guidance computer was Margaret Hamilton, a female engineer who was the head of NASA's flight software design team at the time.

Hamilton was hired as a programmer at the Massachusetts Institute of Technology (MIT) at the age of 24 and became the lead software engineer for NASA's lunar landing software in 1965. It is said that she was so passionate about engineering that she would bring her young daughter Lauren to work and take care of her while coding.

One day, Hamilton witnessed Lauren playing with the guidance computer simulator and causing a computer error.

Afterwards, Hamilton became concerned that astronauts aboard Apollo 11 might make the same mistakes as her daughter, causing computer errors, and decided to develop 'error-avoidance software' as a solution.

Margaret Hamilton, NASA software design team leader, standing next to the navigation software program code list of the Apollo Guidance Computer. / Photo by Internet homepage capture

The error-avoidance software developed by Hamilton assigned priorities to the commands the computer had to process. If the computer was overwhelmed by too many commands and stopped working, lower-priority tasks would be halted, and essential tasks would be reset and processed again. Hamilton created tens of thousands of punched cards to build this program and installed it on the guidance computer.

In fact, NASA initially believed Hamilton's error-avoidance program was unnecessary, thinking that professionally trained astronauts would not make mistakes.

However, on July 20, 1969, the Apollo 11 spacecraft carrying NASA astronauts Neil Armstrong, Michael Collins, and Buzz Aldrin experienced the computer malfunction Hamilton had feared just before lunar landing. Thanks to the error-avoidance program developed by Hamilton's software team, the lunar landing was successfully completed, and the mission was accomplished with a safe return.

On November 22, 2016, Hamilton received the Presidential Medal of Freedom from then U.S. President Barack Obama for her contributions to the success of the Apollo 11 lunar landing. The historic achievement of landing on the moon was made possible because of engineers who worked to solve seemingly minor errors that no one else had noticed.