always ask 'what if?'

Always Ask 'What If?'

The SRE mindset of continuous learning.

In 1968, Margaret Hamilton was working on the Apollo 7 Computer Guidance Software (AGC) to take astronauts to the moon. Margaret would take her daughter to work on some nights and weekends.

One day, her daughter Lauren came to work while the team was running mission scenarios on the hybrid simulation computer. As a young inquisitive mind, Lauren went exploring and playing Astronaut, but eventually caused a mission to crash. She had selected the P01 program while in-flight — an action that wipes out flight navigation data, making it impossible for the AGC to pilot the craft back to earth.

Margaret thought to herself, "What if the astronaut did what her daughter just did in flight?"

She submitted a program change request to add error checking code, but was told it wouldn't ever happen — the astronauts were well-trained and don't make mistakes. So instead, Margaret updated the documentation to say "Do not select P01 during flight."

Her safeguard was considered unnecessary until the very next mission. On Apollo 8, astronaut Jim Lovell selected P01 by mistake on Christmas Day. This was critical because without navigation data, the astronauts were never coming home. Thankfully, the documentation update had called this possibility out and was invaluable in recovering the mission.

The change request was approved shortly afterwards and added to all later flights.

"A thorough understanding of how to operate a system is not enough to prevent human errors." — Margaret Hamilton

Thoroughness, dedication, belief in the value of preparation and documentation, and an awareness of what could go wrong, coupled with a strong desire to prevent it — this is the SRE mindset.