Colossus and Luminary: The Two Souls of Apollo's Flight Software
How two separate AGC software packages—one for the Command Module, one for the Lunar Module—were built by competing teams under impossible deadlines
• Matt Dennis
The Digital Autopilot: How the AGC Flew a Spacecraft with Reaction Jets
The software that translated guidance commands into precisely timed thruster firings—managing attitude, translation, and engine gimbal across every phase of flight
• Matt Dennis
The DSKY and PINBALL: How Astronauts Talked to a 1960s Computer
The electroluminescent display, the Verb-Noun grammar, and the 4,000 lines of I/O code that gave Apollo crews a conversation with their guidance computer
• Matt Dennis
Erasable Memory: Managing 2,048 Words of RAM on the Way to the Moon
How the AGC's programmers divided 4 kilobytes of magnetic core RAM among navigation, guidance, autopilot, and display—and why every word was a negotiation
• Matt Dennis
The Executive and the Waitlist: The AGC's Real-Time Operating System
How a 70-pound computer with 2K of RAM ran a priority-based multitasking OS that could shed its own workload mid-landing to keep astronauts alive
• Matt Dennis
P52: The Star Alignment Program Every Apollo Astronaut Had to Master
How astronauts sighted stars through a sextant to align the AGC's inertial platform—the ritual that kept Apollo on course across 240,000 miles
• Matt Dennis
P63, P64, and P66: The Three Programs That Landed on the Moon
The AGC software sequence that guided the Lunar Module from orbital velocity to touchdown—braking, approach, and the final manual phase that put Armstrong in control
• Matt Dennis
The Interpreter: A Virtual Machine Inside the Apollo Guidance Computer
How MIT built a double-precision math engine on top of the AGC's primitive instruction set—a software layer that made lunar navigation possible
• Matt Dennis
P20 and P22: How the AGC Tracked a Target Across Lunar Orbit
The rendezvous navigation programs that let two Apollo spacecraft find each other above the Moon—using radar, optics, and orbital mechanics solved in real time
• Matt Dennis
Restart Protection: The AGC Software That Could Reboot Itself Mid-Flight
How the Apollo Guidance Computer's restart system preserved critical state across software restarts—a fault-tolerance design that kept computing through failures
• Matt Dennis
Unified S-Band: One Radio System for Everything
How a single microwave communications system handled voice, telemetry, ranging, television, and computer uplinks between the spacecraft and Earth—a quarter million miles of radio link
• Matt Dennis
Orbital Mechanics by Hand: How the AGC Solved Lunar Rendezvous
The terrifying math behind finding a tiny spacecraft in lunar orbit, and the backup plan that used a sextant and a stopwatch
• Matt Dennis
The Apollo Guidance Computer: Programming the Moon Landing
How a 16-bit computer with less memory than a greeting card guided astronauts to the moon and back
• Matt Dennis