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
How two separate AGC software packages—one for the Command Module, one for the Lunar Module—were built by competing teams under impossible deadlines
The software that translated guidance commands into precisely timed thruster firings—managing attitude, translation, and engine gimbal across every phase of flight
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
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
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
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
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
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
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
How the Apollo Guidance Computer's restart system preserved critical state across software restarts—a fault-tolerance design that kept computing through failures
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
The terrifying math behind finding a tiny spacecraft in lunar orbit, and the backup plan that used a sextant and a stopwatch
How a 16-bit computer with less memory than a greeting card guided astronauts to the moon and back