Digital Apollo: Human and Machine in Space Flight (review)

Spaceflight enthusiasts disappointed by the lack of popular interest in interplanetary adventure should take heart in two developments: first, the plethora of new literature on Project Apollo; and second, the fact that while space fans may be fewer than in ages past, they are almost certainly better. Empowered by an internet full of simulation software, astronautics addicts have traded Star Wars for systems engineering, showing their devotion by mastering the switches, buttons, and readouts of Apollo’s “man-machine” interface. It is this seemingly snooze-worthy system of technologies that David Mindell describes with great flair in his much-anticipated Digital Apollo. Coming on the heels of his work on human-factors engineering and analog computing, Mindell’s exhaustive research on the Apollo Guidance Computer (AGC) has spawned a history of both the groundbreaking digital electronic computers that steered Apollo spacecraft to the moon and the analog organic computers—especially the astronauts of the National Aeronautics and Space Administration—who designed, refined, and “flew” these marvelous gizmos.

Digital Apollo aims to be more than a hardware history: the questions perplexing NASA’s leadership in the 1960s were fundamental ones about humankind’s role in an increasingly sophisticated mechanical universe. Mindell’s account begins with an event that some might see as a colossal screwup: the overload of the computer that guided Apollo 11’s Neil Armstrong and Buzz Aldrin to the lunar surface in July of 1969. Instead of concluding that Apollo’s guidance hardware was a mess, Mindell sees the episode as a vindication of NASA’s efforts to integrate human and machine into hybrid systems with greater reliability than either alone (indeed, Armstrong landed despite the alarms). Before describing the development of the AGC, though, Mindell recounts the rise of the meat sacks who operated it: “testy” test pilots who, during the late 1950s, struggled to master new flying machines so fast that human reflexes could barely cope. With Armstrong and others in the cockpit, the experimental, rocket-powered X-15 aircraft reaffirmed the role of human piloting in space, albeit with the help of a “black box” that translated movements of the pilot’s control stick into a more complex language of rudder deflections and thruster firings.

Not surprisingly, the first few years of the space race were occupied by a debate about whether America’s answer to the Soviet launch of Sputnik in 1957 would be a smartman in a dumb spaceship, a dumbman in a smart spaceship, or something in between. Instead, America got a smart man in a smart spaceship, and all of the technical problems, training burdens, and workplace conflicts that approach entailed. NASA’s astronauts lobbied to keep piloting at the center of the space program while recognizing that spaceflight required more than the cockpit instrumentation they knew best. Together with like-minded NASA managers, they saw to it that America’s spacecraft (the first of which flew unpiloted) became less automatic as time went on, with the help of advances in hardware, software, and “peopleware.” Designed at Charles Stark Draper’s Instrumentation Laboratory at MIT, the AGC was the little black box that could: with all the real-time computing muscle of a digital watch, the twin “fly-by-wire” computers on Apollo’s command and lunar modules interacted with keypads, stick controllers, gyroscopes, radar, and optical telescopes to enable human pilots to fire their rocket thrusters accurately without any help from the ground.

Was the AGC the best solution? We may never know: NASA bought it without investigating alternatives. Donald MacKenzie, in Inventing Accuracy, suggested otherwise: Draper’s insistence on autonomous guidance added needlessly to Apollo’s complexity. Nor were the AGCs the only computers under Apollo’s hood: an analog thruster controller by Honeywell, a launch vehicle guidance system by IBM, and an abort computer by TRW also worked well but earn little mention in Digital Apollo.

Unquestionably, though, the AGC excelled at keeping humans “in the loop,” a critical requirement...