Human and Machine

The Eagle's landing is a familiar story, one of the great technological mythologies of the twentieth century.1 I have retold it here by emphasizing elements that usually hide in the background: the interaction between human and machine, the role of the computer in mediating the astronauts' responses, the network of connections in space and on the ground (figure 1.1). Frequently mentioned but rarely analyzed, these relationships lie at the core of manned spaceflight since its inception, and they continue to frame questions surrounding our proposed future in space.

Figure 1.1

Jim Lovell on Apollo 8 aligning the optics for the Apollo guidance and control system. His left hand controls the spacecraft's attitude, while his right hand points the optics. (NASA JSC photo S69-35097.)

Figure 1.1

Jim Lovell on Apollo 8 aligning the optics for the Apollo guidance and control system. His left hand controls the spacecraft's attitude, while his right hand points the optics. (NASA JSC photo S69-35097.)

Human and machine: their relationship is not a new story. Indeed, it is one of the great narratives of the industrial world, from the mythical John Henry, who won a race with a steam drill at the cost of his life, to Charles Lindbergh, who used the word ''we'' to describe his partnership with his aircraft.2 Even during the 1960s, scholars and philosophers debated the appropriate trade-offs between automatic systems and human skills. Yet the many accounts of space travel have failed to explore this profound part of the venture. This book tells the story of the relationship between human and machine in the Apollo project and how that relationship shaped the experience and the technology of flying to the moon. It is a story of human pilots, of automated systems, and of the two working together to achieve the ultimate in flight. It is also a story of public imagery, professional identities, and social relationships among engineers, pilots, flight controllers, and many others, each with their own visions of spaceflight.

To engage the nation, NASA's publicity machine drew on age-old American icons of control and mythologies of individuality and autonomy, from cowboys to sea cap-tains.3 Apollo's astronauts shared their title with the men who plied the great river-boats down the Mississippi: they were pilots. From the beginnings of aviation up through Apollo and the spaceflight of today, the identity of the aviator-pilot shaped, and was shaped by, technologies of flight.

For Apollo, NASA and its contractors built a ''man-machine'' system that combined the power of a computer and its software with the reliability and judgment of a human pilot. Keeping the astronauts ''in the loop,'' overtly and visibly in command with their hands on a stick, was no simple matter of machismo and professional dignity (though it was that too). It was a well-articulated technical philosophy. It was also necessary to achieve the political goals of the space program and show that the classical American hero—skilled, courageous, self-reliant—had a role to play in a world increasingly dominated by impersonal technological systems (especially in contrast to the supposedly over-automated Soviet enemy).

That technical philosophy reflected policy making at the highest levels. When NASA administrator James Webb argued for the project, he cautioned that the decision ''can and should not be made purely on the basis of technical matters,'' but rather on the ''social objectives'' of putting people into space. He and Secretary of Defense Robert McNamara argued that, ''it is man, not merely machines, in space that captures the imagination of the world.''4 Presidential science advisor Jerome Wiesner famously opposed a manned lunar program because its scientific goals did not justify the cost. The debates leading up to Kennedy's decision distinguished between ''exploration,'' which is manned, and ''science,'' which has higher intellectual prestige value but is best conducted remotely.5

Yet the grammar of President Kennedy's 1961 call to action contained an ambiguity. ''Achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth,'' made the astronaut a passive participant.6 Indeed, NASA made an early, radical decision to use a digital computer, a ''thinking machine,'' in the Apollo capsule that would control much of the flight. The computer design and its software then reflected a philosophy of automating the fights while not actually replacing the astronauts.

In the end, the astronauts ''flew'' a very small part of the total mission by themselves, but their control included critical moments of the lunar landing (as well as rendezvous and docking)—landing having long been the ultimate expression of a pilot's skill. Even then, the astronauts controlled the lander indirectly: unless in an emergency mode, their sticks actually commanded a software program, which then controlled the vehicle. Software, a concept barely understood at the start of Apollo, became critical during its development. The programs had the ability to bring the LM right down to the lunar surface under automatic control. They could also crash and kill the astronauts if they went wrong.

Despite the automation, on each of the six Apollo landings the astronaut in command took control and landed in a manual mode. This book explores why.

Chapter 2 begins by examining the anxieties surrounding the role of aircraft pilots in the 1950s. Professional test pilots debated human-machine interactions in the years just before human spaceflight as a host of new technologies—from electronic flight controls to computers in the cockpit—both mediated their control of the machine and gave them access to new realms. When the shock of Sputnik launched the space age in 1957, pilots pondered their potential role in this new era. The X-15 rocket-plane, the subject of chapter 3, sought to prove that human skill and judgment would be required for at least one phase of spaceflight: reentry from space back into the atmosphere. Pilots mastered reentry with the help of computers that augmented their skills and stabilized their flight.

In the wake of the Sputnik scare, NASA was created out of the National Advisory Committee on Aeronautics ( NACA) and a variety of federal research groups, and chapter 4 follows pilots into the space age. X-15 test pilots like Neil Armstrong proclaimed that human operators could manually fly the huge new rockets directly off the launch pad and on toward the moon. The powerful Wernher von Braun had an alternative vision, of rockets as automata, carrying passive human cargo. His idea would overrule the astronauts' desire to fly off the pad.

Yet pilots had new powers of their own. The Project Mercury astronauts sparked intense public interest in human spaceflight and immediately pressed for their vision of professional identity, heroism, and control. Arguments over ''spam in a can'' and the amount of control appropriate for the human cargo ran throughout the Mercury project. Engineers working on the project, who would go on to form the core of the Apollo team, had long experience studying human-machine interactions in aircraft. They held pilots in high regard, relished a close collaboration, and spent years flying and testing dangerous machines. Project Mercury's successor, Project Gemini, epitomized the pilot-centered approach, enabling hands-on control of orbital maneuvers. The complexity of rendezvous operations, however, also called for computational aids, from paper charts to digital computers.

The Apollo program began with the new Kennedy administration and its recognition of the public, political impact of human spaceflight. Kennedy's speech launching the moon program came just weeks after the suborbital flight of Alan Shepard, who was hailed as a space-age Charles Lindbergh. Yet the first contract of the new moon program was let not for rocket engines or fuel tanks or launch pads, but for a computer, the subject of chapter 5. Engineers at MIT's Instrumentation Laboratory, who would build that computer, in the 1930s had helped change the nature of flight from ''seat of the pants'' intuition to numerical, instrument-based tasks. Their Apollo proposal derived from a Mars probe, designed but never built, and from the inertial guidance system for the Polaris nuclear missile. The MIT engineers valued accuracy and autonomy and studied how a set of gyroscopes could find its way to the moon and back.

But the Apollo system had a human user, someone who would require an ''interface'' to issue commands and requests to the computer and read out information. This requirement raised a series of difficult, interesting problems. The machine would have to be much more reliable for the two-week lunar missions than for a missile's short flight. It would interact with two planetary bodies instead of one, and two spacecraft instead of one. It would need to be calibrated against the stars by a human user. And if it failed, people might die. Chapter 6 follows the Apollo computer as it became operational hardware and recounts its designers' decisions about human interface, reliability, and manufacturing.

Exotic as it seemed, the hardware adapted for Apollo was relatively familiar in the world of military avionics. Radically new, however, was the software that would interact with the astronauts to control the mission, the subject of chapter 7. At first, programming was treated as a secondary, almost trivial task, but by 1966, it seemed the early Apollo flights might be delayed for lack of available computer programs. Only the 1967 Apollo 1 fire that killed three astronauts and NASA's management intervention into the programming team brought the software project under control and on schedule. Early, unmanned Apollo flights revealed the delicate mix of reliability, flexibility, and accountability that would surround these new, software-controlled systems.

The entire Apollo program culminated in the landing. The final ten or so minutes before touchdown formed the most critical period of the mission. The remainder of the book examines the design and execution of the lunar landings. Chapter 8 describes the plans for this phase of the flight, incorporating fundamental physics, lunar models, computers, human performance, and a host of uncertainties, including questions about the human role. From 50,000 feet down, the LM made the transition from purely inertial guidance to include radar and the human eye. To allow the astronauts time to visually assess their landing site, the maneuver's design had to incorporate detailed consideration of human capabilities. Automatic systems would fly the LM down to an altitude of a few hundred feet, where the commander could take over semiautomatic control and bring the LM down with his hands on a stick.

The final chapters go through each of the landings and the interactions between the astronauts and their machinery, and with their colleagues on the ground. The minute details afforded by transcripts and data telemetry allow a kind of real-time ethnography, a thick description of human-machine interactions and their cultural context during critical operations.

Each of the landings stood out in some dimension. Chapter 9 dissects Apollo 11 and the famous ''Program Alarm'' that began this chapter to examine risk, responsibility, and error in the distributed software-based system. Chapter 10 looks at the remaining landings. As they progressed, the technical task lost some of its challenge and uncertainty, while the scientific goals of the program took greater prominence—hence the later missions landed in geologically more interesting, but tactically more difficult, areas.

The final chapter of the book extends the analysis to the broader history of human spaceflight in America and follows some threads from the Apollo story into today's world. Human-machine relationships in Apollo had significant implications for the space shuttle, and hence for decades of American space policy. Reframing the ''humans versus robots'' debate into one that is richer and more forthright about both human and remote presence and their social implications is crucial for U.S. space policy as it faces the space shuttle's retirement and a possible return to the moon or human venture to Mars.

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