Chapter 7: Man and machine
Theme: This chapter describes the astronaut’s job, attempting to indicate the significance of his role in relation to the spacecraft’s automatic control systems.
What can a man do? The Mercury spacecraft was designed to be as much like an ICBM nose cone as possible. Our ICBMs span continents and land with precision within a few miles of their target, all automatically, without any help from a pilot. Certainly Mercury could do the same. In fact, it would have to do so on early test flights before the management would have enough confidence in the system to let a man fly in it. If all this could be accomplished automatically, what was there for the man to do, other than to sit back and enjoy this roller coaster ride?
There was plenty to do, the astronauts claimed. What if one of the automatic systems failed? It might be all right to miss hitting the target city if there was another ICBM on its way. But an astronaut in the Mercury vehicle had only one chance. If the system didn’t work, it would be of little comfort to him that there were other Mercury spacecraft ready for future flights. What if the retro rockets were not fired on time, or it the spacecraft were in the wrong attitude? Could the astronaut do nothing but just sit there and let these things go wrong? Certainly not. He should be provided with a complete set of controls that would allow him to do all these critical functions by a completely separate means. If the automatic system failed, he should have a second chance. In this way the astronaut could greatly increase the reliability of the Mercury flights.
This concept was reflected throughout the design of the spacecraft. The automatic systems functioned through electrical circuits, but in case they should fail, the man was provided with duplicate circuits, or better yet, simple mechanical levers which required no electricity. His brain was a far more complex and effective computer than any that could have been designed for use in the Mercury vehicle. Moreover, by using his muscle power through mechanical levers, he was a source of power for the spacecraft that was independent of its batteries and could not be put out of action by a short. Thus, one of the major contributions of the astronaut to the flight was to increase the total reliability of the system. The actual space flights which were to come would demonstrate the soundness of this design concept, and the importance of the role that man can play in any complex system, particularly one on which human life depends.
But in addition to this, man has another very significant, if perhaps more subtle, role to play in space flight. The flight which the Mercury spacecraft can carry out automatically is very limited and stereotyped. No basic changes in the mission can be made without human intervention. It is only with the astronaut on board that the attitude of the vehicle can be varied to suit the special requirements that may arise on any flight. A mute automaton, the unmanned spacecraft is blind to the unexpected, deaf to novelty. It can make only those measurements which have been thought of before the launch. But with an astronaut on board, the flight plan can be changed at any time. The man can note and bring back reports of unexpected sightings which might never be discovered through automatic systems. Thus the astronaut provides the flexibility to adjust to the unexpected. Reliability and flexibility -- these are the key elements provided by man in, or out of, this automated world.