Display and Keyboard

''How do you take a pilot, put him in a space ship, and have him talk to a computer?'' astronaut David Scott succinctly put the question facing the IL. Nevins and his team embodied their philosophy in the interface to the Apollo computer. They developed a ''display and keyboard'' unit, abbreviated DSKY (pronounced ''dis-key''). Somewhat akin to an early calculator display, the DSKY had a numeric keyboard with plus and minus keys, and seven additional function keys like ENTER, CLEAR, and KEY RELEASE (figure 7.8). The display included three signed numbers for numerical data like navigation coordinates, and three shorter numbers to identify functions. Each line of display was merely five numerals, with plus or minus but no decimal point (similar to how a slide rule displayed its results). Astronauts needed to know independently, for example, that time would be displayed in three digits of seconds with two digits of hundredths, while gyro angles would be displayed in two digits of degrees plus three digits of thousandths. A series of warning and indicator lights (including the feared GIMBAL LOCK)

Figure 7.8

DSKY—display and keyboard unit—for the Apollo guidance computer. Note the space for digital displays on the right, with program, verb, and noun indicators, and three line numerical display below. Also note status lights on left, including warnings for gimbal lock, program alarm, and operator error. (Raytheon photo CN-4-268.)

Figure 7.8

DSKY—display and keyboard unit—for the Apollo guidance computer. Note the space for digital displays on the right, with program, verb, and noun indicators, and three line numerical display below. Also note status lights on left, including warnings for gimbal lock, program alarm, and operator error. (Raytheon photo CN-4-268.)

signaled anomalies or faults. The displays used the ''seven segment'' format for alphanumeric data. While the style did not originate with Apollo, its use in the AGC foreshadowed the ubiquitous LED displays of the 1970s and helped make the boxy digits icons of the digital era. In the computer, a routine called PINBALL GAME BUTTONS AND LIGHTS ran the DSKY interface (see cover image).

Alonso began thinking about the command protocol: ''It occurred to me that the sort of dialog between astronaut and AGC could fit into a rudimentary sentence structure, such as 'Display IMU Angles,' or 'Display Time,' or 'Fire Rocket' or 'Align IMU.''' Working with Albert Hopkins and Herb Thaler, Alonso developed a temporary design they could use for testing and demonstration while waiting for an official solution. Their stopgap became permanent.59

Astronauts entered data and commanded the DSKY with this ''verb-noun'' syntax. To enter a command, the astronaut would press the VERB button followed by a two-digit code for a command. Then he would push NOUN and the code for a particular type of data, and then ENTER. Noun 37, for example, referred to roll, pitch, and yaw data and Noun 89 referred to the coordinates of a particular landmark. The verb and noun codes appear on the display as they are entered. If the command requires further data to be entered, the verb-noun display will flash, as the program awaits further data entry on the keypad. It displays data in one of the five-digit numerical display lines. Each data number is then followed by depressing ENTER. Various illegal combinations of keys are rejected by the DSKY as invalid data. If an incorrect key is pressed, the CLEAR button allows the data to be reentered. The interface was a bit cumbersome and not simple. A task like aligning the inertial platform would require anywhere from thirty to one hundred-thirty keystrokes; an entire flight to the moon would take more than ten thousand keystrokes.

Certain verbs simply displayed data. Verb 01, for example, would display a selected value on the display, and Verb 11 would ''monitor'' that value, that is, update the display once per second. Other verbs ran specific guidance programs, such as Verb 41 for ''Coarse align IMU,'' or Verb 46 for ''Activate digital autopilot.'' To some degree, the astronauts could customize the displays for their own preferences, instructing the DSKY to display particular variables on particular lines. Any verb-noun combination, or any mix of DSKY keystrokes could also be entered from the ground, via the radio telemetry link (although the astronauts had a switch that could lock out remote control). The ground controllers would frequently update the ''state vector,'' or the onboard computer's knowledge of its position and velocity, through the telemetry channel.60 One of the ground controllers even had a DSKY display on his console and could push the buttons directly to command the onboard computer. Thus any DSKY command could be entered by the astronauts or from the ground.

While the astronauts could command the computer through the DSKY, the computer could also command them. Occasionally the display would flash a command, asking them to perform a certain item in a checklist.

As an example, Verb 37, ''Change major mode,'' selected a variety of operating programs, depending on particular phases of flight. By pressing VERB and then ''37'' and then ENTER, the display would flash, after which the astronaut would enter a program number for a particular phase of flight. Program ''00'' (pronounced ''poo'') was the idling state for the computer. Additionally, programs starting with 0 related to preflight checkouts (e.g., P01 = ''pre-launch initialization''), programs beginning with 1 performed boost monitoring (e.g., P11 = ''earth orbit insertion monitor''), and the 2-series included ''rendezvous navigation.'' In the command module, programs beginning with 6 specified reentry, whereas in the LM the 60-series programs controlled lunar landing. As we shall see in the next chapter, beginning with P63, ''Braking phase,''

the LM computer cycled automatically through a series of programs until the astronauts would enter P68, for ''landing confirmation.''

IL staff remember having a difficult time getting their management and NASA to accept the verb-noun structure. ''It's not serious enough,'' they recall hearing, along with the objections, ''It's not military enough. It's not scientific enough.''61 Among the astronauts Nevins found two reactions: ''One reaction is that we don't fly spacecraft through DSKYs, we don't fly planes through DSKYs.'' As for the other reaction, he said, ''they appreciated immediately what they were looking at and that they had all this capability and power. That everything and anything that was dynamic in the spacecraft was under the control of the computer. And so those people appreciated it.''

Nevins remembers having more difficulty with the earlier, Mercury astronauts. ''And then we got our spies,'' people like David Scott who worked with Battin on guidance and received a master's degree in 1962;Charlie Duke, who received a master's degree in 1964 for studying human performance during Apollo navigation;or Ed Mitchell, Ph.D. 1964, who studied interplanetary guidance. These men learned how to think about guidance and control in the MIT way. ''They all got brainwashed,'' as Nevins put it.62

Astronauts generally had good things to say about the DSKY on their missions, the result of long hours of training. Hoag recalled that ''an early reticence by the crew members was in time replaced by enthusiasm and confidence in their ability to use the computer to manage many aspects of their mission.''63 Scott added sardonically, ''It was so simple and straightforward that even pilots could learn how to use it.''64 Certain operations generated their own Apollo jargon, as when an astronaut aligned the inertial platform. The computer would display ''residuals,'' or an indication of the quality of the alignment, in degrees. A display of ''00000'' indicated no difference, a perfect alignment, which the astronauts greeted with an exclamation of ''five balls,'' a clear statement of success in the masculine culture.

Nevins's group put together a series of simulations, from simple jigs to evaluate sextant pointing to mockups to verify users' reach to the controls, to a full AGC interface in the Johnsville centrifuge. They also installed their systems' components in NASA's CSM and LM simulators.65

One day NASA headquarters called to inform Nevins that a formal complaint had been levied by the astronauts against the IL because the DSKY interface was too complex for a safe trip to the moon. Nevins responded by putting together a demonstration unit, called the space navigator, that would enable a user to ''navigate'' the earth as though it were a spaceship on its way to the moon, using ''a physical marriage of the man, a complete G&N system, a real stellar environment, and a pseudo space craft motion generator.'' Adding some old radar-tracking hardware to swivel the simulator, the IL mounted it on the roof of their building as a demonstration and training device.

Nevins put together a three-hour training program for NASA managers, including Robert Mueller, Robert Seamans, and Chris Kraft, to teach the basics of the Apollo guidance, navigation, and control and train the astronauts. ''They came to the conclusion,'' Nevins recalled, ''that it's very complex, it's expensive to train—time and everything else—but it's doable.''66 A photo of Doc Draper in the machine with the Boston skyline and stars in the background became a popular image of the lab's participation in Apollo.

At MIT Scott had studied the statistical interpretation of celestial fixes for interplanetary navigation. When he became an astronaut he was assigned to monitor the MIT contract for the astronaut office. ''I spent many nights up on a roof in Cambridge looking at the stars and working with a sextant, telescope and computer,'' Scott recalled. Some of his colleagues, he said, never got used to the keypunching, and requested programs that would combine the keystrokes into larger functions. Yet for Nevins, the turning point came when he observed Jim Lovell, Frank Borman, and Jim McDivitt operating the guidance system in a command module simulator at Kennedy Space Center shortly before their selection for the Apollo 8 mission. Lovell had mastered it, and was making it sing. ''The system wasn't flying him,'' Nevins observed. ''He was flying the system. And wow, he's flying.''67

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