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The Crew as a Subsystem

The following is adapted from something I got from a friend. I don't know who wrote the original or even where my friend got it (he doesn't remember). I've added notes [in brackets] where I felt there were errors or omissions (or in some cases to spell out abbreviations), and I've also added a couple of general comments at the end.

TOTALLY, COMPLETELY AND UTTERLY UNOFFICIAL. UNRELATED TO ANY PROJECT OR SPECIFIC PRODUCT.

The human beings in any manned space system must, by definition, be considered as the most important part of the system. If this were not true, why would the system be called a "manned space system"? If, for example, the TCS [Thermal Control Subsystem] were more important than the crew why would a spacecraft not be called a "thermally controlled space system"? It IS thermally controlled but that's not its main characteristic.

Many of the problems that arise when attempts are made to "put the man in the loop" are caused by the fact that the human element is [almost] never EXPLICITLY mentioned in a system-level specification. It is too often assumed that the human will be able to "fit into" a system that has been built to optimise the interaction between its non-human components. True, the human often can "fit in" and the system still works because the human is the most flexible and adaptive component. Think of the performance benefits that would accrue if the system were defined around the way this most flexible and adaptive component perceives the mission goals and the operations required to achieve them.

True, human beings are aware of themselves and so every engineer feels justified in saying "I know about the human interface because I am a human being." But without being trained in Human Factors one's knowledge of the human component is not wide enough, deep enough, or systematic enough to be compatible with the systems design [methods] employed on other components. The following is a tentative description of the crew in a way that other engineers on manned space systems use.

Subsystem level responsible "the Agency". Components supplied by "competitition".

Component Description

Data Input

visual

One-failure-tolerant interface made up of two synchronised active ports. Capable of high-bandwidth reception of EMR [electromagnetic radiation]. Complex data coding in multiple but limited formats.

auditory

One-failure-tolerant interface made up of two synchronised active ports. Capable of high-bandwidth reception of sound. Complex data coding in multiple but limited formats.

tactile Multiple-failure-tolerant interface made up of many unsynchronised active ports distributed throughout component with local variation in sensitivity. Capable of high-bandwidth reception of vibration [and EMR]. Simple data coding in a few limited formats.

olfactory

Single-failure-tolerant interface made up of two unsynchronised active ports. Capable of high-bandwidth reception of chemical compounds. Complex data coding in single (poorly documented) format.

gustatory

Zero-failure-tolerant interface made up of one active port. Capable of high-bandwidth reception of chemical compounds. Simple data coding in single format.

Data Output

vocal

Zero-failure-tolerant interface made up of one active port. Capable of high-bandwidth transmission of sound. Complex data coding in multiple formats.

gestures

Multiple-failure-tolerant interface made up of many partially synchronised active ports distributed throughout component with local variations in precision. Capable of high-bandwidth transmission of movement. Complex (according to port) data coding in multiple formats.

chemical

Multiple-failure-tolerant interface made up of many unsynchronised active ports. Capable of high-bandwidth transmission of chemicals. Complex data coding in a poorly documented format.

Materials Input

air

Double-failure-tolerant interface made up of three synchronised active ports. Interface operated automatically [or under voluntary control] but may be interrupted for short periods of time (usually up to 1 minute at maximum).

food

Zero-failure-tolerant interface made up of one active port (common with one of air ports). Interface operated under voluntary control of component.

drink

Zero-failure-tolerant interface made up of one active port (common with food port). Interface operated under voluntary control of component.

Materials Output

air

Double-failure-tolerant interface made up of three synchronised active ports (common with air input ports). Interface operated automatically [or under voluntary control] but may be interrupted for short periods of time (usually up to 1 minute at maximum).

feces

Zero-failure-tolerant interface made up of one active port. Interface operated under (hopefully [under nominal conditions]) voluntary control of component.

urine

Zero-failure-tolerant interface made up of one active port. Interface operated under (hopefully [under nominal conditions]) voluntary control of component.

sweat

Double-failure-tolerant [why double?] interface made up of many [partially] synchronised active ports. Interface operated automatically.

Subsystem objectives (and procedures to achieve them)

Intelligent control of all [other?] subsystems (using: specific knowledge of subsystems, specific knowledge of subsystems' operating domains, specific knowledge of mission goals, general knowledge about the world).

Maintenance, repair and replacement of all [other?] subsystems (using: specific knowledge of subsystems, specific knowledge about the overall condition of the system, specific knowledge of mission goals, general knowledge about the world).

Public relations maintenance (using: specific knowledge of mission-related politics, general knowledge of interpersonal skills).

Note: This strikes me as a lighthearted, tongue-in-cheek way to make a perfectly serious point. Two things are missing, though: sex-specific materials output, and a discussion of the processing that is applied to the data and materials. The former is important because technically the description is incomplete without it and because it reflects identifiable subclasses of crew components.

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Last updated 30 April 2006, to redo the visual design