Computers in Spaceflight: The NASA
Experience
- - Chapter Three -
- - The Skylab Computer System
-
-
- Conclusions
-
-
- [82] The Skylab
program demonstrated that careful management of software
development, including strict control of changes, extensive and
preplanned verification, and the use of adequate development
tools, results in quality software with high reliability.
Attention to piece part quality in hardware development and the
use of redundancy resulted in reliable computers. However, it must
be stressed that part of the success of the software management
and the hardware development was due to the small size of both.
Few programmers were involved in initial program design and
writing. This meant that communications between programmers and
teams were relatively minimal. The fact that IBM produced just 10
computers and really needed to ensure the success of just 2 of
those helped in focusing the quality assurance effort expended on
the hardware.
-
- [83] What happened
after the manned Skylab program demonstrated the need for
foresight and proper attention to storage of mission-critical
materials until any possibility of their use had gone away. The
dispersal of the verification hardware is understandable, as it is
expensive to maintain. However, some provision should have been
made for retaining mission-unique capabilities such as actual
flight hardware. The destruction of the flight tapes and source
code for the software by unknown parties was inexcusable. A single
high-density disk pack could have held all relevant
material.
-
- Skylab marked the beginning of redundant
computer hardware on manned spacecraft. It was also the first
project that developed software with awareness of proper
engineering principles. The Shuttle continued both these concepts
but on a much larger and more complex scale.
