The closeness of IBM to Johnson Space Center also facilitated the ability of NASA to manage the project. When IBM won the Shuttle contract, it simply increased its local force. IBM had a building and several hundred personnel near Johnson because of its Mission Control Center contracts. One of the lessons learned from monitoring Draper Laboratory in the Apollo era was that by having the software development at a remote site (like Cambridge), the synergism of informally exchanged ideas is lost sometimes it took 3 to 4 weeks for new concepts to filter over 85. Lastly, Christopher Kraft of Johnson Space Center and George Low of NASA Headquarters, both highly influential in the manned spacecraft program during the early 1970's, felt that Johnson had the software management expertise to handle the contract directly 84. Personnel experienced with a specific software system are the best people to maintain it. There is a considerable difference between changing maintenance mechanics on an existing hardware system and changing software companies on a not yet perfect system because to date the relationships between components in software are much harder to define than those in hardware. By keeping the software contract separate, NASA could develop the code on a continuing basis. In late 1983, Lockheed Corporation, not Rockwell, won the competition for the operations contract. As time went on, Rockwell's responsibilities as prime hardware contractor were phased out, and the shuttles were turned over to an operations group. Moreover, during the operations phase, software underwent the most changes, the hardware being essentially fixed 83. Its importance to the overall program alone justified a separate contract, since it made the contractor directly accountable to NASA. Thus software is in many ways the most critical component of the Shuttle, as it ties the other components together. Since software does not weigh anything in and of itself, it is used to overcome hardware problems that would require extra systems and components (such as a mechanical control system) 82. There are several reasons why this division of labor occurred. As a result, Rockwell still subcontracted with IBM for the computers, but IBM hand a separate software contract monitored closely by the Spacecraft Software Division of the Johnson Space Center. But to Rockwell's dismay, NASA decided to separate the software contract from the orbiter contract. Rockwell bid on the entire aerospacecraft, intending to subcontract the computer hardware and software to IBM. IBM and Rockwell International had worked together during the period of competition for the orbiter contract 81. NASA awarded IBM Corporation the first independent Shuttle software contract on March 10, 1973. NASA separated the software contract from the hardware contract, closely managed the contractors and their methods, chose a high-level language, and maintained conceptual integrity. ![]() Even so, NASA lessened the difficulties by making several early decisions that were crucial for the program's success. As a result, about $200 million was spent on software, as opposed to an initial estimate of $20 million. NASA and its contractors made over 2,000 requirements changes between 1975 and the first flight in 1981 80. Besides these realities, no one could foresee the final form that the software for this pioneering vehicle would take, even after years of development work had elapsed, since there continued to be both minor and major changes. It also increased the complexity of a spacecraft already made complex by flight requirements and redundancy. This increased the size of the task because of the communication necessary between the working groups. Even though NASA engineers estimated the size of the flight software to be smaller than that on Apollo, the ubiquitous functions of the Shuttle computers meant that no one group of engineers and no one company could do the software on its own. It was obvious from the very beginning that developing the Shuttle's software would be a complicated job. Chapter Four - Computers in the Space Shuttle Avionics System - Developing software for the space shuttle During 19 the first requirements began to be specified for what has become one of the most interesting software systems ever designed. Computers in Spaceflight: The NASAExperience
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