It consists of approximately 420,000 lines of source code developed in HAL, an engineering language for real-time systems, and is hosted on flight computers with very limited memory.
Download shuttle sequentially software#
The PASS is safety-critical software that must be designed for quality and safety at the outset. The operating system is designed to instantaneously deselect a failed computer. Every 3 to 4 milliseconds, the four computers check with one another to assure that they are in lock step and are doing the same thing, seeing the same input, sending the same output, and so forth. To ensure high reliability and safety, IBM has designed the space shuttle computer system to have four redundant, synchronized computers, each of which is loaded with an identical version of the PASS. As indicated in the space shuttle flight log history, the backup system has never been invoked. In the event of a PASS failure, there is a backup system. In flight, all shuttle control activities-including main engine throttling, directing control jets to turn the vehicle in a different orientation, firing the engines, or providing guidance commands for landing-are performed manually or automatically with this software. The primary avionics software system (PASS) is the mission-critical on-board data processing system for NASA's space shuttle fleet. Based on a presentation by Keller (1993) at the panel's information-gathering forum, the following case study describes space shuttle flight software functionality as well as the software development process that has evolved for the space shuttle program over the past 15 years. These methodologies are necessarily dependent on the ability to manage, control, measure, and analyze the software using descriptive data collected specifically for tracking and statistical analysis. Throughout the program, the prevailing management philosophy has been that quality must be built into software by using software reliability engineering methodologies. IBM's Federal Systems Division (now Loral), which was contracted to support NASA's shuttle program by developing and maintaining the safety-critical software that controls flight activities, has gained much experience and insight in the development and safe operation of critical software. The space shuttle program, begun in the late 1970s, was designed to support exploration of Earth's atmosphere and to lead the nation back into human exploration of space. The National Aeronautics and Space Administration leads the world in research in aeronautics and space-related activities. Case Study: NASA Space Shuttle Flight Control Software
0 kommentar(er)
