Control/Monitor Instrumentation for Environmental Control and Life Support Systems Aboard the Space Station

The future National Aeronautics and Space Administration (NASA) Space Station will require a high level of Control/Monitor Instrumentation (C/M I) for the operation of its critical subsystems. Automatic control and monitoring of subsystem operation will provide the crew with more time to conduct space operations for scientific experiments and commercial processes. Subsystem control and monitoring involves real-time data processing, subsystem fault tolerance and redundancy management, caution and warning, health monitoring and trend analysis, data management and support for on-orbit maintenance and repair. This paper addresses the control and monitor requirements for the Space Station’s Environmental Control and Life Support Systems (ECLSS). Sensor and actuator requirements are detailed. These are identified, along with the required controllers for the ECLSS complement of equipment. A controller hierarchy is also provided.

This paper also examines the evolutionary development of a “family” of controllers for autonomous operations at both the prototype and flight production levels. The development of these controllers has included the key design requirements of providing reliable operation while minimizing costs using:

1. 1.
   Standard family of microcomputer hardware across the range of ECLSS applications.
2. 2.
   Standard sensor signal conditioning approach that optimizes weight, volume and power and is applicable across various technologies.
3. 3.
   Actuator signal conditioning elements that can be assembled as building blocks to meet the required subsystem configuration.
4. 4.
   Structured software techniques which separate the C/M I software into an operating system and an application-specific portion.

An advantage to these developments is that any ECLSS subsystem controller can be assembled from a generic set of hardware and software, rather than using customized designs.