For the sake of this discussion, engineered systems can be considered in two categories: those that are intended for human-interactive maintenance1, and those that are not. Those that are not so intended are of no interest here. The development of those that are intended for such maintenance must consider the ability of the maintainers to view and reach into, around, or through features of the system to execute maintenance tasks. Those abilities are dominated by human perception, by the shape of human appendages, the postures that can be obtained, and the forces that can be generated. In most cases, those must be considered in the context of tools used for the tasks. Such tools might, or might not, be specially designed for a specific task on a specific system.
These issues can dominate the use of an engineered system so thoroughly that legacy Department of Defense development practices created a standard to describe them. The standard (MIL-STD-1472) was often contractually imposed under the general topic of “Human Engineering”. More recent work collecting this type of information has been conducted by the National Institute of Standards and Technology (see NISTIR-7889).
The legacy documentation was, of course, intended for use in the 1-g environment. The relevant documentation dedicated to the zero-g environment in the CBM’s developmental period was NASA-STD-3000 “Manned Systems Integration Standard”2, which was further supported by NASA/SP-2010-3407 “Human Integration Design Handbook”. Applicability was established by S683-29902B, §3.3.7 and S683-28943E, §3.3.7.
NASA-STD-3000 addresses two special cases of on-orbit Human Integration. Human integration for tasks conducted inside the vehicle (“Intra-vehicular Activity”, or IVA) were addressed in NASA-STD-3000, Sect. 4. NASA-STD-3000, Sect. 14 dealt with similar factors outside the vehicle (“Extra-vehicular Activity”, or EVA). In particular, the latter section dealt with overcoming pressure loads when suited for EVA. The basic nature of the CBM’s transition from “external” to “internal”3 meant that the design must engage with both sets of considerations, which is a rarely encountered circumstance.
Footnotes