The issue of “field conditions” is significant because the CBM is Primary Structure with respect to containing pressure in a high vacuum environment. Like a “factory joint”, the elastomeric seals of a “field joint” are susceptible to issues of long term compression set and to local concentrations of stress. Unlike a factory joint, a field joint in the LEO environment is subjected to several adverse circumstances at the time of compression. These include distortions caused by “ballooning” of the two mating Elements due to internal pressure1, changes in the behavior of the components due to temperatures2, distortions due to temperature differences across the mating interface3, nearby floating particles (both ambient on-orbit and those sourced to the enclosed launch environment itself )4, and exposure to Atomic Oxygen5.
Footnotes- Which turns an ostensibly static seal into a dynamic seal when pressure is introduced into the vestibule. See Parker O-Ring Handbook (ORD5700), Parker Hannifin Corporation, Cleveland, OH (2007), Section 5.[↩]
- Parker, op. cit. Section 2.13.2. [↩]
- Also threatening service as a dynamic seal.[↩]
- Parker, op. cit. Section 3.2. [↩]
- For additional fundamental insight, see Fortescue, P. and John Stark [Ed.] “Spacecraft Systems Engineering” (John Wiley & Sons, 1991), section 2.3.[↩]