Temperature Stress and Nuclear Radiation Effects on Electromagnetic Shielding

Military specifications, such as MIL-STD-810 and similar environmental specifications for airborne electronic equipments, delineate the extremes within which such equipment must function properly. Emphasis is usually on physical parameters such as vibration, shock, heat, cold, salt-spray, and corrosive atmospheres. Limits have usually been dictated by practical considerations of terrestrial, operational, and environmental conditions. Great strides have been taken toward lunar and interplanetary exploration, but the possible effects of known adverse environments upon the electromagnetic shielding effectiveness of electronic equipment enclosures are relatively unknown. Prior to conducting this study, opinions were solicited as to whether physical environments would affect the electromagnetic shielding characteristics of metal equipment enclosures. The consensus of educated guesses was that there would be no effect on electrical characteristics of the enclosures, provided of course that no physical damage accrued to the enclosures. The authors are not aware of any literature which purports to be a study or record of the effects of such environmental extremes upon the electromagnetic shielding effectiveness of electronic equipment enclosures. The effects of repeated temperature shock and of exposure to nuclear radiation on the shielding effectiveness S of enclosures fabricated from several common metals, incorporating several types of seam construction, are explored. This investigation results from a Boeing-sponsored companion study to work performed for the U. S. Army Electronics Command. It in no way purports to supply all the answers, but is presented in the hope that it may arouse sufficient interest so that unresolved questions will be thoroughly investigated.