1.5.3 Hazards To Ordnance (HERO)
HERO results because many modern munitions incorporate electrically initiated firing circuits or detonators. Under abnormal circumstances, sufficiently strong RF electromagnetic fields may induce electrical currents or voltages within these circuits. If the induced energy were large enough to activate the initiation mechanism, there would be a risk of unintended functioning of the explosive device. Although such events are extremely unlikely in properly managed environments, the potential consequences are sufficiently serious that HERO has long been recognized as a distinct category of RF radiation hazard.
The susceptibility of an item of ordnance depends on many factors, including the design of its firing circuitry, the operating frequency and field strength of the RF source, the orientation of the munition with respect to the electromagnetic field, and the way in which cables, wiring, or conductive components couple to the incident energy. Modern munitions are therefore designed with extensive electromagnetic protection measures intended to minimize their susceptibility to external RF fields. These measures may include shielding, filtering, careful circuit design, and the incorporation of safety features that reduce the likelihood of inadvertent initiation.
Despite these engineering safeguards, strict operational procedures continue to be employed wherever explosive ordnance is manufactured, transported, stored, maintained, or handled. Restrictions may be placed on the operation of RF transmitters in the vicinity of ammunition storage facilities, loading areas, weapons preparation facilities, and military platforms carrying explosive stores. Where transmitting equipment must operate nearby, careful planning and electromagnetic compatibility assessments are undertaken to ensure that the resulting RF environment remains within established safety limits.
HERO considerations are encountered primarily in military environments, including naval vessels, air bases, ammunition depots, weapons testing facilities, and defense manufacturing establishments. However, similar principles may also apply to certain civilian industries that use electrically initiated explosive devices, such as mining, quarrying, demolition, seismic exploration, and some specialist industrial applications. In these situations, controls on nearby RF transmitters form part of the overall safety procedures governing explosive operations.
Although HERO represents a specialized aspect of RF radiation safety that affects relatively few people outside defense and certain industrial sectors, it illustrates an important principle that applies throughout RF engineering. RF electromagnetic fields do not interact only with the human body—they may also couple energy into electrical systems in ways that produce unintended consequences. Understanding these interactions enables engineers to design equipment and operating procedures that ensure both personnel and explosive devices remain safe under all foreseeable operating conditions.