What feature of the FMU-139/B fuze enhances its effectiveness against hardened targets?

The FMU-139/B fuze is specifically designed with penetration capabilities that enhance its effectiveness against hardened targets. This feature allows the fuze to ensure that the ordnance can penetrate through the protective layers of a target, such as reinforced concrete or other fortified structures, before detonation occurs. By enabling more effective breaching, the fuze increases the likelihood of achieving significant damage to the target upon impact.

The emphasis on penetration is particularly important in military operations where adversaries may employ hardened facilities. The ability to penetrate these defenses maximizes the efficacy of the ordnance, ensuring that it reaches its intended target deep within the structure.

The other options, while significant in various contexts, do not directly address the specific requirement of engaging hardened targets as effectively as penetration capabilities do. For instance, high-speed impact can enhance the effectiveness of an explosive, but without penetration, it may not be sufficient against particularly tough targets. Proximity detection is useful for airburst munitions but is less relevant when direct impact on hardened surfaces is necessary. Weight distribution can affect the flight characteristics of a munition, but it does not play a pivotal role in ensuring penetration against hardened targets. Thus, penetration capabilities are a crucial feature of the FMU-139/B fuze