Insensitive Munitions (IM) is a relatively new term used in the international ordnance community. What does it mean? Where does the term come from? Is it realistic to think that we can make effective munitions that are “insensitive”? Some people have said that the term “Insensitive Munitions” is an oxymoron. Is it really a contradiction of terms? The answer is simple; it is not.
Munitions should react only when we want and should not be so sensitive that they react violently by accident or by enemy action. In the past, all Navy munitions were designed to be safe to handle, transport, store, and use under realistic operational conditions. Today, we can produce munitions that have these characteristics and, in addition, are insensitive to the stimuli like heat, shock, bullet, and fragment impacts often encountered during operational use. Also, these insensitive munitions can reduce the probability of sympathetic detonation when a nearby munition reacts violently.
The dictionary1 defines munitions as: “materials used in war such as guns, ammunition, and bombs”. Insensitive, on the other hand, is defined as: “having little or no power to feel or notice”. What then is an insensitive munition? It is material used in war having little or no power to feel or notice stimuli that could cause an unplanned explosive event.
There are ample historical data that demonstrate the disastrous effects of unintentional initiation of the explosive materials used by the military. In the following text, I will review some of the catastrophic events that happened during and after the war in Vietnam and the explosives technology developed to solve the problems uncovered following these mishaps. Finally, I will discuss why I believe that we can, and should, make cost-effective “Insensitive Munitions”, available to our Forces.
To make the concept of Insensitive Munitions even more appealing, modern weapon guidance technology allows us to consider using insensitive explosives2 that may be less powerful than the explosive formulations used in World War II, Korea and Vietnam. These new explosives are considerably less sensitive to mechanical, electrical, or thermal stimuli than the compositions that they are intended to replace. Because weapons can now be delivered with great accuracy, the on-target performance of guided weapons loaded with these new explosives is substantially greater than that of the older weapons.
Consider, for example, the “Paveway” laser-guided bomb system. The PAVEWAY bomb was one of the first “smart weapons”. It was developed in the late 1960’s for use in the Vietnam War. Mk-80 series General Purpose bombs were modified by attaching a “Paveway” guidance package. These weapons, in a single sortie with one aircraft, destroyed targets that had previously required multiple aircraft sorties and many bombs for their destruction.
GBU-16B PAVEWAY II laser-guided bombs on the aircraft carried USS JOHN F. KENNEDY during operation “Desert Storm”. U.S. Navy photo.
In “Operation Desert Storm”, laser-guided bombs accounted for only about 5% of the total ordnance expended against Iraq but accounted for nearly 50% of the targets destroyed3. The above is a picture of PAVEWAY bombs being readied for use during Operation Desert Storm. These bombs were loaded either with an RDX, TNT4, and aluminum powder or with a TNT and aluminum formulation. Both of these explosives react violently in fuel fires and are vulnerable to sympathetic detonations in storage areas and are being replaced.
The guided weapons available today have improved accuracy and reliability. Use of new insensitive explosive compositions rather than the more sensitive World War II explosive formulations would have no measurable adverse effect on the on-target performance of the new guided weapons.
1Barnhart, Clarence L., The World Book Dictionary, Field Enterprise Educational Corporation, Chicago, IL, 1971 Edition.
2An “Insensitive Explosive” is one that, in thermal, mechanical, or electrical stimuli tests, has been shown to be substantially harder to initiate to detonation than conventional military explosives like TNT, Composition A-3, Composition B, etc.
3Texas Instruments, Inc. advertisement, Aviation Week & Space Technology, 6 December 1993
4RDX is 1,3,5-trinitro-1,3,5-triazacyclo-heptane and TNT is trinitrotoluene.