02 May 2001
Environmental Impact from Munitions 17
t
Richard Wild
Diehl Munitionssysteme GmbH & Co. KG Werk Maasberg
Abstract
Military history knows many catastrophic losses caused by munition.
Worldwide efforts are made to reduce the vulnerability of munitions and to develop
„Insensitive Munitions“ (IM).
IM fulfill their performance requirements, while minimizing the violence of their response to unplanned stimuli, such as heat, shock and impact.
IM objectives, tests and guidelines are established in the MIL-STD 2105 and in the STANAG 4439.
IM exceeds the actual safety levels and offers more safety - in production (example: initiation threshold), - in storage (example: Sympathetic Reaction), - in transportation (example: Liquid Fuel Fire) and - in use (example: Bullet Impact).
The safety of munition rapidly increased the last 10 years.
While traditional munition in a fire causes mass detonation, Insensitive Munitions even stimulated by a detonation will only burn:
IM saves lifes and materials.
Introduction
Military history knows many catastrophic losses caused by munition.
Serious accidents with munitions on weapon platforms, in stores, or on transport carriers made evident the vulnerability of conventional munition and caused global efforts to reduce the vulnerability, developing so called „Insensitive Munitions“.
In most cases not the munition itself is the reason for the accidents but fires, which spread to the munition and lead to mass detonations.
The safety policy of the US-Navy, derived from accidents like these on ships, found worldwide interest and in the meantime an IM policy is also formulated in STANAG 4439.
What means Insensitive Munitions (IM) ?
Definitions of IM are included in MIL-STD 2105 and STANAG 4439:
123 P. Castelo Branco et al. (eds.),
Defense Industries: Science and Technology Related to Security, 123–126.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
Insensitive Munitions reliably fulfill their performance, readiness and operational requirements on demand, and minimise the probability of inadvertent initiation and severity of subsequent collateral damage to weapon platforms, logistic systems and personnel when subjected to unplanned stimuli.
In short: IM fulfill the performance requirements at considerably lower vulnerability.
When is Munition insensitive ?
STANAG 4439 lists 6 different threats (stimuli), munition will face during its life cycle:
-Open fire and fire in an adjacent room -Impact by bullet and fragment attack -Shaped charge jet attack and -Sympathetic Detonation.
For every threat a munition test procedure is specified.
Munition is considered as insensitive, when
- the response of fire and impact stimuli is a type V (burning) reaction, (STANAG:
for Slow Heating type IV is allowed)
- the response of Sympathetic Reaction is not type I, (STANAG: is not type I and type II),
- the response of a Shaped Charge Jet Impact: no type I reaction (only specified in the MIL-STD).
Insensitive Munitions Technology
IM requirements usually cannot be fulfilled with yesterdays welltried methods, such as traditional TNT or wax bonded explosives.
Basis for IM nowadays are less sensitive PBXs and since some years we use a new generation of pressable PBXs developed by Diehl-MS.
To take advantage of the whole insensitivity potential of these explosives, the manufacturing processes are adjusted to the lower sensitivity.
In case of need the insensitivity of the munition is then guaranteed by a specific IM design of the warhead and the complete munition, together with the packing.
Only the add up of all these steps results in an „Insensitive Munition“.
Safety effects caused by Insensitive Munitions
All the IM tests, specified in the standards, simulate threats which are most likely to occur during military operations.
Slow and Fast Heating, as well as Sympathetic Detonation can be considered equally applicable for production, storage and transportation of ammunition during peacetime.
Insensitive Munitions offer more safety in production
The higher safety levels of Insensitive Munitions with PBX affect already the production of warheads.
In the different steps of the processes, explosive powders and unconfined pressed or casted charges have to be handled. Here e.g. improved impact and friction sensitivities, as well as higher initiation thresholds help to achieve better process safety.
Moulding powders which were for sale 10 years ago, with 95% HMX and wax or plastic binders had an impact sensitivity of 10J or less. Better coated materials, used today have impact sensitivities of 30J and higher.
The following example of the shockwave sensitivity of pressed PBX-charges with 96% HMX, shows the rapid ascent in the development of less shock-sensitive energetic materials:
more than 5 years ago: 20 kbar initiation pressure, 3 years ago: 28 kbar initiation pressure, last year: 40 kbar initiation pressure.
Insensitive Munitions offer more safety in storage
The actual advantages Insensitive Munitions have, of course are more safety in storage and transportation.
The Sympathetic Reaction test shows the response of a detonating munition on adjacent warheads as they are packed up in a store or vehicle.
For IM the Sympathetic Reaction test has to make sure, that a warhead detonation will not propagate this detonation to the acceptor warheads.
Test setup of the example:
The donor of a cure cast filled missile warhead is ignited with its own initiation train.
Lilac acceptor without any barrier to the donor.
Yellow acceptor, separated by the original storage packaging (PU-foam between GF- resin).
The witness plates, the warheads were standing on, and the WH parts found after he test, show a full detonation of the donor, a burning reaction of the yellow acceptor and no reaction traces of the lilac warhead.
So for this weapon a detonation of one warhead in a store will not lead to a mass detonation of the stored munition.
Insensitive Munitions offer more safety in transportation
The Liquid Fuel Fire test simulates the fast heating conditions of an open fire engulfing the munition in a flame envelope. For IM no reaction more severe than typeV shall occur.
In the Fuel Fire test of a highly confined warhead (more than 15 mm wall thickness of the steel case), filled with a pressed PBX (92% RDX), the explosive had burnt out, while the metal case is only damaged in the thread.
So for this weapon a fire on a munition truck will not cause reactions more severe than burning of the PBX filling of the transported warheads.
Insensitive Munitions offer more safety in use
Bullet Impact is one of the most probable threats, that may happen during military operations. For IM no reaction more severe than typeV shall occur.
For a cure cast filled missile warhead the response of the impact of a 12,7 mm AP projectile is a hole in the case, where the PBX slowly burnt out .
So for this weapon the impact of an armor-piercing projectile will only lead to a burning of the explosive filling of the warhead.
Safety improvements by Insensitive Munition
While conventional munition in a fire leads to more and more violent reactions up to mass detonation, fire and impact of IM will cause only burning of the munition.
Even a detonation with IM leads from a type III response, or in my example from the detonation direct to burning.
From every possible reaction level Insensitive Munition always leads to a burning reaction.
Conclusions
Accidents with conventional munition in the past caused many catastrophic losses.
The safety of munition has rapidly increased. Traditional explosives like TNT have been almost completely replaced by less sensitive plastic bonded explosives.
IM is less vulnerable to fire, impact or detonation propagation and guarantees more safety in production, storage, transport and use of munition.
IM hightens the survivability of combat platforms and fighting personnel.
Exceeding actual safety levels, IM saves lifes and materials.
Dr Adam S Cumming
A requirement has developed for new energetic materials which can provide the necessary performance while meeting the insensitivity and environmental requirements now in force. This poses a significant challenge to the munition designer; one that cannot be easily met using existing technology. New materials and new ways of working can provide an answer to the need, and research in the UK has matched that in progress elsewhere in addressing the issues, though from a UK perspective.
This paper will describe the issues from a UK perspective and illustrate how the available technology has been harnessed to begin to meet the developing needs. It has required a systems approach using technology such as steel strip laminate motors for rockets;
combustible cases; as well as new compositions, both using inert rubbery binders and exploring the strengths and limitations of energetic binders. New solids are also being explored; as are clean manufacturing and disposal techniques, and these are described. While there has been some progress, much remains to be done, and priorities need to be assigned.
These are discussed.
127 P. Castelo Branco et al. (eds.),
Defense Industries: Science and Technology Related to Security, 127–140.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
© Dstl 2001 10 September 2004
Dstl is part of the Ministry of Defence