Sustaining A Serviceable Explosive Ordnance Capability In The Middle East Area Of Operation

Introduction

Over the past ten years, the Australian Defence Force (ADF) has become increasingly involved in extended operations outside of Australia. These deployments mean that the environment to which deployed explosive ordnance (EO) is exposed and operated is different to that which formed the original basis of the EO’s initial lifing assessment. This had resulted in the deployed EO natures having:

• Certified environmental limits that are inadequate for current operating environments.
• Lives based on inadequate data.
• No formally certified environmental limits.

The lack of an accurately characterised operating environment, combined with a lack of item design and environmental qualification data, has the potential to compromise the safety and performance of EO deployed in operations. In order to mitigate the risk associated with a lack of objective quality evidence, Munitions Branch within the Australian Defence Materiel Organisation (DMO) has historically applied a series of conservative lifing policies to all EO deployed to the MEAO. In some instances these lifing policies have added a significant logistics and operational burden to the ADF due to:

• the need to constantly replenish EO as a result of premature depletion of stockholdings due to expiry of the MEAO life;
• Increases in transport and re-supply efforts associated with rapidly moving EO from Australia to the MEAO;
• a need to dispose of EO not consumed in operations prior to expiry of the MEAO life;
• a loss of, or limitations on, key warfighting capabilities as a result of the unavailability of key EO assets; and
• the need by the operational commander to potentially accept a reduction in EO performance as well as an increased, but un-quantified, level of risk with respect to EO safety.

Significant secondary costs are also being incurred by the Commonwealth of Australia (CoA) due to the logistics and engineering effort associated with replenishing reserve stocks in Australia, extending the Service Life of life-expired EO and certification of new EO to support existing capabilities. In some cases, EO is also being returned from the Operational Theatre under risk waivers and at significant cost to the CoA, for the purpose of testing and/or disposal.

Lifing methodology

Reference [1] outlines a five-phase lifing methodology designed to support the systematic whole-life assessment of EO. This methodology forms the basis of the lifing methodology developed for this task with the five distinct phases used for the assessments being:

• Phase One. Collecting available design, qualification and test data for all items and characterising the environment to which the items are likely to be exposed.
• Phase Two. Identifying potential life limiting failure modes for all items.
• Phase Three. Identifying life assessment techniques.
• Phase Four. Conducting trials consisting of performance and safety related tests.
• Phase Five. Using all of the evidence accumulated during the previous phases to make an assessment of the life for which the EO will remain safe and meet performance requirements.

Environments

The following environment definitions, described at [2] apply.

MEAO A1 Environment. For the purpose of this study the A1 environment seen in the MEAO is defined as an ‘Extreme Hot Dry’ desert environment where high levels of solar radiation will be experienced. Theoretically it can be expected that induced temperatures of up to 71°C could be experienced in this environment.

Australian A2 Environment. The Australian A2 environment is defined as a ‘Hot Dry’ environment typically experienced in Australia. Theoretically it can be expected that induced temperatures of up to 63°C could be experienced in this environment.

EO lifing terminology

The total life of an item of EO is made up of a number of individual lives. These lives are described and illustrated in reference [3] which states:

‘the duration of EO lives is limited primarily by the progressive ageing and consequent deterioration of the energetic material, with both safety and performance of EO tending to deteriorate with time’.

Thus, the project endeavoured to ensure logistically supportable lives were promulgated, whilst at the same time ensuring an acceptable level of safety (in storage and operation) as well as performance and reliability was maintained.

To enable the findings and recommendations of the study to be effectively implemented, for EO deployed to the MEAO environment, it was also necessary to expand on the ADF lifing definitions detailed within [3].

Service Life. The definition for Service Life is the same as that defined in reference [3]. Due to previous certification practices, this is typically the life assigned to an item of EO expected to be exposed to the Australian A2 environment.

Deployed Life. Where analysis identified one or more of an item’s critical failure modes can be accelerated or adversely affected by exposure to extreme environments, such as the MEAO A1 environment, then it was necessary to identify a Deployed Life, in addition to the Service Life. The Deployed Life has a duration that is less than or equal to the Service Life with the deployed life representing the time that the specific item of EO can be ‘Deployed’ for the purpose of Storage and Transportation, in the MEAO (that is the A1) environment. The Deployed Life comes into effect from the moment the EO enters the deployed theatre of operations and represents the time an item of EO will continue to remain serviceable in accordance with its certification basis which is detailed in its EO Design Certificate.

Tactical Life. Within the MEAO environment there are a number of sub-environments for which evidence indicates a deviation from the baseline A1 environment can be expected. These sub-environments require the promulgation of an additional life referred to as a ‘Tactical Life’. In the context of this report, the Tactical Life is a subset of the Deployed Life and only applies when the ammunition is in an end-user operational environment (that is not in Force Level logistic storage). All EO identified as being in the MEAO will be assigned a Tactical Life which is based on a particular sub-environment.

Application of EO lives

The Tactical Life for an item is assigned based on the type of environment experienced by that item and is predicated on the assumption that the Tactical Life only applies to the EO once it has left bulk ADF storage in the deployed location and has been issued to user units for either:

• local unit, field, or ready-use storage; or
• fitment to vehicles or weapons platforms, loading to weapon systems or issued to personnel.

Once issued to user units, the EO is to either be consumed within the period defined by the Tactical Life or withdrawn for disposal upon expiry of the item’s life.

In order to issue the maximum possible Tactical Life an item of EO must have sufficient Deployed Life remaining. For example, if the Deployed Life for a particular item is 24 months (two years) and the Tactical Life is six months then in order to use the full Tactical Life of six months, the total consumed Deployed Life (that is time in theatre) should be no greater than 18 months at the time of issue.

Failure modes, effects and criticality analysis

Failure mode identification and analysis

The failure modes of the items needed to be identified and the criticality of these failure modes to the life of the item in the MEAO environment had to be established. As such, a Failure Modes, Effects and Criticality Analysis (FMECA), in accordance with [4] was undertaken for each item to identify the failure mode/s which were the most critical to the life of the item in the MEAO environment.

To identify all applicable failure modes for each item, the hardware approach (described in [4]), which utilises a top down identification method, was used. In adopting this approach a failure mode identification matrix was developed which identified all the sub-systems and components which make up an All Up Round (AUR). This method ensured a disciplined approach to the identification of the many failure modes.

The general degradation mechanisms when exposed to the MEAO environmental factors needed to be clearly understood. Typically the energetic is considered to be the life limiting component of an EO system. However one of the key requirements of this study was to ensure the item of EO not only remained safe in the MEAO, but also continued to meet the capability requirement. As such it was essential to attribute just as much effort to analysing the non-energetic failure modes.

Criticality analysis

A criticality number was calculated, utilising and tailoring the qualitative criticality analysis approach of [4].

Firstly, for each identified item failure mode, the likelihood of exposure to the applicable MEAO environment causing that failure mode was assessed, with each likelihood category assigned a weighting factor.

Secondly, an operational factor and safety factor were assessed for each failure mode. Each consequence category was also assigned a weighting factor.

The criticality number was then calculated by summing the product of the likelihood of failure in the MEAO environment by the operational factor and the safety factor.

In accordance with the general principles outlined in [1], this section of the life assessment process detailed the decision logic for identifying the appropriate life assessment technique/s to be applied. This part of the process determined if testing was required for an item of EO (and if so what that testing should be) or if a robust life assessment could be undertaken using extant data.

Calculations

Mean kinetic temperature

Reference [5] defines the Mean Kinetic Temperature (MKT) as a calculated, fixed temperature that simulates the effects of temperature variations over a period of time. It expresses the cumulative thermal stress experienced by an item at varying temperatures during storage and operations.

MKT is derived from a series of temperatures and is more than just a simple numerical average, or arithmetic mean. In calculating the MKT, higher temperatures used as the basis for calculating the MKT are afforded a greater weighting, through application of appropriate activation energies. This weighting is determined by a geometric transformation which is the natural logarithm of the absolute temperature, which is described by the equation:

Where TK[K] is the MKT (degrees K), H is the activation energy (Joules), R is the gas constant (8.314 kJ/mol), Tn is the temperature (degrees K), n is the total number of (equal) time periods over which data are collected and exp is the natural log base.

Calculating the MKT. For each MEAO Tactical environment, the MKT was calculated using commercially available software. Whilst this software has some limitations it was successfully used, and validated, to rapidly process the large data set required to take into account hourly temperature variations across an entire year in the MEAO (as defined in [2]) as well as changes in the activation energy of thermally induced decomposition.

Acceleration factors

The next step in calculating a MEAO life was to determine a Service Life for the item. The Service Life is defined as the life of an item when stored in the equivalent of 25°C isothermal storage. The Service Life for an item is calculated using all available information and data for the item under assessment including in-service surveillance data as well as test data.

However using the MKT calculations on their own does not allow a suitable life, in each of the phases of deployment, to be determined. As such, it is necessary to also identify an acceleration factor for each phase, in order to ensure the kinetics are sufficiently considered when assigning a life for the item in its various operational phases. The acceleration factor for each applicable phase was calculated using the Arrhenius equation, in accordance with reference [6], which is described by the equation:

where k_t is chemical reaction rate coefficient at a given MKT and k₂₅ is the chemical reaction rate coefficient at +25°C.

Relationship between lives

When an item is deployed to the MEAO, the relationship between the design life of an item and the available Service Life, Deployed Life and Operational life which is described by the equation:

$\text{DL}>{\text{L}}_{\text{SA}}+F_1{\text{x L}}_{\text{S-MEAO}}+{\text{F}}_O{\text{x L}}_{\text{O-MEAO}}+{\text{L}}_D$ (3)

where DL is the design life for the item, L_SA is the storage and transport life used in Australia (years), L_S-MEAO is the storage and transport life used in MEAO (years), F₁ is the acceleration factor for storage conditions in MEAO, L_O-MEAO is the total operational life in MEAO (years), F₀ is the applicable operational acceleration factor (that is, F₂, F₃, or F₄) and L_D is the disposal life.

Test and evaluation program

In the majority of cases insufficient data was held by the Commonwealth to allow a robust lifing assessment to be completed. As such QinetiQ Novare developed and managed a T&E program to inform the analysis being conducted on items of EO in the MEAO.

Testing support with respect to all small arms and medium calibre natures was provided by Thales Australia and consisted of:

• accelerated ageing,
• chemical stability testing, and
• ballistic assessment via either gun firing or closed vessel analysis of propellant burn rates (depending on the calibre and nature of the item under test).

In the case of all pyrotechnic devices subject to testing under this program, support was provided by Chemring Australia. The pyrotechnic test program was predominantly aimed at identifying design weaknesses and as such consisted of:

• Using test items that were naturally aged and were of the same design of those currently in the MEAO. These test items were also significantly older than those lots currently in the MEAO.
• Diurnal temperature cycling.
• Functioning of the items at −30°C.

Optimisation of EO life

Once sufficient data exists to determine a Deployed Life and Tactical Life, it becomes essential, in order to ensure the most logistically supportable lives are established, to optimise the lives by compromising between the following scenarios:

• Scenario One: A maximum Deployed Life, which will result in a minimum Tactical Life.

• Scenario Two: A maximum Tactical Life, which will result in a significantly reduced Deployed Life that may not be sustainable in theatre.
• Scenario Three: A compromise between the Deployed Life and the Tactical Life.

Defining the tactical life

In selecting a defined Tactical Life the complex relationship between Service, Deployed and Tactical Lives is reduced by an order of magnitude. For a given Tactical Life, the Deployed Life will vary depending on the Service Life remaining at the time the item of EO enters the MEAO.

Limitations on tactical life

When issued for operations, the combination of exposure to an uncharacterised mechanical environment, combined with an extreme thermal environment has the potential to generate unpredictable combinations of item failure in theatre. As the full spectrum of the ADF’s operating environment in the MEAO is yet to be comprehensively characterised, Tactical Lives were selected that balanced the practical considerations of effective war fighting and the risks associated with the effects of uncharacterised operating environments.

Allocation of tactical life

The basis for allocating a logistically supportable Tactical Life took into account the identified failure modes (not just those pertaining to energetic material degradation) by also considering the following:

• Personnel rotation through theatre generally being no longer than six months.
• Regular maintenance intervals for vehicles which require the vehicle to be de-ammunitioned.
• Real-life surveillance data obtained from both the extant ADF EO surveillance programs and defect reporting systems.

Once the Tactical Life for an item was set, an optimum Deployed Life was calculated which is dependent on the consumed Service Life. As an example, Table 1 provides details where, depending on the age of the item at the time of deployment, it may be possible to obtain a substantial Deployed Life whilst allowing for an operationally practical Tactical Life (given the deficiencies in environmental characterisation).

For the example shown in Table 1, if TSN 00121 is deemed to require a Deployed Life of 24 months from the date of arrival in the MEAO, then it must have at least 76 months of the Service Life remaining. In other words, the subject LOTs of TSN 00121 can have an age of no more than 44 months from Date of Manufacture (that is, 120 months less 76 months), when arriving in theatre in order to achieve a Deployed life of 24 months.

Summary of findings

Through a rigourous process of age and design related testing, detailed analysis of available ‘real life’ surveillance data and optimisation, QinetiQ Novare has been able to significantly improve the deployed life of ADF EO in the MEAO. Coupled with the application of a fixed Tactical Life, the conduct of this task has resulted in an average increase of:

• 300% in the Deployed Life for all small and medium calibre ammunition;
• 400% in the Deployed Life for all pyrotechnic items; and
• 700% in the Deployed Life for all other item natures.

The increase in the Deployed Life for the majority of the items in the MEAO will realise significant dollar savings to the CoA in the areas of logistic replenishment of deployed EO and in-theatre disposal of life-expired EO. These increases in Deployed Life will also provide significant, though unquantifiable, savings and benefits in the operational capabilities that the assessed items of EO provide in the MEAO. Certainly with the implementation of more robust surveillance strategies and further collection of ‘real-life’ surveillance data it may be possible, in some instances, to obtain further increase in EO lives, thus allowing the CoA to realise even greater savings and benfits over the longer term.

Acknowledgments

This task was completed by a team of QinetiQ Novare staff in order to support an urgent ADF operational requirement. This team consisted of the following personnel who provided significant input and dedicated long hours to ensure the outputs of this project met the ADF’s requirements: Mr Daniel Christie, Mr Paul Hitchings, Mr Daniel Hutanu, Mr Mike Manchee, Mr Dennis Nothdurft, Mr Duncan Watt and Mr Greg Wilcock.

References

Author

Michael Rigby is a Senior Explosive Ordnance Engineer with QinetiQ Novare. Michael completed his BEng (Mech) (Hons) in 1999 at the University of Technology, Sydney Australia and his MSc (EOE) at the Royal Military College of Science, Shrivenham (a part of Cranfield University), United Kingdom in 2001. Michael has over 16 years systems engineering, EO design and EO and weapon system test and evaluation experience. His email address is mtrigby@QinetiQ.com and his contact number is +61 421 556 009.