A Woolley, M Riding, V Pit and R Mead, Defence Science and Technology Organisation, Australia SUMMARY
The Defence Science and Technology Organisation (DSTO) has embarked on a research program to deliver to the Royal Australian Navy (RAN) a capability to assess the conformance of maritime platform designs against habitability requirements. The primary deliverable will be a platform habitability assessment software tool that outputs a measure of habitability conformance, known as the Platform Habitability Index. The Platform Habitability Index will amalgamate assessments relating to the platform’s compartment size requirements, victuals and the platform’s environment.
Subsequently, it will allow for identification of habitability deficiencies within a proposed design and, therefore, enable risk identification. That is, it will allow for identification of areas within a platform design that do not (fully) conform to habitability specifications, thereby facilitating decisions regarding platform redesign or to allow the conformance issue to remain and develop mitigation strategies that allow for crew comfort. This paper presents an overview of the research program and how it may be utilised to provide holistic platform assessment during mission scenario simulation. Rules for platform habitability will be defined and assessment utilising the Platform Habitability Index exemplified.
NOMENCLATURE
ADF Australian Defence Force DMO Defence Materiel Organisation
DSTO Defence Science and Technology Organisation HVAC Heating, Ventilation and Air Conditioning IPSM Integrated Platform System Modelling MOTS Military-off-the-Shelf
MPD Maritime Platforms Division MRS Materiel Requirements Set
NAPSA Naval Architecture and Platform Systems Analysis
QofL Quality of Life
RAN Royal Australian Navy
1. INTRODUCTION
The Platform Habitability Modelling and Assessment program is designed to deliver to the Royal Australian Navy (RAN) an assessment capability to measure maritime platform habitability conformance for defined mission scenarios. For this program, platform habitability encompasses compartment size requirements, victuals and platform environmental conditions including noise, vibration, lighting and air quality. The aim is to develop a habitability assessment software tool utilising RAN design guidelines for habitability. The tool will be utilised to determine if conceptual/bespoke or Military
off-the-Shelf (MOTS) maritime platform designs are suitable for crewing according to the Australian Defence Standard DEF(AUST) 5000, the Australian Defence Force (ADF) maritime Materiel Requirements Set (MRS) [1]. Utilising the platform habitability assessment software tool, simulations will generate temporal platform habitability assessment for specific mission scenarios when physical systems, such as diesel engines, batteries, and heating, ventilation and air conditioning (HVAC) are in respective modes of operation.
The Platform Habitability Modelling and Assessment program will not perform human factors research relating to noise, vibration, atmospheres, victualling or workload and fatigue modelling. Instead, other research programs, primarily within the Defence Science and Technology Organisation (DSTO), will provide relevant input to aid the development of the maritime platform habitability assessment capability. Further, to allow for completion of a prototype platform habitability assessment software tool, the research program is constrained in scope:
the prototype does not cater for the crew’s temporal performance degradation;
the crew is considered to be a single entity and there is no consideration for individualisation;
there is no consideration for psychological effects on crew performance; and
the prototype is not capable of generating platform design requirements based on mission scenarios.
The Platform Habitability Modelling and Assessment program constitutes part of the Integrated Platform System Modelling (IPSM) Framework to perform holistic maritime platform system integration and endurance assessments [2]. The IPSM Framework will assist the RAN and the Defence Materiel Organisation (DMO) in decision-making for: platform acquisition;
configuration change; through-life upgrade; platform life extension; and conceptual platform design assessment.
This paper presents an overview of the Platform Habitability Modelling and Assessment program, including example algorithms associated with habitability conformance for RAN maritime platforms and their use in habitability assessment, as measured by the Platform Habitability Index. The paper will conclude with identification of future work and the potential for inclusion of crew performance. The research is being performed by the Naval Architecture and Platform Systems Analysis (NAPSA) Group of Maritime Platforms Division (MPD), DSTO.
2. THE IPSM FRAMEWORK
The IPSM Framework provides a capability to model multiple platform designs within a consistent and robust framework [2]. Within the framework, platform systems and components are modelled in modular form to represent systems such as, for example, the platform’s
‘Power and Energy’ system, which would incorporate fuel subsystems, batteries and diesel engines. Platform habitability, itself a system, is also represented as a component module. Module parameters are configured to reflect the performance of each platform system, as provided by manufacturers or derived from empirical sources. Mission scenarios are defined as a state machine, which enables a platform design model to be exercised. Constraints defining mission success are added to the mission profile prior to the simulation, along with parameters defining mission phases.
Prior to simulation, an initial evaluation of platform habitability is performed against static requirements such as compartment sizes and lighting. Other habitability measures such as noise, vibration, and platform environment are then modelled against the mission profiles. Assessment of victualling can be a static calculation performed prior to simulation when mission duration is known or if wanting to assess the platform against the platform’s requirements specification; or it can be a temporal calculation modelled against mission profiles. During respective mission phases, different propulsion capabilities may be operating, each with their own noise, vibration, air temperature and air quality effects that may be detrimental to the habitability of the platform. The habitability assessment of such factors will enable the provision of advice relating to the habitability conformance for the platform design.
The IPSM Framework will be utilised to model holistic platform configurations; and to test high level platform capability requirements and configurations against a range mission profiles. The IPSM Framework enables timely comparison of multiple platform designs and design configurations thereby facilitating validation of integrated system designs prior to continuing with platform acquisition or upgrade. Utilisation of the IPSM Framework therefore enables early platform design configuration assessment; and the de-risking of design issues prior to such issues becoming apparent during later acquisition phases or through-life.
3. PLATFORM HABITABILITY
Deficiency within a maritime platform crew implies that the crewing system has a reduced capability and, in some situations, this deficiency inhibits the platform from leaving port. The performance and capability of the crewing system is affected by many factors, including the environment within which the crew performs its duties.
For example, prolonged exposure to noise and vibration can increase the effect of crew fatigue; the build-up of
various gases and airborne particulates can cause respiratory issues; confined working conditions could influence the psychology of the crew; and lack of fuel, that is food and water, affects platform endurance. Such habitability issues can create deficiencies within a crew and therefore affects the capability of the platform.
The MRS defines the term ‘Quality of Life’ (QofL) as a measure for crewing RAN platforms [1]:
QofL is thought of as a multi-dimensional concept, defined as factors that promote physical, psychological, and social well-being, as determined by the actual environment and by the perceptions of individuals. The way individuals perceive their lives overall is typically measured as the sum of their feelings about a number of different domains (or aspects) of life. The ship’s accommodation is just one of those domains. Measuring QofL needs to separate and measure objective and subjective factors.
Within the QofL, psychological, physiological, social, furnishing, health and safety, environmental, décor and spatial requirement factors provide for platform habitability, many of which may be objectively and quantitatively measured. To enable this, the MRS provides specific rules and regulations regarding allowable levels for platform habitability. That is, the MRS provides rules relating to static measurable thresholds. However, since these are static thresholds, there is no allowance for minor deviation. For example, any habitability metric that is measured to be just within the associated threshold will be assessed as passed. If it deviates by a fraction then it may be assessed as having failed. Also, the MRS, generally, does not allow for temporal exposure to factors that affect crew performance. For this reason, the initial prototype of the maritime platform habitability assessment software tool only considers boundary thresholds defined in the MRS.
Future refinement of the habitability assessment tool will allow for deviation and temporal assessment in relation to the threshold conditions. For the development of the prototype platform habitability assessment software tool, only the following platform habitability conditions were considered:
1. noise;
2. vibration;
3. lighting;
4. environment;
5. compartment sizing; and 6. victualling.
Aspects of habitability not considered for inclusion were:
ship motion and social factors. Aspects of ship motion, in relation to habitability, are defined within the MRS as:
sleeping accommodation and safety risk spaces like the galley and associated dining facilities are to be positioned within the ship where motions are at acceptable levels against the criteria [1] and these will
therefore be implicit within the assessment for platform compartment sizes and configuration. The second exclusion, social factors, is psychological in nature and cannot be easily quantitatively measured and assessed.
However, components of social factors will also be implicitly recognised in the assessment for platform compartment sizes and configuration.
Rules governing habitability vary depending on location within the platform. Work space habitability rules, for example, are not as stringent as the rules in areas designated as living spaces where the crew will rest and recuperate. Therefore, with this in mind, platform habitability requirements were categorised into the four platform habitability metrics presented in the first row of Table 1. Measures associated with each metric are presented beneath the respective metric and these will contribute to the Platform Habitability Index.
Environment Work Space Living Space Life Needs Oxygen Noise Noise Food Carbon Dioxide Vibration Vibration Water
Particulates Light Light Hygiene Temperature Area/Volume Area/Volume
Humidity Sleep Space
Table 1: Habitability metrics and measures for platform habitability assessment.
4. PLATFORM HABITABILITY INDEX The Platform Habitability Index is a single valued metric used to assess the degree of habitability conformance for crewing an RAN maritime platform. Initially comprised of the four metrics presented in Table 1, the Platform Habitability Index will enable decision-makers to identify areas of platform habitability deficiency, thereby allowing them to determine if the deficiency requires rectification (by performing habitability trade-offs with areas that may exceed habitability requirements or, alternatively, by re-designing the platform); or to accept the deficiency as an acceptable risk to crew comfort and safety and continue with the design.
The four habitability metrics contributing to the Platform Habitability Index are defined in the following subsections. A fifth metric, provisionally referred to as Work-Leisure, will take into consideration the crew’s performance and work-life balance. However, the Work- Leisure metric requires a separate research program relating to workload and fatigue modelling, watch keeping cycles and crew complement. It is therefore beyond the scope of the current research program.
4.1 ENVIRONMENT
The Environment metric will enable assessment of the platform’s atmospheric and environmental conditions to which the crew will be exposed. These conditions can affect crew health, such as respiratory conditions, thereby reducing the capability of the crew system. The
Environment metric includes oxygen and carbon dioxide levels, temperature, humidity and levels for airborne particulates. At the time of writing, the MRS relating to air quality and purification for submarines has yet to receive authorisation for publication. However, the occupational hygiene project for the RAN Oberon Class Submarines [3] presents aspects of air quality and associated reference material that may be utilised in the absence of an official RAN standard. The measures of temperature and humidity have been defined within the MRS and can be assessed. The prototype habitability modelling and assessment software tool will not assess crew performance or health resulting from these environmental conditions.
4.2 WORK SPACE
The Work Space metric assesses habitability factors in the working environment. To enable this assessment, the Work Space is sub-divided into relevant platform compartments and the conditions within each compartment will be considered separately. For example, the Machinery Control Room will have allowable conditions different from, say, the platform’s Control Room. Within the MRS, noise, vibration and lighting have defined allowable levels. However, the allowable area required to enable the crew to perform their duties is less defined and is dependent on specific duties: some jobs only require a workstation and, therefore, ergonomic assessment would apply; whereas other duties may require access to machinery, such as diesel engines. For this reason, the command and control work space areas may be estimated, however much of the maintenance and sea keeping tasks cannot be quantified and are therefore not assessable without performing a more extensive sea keeping analysis. Anthropometric studies are outside the scope of the research program and the related data supplied by the MRS requires validation. However, standards do exist [4] that may be utilised in the absence of validated RAN standards. Future research may be required to determine and validate relevant anthropometric requirements for RAN surface ships and submarines.
4.3 LIVING SPACE
Living Space requirements are probably the most stringent requirements on a platform. Lowering irritants and increasing comfort will allow the crew to more easily recuperate and, therefore, be more attentive upon returning to duty. All the respective habitability measures associated with the Living Space metric have defined, and assessable, minimum and maximum thresholds. The Living Space assessment is also sub-divided into appropriate compartments and assessed accordingly.
However, it must be remembered the entire compartment volume will be utilised. For example, to maximise sleeping arrangements, berths will be stacked within the volume so, for the junior sailors, this may be three berths high and for senior sailors it may be two berths high.
4.4 LIFE NEEDS
Rules relating to food and water are presented in the MRS; however the quality of these measures can add or detract from platform habitability. Consider, for example, food. Having enough food affects mission endurance;
however food quality also affects crew morale and, therefore, productivity in the work environment. The Platform Habitability Index will only consider the endurance aspect relating to these measures. Also considered within the Life Needs metric is a measure relating to hygiene, which includes the number of shower and toilet facilities required on the platform.
4.5 DERIVATION
During initial development of the maritime platform habitability assessment tool, the Platform Habitability Index will output either that the platform has passed the assessment for defined habitability requirements or it has failed. To perform the assessment, the Platform Habitability Index will amalgamate assessments relating to the habitability metrics presented in Table 1. In its simplest form, the Platform Habitability Index can be expressed as the boolean equation:
PHI = Environment ^ WorkSpace ^ LivingSpace ^ LifeNeeds
where: PHI is the Platform Habitability Index; and
^ is the logical function: AND.
Assessments for each of the four habitability metrics are, therefore, also rated as PASS or FAIL. However, continued development of the Platform Habitability Index will have the metric presented as a (normalised) value to indicate the level of conformance to habitability requirements. One such method was presented by Celentano et al [5], which utilised a variation of the weighted average of relatives method for determining the habitability index for space platforms.
5. PLATFORM HABITABILITY RULES Rules and algorithms for RAN platform habitability assessment may be static or temporal in nature.
Simplified static rules for: vibration levels are presented in Table 2; compartment size requirements in Table 3;
and victuals in Table 4. Simplified temporal rules for noise levels are presented in Table 5. Finally, simplified light level requirements are presented in Table 6. These rules were derived from relevant volumes of the MRS [1].
Location
RMS Velocity
(mm/s)
RMS Acceleration
(mm/s2) Cabins, Lounges and Offices <2.2 <98 Workshops, Galleys and Control
Stations <5 <220
Unoccupied Spaces <10 <440
Table 2: Simplified allowable vibration levels.
Location Area (m2)
Wardroom ScaleFactor × #Officers × %CrewAccommodated Senior
Sailors Mess
ScaleFactor × #SeniorSailors
× %CrewAccommodated Junior
Sailors Mess
ScaleFactor × #JuniorSailors
× %CrewAccommodated
Galley ScaleFactor × TotalCrewSize Officer
Cabins FloorArea × #Officers ÷ #OfficersPerCabin Senior Sailor
Cabins
FloorArea × #SnrSailors ÷ #SnrSailorsPerCabin + BunkSpace + CrewStorage
Junior Sailor Cabins
FloorArea × #JnrSailors ÷ #JnrSailorsPerCabin + BunkSpace + CrewStorage
Ablutions
(ShowerArea × TotalCrewSize ÷
#PersonsPerShower) + (ToiletArea × TotalCrewSize ÷ #PersonsPerToilet)
Table 3: Simplified compartment size requirements, where ScaleFactor allows for pipe work and electrical.
Location Volume (m3)
Freezer ScaleFactor × (Meat + FrozenFoods) × TotalCrew
× MissionDuration Cool Room
(Dairy)
(ScaleFactor × Dairy + ScaleFactor × SmallGoods)
× TotalCrew × MissionDuration Cool Room
(Fruit &
Vegetables)
ScaleFactor × FruitVegetable × TotalCrew × MINIMUM(FruitVegetableShelfLife,
MissionDuration) Dry
Provisions
ScaleFactor × GeneralGroceries × TotalCrew × MissionDuration
Thawing Room
ScaleFactor × ThawVolumePerPersonPerDay × TotalCrew
Enlisted Crew Canteen and
Drinks
ScaleFactor × (Canteen + Spirits) × TotalEnlisted × MissionDuration + ScaleFactor × (Beer + SoftDrink) × TotalCrew × MissionDuration +
ScaleFactor × Garbage × TotalEnlisted × MissionDuration
Commanding Officer &
Wardroom Stores
ScaleFactor × (Drinks + Garbage) × #Officers × MissionDuration
Potable Water
ScaleFactor × WaterNeedsPerPersonPerDay × TotalCrew × 2 days
Table 4: Simplified victual requirements.
Decibels 1 Hour 8 Hours
16 Hours
24
Hours Infinite 120
O with EP &
EM
No No No No 110 D with
EM
D with EM
O with
EM No No
100
D with EP or
EM
D with EM or EP
O with EP or
EM
O with EP or
EM
No
85 D D D O with
EP or EP
No 80 D D D D D
Table 5: Simplified allowable noise exposure levels and durations for RAN platforms. [O = occasional exposure;
D = daily exposure; EM = ear muffs; EP = ear plugs]
Platform Lux
Occupied Spaces 150 Unoccupied 100 Work Bench 300
Table 6: Simplified allowable light levels.
To enable assessment of conceptual platform designs, or designs supplied by a manufacturer contending for an acquisition contract, relevant platform habitability measurements may be discerned from sources such as design drawings and manufacturer specifications. During the initial development of the IPSM Framework, which will include habitability assessment, this is likely to be a time consuming process resulting in simplistic assessments. However, continued expansion of the IPSM Framework will enable the development of a library of system models and related options, with associated specifications, that will facilitate timely and more detailed assessments. Some details though, such as work and living space dimensions will need to be calculated from the platform design drawings and, therefore, will not form part of the system library; volumes for food and water storage may also be determined from the design drawings and manufacturer specification. Interior lighting, though, may be estimated by calculating the total lumens emitted by the light fittings (which would be stored within the IPSM Framework system library) divided by the compartment’s surface area (incorporating decks, bulkheads and deck head areas as calculated from the design drawings). Atmospheric conditions would be calculated by considering the specifications for the HVAC units within the platform.
Finally, noise and vibration for a compartment is dependent on the systems and machinery within the compartment, such as diesel engines and HVAC.
Without belabouring the point, the relevant noise and vibration specifications for the diesel engine and HVAC options will also be stored in the IPSM Framework system library. Noise and vibration propagation through the platform may not be easily calculated and will require consultation with relevant subject matter experts.
Having calculated the relevant habitability measurements for a proposed platform design, assessment utilising the respective habitability rules is performed and aggregated to give a measure for the Platform Habitability Index.
Within the IPSM Framework, relevant system values (such as diesel engine noise and vibration) will also form part of the platform integration analysis to allow for comparison of platform configuration options. For example, submarine platform habitability assessment may be performed for propulsion and energy configurations of: battery; air-independent propulsion;
and traditional diesel engines to determine the effects not only in relation to submarine endurance but also on habitability.
6. HABITABILITY ASSESSMENT
Static platform habitability assessment is performed independently of the platform simulation environment.
For example, compartment size assessment, which may be performed using naval architecture software, may be performed prior to or at the conclusion of the simulation and then amalgamated to provide a measure for the Platform Habitability Index. Some assessments, such as those relating to the consumption of food, may be performed independently of the simulation environment when the mission duration is known. However, there will be instances when mission duration is unknown and so, food consumption will be modelled during the simulation.
Longer term development may also include the ability to model replenishment-at-sea.
A method for presenting the results of the assessments may be the use of ‘spider charts’ (also known as polar charts and Kiviat diagrams, among others) as shown in Figures 1 and 2. In these spider charts, the dashed line represents the minimum acceptable level of habitability, referred to, in this context, as the habitability margin. If a measure fails the habitability assessment it will be shown to be below the habitability margin. However, care must be exercised when developing the presentation structure for the spider charts. Confusion may arise when presenting information relating to noise assessment, which must be below pre-defined thresholds and light level assessments, which, generally, must be above pre
defined thresholds. The spider charts will present a normalised assessment, such that all assessments will be measured on a scale of 1 to 10, say, and each habitability measure will then have a minimum acceptable habitability margin as determined by the respective maximum or minimum habitability thresholds.
Figure 1: Example platform assessment utilising the Platform Habitability Index comprised of the four habitability metrics.