This section discusses design considerations for the layout and design of stowage systems inside an underwater habitat. It also provides the characteristics of a successful onboard inventory management system design. Such a system can track the quantity, location, and status (e.g., remaining useful life) of inventory items. The inventory management function is one of the primary elements of onboard information management.
[Image: FORTEPAN / Lissák Tivadar / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)]
Stowage – General Considerations
A stowage system inside an underwater habitat can be integrated with a crew station or may be a separate area apart from the normally occupied areas. A stowage area should be seamlessly integrated with an inventory management and disposal plan. The stowage system affects every aspect of crew operations, and insufficient stowage has a severe negative impact on crew operations and efficiency.
Efficient stowage systems are important to maintain inventory in a consolidated location and to avoid unnecessary conflict and collision with supplies and tools that are not in use. A stowage system contributes to interior order of supplies and hardware and can also be seen as a positive psychological feature. An interior that is messy because of bad or missing stowage may promote stress and irritation for crew members. Lack of awareness of the location of specific items and spending unnecessary time to find these will decrease crew performance, increase task performance time, and pose a danger in emergency situations.
Underwater habitat stowage conditions can negatively and positively affect habitability, operations, and safety. Definition of requirements for the amount and type of stowage provided for future missions must be based on mission scenario, mission duration, crew size, and specific mission tasks. Stowage “keep out” zones must be established and enforced to protect access to critical equipment and controls such as fire ports. The negative effects of poor stowage include increasing crew time to perform daily operations, violating safety constraints associated with maintaining “keep out” zones around critical equipment and controls (e.g., fire ports, lighting and ventilation sources).
Type and Location
Items should be stored in an area as close as possible to where they are used. The following is a list of crew stations and the types of equipment that should be stored adjacent to these stations:
- Equipment Dryer – wet equipment and devices for ventilation and drying
- Equipment Stowage – dry equipment like suits, BC’s, gloves, footlets, masks, regulators, hooks, lamps, new replacements
- Tank Room – tank tub (if tank filling compressor planned), designated area for empty and filled tanks (reinforced walls)
- Compressor room – compressor, corresponding tools
- Personal Stowage – clothing, personal equipment and belongings, personal hygiene items
- Workstation – writing equipment, camera equipment, recording equipment, emergency equipment (e.g., extinguisher, first-aid equipment)
- Workshop – spare parts, tools, benches, repair materials
- Hygiene – personal hygiene consumables (tissues, wipes, towels, soap)
- Housekeeping – detergents, wipes, vacuum cleaners, gloves
- Galley – food, food preparation directions, utensils, wipes, housekeeping supplies
- Recreation facility – recreation items (games, reading materials, audio-visual equipment)
- Meeting areas – writing materials, presentation aids
- Medical treatment area – medical equipment, pharmaceuticals, dispensary supplies
- Exercise facility – exercise equipment
- Trash management system – wet and dry trash receptacles, trash bags
The area in front of safety critical / emergency equipment requiring crew physical or visual access must remain clear of obstructions (e.g., hardware protrusions and non-standard stowage).
As underwater habitats are resupplied, an off-setting amount of stowage is often not returned or removed, resulting in an accumulation of stowage items. The stowage system should take into account the expected resupply/return of stowage over the habitat lifetime.
To accommodate changing mission needs, the following should be considered:
- Standardized container and cover size and design
- Adjustable shelving and racks
- Bolted or strapped storage racks and containers
- Provisions for stowage installation throughout the spacecraft
Central Storage vs. Distributed Storage
Items should be stored adjacent to their use point. There are cases, however, where this is impractical. A central storage point for some items makes inventory tracking a simpler task. This might include low-use items or items used at many different stations. In many cases a central storage and distributed storage system can be combined. This might occur in the galley, where food for a single meal is stored in a pantry but the entire food supply is stored in a central facility.
Stowage containers must be operable without the use of tools, to maximize the use of crew time.
Stowage systems must be designed to allow for easy access to mission critical and frequently-used items.
Stowage systems must not interfere with translation or other operations.
Stowage locations and items must be labeled to allow easy location, replacement, and inventory of items.
The stowage system must be compatible with the inventory management system.
This section provides the characteristics of a successful onboard inventory management system design. Such a system can track the quantity, location, and status (e.g., remaining useful life) of inventory items.
The inventory management function is one of the primary elements of onboard information management, and is directly related to the stowage design considerations.
An on-board inventory management system (IMS) tracks inventory such as crew equipment, consumables, food, and experiment materials, and where these items are located.
As an example, the tracking methodology for items stowed on the International Space Station has historically been inconsistent. On occasion, items have been moved and not returned to their designated area and the IMS has not always updated to reflect the new location. This has resulted in the crew spending increased time searching for items they need for daily tasks. Data entry inefficiencies have made it difficult to keep track of items.
When designing an IMS, the system should provide a reliable methodology for tracking items, and ensuring that items can be easily placed in their designated locations. Tools for IMS use whether display interfaces (tablets) or scanning devices should be easy to use and accurately provide information to the crew and ground personnel. Once an optimal design is established, crewmembers should be trained to ensure efficient inventory tracking and to avoid mistakes. Onboard ISS, items have often been transferred without updating IMS. It may not be necessary to update an IMS to reflect temporarily stowed items, but the beginning and end stowage locations should be accounted for when items are stowed or transferred.
When developing an IMS consider the following:
- Standardization – A standard process for naming hardware and equipment is necessary. The inventory management system nomenclature must be consistent with procedures and labels.
- Easy to Use – The ability to quickly and easily input data and track items is important for the IMS to be fully used and should be provided. ISS crewmembers have commented that their IMS is too complex.
- Efficient – The amount of time required of the crew to perform the inventory management function should be minimized.
- Unique Names – Each item tracked in the IMS must have a unique name so that it can be uniquely tracked. Barcode labels with unique names, part numbers, and serial numbers helped to track hardware and consumables.
- Training – Pre-operational training for IMS should include realistic scenarios for the maintenance of the IMS to develop the complex skills needed during underwater missions. During missions the IMS should also be properly addressed during crew handover.
- IMS Task Time – Appropriate amounts of time should be provided to allow crewmembers to interface with the IMS. ISS crewmembers have reported that the operations time for tasks often exceeds the allocated time to IMS related tasks.
- Item Location and Identification Information – The inventory management database should include the following data elements:
- Item Number – The number by which each item is identified in the database.
- Item Name – The standard name used to describe the item and its function (consistent with labels and procedures).
- Other Name – Nonstandard (slang) names that are often used by the crew. A database should be able to cross-reference the standard and nonstandard names, which are updatable by the crew or ground.
- Item Category – The category indicates the targeted application for the item.
- Item image – An image of each item in the database would give the first impression, if the the item ID is identical with the desired item without unpacking.
- Depot ID – An ID of the designated depot shows, where to store the item and where to find it again (for example: galley store, technical workshop, housekeeping store…)
- Item Functional Designation – An easy-to-learn code that indicates the functional use of the item.
- Total Quantity – The total quantity of each item during each mission phase.
- Stowage Location Maps – Stowage location illustrations are required to the extent that the difficulty in locating or transferring an item necessitates additional data to support the crew procedures.
- Life Remaining – The shelf life remaining for consumables and the operating life remaining for operating hardware.
- Crew Identification – The name of the crewmember, for personal items.
Inventory Management System Technology
Advances in onboard computers, data storage devices, software, bar coding systems, and communications data links make a computerized IMS less costly and easier to implement. Additional automated systems will likely prove useful in addressing many inventory issues. Bar code scanners greatly reduce errors and require less time than manual entry systems. Radio frequency identification (RFID) tags, which do not require crewmembers to use a bar code scanner, can enable the automated location monitoring of critical equipment, and even locate the equipment.
Bar codes – The ISS crew has noted that the use of a barcode reader with the IMS to track items has been useful. If bar code labels are used, consider the following:
- Bar coding everything is excessive, and uses extra time when managing consumables. A careful evaluation of which items to be coded should be conducted.
- Bar codes can sometimes be hard to scan because of the reflective properties, curvature of surfaces or the size of some of labels. Reflective labels should be avoided.
Reports – The inventory management system must be sortable and searchable such that particular items can be found in the database and/or to prepare various reports. Information must be easily accessible, filtered, and compact. At a minimum, consider the following types of reports:
- Item Status – Display the location(s) for an item that is selected by item number or item name. This report must include the quantity of the item at each location.
- Location Status – Display items (by item number and item name) stowed in a specified stowage location. The quantity of each item in the specified location must be provided.
- Limit Warning Report – An alert message that indicates when quantities of consumables and other items fall below a predetermined limit should be provided.
Note: This article contains adaptations from the NASA Human Integration Handbook (HIDH), NASA/SP-2010-3407. Since supplementary transports are not comparable to spaceflight, many considerations do not apply to underwater operations and therefore had been skipped.