N222-120 TITLE: Next-generation Underwater Life-support System (Rebreather)

OUSD (R&E) MODERNIZATION PRIORITY: Biotechnology

TECHNOLOGY AREA(S): Biomedical; Human Systems; Materials / Processes

OBJECTIVE: Develop a next-generation underwater life-support system (rebreather) with improved oxygen supply and/or carbon dioxide removal.

DESCRIPTION: Open circuit self-contained underwater breathing apparatus (SCUBA) wastes much of the usable oxygen (O2) in divers’ bottled gas and produces bubbles that limit its use in covert operations. The closed circuit underwater breathing apparatus (CCR) extends dive times and supports covert operations by eliminating telltale bubbles. Carbon dioxide (CO2) scrubbers contribute much to the overall size and weight of rebreather rigs. Rebreather fatalities may result when divers exceed capacities of either scrubbers or oxygen bottles. Therefore, the Navy seeks new technologies that will improve rebreather safety and mission endurance by reducing the limitations and risks associated with present CO2 scrubbing materials and compressed oxygen gas. Due to size and power constraints, new chemical processes will be needed. Ideal features for the final product form factor would be modular, no larger than current rebreather components, low power requirements (not to exceed 2 kg Li-ion battery); and include appropriate sensors and control systems. System needs to produce oxygen and/or scrub CO2 at a rate to match metabolic rates of an active diver in missions lasting up to 10 hours. Note that a functional system must scrub CO2 effectively for the full duration of the mission, but oxygen production may be supplemented by bottled oxygen to meet full mission duration. Optimal designs eliminate CO2 (not as a gas form into the water) through chemical conversion instead of storing scrubbed CO2 within the rebreather unit.

PHASE I: Develop a concept for a life-support breathing apparatus that improves oxygen supply and/or CO2 removal improved underwater life-support system (rebreather). Demonstrate feasibility through analysis and limited laboratory demonstrations. Provide energy estimates matched to human metabolic demands, energy source, cost of system, cost per dive, and reliability estimates, including lifetime expectancy and lifetime cost estimate. The required Phase I deliverables will include: 1) a research plan for the engineering the design of the life support system; 2) a preliminary prototype, either physical or virtual, capable of demonstrating capability of the design; and 3) test and evaluation plan including data collection guidelines and identification of proper controls. Important considerations should include ability to resist corrosion and fouling. Phase I will provide key information about the uses and limitations of the system and could include rapid prototyping and/or modeling and simulation.

PHASE II: Develop, demonstrate, and validate the life support system prototype based on the Phase I design concept. The system should be tested under expected operational environmental conditions (e.g. temperatures, pressures; potential contaminants. Ideal features for the final product form factor would be modular, no larger than current rebreather components, low power requirements (not to exceed 2 kg Li-ion battery); and include appropriate sensors and control systems.

PHASE III DUAL USE APPLICATIONS: Develop prototype into a functional system as agreed to by an appropriate sponsor. Operationally relevant conditions (e.g., greater depths and prolonged dives) may necessitate additional development. System would have value for commercial/recreational diving as well as potentially life support systems for underwater manned vehicles or facilities.

REFERENCES:

1. Fock AW. Analysis of recreational closed-circuit rebreather deaths 1998-2010. Diving Hyperb Med. 2013 Jun;43(2) 78-85. PMID: 23813461.
2. Selective production of oxygen from seawater by oxidic metallate catalysts. T. P. Keane and D. G. Nocera, ACS Omega 2019, 4, 12860–12864

KEYWORDS: Oxygen generation, electrochemistry, carbon dioxide scrubbing