Naval Special Warfare (NSW) Diver Thermal Human Interface
Navy STTR 2015.A - Topic N15A-T012
ONR - Ms. Lore-Anne Ponirakis - [email protected]
Opens: January 15, 2015 - Closes: February 25, 2015 6:00am ET

N15A-T012 TITLE: Naval Special Warfare (NSW) Diver Thermal Human Interface


ACQUISITION PROGRAM: PMS 340, Naval Special Warfare

OBJECTIVE: Develop highly streamlined and efficient diver worn components, connectors and fluid delivery lines for a wet submersible that provides a source of heated or cooled seawater for operators in extreme ambient undersea conditions.

DESCRIPTION: The Navy needs to improve the human interface to the SEAL Delivery Vehicle (SDV) active thermal systems. To accomplish this, the following three main areas need to be addressed: 1) properties of the diver suit design including improvement of heat transfer from a heat source thereto, 2) improvement in the location, reliability, and operability of quick disconnect umbilical’s from the diver to the heating system, and 3) improvement in the thermal performance characteristics of the delivery components that carry the heated/cooled water from the source to the diver and back..

Operation in water that is colder or warmer than thermally neutral temperatures, roughly 91 degrees F, limits exposure time, exercise capacity, function, and cognitive performance of divers. In particular, operating in temperatures extremes at or near 35°F or above 95°F limits performance and risks serious injury. Specialized solutions have been developed to provide thermal control based on circulating liquid through tubes integrated into a flexible suit. The current suit approach to operating in cold water consists of several layers. The first is an undergarment, such as polypropylene knit fabric. Over the undergarment is the tube suit, made of flexible material that incorporates tubing which warm water runs through to maintain the diver’s body temperature. On top of the tube suit is an insulation layer to reduce heat loss from the tube suit to the cold water. The outermost layer is a diver dry suit.

Current tube suits and connections to them are bulky, making it difficult for divers to move quickly or comfortably. Thinner layers with better insulation performance are desirable. Furthermore, integration of the tube layer and the insulation layer may further reduce bulkiness. Also, donning and doffing these types of suits is time-consuming, taking up to 45 minutes (Ref 1). Commercial hot water suits have been available for divers working in cold water (Ref 2), such as offshore platforms in the North Sea. However, these suits are not suitable because they are connected to large water heaters on offshore platforms that are capable of heating supply water to 98°F or higher. These large systems supply the hot water to the diver via an umbilical. In these commercial suits, heating water is not recirculated, but is instead vented out through the wrists and ankles of the suits. Electrically heated suits are used in other applications, but raise concerns regarding reliability, safety, and flexibility of the heating elements and are not considered in the scope of this solicitation.

The tube suit was invented by Richard Long (Patent US3449761 awarded in 1969). Recently, a study was done on a tube suit with six separate heating zones (Ref 3). Hot water was circulated through the tube suit and then returned to the heater through an umbilical. This work showed that maintaining temperature (heating and cooling) is possible but at significant power. Prior work based on Thinsulate™ insulation, a 3M product, and Aerogel, a synthetic porous ultralight material derived from a gel showed promise in improving suit thermal characteristics. Similar materials, as well as reflective metallic foils and coatings, may improve the insulation layer. Heat transfer from the tube layer to the diver may also be enhanced with coatings, and the variations of their integration between the layers could improve the performance as well.

Very efficient active thermal systems and suits, for use by tube-suit wearing divers in a wet submersible such as the SEAL Delivery Vehicle (SDV), are needed since the heating system must be located in the vehicle, with stringent size, weight, and power (SWaP) restrictions. In the SDV, up to 8 divers would be connected to a source that circulates hot (~104F) water to them via fluid lines and umbilicals that must be thermally efficient. In addition, diver components must incorporate penetrators and connectors that are wet-mate able and easy to manipulate, especially for and connecting and disconnecting. The umbilicals and penetrators must be positioned to enable both comfort and rapid egress from the vehicle if required.

The guidelines below set some performance goals for these systems based on continuing government tests and studies. These goals are not meant to be all inclusive nor limit innovation.

a. Passive insulation minimum: 1.4 clo (clothing insulation value to ensure "come home" capability should the fluid source be degraded or fail).

b. Maximum fluid heat loss of 250W between the entry to and exit from the diver liquid circulation garment, with a flow rate of .4 gallons per minute at 32 degree F ambient seawater conditions. At this ambient temperature, idealized models estimate 150W is required to maintain diver thermal neutrality (excluding hands and feet) with the remaining heat (100W) lost to the environment.

c. Maximum heat loss of fluid delivery line: 8W per foot with the line submerged in 32 degree ambient seawater and carrying 105 degree F fluid at a flow rate of .4 gallons per minute.

d. Minimize bulk and maximize ease of use.
i) For the diver-worn "suit", this can be achieved through emerging materials, or by integrating the three layers for "current generation" systems (passive, liquid circulating suit and dry suit) into two garments or even one that are less bulky and faster to don/doff.
ii) Connectors: These include the attachment from the fluid delivery line to the umbilical, and from the umbilical to the diver suit penetrator. Suit penetrators should add minimum bulk to the diver, be easy to operate, and reflect consideration for manufacturability. For example, a penetrator that can be released with one "claw"-gloved hand in poor visibility (low light, murky water) and reattached within 30 seconds may be more favorable than a less bulky version that reattaches in half the time, depending on cost and manufacturability.

e. Efficiency: Several areas offer potential for maximizing efficiency of the Human interface and fluid deliver lines. For example:
i) Ability to leverage "tube" patterns in the liquid circulating garment that cover less surface area but deliver the same thermal effect (Ref 3).
ii) New materials and manufacturing techniques such as "dustless" Aerogel materials or encasing methods.

f. Trade off considerations:
i) In general, less efficient but more easily manufactured components will be more desirable than far-off solutions. Time to manufacture is a more important consideration, so "80% solutions" that could reach full production in 24 months are more favorable than "100% solutions" utilizing emerging materials that may not be ready for production for five years. Participants may also choose to present a "phased" approach that presents alternatives for increments that deliver in near and longer terms.
ii) Solutions that consider thermal balance to include extremities will have an advantage over those that do not.

Note: The Naval Special Warfare is in the process of obtaining metrics and feedback for current prototypes under test and will provide those as they become available during the SBIR life cycle.

PHASE I: The company will develop a concept for a comprehensive and efficient human interface to the SDV’s emerging thermal system that will provide heated or cooled seawater based on ambient conditions. The company should verify expected thermal performance improvement via modeling and simulation using computerized heat transfer analyses. The materials and combinations of materials should be evaluated for thermally efficient tube suits. The effort also includes the development of concept designs for quick disconnect penetrators that require minimum visibility and dexterity, and evaluate new connection interfaces between the suits and the heating /cooling system. Feasibility will be established by a combination of modeling, documented approaches, design concept review, and an integration approach. No human testing is anticipated for this Phase.

PHASE II: Based on the results of Phase I and the Phase II contract statement of work, the company will build one or more prototype suits and the related interface components to verify performance in a relevant environment under real-world conditions. The prototype will be evaluated by the Navy to determine its capability in meeting Navy requirements for the Diver Human Interface System. This may require human subject testing. System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters to include: Form Fit and Function evaluations; operating pressures of 120psi; operating temperatures of sea water between 35 to 95 degree F; flow-rate of 0.4-0.6 Gallons-per minute. Evaluation results will be used to refine the prototype into a design that meets Navy requirements. The company will prepare a Phase III development plan to transition the technology for Navy use. If human testing is proposed, company must provide production-ready prototypes to the Navy for manned testing at the Naval Experimental Dive Unit (NEDU) and requisite documentation of materials used to fabricate or produce items.

PHASE III: The company will provide support in transitioning the technology for Navy use. The company will develop the suit and related hardware according to the Phase III development plan for full testing and evaluation to determine its effectiveness in operationally relevant environments. The company will also support the Navy for test and validation to certify and qualify the system for Navy use, and build and test several systems for use in actual field conditions and trials.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial divers working in cold water, offshore oil rig environments could benefit greatly from this technology. The technology could be applied to other non-maritime applications where a protective suit is required for mobile or dismounted operations such as bomb squad, disaster recovery, or HAZMAT tasks. The subcomponents for quick disconnect and umbilical connections could be applicable to other systems such as unmanned underwater vehicles (UUV) thermal/cooling systems, ground vehicle and aerial vehicle-based, and human cooling systems.

1. Dry Suit Diving: A Guide to Diving Dry By Steven M. Barsky, Dick Long, Bob Stinton; 2006;

2. Viking hot water suit (example):

3. David R. Pendergast, Joseph Mollendorf, "Exercising divers’ thermal protection as a function of water temperature", Undersea & Hyperbaric Medical Society, Inc., 2011, Vol. 38, No. 2 – DIVER THERMAL PROTECTION, p 127-136

4. DUI Blue Heat suits:

5. DUI hot water suit (example):

6. Battery powered heating (example):

KEYWORDS: Diver thermal improvement; diver thermal umbilical’s; quick disconnect; SEAL Delivery Vehicle (SDV) active thermal; tube suit thermal improvement, diver thermal human interface

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