N251-013 TITLE: Passive Cooling/Heating System for Thermal Regulation in Clothing

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials;Sustainment

OBJECTIVE: Develop a novel a passive cooling capability that provides thermal regulation when operating in the aircraft and/or insulation during inwater survival with a minimal impact on bulk and weight.

DESCRIPTION: For Navy and Marine Corps aircrew, the need to wear an anti-exposure coverall is determined by the operational environment air and water temperatures in which they will be operating. Anti-exposure coveralls are required when flying over water temperatures of 60 °F (15.6 °C) or lower and the outside air temperature is 32 °F (0 °C) or below (when corrected for wind chill). Temperatures in the cockpit and aircraft at takeoff and during flight can be much higher as the aircraft departs from a warm environment and operate over cold water that requires wearing an anti-exposure coverall. Current Navy constant wear exposure suits, the CWU-86/P for men and CWU-87/P for women, are required to be worn by aircrew in rotary-wing, tilt-rotor, and ejection seat aircraft when operating in these environmental conditions. The CWU-86/P and CWU-87/P are dry suits and designed to prevent water intrusion into the suit, keeping the layers underneath dry in order to provide the insulation required for survival. The CWU-86/P and CWU-87/P were designed for a 2 hr inwater exposure time and 3–4 hr of wear time. The increasingly common practice of mid-air refueling extends the duration of wear time in flight and extends the potential inwater exposure due to a longer time before rescue. The design does not afford any thermal regulation for comfort during normal flight conditions, which leads to overheating and sweating, and which is distracting and can lead to dehydration and fatigue.

The Naval Air Warfare Center Aircraft Division (NAWCAD) is seeking novel solutions to improve personal thermal management in flight and maintain or improve inwater thermal protection from hypothermia. The solutions must provide aircrew the capability to actively regulate body temperature in flight without degrading in water survival. Increases in body temperature during flight and decreases in temperature during in water survival can impact strength, endurance, cognitive function, and mission effectiveness decrease [Refs 1-3].

More specifically the solution and technology must meet the following requirements. The requirements address both inflight and inwater scenarios. A solution that addresses one, but not both scenarios will be considered, as well as solutions that address both scenarios.

1. The solution must maintain or improve thermal regulation of aircrew when wearing the current inwater configuration of the CWU-86/P or CWU-87/P worn with two layers of long underwear (layer 1: mid-weight, layer 2: heavy weight).
2. This solution must manage moisture build up inside of the exposure suit to reduce the potential of hyperthermia.
3. The solution must insulate the body to reduce heat loss during inwater immersion and survival for 4 hr (threshold) 24 hr (objective).
4. Aircrew must be able to wear the solution for 12 hr, without interfering with operation of the aircraft or mission tasks.
5. The solution must be compatible with aircrew life-support equipment worn over the top of an anti-exposure coverall. For rotary-wing and tilt-rotor aircrew the configuration will include a survival vest with LPU-36/P or LPU-21E/P life preserver, HGU-56/P helmet, gloves, and boots. For fixed-wing, ejection seat aircrew the configuration will include the CSU-15/P anti-g garment, the PCU-58P parachute/restraint harness, the LPU-37/P or LPU-23/P life preserver, the HGU-68 helmet, gloves, and boots.
6. The body core temperature from body heat build-up during operational performance of aircraft must not exceed 101.3 °F (38.5 °C).
7. The body core temperature must fall no lower than 95 °F (35 °C).
8. The hand and foot skin temperature must be no lower than 60 °F (15.6 °C) when immersed in 45 °F (7.2 °C) water for a minimum of 2 hr, and 60 °F (15.6 °C) when immersed in 32 °F (0 °C) water environment for a minimum of 4 hr.
9. The garment must not interfere with bladder relief systems worn with the anti-exposure suit.
10. The solution, when worn as part of the anti-exposure suit configuration must not cause body burn greater than 25%.
11. The solution must follow MIL-STD-1472H (5.8.3.2). For systems and equipment that are life-critical (e.g., accessibility of safety interlocks, clearances for ejection seats, fit of gas masks), the design for all physical factors (size, shape, weight, reach, strength, and endurance) must accommodate the multivariate central 99 % of suitably clothed and equipped males of the target user population and the multivariate central 99 % of suitably clothed and equipped females of the target user population using dimensions applicable to the tasks.
12. The solutions must not require power (objective) and will utilize a portable power source (threshold) when used in the aircraft. Power is not preffered when in water.
13. The solution must not obstruct emergency egress from the aircraft.
14. If applicable, the solution must continue to function as designed after 25 launderings.
15. The solution must maintain functionality for a minimum of 1 deployment (9 months) with minimal maintenance support.
16. The solution must be easily donned by the individual without requiring additional help.
17. The solution must not cause hot spots or rash if in contact with the skin.
18. The solution must meet airworthiness standards (i.e., MIL-HDBK-516).

PHASE I: Design and develop a solution concept of a thermal regulation system for use with a constant wear anti-exposure coverall. Demonstrate technical feasibility of the solution through analysis and limited laboratory demonstrations. Provide cost and reliability estimates. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop, demonstrate, and validate a working prototype for testing based upon the design concept created during Phase I. Conduct laboratory testing and demonstrate thermal regulation capability in a laboratory environment. Demonstration will be conducted in a simulated environmental environment with personnel representing the central 5th to 95th percentile male and female aircrew.

PHASE III DUAL USE APPLICATIONS: Perform final design updates based upon prototype testing in Phase II. Produce systems for flight testing and develop production capability for commercialization. Provide updated engineering drawings, detail specifications, cost and life cycle analysis, maintenance and repair procedures.

The technology developed under this effort can apply to commercial aircrew flying in helicopters over water, commercial fishing industry, commercial applications in which workers are wearing garments to protect from liquid contaminants.

REFERENCES:

1. Westpac Marine Services, Inc. (n. d.). "Hypothermia." https://westpacmarine.com/samples/hypothermia_chart.php

2. Turk, E. E. "Hypothermia." Forensic science, medicine, and pathology, 6(2), 2010, pp. 106-115. https://doi.org/10.1007/s12024-010-9142-4

3. Kraai, E.; Wray, T. C.; Ball, E.; Tawil, I.; Mitchell, J.; Guliani, S.; Dettmer, T. and Marinaro, J. "E-CPR in cardiac arrest due to accidental hypothermia using intensivist cannulators: A case series of nine consecutive patients." Journal of Intensive Care Medicine, 38(2), 2023, pp. 215-219. https://doi.org/10.1177/08850666221116

4. Massif. (n.d.). "2-Piece Flight Suit Jacket (V2) - NAVAIR - (FR)." https://www.massif.com/2-piece-flight-suit-jacket-v2-navair-fr.html

5. Drifire. (n. d.). "DRIFIRE FORTREX FR 2-Piece Flight Suit Pant (NAVAIR)." https://www.drifire.com/drifire-fortrex-2-piece-flight-suit-pant-navair

6. Hur, P.; Rosengren, K. S.; Horn, G. P.; Smith, D. L. and Hsiao-Wecksler, E. T. "Effect of protective clothing and fatigue on functional balance of firefighters." Journal of Ergonomics, 2013. https://www.ideals.illinois.edu/items/107508

7. Goldman, R. F. "Clothing design for comfort and work performance in extreme thermal environments." Transactions of the New York Academy of Sciences, 36(6 Series II), 1974, pp. 531-544. https://doi.org/10.1111/j.2164-0947.1974.tb01599.x

8. Mann, D. and Pezzullo, R. "The US Navy SEAL Survival Handbook: Learn the Survival Techniques and Strategies of America's Elite Warriors." Skyhorse Publishing Inc., 2012. https://search.worldcat.org/title/759908605

9. Ofir, D.; Yanir, Y.; Eynan, M. and Arieli, Y. "Evaluating the thermal protection provided by a 2?3 mm wet suit during fin diving in shallow water with a temperature of 16-20°C." Diving and Hyperbaric Medicine, 49(4), 266, 2019. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039775/

10. Curtis, R. "Outdoor action guide to hypothermia and cold weather injuries." Outdoor Action: Princeton University, August 8, 2024. https://www.princeton.edu/~oa/safety/hypocold.shtml

KEYWORDS: Exposure Suit; Heating; Cooling; Passive; Clothing; Thermal Regulation

TPOC 1: Katrina Colucci-Chang
(571) 502-1772
Email: [email protected].

TPOC 2: Tara Capecci
(301) 342-921
Email: [email protected]

TPOC 3: Joshua Pettis
(301) 757-164
Email: [email protected]

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