276 WET SUITS 



OBJECTIVES 



The principal technical objective was to evaluate the concept of an electrically heated 

 pressure-compensated wet suit under actual operating conditions. The concept of supplemental 

 electrical heating in a non-pressure-compensated suit had already been established in the lab- 

 oratory by the Naval Medical Research Institute. Another important objective was to provide 

 thermal protection for Sealab II aquanauts, with the view of increasing their useful work time 

 in the water. One of the earliest objectives was to survey the various means of providing sup- 

 plemental heating and pressure-compensated insulating material and to make selections based 

 mainly on the most expeditious design and hardware procurement. The overall objective of the 

 program was to accomplish a first step in the development of an electrically heated pressure- 

 compensated wet suit. 



STATEMENT OF THE PROBLEM 



The problem, as stated in the negotiated contract, was to: "Provide the necessary research, 

 development, and engineering tests, as required, to supply electrically heated garments for use 

 in maintaining thermal comfort of underwater swimmers operating in water of down to 40° F. 

 and at a depth of 320 ft for periods of up to four hours. This procurement shall include both the 

 insulative garment with electrical heating system incorporated and battery power supply so as 

 to provide approximately one (thermal) kilowatt hour as required by the swimmer. The rate 

 shall not be more than 350 watts. The garment shall likewise be designed to have power sup- 

 plied through a 100-ft power cable so as to permit heating the suit from a power source within 

 the Sealab n compartment or other source. Four cables and four sets of batteries are to be 

 supplied." 



Eight experimental suits were to be delivered on or before Aug. 31, 1965, allowing only 

 eleven weeks for the contract program. The main problem was in the time frame of the pro- 

 gram rather than in some technological aspect of the work. A request was made to accelerate 

 the schedule even more and to deliver the suits on Aug. 7. This was done. 



PLAN OF THE REPORT 



The technical discussion in this report features mainly the highlights of the program. De- 

 tailed technical information is given for some aspects of the work. Both negative and positive 

 results of materials evaluation are discussed, with the hope that such discussion will be benefi- 

 cial in reducing the amount of repetitive effort by other investigators. Suit prototype fabrica- 

 tion details are not given extensively, because much of that information is proprietary. The 

 technical discussion includes research, design, development, prototype fabrication, training and 

 field engineering, evaluations, malfunction analysis, and recommendations for further work. 



RESEARCH 



Review of Physiological and Physical Concepts 



The approach to thermal protection taken during the program reported here was based in 

 part on the findings of Beckman, et al. [1, 2, 3]. 



Regional heat losses from the fingers, hands, and arms have been shown to result in an 

 increased reaction time, a decrease in tracking proficiency, a decrease in manual dexterity, 

 with a loss of tactile discrimination and kinesthetic sensation, as well as a decrease in muscle 

 strength (4). Severe body-heat loss can result in degrees of hypothermia, with various symptoms 

 such as amnesia, loss of contact with one's surroundings, pain, loss of voluntary motion, and 

 cardiac irregularities (5, 6). Factors which can be used to limit the loss of body heat during 

 cold water immersion are (1): 



1. Controlling the duration of the period of immersion 



