Technology and Operations
This forum is for discussing technological & operational matters pertaining to U-boats.
Re: Thermal Layers
Posted by:
kurt
()
Date: July 12, 2004 10:47PM
Dion / Dan:
The thermal layer is just a sharp transition in water temperature: warmer water on top, cooler, deep ocean water beneath. The colder water is denser. This sharp layer between the two density levels reflects sound (such as sonar) very well.
Since the thermal layer reflects active sonar, and generally confuses the acoustic environment, a submarine that went below the thermal layer becomes very difficult to detect, and generally could escape.
But the depth that the thermal layer occurs varies in different locals and oceans, and varied from time to time. In the Pacific, it was generally less than 400 ft deep, within diving distance of US subs. They (eventually) had installed a bathythermograph, a strip chart readout of the outside water temperature. A sub, while diving, could easily see the sharp temperature drop. US Subs, in the later war years, often droped down to find the thermocline depth during a submerged approach. After the attack they simply dived below the thrmocline and snuck away.
In the North Atlantic, the thermocline was generally much deeper, often below 600 ft, below the normal operating depth of U-boats. This inhibited its routine tactical use the way US subs learned to do.
The instrumentation for detecting the thermocline was much more primitive on German U-boats than US subs. Instead of a direct strip chart readout of an outside thermocouple, U-boats had to draw external water and measure it with a thermometer - a much slower and less accurate process. This probably reflected the lack of extensive tactical use of the themrocline in the U-boat service.
Hope this helps.
Kurt
The thermal layer is just a sharp transition in water temperature: warmer water on top, cooler, deep ocean water beneath. The colder water is denser. This sharp layer between the two density levels reflects sound (such as sonar) very well.
Since the thermal layer reflects active sonar, and generally confuses the acoustic environment, a submarine that went below the thermal layer becomes very difficult to detect, and generally could escape.
But the depth that the thermal layer occurs varies in different locals and oceans, and varied from time to time. In the Pacific, it was generally less than 400 ft deep, within diving distance of US subs. They (eventually) had installed a bathythermograph, a strip chart readout of the outside water temperature. A sub, while diving, could easily see the sharp temperature drop. US Subs, in the later war years, often droped down to find the thermocline depth during a submerged approach. After the attack they simply dived below the thrmocline and snuck away.
In the North Atlantic, the thermocline was generally much deeper, often below 600 ft, below the normal operating depth of U-boats. This inhibited its routine tactical use the way US subs learned to do.
The instrumentation for detecting the thermocline was much more primitive on German U-boats than US subs. Instead of a direct strip chart readout of an outside thermocouple, U-boats had to draw external water and measure it with a thermometer - a much slower and less accurate process. This probably reflected the lack of extensive tactical use of the themrocline in the U-boat service.
Hope this helps.
Kurt
