The Rainbowfish class bathyscaphe is a Chinese deep submergence vehicle under development in 2015 and originally scheduled to enter service in 2019. The Rainbowfish is a second generation bathyscaphe designed to be able to dive to a depth of 11 km, effectively covering 100% of the oceanic floor. The general designer is Mr. Cui Weicheng (崔维成), who was the first deputy general designer of the first generation bathyscaphes Sea Pole and Jiaolong. Unlike other Chinese deep submergence vehicles developed earlier, the Rainbowfish was developed under a new business model, raising capital from private enterprise.
The Rainbowfish class bathyscaphe is designed to have an endurance of ten hours, with ascent and descent each taking two hours, thus leaving a total of six hours of endurance to conduct research at the sea floor. The bathyscaphe is powered by Lithium-ion batteries and the flotation material is developed by Chinese firm China Haohua Chemical Group, with development successfully completed at the end of 2014. Most of the subsystems of Rainbowfish bathyscaphe such as underwater electric motor, high pressure seawater pump and integrated propulsion system are developed from earlier Jiaolong bathyscaphe. Although many subsystems can be 100% manufactured in China, there are some critical subsystems that had to be manufactured abroad due to the limitation of Chinese industrial and technical bottleneck, despite being indigenously designed in China. One of such subsystem is the capsule housing the crew. During the design stage of the development, it was discovered that the TC4 titanium alloy used on earlier Sea Pole and Jiaolong bathyscaphe are not good candidate for Rainbowfish, because the thickness required would be 110 mm, which would be extremely difficult to build. As a result, alternative material is needed, and the design settled on Martensitic stainless steel. However, existing Chinese capability can only provide the manufacture of capsule capable of diving to a maximum depth of 4500 meter, so foreign assistance was needed with Finnish firm selected due to Finnish experience in construction of deep submergence vehicles. Finnish experts concluded that the Chinese design was feasible after thorough review, both sides are finalizing the deal in the mid 2015, with the completion of the capsule scheduled in 2016. Plans are mde to have future capsules manufactured in China by increasing domestic Chinese capability with governmental support. The mother ship carrying Rainbowfish bathyscaphe will be Chinese oceanographic research ship Zhang Jian.
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