In the modern world, performing oceanological research and underwater technological operations is impossible without using autonomous and remotely operated underwater vehicles. However, each of these types of vehicles has disadvantages limiting their application and allowing only narrow-profile tasks to be performed. To solve this problem, it is proposed to use a hybrid underwater robotic complex consisting of an autonomous and remote-controlled vehicles connected with a cable. The functionality of the proposed hybrid complex is determined. The results of the analysis of the mathematical models of hybrid complex operation in the modes of joint movement and towing are presented. Due to the restrictions imposed on the remotely controlled underwater vehicle and the cable between the vehicles, the speed of the hybrid underwater robotic complex is about 1 m/s in the joint motion mode and about 2 m/s in the towing mode. It is recommended to tow a remote-controlled underwater vehicle on a short cable length when the autonomous uninhabited underwater vehicle is submerged. In addition, it is necessary to adjust the cable length between the devices.

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The adaptation of waterjet cutting technology to underwater working conditions will allow solving various tasks when performing underwater technological operations, including maintenance of man-made hazardous objects. The implementation of such technology under water is possible with the application of mobile installations having low power, which imposes certain restrictions on its use. A method for improving the efficiency of mobile installations implementing underwater waterjet cutting is proposed. The method is based on the use of a built-up jet-forming path consisting of a diamond nozzle, an additional transition tube and a standard focusing tube. The structural externality of the diamond nozzle is given. A physical and mathematical model of the process of forming a high-speed jet which implements the technology of underwater hydro- or waterjet cutting, when the flow of a suspension under pressure passes through the jet-forming path of the proposed design, is described. Using calculations based on the developed model and results of field experiments, the effect of the structural element parameters of the built-up jet-forming path on the output characteristics of the formed jet flow is determined. The possibilities of applying such a design for controlling the output characteristics of the formed high-speed jet are assessed and the practicability of its use is indicated.

A possibility for the creation of a design and technology for manufacturing focal tubes for underwa-ter material hydro-abrasive jet cutting by means of ex-perimental development both existing hydro-jet nozzles and pre-production models of hydro-jet ones, focal tubes and designs of cutting blocks is analyzed. According to the research results at the given stage it is possible to say that the inner profile of a hy-dro-jet nozzle and also a cutting block design optimum from the point of view of productivity are defined. Impossibility to use already existing focal tubes used in the technology of material hydro-abrasive jet cutting for the technology of underwater hydro-abrasive jet cutting (UHAC) in view of the non-assurance of the specified power parameters of a hy-dro-abrasive jet is revealed. There is developed a me-thodical plan for the fulfillment of investigations pro-viding searches of ways to fulfill requirements made to UHAC.

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