Coarse Buoyancy Compensator (CBC)

When Ranger NBV was first assembled and put in the water, it was far from neutrally buoyant. With no floatation or weight added to the body of the vehicle, (Table 2-8) it is about 150 lb. negative with a buoyancy moment along the x-axis of almost 200 ft-lb.

Table 2-8 Buoyancy and mass characteristics before CBC installation

To compensate for this large buoyancy offset, a static system of floatation and weight was added in the propulsion module, along with some weight in the front of the electronics module. This system is called the Coarse Buoyancy Compensator (CBC). The amount and location of the buoyancy and weight added was determined by a series of tests performed both on the deck and in the water. The data from these tests were entered into a spreadsheet, and the results determined iteratively. The results of the buoyancy calculations are shown below.

Table 2-9 CBC mass and buoyancy characteristics

These numbers were then used to create a design which would fit within the propulsion module. The approximate size, shape, and location of the added buoyancy is shown in Figure 2-10

Figure 2-10 Location of CBC within the Propulsion Module

The weight is attached to hard points on the surface of the added foam, and also in the front port side of the electronics module.