17 



for ordinance (mines) inspection and neutralization. PAP- 104 is battery- 

 powered and carries an explosive weight of 100kg (220 lbs) which is released 

 by the operator. Guidance of the vehicle to the ordinance is performed by 

 the support ship's mine-hunting sonar. Detonation of the charge is possible 

 15 minutes after its release and for 30 minutes thereafter. After 30 minutes 

 the igniters are mechanically isolated from the explosive and firing becomes 

 impossible. PAP-104 is propelled by two electric motors with variable pitch 

 propellers. Control in the vertical is by a guiderope which holds the vehicle 

 at near-constant altitude off the bottom. Operations in currents of 4 knots 

 and depths of 100m are attainable, operational duration is 20 minutes. 



Unlike other ROVs , PAP-104 does not pull its tether through the water, instead, 

 a small diameter cable (spooled around a reel) is paid out from the vehicle 

 as it progresses through the water. In this manner cable drag is avoided. 

 Surface components consist of a main control console and a TV monitor. 



At present there are 28 industrial, government and academic manufacturers 

 of ROVs. Approximately 140 vehicles will have been constructed by 1980 

 and at least 100 are now operating (Figure 2.1). The following sub-sections 

 deal only with operational vehicles and those under construction - or funded 

 for construction. Table 2.1 presents the salient characteristics of these 

 vehicles and Table 2.2 presents the vehicles in order of increasing depth 

 capability and the organizations which own and operate specific vehicles. 



2.1.1 Structure 



The majority of vehicle manufacturers (19) produce a vehicle which is rectangular 

 in shape and composed of an open metallic (usually aluminum) framework. 

 The framework serves the function of enclosing, supporting and protecting 

 the vehicle components (thruster, junction boxes, CCTV, lights, etc.). 

 Frequently the framework members are square and rectangular rather than 

 tubular to facilitate attachment of components. Variations from the open 

 aluminum framework are vehicles which have faired the framework entirely 

 with either fiberglass or metal. The vehicle shape in these instances are 

 torpedo-like, disc-like or spherical. 



Vehicle size varies widely and ranges from the basketball-sized RCV-225 

 (0.17m-^) to the automobile-sized ERIC II (27m-^) . Approximately 46 percent 

 are less than Im-^, Figure 2. 2 graphically portrays vehicle size distribution. 



Vehicle dry v^eight is as variable as is vehicle size, and ranges from 80kg 

 to 5,000kg (176 to 11,023 lbs) (Figure2.3). Most (66 percent) are less than 

 500kg (1,102 lbs) . 



2.1.2 Buoyancy 



All ROVs have slight positive buoyancy when submerged. In all but a few 

 instances the buoyancy is supplied by syntactic foam blocks fixed to the top 

 of the framework. Alternatives to syntactic foam take the shape of small, 

 hollow plastic spheres (fishing floats) which are much less expensive, but 

 limited in depth capability. To overcome the positive buoyancy the vertical 

 thrusters are employed to thrust the vehicle downward. The propeller wash, 

 being directed upward, does not disturb the bottom sediments and obscure 

 visibility. Variable buoyancy tanks (blown free of water by compressed air) 



