Undersea Vehicles and National Needs

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TABLE 2-1 Comparative Undersea Vehicle Capabilities

	DSVs	ROVs	AUVs
DEFINITION	Untethered, human-occupied, free-swimming, undersea vehicle	Tethered, self-propelled vehicle with direct real-time control	Untethered undersea vehicle, may be totally preprogrammed and equipped with decision aids to operate autonomously; or operation may be monitored and revised by control instructions transmitted by a data link.
DEPTH	Many to 1,000 m	Very many to 500 m	Several to 1,000 m
	Few to 3,000 m	Many to 2,000 m	Few to 3,000 m
	Very few to 6,000 m	Few to 3,000 m	Very few to 6,000 m
	One to 6,500 m	Few to 6,000 m
		One to 11,000 m
ENDURANCE
Time	Normally 8 hours, 24 to 72 hours max	Indefinite, depending on reliability and operator endurance	6 to 48 hours of propulsion May sit on bottom for extended periods
Range	< 50 km	Limited in distance from host ship by tether	350 km demonstrated; near-term potential 1,500 km, depending on energy source
PAYLOAD	1 to 3 people, 45 to 450 kg (100 to 1,000 lb); adaptable to tools and sensors	45 to 1,590 kg (100 to 2,000 lb); adaptable to tools and sensors	11 to 45 kg (25 to 100 lb); adaptable to measuring equipment, tools, and sensors
SUPPORT
Ship	Most DSVs require large ship support; ship size varies with DSV size	Depends on ROV size and mission requirements	Medium—depends on AUV size and mission requirements
Handling Systems	Depend on DSV size	Depends on ROV size	Similar to ROVs, depending on AUV size
Navigation Systems	Relative to seafloor or surface vessel	Relative to surface/seafloor	Seafloor and inertial navigation
STRENGTHS	Direct human observation and manipulation	Real-time feedback to operator, long endurance capability, low- cost per operating hour	Potential for automated operations, ability to operate with or without human command and without tether; minimum surface support
	Real-time feedback to controller
LIMITATIONS	Large size, weight, and cost due to manned requirements	Tether cable potentially limits maneuverability and range	Energy supply
			Bandwidth of data link
	Limited mission time		Capacity of internal recorders
	Potential personal hazards		Limited work function complexity

mapping and surveying operations. As with other systems, advances in propulsion, energy storage, and manipulators will contribute to DSV utility and may even reduce their cost. Developments incorporating innovative uses of materials have already reduced the size and weight of the next generation of DSVs, and a system designed to bring a single pilot to the deepest part of the ocean is in progress (Hawkes and Ballou, 1990; Broad, 1993).

REMOTELY OPERATED VEHICLES

ROVs are by far the most common type of undersea vehicle; more than 1,000 ROVs have been built since their introduction in the 1960s. ROVs connect to a surface vessel or platform by a tether that carries power and control signals and feedback data from the vehicle. Originally developed for the military, ROV technology was further developed by the civil sector in the early 1970s, when private firms developed ROVs in response to the needs of the offshore oil industry. ROVs were one factor that enabled the offshore industry to move beyond diver depth range. The results were reliable platforms serving a broad commercial market, with some technology transfer back to the military (McFarlane, 1987). ROVs continue to be used reliably in the offshore industry, and innovations in operational techniques and tool packages are expanding the scope of tasks these vehicles can perform (Langrock et al., 1992; Sucato, 1993). Nevertheless, ROVs are vertically operating systems that require significant surface support with attendant costs.

ROV manufacturing has been a highly competitive business. After attempts by several companies to compete in the rapidly growing offshore market of the 1970s, only one company, Perry Tritech, Inc., remains in the United States that builds full-size work platforms for the offshore industry. Worldwide, there probably are no more than five companies that have built more than one large ROV system. In the area of the smaller, low-cost ROV systems, a U.S. company, Deep Ocean Engineering, is the largest supplier among eight companies in the world that are in serial production of these vehicles.

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