Alvin is capable of the following:
- Operating at any depth from the surface to 6,500 meters (21,325 ft.) at speeds of 0-3.4 km/h (0-2.0 knots), and remaining submerged for approximately 10 hours (up to 72 hours under emergency conditions)
- Carrying one or two observers and various internal and/or external instrumentation and tools
- Maneuvering within areas of rugged bottom topography
- Hovering at neutral buoyancy in mid-water and/or resting on the bottom to perform scientific and engineering tasks, including still and video photography
- Using its manipulators and sample basket to deploy various scientific tools and to collect samples
- Providing a 270° observer viewing capability with overlapping fields of view through five acrylic viewports, three looking forward and one to each side
- Providing electric and hydraulic power plus data logging capabilities for scientific instruments and equipment
- Launch and recovery of the vehicle in weather up to and including Sea State 4
- Utilizing symmetrical and redundant electrical and command/control systems to maximize reliability
Alvin's 1,500 lb. total payload includes the pilot, two passengers, descent weights, variable ballast water, science payload and the sample basket. The empty sample basket weighs approximately 105 lbs. in water. The science payload includes user equipment and samples taken during the dive. This load may be divided between internally and externally loaded equipment, subject to some restrictions. Internally mounted equipment must fit in a standard 19-inch rack. All equipment entering the sphere must pass through a 19-inch circular opening so as to fit through the hatch with adequate clearance. With advance planning, the user's portion of the payload can be increased by the removal of one or both manipulators, the science basket, or one observer.
Normal dive duration varies from six to ten hours, but this time may be reduced by excessive 120V or 24V power usage. The primary direct consumers of the 120V power are the propulsion and hydraulic systems and external lights. High speed or current-fighting transits and excessive use of the lights represent loads on the 120V system that might be avoidable with proper dive planning. The 24V power, derived from the 120V batteries, supplies all services within the sphere as well as the control systems, instruments and the computers. Judicious use of other instruments such as the sonar and underwater telephone can result in significant power savings and can thus prolong dive time.
During any given dive, the percentage of time actually spent on the bottom or at desired depths depends on the amount of time it takes to travel to and from that depth. We generally transit the water column at an average of ~40 meters per minute, so calculating total transit duration with 25 minutes for every 1,000 meters of depth yields a rough estimate of total working time on the bottom.
Dive duration may also be affected by the need to perform launch and recovery operations during daylight hours in all but the best of weather conditions. Additionally, deteriorating weather conditions may require the early termination of a dive, as may any malfunction which could affect safety or the continuation of operations. The Expedition Leader, with advice from the Pilot and Surface Controller, is responsible for making decisions based on these factors.
Personnel on any given dive are normally one pilot and two scientific observers. In certain cases, such as where bottom conditions are unknown or where extremely rugged terrain and high currents are anticipated, the Expedition Leader may choose to assign two pilots to the dive. Also, the user may elect to assign only one observer to a dive in order to utilize the extra payload capacity for other purposes.
Alvin Group personnel are prepared to assist scientists with integration of approved experimental or custom sensors and development of new sampling techniques. Some amount of development, customization, and/or integration happens before every cruise, and while more complicated changes or additions will require advance planning, we are happy to pursue any of these avenues with the prospective investigator.
Any potential user of the submersible must carefully consider which aspects of the proposed research require use of the submersible and how it can best be utilized to realize dive objectives. Frequently, extensive investigations are required prior to an Alvin cruise in order to ensure the availability of adequate information for conducting an efficient diving program. Additionally, the capabilities of Atlantis beyond those of supporting the submersible should be considered in order to maximize the value of the cruise and to minimize the effect of dive time lost due to unforeseen problems.
Alvin has proven most effective when used in a well-planned, coordinated program, where its abilities to observe directly, photograph selectively, and sample in situ are complemented by other research techniques.