Alvin is capable of the following:
- Operating at any depth from the surface to 4,500 meters (14,764
ft.) at speeds of 0-3.4 km/h (0-2.0 knots), and remaining submerged for
approximately 10 hours (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 storage basket to deploy various scientific tools and to collect samples.
- Providing a limited amount of electric and hydraulic power plus data logging capabilities for instruments and equipment not normally part of the submersible.
Alvin’s 1,500 lb. total payload includes the pilot, two passengers, ascent weights, variable ballast water, science payload and the science basket. The empty science 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 panel 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 26V power usage. The primary direct consumers of the 120V power are the propulsion system 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 26V 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 CTFM 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 upon the amount of time it takes to travel to and from that depth. As a rule of thumb subtract 1.25 hours from the total dive time for each 1,000 meters of depth. The difference will be a rough estimate of total working time on the bottom (i.e. for a ten-hour dive to 4,500 meters, 5.6 hours will be spent in vertical transits leaving 4.4 hours of “bottom time”).
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 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. Finally, on one dive out of every five during each cruise, a pilot-trainee or other person designated by the Alvin Group must fill one of the two observer positions, leaving only one space for a science user. Although there is flexibility in deciding which specific dives will be of this type, it is recommended that the pilot training dives not be postponed to the end of the cruise, but rather, that science program planning allow them to be completed routinely on every fifth dive.
The potential user 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. Generally, Alvin should be used to accomplish those tasks which cannot be accomplished with other available oceanographic tools.
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. Due to its slow speed and limited power, Alvin is not an effective vehicle for large area searches and surveys.