A Progress Report On The
Design Study For An Alvin Replacement
The basic Alvin design
is over 36 years old and although it has been incrementally modified and
improved, the scope of these improvements has always remained constrained by
the submersibles basic design. These
constraints affect the operation (such as ascent/descent speeds) and
maintainability (such as battery removal).
The Deep Submergence Group of Woods Hole Oceanographic Institution
(WHOI) recently completed an evaluation of the available options for improving
Alvins capabilities, including those resulting from the availability of the
DSV Sea Cliff. The conclusion
was that building a new submersible from the keel up would provide the best
means for the U.S. to regain the 6000 meter submersible capability previously
provided by the U.S. Navy operated Sea Cliff, and to achieve significant
improvements in other areas of importance for a submersible dedicated to
scientific research.
As part of the feasibility
study for building a new research submersible, NSF and NOAA funded the National Deep Submergence Facility
(NDSF) to undertake a concept development.
This first step in the process of constructing a new Alvin will convert
rough requirements and initial concepts into a detailed engineering
specification. This specification
defines the submersible and its sub-systems in sufficient detail to allow
development of the detailed design required for construction. The performance requirements and principal
system characteristics will be defined based upon past and current input from
the science community and the collective experience of WHOI NDSF
personnel. Optimal design concepts will
be chosen from the identified alternatives and specified as necessary to insure
meeting the cost and performance goals.
Science input to this process is being implemented through a special
advisory committee formed in collaboration with the Deep Submergence Science
Committee (DeSSC) so that science requirements will be implemented into the
design.
The planned capabilities and
features of a new Alvin will include:
1. Improved Science Capabilities
·
Increased Bottom Time - This would be achieved through improved
hydrodynamics and possibly increased descent weight. Bottom times could be increased by as much as ~2 hours at
mid-ocean ridge depths.
·
Increased Energy
Capacity - A lighter buoyancy material will allow for larger energy
payload. Additionally switching to NiCd
or Lithium based batteries or fuel cells will further increase capacity.
·
Improved Fields of
View
- A new personnel sphere design will allow moving the observer viewports
forward and overlapping their viewing area with that of the pilot. The views from Alvins ports do not overlap,
a long-standing deficiency in the original Alvin design; correcting this will
provide better observational capabilities and will improve pilot/observer
synergy and efficiency of operations.
·
Increased Access to
the Seafloor - The actual depth capability of the new
submersible will be based on engineering and cost trade-offs with the
underlying requirements of obtaining a vehicle having the general size, weight
and performance characteristics that have made Alvin an effective science tool
over the years.
·
Improved Interior
Ergonomics - The ergonomics in Alvin are far from optimal, especially when
compared to the newer Russian, French, and Japanese 6000+ meters
submersibles. Improved viewport access
and general interior arrangement of the new Alvin will be achieved by increasing
the personnel sphere interior diameter (from 78" to 83") and by
relocating the viewports.
·
Increased Interior
Electronics and Science Payload - This will be achieved by increasing the
interior diameter and will result in an increase of 18% or 27 cubic feet
compared to Alvin.
·
Reduced Physical and
Chemical Disturbances to Science Study Areas - This will be accomplished by
the design of an ascent/descent weight system using seawater instead of the
steel weights currently used. For
simplicity this system could be combined with a variable ballast and trim
system. This improvement is deemed
particularly important for science missions that will be required to install
and maintain seafloor observatories where repeat dives to specific areas are
required.
2. Improved Operational and Maintenance
Features - The following
listing provides the key technical areas where improvements will lead to more
efficient and cost-effective operational maintenance and increased reliability
with the attendant direct benefits to science productivity.
·
Improved Battery
Access - The current Alvin system requires flat seas to change or
inspect a battery. Typically, if
repairs are required, it means the ship must return to port which can result in
lost dives and science. A new battery
installation and handling system will be designed that will allow inspection
and replacement under normal at-sea working conditions.
·
Reduction in Cabling and Number of
Personnel Sphere Penetrators -
Aggressive use of distributed control systems, and fiber optic penetrators will
reduce the numbers of cables and penetrators (points of failure), in addition
to increasing through-hull bandwidth to take advantage of state-of-the-art
imaging systems and recording formats.
·
Elimination of
Hazards Associated with a Mercury Trim System - The replacement of the Hg
trim system by a water based system integrated with the variable ballast system
will eliminate both the potential health threat to the Alvin technicians and
the material hazard associated with carrying Hg on a ship with copper alloyed
piping.
The Concept Development phase
is a combined effort of the Deep Submergence Group at WHOI, the deep
submergence community, and several outside engineering contractors. The final product will be a package ready
for obtaining bids (Request for Proposals) for the detailed design and
construction of the submersible. The
following areas are included in this phase:
a. Community
Input -
A New Alvin Design Advisory Committee
(NADAC) has been formed to provide additional input and review from the deep
submergence science community. They
have formulated the functional mission requirements, are currently reviewing
functional specifications and will be reviewing viewport issues and science
equipment layout in the future.
b. Certification
-
A determination will be made concerning
the certification agency and therefore construction rules for the new
submersible. U.S. Navy and American
Bureau of Shipping (ABS) are viable alternatives. This is currently being studied by the contractors as well as the
Naval Sea Systems Command.
c. Viewport
Number, Location and Sizing -
This matter is being studied to
determine if better arrangements, larger viewports, and/or more viewports might
be feasible and desirable. Modeling and
eventually a full scale mockup will be used to assist in this area as well as
the ergonomics of the interior arrangement.
d. Engineering
Support -
This will include a refinement of
requirements based on a revised set of functional specifications, a detailed
engineering feasibility study of personnel sphere construction based on
selected construction rules as well as viewport window arrangements, a power
source review, drag studies, vehicle and system level designs, and development
of a bid package.
At the completion of the
Concept Development phase we expect that the following will have been
accomplished:
·
The operational depth
will have been established based upon available buoyancy materials, hull
structural considerations, and auxiliary design system issues. Present information supports a goal of 6500
meters.
·
The science requirements
will have been fully integrated into the conceptual design
·
The feasibility of the
functional specifications will have been demonstrated
·
A system level
conceptual design will have been completed
·
The cost estimate
updated
·
A detailed package will
be ready for submission to contractors as a Request for Proposals for the
design and construction of a new Alvin.
This phase is the next step
required to assure that the science community has a new Alvin within 5
years. It will be followed by the
detailed design and construction phase which will result in a new submersible
with increased scientific and operational capabilities including greatly
improved access to the majority of the abyssal regions of the worlds oceans.
Alvin users and potential users
are invited to submit recommendations for the new Alvin to the NADAC via rbrown@whoi.edu
.