Open-Ocean Cargo Transfer to and from a Sea Base
As indicated in Chapter 1 of this report, the Sea Basing concept has not been stated with sufficient definition to allow formal publication of the required capabilities for cargo handling and at-sea transfer of loads that must be incorporated into the selected platform or platforms that will constitute the sea base. On the basis of worldwide data provided by the Oceanographer of the Navy on the frequency of occurrence of various sea-state conditions, the Defense Science Board (DSB) report on Sea Basing recommended that an open-ocean cargo-transfer capability (to and from a sea base), in conditions up to 3 and 4 Sea States should be achieved.1 This goal was considered desirable so that the percentage of time during which operations might be limited by unfavorable environmental conditions will be relatively small. The committee believes the DSB sea-state performance goal to be reasonable. The DSB report implies that the types of cargo that a sea base should be able to receive or disperse in such sea states would include 20-ft-equivalent unit (TEU) shipping containers, outsized/heavy (greater than 40,000 lb) equipment, pallets, and liquids (fuels and/or water).
To some extent, current commercial and military capabilities permit such transfers in nonport environments during times of relatively benign sea states. As
an example, the ship-to-ship transfer of TEUs in nonbenign conditions is difficult, because in commercial practice the TEUs must be stored within guide rails that leave little clearance even for minor deviations from the vertical caused by pendulous motion resulting from the pitch or roll of the vessels executing the transfer. The problems of cargo transfer at sea would be immensely simplified if all of the Services adopted common joint pallet and container sizes. While 20 or 40 ft International Organization for Standardization (ISO) containers will normally be employed for supplying or resupplying the sea base, containers that are smaller than the commercial ISO containers are generally needed by the troops fighting in the objective area. The committee believes that the Joint Modular Inter-Modal Container (JMIC) program is an important initiative that, if successful, will alleviate many of the problems currently encountered in this regard. A number of JMIC containers can be arranged and locked together into 20 or 40 ft ISO-container-size blocks for transport in commercial containerships.
The offshore construction industry has lifted and transferred loads of 5,000 tons or more at sea, using built-for-the-purpose equipment. However, such activities are infrequent and have generally taken place during periods of benign sea states. Offshore resupply boats (mud boats) operate routinely in Sea State 3 or even higher sea-state conditions. However, to the best of the committee’s knowledge and experience, mud boats are not used for the transfer of loads comparable in weight to militarily significant loads (e.g., 70 ton tanks) during periods of high sea state. Also, during mud boat operations, one of the platforms involved is fixed in space, making the transfer easier than it is when both ships involved are subject to random uncorrelated motions.
Various studies of the Sea Basing concept have considered solutions to the open-ocean cargo-transfer problem that include some combination of the use of the following:
Vertical-lift or short-takeoff-and-landing (STOL) aircraft,
Stabilized cranes for skin-to-skin transfers,
Mobile landing platforms (MLPs) (float-on/float-off heavy-lift ships),
Wire line and hose transfers,
Integrated landing platforms (ILPs),
Roll-on/roll-off ramps, and
Transfers within a well deck into air cushion vehicles (landing crafts, air cushion (LCAC) or LCAC-experimental (X)).
Each of the techniques in the foregoing list is proven technology in commercial and/or military cargo-transfer operations. All of them have significant performance limitations, and the limitations in their performance are correlated with the attributes of the ships and connector platforms involved as well as with the attributes of the sea states.
The importance of intraship cargo handling on the sea base ships should be emphasized. Cargo loads brought to the sea base must be broken down and reconstituted into tailored packages for transfer to the troops in the objective area. Marine shipboard cargo-handling systems, including the processes of strike-down, stowage, strike-up, breakout, repackaging, and so on, should be developed with the ability to sustain the required cargo flow rates. Full-scale at-sea testing will be required to develop the required systems.
Ideally, the selected platform design for a sea base should incorporate inherent capabilities to accomplish the following:
Provide for the rapid transfer of large tonnages of cargo both from arbitrarily configured container ships and tankers and from those designed for the purposes of naval vessels (e.g., AO, AKE, AOE,2 and so on);
Provide a high strike-down rate for received cargo;
Provide rapid and effective transfer of equipment to a variety of sea connector designs (e.g., LCAC, LCAC-X, beachable high-speed connector (B-HSC), heavy-lift LCAC (HLLCAC), proposed amphibious helicopter assault vessel, high-speed vessel (HSV)/theater support vessel (TSV), and so on);
Allow the selective retrieval of any specific item of stored equipment;
Keep position in conditions up to Sea State 4 and ballast down sufficiently to reduce roll to a small fraction of a degree;
Transport and provide operational support for non-self-deployable heavylift vertical-takeoff-and-landing (VTOL) aircraft (including Army variants); and
Accommodate the landing and takeoff of STOL aircraft with payloads greater than 20,000 lb.
Any assessment of the technology that will be necessary to achieve the desired cargo-transfer and -handling performance goals for a sea base is inherently dependent on the assumptions that are made concerning the design and attributes of the sea base, the sea-base-to-shore connectors, and the logistic resupply ships and aircraft that will service the sea base. Critical design factors will include such things as the following:
Hull size and shapes of the sea base, the sea-base-to-shore connector vessels, and the logistic resupply vessels that service the sea base;
The availability and effectiveness of roll-mitigation systems;
An ability to operate in deeply ballasted conditions that minimize roll, pitch, and heave motions;
Deck designs, including deck strength, the location of obstructions to STOL operations, the availability of electromagnetic catapults,3 and so on;
Elevator-lift capacity and internal cargo-handling and -management systems that will permit the rapid retrieval of any stored item of equipment;
Dynamic position-keeping capabilities; and
The cargo-transfer methods that are adopted (dry wells, floating platforms, outboard elevators, and so on).
The committee notes that the designs currently proposed for a sea base or for the Maritime Prepositioning Force (Future) (MPF(F)) do not incorporate all of these capabilities or attributes. The interdependencies between the core element of the sea base, the MPF(F), the supply connectors, and the shore-bound connectors must be emphasized. The interfaces between these two categories of connectors and the sea base itself (i.e., the cargo-transfer techniques to be employed) will have a major influence on the MPF(F) configurations as well as on the designs of the several connectors. The MPF(F) design should not be frozen until the required cargo flow rates have been defined and the cargo-transfer methods to be employed have been selected and demonstrated in full-scale, at-sea tests in demanding environments. As an example, if either a stern elevator or a stern ramp is required for the MPF(F), its inclusion will have a major effect on the ship’s overall general arrangement.
CURRENT STATUS OF THE SCIENCE AND TECHNOLOGY BASE AND TECHNOLOGY GAPS
Although limited to lower sea states (below Sea State 3), most of the cargo-transfer capabilities desired for a sea base exist in commercial and/or naval practice. The committee believes that the extension of current open-ocean (nonport) cargo-transfer capabilities to use in higher sea states may be viewed as a number of difficult (but tractable) engineering problems that can be resolved with the application of extant technology and engineering techniques. Few of the current constraints require an extensive science and technology (S&T) investment for resolution. Almost the entire current Navy S&T or research and development (R&D) effort that is oriented toward the achievement of at-sea cargo-transfer capability in higher sea states is vectored toward inclusion in the MPF(F) design. Unfortunately, design efforts for the MPF(F) do not assume that such Navy S&T or R&D efforts will be successful prior to the preconstruction design freeze for the MPF(F). Vaguely stated plans exist for retrofitting or for inserting improved cargo-handling capabilities into current or future MPF(F) hulls.
The committee is concerned that no integrated development plan seems to exist that supports an R&D effort specifically designed to provide high-sea-state cargo-transfer capabilities for the MPF(F). The following subsections present the committee’s assessment of current cargo-handling capabilities and its prognosis for the eventual achievement of significantly improved capabilities in either an MPF(F) or a sea base.
Aviation is a key element in the array of cargo-transfer mechanisms from the sea base to shore, whether to a beachhead or to forces maneuvering against an inland objective. A detailed discussion of the technical issues in developing heavy-lift aircraft to transfer cargos on the order of 20 to 23 tons from the sea base to shore is presented in Chapter 2. As indicated in that chapter, the technical requirements of range and payload to be moved even from a very large ship will require an aircraft having some kind of power-assisted takeoff and the capability for vertical landing.
This chapter will explore the technical problems of transferring cargo among ships of the sea base, and from the sea base to connector ships that will take the cargo to shore.
Stabilized Cranes for Skin-to-Skin Transfers
Stabilized cranes for skin-to-skin cargo transfers exist, but their use is generally limited to benign sea-state conditions. In commercial practice, when ultralarge container ships cannot enter a port because their draft exceeds the controlling depth of a harbor, a sheltered area is selected outside of the harbor and containers are transferred to locally available lighters or barges.
Although commercial crane technology is highly developed, limitations exist in its use in skin-to-skin transfers. Ships with widely different hull shapes or superstructure designs cannot come alongside each other in high-sea or swell states even when significant fenderage capability is available. In some situations, a two-step process is used to solve the problem of ship-to-ship transfers between incompatible hull forms. A large, heavily fendered barge is placed between the two incompatible hulls, and the cargo is transferred from one vessel to the barge and then from the barge to the second vessel.
The problems of crane design for open-ocean skin-to-skin transfers are substantially mitigated if either or both vessels involved have low pitch, roll, and heave motions as a result of their displacement (ballasted draft) and/or an active roll-mitigation system.
The cranes used for such purposes typically have a 75 ft reach for a 56,000 lb load and are 6 degrees-of-freedom (6-DOF) controlled platforms that actively
compensate for movement of alongside platforms. Knuckle-booms with fixed-location pivoting bases are frequently employed. The design of the cranes incorporates active/passive compensation using hydraulic cylinders in the boom and in the knuckle and boom. The relative motion of the alongside platform is sensed, and predictions are made of future (short-term) platform motions so that the timing of cargo delivery can be optimized. In more sophisticated designs, dynamically tensioned guy wires are attached to the cargo in transit so that pendulous motions are mitigated.
The Office of Naval Research (ONR) has supported an S&T program in this area for a number of years. No programmatic roadmap exists for an end-item deliverable from this effort. The ONR should develop a programmatic roadmap for stabilized cranes for skin-to-skin transfers. The limiting factors appear to be the following:
The need to develop an ability to provide a precise, short-term prediction of the motions of a receiving platform relative to the motions of the delivery platform, and
The need to improve the response time of guy wire tensioning equipment designed to damp the pendulous motions of cargo being transferred.
Wire Line Transfers
The Navy has had a ship-to-ship wire line transfer capability for many decades. The capability to perform such transfers is limited to ships that carry the necessary equipment. In practice, this generally implies that wire line transfers can be accomplished between U.S. Navy (USN) ships and U.S. naval ships (USNSs; USNSs are civilian manned and in service), but not between arbitrarily selected commercial ships and USN/USNS ships. The committee presumes that any design for a sea base would incorporate the necessary capabilities for ship-to-sea-base wire line transfers.
Current Navy wire line transfers are limited to pallet loads of about 5,700 lb. Equipment limitations such as king post strength, cable strength, the response time of tensioning engines, and the torque of available hauling engines determine the limits to the weights that can be transferred.
A funded program exists to provide increased (about 14,000 lb) wire line weight-transfer capabilities in time for incorporation in the MPF(F) design. No technology problems are anticipated that would cause significant delay in the development of this capability.
Although a more robust design for a wire line transfer capability can probably be available as early as FY 2008, this enhanced capability is unlikely to be retrofitted into all operational USN/USNS vessels in fewer than 12 years. Thus, a
full operational capability (FOC) for an enhanced wire line transfer capability is unlikely to occur prior to 2020.
Although wire line transfer capabilities exist on current USN/USNS vessels, it is not clear that all of the connectors being considered for use with the sea base will have a wire line connector capability. Certainly, current LCACs do not have such a capability, nor do the current TSV/HSV designs. Cargo will be transferred to such connectors by other means.
Ship-to-ship transfer of fuel and in special cases other liquids has been accomplished routinely in both commercial and naval practice for many decades. Deep-draft commercial tankers normally are required to off-load some of their cargo to barges or transfer shuttles before entering harbors with limited controlling depths. Although this is not a standard Navy practice, the availability of fuel-transfer connectors might be an important adjunct to the sea base concept of operations.
The Navy’s capability to accomplish underway refueling is excellent, and as far as is known, no S&T or R&D effort exists to improve the Navy’s open-ocean fuel-transfer capabilities. Ship-to-shore fuel- and water-transfer requirements have not been defined and appear to be a limiting factor in some scenarios.
The major deficiency in liquid-transfer capabilities resides in the area of direct ship-to-shore transfer of liquids such as water. The Joint Logistics Over the Shore (JLOTS) program has dealt with the problem. The operational equipment needed for JLOTS liquid transfers is limited to a 3 to 4 mile range. No R&D program exists that is designed to produce equipment that will enable a greater standoff delivery range. As currently conceived, JLOTS will not be applicable to the sea base concept of operations unless the current JLOTS capability is incorporated into the design of a system that allows the routine transfer of liquids from a sea base to the shore connector. To the committee’s knowledge, no program in support of the development of such a capability exists.
The sea-base-to-shore transfer of water is not nearly as much of a problem as the transfer of fuels. Water can be transferred to forces ashore by vertical lift either in bladders or as shrink-wrapped pallets of plastic water bottles. Furthermore, mobile ground forces generally have some autonomous water purification capabilities (although such capabilities might be of limited value in a desert environment).
Roll-on/roll-off (RO/RO) ramps are in widespread naval and commercial use. The Navy’s large, medium-speed roll on/roll off (LMSR)-size ships have
both stern and side ramps that allow wheeled and tracked vehicles to be driven from the LMSR. Current ramp designs are limited to pierside or causeway employment.
The use of RO/RO vessels is generally limited to major ports with a substantial pierside infrastructure that can accommodate deep-draft vessels. The number of such ports in the world is small relative to the total number of ports that might exist in future areas of military operations. In consideration of this limitation, the U.S. Army has maintained a program leading to the development of a deployable, floating causeway that can mate up with a deep-draft RO/RO ship. The problems involved in the development of such a capability are formidable. If the Army’s development of this capability is successful, the value of RO/RO vessels as sea base connectors would be greatly enhanced, since their utility would not be limited to a relatively small number of ports.
Although the concept of roll-on/roll-off ramps is being considered for possible future inclusion in the MPF(F), a decision has been made to defer engineering studies of ramp configurations until 2008. In effect, this decision means that RO/RO capabilities will not be incorporated in the first flight of the MPF(F).
To some degree, the issue discussed above highlights a relatively fundamental difference between an MPF(F) and a sea base. Although a sea base could be loaded and unloaded alongside a pier or causeway, its primary design criteria will be an ability to transfer cargo to and from connector and resupply ships in the open ocean. Although the MPF(F) ships will certainly have a capability to transfer cargo to and from connectors and resupply ships in the open ocean, the first flight of the MPF(F) will be a relatively conventional vessel, possessing some open-ocean, cargo-transfer capabilities, that will be most easily unloaded while alongside a pier and causeway. Considerations are being given to future modifications of the MPF(F) for incorporating additional features within the design that will make at-sea cargo transfer more efficient over a wide range of sea states. A decision to configure the MPF(F) vessel in this way constitutes a decision to configure the sea base at what was termed Level One in Chapter 1 of this report—that is, a modest improvement in current capability, with little potential for tactical support for forces ashore from the sea.
Several concepts have been put forward for the use of a ramp with a sea base. The ramp from the sea base might be designed to terminate on an ILP or on a MLP. A short bridge might connect either the ILP or MLP with a TSV/HSV, an LCAC or an B-HSC. No such designs have been adopted. Other than conventional weight/moment and ramp-load capacity decisions that ultimately must be made, there are no currently perceived problems that would preclude the incorporation of such capabilities into an MPF(F) design. However, one must recognize that ramp locations and functions are major drivers of ship designs. They affect virtually the entire internal arrangement of the ship as well as its structural design. In the case of a stern ramp, for example, if one is to be fitted, the internal deck arrangements must permit it to be stowed. Ramps cannot be easily retrofitted into
an existing design if the ship class was not designed from the start with the ramp locations and functions identified.
If a decision is made to commence engineering design studies for a RO/RO ramp for MPF(F) in 2008, the committee is confident that such a capability could be in service between 2013 and 2016. In any case, it appears to the committee that any RO/RO ramp design that is adopted for a sea base should be part of an integrated design of the sea base and all associated connector vessels.
The key issues in the sea base context are the following:
The locations and functions of RO/RO ramps will drive the designs of the core sea base ships as well as the designs of high-speed connectors, and
If the ramps are to be used for open-ocean cargo transfers, they must be tested at sea in realistic environments prior to committing the sea base and connector ships designs to them.
Integrated Landing Platforms
An integrated landing platform may be defined as a large floating platform (or raft) with reserve buoyancy of at least 200 to 250 tons. This buoyancy requirement is established by the need to support the weight of an LCAC and its payload.
The ILP concept of operations (CONOPS) is that an LCAC will drive itself onto the ILP that will be contiguous to an MPF(F) or to the sea base. Because of the lack of significant relative motion between the ILP and the mother ship, the transfer of loads to the LCAC will be simplified.
Although the capability to service an LCAC from an experimental ILP has been demonstrated, the final configuration of an ILP design that will be compatible with an MPF(F) hull has not been decided upon. The ILP will probably weigh about 200 to 250 tons and have dimensions of at least 100 ft by about 60 ft (the footprint of an LCAC is 87.5 ft (26.8 m) × 47 ft (14.3 m); the LCAC-X will be 1.66 times as long as the LCAC). Deploying an object of this magnitude and stowing it for transit will require the development of special handling equipment and the appropriate allocation of reserve weight and moment.
Current efforts on the development of the ILP are oriented toward its integration into the first flight of the MPF(F). The committee believes that a number of engineering design issues must be resolved prior to the incorporation of an ILP into the MPF(F). The committee does not believe that the resolution of these issues will require any S&T investment.
Realistic, full-scale, at-sea testing of the ILP and its connecting ramps must be carried out in order to confirm that they work successfully and that the required cargo transfer rates can be achieved. Also, the committee believes that this testing must be accomplished before committing the MPF(F) design to the ILP, so that an alternative transfer method could be adopted if required.
If studies show that the availability of an ILP will provide a significant enhancement of the cargo discharge rate of an MPF(F), ILPs are likely to be incorporated into the first ships of this class and might well be available operationally by 2012 or 2013.
Mobile Landing Platforms/Float-on/Float-off Heavy-Lift Ships
For several decades, the Navy and Marine Corps have had a capability of ship-to-shore transfer of cargo and equipment using landing craft, air cushion. LCACs ride on a high-pressure air cushion and can transport militarily significant payloads at relatively higher speeds than are normally achieved with conventionally designed monohulls.
One pays a price for these capabilities in that the Von Karman transport efficiency of an LCAC is low (ton-per-mile costs are high because fuel consumption is high). As a consequence, the payload range characteristics of LCACs are not compatible with the sea base CONOPS that constrain the sea base to operate at distances of greater than a hundred miles offshore. No extant LCAC design provides for round-trip ranges of these magnitudes.
Because of the attractiveness of an LCAC as a transport system that can deliver heavy equipment directly onto the beach, people have sought designs for LCAC shuttle ships that can transport fully loaded LCACs from the offshore sanctuary distances of a sea base to ranges from a hostile shoreline.
Heavy-lift ships (HLSs) have been used successfully in commercial and military salvage operations for many years. Basically, an HLS is a vessel with a large, strong, unencumbered flat deck that can be ballasted down so that its deck is awash or even below the surface of the ocean. In operation, the vessels that are to be transported flow onto the awash or submerged deck, and the HLS is then deballasted. Conceptually, the HLS would then transport the LCAC to a location where it would be capable of operating autonomously. When the LCAC had delivered its cargo to the beach, the process would be reversed and the HLS or mobile landing platform would return the LCAC to the vicinity of the sea base.
Since float-on/float-off HLSs exist, technology is not a limitation. There are shipbuilders who would be happy to provide a response to a request for a proposal. If the Navy decided to procure an HLS, it could have an operational capability in 5 to 6 years (the normal time to build a new ship design). In the past, if the Navy needed a float-on/float-off capability for a specific salvage project, it rented the services of a commercial HLS.
Although the HLS was not designed to deliver cargo, it can be used as an intermodal transfer platform. Studies of the rate of delivery of equipment to shore using such a system are not available. Since the hull forms of current HLSs are not designed for high speed, the overall equipment-delivery capability of the MLP concept may be unacceptably low unless current designs are modified to incorporate higher-speed operation.
As will probably be the case, the slow speed of the HLS may preclude its operational employment as an LCAC shuttle from sea base standoff ranges greater than 100 nmi. In that case, a high-speed LCAC shuttle would be needed with a sustained speed greater than 30 knots. This could be done with a monohull or with other hull configurations. However, the committee notes that the HLS has another critical role in the sea base—that of a transfer platform, used to facilitate vehicle transfers by RO/RO between supply ships and the sea base and also in the transfer of cargoes between the MPF(F) ships and the HSCs.
Well Deck Loaded Air Cushion Vehicles
For several decades the Navy’s amphibious ships have had an operational capability to transfer cargo to LCACs located within the ships’ flooded well deck enclosures. As sea states increase, so do the pitch, roll, and heave motions of the ship. These motions, if severe enough, will cause sloshing motions in the water of the well deck, which in turn eventually force a suspension of the loading of the LCAC.
Although the well deck can be pumped dry to eliminate the effects of water sloshing, the high-sea-state-induced pendulous motions of cargo suspended from the ship’s internal gantry will force termination of operations. In principle, the technology of stabilized cranes and dynamic guying systems that are employed for skin-to-skin cargo transfers could be used with the internal gantries of well deck amphibious ships. At present, there appears to be no program whose goal is to produce a stabilized internal gantry within amphibious ships.
The principal limitation of the use of well decks to load LCACs is the large internal cubage of the mother ship that is preempted by a well deck and the limited number of discharge points available on a well deck amphibious vessel.
Transverse (athwart ship) dry wells might be considered and experimented with. A transverse dry well configuration would reduce the ship impacts of a well and permit one-way “drive through” LCAC transits with loading from above. The well closures at the hull side could be dropped to form the entrance and exit ramps for LCAC transit. In higher sea states, the doors on the weather side of the well could be closed, and the LCAC could enter and leave (by backing) on the lee side of the MPF(F) ship. LCAC loading would be done in a sheltered environment and could be done quickly by dropping large, preloaded pallets down from above. Cargo griping to the pallets (the most time-consuming part of the loading evolution) could be done in advance on the deck above. Cargo flow rates could be significantly improved by these means.
As briefed to the committee, current thinking seems to be that well decks will not be included in the design of the MPF(F). The use of stabilized cranes and the use of ILP and MLP are believed to obviate the need for a well deck to allow transfer of cargo from an MPF(F) into an LCAC. If these three technologies are
mature by the time of initial operational capability (IOC) of the MPF(F), then well decks will not be required to load an LCAC.
Clearly, the three technologies referred to here must be proven before the MPF(F) design is frozen, not by the IOC date. If the MPF(F) will require a well deck (longitudinal or transverse) or a stern elevator and/or a stern ramp, these features must be designed into the ship from the outset. They cannot be added to the ship after delivery if the ship has not been designed to accommodate them.
The remaining question will then be, how do the LCACs reach the sea base or the theater of operations? LCACs do not have a trans-ocean self-deployment capability. One possibility may be to use an MLP as a CONUS base (or intermediate support base (ISB)) to the sea base shuttle ship. Alternatively, the LCACs might be carried as deck cargo on the MPF(F), on the sea base ship, or on the high-speed support ship, which is conceptually designed to transport CH-53E helicopters (CH-53X in the future).
ANTICIPATED TIME HORIZONS FOR THE TECHNOLOGIES
Most of the technologies and capabilities that are not currently available to support the desired sea base cargo-transfer capabilities appear to represent little more than an ensemble of moderately difficult engineering design problems. The current S&T efforts in support of the development of new or improved cargo-transfer capabilities appear to be minimally funded and do not seem to have associated dates for completion of the efforts. To the extent that any time lines exist for either S&T or R&D efforts in this area, they appear to be keyed to the fielding of MPF(F) ships or to a retrofit into future flights of the MPF(F). This implies that some of the current R&D programs for improved high-sea-state cargo-transfer capabilities may appear in about 2012 or 2013 when the first MPF(F) is commissioned. Few members of the MPF(F) design community predict that improvements in high-sea-state cargo-transfer capabilities will result from current S&T investments prior to 2020 or 2025.
The committee believes that the development of enhanced high-sea-state cargo-handling capabilities will be achieved if and only if they are integrated into the ship design process. For example:
The degree of ship-roll compensation incorporated into the MPF(F) vessel or sea base design may determine how difficult it will be to design a stabilized crane that can transfer a TEU in Sea State 4;
The size, displacement, and number of ILPs carried by the sea base will strongly influence the design, number, and total cargo throughput of the chosen connector vessel; and
The design of the flight deck and possible inclusion of an electromagnetic catapult will determine the feasibility of using STOL aircraft in lieu of develop-
ing a new family of heavy-lift VTOL. As indicated in Chapter 3, it may be necessary to separate the design of ships to handle heavy cargo by airlift and by seaborne connectors; this would lead to having two kinds of ship in the sea base, with attending operational complexities and cost.
Based on briefings that it received, the committee is not sanguine that any of the desired high-sea-state cargo-handling technologies for sea base will be available within 10 years. Although a few programs appear to exist whose end item deliverable will be available for inclusion in the first MPF(F), the MPF(F) design efforts do not appear to assume successful completion of any current S&T or R&D efforts. Briefers made vague allusions to future retrofits of new technology, but no thought appears to have been given to the implications of such technology on the overall design of the sea base, on the design of the sea-base-to-shore connector fleet, and on the requirements for the design of logistic vessels for resupply of the sea base.
TASKS FOR THE FUTURE: THE WAY AHEAD
The committee does not believe that additional studies are required at this point in order to achieve enhanced high-sea-state cargo-handling capabilities. What appears to be required is an integrated engineering development program. The committee has the strongly held view that high-sea-state cargo-handling capabilities must be integrated into the design of the ship or ships that will constitute the sea base. Near-term, full-scale, at-sea testing of cargo-transfer options, including the ILP, transverse dry well, stern elevator, and stern ramp to the HLS, should be completed, and the results should be assessed before the design of the MPF(F) is frozen.
All of the decisions regarding open-ocean cargo transfer should be informed by advance knowledge of the desired level of capability to be achieved in the sea base. Unless this determination is made in the near future, the elements of the sea base will be mismatched, and the overall level of capability will not be fully optimized.
The committee believes that a requirement for the cargo-transfer components of the sea base should be common (as opposed to being interoperable) across the Services. Although the case for a unified, systems-engineering-based management of all sea-base-related programs is made in Chapter 5 of this report, the need for such an approach is emphasized here because meaningful progress will not occur without it.
The committee believes that unless a large testbed (possibly an LMSR-size ship and later, perhaps, a reserve carrier activated for experimentation with fixed-wing, heavy-lift aircraft, if that proves necessary) is made available to test engineering designs for improved, high-sea-state cargo-handling concepts, new cargo-
handling capabilities are unlikely to be fielded by the Navy within the next 10 to 20 years.
CONCLUSIONS AND RECOMMENDATIONS
If the United States is to attain a true sea base capability rather than a maritime prepositioning capability, significant improvements must be achieved with regard to capabilities to transfer cargo and personnel to and from a sea base in high-sea-state conditions. A high-sea-state, open-ocean, cargo-transfer capability will be essential because U.S. forces may encounter limitations to port access through some combination of the following:
Nonexistence of ports;
Shallow, limiting depth of ports;
Limited diameter of turning basins;
Docks and piers unable to sustain meaningful military loads (greater than 40,000 lb);
Cruise and ballistic missile attacks on harbor facilities;
Mined harbors and approach areas;
Entry channels physically obstructed (by sunken ships); and
Managing at-sea loading and off-loading of the sea base requires a complex mix of capabilities for dealing with prevalent sea-state conditions in the most likely littoral environments. While existing capabilities and technologies permit some at-sea transfers in nonport environments during a wide range of sea-state conditions, the implementation of a joint sea basing for force projection necessitates a coordinated development and testing of open-ocean loading and off-loading capabilities for large cargo packages in conditions as severe as Sea States 3 and 4.
Most sea base concepts are based on the assumption that an intermediate support base will be available. Such ISBs may not be “sovereign” and might themselves become political, terrorist, or military targets for an adversary. Sea base design concepts should be based on the technical implications of the possible nonavailability of an ISB. In the committee’s view, this consideration further strengthens the need for a sea base to be able to accommodate heavier VTOL aircraft (e.g., C-130-like or hybrid-lifting bodies) and to accommodate heavy-lift, intership transfers.
Even if intermediate bases are available and within a reasonable distance from the intended theater of operations, the United States will need to develop and maintain a capability to deliver personnel and materiel from a sea base to the shore. This implies that there is a need to invest in technology (R&D) for the following:
Heavy-lift aircraft (about 40,000 to 43,000 lb) that can land and take off from a sea base in super-short-takeoff-and-landing (SSTOL), short-takeoff-and-vertical-landing (STOVL), and possibly in full VTOL mode;
A capability that will provide for the rapid upgrade of marginal ports and their infrastructure;
Heavy-duty causeways that can be deployed rapidly and are compatible with RO/RO ships; and
A capability that will allow open-ocean cargo transfer in high sea states from a sea base to high-speed surface connectors/litters (possibly with beachability), and/or LCACs with improved performance.
Regarding the capability for open-ocean, heavy-cargo handling, the committee concludes the following:
Attainment of high-sea-state cargo-handling capability will not be achieved until such capabilities are integrated into a ship design process that includes the associated connectors;
Presentations that it received did not convince the committee that either a sense of urgency or the required funding support was attached to developing the desired high-sea-state cargo-handling technologies; and
Absent a large-displacement (possibly an LMSR-size ship), joint testbed vessel to experiment with engineering designs and prototypes—or possibly two vessels, to experiment with heavy-lift aircraft and ship-to-ship cargo transfer if it is found that the capabilities cannot be combined in a single ship—the committee believes that enhanced high-sea-state cargo-handling capabilities may not be available for fielding by the U.S. Navy in the targeted timeframe.
The committee recommends the following:
Recommendation: The Department of the Navy should accelerate efforts to achieve (1) a capability for skin-to-skin transfer of cargo, in Sea State 4 conditions, to and from a sea base and arbitrary commercial cargo ship design, and (2) improved capabilities to transfer military cargo from a sea base to the high-speed surface connectors that move cargo from the sea base to shore.
Recommendation: The Department of the Navy should identify one large vessel to be used as a testbed for resolving the known problems, including those related to connectors and internal cargo handling, involved in at-sea cargo transfer at Sea States 3 and 4, or two such vessels if required for an integral flight deck in order to explore issues associated with potential future heavy-lift aircraft.