Imagine a ship that can travel far, meet up with the sea base, take cargo in a high-sea state, and then, with a full payload of up to 750 tons, deliver that cargo up to the beach at 40 knots, then proceed to drier ground. Imagine a ship that could actually mate with larger ships at a sea base 250 miles off the coast and transfer vehicles such as four M1A1 Abrams tanks and other cargo at sea in conditions never before possible, and deliver that payload “feet-dry,” without needing any port facilities.
A combination of these attributes has never been achievable before, but a combination of new technologies makes it possible.
Dire Contingency–Capable
. . . A major earthquake strikes Haiti. There is massive destruction in the capital of Port-au-Prince, where basic services have broken down, the airport has closed, and the port has been destroyed. The island nation asks for help. Immediately, a pair of versatile ships is readied for sea at the Military Sealift Command’s Blount Island Terminal near Jacksonville, Florida. Crews rush to load containers with an emergency medical trauma unit and medical supplies, an air-traffic control facility, vehicles, and earthmoving and water-making equipment for the SeaBees.
“Seabasing is the rapid deployment, assembly, command, projection, reconstitution, and re-employment of joint combat power from the sea, while providing continuous support, sustainment, and force protection to select expeditionary joint forces without reliance on land bases within the Joint Operating Area,” notes the Seabasing Joint Integrating Concept. “These capabilities expand operational maneuver options, and facilitate assured access and entry from the sea.”
“The sea base consists of the aggregate of all the Navy’s fleet operational capabilities,” said Major General Timothy C. Hanifen, Director Expeditionary Warfare (OPNAV N85) on the Navy staff. (See page 24 for more from General Hanifen.) “The amphibious platforms and the ships that form the sea base, per the Naval Operational Concept, fit in every one of those Sea Power 21 categories.”
According to Hanifen, “The critical enabler for the sea base is amphibious expeditionary capability, and the connectors are key to that. If you were going to conduct influence operations ashore, then you must have the ability to rapidly transition forces ashore via connectors from your sea base for whatever operation is required.”
Sea-base operations reduce operational risk because ships can stand off from shore and potential land-based threats. However, the farther the sea base is from shore, the farther the connectors must travel to the beach.
The Office of Naval Research (ONR) was challenged to develop a new “seabasing enabler” concept in 2005—which became known as the Transformable Craft, or T-Craft. It had to be self-deployable and deliver cargo from the sea base to shore “feet-dry,” which means discharging its payload up to the beach, beyond the surf, and onto dry land, then repeating the process to continue delivering very specific cargo where needed.
The T-Craft had to have four primary capabilities:
• Transit 2,500 nautical miles unrefueled at a speed of at least 20 knots through sea state 5
• Transfer cargo from a ship at a sea base in sea state 4 or 5
• Carry a minimum of four M1A1 tanks, at 40+ knots, 500 nautical miles through sea state 4, unrefueled
• Deliver and offload its cargo ashore, feet-dry.
The capacity for heavy lift, high speed, and long range has never been accomplished in a single vessel. Moving material from ship to shore is governed by an “iron triangle” of speed, range, and payload. Emphasizing one attribute comes at the expense of another. The requirement of amphibious capability typically further diminishes at least one of those three vessel-performance characteristics. The T-Craft concept effectively challenges the iron triangle, offering a practical solution that could go far, fast, full, and feet-dry.
Design x Three
Three competitors were selected to develop concepts and deliver preliminary designs and proposals for construction and testing of a T-Craft INP (Innovative Naval Prototype) Demonstrator, capable of fuel-efficient self-deployment during open-ocean transit, high-speed shallow-water transit in a full-load condition; good sea-keeping during cargo-transfer-at-sea; and the ability to traverse mud flats and sand bars to offload ashore.
Three independent ship designs emerged, and each embraced a confluence of three different ship types. While the catamaran is a concept that dates to ancient times, the surface-effect ship and air-cushion vehicle are 20th-century inventions. T-Craft combines all three.
The three efforts were led by two American companies (Alion Science and Technology, Textron Marine Systems) and one Norwegian company (Umoe Mandal).
“Long-range transit would be performed using either catamaran or surface-effect ship (SES) technology,” said Kelly Cooper, the ONR project officer for the T-Craft INP. “The high-speed 500-nautical-mile dash would be performed in the SES mode, followed by landing feet-dry after transforming into an air-cushion vehicle (ACV) near shore. The principal differences in the three designs were reflected in cargo-transfer/offload systems.”
The T-Craft designs are not small craft. On average, they are about 250 feet long with a beam of 66 feet and a full-load displacement of 1,500 tons.
“T-Craft combines the attributes of the catamaran, with its high length-to-beam-ratio hulls, providing good powering and motions in a seaway; the ACV with its trunk and skirt system enabling amphibious operations; and the SES concept, producing a captured-air cushion and low wetted-area for high-speed powering and motions control,” said naval engineer Bob Wilson, an expert on SES and ACV vessels, who has reviewed the T-Craft concept designs.
Achieving high speed in heavy seas while carrying a significant cargo load is a challenge. “If you want 40+ knots in sea state 4, to date the only answer is an SES,” Wilson said.
. . . The first T-Craft approaches the shore, slows and deploys skirts around the side that inflate, creating an air cushion. Large air propellers on the top of the ship move it to the beach and safely over the surf zone and tidal mud flats up on to firm ground near a road where the vehicles and containers are quickly offloaded. The personnel required to operate the equipment and man the small medical facility and temporary air-traffic control center have been safely inside the ship, and come up to take their gear and get to work. The T-Craft carefully backs into open water, turns, and heads seaward, retracting its skirts to become an SES once again. Now empty, it sails at 40 knots to Guantanamo Bay where the Navy has shelters and MREs, arriving just 5½ hours later. A crew conducts the maintenance checks to get the ship ready for the next mission, and a relief crew is on hand to take the ship back to Haiti.
For an amphibious-force commander, the T-Craft would allow forces to be brought ashore seamlessly from the water onto land and for vehicles and equipment to be discharged directly onto trafficable terrain. “Presently, special capabilities like a pontoon causeway or low-pressure ground mats would have to be set up close to the beach interface to enable these vehicles and equipment to offload onto trafficable terrain,” said James Soon, president of Zycraft Pte Ltd. and former president of Hovertrans in Singapore, and a former fleet commander with the Singapore Navy who is familiar with the T-Craft concept (see “Robots in the Age of Pirates,” p. 54):
The T-Craft thus enables higher throughput by reducing the turnaround time for amphibious landings and by carrying more payload (in excess of 300 tons) compared to a traditional landing craft like a Landing Craft Air Cushion (LCAC).
In terms of its combat vulnerability, the T-Craft designs created to meet ONR’s required capabilities are considered no more vulnerable than an LCAC. Both will require the beach to be well suppressed of enemy fire in order to land successfully.
With the cancellation of the Marines’ Expeditionary Fighting Vehicle (EFV) program, the need to quickly move combat power from the sea base to the beach has become more acute.
Although the T-Craft was conceived as a logistics connector, the designs could be adapted for other roles. It could be armed, armored, or equipped with sensors or other modularized or installed combat components.
The different T-Craft designs offer configurations with both covered and uncovered cargo decks, and with fore and aft ramps or a single ramp. None of the current designs has a helicopter deck, but could receive deliveries by vertical replenishment.
Flexible Disaster Response
In disaster-response situations, food, water, medicine, and light engineering equipment must be delivered quickly.
While primarily intended to support combat operations, the utility of such a ship as the T-Craft for operations other than combat is readily apparent. For example, it could quickly respond to non-combatant evacuation-operation scenarios, and is able to enter damaged or austere ports, or even help civilians evacuate over a beach, away from potentially dangerous areas. T-Craft also could deliver to multiple drop-off points in a single sortie.
By transforming into hovercraft mode, the T-Craft has amphibious capability to land on a beach to deliver units intact as a comprehensive fighting force with vehicles, weapons, and equipment. The T-Craft could deliver units in better fighting condition than if they had been bouncing around in a landing craft or amphibious vehicle traveling at 7 knots. If the threat dictated that the sea base needed to be 250 nautical miles offshore, conventional landing craft would be unable to make the journey in a reasonable amount of time, if at all.
After delivering a load, T-Craft could return to a sea-base ship at 40+ knots, refuel, change crews, conduct maintenance as required, take on another load, and proceed to the next location as directed by the on-scene commander.
A single T-Craft, working with a large, medium-speed roll-on/roll-off ship (LMSR) with medical modules on board, could help deliver teams with temporary medical facilities ashore, and then remove them when the situation warrants. With its deck area and payload, T-Craft could deliver modularized surgical and dental units intact, with people, fuel, food, and water to begin operations. To complement deep-draft hospital ships, T-Craft would permit establishing smaller but more numerous medical sites on the beach where needed.
. . . As a North African country becomes unstable, the U.S. ambassador notifies American citizens that it is time to leave the country. The main port, however, is far too dangerous to enter with ships or landing craft, and the nearest safe airfield is hundreds of miles away. American citizens are told to meet at a beach on the outskirts of the capital. Two T-Craft, fitted with personnel modules and carrying several vehicles for an embarked military-police team, land on the beach, secure the area, embark the civilians, and then quickly leave the area.
Rolling Sea, Stable Platform
The T-Craft SES design with the low-pressure air cushion beneath it requires a large surface area. Unlike other ships, this can result in a squared-off ship with a wide beam, making it better suited for loading vehicles and containers.
“The SES rides on a cushion of air,” said Wilson. “As waves pass through the cushion volume, the pressure varies and this leads to what is called the air cushion’s cobblestone effect on ride quality.” He noted that extensive testing has shown that that effect can be minimized via the cushion vent valves and lift fans. By adjusting such variables, the vessel’s pitch motions can be varied for specific speeds and sea conditions.
The transfer-at-sea capability creates entirely new options for base-to-shore logistics support. The ability to mate with a stern ramp or side-loading ship or to deploy a motion-compensated ramp opens up a heretofore unheard-of range of options for moving materiel from ships to connectors.
“The ability to have pitch-and-heave control integrated with dynamic positioning to minimize the relative motion between the cargo ship and T-Craft is revolutionary,” said Navy Captain Charles Gunzel, an engineering duty officer working with Cooper on the T-Craft INP.
T-Craft can be viewed as complementary to the Joint High Speed Vessel (JHSV), the Army Logistics Support Vessel (LSV), and Landing Craft Utility (LCU)–2000 programs, and should be viewed as a connector for the Navy-after-next. It combines many of the attributes of an LCAC, helicopters, the Mobile Landing Platform (MLP) and JHSV. In many respects, its capability is more analogous to a CH-53E helicopter or V-22 tiltrotor than a small craft because it can go fast and can place cargo ashore without a port facility. As the Navy is seeing a growing demand for help during inevitable world disasters, T-Craft could be a formidable tool envisioned to bring humanitarian assistance/disaster relief from the sea in austere conditions, with or without a port.
“Other than tanks, most cargo is area-limited, not weight-limited,” said Walt Beverly, a program manager with the Naval Surface Warfare Center in Panama City, Florida, and deputy program officer for the T-Craft INP. “In many ways, T-Craft capabilities are much more like a very large helicopter than a displacement ship. Payload and craft performance are usually weight-limited while a displacement ship is usually volume-limited. During the Navy’s SES Program in the ’70s this became very apparent.”
The T-Craft does not replace L-class amphibious warfare ships, prepositioning ships, or sealift ships, but it does augment them by taking on some missions for which it is better suited. As a connector, T-Craft also further enhances the capabilities of the other ships.
“The T-Craft concept would enable the rapid employment of forces and supplies, the continuous sustainment of forces ashore, and reconstitution and recovery operations,” said Beverly.
Moreover, noted Wilson, “It fits into the logistics train of utility.”
. . . The Port-au-Prince airport has reopened, and shipping can now offload at the port using temporary piers erected by the SeaBees of the Amphibious Construction Battalion. But there are still areas inaccessible by road where people desperately need help. A T-Craft loads vehicles with supplies and food from an LMSR several miles off the coast, while another T-Craft is loading from a ship in the harbor. Both T-Craft then proceed to other points along the coast and into isolated communities where they can approach from the sea.
The envisioned demonstrator has room for crew berthing and for passengers during the transit. For longer transits, personnel-berthing modules could be carried on deck. “Alternatively, with specific missions defined, crew, passenger, and cargo accommodations can be designed into the ship,” said Beverly.
T-Craft could loiter for extended times at the sea base if necessary. According to Wilson, “The U.S. Coast Guard’s Seabird-class surface-effect ships, which operated from 1982 to 1994, demonstrated the ability to keep a crew on-station, off-cushion with very acceptable motions for up to a week at a time.”
Technology Investment
While you won’t see a T-Craft on a beach near you anytime soon, the discrete technologies that make such a ship possible will continue to be examined so they can progress from the “art-of-the-possible” to the “science-of-the-achievable.”
With three credible designs, ONR accomplished the overall goal of developing and maturing the technology necessary to meet the program objectives. The technical data are available for any future program-of-record to use.
As a result of funding priorities, a T-Craft Demonstrator will not be built. During the final two years of the program, designated as Phase III, ONR will continue to investigate and develop especially promising T-Craft foundational technology.
“Significant research initiatives are under way focused on developing ship design and physics-based analysis modeling and simulation tools to predict the performance of T-Craft designs as well as other future advanced naval ship concepts,” said Cooper.
“We are using data from physical scale-model tests performed at the Navy’s model-test facilities at the Naval Surface Warfare Center Carderock Division and at university and industry facilities to validate the phenomenological models,” he noted. “We are providing these tools and data to other Navy ship programs.”
For a novel ship design such as the T-Craft, new design models and analytical tools must be developed. New techniques must be explored involving materials such as aluminum, titanium, and composites to be able to make ship components that are lighter, stronger, longer-lasting, and not prohibitively expensive. New power systems need to be tested, such as high-speed generators and permanent magnet motors, to make possible lighter, more efficient drive assemblies for lift fans, air screws, and main propulsion.
“This research can benefit other classes of Navy ships and systems. The goal is to share this technology in order to increase capability while simultaneously reducing life-cycle cost,” said Captain Gunzel.
“For example, if it can be shown that a T-Craft can be built economically using titanium, imagine how the costly maintenance packages on other classes of ships could be reduced using similar material choices up front,” he contended. “The goal is to work closely with academia, industry, and the Navy to achieve the art-of-the-possible.”
He concluded, “Think beyond the need for a pier or shallow draft. Think beyond a 25-mile limit of ship-to-shore operations, and think far beyond the horizon. Think beyond the current limits of transfer at sea, and think beyond the current limits of the iron triangle. If you can imagine this, you can see T-Craft.”