Advanced Logistics Delivery System (ALDS)
The Advanced Logistics Delivery System (ALDS) is a construct based on research performed at the Naval Surface Warfare Center, Carderock Division (NSWCCD) innovation cell. ALDS is an over-the-beach solution to the seabasing logistics problem. It involves a ship launched, unmanned, aerodynamic centerbody containing cargo, which deploys inflatable wings and upon reaching apogee and glides to its destination.
It is assumed that the ship carries enough fuel to travel from CONUS to the sea base where it will be refueled and supplied. The sea base could potentially be located anywhere; however, it is assumed to be 250 nautical miles from shore. This distance allows the sea base to be outside of small missile range, while still being close enough for the V-22 Osprey to make trips to shore, refuel on the ALDS launch ship, and return to the sea base. The ALDS ship will support the V-22 Osprey mission by providing at least one helicopter pad and refueling capabilities. After being fueled and supplied at the sea base, the ALDS launch ship begins traveling towards the shore. A high-speed ship (approximately 40 knots) is required to efficiently deliver the supplies to the troops ashore. At approximately 20 nautical miles from the coast the ship begins traveling parallel to the coastline. This distance allows for the ship to be out of gunfire range, and the ship will either be in an assumed safe area, or escorted for protection.
The primary requirement of the ALDS mission is to provide 100 percent of the dry cargo needs of one Marine Expeditionary Brigade (MEB), which is approximately 13,000 troops with 6,800 onshore. Studies show that one MEB requires approximately 75 short tons of dry cargo each day1. A secondary mission of ALDS is to provide 10 percent of the wet cargo needs for a MEB which accounts for the troops that are further inland and in hazardous areas where manned V-22 Ospreys are not a safe option. To increase the range of the ALDS glider, disposable rockets can be added. For ALDS to deliver all of the dry cargo and 10 percent of the wet cargo, 233 gliders will be launched each day.
The main geometrical requirement of the ALDS launch ship is for the length to be at least 600 feet long. This estimate was concluded for two reasons. First, the linear induction motor requires a length of approximately 365 feet to achieve the desired velocity. Also, the machinery rooms were estimated to be 200 feet long based on X-Craft data, which is a ship with similar power requirements. Based on this length and approximate displacement calculations, the overall mission was determined to be four days. Using typical length to depth ratios, this length yields a depth of about 40 feet.
Some of the disadvantages of monohulls are that they are typically short for stability purposes, they do not have a large amount of upper deck space, and they would need considerable power to reach the required speeds. For these reasons a monohull was not chosen. Secondly, a catamaran was considered due to its large deck space; however, it has more deck space than required and is also typically a short ship. Finally, a trimaran was considered and the conclusion was drawn that this would be the best option to pursue. A trimaran typically has a long slender hull that allows for high speeds and easily lends itself to the launch tube. Another advantage of a trimaran is that the side hulls allow for extra deck space high which is efficient for the assembly process.
Since ALDS will deliver 100 percent of the dry cargo and 10 percent of the wet cargo needs for one MEB, 233 glider launches per day are required. Launches will occur every two minutes resulting in 7.75 hours of launch time. The ship is assumed to travel 250 nautical miles along the coast at 40 knots for 6.25 hours. The remaining 10 hours of the day will be used for maneuvering time, emergency launches, trips to and from the sea base, ALDS glider assembly, and general maintenance.
Another major feature included in the ALDS launch trimaran design is the linear induction motor. A linear induction motor (LIM) is simply a rotary motor sliced and rolled flat. The closest current design to the linear induction motor used in ALDS is EMALS (Electro-Magnetic Aircraft Launch System). EMALS can launch an aircraft mass between 4,500 and 45,000 kg at speeds between 50 and 200 knots with a maximum acceleration of 5 g's. The requirements for ALDS include launching a glider at a speed of 500 knots with an acceleration of 30 g's. These requirements result in a required track length of approximately 365 feet.
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