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Offboard Refueling and Data Transfer System (ORADTS)

Under BAA N00014-16-BA09, entitled, Automated Offboard Refueling and Data Transfer for Unmanned Surface Vehicles, the Offeror will design, build, test, and demonstrate a prototype Offboard Refueling and Data Transfer System (ORADTS). The ORADTS design must improve on previous designs by providing a more robust system that enhances system usability in higher sea states, reliability, and maintainability for implementation in Navy operations. This could be via a new and different design or via multiple technology and architecture improvements to the previous design. The program goal is to achieve a Technology Readiness Level (TRL) of 6 for the system in order to support the Navys potential consideration of the ORADTS technology in a Program of Record (PoR) milestone decision.

The Navy is developing Unmanned Surface Vehicles (USVs) that are launched and recovered from a host ship. A refueling and data transfer system that is remote from the host ship and proximate to the USV operating area will allow a substantially greater fraction of a Navy USVs endurance to be spent on performing the mission rather than on non-mission activities associated with refueling, including transiting to and from the host ship and being deployed and recovered on the host ship.

The USV to be refueled is a Fleet-class USV as defined in the Navy USV Master Plan. It is approximately 38.5 ft in length, 10.5 ft beam and full load displacement 21,400 lbs. It can carry between 400 and 650 gallons of diesel fuel marine (DFM) and uses fuel at a rate between 25 and 40 gallons/hr. The refueling port of the USV is located on the starboard side of the craft, above the waterline, about midships. There will be up to 2 terabytes of data to be offloaded from the USV, per refueling iteration. There is currently no data port on the USV. The fuel source platform (FSP) is envisioned to be another USV, a barge, a small vessel, a bladder or other platform or system. The FSPs function is to bring fuel from an existing land or shore-based source (such as a fuel depot, port or a ship) to the operating area (the operating area is the area in which the USVs perform operations). The USVs will approach the FSP, align to a connection mechanism, connect to the FSP, make fuel and data connections, receive fuel and transfer data, disconnect from the FSP and resume its mission: this sequence shall be automated and require only the supervision of a remote human operator. For an individual USV, refueling and data transfer should occur simultaneously to save time.

ONR previously demonstrated an at-sea refueling system for a USV, which provided an initial demonstration of a technical approach, significant lessons learned about operational requirements, technology limitations, and expected costs to field this new class of system in the challenging maritime environment2,3,4,5. The ONR demonstration used a towed sponson/refueling probe prototype system for refueling connection and demonstrated feasibility on the 39 ft ONR Unmanned Sea Surface Vehicle (USSV) in sea state (SS)-0 through SS-2. Specifically, a USV with a bow-mounted refueling probe made a connection to the refueling device (in this case, a drogue towed from a fuel source vessel) in SS-0, but had difficulty in performing this operation in SS-2. The SS-2 issue was due to wave-induced relative motions between the USV and the towed drogue that inhibited the USVs ability to connect to the drogue. When driven by a human operator, the capture success rate was 45% in SS-2 and 71% in SS-0.

Although at-sea testing was conducted as described above, the sea states were modest compared to Navy requirements and the refueling system was not integrated with the USV nor was integration with the ashore/afloat fuel infrastructure considered. Additional development is needed for the approach, alignment and connection of the USV to the FSP in SS-3 (threshold) SS-4 (objective) and to automate the system; this is within scope of the BAA. A particular challenge in the ONR at-sea test was hydrodynamics: the wave-induced relative motions between sponson and USV. In the future, this might be mitigated by sponson design, location of the probe on the USV relative to the USVs center of gravity (CG), and modeling and simulation (via computational fluid dynamics) of FSP/USV wave-induced motions to clarify system design.

The metric for the at-sea test is the ability of the ORADTS to refuel 650 gallons of fuel and transfer 2 terabytes of data with zero errors from a USV within 45 minutes (threshold)/30 minutes (objective) in NATO SS-3 (threshold)/ SS-4 (objective). The 45/30 minute timeframe includes the last 50 meters of USV transit to the FSP, the automated approach, alignment and connection of the USV to the FSP, the automated transfer of fuel and data, disconnection of the USV, and 50 meters transit of the USV away from the FSP. The time required for refueling and transfer of data is of critical importance since the less time spent performing these functions, the more time the USV can spend performing the mission. The FSP should be capable of refueling and data transfer for 1 USV (threshold) and 8 USVs (objective).

Up to eight USVs may be simultaneously performing a mission in proximity to each other require refueling and data transfer. Therefore, a scalable FSP capability is preferred. The costs and benefits of a single, larger FSP should be traded off against multiple, smaller FSPs. A Government study found that FSPs carrying at least 15,000 gallons of fuel are optimal since smaller amounts of fuel necessitate an unreasonably large number of FSPs.




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