Development of a mini-water jet propulsion system with a diameter of just 100 millimetres to quietly propel an unmanned surface craft on remotely controlled intelligence, surveillance and reconnaissance missions, is the daunting challenge to be tackled by Rolls-Royce as they participate in a US Government funded project led by Candent Technologies Inc.
Image credit: US Navy
Candent Technologies, based in Greenfield, Indiana, was selected for the award of a Small Business Innovative Research (SBIR) Phase I contract from the U.S. Navy. This Phase I program of the contract is the first step in the development of a high efficiency heavy fuel propulsion system for a small surface unmanned craft (volatile fuels like gasoline, hydrogen, propane, or methanol not permitted).
The project, known as MUSCL (the US Navy’s Modular Unmanned Surface Craft Littoral) is to develop an X-class unmanned surface vessel, whose purpose is to reduce risk to manned forces and perform tedious and repetitive surveillance tasks.
X-Class Design Objectives
The project calls for the development of a craft that simultaneously achieves competing requirements for low size and weight, high speed, and long endurance. Yet in addition to propulsive power the system must also provide electrical power to payloads and sensors, all on the very small scale necessary for the craft to operate in shallow and riparian environments.
NAVSEA requires the propulsion and energy system for the X-class craft to be developed for a reference design with the following specifications:
Length Overall: 66 in.
Breadth Overall: 24 in.
Total Craft Weight (inclusive of hull, propulsion, energy storage, sensors): 86 lbs
Total Structural Weight: 16 lbs
Payload Weight: 20 - 30 lbs
Propulsion and energy storage system weight (including fuel): not to exceed 40 lbs
Required Performance Parameters
Fuel endurance: 6 hours (threshold), 12 hours (objective)
Speeds: loiter less than 5 knots, 15 knots cruise speed with burst speeds up to 25 knots
Operational speed profile: 10% loiter / 20% sprint / 70% cruise
Annual operating hours: 600 hrs
Temperature, Ambient: 40 to 140°F
Operating environment: Riverine (fresh, brackish, and salt water)
Wave height: 0 – 1 ft
Cooling water take-off
Efficiency: Overall Propulsion Coefficient (OPC) greater than 40%
Expected nominal power required for sensors and hotel services: 80W
The Navy admits that the optimisation of small size/weight, high speed, and long endurance, coupled with robustness and reliability, requires an innovative solution for an X-class USV, but Dennis Duke, Rolls-Royce, Advanced Programs Director, Naval Marine, was unfazed by the challenge, remarking: “Unmanned craft are a fast growing and exciting part of naval marine technology and we’re delighted to be working with Candent and the US Navy in developing this groundbreaking propulsion system.”
State University of New York Maritime College MUSCL Project 2009: Photo credit NYS Division of Military & Naval Affairs (Eric Durr)
Navy SBIR 2012.1 - Topic N121-054