Members of the Reconnaissance and Amphibious Raids product management office at Marine Corps Systems Command took to the warm waters of Lake Anna in Spotsylvania, Virginia, to test potential upgrades to the Diver Propulsion Device July 18.
The DPD is an underwater motorized device used to extend the range of Marine combatant divers during amphibious missions, and has been a Marine Corps program of record since 2005. A single system can transport two divers nearly four miles at two knots. In efforts to constantly improve gear and equipment fielded to Marines, the RAR Team is considering upgrades that will make the submersible vehicle faster and easier to control.
“Although [the DPD] has been out in the fleet for 10-plus years, a lot of Marines don’t use it because it doesn’t perform the way they want it to,” said Jake Feeney, lead engineer for boat and dive equipment in RAR. “By putting the upgrades out there and saying, ‘This isn’t the DPD you’re used to; this is something better,’ we’ll hopefully get them back to using it and training on it.”
In the past, Marines have encountered difficulties with the stability of the DPD, and when making changes in depth and direction. To address the issues, the team tested an upgraded DPD that uses a more powerful brushless motor and a new configuration for the bow planes, which are small metal panels on the front that help the DPD driver change depth. A simple modification to how the planes connected to the device made it more stable and controllable, Feeney said. The motor is the biggest upgrade to the system.
“The current DPD has a brushed motor, but it’s inefficient and the brushes wear out over time,” he said. “The brushless motor is more efficient and powerful, so we get more battery life out of it and about 40 percent more thrust.”
A new open-propeller, or prop, will also make the DPD more reliable and easier for the operating forces to maintain.
“We were having issues with sticks and debris getting caught in the closed propeller, which would cause the engine to shut down,” Feeney said. “The company that makes the DPD had an open prop version, but they told us it may cause a performance hit of about 10 percent.”
During the testing at Lake Anna, the team wanted to assess whether a slight drop in performance was a reasonable tradeoff for increased reliability in the system.
“We were expecting the same or a little worse [performance] than with the closed propeller, but based on my initial [findings], it’s actually a little bit faster,” Feeney said.
Speaking of speed, the RAR team is also developing a table of ranges to provide to the fleet so Marines know how fast and far they can expect to travel on the DPD based on the number of Marines using it, and the configuration of gear they are carrying, he said.
Several reconnaissance Marines from the National Capital Region participated in the feasibility test, which was two-fold, also allowing them to get necessary requalification training at a location close to home.
“The Marine Corps requires us to do a certain amount of diving, and if not for events like these, Marine divers in the NCR would have to reach out to units on the east or west coast to host them for requalification dives,” said Master Sgt. Brad Colbert, reconnaissance Marine and project officer for small craft and special projects in RAR. “It’s a win-win. It gives MCSC a pool of qualified divers to draw from for testing and evaluating new diving equipment, and it gives the Marines a convenient place to maintain their diving proficiency and pay.”
Lake Anna is a prime location for the maneuverability and speed tests necessary to determine if upgrades are feasible for the DPD system. The divers swam a box-shaped course, alternating between depths of 10 and 20 feet every four minutes. The course was designed to have the Marines make changes and turns in direction and speed to test how easily the DPD recovered, and to determine if the upgraded system corrected stability issues Marines noted with the current DPD.
“This was the capstone test in our test and evaluation plan; it was a final confirmation that the upgraded systems we’ve been looking at do exactly what we hoped they would,” Colbert said. “What’s next for us is to upgrade a number of the systems so the operating forces have a more efficient system. This is part and parcel of what we do at MCSC. We identify a gap, find a material solution, test alternatives, select the right one and then we field it. For us, this was a win.”
Reconnaissance and Amphibious Raids is part of Infantry Weapons Systems, the MCSC program office that develops, tests and fields equipment from weapons and body armor to boats, parachutes and underwater gear.
Story by Monique Randolph