Improved Distance Measurement During Underway Replenishments (UNREPs)

Navy SBIR 23.1 - Topic N231-041
NAVSEA - Naval Sea Systems Command
Pre-release 1/11/23   Opens to accept proposals 2/08/23   Closes 3/08/23 12:00pm ET

N231-041 TITLE: Improved Distance Measurement During Underway Replenishments (UNREPs)

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Autonomy;General Warfighting Requirements (GWR)

OBJECTIVE: Develop a portable device to replace the current phone/distance line capable of accurately measuring the distance between two ships and providing wireless communications during Underway Replenishments (UNREPs).

DESCRIPTION: The US Navy�s DDG-51 Class Destroyers are typically at sea for long stretches of time. Frequent resupply is required to sustain the ships at sea with UNREP. During connected UNREPs, two ships operate at 180-200 ft apart. The ships separation is continuously monitored to maintain a safe operating distance. The current process for distance measurement involves tying a rope to one ship and manually tensioning the rope between the two ships. This is manpower intense and risky. The Navy requires the development of an innovative means of distance measurement and emissions controlled (EMCON) compliant wireless communications during UNREPs.

There is a need to replace the phone/distance line with a less manpower intense system that is more flexible in location. This can be with one or two devices working in concert. The development of an improved phone/distance system to meet the Navy needs will require overcoming the following technical challenges. First, the device(s) must be able to maintain a high degree of accuracy at all times when measuring distance and provide clear communications during rough sea states and inclement weather. Environmental conditions include such hazards as rain, sea spray, and fog, all of which can disrupt the signals used in contemporary distance measuring devices and communications systems. The improved distance measuring system must be accurate in such conditions in order to prevent loss of life and shall be mounted on two moving platforms. The device must be able to compensate for this motion and maintain an accurate reading. Additionally, the device should be man-portable, compact for storage and transport, and pose no fire hazard, as it will be used in the proximity of aviation fuel. The communications system shall provide clear communications in similar conditions.

Research into distance measurement devices has revealed several methods that could potentially meet the Navy�s need. There have been numerous advances in distance measuring techniques across industry but no device has been adequately demonstrated to be a replacement for the existing Navy phone and distance line. Some technologies are accurate, but not viable in exceptionally adverse environments. Other technologies have emissions which may render it unsuitable for Navy use. Many candidate devices are not the most portable or cost-effective solution for the Navy. Further innovation is needed to reduce acquisition costs and produce a viable product for the Navy.

PHASE I: Develop a concept for an improved device(s) for distance measurement during UNREPs and communications that meets the requirements above. Demonstrate the feasibility of the concept in meeting Navy needs and establish that the concept can be developed into a useful product for the Navy. Feasibility of the distance measuring device will be established via computer modeling. The communications device will need to meet shipboard communication requirements. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Based on the results of Phase I and the Phase II Statement of Work (SOW), develop and deliver a prototype distance measurement system and communications device for evaluation. The prototype(s) will be evaluated to determine capability in meeting the performance goals defined in the Phase II SOW. Product performance will be demonstrated through prototype evaluation, modeling, and demonstration over the required range of parameters. An extended test in a maritime environment will be used to refine the prototypes into a design that will meet Navy requirements. Prepare a Phase III manufacturing and development plan to transition the distance measuring system and communications device to Navy use.

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the improved distance measuring system and communications device to Navy use. Develop installation, maintenance, and operations manuals for the distance measuring device to support transition to the fleet.

There is a need in commercial applications for distance measuring devices that are accurate in inimical conditions. Notable examples include such varied fields as mining and autonomous cars.


1.       Ryde, Julian, and Hillier, Nick. "Performance of Laser and Radar Ranging Devices in Adverse Environmental Conditions." Cite Seer X. 2009. Penn State University. November 10, 2021.

2.       Castro, Marcos, and Peynot, Thierry. "Laser-to-Radar Sensing Redundancy for Resilient Perception in Adverse Environmental Conditions." 2012. Queensland University of Technology. November 10, 2021.


KEYWORDS: Laser Range-Finder; Ranging; Underway Replenishment; UNREP; Distance Measurement; Inimical Conditions; Refueling at Sea


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 23.1 SBIR BAA. Please see the official DoD Topic website at for any updates.

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