As the U.S. Navy increases its investment in its fleet of unmanned undersea vehicles (UUV), suppliers of rugged commercial-off-the-shelf (COTS) subsystems, providing solutions for mission computers, network switches and routers, and data storage are meeting the needs of these unique platforms.

The Navy classifies UUV systems into four categories, based on their size and how they are launched. Small UUVs range in diameter from 3" to 10" and can be man portable or submarine launched. Examples of small UUVs include the Swordfish and Sandfish. Medium UUVs have a diameter of 10" to 21" and are surface or submarine launched. Examples of medium UUVs include the Kingfish and the Knifefish. The Knifefish UUV, which is dedicated to mine hunting, is a great example of a UUV designed for a specific purpose. Large displacement UUVs (LDUUV) range in size from 21" to 84" in diameter and are also launched on the surface or from a submarine.

In December 2020, the U.S. Navy released a request for proposals for a new Large Displacement Unmanned Undersea Vehicle (LDUUV) program, also known as Snakehead. Snakehead is a long-endurance, multi-mission UUV, deployed from submarine large open interfaces, with the capability to deploy reconfigurable payloads. The government plans to build two prototype Snakehead platforms in 2021. The last category of UUV, Extra Large, features a diameter greater than 84" and are pier launched. Examples of these XLUUVs include the appropriately named Orca.

The advantages of UUVs are numerous. They can autonomously undertake critical underwater missions without putting warfighters in harm’s way. They can travel great distances—sometimes missions can involve traveling thousands of miles. They can remain underwater for a long time, and for missions such as ISR, they can collect and store huge amounts of data.

A typical scenario using unmanned underwater vehicles for mine detection.

For suppliers of the rugged electronic subsystems that are used onboard UUVs to support their critical missions, a key design challenge is to optimize the system’s size, weight, and power (SWaP), while delivering the required level of performance to satisfy the mission. Curtiss-Wright currently supports a number of UUV programs with Modular Open System Approach (MOSA) based solutions, with equipment currently deployed on UUV platforms that range from open standard single board computer modules, to network routers and data storage systems. Key to the success of these solutions is their ability to manage the right balance between minimizing size and heat dissipation and delivering the optimal level of performance. Another key consideration is the hardware’s support for data encryption, either for data-at-rest (DAR), as in a data storage system, or for data-in-motion in a network switch or router solution.

In one example of a COTS solution deployed on an LDUUV, a system integrator required a small form factor network attached storage (NAS) solution to handle terabytes of information. This UUV required a high storage capacity solution to store critical mission data on long-range missions. In order to conserve power and allow for longer, sustained missions, the UUV has a narrow cross-section that minimizes drag as it moves along. This results in a space-constrained environment for onboard systems, including the NAS. Weight is also an important consideration, since the lighter the UUV, the less power required for its propulsion. Minimizing the power required for onboard embedded computing systems frees up more power for propulsion, which in turn enables longer missions.

Modern UUVs are equipped with a variety of sensors depending on the mission profile. At a minimum, the UUV’s location, direction, and speed must be measured. However, environmental sensing is also critical in order to avoid obstacles (such as rocks, shoals, and sand bars) and threats (such as surface vessels, other UUVs, and aircraft).

Snakehead is a long-endurance, multi-mission UUV that can be deployed from submarines.

Collected by the UUV’s sonar system, this environmental sensing data is gathered and stored so that it can be processed by one of five onboard compact Parvus DuraCOR 311 mission computers. The rugged DuraCOR 311, one of the industry’s smallest rugged mission processors, features a low-power Intel Atom quad-core CPU, and can be easily modified for specific application requirements via multiple expansion slots that support open architecture Mini-PCIe (mPCIe) cards. The sonar data is also saved for post-mission analysis at the base station and provides valuable insights into the success of the mission.

As the 2016 capture of a UUV by the Chinese powerfully illustrated, sensor data must be protected, even if it's simple oceanographic information like salinity or depth. Since their UUV would be collecting top secret data, the manufacturer required that the DAR be protected by agency-approved encryption techniques. For this application, Curtiss-Wright provided a SWaP-optimized Data Transport System (DTS1) data storage solution to deliver certified encryption and transportable high-capacity storage to protect the platform’s valuable mission data. The DTS1 is a small form factor file server that weighs just three pounds, occupies less than 50 cubic inches, and provides scalable storage of up to 8 TB on a single removable memory cartridge (RMC).

The DTS1 is the industry’s first COTS DAR NAS solution that supports two layers of full disk encryption in a single device. It provides two layers of Commercial Solutions for Classified (CSfC) approved encryption (one hardware and one software layer). CSfC is an NSA-approved approach for protecting classified National Security Systems (NSS) information. Because the DTS1 has been approved for protection of top secret data, classified data can be safely transported between the base station and UUV. With adversaries targeting data during transport, this capability significantly lowers the data security risk.

The two DTS1 encryption layers have each been certified by National Information Assurance Partnership (NIAP) under the Common Criteria (CC) program and are also listed as approved NSA CSfC components. Because the DTS1 layers are NSA CSfC approved, the customer can securely store top secret data onboard the UUV and then safely transport the data on the RMC. The RMC is considered unclassified when removed and unpowered.

Another challenge for UUV system integrators is integrating network communications capabilities within the platform. To address those requirements, as well as provide encryption for data-on-the-move, there is a range of ultra-small network switches and routers that support the popular and preferred Cisco IOS enterprise networking infrastructure. Currently in operation onboard a Medium UUV platform are Curtiss-Wright’s DuraMAR network router solutions, and the PacStar 447 next generation network router will also soon undergo testing in these types of platforms. These two product families provide UUV system integrators with a spectrum of ruggedization options, ranging up to fully sealed enclosures, full MIL standard environmental testing. They support full military operating temperature ranges and, if required, standard military connectors.

Parvus DuraMAR routers are COTS mobile routers integrating a Cisco Systems Embedded Services Router (ESR) card like the ESR 6300 or ESR 5915 in an ultra-rugged chassis with circular MIL connectors. They have extensive MILSTD-1275/704/810/461 qualification testing and boast the cybersecurity afforded by Cisco’s products. For applications that don’t require the highest levels of ruggedization, the PacStar 447 small router module embeds the Cisco ESR6300 card and provides high-performance routing, switching and advanced network access in a compact, quick setup, rugged form factor. PacStar 447 can be optionally managed by PacStar IQ-Core Software, which simplifies system setup, network management and protects the system from misconfiguration by operators in the field.

While a COTS vendor knows the SWaP characteristics of its own solutions onboard a UUV, they might not have knowledge of what other customized or other vendors’ products must also be hosted on the platform. For that reason, COTS suppliers need to continue to focus on optimizing SWaP as a matter of course. By providing extremely compact, ruggedized, fully tested and standardized products, industry can best support the system requirements for this critically important new class of naval platform and help to speed their development and deployment.

This article was written by Steve Petric, Senior Product Manager; Mike Southworth, Senior Product Manager; and Charlie Kawasaki, PacStar CTO; Curtiss-Wright Defense Solutions (Ashburn, VA). For more information, visit here .