could be built, to maintain the size of the fleet. These include: Propulsion concepts not constrained by a centerline shaft. Externally stowed and launched weapons (especially torpedoes). Conformal alternatives to the existing spherical sonar array. Technologies that eliminate or substantially simplify existing submarine hull, mechanical, and electrical systems. Automation to reduce crew workload for standard tasks Unified Modular Masts Virginia-class subs are the first class where all masts share common design - the Universal Modular Mast (UMM) - designed by L3 KEO (previously Kollmorgen). Shared components have been maximized and some design choices are also shared between different masts. The first UMM was installed on , a Los Angeles-class submarine. The UMM is an integrated system for housing, erecting, and supporting submarine mast-mounted antennas and sensors. The UMMs are the following: Snorkel mast Two photonic masts Two communication masts One or two high-data-rate satellite communication (SATCOM) masts, built by Raytheon, enabling communication at Super High Frequency (for downlink) and Extremely High Frequency (for uplink) range Radar mast (carrying AN/BPS-16 surface search and navigation radar) Electronic warfare mast (AN/BLQ-10 Electronic Support Measures) used to detect, analyze, and identify both radar and communication signals from ships, aircraft, submarines, and land-based transmitters Photonics masts The Virginia class is the first to utilize photonic sensors instead of a traditional periscope. The class is equipped with high-resolution cameras, along with light-intensification and infrared sensors, an infrared laser rangefinder, and an integrated Electronic Support Measures (ESM) array. Two redundant sets of these sensors are mounted on two AN/BVS-1 photonics masts located outside the pressure hull. Signals from the masts' sensors are transmitted through optical fiber data lines through signal processors to the control center. Visual feeds from the masts are displayed on liquid-crystal display interfaces in the command center. The design of earlier optical periscopes required them to penetrate the pressure hull, reducing the structural integrity of the pressure hull as well as increasing the risk of flooding, and also required the submarine's control room to be located directly below the sail/fin. Implementation of photonics masts (which do not penetrate the pressure hull) enabled the submarine control room to be relocated to a position inside the pressure hull which is not necessarily directly below the sail. The current photonics masts have a visual appearance so different from ordinary periscopes that when the submarine is detected, it can be distinctly identified as a Virginia-class vessel. As a