result, current photonic masts will be replaced with Low-Profile Photonics Masts (LPPM) which resemble traditional submarine periscopes more closely. In the future, a non-rotational Affordable Modular Panoramic Photonics Mast may be fitted, enabling the submarine to obtain a simultaneous 360° view of the sea surface. Propulsor In contrast to a traditional bladed propeller, the Virginia class uses pump-jet propulsors by BAE Systems, originally developed for the Royal Navy's s. The propulsor significantly reduces the risks of cavitation, and allows quieter operation. Improved sonar systems Sonar arrays aboard Virginia-class submarines have an "Open System Architecture" (OSA) which enables rapid insertion of new hardware and software as they become available. Hardware upgrades (dubbed Technology Insertions) are usually carried out every four years, while software updates (dubbed Advanced Processor Builds) are carried out every two years. Virginia-class submarines feature several types of sonar arrays. BQQ-10 bow-mounted spherical active/passive sonar array (Large Aperture Bow (LAB) sonar array from SSN-784 onward) A wide aperture lightweight fiber optic sonar array, consisting of three flat panels mounted low along either side of the hull Two high frequency active sonars mounted in the sail and bow. The chin-mounted (below the bow) and sail-mounted high frequency sonars supplement the (spherical/LAB) main sonar array, enabling safer operations in coastal waters, enhancing under-ice navigation, and improving anti-submarine warfare performance. Low-Cost Conformal Array (LCCA) high frequency sonar, mounted on both sides of the submarine's sail. Provides coverage above and behind the submarine. Virginia-class submarines are also equipped with a low frequency towed sonar array and a high frequency towed sonar array. TB-16 or TB-34 fat line tactical towed sonar array TB-29 or TB-33 thin line long-range search towed sonar array Rescue equipment Submarine Escape Immersion Equipment MK11 suit(s) – enable ascent from a sunken submarine (maximum ascent depth ) Lithium hydroxide canisters that remove carbon dioxide from the submarine's atmosphere Submarine Emergency Position Indicating Radio Beacon (SEPIRB) Virginia Payload Module The Block III submarines have two multipurpose Virginia Payload Tubes (VPT) replacing the dozen single purpose cruise missile launch tubes. The Block V submarines built from 2019 onward will have an additional Virginia Payload Module (VPM) mid-body section, increasing their overall length. The VPM will add four more VPTs of the same diameter and greater height, located on the centerline, carrying up to seven Tomahawk missiles apiece, that would replace some of the capabilities lost when the SSGN conversion s are retired