ShadowLittoral: A Constraint-Driven Architecture for Autonomous Low-Profile Littoral Logistics

This technical white paper presents a constraint-driven systems architecture for an Autonomous Low-Profile Vessel (ALPV) designed for contested littoral resupply operations. Developed in response to the Defense Innovation Unit Commercial Solutions Opening for ALPV, the paper maps the complete constraint space defined by the simultaneous requirements of 18,000+ lb cargo capacity, sea state 5 operability, 1,000–2,000 nautical mile range, low-profile signature, autonomous navigation in GPS-denied environments, road transportability, and 180-day prototype delivery. Six vessel design approaches are evaluated against eight constraint domains through a structured constraint funnel analysis. The paper identifies and resolves coupled geometry conflicts — including demi-hull engine packaging, block coefficient–draft–wet deck clearance cascades, and added wave resistance in heavy seas — that eliminate most intuitive approaches. The surviving architecture is a 20.5-meter aluminum catamaran with mass-bounded hydrostatics (38–42 tonne lightship band), twin MAN D2676 heavy-duty marine diesel propulsion, strategic-grade inertial navigation with layered DDIL degradation, and MOSA-compliant autonomy. Every load-bearing claim is traced to verified sources including manufacturer specifications, DNV classification rules, the NPL/Southampton systematic catamaran series, and published naval INS performance data. Uncertainties are explicitly quantified, including a calm-water power sensitivity analysis and block coefficient stress testing. Honest boundary conditions disclose what the system does not do alongside what it does. The methodology — constraint space analysis with independent research verification across multiple revision cycles — is applicable to complex systems engineering problems where binding constraints span multiple engineering disciplines. Keywords: autonomous surface vessel, contested logistics, catamaran naval architecture, constraint analysis, DDIL navigation, inertial navigation, littoral operations, modular open systems, unmanned surface vessel, systems engineering