System

{{entity:Autonomous Underwater Vehicle}} — final review of the complete systems engineering decomposition. The AUV is a 350 kg, 6000 m depth-rated survey vehicle with 7 subsystems. Project statistics at review entry: 158 requirements across 6 documents, 133 trace links, 8 diagrams, 8 baselines. Status entering this session: validated.

Findings

Coherence. The decomposition tells a consistent story. Seven subsystems — {{entity:Navigation and Guidance}}, {{entity:Power}}, {{entity:Propulsion}}, {{entity:Emergency and Safety}}, {{entity:Sensor Payload}}, {{entity:Communications}}, and {{entity:Pressure Hull and Structure}} — divide responsibility cleanly with no functional overlaps. The Vehicle Management Computer serves as the integration node, appearing in 12 interface definitions without claiming its own subsystem, which is correct for this class of AUV where the VMC is an integration computer, not a functional subsystem.

Completeness. Every stakeholder need ({{stk:STK-OPS-001}} through {{stk:STK-OPS-009}}) traces through system requirements to subsystem and interface requirements, and onward to verification entries. The trace chain from STK-OPS-001 (24-hour autonomous mission) flows through {{sys:SYS-FUNC-001}} (10 kWh energy), {{sys:SYS-FUNC-002}} (0.1% DT navigation accuracy) to component-level battery, navigation sensor, and motor drive requirements. All 156 non-ARC requirements carry rationale and verification method.

Plausibility. Performance values are credible for a HUGIN-class deep survey AUV: FOG INS at 0.1 deg/hr drift, DVL bottom-track at 0.3% speed accuracy, 400 kHz MBES with 256 beams, Ti-6Al-4V hull at 600 bar with 1.5x safety factor. The emergency surfacing architecture — independent ESC on dedicated lithium primary battery, two-of-three voting, dual-path drop weight release — matches real deep AUV safety practice. Acoustic noise budgets (motor below 120 dB, MBES above 100 kHz) correctly separate survey and propulsion spectral domains.

Proportionality. The Emergency and Safety subsystem has the deepest decomposition (11 requirements, 7 interfaces, 8 verification entries) — appropriate for the most safety-critical subsystem. Navigation has 8 requirements reflecting its sensor fusion complexity. Power (5), Communications (5), and Structure (5) are proportionately simpler.

Traceability. {{sys:SYS-FUNC-003}} (emergency surfacing) has 11 downstream links, the highest fan-out. Each link is justified: emergency surfacing genuinely depends on drop weight release, ESC sequence, watchdog, leak detection, burn-wire backup, beacon, pinger, 2-of-3 voting, ESC power independence, PDU fault isolation, and BMS fault detection.

Diagram coverage. The system context and subsystem decomposition diagrams are complete. Power, Propulsion, and Communications subsystems have populated internal architecture diagrams. Navigation and Sensor Payload internal diagrams remain empty — a documentation gap but not an engineering gap, as the component architectures are fully specified in requirements and interface definitions.

flowchart TB
  ESC["Emergency Surfacing Controller"]
  DW["Drop Weight Release Mechanism"]
  HW["Hardware Watchdog Timer"]
  LD["Leak Detection Sensor Array"]
  EB["Emergency Locator Beacon"]
  AP["Acoustic Emergency Pinger"]
  BAT["Emergency Battery"]
  VMC["Vehicle Management Computer"]
  BMS["Battery Management System"]
  HW -->|GPIO timeout interrupt| ESC
  LD -->|I2C leak alarm| ESC
  BMS -->|Hardwired battery critical-low| ESC
  VMC -->|Heartbeat and abort command| ESC
  ESC -->|Solenoid and burn-wire release| DW
  ESC -->|Activation line| AP
  ESC -->|Arming line| EB
  BAT -->|Independent power| ESC
  VMC -->|30s heartbeat pulse| HW
  ESC -->|UART health telemetry| VMC

Corrections

Deleted duplicate {{stk:STK-OPS-006}} (identical text to {{stk:STK-OPS-007}}, both DNV-ST-0512 compliance). STK-OPS-007 retained with its existing traces to {{sys:SYS-FUNC-003}} and {{sys:SYS-FUNC-010}}.

Deleted duplicate {{sub:VER-TEST-038}} (identical text to {{sub:VER-TEST-039}}, both ESC emergency battery 48-hour endurance test). VER-TEST-039 retained with its existing trace from {{sub:SUB-FUNC-027}}.

Deleted duplicate trace link (STK-OPS-007 → SYS-FUNC-010 appeared twice).

Created trace link for orphaned {{ifc:IFC-INTERFACEDEFINITIONS-032}} (VMC-to-Navigation Processor guidance interface), deriving from {{sys:SYS-FUNC-002}}.

Populated the Emergency and Safety subsystem internal architecture diagram with 9 blocks and 10 connectors, and removed 4 duplicate placeholder blocks from a prior session.

Residual

Seven ARC architecture decisions remain orphaned — expected, as these are informational rationale records, not traceable requirements. The lint finding about 49 requirements lacking “shall” is accurate but applies exclusively to ARC decisions and VER test procedures, which correctly use descriptive rather than prescriptive language. The three ontological mismatch findings (RS-232, VMC, BMS classified without Physical Object trait) are classification observations — these entities have both physical and abstract aspects, and the UHT classification reflects their primary nature as protocols or functional systems rather than physical boxes. Navigation and Sensor Payload internal diagrams remain unpopulated.

Verdict

Pass. The Autonomous Underwater Vehicle decomposition is marked complete with baseline COMPLETE-2026-03-19. The engineering content — 156 requirements with full rationale and verification, 133 selective trace links, 7 architecture decisions, and 5 populated architecture diagrams — constitutes a coherent, plausible, and proportionate systems engineering report for a 6000 m survey-class AUV. Current project facts cleared; the next session will select a new system from the seed list.