Fiveo1 Autonomous Single-Person Hybrid Surface–Subsurface Transit System @2026-10-30 19:46:54 - Calle 15 de Febrero

Fiveo1 P.O. Box 312786 Avalon, California 90704 Representative of Record: Evan Winter 0. DOCUMENT CONTROL Revision: C (supersedes Rev B; Revs A and B retained as history) Classification: Proprietary, Preliminary Design Vehicles: F5-D0 (hydrodynamic model), F5-D (autonomous demonstrator), F5-P (single-occupant platform) Basis: First-principles closure using momentum theory, drag build-up, buckling screening, mass and buoyancy budgets, and energy accounting Status: Preliminary. Not released for fabrication. Requires FEA, CFD, tank test and class review. Value convention: R = requirement, C = calculated from Section 2 assumptions, E = estimate (plus or minus 15%), T = target to be proven by test. Purpose of Rev C. Rev B split the program into two vehicles and fixed several Rev A errors. Rev C re-derives every number from stated assumptions and closes each vehicle on mass, buoyancy and energy. Closure exposed errors that had been carried forward. With those corrected, the architecture stands: the vehicle family, 15S LiFePO₄ bus, FOC BLDC propulsion, CAN-based control, fully local autonomy and independent emergency systems all remain. 0.1 Retained from Rev B (checked and correct) 15S LiFePO₄ is 48.0 V nominal (15 x 3.2 V), 54.0 to 54.75 V at full charge; 20 Ah is 960 Wh. Pressure at 30 m is 0.30 MPa gauge, 0.40 MPa (about 4 bar) absolute. LiFePO₄ has a higher thermal-runaway onset than NMC (commonly cited about 270 C versus about 210 C), long cycle life and abuse tolerance. Galvanic isolation of carbon fiber from aluminum, the Kort nozzle rationale, the bronze propeller upgrade, the modular double-O-ring flanged hull, and the rule that every single failure must leave the vehicle positively buoyant. 0.2 Change ledger (Rev B to Rev C) 1. Rev B: F5-D 650 x 120 mm, 8 to 10 kg displacement, 960 Wh. Finding: a teardrop of that size displaces about 4.5 L (7.4 L even as a pure cylinder), and a 960 Wh LiFePO₄ pack alone is about 8 kg. Resolution: F5-D resized to 1.15 m x 0.21 m (25.3 kg displacement, mass closed). The 650 x 120 form becomes F5-D0, an umbilical-powered hydrodynamic and seal model. 2. Rev B: F5-P 520 mm x 2.4 m, 190 to 220 kg. Finding: hull volume is about 316 L (about 324 kg of seawater), inconsistent with its own mass, and the interior (about 0.51 m) is no wider than the shoulders of larger adults, leaving no room for life support. Resolution: F5-P resized to 0.82 m x 3.4 m, about 1.14 t displacement, with a 0.76 m inside-diameter dry cabin. 3. Rev B: hydrokinetic regeneration 50 W at 1.5 m/s and 300 W at 2.5 m/s. Finding: total kinetic power through the 0.16 m propeller disc is about 35 W at 1.5 m/s and about 160 W at 2.5 m/s, so the Rev B outputs exceed the power in the stream. Resolution: realistic output is about 9 W at 1.5 m/s and about 40 W at 2.5 m/s (F5-D). Regeneration is demoted to a research payload. 4. Rev B: recharge via Avalon/Catalina tidal currents. Finding: currents there are generally well below 0.5 m/s (verify with NOAA CO-OPS and HF-radar data). Power scales with velocity cubed, so output is under 1 W. Resolution: shore charging is primary; regeneration is not a charging strategy at the home site. 5. Rev B: 60 W folding solar skin on F5-D. Finding: topside projected area is about 0.24 m2, about half coverable with cells at about 190 W/m2, giving 20 W peak or less. Resolution: F5-D gets an optional trickle of 20 W or less. F5-P gets a 100 W folding deck array (about 300 to 400 Wh/day). 6. Rev B: ram-air turbine ceiling about 4 W at Betz-optimal. Finding: 4.2 W is the total wind power at 10 kn through 0.05 m2. The Betz limit is about 2.5 W and realistic output is 1 W or less. Resolution: ram-air removed from the baseline. 7. Rev B: F5-P 3.8 kWh, about 5 h at 4 kn. Finding: with drag build-up and a 300 W occupied hotel load, 4 kn needs about 1.5 kW, giving about 2 h. Resolution: F5-P pack raised to 11 kWh. 8. Rev B: appendage drag multiplier of 6. Finding: arbitrary and unsupported. Resolution: explicit build-up of 2.5 (F5-D) and 2.0 (F5-P) with plus or minus 40% sensitivity bands. 9. Rev B: dump-load resistor for a seawater fault on the pack. Finding: it does not address gas evolution (hydrogen, chlorine) at exposed 48 V terminals or cell venting. Resolution: battery outside the crew cabin, insulation-monitoring device, contactors, gas-venting path. 10. Rev B: surface reserve buoyancy of at least 25 kg. Finding: about 2% of F5-P displacement, which is unsafe freeboard in waves. Resolution: at least 10% of displacement for F5-P and at least 5% for F5-D. 11. Rev B: loss of link means hover 60 s then surface abort, all vehicles. Finding: an occupied vehicle should defer to its occupant. Resolution: F5-D unchanged. F5-P is occupant-selectable, default surface and signal. 12. Rev B: wet-bay versus dry occupant not addressed. Finding: a dry 1-atm cabin is the only concept consistent with the Rev B life-support and dead-man provisions. Resolution: concept trade documented in Section 3.3. 1. BASELINE SUMMARY Role: F5-D is an unmanned autonomous demonstrator. F5-P carries one occupant in a dry 1-atm cabin. Length x diameter: F5-D 1.15 m x 0.21 m. F5-P 3.4 m x 0.82 m fairing, with a 0.78 m OD pressure hull. Displacement: F5-D 24.7 L (25.3 kg). F5-P 1,113 L (1,141 kg). Mass (E): F5-D 23.5 kg. F5-P about 1,005 kg including occupant and drop weight. Operating depth: F5-D 30 m (proof 60 m). F5-P 20 m, extended to 30 m after type test. Energy: F5-D 960 Wh (15S, 20 Ah). F5-P about 11 kWh (15S, 230 Ah class). Propulsion: F5-D one 2.4 kW peak motor. F5-P two 2.4 kW peak motors. Bollard pull: F5-D target 35 kgf or more, accept 30 kgf or more. F5-P target 90 kgf or more combined. Cruise: F5-D 3 kn for about 7.5 h and about 22 nm. F5-P 3 kn for about 10 h and about 31 nm (4 kn: about 5.7 h and about 23 nm). Max speed: F5-D 6 kn (about 1.7 h). F5-P 5 kn (about 3.3 h). Charging: F5-D shore at 0.5C or less (about 1.5 h from 20%). F5-P shore at 3.3 kW (about 3.2 h) plus 100 W solar top-up. 2. DESIGN BASIS Seawater density: 1,025 kg/m3. Kinematic viscosity: 1.1 x 10⁻⁶ m2/s (15 to 18 C). Hydrostatic pressure: p = rho g z, about 10.06 kPa per metre; 30 m is 0.302 MPa gauge. Aluminum: E = 69 GPa, nu = 0.33; 6061-T6 yield about 276 MPa typical (240 MPa specified minimum); welded heat-affected zones retain roughly half. Hull volume: V = Cp x (pi/4) x D2 x L with Cp = 0.62 (teardrop screening value). Drag: F = 0.5 rho A_f C_D k v2, with C_D = 0.12 on frontal area and k the appendage factor. Efficiencies: propeller and duct 0.55 times motor and ESC 0.88 gives 0.48 battery-to-thrust. Hotel load: F5-D 45 W nominal. F5-P 300 W nominal. Energy margin: factor of 1.2 on all demand figures; 80% usable depth of discharge. Pressure ladder: Operating, F5-D: 30 m, 0.30 MPa, mission ceiling. Operating, F5-P: 20 m then 30 m, 0.20 then 0.30 MPa, ceiling lifted only after type test. Proof: 60 m, 0.60 MPa (6 bar), unoccupied hydrostatic test for 1 h. Ultimate (analysis): 90 m, 0.90 MPa, buckling margin of at least 1.0 before knock-down; 3 times operating. Class societies set their own test and collapse factors. This ladder must be reconciled with the selected society before build release. 3. VEHICLE FAMILY AND OCCUPANT CONCEPT 3.1 Family definition F5-D0: tow-tank or flume model, seal and nozzle tests, 6 bar proof article. 0.65 m x 0.12 m. About 4.5 L. 48 V umbilical power. Proof 60 m. F5-D: autonomous demonstrator for navigation, regeneration research and endurance. 1.15 m x 0.21 m. About 24.7 L. Onboard 960 Wh. Depth 30 m. F5-P: single-occupant transit. 3.4 m x 0.82 m. About 1,113 L. Onboard about 11 kWh. Depth 20 m, then 30 m. F5-D0 preserves the Rev A hull envelope, so the original concept is not discarded. It becomes the cheapest, fastest way to retire hydrodynamic and sealing risk before F5-D is built. 3.2 Occupant geometry Adult male bideltoid (shoulder) breadth runs roughly 0.45 to 0.55 m from the 5th to the 95th percentile, and chest depth roughly 0.22 to 0.30 m. A reclined occupant plus seat, controls, scrubber, displays and clearance needs a cabin of at least 0.74 m inside diameter and about 2.2 m interior length. Rev C therefore specifies a 0.78 m OD pressure hull with 8 mm wall (about 0.764 m ID, about 1.1 m3 free cabin volume) wrapped in a 0.82 m free-flooding fairing. 3.3 Occupant concept trade A. Dry 1-atm pressure hull (baseline). The occupant breathes cabin air at surface pressure. Advantages: no decompression obligation, best occupant protection, matches the Rev B life-support provisions. Drawbacks: heaviest and costliest (about 1 t), highest class and USCG scrutiny. B. Wet bay with rebreather or surface supply. Occupant sits in water in a flooded bay. Advantages: about 250 kg class, simple hull. Drawbacks: falls under diving regulation. At 30 m (4 ATA) on air the no-decompression time is only on the order of 20 to 25 minutes, with narcosis and oxygen-exposure limits, and there is no dead-man or life-support model like Rev B. C. Surface skimmer manned, dive unmanned. The occupant rides above water in surface mode only and the vehicle dives unoccupied. Advantages: lowest risk, reuses the F5-D architecture. Drawback: does not deliver a manned subsurface transit. Baseline is A. B is a regulatory re-route, not a simplification. C is the recommended off-ramp if class cost proves prohibitive. 4. STRUCTURE AND PRESSURE HULL 4.1 F5-D (D = 0.21 m) Shell: 6061-T6, 3.0 mm, hard-anodized. Frames: 20 x 6 mm flat bar at 0.30 m pitch or finer, internal. Long unstiffened cylinder buckling: P_cr = 2E/(1 minus nu2) x (t/D)3, about 0.44 MPa (4.4 bar). This fails the 9 bar ultimate, so frames are mandatory. Buckling between frames (von Mises, L = 0.30 m): about 3.2 MPa (32 bar) before knock-down, about 3.6 times ultimate (C). Hoop stress at 0.90 MPa: pR/t is about 32 MPa, far below 276 MPa yield. Flat end closures: yield needs at least 6.4 mm at 0.9 MPa (simply supported plate, stress = 1.24 p (a/t)2). Use 10 mm. General instability: required effective frame moment of inertia about 0.15 cm4. The 20 x 6 bar exceeds this. The elastic buckling figures are screening values. Real shells carry out-of-roundness and weld or machining imperfections. FEA with eigenvalue and nonlinear imperfection analysis (target out-of-roundness 0.5% or less) is required before release. 4.2 F5-P (pressure hull R = 0.39 m) Shell: 8 mm marine-grade plate (5083-H116 or 5086), rolled and welded. Heads: 2:1 ellipsoidal, 10 mm, buckling-sized per selected class rules. Frames: 50 x 10 mm flat bar at 0.35 m pitch (about 8 frames). Required effective frame moment of inertia at 0.90 MPa: I_e = p R3 L_s / (3E), about 9 cm4. Provided (bar plus 63 mm effective shell flange): about 32 cm4, about 3.5 times the elastic requirement before imperfections (C). Hoop stress at 0.90 MPa: about 44 MPa. Hatch: 0.60 m clear, outward-opening, operable from inside and outside; coaming height set by freeboard. Viewing: camera-primary. Any viewport must be an acrylic window to PVHO-1 (ASME), with certified geometry and documented life. 6061-T6 loses roughly half its yield strength in weld heat-affected zones, which is why the F5-P hull is specified in a marine welding alloy. Machined 6061-T6 remains appropriate for flanges and hatch hardware. 4.3 Corrosion, composites and fasteners Anodize plus marine coating on all aluminum. Sacrificial anodes (zinc or aluminum alloy) are inspected after every dive and replaced at 50% consumption instead of by calendar interval. Carbon-fiber and aluminum interfaces require a glass isolation ply and sealant, since carbon in seawater is cathodic to aluminum. All penetrators are paired (primary and secondary seal), rated to proof pressure, and individually leak-monitored. 5. BUOYANCY, TRIM, STABILITY AND EMERGENCY SYSTEMS 5.1 F5-D mass and buoyancy budget (E), in kg Battery module (15S 20 Ah prismatic LFP, BMS, fusing, housing): 8.0 Main propulsor (motor 1.4, ESC 0.4, nozzle and propeller 0.8, shaft, seals, mount 0.7): 3.3 Maneuvering thrusters (one vertical, one lateral, about 100 W each): 1.4 Pressure hull (3.0 mm shell, frames, flanges, closures): 7.6 Avionics, IMU, depth sensor, acoustic modem, GNSS, wiring: 1.6 Variable-ballast unit (3.0 L tank, pump, valve): 0.8 Emergency drop weight (corrodible-link release): 0.8 Total: 23.5 Displacement (24.7 L x 1.025): 25.3 Surface reserve buoyancy: plus 1.8 kg (7.1%), and plus 2.6 kg (10.3%) after drop-weight release. Dive trim: flood about 1.8 L of the 3.0 L tank. The remaining capacity covers density and temperature variation (a plus or minus 0.3% density change is plus or minus 0.08 kg) and payload changes. 5.2 F5-P mass and buoyancy budget (E, plus or minus 15%), in kg Pressure hull (shell, heads, frames, hatch, penetrations): 250 Battery (two external pressure-tolerant modules, about 11 kWh): 120 Propulsion (two motors, ducts, propellers, ESCs): 55 Life support (72 h O₂, LiOH, cylinders, monitoring): 60 Electronics and sensors (DVL, forward sonar, modem, GNSS, cameras, compute): 60 Ballast systems (main ballast tank, variable buoyancy, blow cylinders, plumbing): 90 Free-flood fairing, mounting frames, syntactic foam: 110 Jettisonable keel (drop weight): 75 Occupant (100 kg design) plus 15 kg stowage: 115 Cabin furnishings, seat, controls, displays: 70 Total: about 1,005 Displacement (1,113 L x 1.025): about 1,141 Surface reserve buoyancy: about plus 136 kg (11.9%), and about plus 211 kg after keel release. Diving uses a main ballast tank of about 140 L (flood to dive) with a plus or minus 25 kg variable-buoyancy unit for fine trim. That range covers the roughly 0.5% seawater-density variation between coastal surface and thermocline water (about plus or minus 5.5 kg), payload changes at ingress and egress, and consumable depletion. 5.3 Surfaced stability (R) Reserve buoyancy at least 10% (F5-P) and at least 5% (F5-D). Surfaced metacentric height GM of at least 0.15 m, with a positive righting arm at every heel angle with the hatch closed (self-righting). Hatch coaming height such that the sill stays above the waterline in the design sea state (initially sea state 2). Inclining experiment before first occupied dive. 5.4 Emergency systems Passive positive buoyancy on power loss: F5-D uses fixed foam plus an empty-tank default and is surface-stable if de-energized. F5-P uses foam plus a main-tank blow default and is surface-stable if de-energized. Drop weight: F5-D has a 0.8 kg corrodible link (timed fail-safe release) plus electrical release. F5-P has a 75 kg keel with mechanical release inside and outside, redundant of electrical. Emergency blow: not applicable to F5-D (pump-out only). F5-P has two independent paths from two 3 L, 200 bar cylinders (about 600 L free gas each); a 140 L tank at 4 bar absolute needs about 560 L. Positive buoyancy in 8 s or less at 30 m (T). Independent power: a 12 V sealed battery on both vehicles. F5-D uses it for beacon and release. F5-P uses it for strobe, AIS man-overboard class transmitter, life-support monitors and comms. Locating aids: F5-D has a strobe and GNSS beacon at surface. F5-P has a strobe, beacon, radar reflector and PLB-class transmitter. 6. PROPULSION AND MANEUVERING 6.1 F5-D main drive Direct-drive sensorless FOC BLDC, 48 V, 2.4 kW peak, firmware-limited to 800 W continuous; IP68, mechanical face seal primary with lip seal redundant. Four-blade ducted propeller of 0.16 m diameter inside a Kort nozzle (OD about 0.19 m, inside the 0.21 m hull envelope). Rev C material is Ni-Al bronze or 316 stainless in place of aluminum. Bollard check (C): the actuator-disc bound is T = [P sqrt(2 rho A)] to the power 2/3. With shaft power about 2.11 kW and A = 0.0201 m2 this gives about 568 N (about 58 kgf) ideal. With a figure of merit of about 0.65 (including nozzle gain) the expected value is 35 to 42 kgf. Target of 35 kgf or more is credible; acceptance is 30 kgf or more. Peak current is about 50 A (2.5C on 20 Ah); a 60 A bus is adequate. Reverse thrust is at least 40% of forward. The 2.4 kW rating is far above cruise needs (about 100 W thrust-equivalent); it exists for bollard and current-fighting tests. 6.2 F5-D maneuvering Below about 1.2 kn control surfaces lose authority. One vertical and one lateral tunnel thruster (about 100 W each) provide depth, pitch-trim and yaw control during loiter and station-keeping. 6.3 F5-P propulsion Twin counter-rotating motors, 2.4 kW each, with 0.30 m ducted propellers on aft outriggers. Bollard (C): ideal about 88 kgf per thruster, expected 55 to 65 kgf each; target 90 kgf or more combined. Single-motor fail-home: one thruster alone exceeds the roughly 36 kgf-equivalent drag at 5 kn, so the vehicle holds at least 4 kn on one motor. Dual 48 V buses with separate contactors. Bus conductors and fusing are rated for 100 A peak (twin motors) with class-T fusing. The Rev B 60 A umbilical rating is adequate only for F5-D. Stern planes and rudder for authority at 1.5 kn and above; twin thrusters give differential yaw below that. 7. ENERGY AND POWER ARCHITECTURE 7.1 Storage and battery safety Configuration: F5-D is 15S1P LiFePO₄, 20 Ah, 960 Wh. F5-P is two 15S modules of about 115 Ah in parallel, about 11 kWh. Bus voltage: 48.0 V nominal, 54.0 to 54.75 V full, 45 V cutoff, on both. The bus stays below the 60 V DC extra-low-voltage threshold. Location: F5-D inside the pressure hull in its own sealed housing with burst-disc relief. F5-P outside the crew cabin in two pressure-tolerant modules with an overboard gas-venting path. Protection: cell-level fusing, balancer, and BMS on CAN for both. F5-P adds per-module contactors and class-T bus fusing. Fault detection: F5-D has an insulation-monitoring device (IMD) and leak sensors. F5-P has an IMD plus per-module ground-fault trip. Charging: F5-D uses CC/CV at 0.5C or less (10 A). F5-P uses a 3.3 kW shore charger. Qualification: UN 38.3 for transport, pack abuse and seawater-immersion test on both. F5-P adds a pack-level standard (IEC 62619 or UL 1973 class) and ABYC E-13 guidance. The Rev B immersion fault path (dump-load resistor) is withdrawn. Seawater on exposed 48 V terminals can evolve hydrogen and chlorine and a resistor does nothing about it. Prevention is by double sealing, the IMD tripping the contactors, and keeping the pack out of any occupied space. 7.2 Generation, corrected budgets Hydrokinetic regeneration (F5-D, research payload). Back-driving the motor as a turbine is sound physics, but the available power is set by 0.5 rho A v3 through the 0.16 m disc (A = 0.0201 m2), the Betz limit (16/27, about 0.59) and real-world losses. Using an overall C_p times efficiency of about 0.25 (plus or minus 30%): 1.0 m/s: stream power 10 W, expected electrical output about 3 W. 1.5 m/s: 35 W, about 9 W. 2.0 m/s: 82 W, about 21 W. 2.5 m/s: 161 W, about 40 W. 3.0 m/s: 278 W, about 70 W. Mooring load at 2 m/s is about 55 N (turbine thrust about 33 N plus hull drag about 21 N). Recovering 768 Wh at 2 m/s would take about 37 h. For F5-P the twin 0.30 m disc pair yields only about 145 W at 2 m/s, so regeneration is not a baseline charging method for either vehicle. Solar. F5-D: 20 W or less, optional trickle. F5-P: 100 W folding deck array deployed only when surfaced, about 300 to 400 Wh/day in Southern California summer conditions (about 5 to 6 equivalent sun-hours). It is a standby and hotel-load top-up, not a mission energy source (about 3.5% of pack per day). Ram-air. Removed. 7.3 Electrical integration Buses: 48 V traction, isolated 12 V control, and an independent 12 V emergency bus (sealed battery) with its own contactors. F5-D umbilical and harness: 4-conductor armored, two power conductors rated 60 A, CAN pair with 120 ohm terminations. F5-P: 100 A peak traction cables and dual CAN (A and B) physically separated. Wet-mateable subsea connectors at all hull penetrations; single-point ground; sacrificial anodes per Section 4.3. 8. PERFORMANCE ANALYSIS (ENERGY ACCOUNT CLOSED) 8.1 F5-D Assumptions: A_f = 0.0346 m2, C_D = 0.12, k = 2.5, efficiency 0.48, hotel 45 W, factor 1.2, 768 Wh usable. 1 kn: drag 1.4 N, thrust power 0.7 W, electrical propulsion 1.5 W, total demand 56 W, endurance 13.8 h, range 13.8 nm. 2 kn: 5.6 N, 5.8 W, 12 W, 68 W, 11.2 h, 22.4 nm. 3 kn: 12.7 N, 19.6 W, 41 W, 103 W, 7.5 h, 22.4 nm. 4 kn: 22.6 N, 46 W, 97 W, 170 W, 4.5 h, 18.1 nm. 6 kn: 50.7 N, 157 W, 326 W, 445 W, 1.7 h, 10.4 nm. Bare-hull drag at 4 kn is only about 9.0 N. The factor of 2.5 covers nozzle, fins, thrusters, antennas and fittings. A plus or minus 40% error in the drag coefficient moves 4 kn endurance between about 3.5 h and about 6.2 h, which is why drag is validated on F5-D0 before F5-D is built. Best range is flat between 2 and 3 kn (about 22 nm). Rev B's 5.5 h and 22 nm at 4 kn is replaced by 4.5 h and 18 nm. 8.2 F5-P Assumptions: A_f = 0.528 m2, C_D = 0.10, k = 2.0, hotel 300 W, factor 1.2, 8.8 kWh usable. 1 kn: drag 14 N, thrust power 7 W, electrical propulsion 15 W, total demand 378 W, endurance 23.3 h, range 23 nm. 2 kn: 57 N, 59 W, 123 W, 508 W, 17.3 h, 35 nm. 3 kn: 129 N, 199 W, 414 W, 857 W, 10.3 h, 31 nm. 4 kn: 229 N, 471 W, 982 W, 1.54 kW, 5.7 h, 23 nm. 5 kn: 358 N, 921 W, 1.92 kW, 2.66 kW, 3.3 h, 16.5 nm. Hotel load dominates below 3 kn. Mission policy: every dive plan ends with at least 25% of usable energy (about 2.2 kWh) in reserve. An 8 h leg at 3 kn uses about 6.9 kWh and satisfies this. 8.3 Recharge balance F5-D: 768 Wh at about 0.5C is about 1.5 h plus CV taper. F5-P: 8.8 kWh at 3.3 kW (92% charger efficiency) is about 2.9 h, or about 3.2 h with taper. Sorties are planned around shore charging at a dock, not around current-based regeneration. 9. LIFE SUPPORT (F5-P) Oxygen consumption: 0.5 L/min (30 L/h) at moderate workload; resting adults are about 0.25 to 0.30 L/min. CO₂ production: about 0.43 L/min (respiratory quotient 0.85), about 47 g/h. Cabin free volume: about 1.1 m3. Mission: 12 h or less. Emergency reserve: 72 h design. Class rules for passenger submersibles commonly require on the order of 72 to 96 h, so this avoids a waiver dependency. Why metering is continuous. In a 1.1 m3 cabin the occupant consumes about 2.7 percentage points of O₂ per hour, falling from 20.9% to the 19.5% floor in about 30 minutes with no makeup, and raises CO₂ by about 2.3 points per hour, reaching 0.5% in about 13 minutes with no scrubbing. Both must therefore be actively controlled at all times. Sizing for 72 h. O₂: about 2,160 L at STP, about 3.1 kg, stored in two 6 L cylinders at 200 bar (about 2,400 L). CO₂: about 3.4 kg produced. At a practical 0.55 kg CO₂ per kg LiOH (theoretical 0.92) the scrubber needs about 6.2 kg, so specify at least 7 kg LiOH in three canisters. Two independent circulation fans and canister trains. Atmosphere limits (R). O₂ 19.5 to 23.0% (control band 20.5 to 22.0%, upper limit chosen for fire safety). CO₂ alarm at 0.5% and emergency action at 1.0%. CO, hydrogen, humidity, temperature and cabin-pressure sensors. No lithium cells in the cabin. Two breathing masks with an independent 30-minute supply (retained from Rev B). Occupant authority (R). Dead-man occupancy sensor. Interior manual override of every autonomous command. Interior controls for abort, main-tank blow, keel release and strobe. The hatch can be opened only when surfaced and pressure-equalized, and from both sides. 10. NAVIGATION, COMMUNICATIONS AND AUTONOMY Navigation. F5-D uses a MEMS AHRS with magnetometer, a pressure depth sensor (plus or minus 0.05 m) and an optional DVL; dead-reckoning drift is typically 1 to 2% of distance traveled without a DVL, with surfacing GNSS fixes. F5-P uses a fiber-optic-gyro INS plus a mandatory DVL, typically 0.1 to 0.3% of distance, GNSS at surface and optional acoustic positioning from the support vessel. Route planning. A* over a bathymetric cost map built from NOAA/NCEI coastal relief data, with horizontal and vertical uncertainty buffers. Minimum bottom clearance is 5 m (F5-D). Forward-looking sonar (30 m range) is mandatory on F5-P. Charted depths are a planning aid, never the sole collision defense. Communications. Surface: encrypted 2.4 GHz telemetry for short range, with cellular or satellite backhaul for the support vessel. Subsurface: acoustic modem at roughly 1 to 10 kbps at short range, falling to hundreds of bps at kilometre range, with about 0.67 s latency per kilometre. Acoustic links are supervisory only. F5-P adds a voice channel in the standard underwater-telephone band (about 8 kHz) and a tether option for trials. Security. Upgrade Rev B from AES-128 to authenticated encryption (AES-256-GCM), with replay protection, per-sortie key rotation and signed mission files. Compute. ARM-class flight computer running ROS 2, with fully local autonomy. A separate safety microcontroller, independent of the ROS 2 stack, owns heartbeat, depth fence, blow and keel release logic, so no autonomy-software fault can disable surfacing. Loss of link. F5-D: hover 60 s, then controlled surface abort. F5-P: the occupant is alerted; default is surface and signal, occupant-selectable. Data. Crash-protected flight-data recorder in both vehicles, with a locator beacon on the F5-P recorder. 11. SAFETY ENGINEERING Method. HAZID, FMEA, fault-tree analysis and STPA, with the hazard log opened in Phase 0 and a gate rule that every open critical hazard blocks the next phase. Hull collapse or leak: proof test, frames, double seals, per-bulkhead leak sensors, depth fence. Thermal event: battery outside cabin, venting, IMD, LiFePO₄ chemistry, no cabin ignition sources. Loss of buoyancy control: passive positive buoyancy, redundant blow paths, drop keel, independent surfacing controller. Loss of life support: dual scrubbers, continuous O₂ metering, masks, 72 h reserve, interior alarms. Surface collision: navigation lights, strobe, radar reflector, chase vessel, Notices to Mariners, cleared zones. Entanglement or seabed contact: forward sonar, clearance rules, no-transit zones near fishing gear and moorings. Hatch failure or entrapment: outward-opening dual-operable hatch, keel and blow reachable from inside. Electric shock: bus below 60 V DC, IMD, grounding, touch-safe enclosures. Software fault: IEC 61508 lifecycle with SIL allocation, DO-178C-informed rigor for critical modes, and 1,000 or more Monte Carlo missions with fault injection before first water. Principle. No single failure may prevent surfacing, and the occupant never depends on software to surface. Operational fences. Geofence, depth ceiling (20 m on F5-P until type-tested), marine-mammal and swimmer standoff, no-go zones near bathymetric unknowns, and a support vessel within acoustic range for every F5-P dive. Identify the nearest hyperbaric facility before any diver-support activity (relevant to concept B, not to the dry-cabin baseline). 12. REGULATORY AND SITE CONSIDERATIONS This section is a pathway, not legal advice; each item must be confirmed with the relevant authority. U.S. Coast Guard. Engage early through the local Sector (Los Angeles–Long Beach) and the Marine Safety Center for plan review. The status of a privately operated single-occupant submersible is not a settled category, and scrutiny rose sharply after the June 2023 loss of the Titan submersible. Unclassed, unreviewed manned designs are an unacceptable risk and should not be pursued. Classification. ABS Rules for Building and Classing Underwater Vehicles, Systems and Hyperbaric Facilities, or DNV rules for underwater technology; ASME PVHO-1 for viewports and where class rules adopt its pressure-vessel provisions. Choose a society and obtain a pre-application meeting before Phase 3. Electrical and batteries. ABYC E-11 (AC and DC systems on boats) and E-13 (lithium-ion batteries) as design guidance. Navigation rules. Treat both vehicles as vessels while surfaced (72 COLREGS, lights and signals) and publish a Local Notice to Mariners for each trial window. Marine environment. Marine Mammal Protection Act considerations for acoustic emissions and standoff. As far as I know Avalon is adjacent to Lover's Cove SMCA and Casino Point Dive Park, so confirm current boundaries and permitting with CDFW and the City of Avalon Harbor Department before any water trial. Catalina lies outside the Channel Islands National Marine Sanctuary, but verify. Radio. 2.4 GHz ISM operation under FCC Part 15. Any licensed marine radio, AIS man-overboard device and PLB-class beacon must be certified and registered. 13. VERIFICATION MATRIX Pressure integrity: external hydrostatic proof with strain gauges at frame knuckles; every manned dive preceded by a 0.5 bar vacuum-decay leak check. Threshold: 6 bar, 1 h, zero leak. Buckling model validation: test-to-collapse of a sacrificial F5-D0 shell. Threshold: measured collapse within plus or minus 20% of FEA prediction and at least 0.9 MPa. Drag: F5-D0 tow tank or flume with Reynolds corrections. Threshold: k times C_D within plus or minus 25% of 0.12 x 2.5. Bollard pull: dock test. Threshold: F5-D at least 30 kgf (target 35); F5-P at least 90 kgf combined. Endurance: full mission profile. Threshold: F5-D at least 7 h at 3 kn; F5-P at least 8 h at 3 kn with 25% reserve. Regeneration (F5-D): tow test at 2 m/s. Threshold: at least 15 W net into the bank (Rev B's 80 W is withdrawn). Trim and reserve buoyancy: weighing and inclining experiment. Threshold: F5-P reserve at least 10%, GM at least 0.15 m, self-righting. Emergency blow: unmanned commanded blow at 30 m. Threshold: positive buoyancy in 8 s or less. Keel and drop-weight release: mechanical and electrical, from inside and outside. Threshold: 100% in 20 trials. Loss of link: RF and acoustic dropout test. Threshold: F5-D hovers 60 s then surfaces; F5-P alerts then surfaces. Life support: 72 h chamber and dock rig with a metabolic simulator. Threshold: O₂ 19.5 to 23% and CO₂ 0.5% or less throughout. Battery safety: abuse and seawater-immersion test. Threshold: no propagation, no cabin gas ingress. Software: simulation-in-the-loop and hardware-in-the-loop. Threshold: zero unsafe outcomes in 1,000 or more missions. 14. PROGRAM PLAN (ordered gates, not dated commitments) Phase 0: Rev C baseline decision, hazard log opened, vendor and class shortlist. Exit: decisions D1 to D6 closed and baseline signed. Phase 1: F5-D0 build; proof test, tow or flume drag, seal and nozzle work, sacrificial collapse test. Exit: 6 bar for 1 h clean; drag and buckling models validated. Phase 2: F5-D build; bench, dock, controlled water, then open-water trials after permits. Exit: 7 h at 3 kn; navigation drift measured; regeneration characterized; loss-of-link demonstrated. Phase 3: F5-P design freeze with FEA, mass-properties control, life-support and systems rigs, class and USCG engagement. Exit: class pre-application accepted; life-support rig passes 72 h. Phase 4: F5-P hull proof unoccupied; unmanned sea trials to 20 m; unmanned 30 m blow and keel demonstrations. Exit: all emergency demonstrations 100%; hazard log clear. Phase 5: occupied trials, tethered to 10 m or less, then free at 20 m, then type test to 30 m with class witness. Exit: abort envelope demonstrated; ceiling extension approved. If class or USCG cost proves prohibitive at the end of Phase 2, fall back to concept C with the F5-D architecture. 15. TOP RISKS 1. F5-P class or USCG pathway cost or refusal. Likelihood high, impact high. Mitigation: early engagement and the concept C off-ramp. 2. Buckling or collapse model error. Medium, high. Mitigation: F5-D0 collapse test, nonlinear FEA, 3 times ultimate. 3. F5-P mass growth beyond plus or minus 15%. High, medium. Mitigation: mass-properties control, plus or minus 25 kg variable buoyancy, keel sizing margin. 4. Battery thermal event. Low, high. Mitigation: external modules, venting, IMD, abuse testing. 5. Penetrator or seal failure. Medium, high. Mitigation: double seals, per-compartment leak sensors, proof tests. 6. Hatch failure or entrapment. Low, high. Mitigation: outward-opening dual-operable hatch, interior release of keel and blow. 7. Navigation drift in GNSS-denied dives. Medium, medium. Mitigation: DVL, surfacing intervals, acoustic positioning. 8. Autonomy software fault. Medium, high. Mitigation: independent safety controller, SIL process, Monte Carlo fault injection. 9. Surface collision near Avalon traffic. Medium, high. Mitigation: Notices to Mariners, lights, chase vessel, cleared zones. 10. Regeneration under-delivers. High, low. Mitigation: already demoted; shore charging baseline. 16. DECISIONS REQUESTED FROM THE REPRESENTATIVE OF RECORD D1. Approve the F5-D (1.15 x 0.21 m) and F5-P (3.4 x 0.82 m) resizing and the introduction of F5-D0. D2. Confirm occupant concept A (dry 1-atm cabin) as baseline with concept C as the fallback. D3. Confirm the 20 m initial manned ceiling and the 72 h life-support reserve. D4. Confirm shore charging plus solar as the baseline, with regeneration as research only. D5. Select a classification society and open a pre-application dialogue. D6. Confirm the trial site and permitting path (harbor, CDFW, USCG notices). Immediate actions. Freeze Rev C; open the hazard log; commission nonlinear FEA of the F5-D and F5-P shells; source an F5-D0 test article and tow or flume access; shortlist cells, motor and DVL vendors; draft the class pre-application package (this is the Rev D scope together with the propulsor alloy trade study). APPENDIX A. WORKED EQUATIONS Pressure: p = rho g z = 1025 x 9.81 x 30 = 0.302 MPa gauge (0.403 MPa absolute). Displacement: V = 0.62 x (pi/4) x D2 x L. F5-D: 0.62 x 0.7854 x 0.0441 x 1.15 = 24.7 L. F5-P: 0.62 x 0.7854 x 0.6724 x 3.4 = 1,113 L. Long-cylinder buckling: P_cr = 2E/(1 minus nu2) x (t/D)3. F5-D: 2 x 69 GPa / 0.891 x (0.003/0.21)3, about 0.44 MPa. Between frames (von Mises): P_cr is about 2.42 E (t/D)^2.5 divided by [(1 minus nu2)^0.75 x (L/D minus 0.45 sqrt(t/D))]. F5-D at L = 0.30 m: about 3.2 MPa. General instability: I_e of at least p R3 L_s / (3E). F5-P at 0.90 MPa: 0.9 x 10⁶ x 0.39³ x 0.35 / (3 x 69 x 10⁹), about 9 cm4. Flat plate closure: maximum stress = 1.24 p (a/t)2 for a simply supported circular plate. Drag and power: F = 0.5 rho A_f C_D k v2; electrical power = F v / 0.48; total = (electrical + hotel) x 1.2. Bollard: T = [P_shaft sqrt(2 rho A)] to the power 2/3, then times a figure of merit of about 0.65 including nozzle. Regeneration: P = 0.5 rho A v3 x C_p x efficiency; Betz limit C_p of at most 16/27. Ram-air check: 0.5 x 1.225 x 0.05 x 5.14³ = 4.2 W total wind power. Life support: 0.5 L/min x 60 x 72 h = 2,160 L O₂; times 1.429 g/L = 3.1 kg. Rev C is preliminary engineering guidance prepared for Fiveo1. It does not replace stamped naval architecture, class review, hazard analysis by qualified personnel, or physical test. Next planned revision: Rev D, covering the propulsor alloy trade study, DVL and INS integration, nonlinear shell FEA results, and the class and USCG pre-application package.