rUv
4072455d1e
Physics scrutiny of WiFi-band maritime sensing scenarios. Steel skin depth is 3.25 um at 2.4 GHz, making bulkheads utterly opaque. Saltwater attenuation is 853 dB/m. The 'through-bulkhead WiFi radar' framing common in conservation/maritime is wrong; the actual feasible category is 'through-seam' sensing exploiting slot diffraction through gaskets, hatch seals, and vent grilles. Composite link budget for 7 maritime scenarios (ESP32-S3 121 dB budget, 10 dB SNR margin): FEASIBLE: - Man-overboard surface @ 200 m: +25 dB - Cabin door, 2 mm seam: +31 dB - Cabin door, 5 mm seam: +39 dB - Container, 30 mm vent slot: +45 dB IMPOSSIBLE: - Closed 10 mm steel door: -938 dB - Submarine pressure hull: -929 dB - Head 30 cm underwater: -231 dB Five feasible verticals catalogued: man-overboard surface, through-seam crew vitals, container tamper detection, hatch-seal predictive maintenance, engine-room thermal anomaly via condensation. Composes with prior threads: - R6 Fresnel envelope + slot diffraction = narrower composite envelope - R10 link-budget primitives reused unmodified for air-side maritime - R7 multi-link consistency essential against superstructure jammers - R14 privacy framework transfers directly to crew-cabin monitoring Honest scope: best-case ignores vessel vibration (5-30 Hz, in-band with R10 gait frequencies), engine ignition noise, salt-spray, steel-surface multipath. Maritime gait-classification is harder than land. The romantic 'through-hull radar' is now explicitly debunked. The actual product roadmap is gasket-leakage sensing, surface detection, and predictive-maintenance audits. Coordination: ticks/tick-10.md, no PROGRESS.md edit.
2.8 KiB
Tick 10 — 2026-05-22 05:46 UTC
Thread: R11 (maritime / through-bulkhead sensing) Verdict: Physics scrutiny re-frames "through-bulkhead" to "through-seam" — the romantic submarine-radar vision is impossible at WiFi bands; the actual product category is gasket-leakage sensing.
What shipped
examples/research-sota/r11_maritime_propagation.py— pure-numpy skin-depth + lossy-dielectric saltwater + slot-diffraction physics for 7 maritime scenarios.examples/research-sota/r11_maritime_results.json— machine-readable predictions.docs/research/sota-2026-05-22/R11-maritime-sensing.md— research note with the physics, verdicts table, feasible/infeasible verticals, honest scope, composition with prior threads.
Headline (verdict table)
| Scenario | Verdict | Margin |
|---|---|---|
| Man-overboard surface @ 200 m | ✅ | +25 dB |
| Through 10 mm closed steel door | ❌ | -938 dB |
| Through cabin door 2 mm seam | ✅ | +31 dB |
| Through cabin door 5 mm seam | ✅ | +39 dB |
| Container w/ 30 mm vent slot | ✅ | +45 dB |
| Submarine 30 mm pressure hull | ❌ | -929 dB |
| Head 30 cm underwater | ❌ | -231 dB |
Key physics: steel skin depth = 3.25 µm at 2.4 GHz (impassable). Saltwater = 853 dB/m. The loophole is slot diffraction through gasket seams.
Feasible verticals catalogued
- Man-overboard surface detection (200 m range)
- Through-seam crew vitals (lone-watch monitoring without compromise)
- Container tamper detection (cargo security)
- Hatch-seal integrity audit (predictive maintenance)
- Engine room thermal-anomaly detection (via condensation envelope)
What this matters for the loop
R11 is the first thread that explicitly debunks a romantic 10-20y framing. The "through-bulkhead" terminology used in the original PROGRESS.md is physically wrong; the actual category is "through-seam". Replacing one vision with a more honest one is the kind of progress this loop is meant to surface.
Composes cleanly:
- R6 Fresnel envelope + slot diffraction = narrower composite envelope
- R10 link-budget primitives reused unmodified for air-side maritime
- R7 multi-link consistency essential for adversarial-resistant maritime
- R14 privacy framework transfers directly to crew-cabin monitoring
Honest scope landed
- Best-case ignores vessel vibration, engine ignition noise, salt-spray, multipath
- Vibration (5-30 Hz) is in-band with R10's gait frequencies — maritime gait-classification harder than land
- No GPS in steel compartments — alternative positioning needed
Coordination
ticks/tick-10.md. No PROGRESS.md edit. Branch research/sota-r11-maritime.
Remaining threads
R3 (cross-room re-ID), R4 (federated), R13 (contactless BP — likely negative-result candidate), R15 (RF biometric).
~6.3h to cron stop. 10 threads landed.