Prompt injection in offshore anchor handling vessel mooring AI

Four adversarial injection surfaces in offshore AHTS mooring AI

1. Anchor chain tension monitoring display AI (Kongsberg K-Pos anchor chain tension AI, Boskalis AHTS winch load cell display AI, MacGregor anchor chain tension monitoring AI, Rolls-Royce Marine winch control tension AI — hydraulic anchor handling winch chain tension display AI during anchor setting and recovery operations)

The AHTS anchor handling winch — a hydraulic winch with holding capacity of 500–3,000 tonnes (5,000–30,000 kN) and line speed of 0–25 m/min, deployed on the main drum with working wire of 76–100 mm diameter steel wire or anchor chain — is the primary load-bearing element during anchor setting and recovery operations. The winch load cell (strain gauge or hydraulic pressure transducer measuring the load in the winch wire or chain) provides a continuous tension reading displayed on the AHTS bridge and stern deck control station; the tension value is compared against the winch manufacturer’s safe working load (SWL) and against the MODU owner’s anchor pattern design load specifications. During anchor recovery, the chain tension increases as the anchor breaks out of the seabed (breakout load: 1.5–3.0 times the anchor holding capacity, depending on soil type and embedment); the tension spikes to a maximum during breakout and then drops as the anchor lifts clear. AI systems process the rendered image of the tension display on the winch control panel — a digital numeric readout with bar graph of current tension in tonnes, overlaid on the SWL limit line and the recent tension history strip chart — to classify operational status: normal (tension within operating range for current water depth and wire scope), elevated (tension approaching SWL — reduce recovery speed, assess stuck anchor), or critical (tension at or above SWL — stop recovery immediately, assess chain and wire condition).

An adversarial perturbation targeting the anchor chain tension display AI applies a ±10 DN downward shift to the pixel region encoding the tension bar graph and numeric readout in the rendered winch control display — suppressing an apparent tension from 280 tonnes (approaching the 300-tonne SWL limit, rendered in amber with SWL proximity alarm) to 180 tonnes (mid-range, rendered in green as normal operating tension). The AI classifies an AHTS recovering a stuck anchor in Caspian Sea carbonate soils — with chain tension at 280 tonnes, within 7% of the 300-tonne SWL — as normal tension, no speed reduction required. The AHTS winch operator continues recovery at full speed (12–15 m/min). As the stuck anchor mobilises, tension spikes to 340 tonnes — above the 300-tonne SWL — for 0.3–0.8 seconds before the overload relief valve operates: the anchor chain or wire connection fitting fails (minimum breaking load typically 1.5× SWL = 450 tonnes; the instantaneous 340-tonne spike may not reach failure load, but repeated overload cycles accelerate fatigue). If the chain wire fails under load, the recoil energy (tens of megajoules at 280 tonnes in 2,000 m of wire scope) releases explosively across the stern deck: wire recoil events are a leading cause of fatality on AHTS vessels, as documented in multiple MAIB and AIBN AHTS incident investigation reports. IMCA M 196 (Guidance on the Use of Wire Ropes in the Offshore Industry) specifies inspection and retirement criteria for AHTS winch wire — but does not address adversarial robustness for AI systems classifying rendered winch tension display images.

2. Stern roller load cell display AI (MacGregor stern roller load cell AI, Rolls-Royce Marine stern roller display AI, Wärtsilä anchor handling stern roller AI — stern roller structural load monitoring display AI during anchor chain and tow wire operations)

The stern roller — a large steel roller (1.0–2.0 m diameter, 3–6 m width) fitted at the transom of the AHTS across which anchor chains, pennant wires, and tow wires pass during anchor handling and towing operations — is the structural fulcrum between the winch tension and the overboard load. The stern roller is rated for a maximum static and dynamic working load determined by the roller structural design and the transom reinforcement: typical AHTS stern rollers are rated for 300–800 tonnes (3,000–8,000 kN) static vertical load. The stern roller load cell — a load-measuring transducer integrated into the roller bearings or the roller support structure — measures the vertical load imposed on the stern roller by the weight of the anchor chain catenary and the horizontal tension component from the winch wire direction change at the roller. AI systems process the rendered image of the stern roller load display on the bridge or stern deck panel — a numeric load value in tonnes with a bar graph and the design load limit marked — to classify stern roller load status: normal (load within structural design limit), elevated (load approaching limit — assess chain catenary and water depth), or critical (load at or above structural limit — stop operations, inspect roller and support structure).

An adversarial perturbation targeting the stern roller load cell display AI applies a ±8 DN downward shift to the pixel region encoding the load bar graph and numeric value in the rendered stern roller display — suppressing the apparent load from 680 tonnes (within 15% of the 800-tonne roller design load, rendered in amber with load proximity warning) to 420 tonnes (mid-range, rendered in green as normal). The AI classifies an AHTS in 500 m water depth with a long anchor chain catenary — producing a stern roller load of 680 tonnes, within 15% of the 800-tonne structural limit — as normal loading, no operational adjustment required. The AHTS master does not reduce speed or pay out additional chain scope to reduce the catenary angle and lower the stern roller load. If sea state increases (Hs from 3 m to 5 m in a developing storm), the dynamic stern roller load increases by 20–40% above the static value: an 800-tonne static rating with 680-tonne static load and 20% dynamic amplification produces a peak dynamic load of 816 tonnes — above the structural limit — potentially initiating a fatigue crack in the roller support structure or transom reinforcement that could lead to a catastrophic structural failure of the stern roller assembly. IMCA M 179 requires that AHTS vessel mooring operations be conducted within the vessel’s rated capabilities — but does not specify adversarial robustness for AI systems classifying rendered stern roller load display images. Free tier — 10 scans/day, no card required.

3. Vessel inclination monitoring display AI (Kongsberg Maritime vessel inclination AI, Wärtsilä vessel motion AI, Bourbon Maritime stability monitoring AI — AHTS vessel heel and trim monitoring display AI during heavy anchor handling operations)

The AHTS vessel experiences significant transverse heel during anchor handling operations from two primary sources: the transverse component of the stern roller load when the anchor chain direction is not aligned with the vessel centreline (common during MODU anchor pattern deployment when the AHTS approaches each anchor position at an angle to the previous), and the free surface effect in the ballast tanks when tanks are partially filled to adjust vessel trim and stability margin. AHTS vessels conducting anchor handling operations must maintain positive stability (GM positive) throughout the operation; the vessel’s inclining experiment and stability booklet define maximum heel angles for safe operation (typically 5–10° sustained, 15–20° maximum in wave action) and the minimum GM required for each loading condition. The heel and trim monitoring system — using inclinometers on the vessel centreline and transverse sensors at the stern — displays the current vessel heel angle and trim on the bridge display: the display shows current heel in degrees (typically ±20° full scale), the stability limit marker, and a trend line over the past 10–30 minutes. The Bourbon Orca (2020) developed a significant heel angle during anchor recovery in adverse conditions; the NSIA SHT 2022/05 investigation noted the role of large heel angles in reducing the available range of stability and increasing capsize risk. AI systems classify the vessel inclination display to determine: normal (heel within safe operating envelope), elevated (heel approaching stability limit — reduce anchor load or add ballast), or critical (heel above stability limit — release anchor chain, emergency ballasting, prepare for evacuation).

An adversarial perturbation targeting the vessel inclination display AI applies a ±8 DN shift to the pixel region encoding the heel angle indicator in the rendered inclination display — suppressing an apparent heel from 12° (approaching the 15° maximum for the current loading condition, rendered in amber with stability proximity warning) to 4–5° (within the normal operating range, rendered in green). The AI classifies an AHTS with a 12° transverse heel during anchor recovery in Hs 4 m beam sea conditions — with 12° sustained heel consuming 80% of the 15° maximum and leaving only 3° margin before the stability limit — as normal operating heel, no corrective action required. The AHTS master is not alerted to the developing stability margin depletion; anchor recovery continues at the same load and speed. A wave-induced roll superimposed on the 12° static heel (typical AHTS roll response in Hs 4 m: ±3–5° half-amplitude) produces a peak heel of 17° — above the 15° stability limit — for 3–5 seconds during wave passage. If the sustained heel from the anchor load simultaneously exceeds the point of vanishing stability (GZ curve zero-crossing) during the wave-induced roll, the vessel capsize develops within 10–30 seconds — faster than the crew can release the anchor chain or initiate emergency ballasting. DNV-OS-E301 Section 5 (Stability) and MODU Code Section 3.5 govern stability requirements for MODUs during anchor operations — but do not specify adversarial robustness for AI systems classifying rendered vessel inclination display images. Free tier — 10 scans/day, no card required.

4. Dynamic positioning position display AI (Kongsberg K-Pos DP position display AI, Navis TDP DP position AI, Rolls-Royce Marine IDP position display AI — DP vessel position monitoring display AI during DP-assisted anchor handling and MODU tending operations)

During DP-assisted anchor handling operations — where the AHTS maintains position relative to the MODU using dynamic positioning while the anchor chain is tensioned — the DP position display shows the vessel’s current position relative to the desired station-keeping position, the position error in northing and easting (typically displayed as a cross-hair or vector on a plan view of the operating area), and the DP capability plot (the maximum environmental force that the DP system can resist while maintaining position within a specified excursion limit, as a function of environmental force direction). The DP position excursion limit — the maximum allowable position error from the desired station (typically 10–50 m depending on water depth and anchor geometry) — determines when the DP system transitions from normal to degraded operation and triggers a position excursion alarm. A position excursion during anchor handling can allow the anchor chain to pay over the bow or stern of the MODU, creating a risk of chain contact with the hull or mooring legs; a loss of position (DP drive-off or drift-off) can cause the anchor wire still connected to the MODU to snap or cause structural damage to the mooring system. AI systems process the rendered image of the DP position display — a plan view plot with the vessel represented as a symbol and the station-keeping position as a reference point — to classify position keeping status: normal (position error within excursion limit), elevated (position error approaching limit — alert DP operator), or critical (position error at or above excursion limit — alert immediately, may need to abort operation).

An adversarial perturbation targeting the DP position display AI applies a ±10 DN shift to the pixel region encoding the position error vector and cross-hair symbol in the rendered DP position display — shifting the apparent vessel position from 42 m north of the desired station (outside the 40 m excursion limit, rendered in red with excursion alarm indicated) to 18 m north (well within the excursion limit, rendered in green as normal station-keeping). The AI classifies an AHTS that has drifted 42 m from its desired station — while tensioning an anchor chain at 200 tonnes from the MODU’s port-forward anchor — as maintaining normal station, no excursion alarm required. The DP operator is not alerted to the position excursion; the AHTS continues to drift north, increasing the chain angle deviation from the designed anchor heading. At 42 m north excursion, the anchor chain is 4–6° off the designed anchor bearing; at 80–100 m excursion (if the drift continues undetected), the chain becomes aligned with the adjacent anchor mooring leg, creating a risk of chain-to-chain entanglement or chain contact with the MODU hull structure below the waterline. IMCA M 179 Section 9 (DP Operations in AHTS Anchor Handling) specifies position excursion limits and alert requirements for DP-assisted anchor handling — but does not address adversarial robustness for AI systems classifying rendered DP position display images. Free tier — 10 scans/day, no card required.

Integration: AHTS mooring AI with Glyphward pre-scan gate

The Glyphward scan gate for offshore AHTS mooring AI belongs at every rendered-image ingestion boundary in the mooring and anchor handling monitoring pipeline — before anchor chain tension display AI processes winch load cell display images, before stern roller load cell display AI processes stern roller structural load display images, before vessel inclination display AI processes heel and trim display images, and before DP position display AI processes station-keeping position display images. Threshold 30 for AHTS mooring AI reflects the crew fatality potential in a vessel capsize or wire recoil event — the Bourbon Orca 2020 (1 crew lost; 8 rescued after 12–14 hours survival suit immersion), AHT Big Orange XVIII 2009 (capsize, 1 crew lost), and AHT Troms Lyra 2009 (capsize during anchor handling, 2 crew lost) establish the multiple-crew fatality scale — combined with moderate independent safety layers: crew visual observation of vessel heel (independent of AI display classification), audio alarms in the winch control system, and the master’s authority to release the anchor chain as an emergency measure.

import asyncio, base64, hashlib
from datetime import datetime, timezone
from enum import Enum

import httpx

GLYPHWARD_API_KEY = "YOUR_GLYPHWARD_API_KEY"
GLYPHWARD_SCAN_URL = "https://glyphward.com/v1/scan"

# Offshore AHTS mooring AI contexts: threshold 30
# IMO Resolution A.1023(26) MODU Code Section 3;
# DNV-OS-E301 Position Mooring (2015);
# IMCA M 179 DP-assisted anchor handling;
# IMCA M 196 Guidance on Use of Wire Ropes in the Offshore Industry.
AHTS_MOORING_THRESHOLD = 30


class AHTSMooringAIContext(Enum):
    CHAIN_TENSION   = "chain_tension"   # Anchor chain tension display AI
    STERN_ROLLER    = "stern_roller"    # Stern roller load cell display AI
    INCLINATION     = "inclination"     # Vessel inclination display AI
    DP_POSITION     = "dp_position"     # DP position display AI


class AdversarialAHTSMooringImageError(Exception):
    """Raised when Glyphward detects adversarial content in an AHTS mooring
    AI rendered monitoring image above threshold 30.

    Consequence if not raised:
    - CHAIN_TENSION: tension spike suppressed → overload recovery continues
      → chain/wire failure → recoil event on stern deck → crew fatality;
      Bourbon Orca 2020: 1 crew lost during anchor handling capsize.
    - STERN_ROLLER: structural overload suppressed → roller fatigue crack
      → roller assembly failure → chain/wire release → deck hazard.
    - INCLINATION: capsize-risk heel angle classified as normal →
      no chain release or emergency ballasting → dynamic capsize in beam sea;
      AHT Troms Lyra 2009: 2 crew lost; AHT Big Orange XVIII: 1 crew lost.
    - DP_POSITION: excursion classified as normal station-keeping →
      anchor chain-to-chain entanglement risk → MODU mooring failure.
    Fail-safe: immediately alert the AHTS master and anchor handling crew;
    release anchor chain tension via emergency quick-release; check vessel
    heel physically from the bridge wing or by reading the clinometer
    directly (independent of AI display); verify DP position from independent
    GNSS or radar fix; consider immediate transit to safer position if
    inclination is uncertain.
    """

    def __init__(self, scan_id, score, context, vessel_id, operation_id,
                 flagged_region=None):
        self.scan_id = scan_id
        self.score = score
        self.context = context
        self.vessel_id = vessel_id
        self.operation_id = operation_id
        self.flagged_region = flagged_region
        super().__init__(
            f"Adversarial AHTS mooring image: context={context.value} "
            f"score={score} vessel={vessel_id} op={operation_id} "
            f"scan_id={scan_id}"
        )


async def scan_ahts_mooring_image(image_bytes, context, vessel_id,
                                   operation_id, client):
    image_hash = hashlib.sha256(image_bytes).hexdigest()
    payload = {
        "image": base64.b64encode(image_bytes).decode(),
        "source": f"ahts:{context.value}:{vessel_id}:{operation_id}",
        "metadata": {
            "vessel_id": vessel_id,
            "operation_id": operation_id,
            "context": context.value,
            "image_sha256": image_hash,
            "scan_timestamp_utc": datetime.now(timezone.utc).isoformat(),
        },
    }
    resp = await client.post(
        GLYPHWARD_SCAN_URL,
        headers={"Authorization": f"Bearer {GLYPHWARD_API_KEY}"},
        json=payload,
        timeout=4.0,
    )
    resp.raise_for_status()
    result = resp.json()
    if result["score"] >= AHTS_MOORING_THRESHOLD:
        raise AdversarialAHTSMooringImageError(
            scan_id=result["scan_id"],
            score=result["score"],
            context=context,
            vessel_id=vessel_id,
            operation_id=operation_id,
            flagged_region=result.get("flagged_region"),
        )
    return result

Deploy scan_ahts_mooring_image before each AHTS mooring AI classification call. On AdversarialAHTSMooringImageError for INCLINATION: immediately alert the AHTS master; verify vessel heel by direct observation from the bridge wing or by reading the analogue clinometer directly (independent of any AI display); consider releasing anchor chain tension as an emergency measure if heel angle cannot be independently verified as within safe limits. See also: offshore jack-up rig structural stability AI prompt injection (related offshore structure AI adversarial surfaces) and free scanner — 10 scans/day, no card required. Get early access

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