In 2023, a wind farm developer clearing 200+ UXO items (primarily 250 lb bombs) from a 50 km² site transitioned from traditional detonation to a commercial deflagration system (using a shaped thermite charge to initiate low-order burning). Using a network of 6 autonomous hydrophones, they measured:
As offshore wind expands into deeper waters (e.g., floating wind at 100m+ depths), new acoustic challenges emerge.
Even in a pure deflagration, hot gases expand rapidly. As the bubble collapses, it can generate secondary pressure pulses that, while far weaker than a detonation bubble pulse, may still be measurable. Characterisation must distinguish between the primary combustion source and secondary cavitation collapse. In 2023, a wind farm developer clearing 200+
| Metric | High-Order Detonation | Low-Order Deflagration | | :--- | :--- | :--- | | | 240–260 dB | 200–220 dB | | Rise Time | < 1 µs | 5–50 ms | | Dominant Frequency | 100 Hz – 10 kHz | 20 – 500 Hz | | Injury Zone (PTS) | 1 – 3 km radius | 50 – 300 m radius | | Behavioral Disturbance Zone | 10 – 50 km radius | 500 m – 3 km radius | | Risk of Barotrauma | High (lung/ear rupture) | Negligible | | Risk of Physical Displacement | Very High (mass strandings) | Low |
As we expand our offshore energy footprint, adopting these "quieter" disposal methods is essential for sustainable marine management. As the bubble collapses, it can generate secondary
is a supersonic combustion process (shock wave velocity > 1000 m/s) where the reaction front is coupled with a shock wave. The transition from solid explosive to hot gas occurs in microseconds, generating a discontinuous pressure rise (a shock front). Underwater, this produces a primary shock wave followed by oscillating bubble pulses. The peak sound pressure levels (SPLs) from a small UXO detonation can exceed 250 dB re 1 µPa @ 1m, with frequencies spanning from tens of Hz to over 50 kHz.
Underwater acoustic characterization of Unexploded Ordnance (UXO) disposal focuses on measuring the sound pressure levels (SPL) and frequency content produced when neutralized via deflagration rather than high-order detonation. 🎯 Primary Objective The goal is to quantify the acoustic footprint is a supersonic combustion process (shock wave velocity
Despite its advantages, deflagration is not a universal panacea. Acoustic characterisation reveals several challenges: