Research-Stack/6-Documentation/docs/underwater_shock_public_benchmark_2026-05-09.md

Underwater Shock Public Benchmark

Date: 2026-05-09

Status: PUBLIC_HISTORY_MODELING_PRIOR

Claim boundary: this note uses public historical underwater detonation records as free modeling data for shock-front, acoustic, bubble-pulse, reflection, and attenuation behavior. It is not a weapon-design document, not a charge-sizing guide, not target-vulnerability analysis, and not an operational placement model.

Why Sea-Based Records Are Useful

Underwater detonations are over-documented historical events. Humans made an enormous number of public visual, acoustic, radiological, naval, and historical records around them. That makes them useful as a low-cost validation source for general shock physics:

impulsive source
-> compressive water shock
-> pressure-release surface interaction
-> gas / vapor bubble expansion
-> bubble collapse and pulse train
-> acoustic propagation and attenuation
-> sediment / boundary reflection

For this stack, the value is not the weapon. The value is the medium response: water is dense, nearly incompressible, acoustically conductive, and creates a clean separation between the first shock front and the slower bubble-pulse sequence.

There is also a practical economic reason. A single serious underwater shock test chamber campaign would be expensive enough to erase the available research budget before the model had a chance to mature. Public historical records are therefore not just convenient; they are the only sane first validation lane. They let the stack fit waveform shape, timing, attenuation, and residuals without pretending that a private chamber test is feasible.

The rule is:

use public history to learn the medium response;
do not use the model to optimize destructive operation.

Public Historical Source Class

Useful public source classes:

• official history pages and fact sheets for underwater tests such as Operation Crossroads BAKER;
• medical / environmental / historical reviews that describe the test context;
• public technical reports that summarize shock-wave and bubble-pulse signal characteristics;
• open acoustic literature on underwater explosion sound and bubble-pulse timing;
• generic bubble-dynamics literature using Rayleigh-Plesset-type equations.

Examples:

• Atomic Heritage Foundation / National Museum of Nuclear Science & History, Operation Crossroads overview: https://ahf.nuclearmuseum.org/ahf/history/operation-crossroads
• NCBI Bookshelf, "Mortality of Veteran Participants in the Crossroads Nuclear Test", historical description: https://www.ncbi.nlm.nih.gov/books/NBK233207/
• OSTI technical report, "Signal characteristics of an underwater explosive acoustic telemetry system": https://www.osti.gov/biblio/6625697
• Acoustics Today, "The Sound from Underwater Explosions": https://acousticstoday.org/wp-content/uploads/2023/02/The-Sound-from-Underwater-Explosions-David-R.-DallOsto-Peter-H.-Dahl-and-N.-Ross-Chapman.pdf

Safe Modeling Variables

The benchmark lane should use observable signal variables:

t_arrival       acoustic arrival time
p_peak_proxy    observed or normalized peak pressure proxy
tau_decay       shock decay time constant
t_bubble_1      first bubble pulse arrival
t_bubble_k      later bubble pulse arrivals
A_k             relative pulse amplitudes
alpha_water     fitted propagation attenuation
Gamma_surface   pressure-release reflection coefficient
Gamma_bottom    fitted seabed / boundary reflection coefficient

The benchmark lane must not optimize:

charge mass
device design
placement depth
standoff distance
target damage
ship / hull response
casualty or infrastructure effects

Those fields are explicitly outside the modeling target.

Equations For The Benchmark Lane

The first useful abstraction is a normalized waveform model:

p_obs(t, r) =
  A_s(r) * exp(-(t - t_a) / tau_s) * H(t - t_a)
  + sum_k A_k(r) * B_k(t - t_b,k)
  + epsilon(t)

Where:

• t_a = r / c_w is acoustic arrival time in water.
• A_s(r) is a fitted initial shock-front amplitude proxy.
• tau_s is a fitted decay constant.
• B_k are bubble-pulse basis functions.
• epsilon(t) is residual sensor / environment error.

Attenuation can be tracked as:

A_s(r) = A_0 * G(r) * exp(-alpha_water * r)

Where G(r) is a declared geometry-spreading term, not a weapon calibration.

The bubble-motion receipt can use the Rayleigh-Plesset shape as a qualitative dynamics gate:

rho * (R * R_ddot + 3/2 * R_dot^2)
  = p_b(t) - p_infty(t) - 2*sigma/R - 4*mu*R_dot/R

For stack use, this equation says:

bubble pulse timing is a medium-response eigenmode,
not a second independent source event

Surface reflection can be modeled as a receipt gate:

p_reflected = Gamma_boundary * p_incident

For a pressure-release surface, Gamma_boundary is expected to be negative in the simplified acoustic model. The exact value remains a fitted receipt field.

Eigenvalue Connection

This public benchmark should sharpen the physical-shock eigen gap found in:

6-Documentation/docs/shockwave_eigenvalue_comparison_2026-05-09.md

Current repo state:

shock alignment / relaxation exists as a local stack mode
classical hydrodynamic shock equations exist but have zero-strength support

The underwater benchmark can add a measured public-data bridge:

Rankine-Hugoniot conservation
+ water acoustic attenuation
+ bubble-pulse eigenmode
+ boundary reflection
+ residual receipt

Gate

Minimum gate:

if source class is not public / archival:
  HOLD_SOURCE_PROVENANCE
elif requested variable is operational weapon design:
  QUARANTINE_OPERATIONAL_OPTIMIZATION
elif waveform lacks arrival/pulse/residual receipt:
  HOLD_SIGNAL_RECEIPT
elif fitted residual <= declared bound:
  ADMIT_PUBLIC_SHOCK_BENCHMARK
else:
  HOLD_RESIDUAL_TOO_LARGE

Stack Interpretation

This is the clean bridge:

stellar shock breakout:
  radiation escape through optical depth

underwater public shock:
  acoustic escape through dense medium + bubble pulse

rain/statolith shock:
  local displacement threshold in biological medium

All three share the same receipt grammar:

impulse -> medium transfer -> boundary condition -> local witness -> residual

That gives the stack a free, public, non-operational benchmark for the physical shock eigen lane.

Next Work

1. Add a PublicUnderwaterShockBenchmark receipt surface.
2. Add an economic feasibility field that records why public data is the primary lane before any lab/chamber validation.
3. Use only normalized waveform fixtures at first: arrival, relative pulse intervals, attenuation fit, and residual.
4. Add negative controls for missing source provenance, operational-variable requests, missing residuals, and overfit waveforms.
5. Re-run the physics eigen remapper after the benchmark exists and check whether Detonics & Shock Physics gains a nonzero support lane.