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Explosives

Explosives are entered at the PES by hazard division and weight. Each division drives an independent calculation path — blast, fragmentation, and thermal results are computed per division, and then the engine takes the largest as the governing required distance.

Learning objectives

By the end of this lesson you should be able to:

  • Enter Net Explosive Weight (NEW) by division correctly
  • Predict how multiple divisions at one PES interact in the final result
  • Identify when an explosive change requires re-running analysis

Hazard divisions under DCMA​

DCMA recognizes six hazard divisions:

DivisionHazard
1.1Mass explosion hazard
1.2.1Non-mass explosion, fragment-producing — large fragments
1.2.2Non-mass explosion, fragment-producing — medium fragments
1.2.3Non-mass explosion, fragment-producing — small fragments
1.3Mass fire hazard, with minor blast or fragment
1.4Minor explosion hazard

The hazard division shapes which calculation paths the engine walks for a given quantity. A 1.1 quantity drives a blast-led path with potential fragmentation contribution; a 1.2 quantity emphasizes fragmentation; 1.3 emphasizes thermal. The engine treats each division as its own analysis and aggregates only at the end.

Entering NEW​

Every division accepts a Net Explosive Weight (NEW) value at minimum. Conventions:

  • Enter only the divisions that are being sited at the PES — leave others empty rather than zero where the calculator distinguishes the two (zero will still calculate, but will generate unnecessary calculations)
  • Match units to the criteria set's expected unit, each criteria uses its native units of measurement (DCMA expects pounds; verify in the calculator)
  • The calculator does not combine HD NEWs. This is a siting tool and applicable HD quantities actually present are the responsibility of the stockpile management.

Supporting weights beyond NEW​

Some hazard divisions take more than just NEW. The criteria treat certain hazards as a function of multiple weight inputs — a single bulk NEW is not enough information to evaluate them — so the calculator surfaces additional weight fields specifically for those divisions.

Under DCMA:

DivisionRequired weights
1.1NEW
1.2.1NEW, MCE (Maximum Credible Event)
1.2.2NEW
1.2.3NEW, MCE, Parenthetical Distance
1.3NEW
1.4NEW

For 1.2.1, the MCE captures the largest single-event detonation expected at the PES — distinct from the total NEW present, which may be larger because not every round contributes to a single credible event.

For 1.2.3, the Parenthetical Distance is an additional input the criteria require to resolve specific fragmentation rules. The calculator presents it as its own field — leaving it blank when 1.2.3 is in play prevents the analysis from completing.

The calculator surfaces only the weight fields that apply to the division. Pick a 1.1 NEW and you see one input; pick 1.2.3 and you see three.

Multiple divisions at one PES​

When a PES carries explosives from more than one division, the engine computes a result per division. Each one walks its own path and produces its own required distance, after its own hazard-specific reductions. The final required distance is the largest across all divisions.

This is why a small 1.1 quantity can be governed by a much larger 1.3 quantity at the same PES — both run, both produce required distances, and the engine takes the larger. But all results are returned by the engine, so you have full visibility on which HD is driving the requirement.

Re-running after explosive changes​

Re-run analysis after editing explosives so the new values flow through the criteria path into the result.

Try it​

At a single PES, enter 100 lb of 1.1 and observe the required distance. Now add 1,000 lb of 1.3 to the same PES (without removing the 1.1) and re-run. Note that:

  1. The 1.1 result stays the same — its analysis is independent of the 1.3
  2. A new 1.3 result appears, with its own required distance
  3. The governing required distance now reflects whichever division produces the larger value