The composition of M28 propellant used in the M55 rocket is listed in Table 2-1. It is a double-base3 propellant with a lead stearate burn-rate modifier. The propellant is contained within a cellulose acetate inhibitor that has been plasticized with dimethylphthalate. The purpose of the inhibitor is to limit propellant burning along the outer surface of the propellant during motor firing. The hazard classification of the separated rocket motors as determined by following the Department of Defense Ammunition and Explosives Hazard Classification Procedures, TB 700–2 (DoD, 1998), affects the packaging requirements for the rocket motors, the number of rocket motors that may be transported off-site in a given shipment configuration, and the number of rocket motors that may be stored in a given location before disposal. The hazard classification of the assembled M55 rockets in their shipping and firing tubes (SFTs) for storage and transportation is currently 1.2.1, which means that they present a non–mass explosion and fragment-producing hazard. BGCAPP intends to apply for a 1.3 hazard classification, which would mean that they present a mass fire and minor blast or fragmentation hazard, to cover shipping and handling of the separated rocket motors (DoD, 1998). Table 2-2 lays out the hazard classifications that are applied to explosive materials.

  Table 2-1 Nominal Composition of M28 Propellant

Component Weight Percent Purpose
Nitrocellulose 60 Energy source
Nitroglycerin 23.8 Energetic plasticizer
Triacetin 9.9 Casting solvent
Dimethylphthalate 2.6 Plasticizer
Lead stearate 2.0 Burn-rate modifier
2-Nitrodiphenylamine 1.7 Stabilizer

  SOURCE: CMA, 2005.


   Table 2-2 Hazard Classifications Applied to Explosive Materials

Hazard Classification Hazard
1.1 Mass explosion
1.2 Non-mass explosion, fragment-producing
1.3 Mass fire, minor blast, or fragment
1.4 Moderate fire, no blast, or fragment
1.5 Explosive substance, very insensitive (with mass explosion hazard)
1.6 Explosive article, extremely insensitive

  SOURCE: DoD, 1998.


Finding 2-1. The hazard classification of the rocket motors has not been determined. The classification will directly affect packaging, transportation, and storage requirements for off-site disposal options.


3The term double-base connotes that there are two active constituents in the propellant. In the case of the M28 propellant, they are nitrocellulose and nitroglycerin.

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