In summary, deterioration of the rocket propellant in the M55s is potentially a serious hazard to continued safe storage of the chemical agent and munitions stockpile. Most extant estimates of the dates when this danger might arise are at or beyond the end points of the current schedule for destruction of the stockpile. However, at least one analyst puts the date of potential danger much earlier. All of these estimates are very uncertain, based as they are on old and sparse data. Controversy is evident about the reaction kinetics and the effectiveness of the 2-NDPA stabilizer. Moreover, the schedule for the disposal program is also uncertain and it could easily slip into or beyond the dates at which significant depletion of stabilizer is now predicted.

It is the committee's conclusion that the consequences of an M55 autoignition are too great for this level of uncertainty to be tolerated. Thus, the committee recommends that the Army undertake a new and definitive study of M55 rocket propellant, including new sampling if that is appropriate, to develop more reliable assessment of these propellants. This study should address all the issues raised by the studies summarized above and by this discussion, including intralot and intragrain variations; degradation kinetics; the effectiveness of both 2-NDPA and its daughter products as stabilizers; the fate of the few hundred rockets manufactured with low stabilizer levels; and the autoignition characteristics of the M55 grain, given its actual configuration.

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