Controlled autoignition propellant systems
View Patent ↗Solid propellant systems include a main propellant and a secondary propellant in contact with the first propellant that exhibits autoignition temperatures of at least about 100° F. lower than the autoignition temperature of the main propellant. The secondary propellant of the present invention is most advantageously employed with conventional AP-containing solid propellant formulations as the main propellant, especially formulations containing both AP, an energetic solid, and a binder. In especially preferred forms, the secondary propellant will include a nitramine which is at least one selected from nitroguanidine (NQ), cyclotrimethylene trinitramine (RDX) and cyclotetramethylenetetranitramine (HMX), and a binder which is at least one selected from HTPB, HTPE or glycidyl azide polymer (GAP). Most preferably, the secondary propellant will include a combination of nitramines which includes NQ and one of RDX or HMX.
1. A solid rocket motor propellant system comprising:
(a) an ammonium perchlorate-based main propellant which comprises, based on the total weight of the main propellant, between about 65 to about 92 wt. % ammonium perchlorate (AP), between about 8 to about 25 wt. % of an inert binder, and optionally, between about 5 to about 20 wt. % of aluminum powder; and
(b) a secondary propellant in the form of a strip in localized contact with said main propellant of a compressed mass of a composition which comprises, based on the total weight of the secondary propellant,
(i) between about 50 to about 95 wt. % of at least one nitramine selected from the group consisting of nitroguanidine (NQ), cyclotrimethylenetrinitramine (RDX) and cyclotetramethylenetetranitramine (HMX), and
(ii) between about 5 to about 50 wt. % of at least one binder selected from the group consisting of hydroxyl-terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP), wherein said at least one nitramine and said at least one binder being present in amounts sufficient for the secondary propellant to exhibit an autoignition temperature which is at least about 100° C. lower than the autoignition temperature of the main propellant.
2. The propellant system of claim 1 , wherein said secondary propellant comprises said nitroguanidine (NQ) and at least one additional nitramine which is said cyclotrimethylenetrinitramine (RDX) or said cyclotetramethylene tetranitramine (HMX).
3. The propellant system of claim 1 , wherein said at least one binder is present in an amount between about 10 to about 35 wt. %.
4. A solid rocket motor propellant system comprising:
(a) an ammonium perchlorate-based main propellant which comprises, based on the total weight of the main propellant, between about 65 to about 92 wt. % ammonium perchlorate (AP), between about 8 to about 25 wt. % of an inert binder, and optionally, between about 5 to about 20 wt. % of aluminum powder; and
(b) a secondary propellant in localized contact with said main propellant having an autoignition temperature which is at least 100° C. lower than the autoignition temperature of the main propellant, said secondary propellant being in the form of a strip of a compressed mass of a powdered composition which comprises, based on the total weight of the secondary propellant;
(i) between about 30 to about 55 wt. % of nitroguanidine (NQ);
(ii) between about 25 to about 50 wt. % of at least one additional nitramine selected from the group consisting of cyclotrimethylenetrinitramine (RDX) and cyclotetramethylene tetranitramine (HMX), and
(iii) between about 5 to about 50 wt. % of a binder which is at least one selected from the group consisting of hydroxyl-terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP).
5. The propellant system as in claim 4 , wherein said secondary propellant consists essentially of said NQ in an amount between about 40 to about 50 wt. %, and said HMX in an amount between about 35 to about 40 wt. %, with the balance being said HTPB.
6. The propellant system as in claim 4 , wherein said secondary propellant consists essentially of said NQ in an amount between about 35 to about 40 wt. %, and said HMX in an amount between about 30 to about 35 wt. %, with the balance being said GAP.
7. The propellant system as in claim 1 or 4 , wherein said secondary propellant is in the form of a ring of said compressed mass of said composition in localized contact with said main propellant.