Abstract A method is disclosed for curing a nitrogen-fluorine propellant in an electromagnetic alternating field. The propellant is cast into thin walled-titanium tubes of predetermined size and with a graphite-epoxy overwrap. When the propellant-filled tubes are exposed to electromagnetic radiation, the propellant is cured to a grain in about 30 minutes as compared to about 5 days required for thermal curing at 135 DEG F. The disclosed method of curing is achieved because of the permeability of the overwrapped tubes to microwaves. The grain cured by the disclosed method acquires the desired mechanical properties, particulary, a greater uniformity, as indicated by a higher Shore hardness value, within a considerably shorter time period. The greater uniformity of mechanical properties throughout the propellant grain is particularly essential for this application because of the small quantity of propellant and the thrust repeatability necessary from one micromotor to another in the Maneuver Motor Array. Accelerated rate of cure is particularly advantageous because of the shortened turn-around time for the motor casting equipment. This is particularly desired because of the large number of motor tubes which must be cast for each array (112 tubes per array).
An accelerated curing method for curing solid propellant in propellant tubes for use in micromotors, said method comprising casting a difluoroamino-plasticized, electromagnetic energy curable propellant composition into thin wall-titanium tubes of predetermined size and with a graphite-epoxy overwrap; and thereafter, subjecting said thin walled-titanium tubes containing said propellant composition for a predetermined period of about 30 to about 35 minutes to electromagnetic energy with a predetermined frequency range of 30 to 30,000 MHz to effect curing of said propellant composition to yield cured grains in said tubes, said grains having a uniformity of measured Shore hardness from about 30 to about 35 throughout the propellant grains.
Claim 2
Dependent Claim
106 words
An accelerated curing method for curing solid propellant in propellant tubes for use in micromotors, said method comprising casting a difluoroamino-plasticized, electromagnetic energy curable propellant composition into thin wall-titanium tubes of predetermined size and with a graphite-epoxy overwrap; and thereafter, subjecting said thin walled-titanium tubes containing said propellant composition for a predetermined period of about 30 to about 35 minutes to electromagnetic energy with a predetermined frequency range of 30 to 30,000 MHz to effect curing of said propellant composition to yield cured grains in said tubes, said grains having a uniformity of measured Shore hardness from about 30 to about 35 throughout the propellant grains.
Claim 3
Dependent Claim
19 words
The accelerated curing method of claim 1 wherein said electromagnetic energy has the predetermined frequency of about 2450 MHz.
Claim 4
Dependent Claim
92 words
The accelerated curing method of claim 2 wherein said difluoroamino-plasticized, electromagnetic energy curable propellant composition as cast into said tubes is comprised of about 5.20 weight percent copolymer binder of polyethyl acrylate/acrylic acid (95/5), of about 29.47 weight percent plasticizer of tris[1,2,3-bis(1,2-difluoramino)ethoxy] propane, of about 1.33 weight percent curing agent of 4,5-epoxycyclohexylmethyl-4',5'-epoxycyclohexyl carboxylate, of about 1.00 weight percent carbon black to enhance propellant's ability to absorb heat in an ultrahigh frequency field and to eliminate combustion instability in the cured propellant grain, and of about 63.00 weight percent oxidizer of ammonium perchlorate.
Claim 5
Dependent Claim
32 words
The accelerated curing method of claim 3 wherein said tubes have predetermined sizes that include outside and inside diameters of about 0.412 and 0.361 inch and wall thicknesses of about 0.026 inch.