Used in Delta 6900; Atlas IIAS; Castor 4A. Castor 4A began the development of a program to improve Delta performance by 11%. This was done by replacing the old fuel with HTPB propellant. The TX780-0, with an 11 degree canted nozzle is used in the ground ignited booster. The TX780-1, with a 7 degree cant, and the TX780-2, (11degree cant) are ignited at altitude. The TX780-3 & 4 were developed as the ground and altitude ignited boosters, respectively. The TX780-5, a straight nozzle, powers OSC's Prospector suborbital vehicle.. First Flown: February 14, 1989, Delta 184. Flown: 163 to end of 1993 (100% success). Propellant Type: TP-H8299 HTPB Polymer (20% aluminium). Shape: cylindrical, with 76% web fraction. transitions to four longitudinal slots. Tailored for ignition and burn-out thrust to be similar to Castor 4. Mass Fraction: 0.874 for standard loading. Burn Time: 53.1 sec web. Thrust (kN, sea level, 21Celsius): 476.661 maximum with a n average of 436.736. Isp: 237.6 sec sea level at 21 Celsius. Itotal: 23,846 kNs sea level at 21 Celsius. Pressure: 46.60 atm average with a maximum of 49.86 atm at sea level. at 21 Celsius. Nozzle Throat Diameter: 278.6 mm. Nozzle Materials: carbon-phenolic. Casing Line: standard HT polymer. Igniter Type: pyrogen, head-end.