AKA: Castor 4A;TX-780. Status: Out of production. Number: 304 . Thrust: 478.30 kN (107,526 lbf). Gross mass: 11,578 kg (25,525 lb). Unfuelled mass: 1,457 kg (3,212 lb). Specific impulse: 266 s. Specific impulse sea level: 237 s. Burn time: 56 s. Height: 9.20 m (30.10 ft). Diameter: 1.02 m (3.34 ft).
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% aluminum). 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. Total Impulse: 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.
Thrust (sl): 426.200 kN (95,814 lbf). Thrust (sl): 43,457 kgf. Chamber Pressure: 47.20 bar. Area Ratio: 9.29. Propellant Formulation: HTPB.