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Centaur C

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Centaur Credit: © Mark Wade

Status: Study 1960. Thrust: 133.45 kN (30,000 lbf). Gross mass: 15,600 kg (34,300 lb). Unfuelled mass: 1,996 kg (4,400 lb). Specific impulse: 425 s. Burn time: 430 s. Height: 9.14 m (29.98 ft). Diameter: 3.05 m (10.00 ft). Span: 3.05 m (10.00 ft).

Early Centaur Guidance System

The Centaur guidance system was all-inertial, consisting primarily of a four-gimbal all-attitude inertial platform and a general purpose serial digital computer with a magnetic drum memory. The airborne guidance program was written onto the drum memory from a punched paper tape along with a pre-flight calibration and alignment program for trimming and aligning the platform prior to launch.

For the geosynchronous equatorial orbit mission the Centaur guidance system performed the following functions:

During the Atlas booster phase, the vehicle pitch program was generated by the Atlas autopilot; however, the guidance system monitored the vehicle position and velocity and generated the booster staging discrete as a function of vehicle acceleration. For the Atlas sustainer stage the guidance system generated vehicle steering signals, which were used to orient the thrust vector so as to reduce the position and velocity dispersions generated during the open-loop booster stage. The sustainer engine cutoff command was also given by the guidance system.

After separation of the Centaur stage from the Atlas booster, the Centaur guidance system controlled the vehicle during each of the succeeding three phases of powered flight necessary to place the vehicle in its final orbit. The guidance system provided steering and cutoff signals to the Centaur autopilot during the powered phases of flight and also provided an attitude reference to the autopilot prior to the second and third firings of Centaur in order that the vehicle assumed the proper attitude prior to thrust initiation. The following was a typical 3 start flight sequence:

• T+0 to 15 sec. Vertical rise and roll to desired azimuth
• Time dependent pitch program to booster staging (booster staging initiated by an accelerometer when acceleration reached 5.8 g's.
• At Beco (Booster engine cut-off) + 15 seconds, the Centaur tank insulation panels were jettisoned. The sustainer phase was flown at a constant inertial attitude
• At Beco +63 seconds, the payload shroud was jettisoned. The sustainer phase was terminated by propellant depletion. At Seco (Sustainer engine cut-off) the vehicle continued in a constant inertial attitude while the Atlas continued a low acceleration in the vernier solo phase.
• At Seco + 9.5 seconds the Centaur main engine prestart (chilldown) was initiated
• Centaur separation and ullage rocket firing was initiated at Veco (Vernier engine out-off). This first ullage rocket firing period was 14.5 sec.
• First Centaur main engine firing; a constant pitch rate was maintained until main engine cutoff, at which point Centaur and its payload were in a low earth parking orbit.
• The Centaur was orientated "tail to sun" in parking orbit for the first coast period. Approximately 300 seconds prior to the second main engine start, the vehicle was re-oriented with the firing direction rockets starting 42 seconds prior to the main engine. Engine prestart was initiated 20 seconds prior to main engine start.
• Prior to the second main engine burn, the vehicle was again oriented "tail to sun" for the second coast period. The vehicle was re-oriented for the third firing direction, with the ullage rockets starting 50 seconds prior to the main engine. Prestart was initiated 20 seconds prior to the main engine.
• Third main engine burn was followed by payload separation

Structural considerations of the configuration limited the product of the angle of attack and dynamic pressure, q, to approximately 67 kN/m^2 with 2-sigma winds at Cape Canaveral. The maximum permissible longitudinal and lateral acceleration factors were 7.0 g and 1.0 g, respectively.

Cost $ : 20.300 million. No Engines: 2.