Slow pace

The Titan IVA-Centaur that left Pad 41 on 3 May 1994 had an unenviable record on the ground. It was rolled out from the Vertical Processing Facility on 14 June 1991, only to be rolled back a year later when inspections found corrosion in the joints of its solid rocket motors. After the investigation into a Centaur failure in August 1992 it was rolled out again, only to be held up by a repeat of the Centaur problem in March 1993. In July 1993, in order not to exceed the 18-month limit for solid rocket motors to sit in the open, it was rolled back due to the late delivery of its payload. Following the loss of a Titan in August 1993 due to the explosion of one of its solid rocket motors, a segment in the grounded vehicle containing one of the suspect repairs was replaced.16,1V8

In contrast, the Titan IVA launched from Canaveral on 27 August 1994 set a record for its rapid preparation, having spent ''only 91 days'' on the pad - which the Air Force said was a sign that the vehicle was ''acquiring maturity".19,20,21 Indeed, on 22 December 1994 the Titan IVA that lifted off from Pad 40 marked the fourth launch in the 12 months since the loss in 1993, all of which had been from the Cape. Another launch on 6 November 1995 deployed a Milstar, the most advanced communications satellite yet developed by the Department of Defense.2V3

The first Titan IVA to leave from SLC-4E since the loss in August 1993 lifted off on 5 December 1995 with a classified payload.24 This hiatus had been to update the pads for the new solid rocket motors that were to be used on the Titan IVB.25

A Titan IVA-Centaur on Pad 40 at Canaveral.

A Titan IVA-Centaur awaits launch on 6 November 1995 with the Milstar DFS 2 satellite.

A Milstar satellite stowed in its shroud and (artist's illustration) in its deployed configuration in orbit.

The Titan IVB

In view of the problems with the solid rocket boosters of the Titan 34D and Shuttle, the Air Force had given the contract for a Solid Rocket Motor Upgrade to Hercules (later Alliant Techsystems).34,3S Unlike the seven-segment steel-cased motors of the Titan IVA, the new ones had filament-wound composite casings and had just three segments to reduce the number of joints. In addition, they were of greater diameter in order to accommodate more propellant and the motor had a hydraulic actuator for thrust-vectoring.36^7 The core stage of the Titan IVB ignited at T+130 seconds, some 15 seconds before the solids were jettisoned.38 It could exceed its predecessor's payload by 25 per cent, increasing the low-orbit capacity from 17.7 to 22.3 tonnes,

A Milstar satellite stowed in its shroud and (artist's illustration) in its deployed configuration in orbit.

The final Titan IVA

When the final Titan IVA-Centaur lifted off from Canaveral on 12 August 1998, it became the second one to be lost.26^7 The telemetry established that the power from the battery to the guidance system had faltered at T + 39.4 seconds.28 The outage was only for a fraction of a second but it was long enough to cause the guidance system to lose its horizon and, when the power was restored, the system had issued an erroneous attitude correction that pitched the vehicle over at an altitude of 20,000 feet, which in turn had triggered the self-destruct system at T + 41.3 seconds.29 The investigation traced the fault to a defect in an electrical harness in the second stage of the core, in which eroded insulation caused a momentary short cir-cuit.30,31,32 This $1 billion mishap lost the National Reconnaissance Office a Mercury signals-intelligence satel-lite.33

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