First failure

On 2 August 1993 a Titan IVA without an upper stage lifted off from SLC-4E and exploded at T+ 101 seconds, just a few seconds before the core stage was to ignite.9 The video showed a normal ascent until a light-coloured ring of smoke puffed outward from the vehicle moments before it was transformed into a fireball. The investigation blamed a faulty repair to one of the solid rocket motors that had permitted a burn-through of the casing.10,n The telemetry indicated pitch and yaw perturbations immediately prior to the explosion due to gas venting from this hole. After the slurry mix of propellant had been poured into its casing, each segment was capped by a rubbery material designed to retard erosion of the field joint. In cases where a void formed between this 'restrictor' and the propellant (a flaw referred to as debonding) this was repaired. After a motor containing a repaired segment on a Titan 34D exploded in 1986, the repair procedure was revised and had since given no cause for concern. In this case, however, the repair had been by far the most extensive - involving an area of some 5,000 square inches of the restrictor's surface compared to the more typical 350 square inches. As there had been multiple voids, it had been decided not to repair each void individually but instead to apply a large pie-shaped patch. It had been believed that when the ignition system fired a jet of flame down the bore of the stacked motor the pressure would seal this cut, but a test undertaken for the investigation showed that the transient pressures would actually open it.12 This had evidently allowed a fast flame front to burn through the 10-centimetre-thick steel casing. It was decided to remain within known parameters, and

Titan IVA models (left to right): Titan IVA-IUS, the 1st vehicle of this type, which was launched on 14 June 1989 with a DSP satellite; Titan IVA on 8 June 1990 with four satellites for the Naval Ocean Surveillance System; Titan IVA-Centaur awaits launch on 7 February 1994 with the Milstar DFS 1 satellite.

Titan IVA models (left to right): Titan IVA-IUS, the 1st vehicle of this type, which was launched on 14 June 1989 with a DSP satellite; Titan IVA on 8 June 1990 with four satellites for the Naval Ocean Surveillance System; Titan IVA-Centaur awaits launch on 7 February 1994 with the Milstar DFS 1 satellite.

not attempt to repair voids larger than those that had been shown to be safe. As an expedient to resume flying as soon as possible, all repaired segments (a total of 14) were removed from already stacked motors and placed in storage to await inspection.

Initially, Titan IVA launches from Canaveral had utilised Pad 41, but following the launch of the final Commercial Titan from Pad 40 in 1992 with Mars Observer this pad was refurbished. Its first use, on 7 February 1994, marked the return to service of the Titan IVA after the loss in August 1993.

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