Tim Furniss/LONDON
Launch of the STS 98/ Atlantis Space Shuttle mission to the International Space Station (ISS) has been delayed from 19 January until 6 February at the earliest due to ongoing solid rocket booster (SRB) cabling problems on the Shuttle fleet.
Atlantis' payload, the US laboratory module Destiny, has been removed from the orbiter, and the Shuttle stack was due to be rolled back to the vehicle assembly building on 19 January.
The STS 98 delay will push back the scheduled 1 March launch of the next Shuttle ISS mission, STS 102/Discovery, already postponed by three weeks. Discovery will collect the first ISS expedition crew and deliver the second crew.
The initial SRB cable inspection was ordered after one of the aft separation devices on one of the two SRBs failed to fire on mission STS 97 Endeavour on 30 November. A back-up device fired successfully. There are two forward and two aft pyrotechnic devices per SRB. The system is designated as a "Criticality One" component as its failure could destroy the Shuttle.
The inspection of Atlantis will concentrate on 36 cables on the SRBs that are not directly associated with the separation systems, says NASA. The cables run down the side of each SRB in tunnels from the forward to the aft skirt, carrying commands and data to support the operation of the boosters. Engineers will conduct X-ray analysis and electrical continuity "wiggle" tests on the cables.
The SRB separation system ordnance cables on Atlantis had been cleared for flight after an extensive evaluation following the STS 97 launch. Similar cables on the Atlantis stack had been inspected prior to its roll-out to the pad. Workers found a frayed outer covering on one cable and another failed an electrical current test. The testing and repairs had already delayed the roll-out for three weeks.
After finding damage on four cables of a total of 3,000 SRB-related cables tested, Shuttle managers decided to prove the integrity of the tunnel cables on Atlantis. Some of the four cables, which were between 14 to 16 years old, do not have back-ups. These tests had not been conducted on the Atlantis tunnel cables and, as further precautions, tests will be made before each Shuttle launch and some cables will be replaced more routinely.
The SRB cable alert follows a similar situation in 1999, when the Shuttle orbiters were grounded for four months after frayed wires were found under the payload bay floor of Columbia.
Source: Flight International
