Atlantis’ booster requires troubleshooting

by Chris Bergin

United Space Alliance (USA) engineers are working on a troubleshooting plan, following ‘erratic’ chamber pressure readings on the right hand SRB (Solid Rocket Booster).

The issue – which was noted last night without specifics – is still expected to delay rollout by 24 hours, although engineers are looking at possibly continuing their evaluations on the launch pad. However, two of the IPRs (In Process Reviews) are officially classed as constraints to rollout.

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The issues have stopped the retraction of all the platforms that surround Atlantis and the STS-117 stack inside High Bay 1 of the Vehicle Assembly Building (VAB), with troubleshooting re-starting on Tuesday morning.

‘Rollout of STS-117 to the Pad may be delayed 24 hrs due to IPR’s 0062 and 0063 on the RH SRB (see IPR status directly below) – the schedule is under review,’ noted the expansive Launch Operations report for Tuesday.

‘C Platform retraction was completed yesterday. E Platform retraction is on hold for IPR troubleshooting access requirements in the SRB forward skirt area.

The list of IPRs were listed after the Integrated Space Shuttle Vehicle interface test was conducted on Atlantis and the STS-117 stack.

‘IPR-0061: RH (Right Hand) aft separation motor ‘no-go’ should be ‘go’ – will close as GSE cable not mated properly,’ listed the Launch Ops report. 

‘IPR-0062: Pitch and yaw indicator went from ‘on’ to ‘off’ to ‘on’. The constraint is to S0007 (Launch Countdown). This IPR may be related to IPR-0063. This IPR is a constraint to rollout.

‘IPR-0063, The RH SRM (Solid Rocket Motor) chamber pressure went erratic – could be related to IPR-0062. This IPR is a constraint to stray voltage testing, platform retraction, and rollout. Power up troubleshooting was performed last evening to try to isolate the problem to the chamber pressure OPT (Operational Pressure Transducer) in the RH forward skirt area.

‘Initial indications are that the transducer is faulty, however further troubleshooting will have to be performed to ascertain the condition of the cabling between the Monoball and the aft IEA, and the cabling between the aft IEA and the OPT in the forward skirt.’

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Troubleshooting the chamber pressure issue was ceased last night due to lack of manpower and a lack of adapter cables required for testing. This has resumed on Tuesday morning.

‘IPR-0064, RH SRB camera recorder #2 was ‘off’ and should’ve been ‘on’. Troubleshooting is complete to date; this may be a camera recorder card issue, and a camera/recorder R&R is possible. This IPR is not a constraint to roll out to the pad.

Another issue was also noted via an electrical bus error, which is also a constraint to rollout. However, this issue is not fully understood as to the culprit of the fault, which could lie anywhere between the RH SRB and the aft of Atlantis herself.

ATK’s Tuesday update confirmed the issues with the RH SRB, but noted that plans are in work to carrying out evaluations at the launch pad.

‘S0008, Shuttle Interface Test, is worked as far as possible. Stray voltage tests will follow IPR 117V-0063 resolution. SSV Rollout to Pad A call-to-stations are scheduled for 0300 hours on Wednesday to Thursday at the same time,’ noted the ATK Quick Look report for Tuesday.

‘IPR 0063 was written against the RH SRB electrical measurement that had an erratic reading. Troubleshooting points toward a bad OPT. Plans to R&R the OPT at the pad are in work.’

Atlantis’ processing has enjoyed a smooth flow until thes issues with one of her boosters, and such hiccups can be expected in any pre-launch work. There remains plenty of contingency time in the flow towards a March 15 launch date, regardless of a delay with rollout.

In other pre-launch news, a bent bracket has caused a slight delay in the preparations of Atlantis’ S3/S4 integrated truss payload at the launch pad.

‘The S3/S4 integrated truss payload transfer from the canister to the PGHM (Payload Ground Handling Mechanism) was delayed yesterday due to a bent bracket on one of the payload support beam drive motors,’ added the expansive Launch Operations report for Tuesday. ‘The Z drive motor was removed last night and the PGHM moved aft to close the canister doors in anticipation of poor weather.

‘An engineering review of a proposed solution will need to be performed along with the repair on 1st shift today. It is estimated that everything could be ready to support a payload transfer around mid 1st shift today. Canister lowering and transfer to the Canister Rotation Facility (CRF) will follow.’

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