STS-123: Houston checking into strange ascent debris incident

by Chris Bergin

Endeavour appears to have enjoyed a relatively clean ride uphill during the early hours of Tuesday, though evaluations are taking place on several debris events – most of which are classed as nominal.

However, as STS-123 concludes inspections on Flight Day 2, video and images of what appears to be a debris strike to Endeavour’s nose – possibly a bird strike – are gaining the most attention. Evaluations are still taking place to confirm if there was an impact or not.

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Given it is very early in the DAT (Debris Analysis Team) evaluations on the ascent imagery, the observed debris has not yet been identified.

The event, early into the ascent of Endeavour (T+10 seconds), shows the debris classed as ‘not from the vehicle’ moving down the stack in slowed down video of the incident.

It appears to impact the Forward Reaction Control System (RCS), from which it appears to knock loose one of the Tyvek covers. Neither can be confirmed at this stage.

However, that could be coincidental, given the covers are designed to liberate during this early stage of the ride uphill. It is also highly unlikely that the impact at the velocity Endeavour would have been travelling could have caused any damage.

‘Single piece of light colored debris (does not appear to originate from the vehicle) falls aft along ET and appears to contact Orbiter nose near F3F RCS thruster,’ noted the DAT team in a memo associated with the debris. ‘Have not observed debris or contact in other camera views. Will be reviewed further.’

Flight Director Mike Moses noted that evaluations were still ongoing by the end of Flight Day 2, and that they are still not sure what exactly the debris was.

However, he did stress that at T+10 seconds the velocity would not be enough to result in a damaging impact.

Also seen in the early imagery, acquired by L2 during Tuesday morning, are a handful of usual debris events, most of which are classed as ‘nominal’ at this stage of evaluation.

‘Tile coating loss noted outboard of SSME (Space Shuttle Main Engine) number 3 dome mounted heat shield,’ noted the data acquired so far, in order of T+ times, with the debris in question seen falling to the right of the vehicle during ignition.

Also classed as ignition debris events, several pieces of material are seen as the vehicle is lifting off the pad.

‘Ice (observed) falls along FSS (Fixed Service Structure) during GH2 Vent Arm Retract (T+2 seconds),’ noted DAT, with unclassified debris also seen in the same image at T+1.8 seconds. ‘Multiple pieces of debris seen at lift-off.’

Interestingly, only one debris event has been observed during first stage, clocked at T+83 seconds. This relates to a ‘nominal’ debris event which misses the starboard wing. It has not yet been evaluated as to how large that piece of debris was, or where it originated.

More findings are likely to follow, though the opening data points to a very clean ascent by Endeavour, to be confirmed by Flight Day 2’s inspections – and Flight Day 3’s RPM below the International Space Station.

‘No major on orbit issues being tracked at this time,’ noted information during second shift, Tuesday.

The couple of issues with Endeavour’s systems during ascent – notably with the Flash Evaporator System (FES) and three RCS (Reaction Control System) thrusters – all hold no mission impacts

‘The flash evaporator cooling system switched to its backup side. This issue has been noted on previous launches and should be no impact to the mission. The cooling system worked, albeit with less redundancy,’ noted information during Flight Day 1.

‘Troubleshooting will be performed after payload bay doors are opened in hopes of restoring the primary system for later use.

‘At T+3 sec, the L2L, L2U, and L2D fuel injector temps exponentially decayed in less than 20 sec from around 80 degF to (-1) degF. Suspect failure of DSC (digital signal conditioner) OL1 Card 1, caused the loss of instrumentation data.

‘The thrusters have been deselected for the mission given the loss of insight by this DSC, but should be no impact to mission as other thrusters are available.

‘APU (Auxiliary Power Unit) 1 gas generator chamber pressure transducer saw a shift from 28 psi to 128 psi and then became erratic at about 14 seconds prior to MECO. This issue is believed to be instrumentation only.’

Planned Flight Day 2 activities include inspections of the Thermal Protection System (TPS) survey via the OBSS (Orbiter Boom Sensor System) – which is to enjoy an interesting couple of months, when it is stowed on the ISS until the arrival of Discovery on STS-124 in May.

Extravehicular Mobility Unit checkout, Centerline camera installation, Orbiter Docking System ring extension, Orbital Maneuvering System pod survey and Rendezvous tools checkout will also be part of FD-2.

These tasks have been completed, ahead of docking with the ISS on Flight Day 3.

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