Thermal imaging video reveals flying debris during STS-124 launch

by Chris Bergin

As part of the investigation into the serious damage to Pad 39A’s flame trench during STS-124’s launch, shuttle managers have been shown a thermal imaging video of Discovery’s lift-off.

The video, acquired by L2 earlier in the week, shows what appears to be a large amount of debris flying horizontally out the trench to scatter behind the pad, but also vertically, chasing Discovery off the pad – though angling away from any potential contact with the vehicle. Article updated (read more).

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Thermal Imaging Video of STS-124 Launch:

Thanks to the Mobile Launch Platform (MLP), contact of trench debris with the vehicle is near impossible, with only three small holes in the MLP – one for the Space Shuttle Main Engines (SSMEs) and two for each Solid Rocket Booster (SRB).

Debris would have to break the laws of physics to rise through the holes and impact the vehicle.

The video, taken from the Vehicle Assembly Building (VAB) roof, cuts off at around T+7 seconds, just prior to the point at which the intense light of the boosters whites out the film, but not before revealing an what appears to be the immediate aftermath of the flame trench wall’s dramatic breakdown.

Obscured by the exhaust of Discovery’s SSMEs and SRBs on normal videos of the launch, the thermal imaging camera catches Discovery firing up her SSMEs, before the booster’s ignite.

Between T+3 and T+5 seconds – as Discovery rises off the pad – multiple objects suddenly appear rising between the water tower and the Fixed Service Structure (FSS), shooting up on the External Tank side of the vehicle. At least 20 individual items of debris are easily visible via the thermal imaging footage.


Due to the distance and angle the video was taken, the debris appears to just miss the rising stack off the pad – through in reality this would not have been the case.

Rather than an actual threat to the vehicle, the debris could only rise past the level of the MLP from outside the platform. It is also noted that the trajectory of the debris is always away from the vehicle.

This too is backed up by no observations of serious damage on the underside of the MLP. It’s been stressed several times by shuttle management that debris from under the MLP cannot rise above the platform’s level and impact the vehicle.

Also, it’s already been confirmed that Discovery’s stack received no ground debris impacts during any part of the ascent.

How the multitude of debris managed to fly so high – some observed to be as high as the top of the FSS – is unknown. It is assumed the observed debris originated from the flame trench wall, thrown downwards by the thrust of the boosters, before ricocheting into the air in the exposed areas of the trench.

The other theory relates to chucks of solid propellant from the boosters – which can sometimes be observed on launch videos during first stage – however, the STS-124 video is being tagged as a unique observation.

No documentation is associated with the video, bar the original title of the video, tagged as ‘flying bricks’ – thus, at this stage, it cannot be confirmed what the debris actually is, though it is being taken very seriously by engineers tasked with the investigation. 

This story will be followed up when more information is available.

Pad Repair Latest (UPDATED):

While that investigation continues, the main focus is on the repair effort that will take place to ensure the pad is ready to accept Atlantis and her stack for STS-125’s October 8 launch to service the Hubble Space Telescope.

The Engineering Review Board (ERB) reconvened on Friday to further review repair options, collating their latest finding ahead of a meeting next Tuesday with shuttle managers, as part of the System Integration Control Board (SICB) meeting.

The SICB may also shed more light on the debris observations during liftoff, with the subjects to be discussed including ‘Flame Trench Environments, Debris Transport Analysis Results, Repair Options Status and NDE (Non Destructive Evaluation) methods.’

The effort is focused on both Pad 39A and 39B – the latter set to host a final stack during STS-125 launch campaign, when Endeavour takes up residence as the Launch On Need (LON) rescue shuttle STS-400.

‘On flame trench activity, earlier in the week got all the brick cleaned up from the pad surface,’ noted a report from the ERB this week. ‘Continuing to evaluate the repair options, and hope to down-select the final repair option on Friday.’

Sources note the favored repair centers around using Fondu Fyre, a Refractory Concrete that is sprayed on to the surface of the flame trench. Interestingly, a presentation on the use of this material was presented to the Program Requirements Control Board (PRCB) back in February, 2007, and acquired by L2 at that time.

‘Intended for use on the Flame Deflectors to protect the facility from: radiant heat, flame impingement effects,’ noted the presentation. ‘Suitable for use at elevated temperatures. Uses hydraulic cement as a binding agent.

‘Key performance characteristics include; abrasion/erosion, shrinkage, thermal properties, compressive strength, tensile strength.’

The presentation notes that since the start of the Shuttle program, Fondu Fyre has remained the only refractory material qualified for use at KSC, and that performance during the program has been satisfactory, with increased maintenance and process modifications.

The material’s performance has managed an average of five launches between major maintenance/refurbishment, along with modifications to the material over the history of the program.

‘Process modifications since 1981 that have reduced liberated material. Metal shavings added to composition improved shear characteristics but presented safety hazard to maintenance personnel (cuts). Nelson studs installed to break up shear plane. Increased pour depth from 4” to 6”.’

Since Return To Flight, all post launch damage to the material at the pad started to be documented as part of the IFA (In Flight Anomaly) reviews.

‘STS-114: Main flame deflector lost some Fondu-Fyre during launch: Closed as expected launch damage and not a debris issue. STS-121: Missing refractory on upper S.W. corner of SRB side, Main flame deflector. Area repaired, not considered a debris issue.

STS-115: Small piece of Fondu-Fyre found loose on west side flame fence. Was not liberated. STS-116: (2) pieces of Fondu-Fyre found on east side of pad surface near side flame deflector. No repair required, leave as is.’

Interestingly, the presentation also outlines the work that was carried out on Pad 39A during its refurbishment, which included the replacement of sections of the Fondu Frye refractory concrete.

‘At Pad-A, a refurbishment has been completed on the SRB side of the flame trench,’ the 2007 presentation added. ‘Flame deflector structural steel repaired and coated. Flame deflector toes encased in concrete.

Worn sections of refractory taken down to structural steel, inspected, studs and grid steel added, replacement of refractory cement poured.’

Also an interesting note in the presentation relates to the risk assessments on the material liberating during launch, and the risk – or lack thereof – of the material being a debris hazard for the vehicle.

‘Liberation of the material is expected, due to the intensity of the launch environment. Liberation 45’ or more below MLP 0-level doesn’t occur until after the SRB’s are ignited post lift off, vehicle accelerating away from debris source.

‘Force of the exhaust is pushing any liberated debris towards the pad perimeter bottom structure of MLP offers protection from ricochet debris thrust of the SRB’s, and the sound suppression water flow prevent debris migration upward through MLP flame holes debris damage risk is to secondary non critical systems.’

Confidence remains high that the repairs can be completed ahead of Atlantis rolling to the pad in August.


‘The ERB (has) recommended the repair option for some brick removal and use of Fondue Fyre material in place of the removed bricks,’ noted L2 information on Monday. 

‘This recommendation will be presented at Thursday’s PRCB.  Analysis is still ongoing for the extent of stabilization required for some or all of the remaining bricks in the wall. 

‘Brick removal process may begin as early as this week.’

Reviewing STS-124:

While Discovery continues to undergo post flight processing inside her Orbiter Processing Facility (OPF), the highly successful mission will undergo a full review in the coming weeks, as is per usual.

The observation of a liberated thermal clip from the Rudder Speed Brake (RSB) has gained some references over the past couple of days, which was aided by a change of cameras the crew had to hand for quick identification of the object.

‘STS-124 seemed to go extremely well, especially the reaction to the clip on the last day,’ noted shuttle manager John Shannon on the latest Shuttle/Stand-up Integration report. ‘Know it was due to a lot of hard work and dedication to get us to that level, and it is appreciated. Looking forward to STS-125.

‘That the picture was ‘worth more than a thousand words’. It was good photography. They had the new cameras on this flight with the 12 mega pixels versus 5-6 for the other ones. That helped.’

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Despite the clip in question being no issue for re-entry – given its minor role is only during ascent – engineers are checking both Atlantis and Endeavour’s RSBs, with a potential of removing the clips – or tabs – from the vehicles. A couple of clips were confirmed to be missing from Discovery.

‘On our last full flight day, had a piece of debris that floated off the orbiter. That was a thermal clip, a little tab that joins the two thermal barriers together,’ added JSC’s Orbiter Project.

‘The Structures and TPS team are going to meet to determine the inspection criteria that we want to apply on OV-104 (Atlantis) and OV-105 (Endeavour), whether it be a purely visual inspection or tactile inspection. Will also go back and assess the inspection requirements.

‘It was mentioned at the MMT (Mission Management Team) that there is a history of these parts being discrepant or broken after flight.

‘In 2002, USA Orbiter proposed a modification. Will go back and reassess that. The modification ranged from deleting these barriers to changing the material. Also looked at the potential of eliminating the tabs altogether.’

Good news has also been confirmed on Discovery’s radiator retract hoses, which have been problematic during payload bay door closures ahead of, and during, recent missions.

‘On radiator retract hoses, the report was good in that they found no issues with radiator retract hoses. They all went into the box on STS-124 during payload bay door closing for deorbit. The aft starboard radiator retract hose is a new hose, first one we put into the fleet. It’s good news for the mod.’

Discovery is currently undergoing safing of her Reaction Control Systems inside the OPF, with preparations for SSME removal continuing.

L2 members: All documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, updated live.

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