STS-127: Foam loss observed on ET intertank images – FD2 inspections
Flight Day 2 for the crew of STS-127 focused on carrying out inspections of Endeavour’s Thermal Protection System (TPS), following Wednesday’s launch enroute to the International Space Station (ISS). Several debris events were noted during ascent, with ET photography showing numerous areas of missing foam on ET-131 – especially at the intertank region.
Shortly after reaching orbit, Endeavour’s Payload Bay Doors were opened, followed by the deployment of her Ku-band antenna. Endeavour’s Remote Manipulator System (RMS) was also activated ahead of Flight Day 2’s inspections.
Flight Day 2 opened with the unberthing of the Orbiter Boom Sensor System (OBSS) via the RMS, in order to carry out surveys of Endeavour’s wing and nose cap. The OMS Pods were also checked for any tile damage or protruding blankets.
“TPS Surveys: All RCC (Reinforced Carbon Carbon) is inspected during the OBSS Starboard Wing, Nose Cap, and Port Wing surveys. The two wing surveys also cover most of the areas of the crew cabin. The OMS Pod is inspected using a handheld camera to take pictures from the aft flight deck windows,” noted Flight Readiness Review (FRR) mission outline documentation (L2).
“The OBSS survey procedures incorporate the use of supplemental IDC (Digital Camera) images during LDRI (Laser Dynamic Range Imager) scans, thus reducing the likelihood of needing Focused Inspection.
“The OBSS unberth procedure incorporates the LDRI 3D calibration and the starboard survey the flat field calibration.
“Three crewmembers are required continuously during the surveys, two for the SRMS/OBSS ops and one to operate the situational awareness cameras and sensors. Only two crewmembers are required during unberthing and berthing operations (non-laser ops).
Scans of the entire starboard wing are not easily performed, or are impossible to perform while docked, and so are scheduled first. The surveys were scheduled through the night passes, with the option to pause if the night time visuals were not sufficient.
“The LDRI survey attitude requires no sun within a +/-20 degree field of view (FOV) of the laser bore-sight. Additionally, no sun can be within a 10 degree half-cone directly behind the instrument; however it is highly desired to keep the sun at a 90 degree half cone behind the instrument as long as it’s not directly behind.”
Although Flight Day 3’s RPM (Rbar Pitch Maneuver) – carried out “underneath” the ISS ahead of docking – will provide a near-complete overview of Endeavour’s heatshield, the OBSS inspections will give the opening insights into the extent of any damage sustained during the ride uphill.
Thanks to live and reviewed imagery taken by the ET camera during ascent, engineers already know one area that requires a closer look – following three coating losses on the starboard chine area of the orbiter.
“DAT (Damage Assessment Team) is checking with TIC (TPS Imagery Coordinator) personnel to determine if we get any chine imagery for “free” tomorrow during FD2 standard imagery,” noted DAT’s “forward plan” based on the ascent imagery. “If not we will get more detailed data on FD3 during standard RPM.”
“Review ET umbilical imagery to see what insulation is missing. WLEIDSS (Wing Leading Edge Impact Detection Sensor System) data/report review – see if any correlation to debris clouds is present.”
The ET umbilical camera/flash system had initially appeared to have suffered an issue, with no imagery of the separated tank downloaded to laptops onboard Endeavour, thus leaving no imagery to be downloaded to the ground at the time it was expected.
“FAO (Flight Activities Officer) does not see the umbilical well photos on any of the PGSCs (Payload and General Support Computers),” noted an early report from the Mission Evaluation Room (MER), on L2.
However, the crew later confirmed that they had found the images, as per conversation with the ground shortly after wake up.
That imagery – acquired by L2 – shows damage to the intertank, as the camera/flash system embedded into the umbilical well of the orbiter took a series of hi res photographs of the tank dropping away from Endeavour.
Damage has also been spotted on at least one of the Ice Frost Ramps (IFRs) and one area of the LOX tank TPS. A large area of foam is also missing from near the starboard Umbilical Well.
Additional handheld ET photography was also taken by the crew, utilizing handheld cameras to take hi res images of the tank as it began its journey to destruction in the Indian Ocean.
Once again, several areas of foam from the intertank ribs – located in the top third of the ET – is shown to have liberated. This is likely to be the foam loss observed on the ET camera during ascent.
However, the DAT engineers are not yet concerned by what they have seen, noting that if the debris losses are indeed foam, it is unlikely that they will have caused any serious damage to the orbter’s TPS.
“(We will also use): Crew Hand held of OMS Pod. OBSS survey of sidewall and crew cabin. RCC imagery/survey. FD3 is RPM – more definition of chine damages,” added DAT. “Ascent ET foam debris hits suspected. Debris report in work.
“TPS Damages noted during ET feedline video, around six discrete damage sites on RH (Right Hand) Chine area. Debris cloud at around MET (Mission Elapsed Time) 106 seconds caused the first cluster of form. AFT most cluster of two damages were caused around 4 to 6 seconds after the first four by some additional debris.
“Initial opinion is that these tile damages are within our experience base (if the debris was foam) but we need to perform our standard process. General consensus was there was quite a bit more debris than usual noted during the ET feedline video.”
Mission Management Team (MMT) documentation also noted 10 triggers on the WLEIDS, although it needs to be noted this is not unusual, and does not mean damage will be expected on the RCC panels/Wing Leading Edge.
Also, triggers can be set off even in the absense of an impact due to the sensitivity of the system. An expansion on the findings will be noted in the next article.
As noted by Shuttle Manager John Shannon, inspections of ET-132 – due to launch with Discovery next month – will take place, although no delay to Monday’s mating has been noted at this time.
Other items on the list for FD2 include EMU (EVA Mobility Unit) checkouts, ahead of their use on the mission’s three EVAs, and the extension of the Orbiter Docking Ring for FD3’s docking to the ISS.
In order to catch up with the orbital outpost, Endeavour will also conduct the NC2 (completed) and NC3 rendezvous burns – planned to allow adequate time for OBSS surveys. A NPC burn exists in the Flight Dynamics Officer’s plan, but is not scheduled since it will likely be combined with another burn.
More will follow during FD2 – refer to live update coverage on the links above.
L2 members: Documentation – from which the above article has quoted snippets – is available in full in the related L2 sections, now over 4000 gbs in size.