NASA STS-121/ULF1.1 FD 07 Execute Package
MSG 050 (13-0643) – FD07 MISSION SUMMARY
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Page 1 of 2, MSG 050 (13-0643)
Good morning, Discovery.
You’re in space, the TPS is clear, transfer is going well, and today is another EVA – life is great. Enjoy!
MSG 053A (13-0646A) – FD06 MMT SUMMARY
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Page 1 of 3, MSG 053A (13-0646A)
FD6 MMT Crew Summary
The primary focus of the FD6 MMT was a review of TPS analysis for the three areas that had not been previously cleared including the starboard ET door gap filler and the two thermal blankets (one forward of the CDR window just aft of the up firing thrusters and the other on the port side of the FRCS module). The good news is that the MMT cleared all three of these items, the entire Discovery TPS is now good for entry, and no modifications to EVA #3 will be required to retrieve the gap filler or remove the slightly protruding thermal blanket patches. The details of this assessment and analysis will be discussed in the TPS summary below.
The MMT also reviewed the detailed SRB, RSRM, SSME, ET, and PAD B GSE performance. In general ET-119 performed very well and there were no debris items that exceeded the allowables.
Finally, the ISS and SSP Programs have agreed to retain the requirements to transfer 15 CWCs. Even though there are 15 CWCs, due to the additional docked day, FD8 will need a simo dump. In terms of the Node 1 Nadir CBM center disk cover straps, the plan is to cut/fold and tape the straps leaving a 4”-5” tail and after that procedure there will be no further concerns with interference during mating ops.
TPS Summary:
a) Tile/RCC/ ET Doors – There is no new data on the tile, RCC, or ET doors . All have been cleared for entry.
b) Gap Fillers – The only remaining gap filler -the one forward of the starboard ET door was cleared for entry via a very conservative analysis that assumed a 1.04 inch protuberance height and a Mach 25 transition in a 20 degree cone aft of the gap filler. This results in worst case heating in the area aft of the gap filler (See Figure 1). Even with the worst case heating analysis, there is no tile coating loss, tile RTV bondline violation, or structural temperature exceedence. All structural margins including those for the ET doors and the thermal seals are positive with at least a 1.5 factor of safety. Additionally, an orbiter subsystems review including the aft structure, body flap and mechanisms, MPS, Hydraulics, ET Door actuators, wiring, active thermal control system, ET attach hardware and pyros was conducted to verify the higher structural temperatures did not negatively influence any systems. After a complete review each subsystem was cleared for the predicted higher structural temperatures.
Even though this conservative analysis was determined to result in an acceptable entry, the focused inspection data was utilized to determine what was likely to occur with the actual STS-121 gap filler during entry. A gap filler was modified on the ground to mimic the configuration of the actual gap filler obtained in the imagery. Testing of gap fillers with STS- 121 type defects showed that extremely low loads (.03 lbs) are required to bend over the gap filler. CFD analysis was utilized to predict the entry loads and stress analysis indicates that only 0.03 psi dynamic pressure is required to bend the gap filler over. This analysis shows that the gap filler will bend over by Mach 25 which reduces the effective protuberance height from 1.04 inches to 0.37 inches. In this case the prediction is that transition in this region will occur at approximately Mach 18. Again in this case there is no TPS or structure over temperature conditions and peak temperatures were reduced significantly from the more conservative Mach 25/1.04 inch height analysis. RTV bondline temperatures 1 ures were reduced approximately 85o F and structure temperatures were reduced by approximately 55o F. Previous flight data has been reviewed and there have been two prior flights with protruding gap fillers in this area, including STS-114 which had a .25 inch protruding gap filler in a similar location. Once the gap filler bends over during entry the resulting environment will be very close to that experienced during STS-114 which showed good TPS performance aft of the gap filler upon post landing inspection.
c) Thermal Blankets – The two blanket patches on the upper surface just aft of the F1U and F3U thrusters and the blanket on the port side just forward of the -Y star tracker were cleared for entry by the MMT. Figure 2 show the locations of two blanket patches
The port blanket was installed in 1995 and the patch identified in the photography was installed after STS-114 to protect eroded fabric. The forward side of this patch was not stitched per normal procedures because it is on a blanket edge. On this patch at least 28 to 56 stitches are still remaining and there is no evidence of patch body lifting. The mass of this entire patch is estimated to be .018 lbm. The predicted maximum load during entry for this patch based on CDF analysis is 0.9 lbs for the port blanket. Pull testing performed at Huntington Beach and at KSC on OV-105 indicate that the minimum load to remove a similar patch is 3.7 lbs which is three times greater than the maximum entry load which occurs below Mach 0.5. Since the patch did not release during ascent, where the ascent dynamic pressure was at least three times larger than peak entry dynamic pressure loads, it is not expected that it will release during entry.
The blanket near F1U and F3U forward of the CDR window was installed in 1994 and the patch was installed after STS-114 to protect damage on the OML edge. The patch is folded over 3” and the mass is very low at 0.008 lbm. In this area the maximum entry load is 0.6 lbs based on CFD analysis. Again the average pull load to remove was on the order of 5.4 lbs with a minimum of 3.7 lbs which is at least six times greater than the maximum entry load. And again ascent loading was on the order of three times larger on this patch, so this patch is not expected to be liberated during entry either.
The analysis for both patches is consistent with wind tunnel testing performed in support of the billowing thermal blanket observed on STS-114. Figure 3 shows the location of that blanket relative to these patches. Additionally, several other flights have re-entered with similar patches that were observed in very good condition on the runway. And finally even if the entire patch was liberated for either of these areas it is predicted that there will be no critical damage to the windows or any other orbiter structure.
