COLUMBIA ACCIDENT INVESTIGATION BOARD (CAIB)/ NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA) ACCIDENT INVESTIGATION TEAM (NAIT) WORKING SCENARIO FINAL VERSION: JULY 8, 2003 PREFACE This Working Scenario report was written to document the collection of known facts, events, timelines, and historical information of particular interest to the final flight of Columbia. The report was written with the understanding that it could be published, either in part or in its entirety, as part of the official Columbia Accident Investigation Board (CAIB) report. The report includes information and results from numerous analyses, tests, and simulations related to the Columbia investigation that have been completed, or were ongoing at the time that this report was completed. It is anticipated that additional analytical and test results will emerge from ongoing work, as well as from future activities associated with the Columbia investigation and efforts related to the Return-To-Flight work. This Working Scenario includes information and results as they existed up to and including July 8, 2003. CONTENTS Section Page 1.0 INTRODUCTION........................................................................................ 1-1 1.1 SCOPE....................................................................................... 1-1 1.2 MISSION BACKGROUND.......................................................... 1-2 2.0 LAUNCH COUNTDOWN............................................................................ 2-1 3.0 LAUNCH..................................................................................................... 3-1 3.1 INTRODUCTION........................................................................ 3-1 3.2 LAUNCH DEBRIS IMPACT OBSERVATION............................. 3-2 3.2.1 Launch/Ascent Conditions.......................................................... 3-2 3.2.2 Launch Debris Impact Area........................................................ 3-4 3.2.3 Launch Photo and Transport Analysis........................................ 3-6 3.2.4 Debris Velocity and Size Assessment........................................ 3-10 3.2.5 Impact Damage Testing and Analysis........................................ 3-12 3.3 LAUNCH MADS DATA............................................................... 3-14 3.4 LAUNCH AREA RADAR ANALYSIS.......................................... 3-19 3.5 LAUNCH GUIDANCE NAVIGATION AND CONTROL............... 3-25 3.5.1 Wind Shear, Day of Launch Wind Effects.................................. 3-25 3.5.2 Predicted/Actual Loads .............................................................. 3-29 3.5.3 ET Liquid Oxygen Slosh............................................................. 3-33 3.5.4 Nozzle Positions......................................................................... 3-35 3.5.5 ET Separation Yaw Rate............................................................ 3-40 3.5.6 Data Correlation of Flights that Used a LWT and PEs............... 3-41 3.5.7 Data Correlation of Flights with ET Bipod Foam Liberation........ 3-42 4.0 ORBIT......................................................................................................... 4-1 4.1 INTRODUCTION........................................................................ 4-1 4.2 ORBITAL DEBRIS...................................................................... 4-1 4.2.1 Orbital Debris Risk Assessment................................................. 4-1 4.2.2 Micrometeoroid or Orbital Debris Detection................................ 4-1 4.3 FLIGHT DAY 2 EVENT.............................................................. 4-7 4.3.1 Radar Tracking of Flight Day 2 Object ....................................... 4-7 4.3.2 Analysis of Mechanisms for Object Release.............................. 4-9 4.3.3 Radar Cross Section and Ballistics Testing................................ 4-11 4.3.4 KSC Lost and Found Items........................................................ 4-13 4.4 ORBIT SUMMARY..................................................................... 4-13 i Section Page 5.0 DEORBIT/ENTRY....................................................................................... 5-1 5.1 INTRODUCTION........................................................................ 5-1 5.2 WEATHER................................................................................. 5-1 5.2.1 Upper Atmosphere Weather....................................................... 5-1 5.2.2 Landing Weather........................................................................ 5-1 5.3 HARDWARE FORENSICS......................................................... 5-4 5.4 ENTRY EVENTS TIMELINE...................................................... 5-12 5.4.1 Early Entry Heating Events......................................................... 5-12 5.4.2 First Roll Maneuver Through Wing Spar Breach........................ 5-16 5.4.3 Wing Breach and Wire Failures.................................................. 5-28 5.4.4 Aerodynamic Events................................................................... 5-37 5.4.5 Wheel Well Gas Penetration and Final Aerodynamic Events .... 5-47 5.5 AERODYNAMIC RECONSTRUCTION...................................... 5-53 6.0 RE-USABLE SOLID ROCKET MOTOR..................................................... 6-1 7.0 SOLID ROCKET BOOSTER...................................................................... 7-1 8.0 SPACE SHUTTLE MAIN ENGINE............................................................. 8-1 9.0 ENVIRONMENTAL FACTORS................................................................... 9-1 9.1 INTRODUCTION........................................................................ 9-1 9.2 AGE AND EXPOSURE .............................................................. 9-1 9.3 WEATHER FACTORS............................................................... 9-5 10.0 LEFT WING PROCESSING AND RCC DESIGN....................................... 10-1 10.1 INTRODUCTION........................................................................ 10-1 10.2 LEFT WING PROCESSING (PALMDALE, J3-OMM)................. 10-1 10.3 LEFT WING PROCESSING (STS-109)..................................... 10-4 10.4 LEFT WING PROCESSING (STS-107)..................................... 10-5 10.5 RCC DESIGN............................................................................. 10-7 10.6 RCC IMPACT RESISTANCE..................................................... 10-9 10.7 RCC CORROSION..................................................................... 10-10 11.0 EXTERNAL TANK...................................................................................... 11-1 11.1 INTRODUCTION........................................................................ 11-1 11.2 TPS REQUIREMENTS............................................................... 11-1 11.3 HISTORY OF FOAM CHANGES AND DEBRIS EVENTS......... 11-2 ii Section Page 11.4 STS-107/ET-93 CHRONOLOGY................................................ 11-6 11.4.1 Bipod Ramp TPS Configuration................................................. 11-6 11.4.2 Bipod Ramp Certification............................................................ 11-8 11.4.3 Bipod Ramp Build Process......................................................... 11-8 11.4.4 Bipod Ramp Foam Acceptance/Non-Destructive Evaluation..... 11-9 11.4.5 ET Shipping and Handling.......................................................... 11-9 11.4.6 KSC Processing Activities.......................................................... 11-9 11.4.7 ET Pre-launch Operations.......................................................... 11-11 11.4.8 Launch/Ascent............................................................................ 11-11 11.4.9 Possible Contributors to Strain Energy at ET Separation........... 11-12 11.5 STS-107/ET-93 TPS BIPOD DEBRIS........................................ 11-14 11.5.1 Bipod Foam Failure Modes and Contributors............................. 11-14 11.5.2 Test Results for Debris Assessment.......................................... 11-16 11.5.3 Max Bipod SLA Temperatures (80 seconds MET)..................... 11-17 11.5.4 Bipod Ramp As-Built Hardware Assessment............................. 11-18 11.5.5 Multi-Failure Mode TPS Bipod Debris........................................ 11-19 12.0 SUMMARY................................................................................................. 12-1 Appendix A ACRONYMS AND ABBREVIATIONS........................................................ A-1 iii TABLES Table Page 3-1 Wing damage analysis methods and results......................................... 3-5 3-2 Transport analysis and ET Working Group estimates of ET bipod debris size, weight, and volume............................................................ 3-12 3-3 STS-107 ascent radar events ............................................................... 3-20 3-4 Material samples from post-STS-27 radar calibration tests.................. 3-23 3-5 LWT and PE flights............................................................................... 3-41 3-6 STS flights with ET left bipod foam liberation........................................ 3-43 4-1 Summary of analysis of 13 rate events................................................. 4-3 4-2 Summary of analysis of the lower bound of MMOD (based on body rate data)............................................................................................... 4-4 4-3 Chronology of events related to flight day 2 object ............................... 4-10 4-4 Summary of nominal launch day events............................................... 4-11 4-5 Lost tools in Columbia processing for STS-107, STS-109, and OMM J3.......................................................................................... 4-13 10-1 RCC refurbishment limits...................................................................... 10-10 11-1 STS-Orbiter-ET configuration, age, and exposure................................ 11-3 FIGURES Figure 1-1 STS-107 payload bay configuration...................................................... 1-2 2-1 STS-107 Launch Countdown (LCD) overview flowchart....................... 2-2 2-2 Shuttle vehicle coordinate system......................................................... 2-4 3-1 Launch of STS-107 at pad 39A at Kennedy Space Center................... 3-2 3-2 STS-107 reconstructed altitude during first stage (prior to SRB separation)............................................................................................ 3-3 3-3 STS-107 flight reconstruction data for mach number and dynamic pressure (Q-bar) prior to SRB separation. Note that Q-bar is highest during first stage (prior to SRB separation), and reduces to a very small number after SRB separation...................................................... 3-3 3-4 Area of most likely wing damage........................................................... 3-4 iv Figure Page 3-5 Multiple analyses determine foam impacted lower RCC panels 6 through 8 area....................................................................................... 3-6 3-6 Photographic analysis techniques determined foam size: debris appears almost circular in frame 4914 and elongated in frame 4919... 3-7 3-7 Camera geometry for ascent video analysis; note that video camera ET208 is at same location as film camera E208................................... 3-7 3-8 Orbiter view from Cameras E212 and ET208....................................... 3-8 3-9 Multiple analyses indicate foam is from ET left bipod area................... Red line depicts the estimated foam trajectory as it moved from the bipod ramp area toward the left wing.................................................... 3-9 3-10 Video analysis shows impact is below wing leading edge stagnation line. Trajectories of particles are depicted after the impact.................. 3-9 3-11 Pre-impact vs. post-impact shows no observable damage within the resolution limits..................................................................................... 3-10 3-12 Sample CFD flow field with debris modeling......................................... 3-11 3-13 CFD surface flow with lower left wing pressure sensors....................... 3-14 3-14 Unusual behavior of pressure sensor V07P8074A............................... 3-15 3-15 Close-out photo shows RCC panel 9 wing leading edge temperature measurement........................................................................................ 3-16 3-16 Three-bit rise (7.5 degrees F) on MADS wing leading edge spar temperature measurement (V09T9895A) during ascent....................... 3-17 3-17 Correlation between simplified thermal math model and STS-107 ascent and entry flight data................................................................... 3-17 3-18 STS-107 ascent and entry heating environments on RCC panel 9....... 3-18 3-19 Limits of dimensional detectability for three simple shapes.................. 3-22 3-20 Limits of radar cross section (RCS) detectability and measured STS-107 debris for three radar source sites......................................... 3-22 3-21 Out-of-plane wind velocity..................................................................... 3-26 3-22 Side-slip angle....................................................................................... 3-27 3-23 Wing loads during wind shear and side-slip angle................................ 3-29 3-24 ET interface loads at forward attachment during wind shear and side-slip angle. Q-beta is side-slip angle multiplied by the dynamic pressure and represents the side-slip angle contribution of the interface load......................................................................................... 3-30 3-25 Slosh effect on ET interface loads........................................................ 3-30 3-26 ET bipod axial aerodynamic loads........................................................ 3-31 3-27 ET bipod side-force aerodynamic loads................................................ 3-32 3-28 ET bipod radial aerodynamic loads....................................................... 3-32 3-29 STS-107 SRB tilt actuators experienced more than typical 0.6 Hz content.................................................................................................. 3-33 3-30 STS-107 SRB gimbal responses at 0.6 Hz frequency correlated to wind....................................................................................................... 3-34 3-31 Center SSME yaw position.................................................................... 3-36 v Figure Page 3-32 Right SSME yaw position...................................................................... 3-36 3-33 RSRM burn rate at propellant mean bulk temperature (PMBT)............ 3-37 3-34 SRB thrust mismatch ............................................................................ 3-38 3-35 SRB nozzle position for PE flights versus non-PE flights...................... 3-39 3-36 ET separation yaw rate......................................................................... 3-40 4-1 Jet firing example for vehicle rates........................................................ 4-5 4-2 Sample data from SAMS and ODRC.................................................... 4-6 4-3 SAMS data frequency content .............................................................. 4-7 4-4 Tracking of flight day 2 object through various sensor passes.............. 4-8 4-5 On-orbit RCS shows increased tumble/rotation rate over time............. 4-9 4-6 Leading edge structural subsystem components matching RCS and ballistics.......................................................................................... 4-12 5-1 Wind profile developed by DAO as part of the STS-107 investigation (time referenced to 8:min:sec EST)...................................................... 5-2 5-2 Slag deposition in the RCC panel 8/9 area relative to the other parts of the left wing leading edge ................................................................. 5-4 5-3 Samples of severe slag deposition on the panel 8 rib........................... 5-5 5-4 Example of rib erosion .......................................................................... 5-6 5-5 Flow on the lower carrier panel 9 tiles................................................... 5-7 5-6 CAD drawing of the recovered debris showing overall slag deposition and erosion patterns............................................................................. 5-7 5-7 Analysis results show possible flow direction and deposition of metals.................................................................................................... 5-9 5-8 RCC panel debris location .................................................................... 5-10 5-9 Three possible orbiter locations of the Littlefield tile on left wing.......... 5-11 5-10 STS-107 stagnation heat flux and dynamic pressure. Note that EI was at 8:44:09 EST............................................................................... 5-13 5-11 Left wing RCC panel 9 strain gauge is first measurement to indicate an off-nominal event. Note that EI was at 8:44:09 EST....................... 5-13 5-12 MADS sensors inside left wing.............................................................. 5-14 5-13 Left wing RCC panel 9/10 clevis temp sensor is second measurement to indicate an off-nominal event..................................... 5-15 5-14 Typical off-nominal OMS pod thermocouple (V07T9220A)................... 5-16 5-15 Location of OMS pod thermocouples off-nominal low........................... 5-17 5-16 Postulated orbiter leeside flow field associated with wing leading edge damage........................................................................................ 5-18 5-17 Orbiter wind tunnel model with vent gap along wing leading edge........ 5-19 5-18 Wind tunnel model results for sensitivity of orbiter side fuselage and OMS pod heating patterns to mass addition along WLE leeside vent gap................................................................................................ 5-19 5-19 Location of left sidewall temperature sensor......................................... 5-20 5-20 Off-nominal temperature indication on the left sidewall ........................ 5-21 vi Figure Page 5-21 Temperature rise on tile surfaces aft of RCC panel 9........................... 5-22 5-22 Left wing MADS sensors, including Measurement Stimulation Identification (MSID) number, and start time of loss of signal (EI + sec.).............................................................................................. 5-23 5-23 RCC panel 9 MADS strain and temperature measurements, STS-107................................................................................................ 5-24 5-24 Off-nominal low OMS pod thermocouple (V07T9972A)........................ 5-25 5-25 Left side fuselage/OMS pod off-nominal responses indicate increased heating.................................................................................. 5-26 5-26 Wing tunnel test results for RCC panel 9 missing and resulting in increased heating to OMS pod.............................................................. 5-27 5-27 CFD results for no damage, partial damage, and full damage to RCC panel 9 show increased heating on side fuselage and OMS pod ......... 5-27 5-28 STS-107 entry heating rate profile........................................................ 5-28 5-29 Cable routing on wing leading edge and wheel well wall ...................... 5-29 5-30 Thermal model prediction of wing spar burn through............................ 5-30 5-31 Hot gas begins to fill left wing................................................................ 5-31 5-32 Columbia LH wing and wheel well geometry......................................... 5-32 5-33 Columbia LH wing and wheel well vent model (wheel well leak paths based on Atlantis test comparison)....................................................... 5-33 5-34 MADS data failure due to wire burning.................................................. 5-34 5-35 View of cables running along outside of wheel wall cavity bulkhead..... 5-35 5-36 Strain measurements on 1040 spar...................................................... 5-36 5-37 Off-nominal temperature rise rate in nose cap RCC attach clevis ........ 5-37 5-38 Location of sensors in the LH wing wheel well...................................... 5-38 5-39 Strain rise in lower 1040 spar cap......................................................... 5-39 5-40 Outboard elevon accelerometer responses at 8:52:25 and 8:52:31 EST (EI + 496 and 502 sec.)............................................. 5-40 5-41 Location of supply dump and vacuum vent nozzles.............................. 5-41 5-42 Off-nominal temperature for supply nozzle and vacuum vent nozzle.... 5-41 5-43 First noted off-nominal aero event (Greenwich Mean Time, GMT, is EST + 5 hours)...................................................................................... 5-42 5-44 Sharp change in rolling moment (GMT is EST + 5 hours)..................... 5-45 5-45 Modeling results show potential area of damage and that significant deformation of the intermediate wing area and/or a recession in the lower surface are possible .................................................................... 5-46 5-46 Temperature data in left wheel well trends up (GMT is EST + 5 hours).................................................................................................... 5-47 5-47 Hot gas breaches the wheel well........................................................... 5-48 5-48 Kirtland photo........................................................................................ 5-49 5-49 Increased wing deformation and wing recession leads to significant vehicle aerodynamic changes (GMT is EST + 5 hours)........................ 5-51 5-50 Wind tunnel testing configurations that match delta roll moment data.. 5-53 vii Figure Page 5-51 Wind tunnel configurations that match delta yaw moment data............ 5-54 5-52 Wind tunnel configurations that match delta pitch moment data........... 5-54 5-53 Delta roll for lower half and full panel RCC panel missing ................... 5-55 5-54 Delta yaw for lower half and full panel RCC panel missing................... 5-56 5-55 Wind tunnel testing results for missing lower carrier panel 8 and a slot and hole through wing.......................................................... 5-57 5-56 CFD analysis of wing deformation......................................................... 5-58 5-57 LaRC wind tunnel testing of lower surface depressions........................ 5-59 7-1 Details of SRB/ET forward separation bolt catcher assembly............... 7-2 9-1 ET age for all STS missions.................................................................. 9-1 9-2 ET age for STS-107 compared to ET age for missions with and without bipod foam loss.................................................................. 9-2 9-3 ET exposure time (to weather) prelaunch for all STS missions ............ 9-3 9-4 ET exposure time (to weather) for STS-107 compared to ET exposure time for missions with and without bipod foam loss............... 9-4 9-5 Total prelaunch rainfall for all STS missions......................................... 9-5 9-6 Total rainfall for STS-107 compared to total rainfall for missions with and without bipod foam loss.................................................................. 9-6 9-7 Average daily rainfall prelaunch for all STS missions ........................... 9-7 9-8 Average daily rainfall prelaunch for STS-107 compared to average daily rainfall for missions with and without bipod foam loss.................. 9-7 9-9 Day-of-launch average temperature for all STS missions..................... 9-8 9-10 Prelaunch average dewpoint for all STS missions................................ 9-9 9-11 Prelaunch average humidity for all STS missions................................. 9-9 10-1 RCC components.................................................................................. 10-2 10-2 RCC panel assembly ............................................................................ 10-3 10-3 Typical tile installation........................................................................... 10-4 10-4 Wing leading edge RCC........................................................................ 10-6 10-5 RCC cross section ................................................................................ 10-8 10-6 RCC impact resistance ......................................................................... 10-9 10-7 RCC corrosion process......................................................................... 10-11 10-8 Tee seal crack location ......................................................................... 10-12 10-9 Tee seal cracking.................................................................................. 10-13 10-10 RCC pinholes........................................................................................ 10-14 10-11 RCC impact damage............................................................................. 10-15 11-1 History of foam changes. Blowing agent shown in parentheses, no changes to SLA................................................................................ 11-2 11-2 Right (+Y) bipod ramp........................................................................... 11-7 11-3 Left and right bipod ramp flow differences, CFD results....................... 11-7 viii