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Challenger Tragedy: Presidential Report Continued

The Challenger Accident

Just after liftoff at .678 seconds into the flight, photographic data show a strong puff of gray smoke was spurting from the vicinity of the aft field joint on the right Solid Rocket Booster. The two pad 39B cameras that would have recorded the precise location of the puff were inoperative. Computer graphic analysis of film from other cameras indicated the initial smoke came from the 270 to 310-degree sector of the circumference of the aft field joint of the right Solid Rocket Booster. This area of the solid booster faces the External Tank. The vaporized material streaming from the joint indicated there was not complete sealing action within the joint.

Eight more distinctive puffs of increasingly blacker smoke were recorded between .836 and 2.500 seconds. The smoke appeared to puff upwards from the joint. While each smoke puff was being left behind by the upward flight of the Shuttle, the next fresh puff could be seen near the level of the joint. The multiple smoke puffs in this sequence occurred at about four times per second, approximating the frequency of the structural load dynamics and resultant joint flexing. Computer graphics applied to NASA photos from a variety of cameras in this sequence again placed the smoke puffs' origin in the 270- to 310-degree sector of the original smoke spurt.

As the Shuttle increased its upward velocity, it flew past the emerging and expanding smoke puffs. The last smoke was seen above the field joint at 2.733 seconds.

The black color and dense composition of the smoke puffs suggest that the grease, joint insulation and rubber O-rings in the joint seal were being burned and eroded by the hot propellant gases.

At approximately 37 seconds, Challenger encountered the first of several high-altitude wind shear conditions, which lasted until about 64 seconds. The wind shear created forces on the vehicle with relatively large fluctuations. These were immediately sensed and countered by the guidance, navigation and control system.

   
 

Signs of black smoke immediately after liftoff of the Shuttle Challenger.

 
   

NASA photo

   
 

The steering system (thrust vector control) of the Solid Rocket Booster responded to all commands and wind shear effects. The wind shear caused the steering system to be more active than on any previous flight.

Both the Shuttle main engines and the solid rockets operated at reduced thrust approaching and passing through the area of maximum dynamic pressure of 720 pounds per square foot. Main engines had been throttled up to 104 percent thrust and the Solid Rocket Boosters were increasing their thrust when the first flickering flame appeared on the right Solid Rocket Booster in the area of the aft field joint. This first very small flame was detected on image enhanced film at 58.788 seconds into the flight. It appeared to originate at about 305 degrees around the booster circumference at or near the aft field joint.

   
 

Image taken 59.249 seconds into flight shows a well-defined intense plume on side of right hand solid rocket booster.

 
   

NASA photo

   
 

One film frame later from the same camera, the flame was visible without image enhancement. It grew into a continuous, well-defined plume at 59.262 seconds. At about the same time (60 seconds), telemetry showed a pressure differential between the chamber pressures in the right and left boosters. The right booster chamber pressure was lower, confirming the growing leak in the area of the field joint.

As the flame plume increased in size, it was deflected rearward by the aerodynamic slipstream and circumferentially by the protruding structure of the upper ring attaching the booster to the External Tank. These deflections directed the flame plume onto the surface of the External Tank. This sequence of flame spreading is confirmed by analysis of the recovered wreckage. The growing flame also impinged on the strut attaching the Solid Rocket Booster to the External Tank.

The first visual indication that swirling flame from the right Solid Rocket Booster breached the External Tank was at 64.660 seconds when there was an abrupt change in the shape and color of the plume. This indicated that it was mixing with leaking hydrogen from the External Tank. Telemetered changes in the hydrogen tank pressurization confirmed the leak. Within 45 milliseconds of the breach of the External Tank, a bright sustained glow developed on the black-tiled underside of the Challenger between it and the External Tank.

Beginning at about 72 seconds, a series of events occurred extremely rapidly that terminated the flight. Telemetered data indicate a wide variety of flight system actions that support the visual evidence of the photos as the Shuttle struggled futilely against the forces that were destroying it.

At about 72.20 seconds the lower strut linking the Solid Rocket Booster and the External Tank was severed or pulled away from the weakened hydrogen tank permitting the right Solid Rocket Booster to rotate around the upper attachment strut. This rotation is indicated by divergent yaw and pitch rates between the left and right Solid Rocket Boosters.

At 73.124 seconds,. a circumferential white vapor pattern was observed blooming from the side of the External Tank bottom dome. This was the beginning of the structural failure of hydrogen tank that culminated in the entire aft dome dropping away. This released massive amounts of liquid hydrogen from the tank and created a sudden forward thrust of about 2.8 million pounds, pushing the hydrogen tank upward into the intertank structure. At about the same time, the rotating right Solid Rocket Booster impacted the intertank structure and the lower part of the liquid oxygen tank. These structures failed at 73.137 seconds as evidenced by the white vapors appearing in the intertank region.

Within milliseconds there was massive, almost explosive, burning of the hydrogen streaming from the failed tank bottom and liquid oxygen breach in the area of the intertank.

At this point in its trajectory, while traveling at a Mach number of 1.92 at an altitude of 46,000 feet, the Challenger was totally enveloped in the explosive burn. The Challenger's reaction control system ruptured and a hypergolic burn of its propellants occurred as it exited the oxygen-hydrogen flames. The reddish brown colors of the hypergolic fuel burn are visible on the edge of the main fireball. The Orbiter, under severe aerodynamic loads, broke into several large sections which emerged from the fireball. Separate sections that can be identified on film include the main engine/tail section with the engines still burning, one wing of the Orbiter, and the forward fuselage trailing a mass of umbilical lines pulled loose from the payload bay.

Sequence of Major Events of the Challenger Accident

Mission Time                             Elapsed
(GMT, in hr:min:sec)     Event           Time (secs.)    Source
16:37:53.444  ME-3  Ignition Command              -6.566  GPC
   37:53.564  ME-2  Ignition Command              -6.446  GPC
   37:53.684  ME-1  Ignition Command              -6.326  GPC
   38:00.010  SRM Ignition Command (T=0)           0.000  GPC
   38:00.018  Holddown Post 2 PIC firing           0.008  E8 Camera
   38:00.260  First Continuous Vertical Motion     0.250  E9 Camera
   38:00.688  Confirmed smoke above field joint
              on RH SRM                            0.678  E60 Camera
   38:00.846  Eight puffs of smoke (from 0.836
                thru 2.500 sec MET)                0.836  E63 Camera
   38:02.743  Last positive evidence of smoke
              above right aft SRB/ET attach ring   2.733  CZR-1 Camera
   38:03.385  Last positive visual indication 
                  of smoke                         3.375  E60 Camera
   38:04.349  SSME 104% Command                    4.339  E41M2076D
   38:05.684  RH SRM pressure 11.8 psi above
                nominal                            5.674  B47P2302C
   38:07.734  Roll maneuver initiated              7.724  V90R5301C
   38:19.869  SSME 94% Command                    19.859  E41M2076D
   38:21.134  Roll maneuver completed             21.124  VP0R5301C
   38:35.389  SSME 65% Command                    35.379  E41M2076D
   38:37.000  Roll and Yaw Attitude Response to
              Wind (36.990 to 62.990 sec)         36.990  V95H352nC
   38:51.870  SSME 104% Command                   51.860  E41M2076D
   38:58.798  First evidence of flame on RH SRM   58.788  E207 Camera
   38:59.010  Reconstructed Max Q (720 psf)       59.000  BET
   38:59.272  Continuous well defined plume
                    on RH SRM                     59.262  E207 Camera
   38:59.763  Flame from RH SRM in +Z direction
              (seen from south side of vehicle)   59.753  E204 Camera
   39:00.014  SRM pressure divergence (RH vs. LH) 60.004  B47P2302
   39:00.248  First evidence of plume deflection,
                intermittent                      60.238  E207 Camera
   39:00.258  First evidence of SRB  plume
              attaching to ET ring frame          60.248  E203 Camera
   39:00.998  First evidence of plume deflection,
               continuous                         60.988  E207 Camera
   39:01.734  Peak roll rate response to wind     61.724  V90R5301C
   39:02.094  Peak TVC response to wind           62.084  B58H1150C
   39:02.414  Peak yaw response to wind           62.404  V90R5341C
   39:02.494  RH outboard elevon actuator hinge
               moment spike                       62.484  V58P0966C
   39:03.934  RH outboard elevon actuator delta
                pressure change                   63.924  V58P0966C
   39:03.974  Start of planned pitch rate
                maneuver                          63.964  V90R5321C
   39:04.670  Change in anomalous plume shape
              (LH2 tank leak near 2058 ring
              frame)                              64.660  E204 Camera
   39:04.715  Bright sustained glow on sides
               of ET                              64.705  E204 Camera
   39:04.947  Start SSME gimbal angle large
                pitch variations                  64.937  V58H1100A 
   39:05.174  Beginning of transient motion due
                to changes in aero forces due to
                plume                             65.164  V90R5321C
   39:06.774  Start ET LH2 ullage pressure
               deviations                         66.764  T41P1700C
   39:12.214  Start divergent yaw rates
               (RH vs. LH SRB)                    72.204  V90R2528C
   39:12.294  Start divergent pitch rates
               (RH vs. LH SRB)                    72.284  V90R2525C
   39:12.488  SRB major high-rate actuator
                command                           72.478  V79H2111A
   39:12.507  SSME roll gimball rates 5 deg/sec   72.497  V58H1100A
   39:12.535  Vehicle max +Y lateral
               acceleration (+.227 g)             72.525  V98A1581C
   39:12.574  SRB major high-rate actuator
              motion                              72.564  B58H1151C
   39:12.574  Start of H2 tank pressure decrease
              with 2 flow control valves open     72.564  T41P1700C
   39:12.634  Last state vector downlinked       72.624 Data reduction
   39:12.974  Start of sharp MPS LOX inlet
              pressure drop                       72.964  V41P1330C
   39:13.020  Last full computer frame of TDRS
                 data                            73.010 Data reduction
   39:13.054  Start of sharp MPS LH2 inlet
              pressure drop                       73.044  V41P1100C
   39:13.055  Vehicle max -Y lateral
                accelerarion (-.254 g)            73.045  V98A1581C
   39:13.134  Circumferential white pattern on
              ET aft dome (LH2 tank failure)      73.124  E204 Camera
   39:13.134  RH SRM pressure 19 psi lower
              than LH SRM                         73.124  B47P2302C
   39:13.147  First hint of vapor at intertank    E207 Camera
   39:13.153  All engine systems start responding
              to loss of fuel and LOX inlet
                pressure                          73.143  SSME team
   39:13.172  Sudden cloud a long ET between
              intertank and aft dome              73.162  E207 Camera
   39:13.201  Flash between Orbiter & LH2 tank    73.191  E204 Camera
   39:13.221  SSME telemetry data interference
              from 73.211 to 73.303               73.211
   39:13.223  Flash near SRB fwd attach and
               brightening of flash between
               Orbiter and ET                     73.213  E204 Camera
   39:13.292  First indication intense white
              flash at SRB fwd attach point       73.282  E204 Camera
   39:13.337  Greatly increased intensity of
               white flash                        73.327  E204 Camera
   39:13.387  Start RCS jet chamber pressure
                fluctuations                      73.377  V42P1552A
   39:13.393  All engines approaching HPFT
              discharge temp redline limits       73.383  E41Tn010D
   39:13.492  ME-2 HPFT disch. temp Chan. A vote
             for shutdown; 2 strikes on Chan. B   73.482  MEC data
   39:13.492  ME-2 controller last time word
                update                            73.482  MEC data
   39:13.513  ME-3 in shutdown due to HPFT discharge
              temperature redline exceedance      73.503  MEC data
   39:13.513  ME-3 controller last time word
                 update                           73.503  MEC data
   39:13.533  ME-1 in shutdown due to HPFT discharge
              temperature redline exceedance      73.523  Calculation
   39:13.553  ME-1 last telemetered data point    73.543  Calculation
   39:13.628  Last validated Orbiter telemetry
              measurement                         73.618  V46P0120A
   39:13.641  End of last reconstructured data 
              frame with valid synchronization
              and frame count                    73.631 Data reduction
   39:14.140  Last radio frequency signal from
                Orbiter                          74.130 Data reduction
   39:14.597  Bright flash in vicinity of Orbiter
                nose                             74.587  E204 Camera
   39:16.447  RH SRB nose cap sep/chute 
                deployment                       76.437  E207 Camera
   39:50.260  RH SRB RSS destruct               110.250  E202 Camera
   39:50.262  LH SRB RSS destruct               110.252  E230 Camera
ACT POS -- Actuator Position
APU     -- Auxilixary Power Unit
BET     -- Best Estimated Trajectory
CH      -- Channel
DISC    -- Discharge
ET      -- External Tank
GG      -- Gas Generator
GPC     -- General Purpose Computer
GMT     -- Greenwich Mean Time
HPFT    -- High Pressure Fuel Turbopump
LH      -- Lefthand
LH2     -- Liquid Hydrogen
LO2     -- Liquid Oxygen (same as LOX)
MAX Q   -- Maximum Dynamic Pressure
ME      -- Main Engine (same as SSME)
MEC     -- Main Engine Controller
MET     -- Mission Elapsed Time
MPS     -- Main Propulsion System
PC      -- Chamber Pressure
PIC     -- Pyrotechnics Initiator Controller
psf     -- Pounds per square foot
RCS     -- Reaction Control System
RGA     -- Rate Gyro Assembly
RH      -- Righthand
RSS     -- Range Safety System
SRM     -- Solid Rocket Motor
SSME    -- Space Shuttle Main Engine
TEMP    -- Temperature
TVC     -- Thrust Vector Control
NOTE:  The Shuttle coordinate system used is relative to the Orbiter,
as follows:
+X direction = forward (tail to nose)
-X direction = rearward (nose to tail)
+Y direction = right (toward the right wing tip)
-Y direction = left (toward the left wing tip)
+Z direction = down
-Z direction = up

Next page

Source: NASA.

 

Share Your Memories!

What do you remember about Challenger Presidential Report? Have you any compelling stories to share? Share your stories with the world! (We print the best stories right here!)

Your Memories Shared!

"I find it VERY hard to believe that the shuttle launch decision-making party was unaware of the problems that made the launch of Challenger so very dangerous. Was there no communication between NASA officials and engineers and experts screaming for a launch postponement? It became well known, through the extreme coverage of this event, that NASA was under pressure to meet a deadline to justify its enormous spending before the US Government. It does not take a lot of brains to see that the findings of their UNAWARENESS of the then recent Challenger history were no more than a big COVERUP. I rest assured that the persons who disregarded the safety of those seven souls aboard Challenger will meet their justice some day."

--Tom in Florida



Space References (Books):
Dickinson, Terence. Nightwatch: A Practical Guide to Viewing the Universe. Firefly Books, 1998.
Greene, Brian. Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. Vintage, 2000.
Hawking, Stephen. Illustrated Brief History of Time, Updated and Expanded Edition. Bantam, 1996.
Hawking, Stephen. Theory of Everything: The Origin and Fate of the Universe. New Millenium, 2002.
Hawking, Stephen. The Universe in a Nutshell. Bantam, 2001.
Kaku, Michio. Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps and the Tenth Dimension.
Kranz, Gene. Failure Is Not an Option: Mission Control from Mercury to Apollo 13 and Beyond. Berkley Pub Group, 2001.
Sagan, Carl; Druyan, Ann. Comet, Revised Edition. Ballantine, 1997
Sagan, Carl. Cosmos, Reissue Edition. Ballantine, 1993
Sagan, Carl. Pale Blue Dot: A Vision of the Human Future in Space. Ballantine, 1997

Space References (Videos):
Cosmos. PBS, 2000.
Stephen Hawking's Universe. PBS, 1997.
Hyperspace. BBC, 2002.
Life Beyond Earth PBS, 1999.
The Planets
. BBC, 1999.
Understanding The Universe. A&E, 1996.

 

SPACE SPECS

Challenger was finally launched on January 28, 1986 after postponements on the 22nd, 23rd, 24th, 25th, and 27th.

Courtesy of NASA


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