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History of the roles of some Star Trek heavy hitte
STS 51-L Mission Overview and Preface to Presidential Commission
Report on the Challenger Accident
SPACELINK NOTE: The 25th mission in the Space Shuttle program --
flown by the Challenger -- ended tragically with the loss of its seven
crew members and destruction of the vehicle when it exploded shortly
after launch.
The launch -- the first from Pad B at KSC's Launch Complex 39 --
occurred at ll:38 a.m. EST, on Jan. 28, 1986. The flight had been
scheduled six times earlier, but was delayed because of technical
problems and bad weather.
One minute, 13 seconds after liftoff, the vehicle exploded and was
destroyed.
All seven members of the crew were killed. They were Francis R.
Scobee, commander; Michael J. Smith, pilot; three mission specialists:
Judith A. Resnik, Ellison Onizuka and Ronald E. McNair; payload
specialist, Gregory Jarvis of Hughes Aircraft, and payload specialist,
S. Christa McAuliffe, a New Hampshire teacher -- the first Space
Shuttle passenger/observer participating in the NASA Teacher in Space
Program. She had planned to teach planned lessons during live
television transmissions.
The primary cargo was the second Tracking and Data Relay Satellite
(TDRS). Also on board was another Spartan free-flying module which
was to observe Halley's Comet.
The preface from the report by The Presidential Commission on the
Space Shuttle Accident (created by Executive Order 12546 of February
3, 1986) follows:
PREFACE
The accident of Space Shuttle Challenger, mission 51-L, interrupting
for a time one of the most productive engineering, scientific and
exploratory programs in history, evoked a wide range of deeply felt
public responses. There was grief and sadness for the loss of seven
brave members of the crew; firm national resolve that those men and
women be forever enshrined in the annals of American heroes, and a
determination, based on that resolve and in their memory to strengthen
the Space Shuttle program so that this tragic event will become a
milestone on the way to achieving the full potential that space offers
to mankind.
The President, who was moved and troubled by this accident in a very
personal way, appointed an independent Commission made up of persons
not connected with the mission to investigate it. The mandate of the
Commission was to:
1. Review the circumstances surrounding the accident to establish
the probable cause or causes of the accident; and
2. Develop recommendations for corrective or other action based upon
the Commission's findings and determinations.
Immediately after being appointed, the Commission moved forward with
its investigation and, with the full support of the White House, held
public hearings dealing with the facts leading up to the accident. In
a closed society other options are available; in an open society --
unless classified matters are involved -- other options are not,
either as matter of law or as a practical matter.
In this case a vigorous investigation and full disclosure of the facts
were necessary. The way to deal with a failure of this magnitude is
to disclose all the facts fully and openly; to take immediate steps to
correct mistakes that led to the failure; and to continue the program
with renewed confidence and determination.
The Commission construed its mandate somewhat broadly to include
recommendations on safety matters not necessarily involved in this
accident but which require attention to make future flights safer.
Careful attention was given to concerns expressed by astronauts
because the Space Shuttle program will only succeed if the highly
qualified men and women who fly the Shuttle have confidence in the
system.
However, the Commission did not construe its mandate to require a
detailed investigation of all aspects of the Space Shuttle program; to
review budgetary matters; or to interfere with or supersede Congress
in any way in the performance of its duties. Rather, the Commission
focused its attention on the safety aspects of future flights based on
the lessons learned from the investigation with the objective being to
return to safe flight.
Congress recognized the desirability, in the first instance, of having
a single investigation of this national tragedy. It very responsibly
agreed to await the Commission's findings before deciding what further
action might be necessary to carry out its responsibilities.
For the first several days after the accident -- possibly because of
the trauma resulting from the accident -- NASA appeared to be
withholding information about the accident from the public. After the
Commission began its work, and at its suggestion, NASA began releasing
a great deal of information that helped to reassure the public that
all aspects of the accident were being investigated and that the full
story was being told in an orderly and thorough manner.
Following the suggestion of the Commission, NASA established several
teams of persons not involved in the mission 51-L launch process to
support the Commission and its panels. These NASA teams have
cooperated with the Commission in every aspect of its work. The
result has been a comprehensive and complete investigation.
The Commission believes that its investigation and report have been
responsive to the request of the President and hopes that they will
serve the best interests of the nation in restoring the United States
space program to its preeminent position in the world.
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.
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.
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
THE CAUSE OF THE ACCIDENT
The consensus of the Commission and participating investigative
agencies is that the loss of the Space Shuttle Challenger was caused
by a failure in the joint between the two lower segments of the right
Solid Rocket Motor. The specific failure was the destruction of the
seals that are intended to prevent hot gases from leaking through the
joint during the propellant burn of the rocket motor. The evidence
assembled by the Commission indicates that no other element of the
Space Shuttle system contributed to this failure.
In arriving at this conclusion, the Commission reviewed in detail all
available data, reports and records; directed and supervised numerous
tests, analyses, and experiments by NASA, civilian contractors and
various government agencies; and then developed specific scenarios and
the range of most probable causative factors.
FINDINGS
1. A combustion gas leak through the right Solid Rocket Motor aft
field joint initiated at or shortly after ignition eventually weakened
and/or penetrated the External Tank initiating vehicle structural
breakup and loss of the Space Shuttle Challenger during STS Mission
51-L.
2. The evidence shows that no other STS 51-L Shuttle element or the
payload contributed to the causes of the right Solid Rocket Motor aft
field joint combustion gas leak. Sabotage was not a factor.
3. Evidence examined in the review of Space Shuttle material,
manufacturing, assembly, quality control, and processing on
non-conformance reports found no flight hardware shipped to the launch
site that fell outside the limits of Shuttle design specifications.
4. Launch site activities, including assembly and preparation, from
receipt of the flight hardware to launch were generally in accord with
established procedures and were not considered a factor in the
accident.
5. Launch site records show that the right Solid Rocket Motor segments
were assembled using approved procedures. However, significant
out-of-round conditions existed between the two segments joined at the
right Solid Rocket Motor aft field joint (the joint that failed).
a. While the assembly conditions had the potential of generating
debris or damage that could cause O-ring seal failure, these were not
considered factors in this accident.
b. The diameters of the two Solid Rocket Motor segments had grown as
a result of prior use.
c. The growth resulted in a condition at time of launch wherein the
maximum gap between the tang and clevis in the region of the joint's
O-rings was no more than .008 inches and the average gap would have
been .004 inches.
d. With a tang-to-clevis gap of .004 inches, the O-ring in the joint
would be compressed to the extent that it pressed against all three
walls of the O-ring retaining channel.
e. The lack of roundness of the segments was such that the smallest
tang-to-clevis clearance occurred at the initiation of the assembly
operation at positions of 120 degrees and 300 degrees around the
circumference of the aft field joint. It is uncertain if this tight
condition and the resultant greater compression of the O-rings at
these points persisted to the time of launch.
6. The ambient temperature at time of launch was 36 degrees
Fahrenheit, or 15 degrees lower than the next coldest previous launch.
a. The temperature at the 300 degree position on the right aft
field joint circumference was estimated to be 28 degrees plus or minus
5 degrees Fahrenheit. This was the coldest point on the joint.
b. Temperature on the opposite side of the right Solid Rocket
Booster facing the sun was estimated to be about 50 degrees
Fahrenheit.
7. Other joints on the left and right Solid Rocket Boosters
experienced similar combinations of tang-to-clevis gap clearance and
temperature. It is not known whether these joints experienced
distress during the flight of 51-L.
8. Experimental evidence indicates that due to several effects
associated with the Solid Rocket Booster's ignition and combustion
pressures and associated vehicle motions, the gap between the tang and
the clevis will open as much as .017 and .029 inches at the secondary
and primary O-rings, respectively.
a. This opening begins upon ignition, reaches its maximum rate of
opening at about 200-300 milliseconds, and is essentially complete at
600 milliseconds when the Solid Rocket Booster reaches its operating
pressure.
b. The External Tank and right Solid Rocket Booster are connected
by several struts, including one at 310 degrees near the aft field
joint that failed. This strut's effect on the joint dynamics is to
enhance the opening of the gap between the tang and clevis by about
10-20 percent in the region of 300-320 degrees.
9. O-ring resiliency is directly related to its temperature.
a. A warm O-ring that has been compressed will return to its
original shape much quicker than will a cold O-ring when compression
is relieved. Thus, a warm O-ring will follow the opening of the
tang-to-clevis gap. A cold O-ring may not.
b. A compressed O-ring at 75 degrees Fahrenheit is five times more
responsive in returning to its uncompressed shape than a cold O-ring
at 30 degrees Fahrenheit.
c. As a result it is probable that the O-rings in the right solid
booster aft field joint were not following the opening of the gap
between the tang and cleavis at time of ignition.
10. Experiments indicate that the primary mechanism that actuates
O-ring sealing is the application of gas pressure to the upstream
(high-pressure) side of the O-ring as it sits in its groove or
channel.
a. For this pressure actuation to work most effectively, a space
between the O-ring and its upstream channel wall should exist during
pressurization.
b. A tang-to-clevis gap of .004 inches, as probably existed in the
failed joint, would have initially compressed the O-ring to the degree
that no clearance existed between the O-ring and its upstream channel
wall and the other two surfaces of the channel.
c. At the cold launch temperature experienced, the O-ring would be
very slow in returning to its normal rounded shape. It would not
follow the opening of the tang-to-clevis gap. It would remain in its
compressed position in the O-ring channel and not provide a space
between itself and the upstream channel wall. Thus, it is probable
the O-ring would not be pressure actuated to seal the gap in time to
preclude joint failure due to blow-by and erosion from hot combustion
gases.
11. The sealing characteristics of the Solid Rocket Booster O-rings
are enhanced by timely application of motor pressure.
a. Ideally, motor pressure should be applied to actuate the O-ring
and seal the joint prior to significant opening of the tang-to-clevis
gap (100 to 200 milliseconds after motor ignition).
b. Experimental evidence indicates that temperature, humidity and
other variables in the putty compound used to seal the joint can delay
pressure application to the joint by 500 milliseconds or more.
c. This delay in pressure could be a factor in initial joint
failure.
12. Of 21 launches with ambient temperatures of 61 degrees Fahrenheit
or greater, only four showed signs of O-ring thermal distress; i.e.,
erosion or blow-by and soot. Each of the launches below 61 degrees
Fahrenheit resulted in one or more O-rings showing signs of thermal
distress.
a. Of these improper joint sealing actions, one-half occurred in
the aft field joints, 20 percent in the center field joints, and 30
percent in the upper field joints. The division between left and
right Solid Rocket Boosters was roughly equal.
b. Each instance of thermal O-ring distress was accompanied by a
leak path in the insulating putty. The leak path connects the
rocket's combustion chamber with the O-ring region of the tang and
clevis. Joints that actuated without incident may also have had these
leak paths.
13. There is a possibility that there was water in the clevis of the
STS 51-L joints since water was found in the STS-9 joints during a
destack operation after exposure to less rainfall than STS 51-L. At
time of launch, it was cold enough that water present in the joint
would freeze. Tests show that ice in the joint can inhibit proper
secondary seal performance.
14. A series of puffs of smoke were observed emanating from the 51-L
aft field joint area of the right Solid Rocket Booster between 0.678
and 2.500 seconds after ignition of the Shuttle Solid Rocket Motors.
a. The puffs appeared at a frequency of about three puffs per
second. This roughly matches the natural structural frequency of the
solids at lift off and is reflected in slight cyclic changes of the
tang-to-clevis gap opening.
b. The puffs were seen to be moving upward along the surface of the
booster above the aft field joint.
c. The smoke was estimated to originate at a circumferential
position of between 270 degrees and 315 degrees on the booster aft
field joint, emerging from the top of the joint.
15. This smoke from the aft field joint at Shuttle lift off was the
first sign of the failure of the Solid Rocket Booster O-ring seals on
STS 51-L.
16. The leak was again clearly evident as a flame at approximately 58
seconds into the flight. It is possible that the leak was continuous
but unobservable or non-existent in portions of the intervening
period. It is possible in either case that thrust vectoring and
normal vehicle response to wind shear as well as planned maneuvers
reinitiated or magnified the leakage from a degraded seal in the
period preceding the observed flames. The estimated position of the
flame, centered at a point 307 degrees around the circumference of the
aft field joint, was confirmed by the recovery of two fragments of the
right Solid Rocket Booster.
a. A small leak could have been present that may have grown to
breach the joint in flame at a time on the order of 58 to 60 seconds
after lift off.
b. Alternatively, the O-ring gap could have been resealed by
deposition of a fragile buildup of aluminum oxide and other combustion
debris. This resealed section of the joint could have been disturbed
by thrust vectoring, Space Shuttle motion and flight loads inducted by
changing winds aloft.
c. The winds aloft caused control actions in the time interval of
32 seconds to 62 seconds into the flight that were typical of the
largest values experienced on previous missions.
CONCLUSION
In view of the findings, the Commission concluded that the cause of
the Challenger accident was the failure of the pressure seal in the
aft field joint of the right Solid Rocket Booster. The failure was
due to a faulty design unacceptably sensitive to a number of factors.
These factors were the effects of temperature, physical dimensions,
the character of materials, the effects of reusability, processing and
the reaction of the joint to dynamic loading.
THE CONTRIBUTING CAUSE OF THE ACCIDENT
The decision to launch the Challenger was flawed. Those who made that
decision were unaware of the recent history of problems concerning the
O-rings and the joint and were unaware of the initial written
recommendation of the contractor advising against the launch at
temperatures below 53 degrees Fahrenheit and the continuing opposition
of the engineers at Thiokol after the management reversed its
position. They did not have a clear understanding of Rockwell's
concern that it was not safe to launch because of ice on the pad. If
the decision makers had known all of the facts, it is highly unlikely
that they would have decided to launch 51-L on January 28, 1986.
FINDINGS
1. The Commission concluded that there was a serious flaw in the
decision making process leading up to the launch of flight 51-L. A
well structured and managed system emphasizing safety would have
flagged the rising doubts about the Solid Rocket Booster joint seal.
Had these matters been clearly stated and emphasized in the flight
readiness process in terms reflecting the views of most of the Thiokol
engineers and at least some of the Marshall engineers, it seems likely
that the launch of 51-L might not have occurred when it did.
2. The waiving of launch constraints appears to have been at the
expense of flight safety. There was no system which made it
imperative that launch constraints and waivers of launch constraints
be considered by all levels of management.
3. The Commission is troubled by what appears to be a propensity of
management at Marshall to contain potentially serious problems and to
attempt to resolve them internally rather than communicate them
forward. This tendency is altogether at odds with the need for
Marshall to function as part of a system working toward successful
flight missions, interfacing and communicating with the other parts of
the system that work to the same end.
4. The Commission concluded that the Thiokol Management reversed its
position and recommended the launch of 51-L, at the urging of Marshall
and contrary to the views of its engineers in order to accommodate a
major customer.
Findings
The Commission is concerned about three aspects of the ice-on-the-pad
issue.
1. An Analysis of all of the testimony and interviews establishes
that Rockwell's recommendation on launch was ambiguous. The
Commission finds it difficult, as did Mr. Aldrich, to conclude that
there was a no-launch recommendation. Moreover, all parties were
asked specifically to contact Aldrich or other NASA officials after
the 9:00 Mission Management Team meeting and subsequent to the
resumption of the countdown.
2. The Commission is also concerned about the NASA response to the
Rockwell position at the 9:00 a.m. meeting. While it is understood
that decisions have to be made in launching a Shuttle, the Commission
is not convinced Levels I and II appropriately considered Rockwell's
concern about the ice. However ambiguous Rockwell's position was, it
is clear that they did tell NASA that the ice was an unknown
condition. Given the extent of the ice on the pad, the admitted
unknown effect of the Solid Rocket Motor and Space Shuttle Main
Engines ignition on the ice, as well as the fact that debris striking
the Orbiter was a potential flight safety hazard, the Commission finds
the decision to launch questionable under those circumstances. In
this situation, NASA appeared to be requiring a contractor to prove
that it was not safe to launch, rather than proving it was safe.
Nevertheless, the Commission has determined that the ice was not a
cause of the 51-L accident and does not conclude that NASA's decision
to launch specifically overrode a no-launch recommendation by an
element contractor.
3. The Commission concluded that the freeze protection plan for
launch pad 39B was inadequate. The Commission believes that the
severe cold and presence of so much ice on the fixed service structure
made it inadvisable to launch on the morning of January 28, and that
margins of safety were whittled down too far.
Additionally, access to the crew emergency slide wire baskets was
hazardous due to ice conditions. Had the crew been required to
evacuate the Orbiter on the launch pad, they would have been running
on an icy surface. The Commission believes the crew should have been
made aware of the condition, greater consideration should have been
given to delaying the launch.
AN ACCIDENT ROOTED IN HISTORY
EARLY DESIGN
The Space Shuttle's Solid Rocket Booster problem began with the faulty
design of its joint and increased as both NASA and contractor
management first failed to recognize it as a problem, then failed to
fix it and finally treated it as an acceptable flight risk.
Morton Thiokol, Inc., the contractor, did not accept the implication
of tests early in the program that the design had a serious and
unanticipated flaw. NASA did not accept the judgment of its engineers
that the design was unacceptable, and as the joint problems grew in
number and severity NASA minimized them in management briefings and
reports. Thiokol's stated position was that "the condition is not
desirable but is acceptable."
Neither Thiokol nor NASA expected the rubber O-rings sealing the
joints to be touched by hot gases of motor ignition, much less to be
partially burned. However, as tests and then flights confirmed damage
to the sealing rings, the reaction by both NASA and Thiokol was to
increase the amount of damage considered "acceptable." At no time did
management either recommend a redesign of the joint or call for the
Shuttle's grounding until the problem was solved.
FINDINGS
The genesis of the Challenger accident -- the failure of the joint of
the right Solid Rocket Motor -- began with decisions made in the
design of the joint and in the failure by both Thiokol and NASA's
Solid Rocket Booster project office to understand and respond to facts
obtained during testing.
The Commission has concluded that neither Thiokol nor NASA responded
adequately to internal warnings about the faulty seal design.
Furthermore, Thiokol and NASA did not make a timely attempt to develop
and verify a new seal after the initial design was shown to be
deficient. Neither organization developed a solution to the
unexpected occurrences of O-ring erosion and blow-by even though this
problem was experienced frequently during the Shuttle flight history.
Instead, Thiokol and NASA management came to accept erosion and
blow-by as unavoidable and an acceptable flight risk. Specifically,
the Commission has found that:
1. The joint test and certification program was inadequate. There
was no requirement to configure the qualifications test motor as it
would be in flight, and the motors were static tested in a horizontal
position, not in the vertical flight position.
2. Prior to the accident, neither NASA nor Thiokol fully understood
the mechanism by which the joint sealing action took place.
3. NASA and Thiokol accepted escalating risk apparently because they
"got away with it last time." As Commissioner Feynman observed, the
decision making was:
"a kind of Russian roulette. ... (The Shuttle) flies (with O-ring
erosion) and nothing happens. Then it is suggested, therefore, that
the risk is no longer so high for the next flights. We can lower our
standards a little bit because we got away with it last time. ... You
got away with it, but it shouldn't be done over and over again like
that."
4. NASA's system for tracking anomalies for Flight Readiness Reviews
failed in that, despite a history of persistent O-ring erosion and
blow-by, flight was still permitted. It failed again in the strange
sequence of six consecutive launch constraint waivers prior to 51-L,
permitting it to fly without any record of a waiver, or even of an
explicit constraint. Tracking and continuing only anomalies that are
"outside the data base" of prior flight allowed major problems to be
removed from and lost by the reporting system.
5. The O-ring erosion history presented to Level I at NASA
Headquarters in August 1985 was sufficiently detailed to require
corrective action prior to the next flight.
6. A careful analysis of the flight history of O-ring performance
would have revealed the correlation of O-ring damage and low
temperature. Neither NASA nor Thiokol carried out such an analysis;
consequently, they were unprepared to properly evaluate the risks of
launching the 51-L mission in conditions more extreme than they had
encountered before.
THE SILENT SAFETY PROGRAM
The Commission was surprised to realize after many hours of testimony
that NASA's safety staff was never mentioned. No witness related the
approval or disapproval of the reliability engineers, and none
expressed the satisfaction or dissatisfaction of the quality assurance
staff. No one thought to invite a safety representative or a
reliability and quality assurance engineer to the January 27, 1986,
teleconference between Marshall and Thiokol. Similarly, there was no
representative of safety on the Mission Management Team that made key
decisions during the countdown on January 28, 1986. The Commission is
concerned about the symptoms that it sees.
The unrelenting pressure to meet the demands of an accelerating flight
schedule might have been adequately handled by NASA if it had insisted
upon the exactingly thorough procedures that were its hallmark during
the Apollo program. An extensive and redundant safety program
comprising interdependent safety, reliability and quality assurance
functions existed during and after the lunar program to discover any
potential safety problems. Between that period and 1986, however, the
program became ineffective. This loss of effectiveness seriously
degraded the checks and balances essential for maintaining flight
safety.
On April 3, 1986, Arnold Aldrich, the Space Shuttle program manager,
appeared before the Commission at a public hearing in Washington,
D.C. He described five different communication or organization
failures that affected the launch decision on January 28, 1986. Four
of those failures relate directly to faults within the safety
program. These faults include a lack of problem reporting
requirements, inadequate trend analysis, misrepresentation of
criticality and lack of involvement in critical discussions. A
properly staffed, supported, and robust safety organization might well
have avoided these faults and thus eliminated the communication
failures.
NASA has a safety program to ensure that the communication failures to
which Mr. Aldrich referred do not occur. In the case of mission 51-L,
that program fell short.
FINDINGS
1. Reductions in the safety, reliability and quality assurance work
force at Marshall and NASA Headquarters have seriously limited
capability in those vital functions.
2. Organizational structures at Kennedy and Marshall have placed
safety, reliability and quality assurance offices under the
supervision of the very organizations and activities whose efforts
they are to check.
3. Problem reporting requirements are not concise and fail to get
critical information to the proper levels of management.
4. Little or no trend analysis was performed on O-ring erosion and
blow-by problems.
5. As the flight rate increased, the Marshall safety, reliability and
quality assurance work force was decreasing, which adversely affected
mission safety.
6. Five weeks after the 51-L accident, the criticality of the Solid
Rocket Motor field joint was still not properly documented in the
problem reporting system at Marshall.
PRESSURES ON THE SYSTEM
With the 1982 completion of the orbital flight test series, NASA began
a planned acceleration of the Space Shuttle launch schedule. One
early plan contemplated an eventual rate of a mission a week, but
realism forced several downward revisions. In 1985, NASA published a
projection calling for an annual rate of 24 flights by 1990. Long
before the Challenger accident, however, it was becoming obvious that
even the modified goal of two flights a month was overambitious.
In establishing the schedule, NASA had not provided adequate resources
for its attainment. As a result, the capabilities of the system were
strained by the modest nine-mission rate of 1985, and the evidence
suggests that NASA would not have been able to accomplish the 14
flights scheduled for 1986. These are the major conclusions of a
Commission examination of the pressures and problems attendant upon
the accelerated launch schedule.
FINDINGS
1. The capabilities of the system were stretched to the limit to
support the flight rate in winter 1985/1986. Projections into the
spring and summer of 1986 showed a clear trend; the system, as it
existed, would have been unable to deliver crew training software for
scheduled flights by the designated dates. The result would have been
an unacceptable compression of the time available for the crews to
accomplish their required training.
2. Spare parts are in critically short supply. The Shuttle program
made a conscious decision to postpone spare parts procurements in
favor of budget items of perceived higher priority. Lack of spare
parts would likely have limited flight operations in 1986.
3. Stated manifesting policies are not enforced. Numerous late
manifest changes (after the cargo integration review) have been made
to both major payloads and minor payloads throughout the Shuttle
program.
Late changes to major payloads or program requirements can require
extensive resources (money, manpower, facilities) to implement.
If many late changes to "minor" payloads occur, resources are
quickly absorbed.
Payload specialists frequently were added to a flight well after
announced deadlines.
Late changes to a mission adversely affect the training and
development of procedures for subsequent missions.
4. The scheduled flight rate did not accurately reflect the
capabilities and resources.
The flight rate was not reduced to accommodate periods of
adjustment in the capacity of the work force. There was no margin in
the system to accommodate unforeseen hardware problems.
Resources were primarily directed toward supporting the flights
and thus not enough were available to improve and expand facilities
needed to support a higher flight rate.
5. Training simulators may be the limiting factor on the flight rate:
the two current simulators cannot train crews for more than 12-15
flights per year.
6. When flights come in rapid succession, current requirements do not
ensure that critical anomalies occurring during one flight are
identified and addressed appropriately before the next flight.
OTHER SAFETY CONSIDERATIONS
In the course of its investigation, the Commission became aware of a
number of matters that played no part in the mission 51-L accident but
nonetheless hold a potential for safety problems in the future.
Some of these matters, those involving operational concerns, were
brought directly to the Commission's attention by the NASA astronaut
office. They were the subject of a special hearing.
Other areas of concern came to light as the Commission pursued various
lines of investigation in its attempt to isolate the cause of the
accident. These inquiries examined such aspects as the development
and operation of each of the elements of the Space Shuttle -- the
Orbiter, its main engines and the External Tank; the procedures
employed in the processing and assembly of 51-L, and launch damage.
This chapter examines potential risks in two general areas. The first
embraces critical aspects of a Shuttle flight; for example,
considerations related to a possible premature mission termination
during the ascent phase and the risk factors connected with the
demanding approach and landing phase. The other focuses on testing,
processing and assembling the various elements of the Shuttle.
ASCENT: A Critical Phase
The events of flight 51-L dramatically illustrated the dangers of the
first stage of a Space Shuttle ascent. The accident also focused
attention on the issues of Orbiter abort capabilities and crew
escape. Of particular concern to the Commission are the current abort
capabilities, options to improve those capabilities, options for crew
escape and the performance of the range safety system.
It is not the Commission's intent to second-guess the Space Shuttle
design or try to depict escape provisions that might have saved the
51-L crew. In fact, the events that led to destruction of the
Challenger progressed very rapidly and without warning. Under those
circumstances, the Commission believes it is highly unlikely that any
of the systems discussed below, or any combination of those systems,
would have saved the flight 51-L crew.
FINDINGS
1. The Space Shuttle System was not designed to survive a failure of
the Solid Rocket Boosters. There are no corrective actions that can
be taken if the boosters do not operate properly after ignition, i.e.,
there is no ability to separate an Orbiter safely from thrusting
boosters and no ability for the crew to escape the vehicle during
first-stage ascent.
Neither the Mission Control Team not the 51-L crew had any warning
of impending disaster.
Even if there had been warning, there were no actions available to
the crew of the Mission Control Team to avert the disaster.
LANDING: Another Critical Phase
The consequences of faulty performance in any dynamic and demanding
flight environment can be catastrophic. The Commission was concerned
that an insufficient safety margin may have existed in areas other
than Shuttle ascent. Entry and landing of the Shuttle are dynamic and
demanding with all the risks and complications inherent in flying a
heavyweight glider with a very steep glide path. Since the Shuttle
crew cannot divert to any alternate landing site after entry, the
landing decision must be both timely and accurate. In addition, the
landing gear, which includes wheels, tires and brakes, must function
properly.
In summary, although there are valid programmatic reasons to land
routinely at Kennedy, there are concerns that suggest that this is not
wise under the present circumstances. While planned landings at
Edwards carry a cost in dollars and days, the realities of weather
cannot be ignored. Shuttle program officials must recognize that
Edwards is a permanent, essential part of the program. The cost
associated with regular scheduled landing and turnaround operations at
Edwards is thus a necessary program cost.
Decisions governing Space Shuttle operations must be consistent with
the philosophy that unnecessary risks have to be eliminated. Such
decisions cannot be made without a clear understanding of margins of
safety in each part of the system.
Unfortunately, margins of safety cannot be assured if performance
characteristics are not thoroughly understood, nor can they be deduced
from a previous flight's "success."
The Shuttle program cannot afford to operate outside its experience in
the areas of tires, brakes and weather, with the capabilities of the
system today. Pending a clear understanding of all landing and
deceleration systems, and a resolution of the problems encountered to
date in Shuttle landings, the most conservative course must be
followed in order to minimize risk during this dynamic phase of
flight.
SHUTTLE ELEMENTS
The Space Shuttle Main Engine teams at Marshall and Rocketdyne have
developed engines that have achieved their performance goals and have
performed extremely well. Nevertheless the main engines continue to
be highly complex and critical components of the Shuttle that involve
an element of risk principally because important components of the
engines degrade more rapidly with flight use than anticipated. Both
NASA and Rocketdyne have taken steps to contain that risk. An
important aspect of the main engine program has been the extensive
"hot fire" ground tests. Unfortunately, the vitality of the test
program has been reduced because of budgetary constraints.
The number of engine test firings per month has decreased over the
past two years. Yet this test program has not yet demonstrated the
limits of engine operation parameters or included tests over the full
operating envelope to show full engine capability. In addition, tests
have not yet been deliberately conducted to the point of failure to
determine actual engine operating margins.
PRESIDENTIAL COMMISSION ON THE SPACE SHUTTLE CHALLENGER ACCIDENT
William P. Rogers, Chairman
Former Secretary of State under President Nixon (1969-1973), and
Attorney General under President Eisenhower (1957-1961), currently a
practicing attorney and senior partner in the law firm of Rogers &
Wells. Born in Norfolk, New York, he was awarded the Medal of Freedom
in 1973. He holds a J.D. from Cornell University (1937) and served as
LCDR, U.S. Navy (1942-1946).
Neil A. Armstrong, Vice Chairman
Former astronaut, currently Chairman of the Board of Computing
Technologies for Aviation, Inc. Born in Wapakoneta, Ohio, Mr.
Armstrong was spacecraft commander for Apollo 11, July 16-24, 1969,
the first manned lunar landing mission. He was Professor of
Aeronautical Engineering at the University of Cincinnati from 1971 to
1980 and was appointed to the National Commission on Space in 1985.
David C. Acheson
Former Senior Vice President and General Counsel, Communications
Satellite Corporation (1967-1974), currently a partner in the law firm
of Drinker Biddle & Reath. Born in Washington, DC, he previously
served as an attorney with the U.S. Atomic Energy Commission
(1948-1950) and was U.S. Attorney for the District of Columbia
(1961-1965). He holds an LL.B. from Harvard University (1948) and
served as LT, U.S. Navy (1942-1946).
Dr. Eugene E. Covert
Educator and engineer. Born in Rapid City, South Dakota, he is
currently Professor and Head, Department of Aeronautics and
Astronautics, at Massachusetts Institute of Technology. Member of the
National Academy of Engineering, he was a recipient of the Exceptional
Civilian Service Award, USAF, in 1973 and the NASA Public Service
Award in 1980. He holds a Doctorate in Science from Massachusetts
Institute of Technology.
Dr. Richard P. Feynman
Physicist. Born in New York City, he is Professor of Theoretical
Physics at California Institute of Technology. Nobel Prize winner in
Physics, 1965, he also received the Einstein Award in 1954, the
Oersted Medal in 1972 and the Niels Bohr International Gold Medal in
1973. He holds a Doctorate in Physics from Princeton (1942).
Robert B. Hotz
Editor, publisher. Born in Milwaukee, Wisconsin. He is a graduate of
Northwestern University. He was the editor-in-chief of Aviation Week
& Space Technology magazine (1953-1980). He served in the Air Force
in World War II and was awarded the Air Medal with Oak Leaf Cluster.
Since 1982, he has been a member of the General Advisory Committee to
the Arms Control and Disarmament Agency.
Major General Donald J. Kutyna, USAF
Director of Space Systems and Command, Control, Communications. Born
in Chicago, Illinois, and graduate of the U.S. Military Academy, he
holds a Master of Science degree from Massachusetts Institute of
Technology (1965). A command pilot with over 4,000 flight hours, he
is a recipient of the Distinguished Service Medal, Distinguished
Flying Cross, Legion of Merit and nine air medals.
Dr. Sally K. Ride
Astronaut. Born in Los Angeles, California, she was a mission
specialist on STS-7, launched on June 18, 1983, becoming the first
American woman in space. She also flew on mission 41-G launched
October 5, 1984. She holds a Doctorate in Physics from Stanford
University (1978) and is still an active astronaut.
Robert W. Rummel
Space expert and aerospace engineer. Born in Dakota, Illinois, and
former Vice President of Trans World Airlines, he is currently
President of Robert W. Rummel Associates, Inc., of Mesa, Arizona. He
is a member of the National Academy of Engineering and is holder of
the NASA Distinguished Public Service Medal.
Joseph F. Sutter
Aeronautical engineer. Currently Executive Vice President of the
Boeing Commercial Airplane Company. Born in Seattle, he has been with
Boeing since 1945 and was a principal figure in the development of
three generations of jet aircraft. In 1984, he was elected to the
National Academy of Engineering. In 1985, President Reagan conferred
on him the U.S. National Medal of Technology.
Dr. Arthur B. C. Walker, Jr.
Astronomer. Born in Cleveland, Ohio, he is currently Professor of
Applied Physics and was formerly Associate Dean of the Graduate
Division at Stanford University. Consultant to Aerospace Corporation,
Rand Corporation and the National Science Foundation, he is a member
of the American Physical Society, American Geophysical Union, and the
American Astronomy Society. He holds a Doctorate in Physics from the
University of Illinois (1962).
Dr. Albert D. Wheelon
Physicist. Born in Moline, Illinois, he is currently Executive Vice
President, Hughes Aircraft Company. Also a member of the President's
Foreign Intelligence Advisory Board, he served as a consultant to the
President's Science Advisory Council from 1961 to 1974. He holds a
Doctorate in Physics from Massachusetts Institute of Technology
(1952).
Brigadier General Charles Yeager, USAF (Retired)
Former experimental test pilot. Born in Myra, West Virginia, he was
appointed in 1985 as a member of the National Commission on Space. He
was the first person to penetrate the sound barrier and the first to
fly at a speed of more than 1,600 miles an hour.
Dr. Alton G. Keel, Jr., Executive Director
Detailed to the Commission from his position in the Executive Office
of the President, Office of Management and Budget, as Associate
Director for National Security and International Affairs; formerly
Assistant Secretary of the Air Force for Research, Development and
Logistics; and Senate Staff. Born in Newport News, Virginia, he
holds a Doctorate in Engineering Physics from the University of
Virginia (1970).
PRESIDENTIAL COMMISSION STAFF
Dr. Alton G. Keel, Jr. Executive Director White House
Thomas T. Reinhardt Executive Secretary MAJ, USA/OMB
Special Assistants
Marie C. Hunter Executive Assistant Rogers & Wells
to the Chairman
M. M. Black Personal Secretary OMB
to Vice Chairman &
Executive Director
Mark D. Weinberg Media Relations White House
Herb Hetu Media Relations Consultant
John T. Shepherd NASA Tasking CAPT, USN(Ret)/Atty.
Coordination
Administrative Staff
Steven B. Hyle Administrative Officer LTC, USAF
Patt Sullivan Administrative Assistant NASA
Marilyn Stumpf Travel Coordination NASA
Joleen A. B. Bottalico Travel Coordination NASA
Jane M. Green Secretary NASA
Lorraine K. Walton Secretary NASA
Vera A. Barnes Secretary NASA
Virginia A. James Receptionist Contract Support
Investigative Staff
William G. Dupree Investigator, Development DOD IG
and Production
John B. Hungerford, Jr. Investigator, Development LTC, USAF
and Production
John P. Chase Investigator, MAJ, USMC/DOD IG
Pre-Launch Activities
Brewster Shaw Investigator, LTC, USAF/NASA
Pre-Launch Activities Astronaut
John C. Macidull Investigator, Accident FAA/CDR, USNR-R
Analysis
Ron Waite Investigator, Accident Engineering
Analysis Consultant
John Fabian Investigator Mission COL, USAF/Former
Planning & Operations Astronaut
Emily M. Trapnell Coordinator, General FAA Atty.
Investigative Activities
Randy R. Kehrli Evidence Analysis DOJ Atty.
E. Thomas Almon Investigator Special Agent, FBI
Patrick J. Maley Investigator Special Agent, FBI
John R. Molesworth, Jr. Investigator Special Agent, FBI
Robert C. Thompson Investigator Special Agent, FBI
Dr. R. Curtis Graeber Human Factors Specialist LTC, USA/NASA
Michael L. Marx Metallurgist NTSB
Writing Support
Woods Hansen Editor Free Lance
James Haggerty Writer Free Lance
Anthony E. Hartle Writer COL, USA/USMA
William Bauman Writer CAPT, USAF/USAFA
Frank Gillen Word Processing Supervisor Contract Support
Lawrence J. Herb Art Layout Free Lance
Willis Rickert Printer NASA
Lynne Komai Design Contract Support
Documentation Support
Clarisse Abramidis Case Manager DOJ
Fritz Geurtsen Project Manager DOJ
John Dunbar Contract Representative Contract Support
Valarie Lease Support Center Supervisor Contract Support
Stephen M. Croll Correspondence Support Contract Support
Independent Test Observers
Eugene G. Haberman Rocket Propulsion Lab USAF
Wilbur W. Wells Rocket Propulsion Lab USAF
Don E. Kennedy TRW Ballistic Missile Office Pro Bono
Laddie E.Dufka Aerospace Corp Pro Bono
Mohan Aswani Aerospace Corp Pro Bono
Michael L. Marx Metallurgist NTSB
COMMISSION ACTIVITIES
An Overview
President Reagan, seeking to ensure a thorough and unbiased
investigation of the Challenger accident, announced the formation of
the Commission on February 3, 1986. The mandate given by the
President, contained in Executive Order 12546, required Commission
members to:
(1) Review the circumstances surrounding the accident to establish
the probable cause or causes of the accident; and,
(2) Develop recommendations for corrective or other action based
upon the Commission's findings and determinations.
The Commission itself divided into four investigative panels:
1. Development and Production, responsible for investigating the
acquisition and test and evaluation processes for the Space Shuttle
elements;
2. Pre-Launch Activities, responsible for assessing the Shuttle
system processing, launch readiness process and pre-launch security;
3. Mission Planning and Operations, responsible for investigating
mission planning and operations, schedule pressures and crew safety
areas; and
4. Accident Analysis, charged with analyzing the accident data and
developing both an anomaly tree and accident scenarios.
More than 160 individuals were interviewed and more than 35 formal
panel investigative sessions were held generating almost 12,000 pages
of transcript. Almost 6,300 documents, totaling more than 122,000
pages, and hundreds of photographs were examined and made a part of
the Commission's permanent data base and archives. These sessions and
all the data gathered added to the 2,800 pages of hearing transcript
generated by the Commission in both closed and open sessions.
In addition to the work of the Commission and the Commission staff,
NASA personnel expended a vast effort in the investigation. More than
1,300 employees from all NASA facilities were involved and were
supported by more than 1,600 people from other government agencies and
over 3,100 from NASA's contractor organizations. Particularly
significant were the activities of the military, the Coast Guard and
the NTSB in the salvage and analysis of the Shuttle wreckage.
RECOMMENDATIONS OF THE PRESIDENTIAL COMMISSION
The Commission has conducted an extensive investigation of the
Challenger accident to determine the probable cause and necessary
corrective actions. Based on the findings and determinations of its
investigation, the Commission has unanimously adopted recommendations
to help assure the return to safe flight.
The Commission urges that the Administrator of NASA submit, one year
from now, a report to the President on the progress that NASA has made
in effecting the Commission's recommendations set forth below:
I
DESIGN
The faulty Solid Rocket Motor joint and seal must be changed. This
could be a new design eliminating the joint or a redesign of the
current joint and seal. No design options should be prematurely
precluded because of schedule, cost or reliance on existing hardware.
All Solid Rocket Motor joints should satisfy the following
requirements:
The joints should be fully understood, tested and verified.
The integrity of the structure and of the seals of all joints should
be not less than that of the case walls throughout the design
envelope.
The integrity of the joints should be insensitive to:
--Dimensional tolerances.
--Transportation and handling.
--Assembly procedures.
--Inspection and test procedures.
--Environmental effects.
--Internal case operating pressure.
--Recovery and reuse effects.
--Flight and water impact loads.
The certification of the new design should include:
--Tests which duplicate the actual launch configuration as closely
as possible.
--Tests over the full range of operating conditions, including
temperature.
Full consideration should be given to conducting static firings of
the exact flight configuration in a vertical attitude.
INDEPENDENT OVERSIGHT
The Administrator of NASA should request the National Research Council
to form an independent Solid Rocket Motor design oversight committee
to implement the Commission's design recommendations and oversee the
design effort. This committee should:
Review and evaluate certification requirements.
Provide technical oversight of the design, test program and
certification.
Report to the Administrator of NASA on the adequacy of the design
and make appropriate recommendations.
II
SHUTTLE MANAGEMENT STRUCTURE
The Shuttle Program Structure should be reviewed. The project
managers for the various elements of the Shuttle program felt more
accountable to their center management than to the Shuttle program
organization. Shuttle element funding, work package definition, and
vital program information frequently bypass the National STS (Shuttle)
Program Manager.
A redefinition of the Program Manager's responsibility is essential.
This redefinition should give the Program Manager the requisite
authority for all ongoing STS operations. Program funding and all
Shuttle Program work at the centers should be placed clearly under the
Program Manager's authority.
ASTRONAUTS IN MANAGEMENT
The Commission observes that there appears to be a departure from the
philosophy of the 1960s and 1970s relating to the use of astronauts in
management positions. These individuals brought to their positions
flight experience and a keen appreciation of operations and flight
safety.
NASA should encourage the transition of qualified astronauts into
agency management positions.
The function of the Flight Crew Operations director should be
elevated in the NASA organization structure.
SHUTTLE SAFETY PANEL
NASA should establish an STS Safety Advisory Panel reporting to the
STS Program Manager. The Charter of this panel should include Shuttle
operational issues, launch commit criteria, flight rules, flight
readiness and risk management. The panel should include
representation from the safety organization, mission operations, and
the astronaut office.
III
CRITICALITY REVIEW AND HAZARD ANALYSIS
NASA and the primary Shuttle contractors should review all Criticality
1, 1R, 2, and 2R items and hazard analyses. This review should
identify those items that must be improved prior to flight to ensure
mission safety. An Audit Panel, appointed by the National Research
Council, should verify the adequacy of the effort and report directly
to the Administrator of NASA.
IV
SAFETY ORGANIZATION
NASA should establish an Office of Safety, Reliability and Quality
Assurance to be headed by an Associate administrator, reporting
directly to the NASA Administrator. It would have direct authority
for safety, reliability, and quality assurance throughout the agency.
The office should be assigned the work force to ensure adequate
oversight of its functions and should be independent of other NASA
functional and program responsibilities.
The responsibilities of this office should include:
The safety, reliability and quality assurance functions as they
relate to all NASA activities and programs.
Direction of reporting and documentation of problems, problem
resolution and trends associated with flight safety.
V
IMPROVED COMMUNICATIONS
The Commission found that Marshall Space Flight Center project
managers, because of a tendency at Marshall to management isolation,
failed to provide full and timely information bearing on the safety of
flight 51-L to other vital elements of Shuttle program management.
NASA should take energetic steps to eliminate this tendency at
Marshall Space Flight Center, whether by changes of personnel,
organization, indoctrination or all three.
A policy should be developed which governs the imposition and
removal of Shuttle launch constraints.
Flight Readiness Reviews and Mission Management Team meetings should
be recorded.
The flight crew commander, or a designated representative, should
attend the Flight Readiness Review, participate in acceptance of the
vehicle for flight, and certify that the crew is properly prepared for
flight.
VI
LANDING SAFETY
NASA must take actions to improve landing safety.
The tire, brake and nosewheel steering systems must be improved.
These systems do not have sufficient safety margin, particularly at
abort landing sites.
The specific conditions under which planned landings at Kennedy
would be acceptable should be determined. Criteria must be
established for tires, brakes and nosewheel steering. Until the
systems meet those criteria in high fidelity testing that is verified
at Edwards, landing at Kennedy should not be planned.
Committing to a specific landing site requires that landing area
weather be forecast more than an hour in advance. During
unpredictable weather periods at Kennedy, program officials should
plan on Edwards landings. Increased landings at Edwards may
necessitate a dual ferry capability.
VII
LAUNCH ABORT AND CREW ESCAPE
The Shuttle program management considered first-stage abort options
and crew escape options several times during the history of the
program, but because of limited utility, technical infeasibility, or
program cost and schedule, no systems were implemented. The
Commission recommends that NASA:
Make all efforts to provide a crew escape system for use during
controlled gliding flight.
Make every effort to increase the range of flight conditions under
which an emergency runway landing can be successfully conducted in the
event that two or three main engines fail early in ascent.
VIII
FLIGHT RATE
The nation's reliance on the Shuttle as its principal space launch
capability created a relentless pressure on NASA to increase the
flight rate. Such reliance on a single launch capability should be
avoided in the future.
NASA must establish a flight rate that is consistent with its
resources. A firm payload assignment policy should be established.
The policy should include rigorous controls on cargo manifest changes
to limit the pressures such changes exert on schedules and crew
training.
IX
MAINTENANCE SAFEGUARDS
Installation, test, and maintenance procedures must be especially
rigorous for Space Shuttle items designated Criticality 1. NASA
should establish a system of analyzing and reporting performance
trends of such items.
Maintenance procedures for such items should be specified in the
Critical Items List, especially for those such as the liquid-fueled
main engines, which require unstinting maintenance and overhaul.
With regard to the Orbiters, NASA should:
Develop and execute a comprehensive maintenance inspection plan.
Perform periodic structural inspections when scheduled and not
permit them to be waived.
Restore and support the maintenance and spare parts programs, and
stop the practice of removing parts from one Orbiter to supply
another.
CONCLUDING THOUGHT
The Commission urges that NASA continue to receive the support of the
Administration and the nation. The agency constitutes a national
resource that plays a critical role in space exploration and
development. It also provides a symbol of national pride and
technological leadership.
The Commission applauds NASA's spectacular achievements of the past
and anticipates impressive achievements to come. The findings and
recommendations presented in this report are intended to contribute to
the future NASA successes that the nation both expects and requires as
the 21st century approaches.
NASA ACTIONS TO IMPLEMENT COMMISSION RECOMMENDATIONS
(Source: Actions to Implement the Recommendations of The Presidential
Commission on the Space Shuttle Challenger Accident, Executive Summary, July
14, 1986, NASA Headquarters)
On June 13, 1986, the President directed NASA to implement, as soon as
possible, the recommendations of the Presidential Commission on the
Space Shuttle Challenger Accident. The President requested that NASA
report, within 30 days, how and when the recommendations will be
implemented, including milestones by which progress can be measured.
In the months since the Challenger accident, the NASA team has spent
many hours in support of the Presidential Commission on the Space
Shuttle Challenger Accident and in planning for a return of the
Shuttle to safe flight status. Chairman William P. Rogers and the
other members of the Commission have rendered the Nation and NASA an
exceptional service. The work of the Commission was extremely
thorough and comprehensive. NASA agrees with the Commission's
recommendations and is vigorously pursuing the actions required to
implement and comply with them.
As a result of the efforts in support of the Commission, many of the
actions required to safely return the Space Shuttle to flight status
have been under way since March. On March 24, 1986, the Associate
Administrator for Space Flight outlined a comprehensive strategy, and
defined major actions, for safely returning to flight status. The
March 24 memorandum (Commission Activities: An Overview) provided
guidance on the following subjects:
actions required prior to next flight,
first flight/first year operations, and
development of sustainable safe flight rate.
The Commission report was submitted to the President on June 9, 1986.
Since that time, NASA has taken additional actions and provided
direction required to comply with the Commission's recommendations.
The NASA Administrator and the Associate Administrator for Space
Flight will participate in the key management decisions required for
implementing the Commission recommendations and for returning the
Space Shuttle to flight status. NASA will report to the President on
the status of the implementation program in June 1987.
The Commission report included nine recommendations, and a summary of
the implementation status for each is provided:
RECOMMENDATION I
Solid Rocket Motor Design:
On March 24, 1986, the Marshall Space Flight Center (MSFC) was
directed to form a Solid Rocket Motor (SSRM) joint redesign team to
include participation from MSFC and other NASA centers as well as
individuals from outside NASA. The team includes personnel from
Johnson Space Center, Kennedy Space Center, Langley Research Center,
industry, and the Astronaut Office. To assist the redesign team, an
expert advisory panel was appointed which includes 12 people with six
coming from outside NASA.
The team has evaluated several design alternatives, and analysis and
testing are in progress to determine the preferred approaches which
minimize hardware redesign. To ensure adequate program contingency in
this effort, the redesign team will also develop, at least through
concept definition, a totally new design which does not utilize
existing hardware. The design verification and certification program
will be emphasized and will include tests which duplicate the actual
launch loads as closely as feasible and provide for tests over the
full range of operating conditions. The verification effort includes
a trade study which has been under way for several weeks to determine
the preferred test orientation (vertical or horizontal) of the
full-scale motor firings. The Solid Rocket Motor redesign and
certification schedule is under review to fully understand and plan
for the implementation of the design solutions as they are finalized
and assessed. The schedule will be reassessed after the SRM
Preliminary Design Review in September 1986. At this time it appears
that the first launch will not occur prior to the first quarter of
1988.
Independent Oversight:
In accordance with the Commission's recommendation, the National
Research Council (NRC) has established an Independent Oversight Group
chaired by Dr. H. Guyford Stever and reporting to the NASA
Administrator. The NRC Oversight Group has been briefed on Shuttle
system requirements, implementation, and control; Solid Rocket Motor
background; and candidate modifications. The group has established a
near-term plan that includes briefings and visits to review inflight
loads; assembly processing; redesign status; and other solid rocket
motor designs, including participation in the Solid Rocket Motor
preliminary design review in September 1986.
RECOMMENDATION II
Shuttle Management Structure:
The Administrator has appointed General Sam Phillips, who served as
Apollo Program Director, to study every aspect of how NASA manages its
programs, including relationships between various field centers and
NASA Headquarters. General Phillips has broad authority from the
Administrator to explore every aspect of NASA organization, management
and procedures. His activities will include a review of the Space
Shuttle management structure.
On June 25, 1986, Astronaut Robert Crippen was directed to form a
fact-finding group to assess the Space Shuttle management structure.
The group will report recommendations to the Associate Administrator
for Space Flight by August 15, 1986. Specifically, this group will
address the roles and responsibilities of the Space Shuttle Program
Manager to assure that the position has the authority commensurate
with its responsibilities. In addition, roles and responsibilities at
all levels of program management will be reviewed to specify the
relationship between the program organization and the field center
organizations. The results of this study will be reviewed with
General Phillips and the Administrator with a decision on
implementation of the recommendations by October 1, 1986.
Astronauts in Management
Rear Admiral Richard Truly, a former astronaut, has been appointed as
Associate Administrator for the Office of Space Flight. Several
active astronauts are currently serving in management positions in the
agency. The Crippen group will address means to stimulate the
transition of astronauts into other management positions. It will
also determine the appropriate position for the Flight Crew Operations
Directorate within the NASA organizational structure.
Shuttle Safety Panel
A Shuttle Safety Panel will be established by the Associate
Administrator for Space Flight not later than September 1, 1986, with
direct access to the Space Shuttle Program Manager. This date allows
time to determine the structure and function of this panel, including
an assessment of its relationship to the newly formed Office of
Safety, Reliability, and Quality Assurance, and to the existing
Aerospace Safety Advisory Panel.
RECOMMENDATION III
Critical Item Review and Hazard Analysis
On March 13, 1986, NASA initiated a complete review of all Space
Shuttle program failure modes and effects analyses (FEMEA's) and
associated critical item lists (CIL's). Each Space Shuttle project
element and associated prime contractor is conducting separate
comprehensive reviews which will culminate in a program-wide review
with the Space Shuttle program have been assigned as formal members of
each of these review teams. All Criticality 1 and 1R critical item
waivers have been cancelled. The teams are required to reassess and
resubmit waivers in categories recommended for continued program
applicability. Items which cannot be revalidated will be redesigned,
qualified, and certified for flight. All Criticality 2 and 3 CIL's
are being reviewed for reacceptance and proper categorization. This
activity will culminate in a comprehensive final review with NASA
Headquarters beginning in March 1987.
As recommended by the Commission, the National Research Council has
agreed to form an Independent Audit Panel, reporting to the NASA
Administrator, to verify the adequacy of this effort.
RECOMMENDATION IV
Safety Organization
The NASA Administrator announced the appointment of Mr. George A.
Rodney to the position of Associate Administrator for Safety,
Reliability, and Quality Assurance on July 8, 1986. The
responsibilities of this office will include the oversight of safety,
reliability, and quality assurance functions related to all NASA
activities and programs and the implementation of a system for anomaly
documentation and resolution to include a trend analysis program. One
of the first activities to be undertaken by the new Associate
Administrator will be an assessment of the resources including
workforce required to ensure adequate execution of the safety
organization functions. In addition, the new Associate Administrator
will assure appropriate interfaces between the functions of the new
safety organization and the Shuttle Safety Panel which will be
established in response to the Commission Recommendation II.
RECOMMENDATION V
Improved Communications
On June 25, 1986, Astronaut Robert Crippen was directed to form a team
to develop plans and recommended policies for the following:
Implementation of effective management communications at all levels.
Standardization of the imposition and removal of STS launch
constraints and other operational constraints.
Conduct of Flight Readiness Review and Mission Management Team
meetings, including requirements for documentation and flight crew
participation.
Since this recommendation is closely linked with the recommendation on
Shuttle management structure, the study team will incorporate the plan
for improved communications with that for management restructure.
This review of effective communications will consider the activities
and information flow at NASA Headquarters and the field centers which
support the Shuttle program. The study team will present findings and
recommendations to the Associate Administrator for Space Flight by
August 15, 1986.
RECOMMENDATION VI
Landing Safety
A Landing Safety Team has been established to review and implement the
Commission's findings and recommendations on landing safety. All
Shuttle hardware and systems are undergoing design reviews to insure
compliance with the specifications and safety concerns. The tires,
brakes, and nose wheel steering system are included in this activity,
and funding for a new carbon brakes system has been approved. Runway
surface tests and landing aid requirement reviews had been under way
for some time prior to the accident and are continuing. Landing aid
implementation will be complete by July 1987. The interim brake
system will be delivered by August 1987. Improved methods of local
weather forecasting and weather-related support are being developed.
Until the Shuttle program has demonstrated satisfactory safety margins
through high fidelity testing and during actual landings at Edwards
Air Force Base, the Kennedy Space Center landing site will not be used
for nominal end-of-mission landings. Dual Orbiter ferry capability
has been an issue for some time and will be thoroughly considered
during the upcoming months.
RECOMMENDATION VII
Launch Abort and Crew Escape
On April 7, 1986, NASA initiated a Shuttle Crew Egress and Escape
review. The scope of this analysis includes egress and escape
capabilities from launch through landing and will provide analyses,
concepts, feasibility assessments, cost, and schedules for pad abort,
bailout, ejection systems, water landings, and powered flight
separation. This review will specifically assess options for crew
escape during controlled gliding flight and options for extending the
intact abort flight envelope to include failure of 2 or 3 main engines
during the early ascent phase. In conjunction with this activity, a
Launch Abort Reassessment Team was established to review all launch
and launch abort rules to ensure that launch commit criteria, flight
rules, range safety systems and procedures, landing aids, runway
configurations and lengths, performance versus abort exposure, abort
and end-of-mission landing weights, runway surfaces, and other
landing-related capabilities provide the proper margin of safety to
the vehicle and crew. Crew escape and launch abort studies will be
complete on October 1, 1986, with an implementation decision in
December 1986.
RECOMMENDATION VIII
Flight Rate
In March 1986 NASA established a Flight Rate Capability Working
Group. Two flight rate capability studies are under way:
(1) a study of capabilities and constraints which govern the Shuttle
processing flows at the Kennedy Space Center and
(2) a study by the Johnson Space Center to assess the impact of
flight specific crew training and software delivery/certification on
flight rates.
The working group will present flight rate recommendations to the
Office of Space Flight by August 15, 1986. Other collateral studies
are still in progress which address Presidential Commission
recommendations related to spares provisioning, maintenance, and
structural inspection. This effort will also consider the National
Research Council independent review of flight rate which is under way
as a result of a Congressional Subcommittee request.
NASA strongly supports a mixed fleet to satisfy launch requirements
and actions to revitalize the United States expendable launch vehicle
capabilities.
Additionally, a new cargo manifest policy is being formulated by NASA
Headquarters which will establish manifest ground rules and impose
constraints to late changes. Manifest control policy recommendations
will be completed in November 1986.
RECOMMENDATION IX
Maintenance Safeguards
A Maintenance Safeguards Team has been established to develop a
comprehensive plan for defining and implementing actions to comply
with the Commission recommendations concerning maintenance
activities. A Maintenance Plan is being prepared to ensure that
uniform maintenance requirements are imposed on all elements of the
Space Shuttle program. This plan will define the structure that will
be used to document
(1) hardware inspections and schedules,
(2) planned maintenance activities,
(3) Maintenance procedures configuration control, and
(4) Maintenance logistics.
The plan will also define organizational responsibilities, reporting,
and control requirements for Space Shuttle maintenance activities.
The maintenance plan will be completed by September 30, 1986.
A number of other activities are underway which will contribute to a
return to safe flight and strengthening the NASA organization. A
Space Shuttle Design Requirements Review Team headed by the Space
Shuttle Systems Integration Office at Johnson Space Center has been
assigned to review all Shuttle design requirements and associated
technical verification. The team will focus on each Shuttle project
element and on total Space Shuttle system design requirements. This
activity will culminate in a Space Shuttle Incremental Design
Certification Review approximately 3 months prior to the next Space
Shuttle Launch.
In consideration of the number, complexity, and interrelationships
between the many activities leading to the next flight, the Space
Shuttle Program Manager at Johnson Space Center has initiated a series
of formal Program Management Reviews for the Space Shuttle program.
These reviews are structured to be regular face-to-face discussions
involving the managers of all major Space Shuttle program activities.
Specific subjects to be discussed at each meeting will focus on
progress, schedules, and actions associated with each of the major
program review activities and will be tailored directly to current
program activity for the time period involved. The first of these
meetings was held at Marshall Space Flight Center on May 5-6, 1986,
with the second at Kennedy Space Center on June 25, 1986. Follow-on
reviews will be held approximately every 6 weeks. Results of these
reviews will be reported to the Associate Administrator for Space
Flight and to the NASA Administrator.
On June 19, 1986, the NASA Administrator announced termination of the
development of the Centaur upper stage for use aboard the Space
Shuttle. Use of the Centaur upper stage was planned for NASA
planetary spacecraft launches as well as for certain national security
satellite launches. Majority safety reviews of the Centaur system
were under way at the time of the Challenger accident, and these
reviews were intensified in recent months to determine if the program
should be continued. The final decision to terminate the Centaur
stage for use with the Shuttle was made on the basis that even
following certain modifications identified by the ongoing reviews, the
resultant stage would not meet safety criteria being applied to other
cargo or elements of the Space Shuttle System. NASA has initiated
efforts to examine other launch vehicle alternatives for the major
NASA planetary and scientific payloads which were scheduled to utilize
the Centaur upper stage. NASA is providing assistance to the
Department of Defense as it examines alternatives for those national
security missions which had planned to use the Shuttle/Centaur.
The NASA Administrator has announced a number of Space Station
organizational and management structural actions designed to
strengthen technical and management capabilities in preparation for
moving into the development phase of the Space Station program. The
decision to create the new structure is the result of recommendations
made to the Administrator by a committee, headed by General Phillips,
which is conducting a long range assessment of NASA's overall
capabilities and requirements.
Finally, NASA is developing plans for increased staffing in critical
areas and is working closely with the Office of Personnel Management
to develop a NASA specific proposal which would provide for needed
changes to the NASA personnel management system to strengthen our
ability to attract, retain, and motivate the quality workforce
required to conduct the NASA mission.
(Source: The Presidential Commission on the Space Shuttle Challenger
Accident Report, June 6, 1986)
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