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Shuttle
Triumphs and Tragedies |
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The Challenger Accident
"The exploration of
space will never be without risk. But it is mandatory
that we use the best technology, human expertise,
and human dedication available to minimize that
risk at all times. And, it is certain that the
benefits to humanity are worth the risk we cannot
avoid." -Astronaut John Young, technical director, Johnson Space Center, Apollo
astronaut and commander of the first Space Shuttle
"If
we die, we want people to accept it. We are in
a risky business, and we hope that if anything
happens to us it will not delay the program. The
conquest of space is worth the risk of life."
-Astronaut
Virgil I. Grissom (On January 27, 1967, astronauts
Grissom, Ed White, and Roger Chaffee died from a
flash fire aboard the Apollo 204 Spacecraft).
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The Space Shuttle Challenger
and its seven-member crew were lost 73 seconds
after launch on January 28, 1986, when a booster
failure resulted in breakup of the vehicle. Beginning
at about 72 seconds into the flight, a series
of events occurred extremely rapidly that terminated
the flight.
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| Just after liftoff at 0.678 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. |
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This area of the solid
booster faces the external tank. The vaporized material
streaming from the joint indicated that there was
not complete sealing action within the joint. These
joints hold each of the four sections of the SRBs
together and were sealed by two rubber O-rings gaskets.
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The dense black smoke
puffs suggest that the grease joint insulation
and the rubber O-rings in the joint seal were
being burned and eroded by the +5000°F propellant
gases.
Main
engines had been throttled up to 104% thrust and
the solid rocket boosters were increasing their
thrust when the first flame appeared on the right
solid rocket booster in the area of the joint.
That
flame 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 to the external tank. The growing flame
also encroached on the strut attaching the solid
rocket booster to the external tank.
The
first visual indication that flame from the solid
rocket booster breached the external tank was
at 64.66 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. Data from the hydrogen tank
pressurization confirmed the leak.
At
about 72.20 seconds, the lower strut linking the
solid rocket booster and the external tank, was
severed from the weakened hydrogen tank permitting
the right solid rocket booster to rotate.
At 73.124 seconds, a white vapor pattern was observed
blooming from the side of the external tank. This
was the beginning of the structural failure of
hydrogen tank that culminated in the entire bottom
dropping away. This released massive amounts of
liquid hydrogen from the tank, which 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.
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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 Mach 1.92 at an altitude of 46,000
feet, the Challenger was totally enveloped in an
explosion.
The Orbiter broke into several
large sections, including 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. The explosion 73 seconds after liftoff
claimed crew and vehicle. |
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Cause of explosion was
determined to be a failure of the aft joint seal
(O-ring) in the right solid rocket booster. Cold
weather was a contributing factor. The extreme cold
allowed the gas to leak around the unpressurized
O-rings, burning the connecting strut of the SRB
and allowing it to tilt away from the spacecraft
and ripping the structure apart.
After
the Challenger accident, the Space Shuttle Program
was put on hold so that a variety of safety and
emergency upgrades could be made in addition to
the redesign of the solid rocket boosters.
The redesign of the O-rings in the SRBs included
the addition of a third pressurized O-ring on the
outside of the inner two which improves the seal
and greatly strengthens the physical connection
between the segments to compensate for the extreme
forces that occur during launch and firing of the
SRBs. Heaters were added to the joints to prevent
cold weather from affecting the sealing capability
of the O-rings. Click
here to read more about the many Shuttle
redesigns after the Challenger accident.
In
addition to the redesign of the solid rocket booster,
extensive landing safety improvements were made including
upgrades of the Orbiter tires, brakes, and nosewheel
steering mechanism, and a drag chute system was added.
Numerous
other hardware, software, and safety improvements
were incorporated, including the installation of a
crew escape system that allows astronauts under certain
conditions to parachute from the Orbiter .
The
astronauts now wear an orange launch and entry suit
that is equipped with a parachute, life raft, water,
rations, radio, flares, water dyes and other life
saving equipment in case they need to eject from the
Shuttle in an emergency. Click
here for a short tutorial on space training.
Changes
were made in the software of the Orbiter's general-purpose
computers. The software changes, which were required
for transatlantic-landing and glide-return-to-launch-site
abort modes, provide the Orbiter with an automatic-mode,
that in turn provides the Orbiter with an automatic
stable flight for crew bailout. This software change
is required to allow the flight crew commander's departure,
automatically controlling the Orbiter's velocity and
angle-of-attack during bailout. Click
here for more information about this type
of emergency egress of the vehicle.
The Space
Shuttle Program was reorganized over the following
year and risk identification and reduction programs
were put in place. Click
here to read more about the reorganization.
For details
on the O-ring failure, click
here.
To
read a full account of the accident, click
here.
To read the Report of the
Presidential Commission, click
here.
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The Challenger crew |
The crew
was composed of Commander Francis R. Scobee, Pilot
Michael J. Smith, Mission Specialist Judith A.
Resnik, Mission Specialist Ellison S. Onizuka,
Mission Specialist Ronald E. McNair, Payload Specialist
Gregory B. Jarvis, and Payload Specialist Sharon
Christa McAuliffe.
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Click
here to read more about the crew, including
the first teacher in space, Christa McAuliffe.
For
videos of the crew and flight, click
here.
Many
questions are often asked about whether the crew
was conscious or not, or for how long after the
accident. Former astronaut and investigator
Joseph Kerwin's report, which can be read
here, explains the evidence that was collected
on this point.
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Views of ice on the launch pad |
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Click
here for a memorial montage video from CNN.
Click
here for the Life magazine story,
Challenger Ten Years Later.
"The best way
to honor the memories of the crew of the Challenger,
and of all the men and women who have given their
lives to explore the frontiers of air and space,
is to continue their bold tradition of exploration
and innovation. That's what the people of NASA
do every day. They push the boundaries of knowledge
and human endeavor to improve and enrich life
on Earth today and secure a better future for
all of us tomorrow. I've said many times that
safety is the highest priority at today's NASA.
We will not waver from that commitment. But human
beings have always taken great risks to reap great
rewards. Space flight is inherently dangerous
and every member of the NASA team understands
those risks." - former NASA Administrator
Dan Goldin
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The
Challenger accident had profound effects on the
U.S. space program. On August 15, 1986, President
Reagan announced that "NASA will no longer
be in the business of launching private satellites."
A 1992 White House advisory committee concluded
that the recovery from the Challenger disaster cost
the country $12 billion, which included the cost
of building the replacement Orbiter Endeavour.
It took
NASA 32 months after the Challenger accident to
redesign and requalify the Solid Rocket Booster
and return the Shuttle to flight. The first
post-Challenger flight, Discovery, was launched
on September 29, 1988. In almost 15 years
between the return to flight after the Challenger
accident and 2003, the Shuttle was being used on
a regular basis to conduct space-based research,
and, in line with NASA's original 1969 vision, to
build and service the space station. The Shuttle
flew 87 missions during this period, compared to
24 before Challenger. |
The
Columbia Accident
"In
an age when spaceflight has come to seem almost
routine, it is easy to overlook the dangers of
travel by rocket, and the difficulties of navigating
the fierce outer atmosphere of the Earth.
These astronauts knew the dangers, and they faced
them willingly, knowing they had a high and noble
purpose in life."
-President
George W. Bush
"From our orbital vantage,
we observe an earth without borders, full of peace,
beauty and magnificence, and we pray that humanity
as a whole can imagine a borderless world as we
see it and strive to live as one in peace."
-Wiliam
McCool, January 29, 2003
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The
Columbia STS-107 mission lifted off on January 16,
2003, for a 17-day science mission featuring numerous
microgravity experiments.
A Space
Shuttle contingency was declared in Mission Control,
Houston, as a result of the loss of communication
with the Space Shuttle Columbia as it descended
toward a landing at the Kennedy Space Center, Florida
on February 1, 2003..
It was scheduled to touchdown at 9:16 a.m. EST.
Communication and tracking of the shuttle was lost
at 9 a.m. EST at an altitude of about 203,000 feet
in the area above north central Texas. At the time
communications were lost, the shuttle was traveling
approximately 12,500 miles per hour (Mach 18). No
communication and tracking information were received
in Mission Control after that time. The orbiter
and its seven crewmembers were lost. |
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The physical
cause of the loss was due to a breach in the Thermal
Protection System on the leading edge of the left
wing. The breach was initiated when falling
foam from the External Tank struck the Reinforced
Carbon Carbon panels on the underside of the left
wing that occurred 81.9 seconds after launch.
During re-entry, this breach in the Thermal Protection
System allowed super heated air to penetrate the
leading edge insulation and melt and destroy the
aluminum structure of the left, resulting in a weakening
of the structure until increasing aerodynamic forces
caused loss of control, failure of the wing, and
breakup of the Orbiter.
Evidence
was derived from film and video of the launch, radar
images of Columbia on orbit, and amateur video of
debris shedding during the in-flight breakup.
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| The American people stood
with NASA during this time of tragedy. Volunteers
from across the country joined the efforts to recover
Columbia. Individuals gave their time and energy
to search an area the size of Rhode Island on foot
and from air. Many websites are set-up to remember
Columbia. Click
here to view one of them. |
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Columbia Accident Investigation Board was established
within two hours of the loss of signal from the
returning spacecraft in accordance with procedures
established 17 years earlier following the Challenger
accident.
In this
process, the Board identified a number of pertinent
factors:
1. physical
failures that led directly to the Columbia's destruction,
2. underlying
weaknesses, revealed in NASA's organization and
history, that can pave the way to catastrophic failure,
and
3. "other
significant observations" made during the course
of the investigation, but which may be unrelated
"For
all those inspired by flight, and for the nation
where powered flight was first achieved, the year
2003 had long been anticipated as one of celebration
- December 17 would mark the centennial of the day
the Wright Flyer first took to the air. But
2003 began instead on a note of a sudden and profound
loss." - Columbia Accident Investigation
Board
To read
the full Columbia Accident Investigation Board report,
click here. |
The Columbia Crew |
The crew was composed of Commander
Rick D. Husband, Pilot William C. McCool, Payload
Specialist Michael P. Anderson, Mission Specialist
Kalpana Chawla, Mission Specialist David M. Brown,
Mission Specialist Laurel B. Clark, and Payload Specialist
Ilan Ramon, Israel. |
| To read more about the crew,
click
here. |
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