Edited by Gerald Boerner

    

    
Commentary:

JerryPhoto_thumb2_thumb_thumb_thumb_I remember that day back in 1986, when we were watching the launch Christa McAuliffe, the first educator, into space. Then we watched in horror and unbelief when the Challenger exploded a little over a minute into the flight. This was a sobering time and a time for national mourning, not dissimilar to the aftermath of the assassination of John F. Kennedy, Martin Luther King, Jr., Robert Kennedy, and others. We were all in pain, we all grieved. But today, let’s look back upon the space program and the brave men and women who participated both as astronauts and in the ground crew. We take our “hats” off and thank them for their bravery and willingness to serve on the forefront of our country’s quest of space.

Challenger_flight_51l_crew

In recent history we have witnessed first-hand the explosion shortly after clearing the launch pad of the Space Shuttle Challenger in 1986. This event sent shutters through our bodies in a fashion similar to that that most of us did as we watched Neil Armstrong take those first steps on the moon in 1969. But this time, the reaction was not from the joyful sharing of an event of great import for all mankind, it came from the realization that the entire Challenger crew perished in the explosion. In just a few seconds, we saw the lift-off of the shuttle from the launch pad followed by a puff of white smoke that could be seen when the shuttle broke apart, with different large chunks going in different directions.

At the time, I was working for a school district and witnessed the event “real time,” not on video tape on the evening news. All educators were thrilled by the fact that one of our own, a high school teacher from New England, Christa McAuliffe, was travelling into space. She would be the first civilian to make such a voyage. She was prepared to carry out a number of educational experiments during her time in space and was being followed by schools across the country. But the voice of the TV commentator soon informed us that something terrible had happened a few seconds after launch from Cape Canaveral, Florida.

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Then we witnessed the debris from the shuttle fall from the sky. With that debris were the bodies of the seven shuttle astronauts. There was no escape. This incident resulted in a suspension of future shuttle flights until the cause of the accident had been determined and remedied. And it turned out that the cause was due to the failure of an O-Ring that cost just a few dollars. After this tragedy, both the equipment checks before launch and the launch procedures themselves were changed. A major cause of the O-Ring failure was the launch in the early morning hours in freezing weather. Ice had been an ever-present hazard to all launches from Cape Canaveral over the years; each crew breathed a sigh of relief when their vehicle had cleared the launch tower. Procedures were instituted that prevented launch until ice would no longer be a hazard.

We now will proceed to examine this event in history in more detail... GLB

These Introductory Comments are copyrighted:
Copyright©2012 — Gerald Boerner — All Rights Reserved

[ 3472 Words ]
    

    

Quotations Related to (Space) Shuttle:

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“I can remember in early elementary school when the Russians launched the first satellite. There was still so much unknown about space. People thought Mars was probably populated.”
— Christa McAuliffe

“Be strong and courageous. Do not be terrified. Do not be discouraged for the Lord your God will be with you wherever you go.”
— Rick Husband

“When you look at the stars and the galaxy, you feel you are not just from any particular piece of land, but from the solar system.”
— Laurel Clark

“Ever since I was a little kid, I’ve known this was what I wanted to do. I was probably 4 or 5 years old.”
— Michael Anderson

“I’m looking forward to the flight, of course. After you go to space once, you sort of get addicted. You want to have the same experience. Doing it again is like having a good dream once again.”
— Chawla

“It [space] was just so incredibly adventurous and exciting to me. I just thought there was no doubt in my mind that is what I want to do when I grow up.”
— Rick Husband

“I remember growing up and thinking astronauts and their jobs were the coolest things you could possibly do. But I absolutely couldn’t identify with people who were astronauts. I thought they were movie stars. I thought I was kind of a normal kid.”
— David Brown

“The colors are stunning. In a single view, I see – looking out at the edge of the earth: red at the horizon line, blending to orange and yellow, followed by a thin white line, then light blue, gradually turning to dark blue and various gradually darker shades of gray, then black and a million stars above. It’s breathtaking.”
— Pilot Willie McCool

    

In Memoriam: Challenger Space Shuttle Disaster…

    

    
Challenger_explosionThe Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida, United States, at 11:39 a.m. EST (16:39 UTC).

Disintegration of the entire vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB attachment hardware and external fuel tank. This led to the separation of the right-hand SRBs aft attachment and the structural failure of the external tank. Aerodynamic forces promptly broke up the orbiter.

The crew compartment and many other vehicle fragments were eventually recovered from the ocean floor after a lengthy search and recovery operation. Although the exact timing of the death of the crew is unknown, several crew members are known to have survived the initial breakup of the spacecraft. However, the shuttle had no escape system and the astronauts did not survive the impact of the crew compartment with the ocean surface.

The disaster resulted in a 32-month hiatus in the shuttle program and the formation of the Rogers Commission, a special commission appointed by United States President Ronald Reagan to investigate the accident. The Rogers Commission found that NASA’s organizational culture and decision-making processes had been a key contributing factor to the accident. NASA managers had known that contractor Morton Thiokol’s design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but they failed to address it properly. They also disregarded warnings from engineers about the dangers of launching posed by the cold temperatures of that morning and had failed to adequately report these technical concerns to their superiors. The Rogers Commission offered NASA nine recommendations that were to be implemented before shuttle flights resumed.
    

    

The Launch

    

Christa_McAuliffeMany viewed the launch live due to the presence on the crew of Christa McAuliffe, the first member of the Teacher in Space Project. Media coverage of the accident was extensive: one study reported that 85 percent of Americans surveyed had heard the news within an hour of the accident. The Challenger disaster has been used as a case study in many discussions of engineering safety and workplace ethics and inspired the 1990 television movie, Challenger.

    
Pre-Launch Conditions and Delays

Challenger was originally set to launch from Kennedy Space Center in Florida at 2:42 p.m. Eastern Standard Time (EST) on January 22. However, delays suffered by the previous mission, STS-61-C, caused the launch date to be pushed back to January 23 and then to January 24. Launch was then rescheduled to January 25 due to bad weather at the Transoceanic Abort Landing (TAL) site in Dakar, Senegal. NASA decided to use Casablanca as the TAL site, but because it was not equipped for night landings, the launch had to be moved to the morning (Florida time). Predictions of unacceptable weather at Kennedy Space Center (KSC) caused the launch to be rescheduled for 9:37 a.m. EST on January 27. According to Malcolm McConnell’s book, Challenger: A Major Malfunction, NASA normally would have launched with the predicted forecast of a 50 percent chance of rain if not for plans to have Vice President George H. W. Bush stop over and watch the launch on his way to Honduras.

Ice_on_the_Pad_on_the_Day_of_STS51Ls_Launch__GPN200400011 The launch was delayed the next day by problems with the exterior access hatch. First, one of the microswitch indicators used to verify that the hatch was safely locked malfunctioned. Then, a stripped bolt prevented the closeout crew from removing a closing fixture from the orbiter’s hatch. When the fixture was finally sawn off, crosswinds at the Shuttle Landing Facility exceeded the limits for a Return to Launch Site (RTLS) abort. The crew waited for the winds to die down until the launch window finally ran out, forcing yet another scrub.

Forecasts for January 28 predicted an unusually cold morning, with temperatures close to 31 °F (−1 °C), the minimum temperature permitted for launch. The low temperature had prompted concern from engineers at Morton Thiokol, the contractor responsible for the construction and maintenance of the shuttle’s SRBs. At a teleconference on the evening of January 27, Thiokol engineers and managers discussed the weather conditions with NASA managers from Kennedy Space Center and Marshall Space Flight Center. Several engineers—most notably Roger Boisjoly, who had voiced similar concerns previously—expressed their concern about the effect of the temperature on the resilience of the rubber O-rings that sealed the joints of the SRBs. Each SRB was constructed of six sections joined in three factory joints and three “field joints”.

The factory joints were welded, but the field joints—assembled in the Vehicle Assembly Building at Kennedy Space Center—each used two rubber O-rings, a primary and a secondary (backup), to seal them. (Since the accident, SRB field joints now use three O-rings.) The seals of all of the SRB joints were required to contain the hot high-pressure gases produced by the burning solid propellant inside, forcing it out the nozzle at the aft end of each rocket. Thiokol engineers argued that if the O-rings were colder than 53 °F (12 °C), they did not have enough data to determine whether the joint would seal properly. This was an important consideration, since the SRB O-rings had been designated as a “Criticality 1″ component—meaning that there was no backup if both the primary and secondary O-rings failed, and their failure would destroy the Orbiter and its crew.

    
Liftoff and initial ascent

The following account of the accident is derived from real time telemetry data and photographic analysis, as well as from transcripts of air-to-ground and mission control voice communications. All times are given in seconds after launch and correspond to the telemetry time-codes from the closest instrumented event to each described event.

STS51L_grey_smoke_on_SRB Gray smoke escaping from
the right side SRB
    

At 6.6 seconds before liftoff, as normal, the three space shuttle main engines (SSME) ignited. Until liftoff actually occurs, the SSMEs can be safely shut down and the launch aborted if necessary. At liftoff time (T=0, which was at 11:38:00.010 EST), the three SSMEs were at 100% of their original rated performance, and began throttling up to 104% under computer control. At this moment, the two SRBs were ignited and hold-down bolts were released with explosives, freeing the vehicle from the pad. With the first vertical motion of the vehicle, the gaseous hydrogen vent arm retracted from the External Tank (ET) but failed to latch back. Review of film shot by pad cameras showed that the arm did not re-contact the vehicle, and thus it was ruled out as a contributing factor in the accident. The post-launch inspection of the pad also revealed that kick springs on four of the hold-down bolts were missing, but they were similarly ruled out as a possible cause.

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To see a video of the Challenger Disaster,
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Later review of launch film showed that at T+0.678, strong puffs of dark gray smoke were emitted from the right-hand SRB near the aft strut that attaches the booster to the ET. The last smoke puff occurred at about T+2.733. The last view of smoke around the strut was at T+3.375. It was later determined that these smoke puffs were caused by the opening and closing of the aft field joint of the right-hand SRB. The booster’s casing had ballooned under the stress of ignition. As a result of this ballooning, the metal parts of the casing bent away from each other, opening a gap through which hot gases—above 5,000 °F (2,800 °C)—leaked. This occurred in previous launches, but each time the primary O-ring shifted out of its groove and formed a seal. Although the SRB was not designed to function this way, it appeared to work well enough and Morton-Thiokol changed the design specs to accommodate this process, known as extrusion.

Challenger_STS51Llaunch Unfortunately, while extrusion was taking place, hot gases would leak past, a process called blow-by, damaging the O-rings until a seal was made. Investigations into the matter by Morton-Thiokol engineers determined that the amount of damage to the O-rings was directly related to the time it took for extrusion to occur, and that cold weather, by causing the O-rings to harden, lengthened the time of extrusion. (The redesigned SRB field joint used subsequent to the Challenger accident uses an additional interlocking mortise and tang with a third O-ring, mitigating blow-by.)

On the morning of the disaster, the primary O-ring had become so hard due to the cold that it couldn’t seal in time. The secondary O-ring was not in its seated position due to the metal bending. There was now no barrier to the gases, and both O-rings were vaporized across 70 degrees of arc. However, aluminum oxides from the burned solid propellant sealed the damaged joint, temporarily replacing the O-ring seal before actual flame rushed through the joint.

As the vehicle cleared the tower, the SSMEs were operating at 104% of their rated maximum thrust, and control switched from the Launch Control Center (LCC) at Kennedy to the Mission Control Center (MCC) at Johnson Space Center in Houston, Texas. To prevent aerodynamic forces from structurally overloading the orbiter, at T+28 the SSMEs began throttling down to limit the velocity of the shuttle in the dense lower atmosphere, as per normal operating procedure. At T+35.379, the SSMEs throttled back further to the planned 65%. Five seconds later, at about 19,000 feet (5800 m), Challenger passed through Mach 1. At T+51.860, the SSMEs began throttling back up to 104% as the vehicle passed beyond Max Q, the period of maximum aerodynamic pressure on the vehicle.

    
Cause and Time of Death

On July 28, 1986, Rear Admiral Richard H. Truly, NASA’s Associate Administrator for Space Flight and a former astronaut, released a report from Joseph P. Kerwin, biomedical specialist from the Johnson Space Center in Houston, relating to the deaths of the astronauts in the accident. Dr. Kerwin, a veteran of the Skylab 2 mission, had been commissioned to undertake the study soon after the accident. According to the Kerwin Report:

The findings are inconclusive. The impact of the crew compartment with the ocean surface was so violent that evidence of damage occurring in the seconds which followed the disintegration was masked. Our final conclusions are:

  • the cause of death of the Challenger astronauts cannot be positively determined;

  • the forces to which the crew were exposed during Orbiter breakup were probably not sufficient to cause death or serious injury; and

  • the crew possibly, but not certainly, lost consciousness in the seconds following Orbiter breakup due to in-flight loss of crew module pressure.

Despite the report, some experts, including one of NASA’s lead investigators Robert Overmyer, believed most if not all of the crew were alive and possibly conscious during the entire descent until impact with the ocean.

    
Crew escape was not possible

STS51L_riadiace_stredisko During powered flight of the space shuttle, crew escape was not possible. While launch escape systems were considered several times during shuttle development, NASA’s conclusion was that the shuttle’s expected high reliability would preclude the need for one. Modified SR-71 Blackbird ejection seats and full pressure suits were used on the first four shuttle orbital missions, which were considered test flights, but they were removed for the “operational” missions that followed. (The CAIB later declared, after the Columbia descent disaster, that the space shuttle system should never have been declared operational because it is experimental by nature due to the limited number of flights as compared to certified commercial aircraft.) Providing a launch escape system for larger crews was considered undesirable due to “limited utility, technical complexity and excessive cost in dollars, weight or schedule delays.”

After the loss of Challenger the question was re-opened, and NASA considered several different options, including ejector seats, tractor rockets and bailing out through the bottom of the orbiter. However, NASA once again concluded that all of the launch escape systems considered would be impractical due to the sweeping vehicle modifications that would have been necessary and the resultant limitations on crew size. A bail-out system was designed to give the crew the option to leave the shuttle during gliding flight; however, this system would not have been usable in the Challenger scenario.

    

The Aftermath

    

Reagan_Challenger U.S. President Ronald Reagan’s Oval Office
address after the shuttle disaster.
    

In the aftermath of the disaster, NASA was criticized for its lack of openness with the press. The New York Times noted on the day after the disaster that “neither Jay Greene, flight director for the ascent, nor any other person in the control room, was made available to the press by the space agency.” In the absence of reliable sources, the press turned to speculation; both The New York Times and United Press International ran stories suggesting that a fault with the external tank had caused an explosion, despite the fact that NASA’s internal investigation had quickly focused in on the solid rocket boosters. “The space agency,” wrote space news reporter William Harwood, “stuck to its policy of strict secrecy about the details of the investigation, an uncharacteristic stance for an agency that long prided itself on openness.”

    

Tributes

    

On the night of the disaster, President Ronald Reagan had been scheduled to give his annual State of the Union Address. He initially announced that the address would go on as scheduled, but then postponed the State of the Union Address for a week and instead gave a national address on the Challenger disaster from the Oval Office of the White House. It was written by Peggy Noonan, and finished with the following statement, which quoted from the poem “High Flight” by John Gillespie Magee, Jr.:

“We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and ‘slipped the surly bonds of Earth’ to ‘touch the face of God.’

Three days later, President Reagan with his wife Nancy traveled to the Johnson Space Center to speak at a memorial service honoring the astronauts where he stated

“Sometimes, when we reach for the stars, we fall short. But we must pick ourselves up again and press on despite the pain.”

It was attended by 6,000 NASA employees and 4,000 guests, as well as by the families of the crew. During the ceremony, an Air Force band led the singing of “God Bless America” as NASA T-38 Talon jets flew directly over the scene, in the traditional missing-man formation. All activities were broadcast live by the national television networks.

The families of the Challenger crew organized the Challenger Center for Space Science Education as a permanent memorial to the crew. Fifty-two learning centers have been established by this non-profit organization.

    

    

Space shuttle Challenger explosion CBS Evening News…  (10:32)

    

    

Please take time to further explore more about Dick Scobee, Michael J. Smith, Judith A. Resnik, Ronald E. McNair, Ellison S. Onizuka, Gregory B. Jarvis, Christa McAuliffe, Cape Canaveral, Space Shuttle, Challenger, Challenger disaster, O-Ring Seal, and Solid Rocket Boosters by accessing the Wikipedia articles referenced below…

    

    

References

    

Background information is from Wikipedia articles on:

Wikipedia: Challenger Disaster
http://en.wikipedia.org/wiki/Challenger_disaster

Wikipedia: Christa McAuliffe (1st Civilian in Space)
http://en.wikipedia.org/wiki/Christa_McAuliffe

Brainy Quote: Challenger Quotes…
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Prof. Boerner’s Explorations: Space Shuttle Challenger Disaster…
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Prof. Boerner’s Explorations: Columbia Disaster: Shuttle Disintegrates…
http://www.boerner.net/jboerner/?p=16773

Prof. Boerner’s Explorations: John Glenn: First American in Earth Orbit…
http://www.boerner.net/jboerner/?p=8712

Prof. Boerner’s Explorations: John Glenn: Always an Astronaut…
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