ProQuest www.csa.com
 
 
RefWorks
  
Discovery Guides Areas
>
>
>
>
>
 
  
e-Journal

EEVL

 

Columbia Shuttle Tragedy
(Released October 2003)

 
  by Yng-Ru Chen  

Review

Key Citations

Web Sites

Glossary

Conferences

Editor
 
Review Article
February 1st, 2003 was a clear sunny day, the perfect day for the Columbia shuttle to return to earth. Everyone at NASA was excited because the shuttle would bring back many important research results from its 16-day mission. No one suspected anything unusual.

When the shuttle lost contact with NASA at approximately 9:00 AM, the mission controllers thought it was a temporary problem caused by reentry into the atmosphere, even though temperature sensors on the inboard and outboard elevons on the left wing had stopped functioning minutes before. When the silence continued, the fear rose. Several 911 calls were made by residents in Texas, Arkansas and the Louisiana area. The worst nightmare had happened. The space shuttle Columbia and her seven crewmembers were lost!
Columbia reentry timeline
http://www.cnn.com/interactive/aol/popup.shuttle.route/frameset.exclude.html

Immediately after losing the shuttle and its seven crew members, NASA began impounding all mission control data on the flight, and also stopped all shuttle operations at Kennedy Space Center. NASA authorities asked the public not to touch the debris and to report any findings to the police. The condition and location of the debris would help the engineers to determine what caused the shuttle to break up.

The engineers try to reconstruct the shuttle
KSC-03PD-0430: http://mediaarchive.ksc.nasa.gov/

The biggest concern was with what had happened during the launch on January 16th. A day after, NASA engineers reviewed the launch tapes to reveal a 20-inch piece of hardened insulation foam breaking off the main fuel tank and hitting the shuttle's left wing.

The foam from the fuel tank hit the left wing of the shuttle
KSC-03PD-0250: http://mediaarchive.ksc.nasa.gov/

The engineers could not determine if the foam had caused any damage to the shuttle's wing because the picture was blurry and the angle of the shot was bad. They asked the top shuttle managers for outside agency assistance, but the request was denied. After an official report from Boeing and many consultations, the shuttle managers concluded that there was no safety concern due to the foam's impact and the shuttle continued its mission.

When the shuttle broke up during reentry, no one could ascertain if it was because of the damaged wing hit by the foam. Other possible causes were pilot mistake and space debris. Investigations continued in the next few weeks. Some molten aluminum debris from the shuttle's wing structure, as well as molten steel debris, had been found. The engineers eliminated the other possibilities and began focusing on the foam from the external tank only.

When the shuttle reenters the earth, the temperature on its surface can reach nearly 3000o F. So the Thermal Protection System (TPS) on the shuttle is critical. This system uses four different materials: high-temperature reusable surface insulation (HRSI), low-temperature reusable surface insulation (LRSI), felt reusable surface insulation (FRSI), and reinforced carbon-carbon composite (RCC). The black HRSI tiles cover the areas where the high surface temperature is between 1,200 and 2,300 degrees Fahrenheit. The white LRSI tiles cover the lower temperature areas where the maximum surface temperature reaches between 700 and 1,200 degrees Fahrenheit. The felt reusable surface insulation and the reinforced carbon-carbon are used in small amounts. The felt reusable surface insulation was developed later in the thermal protection system program to replace some of the HRSI tiles in the selected areas.

Space shuttles thermal protection system (TPS)
http://www.centennialofflight.gov/essay/Evolution_of_Technology/TPS/Tech41G2.htm

Because the temperature during reentry exceeds 2,300o Fahrenheit at the nose cap, the chin panel, forward external tank attachment point, and wing leading edge panels and T-seals, the reinforced Carbon-Carbon panels were used in these areas. The RCC composite is a laminate of graphitized rayon cloth impregnated with a phenolic resin and layered, one ply at a time, then cured. Next, the laminate is pyrolized to convert the resin to carbon. The part is then impregnated with furfural alcohol in a furnace to convert it to carbon. The process is repeated three times until the desired carbon-carbon properties are reached. For reuse purpose and to prevent oxidation, the outer layer of the RCC is converted into silicon carbide in a furnace filled with argon with a temperature cycle up to 3,000o Fahrenheit.

During the January 16th launch, the foam from the bipod of the external tank was shed, and struck the shuttle's left wing. The debris had damaged the wing's leading edge reinforced carbon-carbon (RCC) structures and excavated tiles, allowing reentry plasma to penetrate and disintegrate the underlying aluminum, damaging the wing's structure.

The bipod on the shuttle model The wing of the shuttle
http://www.caib.us/photos/sub_section.asp?category=&main=materials_testing&sub=models&item=&thumbnails=yes

Foam of the bipod ramp
http://www.caib.us/photos/sub_section.asp?category=&main=materials_testing&sub=et94_dissection&item=&thumbnails=yes

The foam of the bipod ramp is BX-250, polyurethane foam applied with CFC-11 chlorofluorocarbon. It is applied by hand to cover outside of the tank fittings to prevent ice and frost from forming on the surface. The foam also helps protect from engine and aerodynamic heating. The foam is made of light material to reduce the weight. The wing of the shuttle is covered with a tough carbon panel. It was hard to imagine how such a light material could damage the wing of the shuttle. Some tests were run at the Southwest Research Institute. A piece of foam fired from an air gun at about 500 mph punched a hole in the reinforced carbon material. In other tests with different firing speeds from the air gun, the foam also caused visible cracks on the tested RCC panels. And these cracks could lead to shuttle breakup during re-entry.


Before the Impact After the impact
http://www.caib.us/photos/sub_section.asp?category=&main=materials_testing&sub=impact_test_20030707&item=&thumbnails=yes

Foam ejection during launch has been a problem with quite a long history. Four previous shuttle launches had foam falling from the bipod area: Challenger in 1983, Columbia in 1990 and 1992, and Atlantis last October. Engineers had made many changes in the foam design in the past few years, but the problem had not been solved. The debris of Columbia's left wing leading edge was found heavily eroded from the extreme heat. Erosion was not detected on the debris from the other parts of the wings, clearly proving that the shuttle disintegrated because of the damaged left wing.

The final report of the Columbia Accident Investigation was released on August 26th, 2003. It concluded that this tragedy was caused by technical and organizational failures. The foam problem of the bipod area has existed for years, and NASA engineers have looked at a variety of ways to correct it. The report indicated that the space shuttle should not have been launched with this problem extant. The report further proposed that, although the shuttle had always returned to earth safely after the foam hit the wing during previous shuttle flights, the managers at NASA should not have rejected the engineers' requests to make sure Columbia's wing was not damaged this time. Finally, it suggested that NASA should have had a backup plan for fixing the shuttle in space and insuring the crew's safety if they found out the wing was badly damaged .

The first space shuttle was Columbia, and the first ever shuttle mission took place on April 12, 1981. More recently, because NASA's budget has been cut, along with its workforce, it has been hard for NASA to solve unexpected problems or to improve the shuttle. Despite Columbia's age, plans to replace it were moved from 2006 to 2015 or later because of the budget. Now NASA has decided that they are not building any new space shuttles with the current design. But before the new shuttle is available, the maintenance of the current shuttle is still the priority. The Columbia Accident Investigation Board (CAIB) gave 29 recommendations, 23 technical and 6 organizational, 15 of which the Board specified must be completed before the shuttle returns to flight status. NASA plans to have the next shuttle flight in 2004, no earlier than September 12, 2004.

With the Columbia accident, not only has the nation lost a four-billion-dollar shuttle, seven outstanding astronauts and priceless experimental results, it has also lost confidence in manned space flight and space exploration. It remains to be seen whether internal problems at NASA can be solved, and we can return to an era of pride and confidence in our space program.

 

© Copyright 2003, All Rights Reserved, C SA