ENDNOTES FOR CHAPTER 3

¶The citations that contain a reference to "CAIB document" with CAB or

¶CTF followed by seven to eleven digits, such as CAB001-0010, refer to a document in the Columbia Accident Investigation Board database maintained by the Department of Justice and archived at the National Archives.

¶See Dennis R. Jenkins, Space Shuttle: The History of the National Space

¶Transportation System – The First 100 Missions (Cape Canaveral, FL,

¶Specialty Press, 2001), pp. 421-424 for a complete description of the

¶External Tank.²² Guidelines per NASA Policy Guideline 8621.

¶Scotty Sparks and Lee Foster, "ET Cryoinsulation," CAIB Public Hearing,

¶April 7, 2003. CAIB document CAB017-03140371.³³ 5 U.S.C. App § §1 et seq. (1972).

¶Scotty Sparks and Steve Holmes, Presentation to the CAIB, March 27,

¶2003, CAIB document CTF036-02000200.

¶See the CAIB/NAIT Joint Working Scenario in Appendix D.7 of Volume

¶II of this report.⁵⁵ Harold W. Gehman to Sean OʼKeefe, February 25, 2003. 238 Report Volume I August 2003

¶Boeing Specification MJ070-0001-1E, "Orbiter End Item Specification for the Space Shuttle Systems, Part 1, Performance and Design Requirements,

¶November 7, 2002.⁶⁶ Quoted in Jenkins, Space Shuttle, p. 171. Press, 1996). 7 18 Memorandum from J. Fletcher to J. Rose, Special Assistant to the See John M. Logsdon, "Return to Flight: Richard H. Truly and the President, November 22, 1971; Logsdon, John, "The Space Shuttle Recovery from the Challenger Accident," in Pamela E. Mack, editor, Program: A Policy Failure?" Science, May 30, 1986, Volume 232, pp. From Engineering to Big Science: The NACA and NASA Collier Trophy 1099-1105. Research Project Winners, NASA SP-4219 (Washington: GovernmentShow full note

¶Ibid., Paragraph 3.3.1.8.16.

¶NSTS-08171, "Operations and Maintenance Requirements and

¶Specifications Document (OMRSD)" File II, Volume 3. CAIB document

¶CAB033-12821997.⁸⁸ The only actual flight tests conducted of the Orbiter were a series of Printing Office, 1998) for an account of the aftermath of the accident. Approach and Landing Tests where Enterprise (OV-101) was dropped Much of the account in this section is drawn from this source. from its Boeing 747 Shuttle Carrier Aircraft while flying at 25,000 feet. 19 Logsdon, "Return to Flight," p. 348. These tests – with crews aboard – demonstrated the low-speed handling 20 Presidential Commission on the Space Shuttle Challenger Accident capabilities of the Orbiter and allowed an evaluation of the vehicleʼs (Washington: Government Printing Office, June 6, 1986). landing characteristics. See Jenkins, Space Shuttle, pp. 205-212 for more information. 26 Report Volume I August 2003Show full note

¶Dr. Gregory J. Byrne and Dr. Cynthia A. Evans, "STS-107 Image Analysis

¶Team Final Report in Support of the Columbia Accident Investigation,"

¶NSTS-37384, June 2003. CAIB document CTF076-15511657. See

¶Appendix E.2 for a copy of the report.

¶This section based on information from the following reports: MIT Lincoln

¶Laboratory "Report on Flight Day 2 Object Analysis;" Dr. Brian M. Kent, Dr. Kueichien C. Hill, and Captain John Gulick, "An Assessment of Potential Material Candidates for the ʻFlight Day 2ʼ Radar Object

¶Observed During the NASA Mission STS-107 (Columbia)", Air Force

¶Research Laboratory Final Summary Report AFRL-SNS-2003-001, July

¶20, 2003 (see Appendix E.2); Multiple briefings to the CAIB from Dr. Brian M. Kent, AFRL/SN (CAIB document CTF076-19782017); Briefing to the CAIB from HQ AFSPC/XPY, April 18, 2003 (CAIB document

¶CAB066-13771388).

¶The water tanks from below the mid-deck floor, along with both Forward

¶Reaction Control System propellant tanks were recovered in good condition.

¶Enterprise was used for the initial Approach and Landing Tests and ground tests of the Orbiter, but was never used for orbital tests. The vehicle is now held by the National Air and Space Museum. See Jenkins,

¶Space Shuttle, pp. 205-223, for more information on Enterprise.

¶Philip Kopfinger and Wanda Sigur, "Impact Test Results of BX-250 In

¶Support of the Columbia Accident Investigation," ETTP-MS-03-021, July

¶17, 2003.

¶Details of the test instrumentation are in Appendix D.12.

¶Evaluations of the adjustments in the angle of incidence to account for rotation are in Appendix D.12. 16

¶The potential damage estimates had great uncertainty because the database of bending, tension, crushing, and other measures of failure were incomplete, particularly for RCC material.

Chapter 4: Other Factors Considered

¶During its investigation, the Board evaluated every known factor that could have caused or contributed to the Columbia accident, such as the effects of space weather on the Orbiter during re-entry and the specters of sabotage and terrorism. In addition to the analysis/scenario investigations, the Board oversaw a NASA "fault tree" investigation, which accounts for every chain of events that could possibly cause a system to fail. Most of these factors were conclusively eliminated as having nothing to do with the accident; however, several factors have yet to be ruled out. Although deemed by the Board as unlikely to have contributed to the accident, these are still open and are being investigated further by NASA. In a few other cases, there is insufficient evidence to completely eliminate a factor, though most evidence indicates that it did not play a role in the accident. In the course of investigating these factors, the Board identified several serious problems that were not part of the accidentʼs causal chain but nonetheless have major implications for future missions.

¶In this chapter, a discussion of these potential causal and contributing factors is divided into two sections. The first introduces the primary tool used to assess potential causes of the breakup: the fault tree. The second addresses fault tree items and particularly notable factors that raised concerns for this investigation and, more broadly, for the future operation of the Space Shuttle.