LIST OF VOLUMES (seperately bound)

VOLUME 1	REPORT SUMMARIES
VOLUME 2	Enclosure 1. MISSION 51-L SHUTTLE MISHAP-SURFACE SEARCH Enclosure 2. RADAR DATA ANALYSIS AND IMPACT ESTIMATION FOR STS 51-L DEBRIS . Enclosure 3. STS 51-L RIGHT SRB REPORT NO. 82-SR-86-07, Enclosure 4. SEARCH, CLASSIFICATION AND RECOVERY
VOLUME 3	Enclosure 5. SRB INCREMENTAL RECOVERY PLANNING
VOLUME 4	THIS VOLUME Enclosure 6. RECOVERED ET DEBRIS HARDWARE ASSESSMENT, Enclosure 7. OCEANOGRAPHY Enclosure 8. SPACE TRANSPORTATION SYSTEM, MISSION 51-L STRUCTURAL RECONSTRUCTION AND EVALUATION REPORT (Standard Accident Report) Enclosure 9. CONTACT #131 AND #712 RECOVERED RH SRB AFT FIELD JOINT EVALUATION

John W. Beaton

Martin Marietta Corporation

Launch Support Services

Alexander McCool

Director, Structures and Propulsion Laboratory

NASA, Marshall Space Flight Center

ENCLOSURE 6

A. Introduction.

B. Recovered Hardware Review.

1. Interface Hardware.

2. Press Lines, Cable Trays, and Other External Hardware.

3. LO₂ Feedline.

4 LO₂ Tank.

5. LH₂ Tank Skin.

6. Intertank Skin Panels.

7. ET/SRB Cross Beam.

8. TPS Foam/SLA Debris.

C. Recovered Hardware Assessments.

1. Fractographic Analysis.

2. LO₂ Tank Hardware.

3. Intertank Hardware.

4. LH₂ Tank Hardware.

5. LO₂ Feedline.

6. LO₂ Feedline Fairing.

7. Aft GH₂ Pressline Fairing.

8. Miscellaneous Cable Tray Parts.

D. Conclusion .

E. Attachments.

TABLES AND FIGURES

Table 1. Recovered Debris Matrix.

Figure 1. External Tank Map.

Figure 2. Liquid Oxygen (LO₂) Tank Map.

Figure 3. Intertank Map.

Figure 4. Liquid Hydrogen (LH₂) Tank Map.

[O363] RECOVERED ET DEBRIS HARDWARE ASSESSMENT

A. INTRODUCTION.

To date, approximately 200 pieces of Light Weight Tank (LWT-19 (51 L)) have been recovered. Approximately 100 of these pieces are foam/Thermal Protection System (TPS) items. The remaining hardware consists of portions of the Liquid Hydrogen (LH₂), Liquid Oxygen (LO₂), and intertank skin panels. Other recovered debris includes cable trays, fairings, ordnance, and the External Tank (ET)/Orbiter LO₂ disconnect.

The majority of the debris, which was recovered within the first 10 days after the accident, was found floating on the Atlantic Ocean.

All recovered debris is photographed when received at KSC and assigned and tagged with a log number for traceability. The numbers shown on the "maps" and matrix included with this report are the assigned log numbers.

After receipt of the debris, exposed metallic surfaces were rinsed with fresh water and all fracture surfaces were brushed with nylon brushes and sprayed with WD-40 to prevent corrosion.

Any work performed on hardware was documented and photographed before, during, and after execution. Any photographs that are needed can be obtained through the Kennedy Space Center (KSC) Task Force and must be requested by debris log number.

B. RECOVERED HARDWARE REVIEW.

1. Interface Hardware.

The only piece of interface hardware recovered was the ET/Orbiter LO₂ disconnect. Both the ET and the Orbiter halves were recovered still mated by the pyro separation bolts.

No ET/Solid Rocket Booster (SRB) interface/attachment hardware has been recovered.

2. Press Lines, Cable Trays, and Other External Hardware.

The three sections of LH₂ cable tray and forward section (3 ft.) of the LO₂ containing the linear-shaped charge/confined detonating fuse (LSC/CDF) were recovered floating. Both the LO₂ and LH₂ LSC/CDF were fractured but not detonated.

Other external hardware recovered includes:

Nose Cone Fairing

- y Vert Strut Cable Tray

GO₂ Press Line Mount at X_T752

Portion of LO₂ Umbilical Cable Tray

+y Vert Strut Transition Cable Tray

+y ET/SRB Bolt Catcher

GO₂ Press Line Guide Rail

GH₂ Press Line Fairing from Cross Beam

3. LO₂ Feedline.

Three sections of LO₂ Feedline were recovered, one section approximately 3 ft. long with the mating flanges from Station (STA) X_T 1372 and two sections of aluminum line approximately 10 feet long, that cannot be precisely located on the longitudinal axis.

4. LO₂ Tank.

Six pieces of LO₂ tank were recovered. One item's location has been determined in the original configuration. None of the five remaining pieces can be precisely located, but four are believed to be parts of the forward LO₂ ogive section and one is believed to be from the aft dome. Six pieces of the LO₂ slosh baffles were recovered but they also cannot be precisely located in the original configuration.

5. LH₂ Tank Skin.

Six pieces of LH₂ tank skin were recovered; four were floating on the ocean and two were salvaged from the ocean bottom. Item 1543 was originally thought to be from the +y (right-hand) side near the ET/SRB strut and had a hole that appeared to be a burn through when viewed in the underwater films. After recovery, positive identification showed it to be located near - y (left-hand) from STA X_T1871-2000, and the hole, which was approximately 2 inches by 4 inches, occurred when part of the 1871 "T" ring tore loose, therefore, it was not a burn through.

Item #0064 is the piece of structure where a weld imperfection was detected at the - z longitudinal weld at the junction of the upper 2058 ring weld. X-rays were done of the suspect area on the debris at KSC and compared with the build x-rays at Michoud. Analysis of these x-rays showed no propagation of the imperfection and fracture analysis determined this area was not a start of ET break-up nor a contributing factor of the accident. A more detailed explanation is contained in the fractographic analysis section.

All recovered LH₂ debris shows mild surface scorching of the TPS foam but there is no evidence of severe heat that melted or burned through any tank structure. At this time, no parts of the ET from the areas of the right- or left-hand ET/SRB aft attach points have been located or recovered.

There have been five pieces of LH₂ tank internal intermediate ring frames recovered that can be identified as to location on the longitudinal axis but not the circumferential axis.

6. Intertank Skin Panels.

Fifty-three pieces of intertank were recovered as floating debris. Forty-one pieces have been precisely located on the original configuration. Of the remaining 12 pieces, ten are portions of individual stringers that have been separated from the skin and range in length from 2 inches to 2 feet. The remaining two skin panels are less than 36 square inches and too small to precisely locate.

The external TPS surface of the recovered panels shows evidence of heating and varied degrees of charring that range from no evidence of heat to several pieces that are heavily charred. There is no discernible pattern to the burning. Pieces that are heavily charred match to pieces that show no evidence of any heat. This indicates that the parts were in high heat environments after break-up. Visual observation of all interior intertank surfaces show no indication of any heat or fire damage, which indicates that no explosion or any fire originated from inside the intertank.

7. ET/SRB Cross Beam.

Five pieces of the ET/SRB cross beam webbing have been recovered to date. None of the major structural members of the beam have been found. The exact location of the recovered webbing cannot be determined. Pieces range from 36 square inches to 200 square inches.

8. TPS Foam/SLA Debris.

Approximately 100 pieces of foam insulation were recovered as floating debris. Positive location has been made on some of these, others have been identified as coming from the LO₂, LH₂, intertank, or PAL ramps, but exact location cannot be determined. This debris will not provide any evidence useful to the investigation.

[O364] C. RECOVERED HARDWARE ASSESSMENTS.

1. Fractographic Analysis.

All the major fracture faces were visually examined to determine fracture propagation direction, fracture origins, fracture mechanism (slow fracture vs. fast fracture), material imperfections, and any other topographical feature. In some areas, a 10x eyepiece was used to better examine the fracture features. Plastic replicas were made of the fracture face on Item 0064 at the HAG-7 ( - z at upper X_T2058 ring weld junction) weld, and the replicas were then examined with a scanning electron microscope (SEM).

2. LO₂ Tank Hardware.

The one significant piece of LO₂ hardware, Item 0065, that has been recovered to date, failed along the OAF weld (X_T852), ODG welds (285°, 345°), and along the second and third dome stiffening ring. All the fracture faces indicate a rapid fracture mode. A review of weld x-rays indicated no weld imperfections in this area.

3. Intertank Hardware.

Because of the large number of intertank pieces and secondary cracks, the visual examination concentrated on the major features. In general, the majority of fractures were in a shear mode (rapid fracture). Fractures at the aft end of the stringers near the LH₂ tank (X_T1123) are of a compression type indicating forward motion of the LH₂ tank. The two more interesting fractures were associated with the main intertank frame located at STA 985. On intertank Panel No. 311, the 985 frame section that is protruding past the piece itself is bent inboard. Considering the bulk of the frame, a considerable force would be required to bend the frame. Other than water impact, the only explanation would involve (slow) contact with the forward end of the SRB. This hypothesis appears more likely than water impact, based on the undistorted condition of the skin/stringers on panel 311. The Mating Panel, No. 0657, shows no external damage.

On the intertank Panel No. 0267, the piece of 985 frame still attached to the thrust panel indicated a slower (plain strain) type fracture. The lengthwise fracture of this same intertank panel also appeared to slow down near the 985 frame region. This may be expected because of the load carrying capability of the intertank in this area.

4. LH₂ Tank Hardware.

The fracture faces of the recovered LH2 tank hardware yielded the most interesting findings:

a. As mentioned elsewhere in this report, a 0.400-inch cracklike imperfection was discovered to be unreported. The location of the imperfection was along the HAG-7 weld intersection with the H1 weld (Upper 2058 Ring Frame). Considerable attention was given to the recovered hardware from this area.

b. The recovered - z barrel No. I hardware very likely contained the 0.400-inch imperfection. Following is the step-by-step methodology used to determine if the 0.400-inch imperfection was recovered, and if so, was there any flaw growth, and did the imperfection contribute to the overall fracture scenario.

(1) An x-ray overlay of the HAG-7 weld and its distinguishing features was made and it included the 0.400-inch indication. This overlay was taken to KSC and compared with the recovered weld's features and the path of the fracture. The result indicated that the STS 51-L fracture went through the 0.400-inch indication.

NOTE: It could not be determined from the original x-ray whether the imperfection was near the ISL (upper) or the OSL (lower).

(2) Next, the area of the 0.400-inch imperfection was visually examined at magnifications up to 10x. No preexisting defect was observed.

(3) A replica was then made of the fracture face areas indicated by the x-ray film overlay. The replica method consists of using an acetate film softened with acetone and pressing the film against the fracture face. The film dries in 5 to 10 minutes and is stripped away. The replica is placed in a vacuum chamber where a 200-angstrom layer of 60% gold /40% palladium is applied. The coated replica is then viewed with the scanning electron microscope (SEM).

(4) An extensive examination of the replica of the HAG-7 weld did not reveal a pre-existing flaw or indicate any slow or cyclic flaw growth (Striations).

(5) After the SEM work, the HAG-7 weld was radiographically inspected to locate the 0.400-inch imperfection with respect to the recovered fracture face. These new x-ray films reconfirmed that the 0.400-inch indication was on the recovered fracture face.

(6)Additional visual examination of the HAG-7 weld revealed a single gas pore approximately 2 inches aft of the 0.400-inch imperfection. Review of the original x-ray film indicated four very small (up to 0.050-inch diameter) pores in this area. The KSC x-ray films revealed that the fracture pore was most likely to be the 0.050-inch pore. Examination of the adjacent fracture topography suggests that the region of the pores was a secondary origin of the HAG-7 fracture itself. With a calculated critical flaw size of at least 5 inches, the porosity can only be considered a secondary effect.

(7) Except for the HAG-7 weld, no other longitudinal fractures occurred through a weld.

(8) Except for short transitional fractures, all circumferential fractures were along weld heat-affected zones or fusion lines.

(9) All circumferential weld fractures occurred on the extrusion side of the weld joint.

(10) Whereas the longitudinal parent metal fractures were shear type, the circumferential weld fractures characteristically had a "woody" type fracture topography. (This is likely a result of the typical layered microstructure of an extrusion. However, this item should be considered for further study.)

5. LO₂ Feedline.

With only an 0.800-inch thickness and physical wear to the fracture face, an exact analysis was difficult. However, the fracture features indicated a rapid fracture. An interesting observation of the feedline TPS was the number of imbedded Orbiter particles, including pieces of mylar, gold, and pieces of graphite/epoxy composite.

6. LO₂ Feedline Fairing.

The fairing apparently was torn from the intertank. Examination of the interior of the fairing suggested a strong upward force/impact from the feedline itself. All fracture features indicated a rapid fracture.

7. Aft GH₂ Pressline Fairing.

This fairing also failed by overload in a rapid manner.

8. Miscellaneous Cable Tray Parts

All fracture features indicated a rapid fracture.

D. CONCLUSION.

Analysis of the recovered ET hardware provided no evidence to indicate that an ET imperfection contributed to the STS 51-L accident.

E. ATTACHMENTS.

A matrix (Table 1) has been included showing whether debris floated, degrees of charring, or other pertinent information.

Four"maps" (Figures 1 through 4) have been included as part of this report to show the exact location on the ET of all the debris that was recovered and positively identified.

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[O365]

 

Table 1. Recovered Debris Matrix.

 

Debris Item #	Floating	Sunken	General Location	Degree of Heat Charring				Pos ID	Remarks
				None	Light	Med	Heavy
.
0002	X	.	I/T	X	.	.	.	X	.
0005	X	.	I/T	X	.	.	.	X	.
0007	X	.	I/T	.	.	X	.	X	.
0008	X	.	LO2 Fairing	X	.	.	.	X	.
0059	X	.	+Y Bipod MA25 SLA	X	.	.	.	X	.
0060	X	.	I/T	.	X	.	.	.	Small Stringer Fragment
0061	X	.	I/T Foam	.	.	.	.	.	Multiple TPS Fragments
0062	X	.	LO2 TPS	.	.	.	.	.	Multiple TPS Fragments
0064	X	.	LH2	.	X	.	.	X	Weld Imperfection
0065	X	.	LH2	.	.	.	.	X	.
0066	X	.	I/T	X	X	.	.	X	.
0067	X	.	I/T	.	.	.	.	X	.
0069	X	.	BX 250	.	.	.	.	.	Multiple TPS Fragments
0070	X	.	I/T	.	.	.	.	.	Stringer Fragment
0071	X	.	I/T	.	.	.	X	X	.
0072	X	.	I/T	.	.	X	.	X	.
0073	X	.	I/T	X	.	.	.	X	.
0074	X	.	I/T	X	.	.	.	X	.
0075	X	.	I/T	.	.	.	X	X	.
0076	X	.	I/T	.	X	.	.	X	.
0077	X	.	I/T	.	.	X	.	X	.
0078	X	.	I/T	X	.	.	.	X	.
0079	X	.	I/T	.	X	.	.	X	.
0080	X	.	LO2 TPS	.	.	.	.	.	Multiple TPS Fragments

 

 

Table 1. Recovered Debris Matrix- Continued

 

 

Debris Item #	Floating	Sunken	General Location	Degree of Heat Charring				Pos ID	Remarks
				None	Light	Med	Heavy
.
0081	X	.	I/T	.	.	X	.	X	.
0082	X	.	LO2 F/L	X	.	.	.	X	.
0083	X	.	LH2	.	X	.	.	X	.
0084	X	.	LO2 F/L	.	.	X	.	.	Multiple Imbedded Possible ORB Fragments
0085	X	.	I/T	.	X	.	.	X	.
0086	X	.	GH2 PL Fairing	.	.	X	.	X	.
0087	X	.	I/T	.	X	.	.	X	.
0092	X	.	LH2 C/T	X	.	.	.	X	.
0120	X	.	I/T	.	.	.	X	X	.
0196	X	.	I/T	.	X	.	.	.	Stringer Fragment
0197	X	.	P/L Mount	X	.	.	.	X	.
0230	X	.	C/T Assy	X	.	.	.	X	LH2 C/T Fragment ID Possible
0231	X	.	GO2 P/L BKT	X	.	.	.	X	.
0232	X	.	LO2 TPS	.	X	.	.	X	Multiple Fragments
0233	X	.	AT C/T	X	.	.	.	X	.
0234	.	.	LO2 TPS	.	X	.	.	.	Multiple Fragments
0263	X	.	I/T	X	.	.	.	X	.
0264	X	.	I/T	.	X	.	.	X	.
0265	X	.	I/T	.	.	.	X	X	.
0266	X	.	LH2	.	.	X	.	X	.
0267	X	.	I/T	X	.	.	.	X	.
0268	X	.	-Y Vert Strut C/T	X	.	.	.	X	.
0269	X	.	+Y Vert Strut C/T	X	.	.	.	X	.

 

[O366] Table 1. Recovered Debris Matrix- Continued

 

Debris Item #	Floating	Sunken	General Location	Degree of Heat Charring				Pos ID	Remarks
				None	Light	Med	Heavy
.
0270	X	.	LO2 F/L	.	.	.	X	.	Some Imbedded ORB Fragments
0271	X	.	I/T	.	X	.	.	X	.
0288	X	.	LH2	.	X	.	.	X	.
0290	X	.	I/T	X	.	.	.	X	Skin Fragment
0307	X	.	I/T	.	X	.	.	X	.
0308	X	.	I/T	.	.	X	.	X	.
0309	X	.	I/T	.	X	.	.	X	.
0310	X	.	I/T	.	.	.	X	X	.
0311	X	.	I/T	.	X	.	.	X	.
0312	X	.	I/T	.	X	.	.	X	.
0313	X	.	I/T	.	X	.	.	X	.
0314	X	.	I/T	X	.	.	.	X	.
0368	X	.	TPS	.	.	.	.	.	Multiple Fragments
0401	X	.	I/T	.	X	.	.	.	Stringer Fragment
0443	X	.	I/T	.	X	.	.	.	Stringer Fragment
0444	X	.	I/T	.	X	.	.	X	Stringer Fragment
0445	X	.	I/T	.	X	.	.	X	.
0446	X	.	I/T	.	X	.	.	.	Stringer Fragment
0447	X	.	I/T	X	.	.	.	X	.
0448	X	.	I/T	X	.	.	.	X	.
0502	X	.	TPS	X	.	.	.	.	Multiple Fragments
0511	X	.	I/T	X	.	.	.	X	.
0512	X	.	I/T	.	X	.	.	X	.
0541	X	.	I/T	.	X	.	.	.	Stringer Fragment
0542	X	.	TPS	.	X	.	.	.	Multiple Fragments
0543	X	.	I/T	X	.	.	.	X	.
0544	X	.	I/T	X	.	.	.	X	.

Table 1. Recovered Debris Matrix- Continued

 

Debris Item #	Floating	Sunken	General Location	Degree of Heat Charring				Pos ID	Remarks
				None	Light	Med	Heavy
.
0571	X	.	TPS	.	.	.	.	.	Multiple Fragments
0572	X	.	TPS	.	.	.	.	.	Multiple Fragments
0579	X	.	TPS	.	.	.	.	.	Multiple Fragments
0592	X	.	TPS	.	.	.	.	.	Multiple Fragments
0602	X	.	TPS	.	.	.	.	.	Multiple Fragments
0605	X	.	TPS	.	.	.	.	.	Multiple Fragments
0652	X	.	I/T	.	X	.	.	.	Stringer Fragment
0653	X	.	I/T	X	.	.	.	.	Skin Fragment
0656	X	.	TPS	.	.	.	.	.	Multiple Fragments
0657	X	.	I/T	.	.	.	X	X	.
0661	X	.	Nose Cone Fairing	X	.	.	.	X	.
0679	X	.	+Y ET/SRB Bolt Catcher	X	.	.	.	X	.
0697	X	.	TPS	.	.	.	.	.	Multiple Fragments
0703	X	.	TPS	.	.	.	.	.	Multiple Fragments
0846	X	X	LO2 Skin	.	.	X	.	.	Possible Ogive Fragment
0847	.	X	LH2 Ring	X	.	.	.	.	Intermediate "Z" Ring
0848	.	X	LO2 Skin	.	.	X	.	.	Possible Ogive Fragment
0849	.	X	LH2 Ring	X	.	.	.	.	Intermediate "Z" Ring
0850	.	X	LH2 Ring	X	.	.	.	.	Intermediate "Z" Ring
0851	.	X	LH2 Ring	X	.	.	.	.	Intermediate "Z" Ring
0868	.	X	LO2 Skin	.	.	X	.	.	Possible Ogive Fragment
0869	X		I/T	.	X	.	.	.	Stringer Fragment
0870	.	X	LO2 Skin	.	.	X	.	.	Possible Ogive Fragment

 

[O367] Table 1. Recovered Debris Matrix- Continued

 

Debris Item #	Floating	Sunken	General Location	Degree of Heat Charring				Pos ID	Remarks
				None	Light	Med	Heavy
.
0871	.	X	LO2 Slosh Baffles	X	.	.	.	.	Multiple Fragments
0872	.	X	LH2 Ring	X	.	.	.	.	Intermediate "Z" Ring
0893	.	X	ET/SRB Beam Web	X	.	.	.	.	.
0935	.	X	LO2 Skin	X	.	.	X	X	Part of Aft Dome
0994	.	X	LO2 Disconnect	X	.	X	X	X	Both ET and ORB Halves
1503	.	X	ET/SRB Beam Web	X	.	.	.	.	.
1543	.	X	LH2	X	.	.	X	X	.
1566	.	X	LH2 Ring	X	.	.	X	X	Intermediate "Z" Ring
1567	.	X	ET/SRB Beam Web	X	.	.	X	X	.
1568	.	X	ET/SRB Beam Web	X	.	.	.	.	.
1569	.	X	ET/SRB Beam Web	X	.	.	.	.	.
1601	X	.	TPS	.	.	.	.	.	Multiple Fragments
1602	X	.	TPS	.	.	.	.	.	Multiple Fragments
1626-1	X	.	LH2 C/T	.	X	.	X	X	Attached Together
1626-2	X	.	LH2 C/T	.	X	.	X	X	With Entire
1626-3	X	.	LH2 C/T	.	X	.	X	X	Length of LSC
1626-4	X	.	LH2 C/T	X	.	.	X	X	Contained Fwd Section of LSC

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[O367]

 

 

Figure 1. External Tank Map.

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[O368]

 

 

Figure 2. LO₂ Tank Map.

 

 

 

Figure 3. Intertank Map.

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[O369]

 

 

Figure 4. LH₂ Tank Map.

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