Main parachute, No. 2 of SRB A-12 on STS-3, sustained damage during deployment or initial inflation that resulted in its collapse and failure to sustain load. During an investigation of the materials from this parachute, optical and scanning electron microscope analyses were conducted. This examination identified stains and abrasions on vent lines that appear to have been a result of friction contact with its flotation bag lanyard. Mechanical testing of the vent band indicated a reduction in strength of 37 percent obviously due to structural overload, heat, and ocean water exposure. It is concluded from this and other available data that entanglement of parachutes No. 1 and No. 2 during deployment caused adequate structural damage to main parachute No. 2 to render it unable to carry load

Nichols, R. L.

English

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NASA 
Technical 
Memorandum 
(NASA-TB-d2540)  l4ATEFiIALS INVESTIGATIUAU Uk' U83-3 17 12 
STS-3 PARACHUTE P A U U h E  ( N A S A )  12 p 
MATERIALS INVESTIGATION OF STS-3 PARACHUTE FA1 LURE 
By Ronald L .  Nichols 
Materials and Processes Laboratory  
C S L ~  LLB 
Unclas 
G3/16 28491 
J u l y  1 9 8 3  
Nat~onal Aeronautics and 
Space Admlnlstratlon 
George C. Marshall Space Flight Center 
MSFC - Form 3190 (Rev. May 1Sd3) 
https://ntrs.nasa.gov/search.jsp?R=19830023441 2020-03-21T03:33:26+00:00Z
NASA TM -82540 1 
I. TITLK AND S W T I T L I  8.  R I P O W  DATI  
J u l y  1983 
Materials Investigation of STS-3 Parachute Failure 6. MRCORMIWQ ORGANIZATION 
George C. Marshall Space Flight Center 
Ronal-! L. Nichols 
). CRRCORMIMG Hi0116lYATlON N * r r  AM0 ABORES8 
Marshall Space Flight Center, Alabama 358 12 
10. WORK UNIT NO. 
1 1. CONTRACT OR GRANT NO. 
I Technical Memorandum 
National Aeronautics and Space Administration 
Washington, D.C. 20546 1.0. SPONSORING AGENCY CODE 
I 
S. SUPCLCMCNTMY NOTW 
Prepared by Materials and ?messes Laboratory, Science and Engineering Directorate. 
M3h1 pmchute, No. 2 of SHB A-12 on STS-3, sustained damage during deployment or initial 
inflation that resulted in its collapse and failure to sustain load. During an investigation of the materials 
from this pamchutc. optical and scanning electron microscope analyses were conducted. This examina- 
tion identified stains and abrasions on vent lines that appear to have been a result of friction contact 
with its flotation bag lanyard. Mechanicd testing of the vent band indicated a reduction in strength of 
37 percent obviously due to structuml overload, heat, and o c t m  water exposure. It is concluded from 
this and other available data that entanglement of pamchutes No. 1 and No. 2 during deployment caused 
adequate structuril d a n ~ a g  to main parachute No. 2 to render it unable to carry load. 
17. KCt WORDS rlSTIII8UTlON STLTEMCNT 
o p t i c a l  and scanning e l e c t r o n  microsco~+c 
a n a l y s i s  
Mechanical tes i i irg  
Unclassified - Unlimited 
I 
9 .  SECURITY CLASSIC. (d :Ma row\ 10. SLCURITY CLASSIC. (a8 tUa pa@.) 21. NO. OC CAGES 22. PRICE 
Unclassified ---TUnclassified 11 NTIS 
TABLE OF CONTENTS 
.......................................................... FAILURE L%SCRIPTION 
................................................................... VENT LINE.. 
VENTBAND .................................................................... 
.......................................................... HORIZONTAL RIBBONS 
RUBBERBUMPER ............................................................... 
.................................................................. CONCLUSIONS 
LIST OF ILLUSTRATIONS 
Figure Title 
..................................... I. Parachute canopy structural components. 
............................................... 2. Broken parachute vent line.. 
3. Lanyard fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  
........................................... 4. Green fibers from failed vent line 
............................................. 5.  Frustrum location aid bumper 
6. Stainon rubberbumper ................................................... 
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TECHNICAL MEMORANDUM 
MATERIALS INVESTIGATION OF STSS PMACHUTE FAILURE 
FAILURE DESCRIPTION 
Parachute No. 2 on SRB A-12 was noted to  have sustained significant structural damage during 
SRB reentry. Investigation of the available data relative t o  this parachute indicates that the frustrum was 
tilted at a significant angle during deployment of the main parachutes. All three canopies began to  carry 
load, but approximately 2.5 sec after deployment parachute No. 2 ceased carrying load. This data was 
gathered from reentry film and load cells at the SRB-parachute interfaces. Additionally, it was observed 
that the flotation devices were detached from parachutes No. 1 and No. 2. Parachute No. 1 was 
detached from the SRB by the separation nut pyrotechnic devices, and it subsequently sank prior t o  
arrival of the retrieval vessel. Parachute No. 2 did not detach from the SRB even though the separation 
nuts fired as scheduled. This allowed for the retrieval of parachute No. 2. It was returned to the 
Parachute Refurbishment Facility where it was washed and dried according t o  normal procedure anL 
spread to allow observation of the damage. Figure 1 identifies those structural elements of the SRB 
main parachute involved in this investigation. 
VENT LINE 
The vent lines are extensions of the radial structural componmts and extend across the apex of 
the canopy above the vent. One vent line that connects radials 3 and 51 together was completely 
severed. A green stain was apparent on the vent lines extending from the radial No. 42 to  No. 59 form- 
ing a triangular pattern near the vent band. A vent band was broken ai approximately 3 in. from the 
intersection of radial No. 5 1. The broken vent line is heavily stained with 3 green color. Figure 2 shows 
the failed vent line and the heavily stained arez. 
Samples of all the green material that may have caused the vent line stains were analyzed under 
an optical nlicroscope and compared to the green stained fibers deposited on the vent line. The green 
materials analyzed came from the parachute flotation covers, its webbing, the shock absorber lines, and 
the lanyard that attaches the vent lines t o  the flotation bag risers. The optical microscope analysis con- 
sisted of comparing the fiber diameter, texture, and color. The lanyard fibers appeared to  match the 
stains mosl c\osely. The stained fibers on the vent line and fibers from the lanyard were compared 
utilizing the Scanning Electron Microscope (SEM). Figure 3 shows fibers from the lanyard that attached 
the vent lines to the flotation bags. Figure 4 depicts fibers from the green stained area of the broken 
vent line. The SEM pictures of these fibers appear to  be similar in size, texture, and color. 
Tensile specimens were made from the broken vent line from the failed parachute. The average 
breaking strength of these samples was 3300 lb when pulled to  failure on an Instron tensile testing 
machine at 10 in./min. The vent line material is initially rated at 6000 Ib. 
Two vent lines were removed from parachute No. 2 and tested in tension to destruction. These 
vent lir,es were located at approximately 90 deg to  the failed one. The results of this testing is shown 
ir? the following table. 
Sample No. Breaking Streqth (lb) 
Average = 
These vent lines located 90 deg to the heavily loaded one indicated breaking strengths only 7 
percent below the rated load carrying capability of this webbing. 
Degradation was expected in the strength of the vent line material as it was loaded aear its rated 
load capability. Samples of a nylon webbing of MIL-W-4088D (3500 lb rating) were tested to destruc- 
tion. An additional set was loaded to 80 percent of the average breaking strength and htld for 30 sec. 
The load was released and the samples were pulled to failure. The results of these tests are as follows. 
No. Relodd 
Sample 1 3. Breaking Strength 
Reloaded to  3 172 lb 
Breaking Strength 
Average = 3965 Average = 4397 
A decrease in strength after preloading was anticipated; however, this did not occur. 
This test does not represent the abrasive action t h t  would have occurred due to dynamic motion 
during STS3 fhght. 
VENT BAND 
The vent band is composed of two k ~ g t h s  of 2 in. wide webbing, overlaid and sewn together. 
It limits the volume of vent at the apex of the canopy. The vent band failed at radial No. 3. No other 
obvious damage was noted during our analysis of the failed vent band. The vent band was cut ii.to 
30 in. test samples and pulled to failure in an Instron tensile test machme. The tensile test data is 
shown as follows. 
Specimen No. 
Average = 
UTS (lb) 
The average breaking strength of t h w  specilncns is 2528 Ib indicating a reduction in strength of 
approxiniately 37 percent below the 4030 Ib rating for this webbing. The loading, thermal, and salt 
water exposwes have apparently degraded the vent band niaterial significantly 
HORIZONTAL RIBBONS 
The horizontal ribbons of gorc No. 3 failed tioni the vent band to  the tenth horizontal from the 
skirt band. Several horizontals near the vent band exhibited failures in two locations indicating loads 
applied rapidly, shear t y p  loads present, or possibly both. The nylon horizontals near the vent band are 
r u t 4  at 1000 Ib, while those near the skirt hand are 450 Ib ribbons. 
The failure surfaces of the horizontal ribbons were analyzed under an optical microscope conipar- 
ing those ribbons at the vent band with tho* s t  other locations. ORen nylon fibers crystallize and 
bccom~ opaque when they are rapidly failed in tension. Presence of opaque fibers would indicate the 
failure rate of the tibem No crystallization o i  the nylon fibers was detected at any location. All samples 
analyzcd exhibited melting and the formation of a small sphere at the fractwe surface of the fibers as 
is conimon with ten? .le failure of nylon fibers under slower loading rates. No obvious difference in fiber 
failurc uppnlrunce w, s noted relative to the locution of the licrizontals on tlie canopy. 
RUBBER BUMPER 
A rubber bumper is located on the lower rim of thc frustrua~ to serve as a hunlpr  for the frus- 
trum location aid (FLA). The rubber bumper shown in Figure 5 has signitica~t stains on its upper s u r  
faces that riluy have been caused by rubbing contact with the parachute as it was deployed. Viewing 
of the fillns to determine the angle of the frustrum during deploynletit indicates that parachute No. 2 
may have contacted the nrbber bunlper. Figure b shows the stains on the rubber bumper. They apptar 
to be deposites of molten ~nateriul cllaricteristic of nylon. Efforts exiwnded did not result in the posi- 
tive identit'icution of the source of these stains. 
CONCLUSIONS 
Bawd on preen stains foilnd on the vent bands i~tid nlotioti photograp11 obtained during SRB 
reentry. it lippears tllut the parachute failure was initiated by overloading a vent tine when thc panchute 
flotation bags of pu~tcllutes No. I and No. 2 becanie entangled. This entanglem~nt probably resulted 
in stretching of tlie vent line beyond its elastic limit. When it failed. tile load was transferred tirst to the 
vent band and, after vcnt band failun., to the horizontal ribbons as the radial contracted. resulting in 
failure of the horizontal ribbons. Thr uvailublc evidence indicates that tlie horizontal ribbons near tlie 
vent band were severed early in the f;iilurtl sequence with propugation toward the skirt band from aero- 
dynamic loads di~ring the continuation of descent. This conclusio~~ is derived froni ma!,-hing stains and 
fibers found on the broken vent line to those of the tlotutioti bag lanyard. the lmds data obtained during 
!light on the SRB tape recorder, and long range motion picture c o v e n p  of the reentry of the A-I2 
hardware. 
It appears at this point that the FLA humper damage did not contribute to  the parachute failure. 
Additionally, no evidence was found in the huild records nor frorli testing of niatcrials froni rnain para- 
chute No. 2 that indicated that any substandard niuteriuls contributed to the parachute's failure. 
3 





APPROVAL 
MATERIALS INVESTIGATION OF STS-3 PARACHUTE FAILURE 
By Ronald L. Nichols 
The information in this report has been reviewed for technical content. Review of any informa- 
tion concerning Department of Defense or nuclear energy activities or programs has been made by the 
MSFC Security Classification Officer. This report, in its entirety, has been determined to be unclassifiid. 
w i 
i?j. sL3-L- 
R. J! SCHWINGKAMER 
Director, Materials a d  Processes La&tory 
*US. GOVERNMENT PRINTING OFFICE 1983--/17 


Materials investigation of STS-3 parachute failure

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