NASA 'Fdnisal Memorandum 78204
Testing anc! Environmental Exposure of Parachute Materials for the Solid Rocket Booster Decelerator Subsystem
B. K. Tamehill George C. Marsball Space Pligbt Center MarsbaN Space Flight Center, Alabama
National Aermautics and Space Administ .ation
Sck 4~tiflc and Teehniml Information O%co
ACKNOWLEDGMENTS
The author gratefully acknowledges the contributions of other personnel of the Materials and Processes Laboratory who assisted in the preparation of this report. Particular recognition i s given to L. M. Thompson of Materials and Processes Laboratory and R. E. Runkle of Structures and Propulsion Laboratory.
IT. MATERIALS SELECTKlN AND TEST PREPARATION. . . . . . . . 2
ma LOAD-BEARING WEBBING a a a a 0 a a a a a a a a a a a a a a a a a 5
A. Material Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . 5 B. Materials Test Procedure and Testing . . . . . . . . . . . . . . 8 C. Other Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
I V a CANOPY TAPE AND WEBBING a a a a a a a a a a a . a e 38
V. OCEAN WATER SUBMERSION AT KENNEDY SPACE CENTER(KSC) a a a a a a a a a a a a a a a o . a . a a a a a a a a a a a a a a 44
A. Materials Study of Marine Organism Effects , . . . . . . . . . 44 B. Materials Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 C. Test Results , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A. Load-Bearing Webbing.. . . . . . . . . . . . . . . . . . . . . . . . 57 B . C anopy Tape a d Webbing . . . . . . . . . . . . . . . . . . . . . . 57 C . MatezW Selection and Tests Prepayation, Rinsing
and Drying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 D. Genera l . . . . ...... ............ ..... . ...... 58 E. Omission Considerations . . . . . . . . . . . . . . . . . . . . . . . 58
APPENDIX A - LOAD VERSUS ELONGATION CALCULATION EXAMPLE a . a r a a . a a a a a . a a a a a * a a a a m . a a a a 61
APPENDIX B - PARACHUTE CANOPY MATERIAL TEST M E T H O D * a ~ a a * * a * a a a . * a a a ~ a ~ m . m a m a a a o a 63
LI ST OF ILLUSTRATIONS
F m Title P W
1. General ribbon type parachute oonstructlon canopy with ........................... tapdwebbing location 3
............... 2. Salinity test chart for parachute rinsing 6
3. Static load-elongakion diagram for unexposed material (nylon webbing, MIL-W-27657, Type a) .............. 8
4, Static load-elongation diagram for unexpcsed material, stitched (nylon webbing, MIL-W-27657, Type V) ......... 9
5. Static load-elongation diagram for unexposed material (nylon webbing, MIL-W-4088, Type X ) ............... 10
6. Static load-elongation diagram for unexposed material, ........ stitched (nylon webbing, MIL-W-4088, Type XM) 11
7. Static-load elongation for unexposed material (nylon webbing, MIL-W-4088, Type Vl) ............... 12
8. Static load-elongation for unexposed material (nylon webbing, hITL -W-4088, Type VII) .............. 13
9. Static load-elongation for unexposed material (nylon webbing, MIL-W-4088, Type Xm) .............. 14
10. Static load-elongation for unexposed material (nylon webbing, MIL-W-4088, Type 2WI) .............. 15
11. Static load-elongation for unexposed material, stitchad (nylon webbing, MIL-W-4088, Type M(m) ............. 16
12. Static load-elongation for unexposed material, stitched (nylon webbing, MIL-W-4088, Type XXVI) ............. 17
13. 'VV" pattern stitching used in webbing. ................ 19
TftrXe
Suspension Urn load LnflPadon a d dIs ~ . . . . . e e .
Main riser Une load inflation aad dl pedss........
Rupture on load test in akwalded area (not in the normal ~Umma)..................................
..................... MetOllUc link test wnf&uration
Canopy parachute materials b a t plan. ................ Comparative environmental effects on static load-elongation (nylon webbing, MIL -W-851M, Type I) ............... Comparative environmental effects on static load-elongation .............. (nylon webbing, MSL-W-83144, Type II)
Comparative environmental effects on sW$o load-elongation .............. (nylon webbing, MIL-W-83144, Type V)
Comparative environmentd effects on static load-elongbtfom (nylon tape, M!L-T-4608, Type V, Class C) ............ Comparative environmental effects on static load-elongation ........... (nylon tape, MIL-T-5608, Type II, Class D)
Comparative environmental effects on static load-elongation ........... (nylon tape, MIL-T-5608, Type 11, Class E)
Static load-elongation for unexposed material (nylon ................ tape, MIL-T-5608, Type SV, Class E)
Static load-elongation for unexposed material (nylon ....................... tape, MIL-T-5038, Type V)
LIST OF ILLUSTRATIONS (Concluded)
nEte
46 { ....... KSC submerwion rack after 7 day submersion test ?
Degree of abrasion to parachute material resulting from .......................... 7 day submersion tepif.
.............. Main suspension line unexposed (SEM)
M a n suspension line after submersion for 7 days at KSC (SEM) ........e....e...................
...... Mdn suspension line after approved rinsing (SEM)
Comparative static load-elongation effect of 7 day KSC seawater soak and equivalent weatherometer exposure (nylon webbing, MIL -W -83144, Type V) ............. Comparative static load-elongation effect of 7 day KSC seawater soak and equivalent weatherometer exposure (nylon tape, MIL-T-5608, Type V, Class C) .......... Comparative ststic load-elongation effect of 7 day KSC seawater soak and equivalent weatherometer exposure (nylon tape, MIL-T-5608, Type XI, Class E) .......... Static load-elongation effect of 7 day KSC seawater soak (nylon webbing, MIL-W-4088, Type XXVI) ............ Static load-elongation effei.i of 7 day KSC seawater soak ............. ( nylon webbing, MIL -W -40 88, Type XM)
Static load-elongation effect of 7 day KSC seawater soak (nylon webbing, MIL-W-27657, Type 11) ............. Static load-elongation effect of 7 day KSC seawater soak ............ (nylon webbing, MIL -W-4088, Type XMII)
Polynomial least squares regression analysis ..........
Table
LI ST OF TABLES
Analysis of Six SRB Parachute Rinse Water Samples and a ~ a p Water Sample .............................. 5
Parachub Load-Bearing Materials ................... 7
Static Breaking Strength of Control (Unexposed) .................... Parachute ~ o a d - ~ e a r i n g Yebbing 18
............................ Test Procedure Steps 22
Riser Inflation Loads and Breaking Strength Procedure for Suspension Lines on Main and Drogue Parachutes ......... 23
Test Results of Inflation Loads ou Main Suspension Line (Stitched LA, MIL-W-27567, Type ll; Rated Strength - 40001b) ..................................... 24
Test Results of Inflation Loads on Drogue Suspension Line (stitched 9A, MIL-W-4088, Type XWI; Rated ............................ Strength - 12 000 lb) 28
................................. Abrasion Test 30
Results of Metallic Suspension Link Strength Test ......... 32
Parachute Canopy Material ........................ 33
............. Parachute Canopy Materials Test Summary 35
.................... 13. Parachute Material After Rinsing 48
14. Comparative Breaking Strength of Parachute Webbing and Tape A f t e r 7 day KSC Seawater Soak, and three ........................... Weatherometer. Cycles 49
TECHNICAL MEMORANDUM
TESTING AND ENVI RONMENTAL EXPOSURE OF PARACHUTE MATERIALS FOR THE SOL1 D ROCKET BOOSTER
DECELERATOR SUBSYSTEM
SUMMARY
The materials described in this report were tested specifically for the recovery and reuse of the Solid Rocket Booster Decelerator Subsystem (SRB DSS) under simulated environmental conditions expected during flight. The tests were restricted to static conditions and primarily to rlonmetallic materials. Nylon was chosen as the parachute fabric because of its elongation character- istics, durability under "use" ?onditions, history of successful use in decelera- tors, and strength.
With the exception of one webbing, a.ll material met the strength tests. A l l load-bearing webbing met o r exceeded the required strength requirements and proved to have a reuse capability of 40 ocean drop-recoveries a s limited to UV, seawater withstanding capability, and rinse and dry processes. Worst-case conditions were used o r exceeded in inflation load testing. The first recovery rinse, and dry procedure resulted in greater strength degradation than subse- quent cycles.
The canopy materials were alw exposed tc Amulated "use" conditions in addition to the tests stipulated in their respcziive m%tary spevifications. Dynamic testing (i. e., flight and drop testing) is still i n progress and cohld result in f ~ r t h e r changes o r modifications to the present parachute's design and material composition.
I. INTRODUCTION
In the basic Space Shuttle configuration, the reusable Orbiter is "piggy- backed" on an expendable External Tank ( ET) . Two reusable SRB 's a re strapped to the ET. This report describes the nylon and related materials comprising the parachutes in each SRB DSS. Each DSS consists of a drogue and three main parachutes which open during SRB reentry, slowing the SRB adequately for
ocean impaot, flotation, and subsequent recovery. Each main parachute is 115 ft in diameter (D~), has ninety-six 62 R suepension lined dispsrslon bridles
70 ft in length, and 40 ft risers. The canopy is a ribbon type with 16 percent geometrlc porosity, The drogue parachub is 54 ft in dlameter and has sixty 100 ft swpenslon lines (Fig. 1).
These enormous parachutes have tbe highest strength of any fabrtcated to date. To our knowledge, the largest load ever dropped by parachub and recovered was in the 50 000 lb rage. Each SRB after firing will veigh approxi- mately 170 000 lb. Considering the weight involved, parameters such as design, material solectlon, material and dynamic testing, and deployment are extremeiy critical. To keep within bwiget restraints, recovery and reuse are necessary. t
All of these factors must be tested in simulated "usev environments.
This project was initiated by performing fabric material studies, testing, and analyses through literature research, and Government and Manufacturer/ Vendor contacts. Materials acceptance and identification were performed by tests and analyses. Environmental exposures simulated ascent, ocean drop, recovery, rinsing, drying, and reuse. Laboraiory test conditions included heat, artificial seawater soak, and W light exposure (utilizing a weatherometer), tap water rinse, and oven drying. Tests were then selected to determine the strength, elongation, and durability o r degradation resulting from these exposures. It was estimated that the SRB DSS could remain in the ocean for 3 days before recovery. Therefore, one ozean drop-recovery (72 hr) was designated as one cycle. Ten cycles of exposure for canopy matezials and up to 40 cycles for other fabrics known as 'load bearingv materials (e.g., suspension lines and risers) were c o q k t e d . Test plans, methods, etc., are presented for each type material. From these tests, the number of parachute drop-recoveries and reuse cycles may be projected.
MATERIALS SELECTION AND E S T
A, Materials Selection 1. Parachute Webbing and Tape. Materials screened were those pre-
viously evaluated with specified proven properties and a history of successful decelerator expex%nce, Natural fibers were excluded due to their lack of weathering, durability, and strength. Voluminous reports on syntf'etic fibers
GORE GEOMETRY 81 POROSITY
DETAIL B
Figure 1. General ribbon type rachute construction canopy with tape/webbl: ,?: location.
1
developed by the Air Force, Navy, Army, cBnd revsrd rwrrearch and mamrfac- bring &nns were studied. Arbmid matartale were considered; however, bscou8e of their limited use and their abrasion anrf elongation chanlcteriatlce nylon was circzsn. Considering akt the *'ueeM environmsnb, nylon hod thg mo8t dsdrable properties (:a& zc s!@dcant bat expooure), and a hiratory of repeated urse. t
1 2. StitaUng - Patterns. ft was decided to stit& selected parachub webbing I which would car!:y the bruct of the load due Qb tb kaok of proper cap tan holders
(jaws) for the Dlstron machine. Stitchhg ~ i m Q & s acd marly as poesible, the parachutes to l-4 fabricated. Stitcblng usually reduces the strength of tho wt Wqg
i and givcs a more realistic tensile strength i n use as well as a potential we&-link in the d,?sign/materials used. r
The stitching and patterns chosen were taken from Wright A!r Fo D6:elopmer.t Center, WADC Technical Report 56-313, Part II, ''A S'udy Paracbuie Seam Design Crlterla," June 1956.
6. Test Preparation 1. Environmental Exposure Conditions. The weatherometer was utilized
to simulate ocean exposure after SRB and parachute drop. All samples were scaked in artillciai seawater approximately 1 h r prior to attaching to the test fixture inside the weatherometer. The test fixture rotated around a xenon light 3: a distance sufficient to emit "one sun" in the W spectrum. Exposure was continued for 7 hr/day with sample removal and immersion in seawakr a t least once during this period to k e q the nylon wet and to prevent salt z~.yetallization. A t the end of 7 h r , the samples were placed i n seawater and s ~ ~ a k e d over night, o r weekend, until the next exposure period. Three of these 7 h r exposures (21 hr) a re referred to as one cycle, i.e., a 3 day period that parachutes may remain in the ocean before recovery.
Samples of seawater were taken periodically and the percentage of chloride was measured to maintain a 3.5 to 4 percent salts concentration,
2. Rinse and Dry Procedure. Before testing for environmental exposure, it was necessary to determine the number of rinsing operations necessary to reduce the s & i t y to a level that would not be detrimental to the parachute. With the thicker load-bearing nylon samples, a sample of water wee taken from each rinse solution. Salt content was determined by measuring the chloride content and conductivity. Total solid salts were also determined on two samples for a comparison test but were di~,continued when thev agreed with chloride and
+. ;- r - j , .. . . ?"?-+: ;:, ;< :h:,:, , ~, \ ;,,:,~~*4-<. F...c, ,. . , ,.:.,*,. ,
-,.,-"4-Y . . * , . ;- .. -.. . .. ;.+>. .!, ),.&.q.<, ~ . @, <<!? .-;:y;'; ?'* L- ;. . , ,: . . .. ,. ,. . , c , . .. , . , - 1 , . . . . , - 3, .. *:&&%., .:$. , , ,-+; - ,;#& ; :ti ,r,yy 5. . . r , . . . .. ., -: . ,
.,a . 5. , . , ,.,+, _ * - - . , .~ , h . . /
.< . . . ' .. , , * .. . . .' ,' - -..--..-.-.-- u -....A i r., .:...Ai' . : . - - . - .-- - - .. - .- . - -
Ill. LOAD-BEARING WEBBING
A. Material l n spection Webbing identdflcation is given in Table 2, An overall examination wae
performed on each makria3 received. No uneven dyeing, wewing, or wrong color was noted in tbs rolls and a l l were labeled properly. There were no abraeion marks, broken or missing ends, twist or distoflon in the webbing weave, nor cub or tears. All military specification defect criteria were met,
8. Materials Test Procedure and Testing 1. Static Tensile Loading. All tests, unless otherwise stated, were
specified in the webbing military specifications and procedures taken from Federal Standard 191. Static tensile tests were conducted on a 10 000 lb capacity Instron or a 60 000 lb capacity Riehle Testing Machine. Cn the Instron, specimens were mounted in 4 in. diameter capstan jaws with approximately 15 in. betweeu jaw centers. A speed of 2 in. /min was used and extension measurements were made with a ruler calibrated in 1/16 in. Extension readings were taken at 1/S in. intervals. Unless otherwise stated, two samples of each webbing were tested to rupture. Pblynomial least squares regression analysis was used for the load-elongation diagrams (Figs. 3-12) for all load-bearing webbing, and values for rupture loads a r e given in Table 3.
I I J 0 10 20 30
ELONGA flON 1%)
Figure 3. Static load-elongation diagram for unexposed mate rid (nylon wbbing, MIL-W-27657, Type II) .
Figure 4. Static lozd-elongation diagram for unexposed material, stitched (nylon webbing, MIL-W-2';657, Type V) .
ELONGATION (%I
Figure 5. Static load-elongation diagram for unexposed m~terial (nylon webbing, MId-W-4088, T ~ p e X) .
Figure 6. Static load-elongation diagram for unexposed material, stitched (nylon webbing, MIL-W-4088, Type XM).
10 20
ELONGATION (%I
Figure 8. Static load-elongation for unexposed material (nylon webbing, MIL-W-4088, Type VII).
10 20 ELONGATION (%I
Figure 9. Static load-elongation for unexposed material (nylon webbing, MIL-W-4088, Type MTI) .
10 20
ELONGATION (%I
Figure 10. Static load-elongation for unexposed material (nylon webbing, MIL-W-4088, Type XVI) .
ELONGAT ION (%I
Figure 11. Static load-elongation for unexposed material, stitched (nylon webbing, MIL -W -40 88, Type XXIII) .
ELONGATION !%I
Figure 12. Static load-elongation for unexposed material, stitched (nylon webbing, MIL-W - 4OS8, Type XXVI) .
TABLE 3, STATIC BREAKING STRENGTH OF CONTROL (UNEXPOSED) PARACHUTE LOAD-BEARING W$ElBfPrlG
- - -
Sample Identlflcatlon
am-W-27657, Type U 1A 1A Avemge
MIL-W-27657, Type va . 2A
2A Avernge
MIL-~-4068, Tjpe V1 3A 3A Avenge
MIL-W-4088, Type VU 4A 4A Average
MlL-W-4088, Type X 5A 5A Average
MJL-W-408H. Type XTll 6A 6A Average
LIIL-w -40~s. Tjpe XIX" HA XA A ve r.Ve
MIL-W-4038, Type xXITIa 9A 9A Average
Rated Strength (lb) Breaktng Force (lb)
a. \\.obMng etitched with a 1 in, 1 0 6 at both end$. A boll was pnssed through loops, placed in Inetron, ~ n d tested. S:tmples ruptured In etltched area.
- DROGUE CHUTE - MAIN CHUTE
10 20 30 40 50 60 70
TIME (MC)
Figure 14. Suspension line load inflation and disreefing peaks.
TIME (wc)
Fibpire 15. hlain r iser line loud inflntion and disrccfing peaks.
An extended life test in simulated "use" ennmnments was performed on the materials at the design limit load of 40 percork: of the material's rated strength, which includes a safety factor. The @'her inflation loads range from an under-design limit load to several overload conditions. This gives some idea of what may be expected if an momaly occurs during deployment (e. g., non- simulttlneous opening of the parachute cluster, premature disreefing, failure of a main parachute to open, etc. ) . The webbing was subjected to seawater soak and I'V light according to the procedure given in Table 4 and Figure 16.
TABLE 4. TEST PROCEDURE STEPS
Preload sample to 1 percent of its rated strength; measure reference length of sanq .t:
Load sample to inflation load; measure elongation
Hold inflatian load for required time a
Relax to seconciarj load position; hold for required time"
Relax to preload 1 percent position; measure elongation
Remove sample, coctinue environmental e.uposura cycling, and subject to rinse and dry proce&,i-as established.
Cycle each material for a minimum of ten 21 h r exposure cycles, repeating test procedure steps 1 through 6 before the first cycle (control) and after cycles I , 4, 7, and 10. Con- tinue to 40 cycles for extended life test, repeating inflation loads after 20, 30, and 40 cycles
Load to failure
a. Hold inflation load constant for time period from top of first to i ; ~ p of flnal peak. Hold secondary load as depicted on graph from end of disreefing to deflation. Consider drogue chute secondary load time ir.terva.1 from peak of dereefing point to deflation. This is due to the slow rise time (2 in. /min. ) of +he testing apparatus.
Figure 16. Test cycle.
The number of exposure cycles was %pendent on the materials and their capability tr, wSbtand additional exposure-loadiqg. Test loads applied are specified in Table 5. The inflation tests call for dynamic testing. Since the test machines used in this hboratory are not capable of the rapid rise (load) time, the regular 2 in. /min wes used to reach the first inflation (reefed) peak and the load was held for the time period required for final disreefing. A secondary load was then held for the time required for complete deflation, representing full main parachute inflation and descent to touchdown. These etatic loads represent a much more severe condition than the dynamic load test. This w'as obvious during cycling and testing uhile holding the specified time interval at p xdc loads. Webbing fibers could be heard snapping, and several webbings ruptured toward the end of the hold time period. Tables 6, 7, and 8 give r e ~ u l t s of these tests.
TABLE 5. RISER INFLATION LOADS AND BREAKING STRENGTH PROCEDURE FOR SCSPENSION LINES ON MAIN AND
DROGUEPARACHUTES
Test Number
1. Reference, load to failure
2. 25 percent of rated load, Ib
3. 40 percent of rated load, Ib, exbnded life test
4. 60 percent of rated load, Ib
5. 75 percent of rated load, lb
6. 85 prcent of sated load, lb
Hold time at inflation peak, l o ~ d 1 dues listed above
Secondary peak and hold time
Sample IdenUfi :ation
1A-1
1A-2/1000
1A-3/ 1600
1A-4/2400
1A-5/3000
1A-6/3400
A L L 1A - 23 88C
525 lb 7 sco
ALL 8A A L L 9A - 23 sec 13 sac
1450 Ib 2800 lb 7 sec 8 sec
Rated Strength: Main -- MIL-W-27657, Type I1 (1A) 4000 lb; Riser - MIL-W- 4088, Type XM (8A) 10 000 lb; Drogue - MIL-W-4088, Type XXIII (9A) 12 000 lb
TABLE 6. TEST RESULT'S OF INFLATION LOADS ON MAIN SUSl?ENSION LINE (STITCHED 1A, MIL-W-27567,
TYPE n; RATED STRENGTH - 4000 ib)
(25 percent of Rated Stre.lgth - 1000 lb)
Table 5 Test No. -
Ultimate Elong.
10 1/4
9 3/4
9 3/4
3 1/2
10
Load to Failure -- 3637 11
11
10 1/4
10 1/2
10 1/2
10 5/8
Environmental Cycles
--
Load to Failure --------- 2900 lb
(40 percent of Rated Strength - 1600 lb)
Preload Length (in- ) --
Passed - No Failure
Load to Failure --------- 1818 lb
Elongation at Load (9
Note: No length measurements taken after 10 cycles.
F i n d Preload Length
(in. )
Table 6 Teet No.
TABLE 6, (~oncluded)
Preload Environmectal Length
Cyclee (in,
Elongation Final Preload at L a d Length
(X (in*
(60 percent of Rated ~tre&h - 2400 ib)
Failed at Inflation Load - 2400 lb
(75 percent of Rated.Stren@h - 3000 lb)
10 5/8 Failed While Holding at Inflation Peak - 3000 lb
(85 percent of Rated Strength - 3400 lb)
6 I 9 11/16 Failed at 3063 lb I
TABLE 7. TEST RESULTS OF INFLATION LOADS ON MAIN RISER HARNESS (STITCHED 8A, MJL-W-4088, TYPE ,XX;
RATED STRENGTH - 10 000 Ib)
Table 5 Test No.
Preload Elongation Environmental Length at Load
Cycles (in* ) (%)
Final Preload Length (in. )
(25 percent of Rated Strength - 2500 Ib)
Load ta Failure - 9900 Ib
11
10 1/4
I0 3/8
10 1/3
10 1/2
Load to Failure - 7515 lb I - I
(40 percent of Rated Strength - 4000 Ib)
10 3/8 12 10 3/4
9 7 / 8 14 10 3/8
9 3/4 14 10 1/2
9 3/4 16 10 9/16
9 7/8 16 10 1/2
- 22 - Passed - No Failure
I qad to Fdlure - 5493 lb I I 1
Note: No length measurements taken after 10 cycles.
, . . .
i P'. . .
l . -. F . 1
?: .. .. - *: i
""i I .'-- : a . .
.... . 1 <- - , - . . .. . . -.
i ::. . . ! , , i
TABLE 7. (concluded)
I ( Preload I Elongation 1 Final Preload . Table 5 Test KO,
Environmental at Load Length Cycles '
(60 percent of Rated Strength -- 6000 lb)
Load to Failure - 6050 lb
(75 percent of Rated strength - 7500 lb)
(85 percent of Rated Strength - 8500 lb)
5
5
Failed While Holding at Inflation Peak - 8500 lb
4
7
9 7/8
9 7/8
17 1 10 3/4
Failed at 6850 lb I
TABLE 8. TEST RESULTS OF INFLATION LOADS ON DROGUE SUSPENSION LINE (STITCHED 9A, MIL-U'-4088, TYPE
XXJII; RATED STRENGTH - 12 000 Ib)
Table 5 Test No.
(25 percent of Rated Strength - 3000 lb)
Environmental Cycles
Ultimate Elong. 20%
15
14
12
13
12
Load to Fail1
Load to Failure 11.150
12 1/2
10 1/2
10 9/16
10 5/8
10 5/8
re - 10 395 lb
Preload Length
(in. )
(40 percent of Rated Strength - 4800 lb)
Elongation at Load
(%
Note: No length measurements taken after 10 cycles.
Final Preload Length
(in.)
- Passed - No Failure
2o I - Load to Fdlure - 6300 lb
TABLS 8, (Concluded)
I I Preload I Elongation I Final Preload 1 Table 5 I Environmental Test No. Cycles
(60 percent of Rated Strength - 7200 lb)
Load to Failure -- 8480 lb I I
(75 percent of i?ated Strength - 9000 lb)
10 1/8 2 1 10 13/16
10 11'8 18 10 11/16
10 1/8 - 11 1/8
10 1/4 2 2 11 1/18
Failed While Holding at Inflation I ( Peak - 9000 ib I
(85 percent of Rated Strength - 10 200 lb)
1 I Failed While Folding at Inflation Peak - 10 200 lb I
TABLE 10. RESULTS OF METALLIC SLSPENSION LINK STRENGTH TEST
Suspension Line, Drogue (hITL-IN-9088, Type IiXlIX) Par t No. 52 B 6660-1
J
Rupture ( lb) Sample
Suspension Line, Main (MIL-W-27657) Part No. MS 22021-1
Link Bent ( W
8550 EHSS 9A
Average
Note: These values exceed the design limit load.
I
6000
IV. CANOPY TAPE AND WEBBING
7250 A
EH33 1A Average
Reqidremer~ts were not a s den~anding on the canopy n ~ a t e r i d n ~ listed in Table 11 a s on t l ~ e load-bearing we5bi1-g. Therefore, no permanent deformation test nor wwst-case "use" conditions s e r e determineci during these analyses, The ent3ronmentd conditions were severe a s in previous webbings with one cycle consisting of three 7 h r exposures to LW Ught in the weathcrometer while keeping s,m~ples wetted with the artificial seawater md an overnight seawater so:& ( 2 1 h** ITV light ex -+sure ) . Rupture loads were n~easured on the Instron mnchine in determlninl: the effects of heat exposure, seawater soak and rinse, environmental cycles, md environn~ental cycles plus abras;ion ( ~ i g , 20). A s ~ ~ m m a r y of results is @veil in Table 12.
3517
In collaboration with the previously chosen parachute manufacturer, The Pioneer Parachute Co., i t was found that the shrinkage regained its normal Iewth when subjected to n load. This keeps the parachute to within approxin~ately 95 p r c c n t of its initial fabrication measurements.
TABLE 1
1.
PA
RA
CH
UT
E C
AN
OPY
MA
TE
RIA
L
Lab
No.
N
ylon
Tape
per
MIL
-T-5
638
A~
~li
catf
on
EH
33
4
Type:
V,
Cla
ss C
, 2 i
n. w
idth
, 30
0 lb b
reak
ing
str
eng
th
Rad
ial,
mai
n
EH
33-5
Type I!,
?,a
ss D
, 2 ia.
wid
th,
400 lb b
reak
ing
str
eng
th
Hori
zonta
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No loadelongation curves were plotted for abraded samples since abra- sions resulted in very little damage to samples pbraded after the environmental and the load-environmental cycles. Figures 21 through 28 give the comparative environmental effects on static load-elongation curves.
A description of the parachute canopy material test method is given in
- I ENVIRONMENTAL CYCLE - 6 ENVIRONMENTAL CVCLES
a - 10 ENVIRONMENTAL CVCI.ES
1 a
Figure 21. Comparative environmental effects on static load-elongation (nylon webbing, MIL-W -83144, Type I).
ELONGATION 06)
Figure 22. Comparative environmental effects on static load-elorgation (nylon webbing, MIL -W-83144, Type 11).
ELONGATION 4%)
- 1 ENVIRONMENTAL CYCLE - S ENVIRONMENTAL CYCLES
A - 10 ENVIRONMENTAL CYCLES
Figure 23, Comparative envirofimental effects on static load-elongation (nylon webbing, MIL -W -83144, Type V) ,
0 -CONTROL 0 - 1 ENVIRONMENTAL CYCLE 0 - 6 ENVIRONMENTAL CYCLES A - lo ENVIRONMENTAL CYCLES
J
ELONGATION (%I
Figure 24. Comparative environmental effects on static load-elokation (nylon tape, MIL-T-4608, Type V, Class C).
Figure 25, Comparative eavlronmental effeob on stati.0 load-elongation (nylon tape, MIL-T-6608, Type R, Class Dl,
0 - CONTROL 0 - 1 ENVIRONMENTAL CYCLE 0 - 5 ENVIRONMENTAL CYCLES A - 10 ENVIRONMENTAL CYCLES
10
ELONGATION 4 % )
Figure 26. Comparative environmental effects on static load-elongation (nylon tape, MIL-T-5608, Type II, Class E) .
ELONGATION (%I
Figure 27, Static load-elongation for unexposed material (nylon tape, MIL-T-5608, Type IV, Class E),
10 20 ELONGAT ION (%I
Figure 28. Static load-elongation for unexposed material (nylon tape, MIL-T-5038, Type V).
V. OCEAN
A, Materia
WATER SUBMERSION AT KENNEDY SPACE CENlER (KSC)
s Study of Marine Organism Effects
A study was planned to determine the effect of seawater bioorganisms on the nylon parachcte material after some concern was expressed as to:
1) What types of growths a re likely to be encountered?
2) Do any of the organisms mechanically o r chemically degrade the material ?
3) How effectively is %he marine life removed by the planned rinsing operations ?
Eight materials were selected for exposure. Parameters for selection were (1) importance o: function in SRB recovery, (2) military specificatic n requirements (minimum of one material per specification), (3) strength of materirl, and (4) weave pattern.
The samples were mounted on a rack and placed 35 ft deep in the ocean approximately 700 yards offshore from KSC. Sonle degree of abrasion was expected due to the close proximity of samplss and the action of the sea while submerged. The samples were recovered after 7 days, placed in a container of the seawater, and returned to the M F C Materials and Processes Laboratory,
Be Materials Testing Ar, outline of marine organism studies and distribution of the eight
samples selected a re given in the following listing:
1) Unexposed nylon samples
2) After 7 days KSC ocean ~ubmersion
3) After approved rinsing procedure,
Unexposed samples were received by biological personnel of the University of Maryland hIicrobiology Department [ Ij , and the IWFC Materials and Pmcesses Laboratory for control analysis.
After 7 days of ocean submersion and after the ap~mved rlnsing procedure, both sets of samples were sent to MSFC biological personnel and to the Univer- sity of Maryland for microscopic quantitative analysis for a colony count of marim orgd sms and scanning el 3 c b n microscopic (SEM) emmination for identification. Samges from Groups 2 bi-rd 3 were also retained by the Materials and Processes Laboratory for load-elongation and ultimate breaking strength analysis. Additional SEM analyses with energy dispersion of X-ray (EDAX) attachments were processed by the Materials and Processes Laboratory for debris and inorganic contamfnants.
Biodegradation tests ;m presently underway at the University of Maryland to determirm if there are actually any detrimental effects on nylon by marine organisms or fungi.
Figure 29 shows the KSC submersion rack being removed to the ship after a 7 day submersion test. Figure 30 shows the degree of abrasion on some of the samples.
C. Test Results Results indicate the specimens examined in the "as recaivedv condition
with SEM micrographs of 50X, 100X, 200X, 500X, and lOOOX magnificatio~~s had no significant contamination. After exposure to seawater for 7 days, specimens of the same material were examired by SEM to determine if any damage was detectable to the material and what, i f any, types of growth were present, There was no noticeable growth on the specimens examined at the Materials and Processes Laboratory (Figs. 31, 32, and 33). EDAX analyses were also nude of the eight exposed specimens and the following elements were detected: Na, Mg, Si, C1, K, C a, and P. From Table 13 it can be seen that after iinsing a clean surface is present with only minute amounts of debris. Therefore, no potential problem is predicted using the standard rinsing procedure.
Comparative bresking strength and static load-elonga'iion effects are given in Table 14 and Figures 34 through 40, respectively. The weatherometer results, where available, were exposures to artificial seawater for the equivalent time ( 7 days) under laboratory conditions. Other comparative values shown were control (unexposed) samples. Two of three samples show a significantly larger loss in breaking strength and a trend toward greater e lowtion.
TABLE 14. COMPARATIVE BREAKING STRENGTH OF PARACHUTE WEBBING AND TAPE AFTER 7 DAY KSC SEAWATER SOAK
ANL THREE WEATHEROMETER CYCLLB
A vc r:\ge
hln-T-SGOP, Type V, Class d
Control L'ncxposed
Sntiiple ( 1'4
1 $20 1 7!M - 1 755
3 SO 390 - 3S5
1 180 1 110 - 1 160
645 GI0 - GI
4 100 .! 050 - 4 075
c) 640 10 160 - 9 900
9 960 10 180 - 10 070
14 100 13 900 - 14 000
b. Scvcrcly :~br;ddcd; anchor Uc-down brokc loose on rack at s e a on two smiiplrs :md abrasion i~ visiblc on tldrd s .mplc with rccordcd value.
0 -CONTROL 0 - 3 ENVIRONMENTAL CYCLES LS - KSC SEAWATER SOAK
ELONGATION (961
Figure 34. Con~pnr;ltive static lond-clongntion effect of 7 day KSC scawatcr soak ;tnd cqiiv;llcnt wcathcronlctcr exposure (nylon webbing,
ItIII.-!Y-S3144, Typ: V ) .
O -CONTROL [3 - 3 ENVIRONMENTAL CYCLES A - KSC SEAWATER SOAK
10 30
ELONGATION 4%)
Figure 35. Comparative static load-elongation effect of 7 day KSC seawater soak and equivalent weatherometer exposure (nylon tape,
MIL-T-5608, Tvpe V, Class C) .
0 -CONTROL 0 - 3 ENVIRONMENTAL CYCLES A - KSC SEAWATER SOAK
ELONGATION (%I
Figure 36. Comparative static load-elongation effect of 7 day KSC seawater soak and equivalent weatherometer exposure (nylon tape,
MIL-T-5608, Type 11, Class E) .
O -CONTROL Q - KSC SEAWATER SOAK
ELONGATION (%I
Figure 37. Static load-elongation effect of 7 day KSC seawater soak (nylon webbing, MIL-W-4088, Type xXVI) .
O -CONTROL 0 - KSC SEAWATER SOAK
10 20
ELONGATION 4%)
Figure 38. Static load-elongation effect of 7 day KSC seawater soak (nylon webbing, MIL-W-4088, Type XIX) .
O -CONTROL 0 - KSC SEAWATER SOAK
ELONGATION 4%)
Figure 39. Static load-clongation effect of 7 day KSC seawater soak (nylon webbing, MIL-W -27657, Type XI).
10 20 ELONGATION (XI
8 - CONTROL - KSC SEAWATER SOAK
Figure 40. S\;atic load-elongation effect of 7 day KSC seawater soak (nylon webbing, MIL -W-4088, Type XXIII) .
On the basis of further technical literature research and, especially, work done under the supervision of Dr. H. P. Vind of the Naval Facilities Engineering Command (21 with nylon and other plastics, i t is projected that the marine environment will present no problems insofar a s microorganisms a r e concerned. Dr. Vind found no significant degradation in nylon sheet samples o r nylon rope sanlples following subn~ersion in aerobic and anaerobic environments for 2.5 years. The difference in strength i~~dica tcd by the MSFC study was probably caused by the mamer in which the samples were mounted, causing two samples to break loose a t one end resulting in an abrasive action. A degree of abrasion occurred to other samples due to the action of ocean currents, tides, etc, , flowing through and around them.
VI. CONCLUSIONS
A. Load-Bearing Webbing
1. Stitching Patterns. Stitching the nylon webbing is extremely important since it may reduce the rated strength of the material up to approximately 17 percent. A "V" pattern is used in sewing with three to eight points. The width and strength of the webbing governs the size cord and number of points. Large cord with more points severs nylon fibers in the webbing and creates a weakened material. Too snlall a cord o r insufficient points will break the cord and dsc! weaken the webbing, making the optimum selections critical. The control samples listed in this report all broke a t the stitched point area near the rated strength of webbing which indicates near optimunl conditions.
2. Abrasion ResisLmce. The load-bearing materids, especially r i se r s and suspension lines, are very susceptable to abrasion. When under a load in the sea, damage which would require a ch'mge-out o r refurbishn~ent may occur. The parachute should be recovered a s soon as possible, especially in rough seas.
B. Canopy Tape and Webbing
Canopy webbing to MIL-W-53144, Type I1 is slightly out of specification tolerence in strength. It should be rejected o r new webbing ordered md retested.
C. Material Selection and Tests Preparation, Rinsing and Drying
The recommended conductivity of the final rinse solution after recowry of the parachutes is 0.125 millimhos/cm (approximately 52 ppr.1 chloride con- tent) above that of the incoming water. The rinse water should be potable water at ambient temperature. Due to the size and number of parachutes, this saline level may have to be less restrictive. To limit seawater salt crystallization and, more importantly, hygroscopicity, controls should be e s tablished to insure the minimum level (em g. , weighing the parachute after drying, etc. ) . It is further recommended that the oven drying temperature be 140°F * lo0 until completely dried.
D. General Generally, the parachute materials met all requirements within design
limitations. Worst-case conditions were used d ~ r i n g static and environmental testiw. The results have been coordinated with design personnel.
An overall evaluatioa that covers individual tape and webbing tests is not possible since the nylon materials cover strength rating from 300 to 15 000 lb, all types of weave patterns, shrinkage factors, abrasion characteristics, e tc. Each material must be evaluated for its particular use under its real o r simu- lated environmental exposure.
E. Omission Considerations The parachutes are in the initial phase of fabrication and air drop testing.
Each failure or anomaly has and will continue to add modifications, changes in design, and possibly new inaterials or fabrication techniques. Changes have been made in parachute canopy widths, a second reefing line has been added to the drogue parachute, and the webbing has been reinforced around reefing rings. Other minor changes are anticipated.
REFERENCES
1 . Colwell, R. R. and Zachary, A.: Study to Determine the Aquatic Biological Effects on the Solid Rocket Booster (SRB). Department of Microbiology, University of Maryland, College Park, Maryland, Contract Number NAS9-32143, September 30, 1977.
2 . Muraoka, J. S. and Vind, H. P. : Durability of Plastics in Anaerobic Marine Sediments. TN N-1402, Civil Engineering Laboratory, Naval Construction Battalion Center, Port Hueneme, California, October 1975.
BIBLIOGRAPHY
Boon, J. D. : Nethod and Regulations Governing Cleaning and Washing of Parachutes. TR No. 3-62, U, S. Naval Parachute Facility, El Centio, Califovnia, June 1962.
Hawkins, G. Michael: Multifiber Bulletins X-215, X-216, X-159, X-228, X-233, X-82, X-56, K-1. IjuPont Technical Information, TexAile Fibers Department, Industr,,ll Pivision, Wilmington, Delaware.
Runkle, Roy E., Beck, R. L., and White, J, E. : Space Shuttle 146-Inch Diameter Solid Rocket Boaster Recovery Concept. NASA TRI X-64905, RInrshdl Space Flight Center, Alabanla, PTovember 1974.
Skelton, J., Sebring, R. E., and Freeston, W. D., Jr.: hIaterids for Aerial Recovery Parachute Systems. AFRIL-TR-69-180, Fabrics Research Laboratories, Inc., WPAF Base, Ohio, July 1969.
APPENDIX A
LOAD VERSUS ELONGATION CALCULATION EXAMPLE
A forced intercept polynomial least squares regression analysis (Fig. A-1) was used to plot the load versus elongation curves in this techniual memo- randum. Usually polynomial coefficients of Degree 2 or 3 was used to produce the curve. Higher degrees, though giving correlation coefhients closer to unity, were not used because L e small amount of data caused the curves to interweave between data points,
Figure A-1. Polynomial least squares r6gression analysis.
.- 1 ..., -. .. 1.. . . .. .- . 1. 1 . -. . - ... . . -I . ,". ... ,̂* . . .. .... -... I.. ..* . ...- - - ... .. -- - ̂ - ..- .
Figure A -1. (Concluded)
