Calculation 12. Procedure

I Calculate the compression set expressed

¶12.1 Original Thickness Measurementas a percentage of the original deflection as fol- Measure the original thickness of the specimen lows: to the nearest 0.02 mm (0.001 in.). Place the specimen on the anvil of the dial micrometer so CB = [(lo - I , ) k - l.)] x loo (2) that the presser foot will indicate the thickness at where: the central portion of the top and bottom faces. C. = compression set (Method B) expressed as

¶12.2 Application of CompressiveForce-Place percentage of the original deflection, the test specimen between the plates of the com- r, = original thickness of specimen (12. I), pression device with the spacers on each side, I, = final thickness of specimen (12.3, and allowing sufficient clearance for the bulging of

= thickness of the spacer bar used. the rubber when compressed (Fig. 3). Where a lubricant is applied, it shall consist of a thin NOTE5-Lubrication of the operating surfaces of coating of a lubricant having substantially no the compression device is optional while giving more action on the rubber. For most purposes, a silicon reproducible results, lubrication may somewhat alter the compression set values. or fluorosilicon fluid is suitable. Tighten the bolts so that the plates are drawn together uniformly until they are in contact with the spacers. The 14. Report amount of compression employed shall be a p 14.1 The report shall include the following: proximately 25 %. A suitable mechanical or hy- 14. I. I Original dimensions of the test speci- draulic device may be used to facilitate assem- men including the original thickness, fo, bling and disassembling the test fixture. 14.1.2 Percentage compression of the speci12.3 Test Time and Temperature-Choose a men actually employed, suitable temperature and time for the compres- 14.1.3 Thickness of the test specimen 30 min sion set, depending upon the conditions of the after removal from the clamp, ti, expected service. In comparative tests, use iden- 14. I .4 Type of test specimen used, together tical temperature and test periods. It is suggested with the time and temperature of test, that the test temperature be chosen from those 14. I .5 Whether or not the surfaces of the com- listed in Recommended Practice D 1349. Sug- pression device are lubricated. If they are, what gested test periods are 22 h and 70 h. The test type lubrication was used, specimen shall be at room temperature when 14. I .6 Compression set, expressed as a per- inserted in the compression device. Place the centage of the original deflection, assembled compression device in the oven within 14. I .7 Method used (Method B), and

¶D 395

¶14.1.8 Ntinlth.. :pecimens tested. A testing, therefore the precision for Method A 15. Precision' and b. is derived from four laboratories.

¶15.4 The precision results are given in Tables

¶15.1 These precision ,,atements have been I and 2. prepared in accordance with Practice D 3040-8I. 15.5 Bias-In test method statistical termi- Please refer to this practice for terminology and nology, bias is the difference between an average other testing and statistical concepts. test value and the reference or true test property

¶15.2 Prepared test specimens of two rubbers, value. Reference values do not exist for this test Methods A and B, were supplied to five labora- method since the value or level of the test p r o p tones. These were tested in duplicate each day erty is exclusively defined by the test method. on two separate testing days. A test result, there- Bias, therefore, cannot be determined. fore, is the average of two test specimens, for both Methods A and B. 'Supporting data arc available fmm ASTM H e a d q m r s .

¶15.3 One laboratory did not run the Method RequestRRD-11-1138.

TABLE I LQC Pmisioa Data Comprearion Set-Method A Within Laboratories Among Laboralones Material Mean Level - S cv S CV A 1.73(I) 0.0500 0.0277 0.190 0.1096 B 26.1 0.898 0.0336 2.37 0.0908 Avcrage or Pooled 0.636 0.0308 I .68I 0.1006 Values Repcatabilily Reproducibility Standard Deviation, (9" 0.636 1.743 Callicient or Variation. ( C V ) 0.0308 0.103 Least Significant Di!Terena. (LSD)*' 8.8 I 29.1 I

¶A An averagc value. the value of S varies with mean level.

¶.LSD based on 95 Iconfidence level: two results are considered significantly different If their difference. expressed as a percentage ortheir avcragc. exceeds the stated p e m n l value.

¶CThe LSD values are relative percent. that is, a percent of the 'percent" values used to measure the tested PmWrtY.

TABLE 2 LQC Precision D.1. Colnprrssh Set-Melhod 6 Within Laboratories Among laboratones Material Mean Level S cv S cv A 13.7 (A) 0.591 0.0420 1.543 0.113 B 52.8 0.567 0.01 10 5.924 0.112

Average or Pooled 0.579 0.OM7 4.329 0.1124 valuei Repeatability Repmducibilily Standard Deviation. (W 0.579 4.348 Coetlicient or Variation. ( C V ) 0.0307 0.1 14 Lean Significant Difference. (LSD)*E 8.7 Sb 32.4 I

¶An average value, the value oTS varies with mean level.

¶LSO b a d on 95 A oonfdence level: two results are considered significantly different if lhetr dimerence. expresvd as a percentage oftheir average, exceeds the stated percent value.

¶The LSD values are relative percent. that is. a percent of the 'percent" values used to measure the tested property.

¶D 395

FIG. I Device for Compreash Sef Test, Usins Chlibnted Spring lmdinll, Method A

FIG. 3 Device for C o m p ~ i u asct Test Under Consmat DellectioqMC(M B

¶The American Societyfor Testingand Materials rakes no position respfrring the v d i d i y orany pamu ri&s asserted in connection with any irem mentionedin this standard. Users ojrhis srandard are expressly advised thru dormninruion dthe volidiry oJany such patent rights. and the risk of infiingement of such rights. are entirely their own tesfmnsibiliry.

¶This standard is subject to revision at any rime by the responsible technical committee and musr be r e v i d everyjve ypan and if nor revised, eirher reapproved or wirhdrawn. Your commenrs are invited either far revision ofthis sran&rd or for additional standards and should be addressed to ASTM Headquarters. Your comments will receive c a r & / cansideration ar a meering d t h e responsible technical committee. which you may attend. Uyou/eel that your comments have nm received a b i r hearing you should make your views known to the ASTM Committee on Standards, I916 Race SI.. Philadeldria. Pa. 19/03.

376

¶VZI-B

¶To: WArro~iatoAdministrator for Spaco ?light now: 1QS/Irr Davidr SUUECT: Car. to Car. and Worrlo to Car0 "0" ling Soa1 Erorlon

¶?roblomr

¶As a rorult o f tho problomr balni Incurrod durlng f3ight on both CIS. to car0 ond noxxlo to oaro 0" rial oroilon. nr. Hamb and I riritod X I l C on July 11, 1011, to discuss this Irruo with L t h projoct and SID porronnol. lollowing oro romo important factors concoralae thoro problom: A. IIorr10 to C8ro aF?In# ororlom T h o luvo boom twolro (12) Inrtrncor darine flight whoro thoro haw boon SOW prlury "0" rIn8 ororlon. In on. rpociflc cmo thoro war also ororios of tho rocondary "0" ria# 80.1. thoro woro tw (2) priur "0" sIa8 roalr that n r o hoat rffoctod (no ororion) u d t w o (a! casos In which root blow by tho priury moa1r. Tho p r i w rurpoct as tho CIUSO for tho ororion on tho primary "0" ring roalr Is tho typo of putty urod. It lr lhiokol*r position thot during arrembly. loak chock. or Ignltloa. Lolo Can k formod throu h tho utty whlch Inltirtor "0" ring ororlon duo t o jotting offoct. it is Important to noto that aftor STS-10. tho unufacturor of tho putty wont out of borinorr and now putty sanufocturot wor coatrrctod. n o BOW potty is bollorod to k IOFI rurcoptiblo to onrironmontal offoctr such as molrturo whlch u k o r tha putty m o m tacky. n o r 0 aro rarlour options bring coarldorod rucb as romoval of putty. roryln tho putty conflguratlon to rowat tho jotti.8 offoct. IJSO of putty amdo by a Canadian &aaufrcturor which Imcludor arbortor, and vrriour combisatton of putty ond grraro. n o r m 1 analysis andlor torts at. andorway to ~ r r o r rthoso optlrr. Thlokol 1s rorlorrly c o n ~ i d ~ r i rtho dolotIom of utt om tho PC- S roaalo/caro jolrt rlrco thoy folIaro tho utty 1s tio pTIW * caaro o f tho ororion. A docIrIoa om t h i s cKanSo t o planad to k n u d o t h i s wok. I h o w rmrorratlonr about dola# It coaridorina t k r ~ g n ~ f ~ c a mof 91-r iirtma tm quolityina t L me tor c ot l ~ fllgbt.

377

¶It is 1. ortrnt to mot0 thot tho cruso rnd offoct o f tho putt rrrlor. fboro rro romo WFC orromol rho aro sot convincod tirt tbo bolo# in tho putty rro t!o rourco o f tho problom but fool that i t may bo 8 rovar$o offoct in that tbo hot grror u bo lorking through tho roal and causing tho bolo track la tgo putty. Conrldoring tho fact that thrro doorn't appoar to bo 8 rrlidatad rorolutlon 8 r to tar offoct of putty, I would cortrlnly euerrlen tlr r l & w i a tmmarrng 1% on ipt-5.

¶Thrro h a w boon f f v o ( I ) oc~urroncosduring flight whoro thors ras primary f i o l d joint "0" ring ororion. Thcro vas one car. whore tho rocondar "0" rln ras hoar affoctod rith no ororion. Tho ororion vlth tn, field folnt primary "0" rlngr is conrldorod b romo t o - b o moro critical than tho norrlo joint duo t o tho fact tgot during tho prorruro build up on tho p r i u r y "0" rin tho unprorrurirod fiold joint rocondrry rorl unroatr &a0 to f o h t rot t ion. Tho problom rlth tho unroating of tho rocondary "0" ring durlag joint rotation ha8 botn known for uito norno t h o . In ordor t o ollmlnatr thir roblom on tho FXC !iold joints capturo foaturo vas drslgnod uh!ch provontr tho ~ocondriyrorl from lifting off. Durin our dircurrlonr on this isrua rith MSFC, 8n rctlon war arsigno! for tho8 to idontlfy tho timing rrrociatod with tho unseatlag of tho rocondary '*O" ring and tho m 4 t i n # of tbo primary "0" rln durin rotation. How long it t a k a tho recondary "0" rfng to fift off during rotatlon and rbon in tho rerruro cyclo it lifts mro koy frctorr in tho dotor8inrtion of P t r criticality. Tho proront C O ~ ~ O I I SIs

¶U ~that if tho rimmry "0" ria roatr durln ignltion, 8nd rubroquontly fri!r, tho unroatod rocondrry ''0" rfng will not rorvo Its intrndod purporo as r rodundont seal. Hovovor, rodundrnc door oxlrt during tbo Ignition cyclo, bhich tho most cri?icaI t h o . * t 1s rocommondod thrt ro rrrrn#o for WSFC t o provido an ovorrll brl0fing to you on tho SRll "0" rings, including friluro hlrtoty, currant status, and options for corrocting tho problo~r.

¶6 4 - 4 2 0 0 - 86 - 1 3

378

¶VII-c

379

¶2 .

380

¶VIII-A

¶NASA

¶STS St-L

. PROGRAM DIRLCTIVE

¶G,ff 1.;'a.

381

¶b.

¶c.

¶d.

¶P Q t E . 06 , ___

¶.

¶VIII-B

¶THR-15380

, I . . . , . . I . . . . .. . . . . . .

¶STS-51L (STS-33 )

¶SOLID ROCKET flOTOR (SRH-251, .., . ,

¶FLIGIIT READIt!ESS ,REVIEH

., . . .I , . .. . . .. .. . I . ., . .. . .. . .. . . . . . . . . .. . .

¶. . . .. . . 0

t '-, . I . '. .:. . . ., . .. , * '. .. . . . . *. .. . . . . .⁸⁸ Ibid. Ibid. ' 0 bid. I 1bid. Morton Thiokol, "Program Plan, Protection of Space Shuttle SRM Primary Seals," TWR- 14359,May 4, 1984. s Ibid. Discussions with Allan McDonald and Carver Kennedy, Thiokol (Wasatch Operations), Brigham City, Utah,, September 4, 1986. . . . . . . .. .. .. . . . . . " , . '. .. .. iI . . . ...... . . . .. ... w

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¶. .. . 11"DECE)IBER1985 . . I

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'. . L I ....⁴⁴ Rogers Commission Report, Volume 11, p. H-1. . . . . I :

WASATCII D I V I S I O N

' P.O. BOX 524'; RRIGIIAll C I T Y . ~ l ~ T A 8H 9 3 0 2 .(801) ,863-3531,

.o S I S - 6 l C (SIS-32) ( SRtl-24) PERFORMIICE

7.0 0 PROBLEM SUEIMARY

¶I

¶3.0 0 S T S - 5 1 1 (STS-33) (SRM-25) CllANGES

0 CllANGE SVIMARY

¶0 DESIGtI

0 . IIARDWARE CHANCIEOUT

0 PROCESS CllAN6ES 0 F IRST 1I tE CONF I GIIItAT I ON REUSED