·-•• -- • ••• •• • •• _r- • ·- ·• ·---- ·-• ·- 1 -• • 883413 103 CONFIRMED TO BE UNCLASSIFIED DOE OFFICE OF CLASSIFICATION D C Hix AU-63 DATE 9 30 14 J M de MantmoWn 7118 w lL Boa Jand 7182 - J'ebl'IW 7 _1981 -- ·- · ABSTRACT - Thia repc r preaenta the reaalta of tile bmtaUp Uon a- id aulJall of the af'ety upecta of the Mk 39 Mod 2 bamb1 mnlved ID tile B-530 c rull 981 Greeuboro Nr rtb Carolina Thia hmtaUpt an waa condueted b7 Sandla Corporat' cm aubnqueut _to • prelbr dnary inveaUptlcn al tbe ot tile a_rub eae • · •' ••• I ' ·_ · •· ····· ·• - ' · 1 J STIUBVTJQ · -·· _ - · ·· 1-ll 38A • I K F J erttotd ALO l'or _ ____ ____ _ _ _- _ ---------- Bn a · A W Betta • DIIA LASL Attia Mas ac W LllL AUD J POiter TechAlcal Ubt'VJ' mu · Attn Col · QoJdealMq Storqe Dl'Wtalali da l'Jll7 S ety B '- · a c -nrmvuffng t fflc ' AFSWC or F CoL C B Stewart t Ji' lt ASA For -- _ ' • -• ' •-a•• · - _4 - · ••• -'- · 1' · •• · • • ·i · -J l'or ·· tin- · i' _ ' · -- · · - · · - t CoJ Striddaad Lt Ced Schuyler w Henderaon · · B Leaudes- 1300 B Fmdlay 1400 B Machen 2300 -· · --------------c - i 12 38A - R 13 38A - B 14 38A J 15 38A - A 18 38A - L A Hopldna 21'100 17 38A • G A Fowler 7000 18 38A - E B per 7100 19 3 • 7fi fittersm '1110 20 38A - E • Bvley '1118 21 38A - l£ w1 Jm fJ '1120 32 38A 4H S wlliion '1140 23 38A - D R Cotter 7180 24 38A- J M Olaon 7182 25 38A - s 'A M oore '1180 28 3U L E IAmJdn '1500 27 38A - w J Boward 8100 28 38A - L Gutierres 8140 · 29 38A - C Winter 8141 30 38A - M G Banclle 3411•2 31 38A - R K Smeltzer 3421-S 32 384 - W F Caratene 3423 33 SBA - A D Pepmueller aw 34-38 38A - R C Smelich 3488-1 - •· ' ' - _ _ -t _ · · ' #- 5 Thia report la not to be reproduced In whole or In P wltlmt written permlaalon by- tho of tbe orlglut1n1 depa rbrellt muaaer - t - ' _ · · _ · - - - · - · ·· - - -· J' • ' ·- ' · · ' · · · J - ·· ·_ ·_· - - • · - -r J ·- _ · llcUcn - W•ipoll Syateqi D tactlpUOll • ••• t B•HQ 4rcftff s o f Aaalj ot•• - • · ' ' ' ' ' ' - lnil f l B1 •-1 • S·I t _ - I ' '· ' _ • • • •• • _ 2 fot ajll Tra tectorj en ot•fr at Mo l# 3·· •• • •'f ''· - d 1 ---_ _' · _ · • ' ' •-' ·'i '_ · I - • r - ·- ' ' Blocki Diap-am MJc aJ 1'4 11'ltb'AL'r 111 '' · le ' - _ · ' _1 ·1 ' • • T ecto1 t ·•• W--lf f a 1 ot •n 1 2 · l•T •c 10 ace W No 1 ' - ' ••e TJI l lecqve f W--JfO 2 ' ' - ' a ' inter'nil Vte r of u _m 04 MC-na · 9 - • Vie Mq f f W - •• • ' ' eel • 'WUhiT ' q ou Bet ' U MC R - t •- l o 2 · ANKLYSIS OF THE SAFETY ASPECTS OF THE MK 39 MOD 2 BOMBS INVOLVED IN a-no CRASH NEAR GREENSBORO NOl TH CAR OLtNA ·- Introduction On J lnuary 24 1961 a B-52O carrying two Mk 39 Mod 2 bombs broke up 1n mid-a lr and crashed near Seymour-Johnson AFB North Carolina During the mid-air b akup or the alrcrart the weapons separated Crom' the aircraft The parachute or the weapon 1n the aft bomb bay hereinafter c alled weapon No 1 deployed and ln its retarded trajectory the wc spon impacted approximately l mile short of the impact point of the major section of the aircraft The parachi tes of the weapon in the forward bomb bay hereinafter called weapon No 2 did not deploy and the weapon impacted in the free-ra1 condition approx - mately 1500 feet past the impact point or the major porti ll'l or the aircraft fuselage An AEC team consisting or members from ALO LASL and Sandia Corporation went to the scene or the crash to _assist in the preliminary investigation or the weapons involved in the crash A report of the accident and the on-site investigation is contained 1n SCOR 108-61 • Subsequently 1ome com nenta or weapon No 2 were ret11rned to Sandia Corporation ror further analysis Detailed post-morti 1n o these components along with information Crom the preliminary investigation bas made possible a determination of the status of the weapons during the crash Summary o Results Anoly is or the compone11t3 and rep rts from the crew or the aircraft indicate that none or the pre• arming functions required to release a live nuclear weapon had been performed prior to the time thr weapon separat d from the ni re raft However some event normally requiring crew action must have occi red mechanically due to aircraft breakup It is known that the sating pins were extracted from the Blach generator actuation rods and the rods themselves ' 'ere extracted from the pullout assembly On both weapons the fuzing sequences were initiated but due to the fact that the aircraft-controlled Arm Safe switch was in the safe condition at time of release neither weapon armed This in itself would have prevented a nuclear explosion When the MC-772 Arm Safe Switch or weapcm No 2 was recovered there was an lildication that the switch might have been armed Pest-mortem results Indicated that the indicator drum had rotated to the ARM position but that the switch contacts ln _ lll probability never actually closed in the ARM pos• lon The rotation of the indicator drwn was undoubtedly due to the impact shock however the impact shoc I also damaged the switch contacts·to the extent that there was no continuity through the switch in elther the ARM or SAFE position • •· Weapon System Description B-52O Aircraft Tho B-52O has two bomb bays each capable or carrying one Mk 39 weapon The weapons are separately controlled through two T-249 Aircraft Monitor and Control units The arming circuita to the weapons are interlocked by the T-380 Readiness Switch The T-380 under the aircraft commander's control must be placed in the ready position and the appropriate T-249 must be plac ed In the air or lf'C Wld position in order to prearm either weapon The aircraft ls also equipped with lanyards from the bomb bays to the crew compartment t allow extraction or sating pins during rught• SRO 5 • _ -------_ _ _ _ _ _ _ _ _ _ •- __ _ _ _ _ _ _ ____ _ _ - --•tc a1r I I --- Th -e-a-- 1r-c r_af_t-ay-stem also Incorporates a solenoid-ope rated lock which either allows the weapon to Jl freet• all trajector1 or lnlUatea parachute deployment at release The static line from the parachute • attached to th solenoid lock ar d when-the lock la operated the parachute deploys at release DOE M 39 Mod 2 Weapon b 3 The Mki39 Mod 2 is capable of either Cree-Call or completely retarded trajectories It has a dual1 ch annel ttmer-a omeid and bnpac t• lred fuzln s stem Tl e riring sign Lt 1 iM liaJleriY ed mm cio m ---- _ o a crush aw tcl A Cl ' of the weapon In a ddition there la a trajectory-arming feature In this wel pon tihlch funclloi s after separatlon troi n Uie a rcratt be ore arming is allowed the weapon must unde -go • pressure change corresponding to 1500 feet at sea level ---- 81 cLJ nC system is shown 1n_n m fL llt orrn e · ruzi It singlet channel block diagram or t h •tn Jectory t t • s s h Detailed operation is as fe l1ovis Prior to release the MC-7 2 e Switch controlled from the T-2 9 must boa placed in the MM position and the sating pins in tho Blach generator rods must be removed by the lanyar4 extendinJ to the crew compartment At release ot the weapon rods are extractc d Crom the Blach generator assembly which in turn delivers an Initiation algnal to the low' voltage battery and the safe•separatlon timer R Qda also actuate the pullout valve ass'imbly causing the valve to close and sealing a re erence pressure in one chamber of the P C -832 DW'erentlal Presroximatel 28 volts • sur-e Switch Five to ei ht secands after ·release the thermal batter volta e rises to ___ _ _ _ _ _ _ _ _ __ When the weapon has Callen the required vertical distanee e i eren pre u1ure slV1tr h contacts close passing battery current through the MC-7'12 to the MC-788 High Voltage Sating Switch · Upon receipt or this current the MC-788 ls operated connecting t '1e output of the high-voltage ermal battery to the X-unit When the timer contacts close 42 sec onds after release initiation power is delivered to the high-voltage thermal battery The high-voltage thermal battery comes up to voltage 1 to 2 secon ds later The X•unit is charged and voltage is appUeti to the trigger circuit At impact the crush switch • loees grounding one 1 1 ide of a firing transformer in the trigger 'cit i ult The other slde or the transformer k connected Le the 28-volt low voltage therm ll battery Uu-ough·a fuse When the crush swl ch closes a pulse ls de lvered to the transformer causing a signal t be trans itted to the gap a rltch and dlscharlflng the X-unil Each chAMel of the crush switch firing circuit is fused '· L'l the event at premature operation or or e channel th 1t fuse will clear in a few millitseconds to allow'subaequent o eration o the oppo· site channel · b 3 ITAR 6 Deleted Deleted f ·• T-380 READINESS SWITCH IN READY POSITION T-249 CONTROL POWER SWITCH ON T-249 SELECTOR SWITCH IN ARMED POSmON ARMING MC-772 AfUII SAFE SWITCH ' LANYARDS PULLED _REMOVING SAFING PINS AT RELEASE MC-845 GENERATOR OPERATES ACTIVATING MC-640 THERMAL BATTERY AND STARTING MC-543 TIMER PILOT PARA- CHUTE DEPLOYED PULLOUT PLUGS REMOVED AND VALVES IN PRESSURE SWITCH SYSTEM CLOSED 28-FOOT PARACHUTE DEPLOYED 100-FOOT PARAc roTE DEPLOYED---i- - n MC-832 BAROSWITCH CLOSES ARMING THE MC-'188 SAFING SWITCH MC-543 TIMER CLOSES AT 42 SECONDS MC-641 THERMAL BATrERY ACTIVATED ----CHARGING X-UNIT RELEASE ALTITU 3500 TO ft'lOO FEE' BOMB NOSE CRUSHED ON IMPACT COMPLETING FIRING cmCUIT BOMB DETONATES - t Flgure 2 Normal Trajectory Sequence or Mk 39 Mod 2 RES SECR MC-832 DlCCerential P re Switch -C-832 contains four individual barometric elements Aiie' elements or this switch ar r-'ii t to operate when a differential pressure equivalent to approximately 30 mm Hg ls ai plled to the element In the weapon one chamber oC each element is open to ambient atmospheric pressure The opposite chamber is open to ambient pressure through a mechanically actuated valve Pullout Valve Assembly -- The pullout valve assembly r ontains rods which when extrs ' ted from the weapon at release close to seal the ambient pressure in one of the chambers of each or the differential pressure-switch elements Prior to operation the rods are retained in the weapon assembly by shear pins -J 'J · -- MC-772 Arm Safe Switch -- The MC-772 is a solenoid-operated rotary switch with detents so that if a pulse of power is·delivered to the solenoid the switch will step from SAFE to ARM or Crom ARM to SAFE The solenoid operates through an axial air gap The axial force is translated to rotational motion b r balls which ride in grooves in an inclined plane A drum attached to the rotary switch which indicates the ARM or SAFE condition can be observed through _windows in th- side or the housing There is an awcillary lever at the end or the switch assembly which will allow manual move ment of the switch from the MM to the SAFE position but not vice versa MC-788 High-Voltage Safing Switch -- The MC-788 is also a solenoid-operated switch The solenoid device is similar to that used in the MC-772 however there is no detent action to cause the switch to remnin in the ARM position Continuous power must be applied to the solenoid in order to keep the contacts closed in the ARM position MC-641 High-Voltage Thermal-Battep Pack -- uc m _- uiuaUU1 nm MC-583 or MC-818 thermal batteries Theatteries are comected in a ser es-parallel arrRngement with five in each series leg The complete aesembly provides a total voltage of 2500 volts to charge the X-unit Individual batteries are initiated when energy is delivered to their n iatclles through an isolation transformer MC-787 Trigger Circuit -- The MC-787 contains tw o krytron tubes which are supplied plate voltage from the htgh-voltage thermal battery through a divider network Pul transformers are connected in the grid circuits of these tubes o that when the transformer is pulsed the tubes conduct and deliver firing pulse to the X-unit gap a Crush Nose Switch - - The nose or the weapon is arranged so as to close an electrical circuit'when it is deformed inwardly Spaced behind the nose cap are six metal plates each covering a 60-dP gree sector of the weapons cross section Alternate _plates are connected in parallel to one trigger-circuit grid transformer through a fuse When the nose cap is deformed at impact contact is made with sharp pr-ojections on the switch plates completing the circuits and pl lsing the transforr -1ers ALT 197 pr-ovides additional sa ing by introducing Arm Sale switch contacts between the Bisch generator output and the low-voltage thermal battery matches In this ALT the MC-1288 Arm Safe switch is installed - 1 •in place of the MC-772 In addition tu th contacts in lines presently controlled by the MC-772 MC-1288 contacts in the Bisch line insure that the thermal battery wW not be operated if the weapon is released 1n the safe condition A block diagram of the system with ALT 197 is shown 1n Figuz-r 1 3 When th $ ALT is accomplished it is considered that the system ls adequately safe for alert flying without sating pins installed in the pullout rods ALT 193 is a modi i ation to provide compatibility with the aircraft clip•in suspension system by adapting the Bisch and viuve pullout connections to the clip-in supporting structure The lanyard arrangement for removing sating pins in fli ht cannot be used with ALT 193 For this· reason ALT 197 must be performed at the same time or prior to completion ol ALT 193 · · · • •· - • Deleted Observers reported that this weapon separated from the aircraft 70 0-9000 feet above terrain Fully retarded it impacted in th_e near-vertical position penetrated the earth approximately 18 inches and remained in IUI upright position with the r ichute hanging in adjacent trees The weapon was intact with only minor damage and it was possible to azu lyze the components at the scene It was found that the sating •-- •Bisch generator rods had been extracted and the pullout valves had operated The low-voltage thermal battery pack had been initiated and the timer had run down The differential pressure switch contacts were closE d and the high-voltage thermal battery pack had been initiated The MC-772 Arm Sale Switch and the MC-788 Satlng Switch were in the SAFE positions The gas reservoir valve had not been actuated and the gas remained in the reserv Jir The crush nose assembly was deformed and it can be assumed that it supplied a fire signal at impac The probable trajectory sequence is shown in Figure 4 · r · From examinatio of the MC-845 Bisch generator assembly it appears that the pullout rods were extracted in the normal fashion There was no scoring or other physical damage to the assembly which would indicate that any unusual Corces had been applied Also since the holes for the safing pins we1•e not in any way damaged it must be assumed that the saf'ing pins were extracted prior to separation ot' the weapon from the rack It is known that the aircraft broke up in mid-air and impacted the earth in several pieces over a wide area One intact saf'ing pin and a portion of the lanyard were recovered indicating that the pin must have been removed at the time the B sch rods were pulled It is believed that the lanyards attachej to the safing pin in this weapon caused the si r ing pins to be extracted during the breakup of the aircraft This weapon appeared to have a completely normal retard d trajectory therefore it is assumed tha the parachute solenoid locking device had been operatE d securing the parachute static line to the aircraft structure From the information available on this weapon it is ap arent that all components behaved in the normal manner that would be expected i the bomb were released from the aircraft wit i the T- 49 in the safe conditinn Under these conditions arming of the we pon is prevented by the MC-772 and the MC-788 Analysis of Weapon No 2 This weapon probably separated from the aircraft between 2000 and 5000 feet above terrain It impacted in a free-fRll trajectory The tail of the weapon was buried approximately 12 feet below the surface The structure of the weapon was severely damaged and there was considerable breakup due to the ir 1pact conditions however no HE explosion resulted Components of the fuzing system which are ler ated in the aft portion of the weapon Just ahe9 d of the parachute see Figure 5 were recovered relativPly intact however the extent of the damage did not readily allow complete evaluation at the scene The gas reservoir was essentially undamaged The actuator had not been initiated and the gas remained in the res rvoir The MC-·772 Arm Sat'e Switch appeared to be intact when recovered from the unit and the indir ator drum indicated that the switch was in the ARM position It was therefore requested that this component along with other omponents of the fuzing system be returned to Sandia Corporation for iartber analysis Post-mortem results of various c 1mponents at Sandia indicated that the fuzing sequence had been initiated si nilarly to weapon No 1 The B sch generator had been actuated ca using the low-voltage thermal battery to be activated and the timer to be started The pullout valves had been closed and subsequently the differential pressure switch contacts had closed The timer had not completed its timing cycle but had stopped after approximately 12 seconds of operation as a result of the deformation which occurred at impact therefore the high-voltage t hermal battery had not been actuated 'I • i ' · 11 · l· a• BEFORE BREAKl AT 5EPARA TION T-380 READINESS SWITCH IN SAFE POSITION T-249 CONTROL POWER SWITCH OFF T-249 IN SAFE POSITION MC-772 ARM SAFE MC-845 GENERATOR OPERA1 ED ACTIVATING MC-840 THERMAL BATTERY AND STARTING MC-543 TIMER PILOT PARACHUTE DE- SWITCH SAFE LANYARDS NOT PULLED PLOYED PULLOUT PLUGS RE- MOVED AND VALVES IN PRESSURE SWITCH SYSTEM CLOSED AT AIRCRAFT BREAKUP LANYARDS EXTR CTED SAFING PINS 100-FOOT PARACHUTE DEPLOYED ESTIMATED ALTITUDE AT SEPARATION 7000 TO 9000 FEET MC-832 BAl OSWITCH CLOSED MC-543 TIMER CLOSED AT 42 SECONDS MC-041 TIIERMAL BATTERY ACTIVATED '----- BO MB NOSE CRUSHED AT IMPACT WEAPON DID NOT FIRE BECAUSE WEAPON VAS NOT ARMED Figure 4 Probable Trajectory Sequence Weapon No 1 l t• DOE b 3 Deleted Figure Cutaway f Mk a Mod 2 DOE Deleted b 3 __ _ _ _ _ _ _ _ _ _ _ _ _ __ The probable trajectory sequence of this weapon is shown in Figure 6 As L 1 indicator drum of the MC-772 di i indicate that the shcl t of this switch w in the ARM position after impact c etailed examination of this swit h was conducted Photographs oC the switch as it appeared when recovered are shown in Figure 7 The An indication can be seen in the window At the time it was recovered there was no continuity through any contscts of this switch Upon disassembly of this switch it 'was found that the statior ary members of the switch contacts had been physically displaced at impact approximately 1 4 inch in the direction ol travel The direction of impact force is in the opposite direction that would be expected to operate the solenoid of this switch However because of the mounting co 'lfiguration of the switch see Figure 5 there s good reason to believe that a severe rebound shock would occur after impact which could cause the solenoid to rotate the switch shaft Fro n the evidence a- ail able it must be concluded that the MC-772 was 1n the SAFE position until time or impact It is quite prob11ble that the contacts of this switch never operatad to the ARM position The circumatanct s or this weap 'ln up until the time or impact are very much the same as those or weapon No exr ept that there was insufficient time between separation or the weapon from the aircraft structure u ntil impact for the timer to operate consequently the high-voltage battery was nc-t initiated - · Detailed post-mortem results on various cumponents recovered Crom this llnit n re available in separate repo -ts They are summarized here to provide completeness to this report MC-772 Arm Safe Switch -- mectrical check11 of the circuits of the switch revealed that there wa11 no c ontinuity through any of the switch circuits in either the ARM or SAFE condition Disassembly of this switc 1 revealed that the structure on vhich the switr h is mounted internal to the housing was severely deformed in the direction of travel or the weapon at im Jact A comparison o Figures 8 and 9 shows that the plastic wafe1·s which support the stationary contacts of the switch roke from their supporting posts and were displaced away from the swi tch rotor contacts The indicator drum remained attached to the switch rotor and the rotor was displaced to the A RM position MC-640 Low-yo1tage Thermal Battery Pack -- The MC-473 batteries were removed from the battery pack Scorching of materials around the batteries indicated that they had been activated The batteries were opened and it was found that they hac l been activated by elc·ctrical energy to the matches and that ower·was probably available during the trajectory sequence •• MC-543 Timer - - The case 011 the MC-543 was severely distorted The cover plate had been deformed so as lo jam the gears on both timer channels Figure 10 shows a comparison of this timer with a normal re·set timer The position of the mechanism indicated that the timer had bi en sat at 42 seconds and had run approximately 12 seconds after initiation Examination of the actuators indicated that th y h11d been fired electrically · MC-641 High-Voltage Thermal Battery Pack -- Each or the ten MC-583 Thermal Batteries was removed from the battery pack and opened It was found that none or these batteries had been activated at any time The squib switches used to indicate whether the battery had received an initiation pulse were also examined and it was found that they had not been activated l ' 'Q • • -· MC-845 Bisch Generator -- The Bisch generator rods were found to have been extracted There was no evidence of any Wlusual scoring or other damage which would indicate that the rods were extracted in other than a normal Cashion The holes through which the sating pins are installed appeared normal and it is believed that the sating pins were extracted before separation of the weapon Crom the rack M£ 88 High•Voltye Sating Switch -- The switch was crushed and severely distorted The r1tationary· and movable contacts were smashed together with their plastic supporting members Although the connectors had been ripped loose from the housing electrical checks at the ends of the broken leads showed continuity in the SAFI' pr sition These checka and ihe examination of the switch parts would indicate tr at u e switch was in the SAFE position at time or impact 14 M f ·' • i 1 AT SEPARATION · BEFORE BREAKUP MC-845 GEHERATOR OPERATED ACTIVATING MC-640 111ERMAL BATTERY AND STARTING MC-543 TIMER PILOT PARACHUTE DEPLDYED PULLvUT PLUGS REMOVED AND VALVES IN PRESSURE SWITCH SYSTEM CLOSED T-380 READINESS SWITCH N SAFE POSITION T-249 CONTROL POWER 3WITCH OFF T-249 IN SAFE POSITION MC-772 ARM SAFE SWITCH SAFE LANYARDS NOT PULLED AT AIRCRAFT BREAKUP LANYARDS EXTRACTED SAFING PINS ---- ------ ---- - -- -- m 0 m -t MC-832 BAROSWITCH CLOSED - - - - - BOMB NO 'E CRUSHED AT IMPACT TIMER STOPPED AT 12 SECONDS WEAPON DID NOT FIRE BECAUSE WEAPON WAS NOT ARMED CII Figure 6 Probable Trajectory Sequence Weapon No 2 ESTIMATED ALTITUDE AT SEPARATION 2000 TO 5000 FEET b 3 ITAR b 3 ITAR Figure 7 MC-772 Recovered from Weapon No 2 • 16 ·- - • • b 3 ITAR • • 1_ • • p -• ·• • • b 3 ITAR 1· ' ' ' 18' •' -- · · · ·v -' ' ' • ' • b 3 ITAR • ' - · · i 11 1 i · ' l o •• r 1 ared to have· b eta bliUated ConclaalGaa Deleted aeq11_ 8 r ubii Jt_c c i'1r- t '1» _ntJntUadon oi - •·· · 2 The Arm $a e switch preventecl'a nuclear detanatloc •lJi· the•e reapona aa it waa desl ned to do• • ·-· · · - • ' ' '' ' · · '• • J SI nee lt _1a undesirable haye the fu e p er iq pl ' a tlw ed eir- apt when a ll rele@• l' Ml t 1 de i T 191 should be lnc 1 t rated aa raptdlt• poaaible JD au oda of the Mk 15 38 fainf lf Wbich are used in the airborne alflrt •· · · · · •i1Wf41- '· ---· • '· - ·c • ' i l- ·-·- -- j ' ' ' ' · • · -- - l · I _' · · ·t