Operation Castle - Project 1.8, Report to the Scientific Director Dynamic Pressure Investigation

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*primary ob,-)ectlve of Project 1.8 was to evaluate dymmlc pressure_ iis a damage parameter. In sddition an attempt was made to determine the damage effect of the long positive phase &ration. A tot& bf 27 l/&ton trucks were exposed in %cts 3 and 6 of Operation CASTLE. The ground ranges were selected to obtain dynamic pressures comparable to those acting upon jeeps experiencing light to severe damage on Shot 10 of Operation UpsBoT-X3iCYTHOU~. The yield value realized on Shot 3 was too LOI+to give ~D,Y~ieprificmt results. For each degree of dmage sutained by the Jeeps irr Shot 6 aycamic pressures: were recorded which ue rslatedto meaeured results of Shot 6, CAS$& ccmpue favorably with that of Shot lo, UPSHOT-KWTECXJJ.Althbugh v+able data were obtained in Operation effect of the long positiveIp@$se on dmagc. The data obtained fro&d&-~~~on CRslzE were sufficient to evduate $mmic pressure aa a t+&ge permeter and also to determine l/&ton trucks for the set of c$‘ii&Aons as realized In Operation

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Thla report la oue of +.hereports presenting the results of the Operation CASTLEi,whlch:lncluded six test detonations. For readers interested in other pertinent test lnfonwtloa, reference Is made to WT-634, Sumnary of Weapons Mfects Tests, Military Effects R~grem. 'Th?.e8~ report includes the following information of possible general lntereet: (1) An o9eraL.i description of each detonation, Including yield, height of burtit,ground wro location, tlnw of detonation, ambient atmospheric-&Aditlous at detonation, etc., for the sir shots. (2) Dlscusslon of al_-project results. (3) A summary of’ each project Including objectlves..~ rcaults, (4) A coqlete llst-

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The purpoee of this report is to present the damage to @+-ton with we sustained In Shot 10 of Operation UPSHOT-KNOTHOLEmd with cond:tlone i--&edetermined to be suitable to Eeei the requirementsof the teet. :!I.$e.factoralnflvenclng participation were sufficient land dymmlc pressure and etatic overpresaure withlilthe vehicle stations vicinity. These gage8 were supplied by Project I.%. A jointeffort wa8 made by both project8 to utilize these gage8 in the xoct efficient manner in order that both projects could achieve the d.eeired objectivea. For description of the gage8 and detail8 of lnetrummtation, reference should be made to report prepared by Project 1.2b, during Operation CASTLE in the cap&tie8 noted: E. J. Bryant, ments for this project. Particular and grateful acknowledgement 18 @e to IV.8. Ethridge of Fistic Research Laboratories fc. the calctiatioqs,performed concerning the effect of positive dqzatlon on d8anage.ii Grateful appreciation is expreseed for the tcchn&l. .mmi8tance Appreciation is expreesed to personnel of Ta8k Unit 8:&d Tcek Unit 3 for the technical and document8zy photography they p$ov_lied. Also, grateful apprecfatlm is expreeeed to the w &ipport dlvislons, wlthcut which very llt'2e of project work could have bee&

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lev@:of 6.2, 12.3 and 24.5 psi overpressure levels -of 0.88, 3.28 and 11.78 psi dynsmic pressure l//+-ton trucks (side-on) for yields of wapon of Calculated displacements versus dynernio pk~s&e if l/&on trucks (side-on) for yields of weapon for yields of weapon of 24 KI (a-9) and 1 Xi (sur&e burst) Probability of damage versus ~~-~~place,jent’for*V1:ton” Surface bwst at sea level Station 180.10, before Shot 3, two l/4-t&i %rucks: 11 side-on, q gage to right of vehicles . i c ;

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-._. __- The primary objective was to evaluate the magnitude of dyntnic pressiirt$$s a dnmge parf*meter for.one tfle of target. In addition, an at&&t was made to dl.termine the dsmage effect of the long positive ;phase duration ?if the shock wave. l%&ber-information wns required to determine whether or not the damage cur&~ devised after Operation UPSHOT-KNOTHOLE(see Reference 1) are va.lid and also to extend the present knowledge cf the effects of atomic weapons on ordnance equipment. The exflsure of equipment In Operation CASTLEwas a consequence of the anomalous results obtained In UPSHCYT-KNOTHOLE,specifically, Shot 10 (.dee Referan& a). GA most of the equipment exposure tests in the past, the damage effects have been influenced by the presence of varying amounts cf dust~beh_lnd the shock and on some by the presence of both, a precursc$ shock wave and dust behind the precu~or R-lor to UPSHOT-KNOTHOLE:,$t&ic ovepressure was the parameter associated with damage. The as$n$~ion was made that other blast-wave pa!YUIIeterSwere uniquely relate&$+ the ststic overpressure. The data obtained in Srot 10 indicated that dy$&nLc pressures measured were higher by factors of three to four t&&s and possibly more than thr? dynamic pressures computed from meas&d overpressures using the to ordnance equipment on Shots 9 and 10, ~EWI’-K?KZ’H9~ did not correlate with measured overpressures. Danrige within the precursor zone (Shot 10) was excessive as compared t$_jdamage on Shot 9 at corresponding overpressure levels. Studies of we sustalned indicated that dynam!.c pressure is the slgniflcs@ parameter to be associated with damage. The maetudes of dynax@! pressure for The observed values of dyna .: pressure (see Refekence 2) and subsequent inv?st.lgations suggel :d that the damage aual;alned on Shot 10 may be attributed to dynamic pressures computed froman ideal overHugoniot relation. These assum& values of dynamic pressure 9ere used In the ensuing statistical analysis. The test in Operation I&STLF: was to prove or disprove the validity of the assumption c&e .&d to

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ascertain whether or not the prccumor will enhance dnmnpe, In view of the developert of high-yield veapons, It Is desirable to know the effect on damage of the positive duration so that the present ckmage criteria can be extended for range of weapons approxlmately from 0.1 KT up to and including 10 MT. There Is data available beyond a yield of approximately 60 KT or The study undertaken at Ballletlc Research Laboratories as tha_riqld of weapon Increases the pressure level for dmag4 idkireaees for drag sensitive targets.:

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;To:understand better the blast-wave parmeters associated with the dauij$e noted on Shot 10 of UPSHOT-KNOTHOLE,a total of 27 l/b-ton time--field expected to be that of a clas.sical shock wave. The ground ranges wcre:aelected to obtain dynamic pressures comparable to those acting upon jeeps experiencing light to.severe damage on Shot 10. In term, of value3 of side-on or static pressures, the region of interest for exposure of Jeeps was 6 to 2$1psi, based on the Ideal preseuredistance curve. -Within the vicinity of, each station, static and dynamic pressures were measured. Dynamic pressures were also caiculated from measured static preeauree using the following relation: The study of the effect of positive duration (see Appendix A) Indicated a lowering of pressure for &eclfic.,damage to drag-type targets for the large yield of weapons. FUzzher insight into this effect was to be obtained from results of t&&e tests. Damage evaluation of vehicles wa8 in &&ordance with the prucedures for UPSHOT-KNYl!HOLEI.That is, damaged l%&ns were clasrsified In terms of echelon of maintenance and time to r$@ore to combat use. A total of J.2 l/l-ton trucks were exposed on Shoi-3, Table 2.1 presents the vehicle ststions and the pressures expected frq-_the pressure range indicated in Table 2.1, damage to vehiclea wa$.:expected to be between moderate aria severe for any value of yield f%m2he estimated average to the estimated rnaxm. Placement of vehicles ir

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pressure r&~&e of interest correspo%dlng to the estimated minimum >$eld was a&$ considered. It was felt that if vehicles were placed In pressure r&&z& corresponding to the minlnnm yield and the actual yield exceeded t@?Xmaximumlimit, (this poeslbility existed since the yield values of k6& preceding shots were above the estimated average) vehicles would:bk~demollehed and no Information would be gained. On the other hand-if the lower 1-t of yield -were realized, the vehicles would not be damaged and, therefore, could be used for exposure in a subsequent shot. The field layout for Shot 3 is shown Because the shot that mfret suited the requirearente of this project was cancelled, parti.+patlon In Shot 6 was a move of desperation for @therIng sme u&fui data. Shot 6 was the only remaining shot with enough land area-ak&+ble whereby vehicles could be exposed within the pressure regions of Q&=est.

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In c&d& to be assured of mme data in Shot 6 the veM?le locations ran@d:from 5200 feet to i3,lOO feet. Severe and moderet? damage could be expected from the eetimated minlmm yield to the eetlmated maximirmyield. A tctal of 20 vehicles were exposed; GIX of these vehicles were recovered from Shot 3, the other elx were too ccntamfnated to be:transported. Two vehicles, one aide-on and one faceOE, were placed a% eagh station, instead of three per etatioa, to be certain there were sufficient station3 for complete coverage. The vehicle stations for.-Shot 6 are presented In Table 2.2 and the field layout is shown in Fig.- 2.2,

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flcant results. The highest pressure region In which vehicles were located was"7.443pel. At this pressure level dsmage to vehicles was light. T&Szdamage and the displacements are tabulated In Table B.i. The pressurd'vsl;uesmeasured at each vehicle station are shown In The pressure region to which vehicles were subjected ranged from 0.3 psi to 50 psi. Within-this range, dsmage varied frcm light to severe. MoRt of the vehicles were com1etel.v demolished. As In previous sn0c8~~:~-venlclcsIn side-on orientation eustsined more damage thm the veh$cles in face-on orientation. In the region placed face-on were not dasaaged~;~othe extent of the vehicles placed tioslof unu8ml damage was made-& Station i8O.20. The vehicle In face-on position was displaced 200 fe@; yet the only damage Incurred was to the two front wheels. The b$d$and steering colurm were Intact, so It my be assumed that this vehi@e_.?dIdnot roll. I?owever,It is sot certain whether the vehicle WRE plcke@up and hurled through the air, landi- on Its two front wheels, or whether the vehicle slid. Two vebrcles at Station MO.21 were blown into the lagoon, ahd dawe cculd not be evaluated. If the d&Age $.o@d be evaluated, this result would Cat be valid, since damage would @maIQf be different u the vehicles were hurled against a ground 8dface. Water wave8 did wa8h over the nearer Posit&8 to ground zero and possibly Inflicted additional damage to vehicles at t>ese station. Beyond Statlon 18O.19 there appeared to be no demagei$esultlngfrom to assume that water waves did not waoh over beyond ,%atlon.--f&2.19. measured BTe shown In Table 3.2 and plotted in mg8. 3.1 and_'3.2_,_ respectively. The plot 0r static preeeure data generally fIt8 thePredicted Pressure-distancecume, if a yield vaue 00 1.7 ~11Isi&&.

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c . The wave forms of the pressures measured arutthe general agreement betGe& the measured and calculated dynamic pressures :CdiCHted that the &ock wave of Shot 6 was nearly a claeelcsl shock wave. Although therb+aa sand in the blast wave, as evidenced by the vehicles being sandblatjt$d,there vae an Insufficient emounC of sand to alter appreciably the wave forms. It is believed that the contributionsto damage of vehiclea by dust was negligible. A~surprl_s$gly larger value of &tic pressure is required to cause ihe muv= de&ee of damage to vehicles placed face-on than for vehicles placed side-on. The value of dynamic pressure for lower limit of severe damage, (vehicle demolished) for face-on orientation was 12.1 psi. Unfortirnately,data were not availabia at Pressure levels less than 6.9 lpslto establish the lower 1:Lmitof severe Zcmage station for severe &&age__and the next station for moderate damage. Land area was not avail&&$ for plsccment of vehicles within this gap. HOLE) is given In Table 4.1 &&'shoxn In Figs. 4.1 and 4.2, In both sevtre, severe-moderate,moderate and light Jamage, respectively sustained by the Jeeps at the dist&es indicated. The age noted that item was still intact, but repalre~f!brimmcdlate combat USC-were euch as to require depot maintenance. Thik classificationmakes a distinction from severe dsmage whereby item Is completely dlamembered.:- to jeeps higher values of overpresbure were recorded on Shot 6 (CASTE) than on shot 10 (UPSHOT-mOTHoLE). The rela&?e qgpirison8 as shown in Fig. 4.1 Indicates that damage to jeeps on Shot :ld (WSEOT-KNOT~O~) ~~~t?sponds to the ideal overpressure-distancecu_z+W; However, since measurements of overpreexre were taken on both shotp and are reliable the damage to jeeps on Shot 10 as a function of th-e--idealoverpressure Aa mentioned In Section 1.2, damage to jeeps will bc16 hmctlon of dynamic pressure, but the magnitudes of cL;vnamicpresaurc for specific damage were in question. On Shot 6, CAS'I'ZE,measure!enta of

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dynamic pressure which are related to meamrcd ovcrprcssure oy ude of the Ranklne-Ru.go:*.lot relation, Equation 2.1 were recorded for each preesure aa ehown in Fig. 4.2 lndlcstcs the damage to jeeps on Shot 10 correlate better with the Ideal. dynazlc pressure than with the valuer measured by Sandla Corporation (GW Reference 4). The measured valuer of dpamic preeeure cn Shot 10 are questionable. !Chls comparison auggegte’that the probability cumce for we to jeeps (see Reference 1) T >*ld since Ideal dynamic precleures were uml for correlation m to:no$ to mention has been ma&e of the effect of positive duration on dsnage to jeeps. Intuitively, it cm be expected that If a rorce of eufflcleat magnitude to’cause motisa ‘sots on a target for lent force acting on the target for a shorter p&iod q$ time. The treatment c,Pthe effect of positive duration lo give&G Appendix A. It 18 shown that as the yield of vrqI;on lxreaees the; dy-4c presage of a vehicle are related. It can be expect& that the-larger riloplacanenteof a vehicle wlU cause greater we. Therefore, for the eemc level of da~~qc the aspanic preseure will be higher +om a low yield weapon than from a high yield weapon. In view of thla, the dynamic Rreeeure on Shot 10 couiLi have been higher than the Idealdynemlc pressure even though the comparison of the We made befrween Shot 6 srd Shot 10 implies that the Ideal dynamic pressure was :- c effective ti causing damage to ,jeepe on Shot 10. Althou& the data obtained in Operation C!A3l?LEvae valuable, it vas not enough to

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sewate the effect6 of dynamic pressure on damage to vehicles from the effect8 of positive duration on damage to vehfcles. It fol&~ therefore that the effect on d&m%geresulting from the long pooiti'fe duration is still to be determined and that the validity of the probability curves for dixrw3eas a function of ideal WC PreRaWe remain to be proven. It Is of interest to point out that if the damage to the jeep at 13,m Peet (Shot 6) wes severe then a mrt favorable comparison vould exiaf fpr dloplacement as well as ti.ge between Shot 6 (CASTLE) and She! :&Xi(UPSEOT-IUKVHOLE). The damage to the jeep at 13,090 feet could -$.~&,~a likely have been severe since during ttz transient time of the vehgcie being displaced the manner of impact of the vehicle with the g%und would itself be a probability _finctlon. The dlsplacement and :&&age then would be a?proxlmate!y eFmllar at 13,090 feet, Shot 6 and 2’rg5-_feet, Shot 10. In each case the vehicles were intact except that on:Shot 10, the vehicle required depot maintenance to restore to combat use which Is considered as severe-moderate damage ar.d on Shot 6, the vehicle required field maintenance which Is considered If t1.e coxnparlt~~nwas as indicated above the scaling from Shot 6 conditions to Shot 10 conditions for displacement of Jeep as well aa J/3*the damage to jeep would be,approxlmately h At each of two locatlor:8 on Shot 6 ezti Shot 10 the displacements were approximeteiy equal. “aat is at 9,OOO;$&Yt, Shot 6 and I.,920 feet, Shot 10, the displszements …