17 April 1945 JA O c o 55 5' r --9 Z TO Major General L R Groves From R Subject l c Tolman or -Ult - f t4 llllt oob Program for Trinity Test Purpose ilafiil tt t i nsm rttaf · · any miinner i o' _- oY th6sc iv Teat· Thia briet' description ot the teahDical aapeota or the program ror the proposed T1nit7 •t ia made 1n reaponae to your recent request • t p air1e 1J c- -- ·· • -· - • · ploaion nuolear bomb subatantialJ y 1d ant1oal with the r1rat model a which are being dea1gned t oc abat uae In contrast to the oaae or the gun aaaemb1y type bomb auch a proot t1r1ng 1a regarded aa neoeaa r7 in tbe case or an 1 mploaian bomb 1n Vin or the present unaTo14able unoerta1nt1ea •• to the beh Yiour ot the implosion prooeaa tr· tbe nuclear re- aet1on set ott by implosion doea not re1111lt 1n • · aatiataot017 high order nuclear exploaion the teat will be important 1n d1agnoa1Dg the oauao ot the trouble am in auggaa _ -J ng oeaA rJ' mods rtoauona - 1Jl' ·deatgg · ---t t - tba 1·rm lear ' ez- ·- • pl osion '-doee take plue high ordu · fibe 'teat •iU· b• · 1 mpor t 1n determ1n1ng the extent o blaat -d•uge th a eztent the to xio rad1oaot1ve e t tecta and tbe nature or behaviour the upper air to be expeoted in mU 1ta r7 uae or t be weapon 2 General Character or the Test The teat is being carried out at an isolated location Trin1t7 with autt1c1ent area under m111tarJ' oontrol and gu ud • t o provide the diatanc•• neoeaa07 tor malc1 ng the desired -•m a rementa tor prav1 di Dg p ro toOtion ra the peraormel comuating· tbe teats - and tor aaaur 11Jg J he·· ·aarety ott Snb•bitanta -or- t he •glon I t la zq op1 D1ou that proper attenti on 1B being g iven 'to these que st1 ona The i esu lts of t ho Trim ty 11r1ng will or course be correlated with the studios or the implosion process being made at Loa Alamos and also with the existing body or information as to the er tecta produced both by the experimental and accidental detonation or various amounts or ordlnaey high explosives I DECLASSIFIED 1 Authority - __ I J tJ 'v2 30 D·3S 1 ' ' · Memo to Genern l Groves -2- 27 April 1945 · rn addition vs rious small son le tests o the ef 'ects of explos1oil8 are being mde both a t Los Alamos and Trinity to prove in experimental methods and to settle specific points For example tests on wter rormation have already been made at Trinity to determine the e ' fects of the particul ar soil structure at that l oaation ' 'he first l rge sea le test at Trinity which 1s now scheduled for 5 Hay 1945 will consist in the tiring of 100 tons or ordinary h1gh e losive stacked 1n the form or an octagonal cylinder approxi mately 18 feet high on the platrorm or a 20 root to1f8r he obarge will consist pr1martly o some 51590 boxes each containing 50 lba • or Tll' aUpplemented at' aix po1nta by boxea o r compoai ticm B •JDOIJg wbich rlll be speci al boxea prepared to reoe1 ve the tetryl boost era which •ill initiate tbl explosion P1pea plaatio tubillg o appropriate composition will be inserted hori ntally into the pile in a regular arra y into which will be introduced a radioactive tracer mixtul e consisting or a dissolved sl ug from Ran ord ' hia preliminary teat will make it poaaibl e- - to lllllko • '-NNkll Uc• t rial •a t' - all J1181Unll'8J11BUta 1 -to · - · be employed in the 'inaJ test except those having to·do with the special cbaraater or a rmcl ear expl oaion The final princi pal test at Trinity ia now scheduled or It 111 consist in the static t'1i-ing ot an 1m- 4 JUly 1946 plos1 on bomb subatantially 1dent1ca1 with those being designed tor incorporation in -the tat ·m an• and or combat use _ The bolbb will be 9 ' the ao-oallod Cbriaty type 'The present expectation 1s that the cbanoea ror suooesa tul-high order detonation Will be su t icientl 7 grea ao that the bomb should be exploded in the open aJ r without at tempt ·t o recover · aot1ve mator1a1 in caae or a ·t'1za1e Tlds · Wi ll be -clone on the ·J l att'orm ot' · a ate•l • tower 100 t'e·e t high - this diatance · above·· ground ·eoal1ng· in· accordance with the cube root la• w1 th the distance above ground of 29 reet to the center ot' the 100 ton charge I _J Authority N tJ 22 30 D DECLASSIFIED •- ' · ll8mo to General Groves 17 April 1945 A11 plans for measurements are k•iJl made on the basis I t later eattDll tea as to the probability o£ aucceastul detonation make 1t neoess11r7 to f'lre 1na14a •Jumbo • to allow £or recov r7 in case or a 1zzle soma or the proposed meallllr'emmta will noi be teaaible · or such an open air tiring at al1 and moat o tbelll - 1n can b'gb orde r detonation ia aobievad - 11111 be muoh leaa 1med1atel 7 appllcabl e tor pi-edieting the e tt'eota to be exp oted 1n actual combat use tr011 explosion 1n open air a Prograa ot lleaauremem an4 Obaenation PftllU'J' aeaam-ea me 8114 obeenaUOD • to be taken tbe uploa1on _ be- pc uped und• fouzt maizl baadinga 1D oOOl'dano• 111 th the or nenta llh1ah ooour am muat be atucU etl atte tbe lmploaon or tba btgb exploaiva 1a a W ' beae head5ngam 7 be talr ezl aa · The ·at the tilla •eciueno• 1 Beb Tioma ot th8 Imploa1on $ 4 DaMp Bt eota PJto4l»e4 ovwall Behaviour or tba Bxploaioa amt 1ta At1 e rreota ' be behaviour or tAe Smplo S 011 •111 be •tudlecl bJ' de1 end Dlng the tlme 1ntaval • 1 mi ob the de1iomtora f tbe b1gll apJ oa re ac the t1me 1 Dterval beween the aoid on ot thea• delcmatozia am ti 1D1tlat1cm ot tba nuoleu naotion and· tt poul'ble obut Dillg· a ooapl eu· - or -the·' rlae ot DIIOl NI' ao'1 v1t y art 1zd tia'1oa - -- lf bll •IIOUl1' m- oleu- enog released 11111 be meanre4 b7 vuJ oaa -tboda or dete DSnfng tbe mmber or rmc1ear 1 uiom llbiab have taken pl aoe '1'he atu4J' or ti damage e tt'eota a d wU1 iDvol ve - ure1181d a ot blast pressure 1D- air aid ·ot cllaplaoeamta aD4 en tar 1'orJD t1on 1n 8U'th ll8 on N 11 bebanaur am Arter erreota wm be wtnJ7 ataMU 84 b7 pbotognpb1o 8Dd apeotzitopapbio obaenaticma Tbe-apee1 1o and ob__ _- t1ona 1'all1ng 11nder the aboYe J»adinga wU1 be 4eaar1bed 1D 1110N dau U ill later aeotlallll • •• r• •• - • • • - i1i ' • •• •• • ' • t • - '• •• •• • • • · _ · 1'he i eraoa 1 OU'J71Da mt the-_ aboft PZ'OSftllll· - 111 be working 1D ahelt-ea bullt-at··tbree' a'-1 iona• loaate4 10 000 7U'da from the aero or f'1r1ng point• t he aouth weat and 'f be ahe1tera are r4 a'trotg enough oonat ruc t10Jl to Memo to General Groves 17 April 1945 protect against· t l agment damage even il Jumbo ia used and the blast pressure at 10 9 000 rds 1a expeoted to have dropped to a safe t1gure o t 0 3 lba per square inoh i'ha prevaillDg winds to be expected are tram a south•waat direot1 on and the nearest tOWD to the east ts acroaa a mountain range 28 mil ea in a s011theaaterly direotion so that ·pro- tection trom toxio radioactive et taots should be good both ror scs1ent1 t1o pasonnal and looal 1nbab1tanta • • Receivillg 1nstrumenta tor d1 tftt nn tnea o meaaU1 8JIIIUl1 will be located at var1oua diatanoea from the 1aro point aD4 111 ll transmit th•1 a1goala eleavloal 17 bJ' wire to tbe acmth west and north 10 000 JU4 ■tat1ona In-ad41 t1on a pela 1'roa oertain preaaun gaugea wUJ be tnmmd ttecl by radio ftring •111 be aontrolle4 trO'III the south 10 000 JIIK ·ata1 10Jl llbS ch ia merest to the baae camp Aboui twelve men will be neacle4 at tbe south 10 000 ya1'4 station to- meuu remenb OD implosion and nucl ear behaviour about twelve lll8Jl at the weat 10 000 yU'4 stat1on _tor controlling photographlc and apedr aoopic e xpoavea tor wJdng obaan tlona on·cooperatlng 11'• 1 '- • pl a-• aztd OD l l 8 o a 1 pbarso reaa •· am J A N■dlzwaa ta r · sample oollect1on and about f'Uteen man at the ·north 10 000 yard at at1on ror meaaurezanu · cm air blast and t photo- •·-·· papbic obeel Vllt1 ona • IR add1 t1 on to· the primarJ' aurementa aDd obaervat oaa manticmed above meteorlogloal obaena tS ona will be nao••IIU'J' to study be torebam the beba o w1Dia c v-er the JIIOUP 1 aSna tb the eaat to toreoaat the weather aa the proposed tir1Dg U me approaches and to atud7 tba •teorol og1oal pbeD01811 aa pnduoed by the uploaicm s ttaeU Puthemore atta 'the ez p1oa1cn -··or ·radloao'1n oontamlmUon wSl 1 be made 1n the neigbbaJllhood or 1al8 tiring potnt and in the lllallllw ta1na and terri torJ' to the eaas suah wauramenta will be meded t the protection or tha ao1ent1ats 1D the work to be undertaken after the exploaicm an4 or-the proteot1011 or· loca1 1nbab1tanta It la now ezpeota4 tbat the beat tlme ta tiring will be at about an hour bat'ore sunrlaa at a time when 111114 valooltiea are l ow • and when pbotograpbio and apeovo- · paph1o obaervatlcma will not be d1atube4 by direot ii-11nl1gbt Such an early 1'1r1ng hom9 wiU also provide a long daytime 1n which o t'ficiala 1n charge o t health protection can aeom e eftouat1on rrom ocmtud nated • • U thS • proves neoeaa ZT on iba baaia o t' their rad 1oaot1ve -■urementa 4 organization ror car171ng out the Program The soient1r 10 am technica1 aapec a of the prQgram out 1 1ned above are Ullder the genera 1 direction ot Dr K T Bainbridge as Head 0£ the Trinity Projeo't The work umer h1m i vi SECRET r- DECUSSWm D l Authority NM P 2 o OJ t DECLASSIFIED Authorizy I J tJ S 2 30 03 -s- Memo to Genel'al Groves 17 April 1945 is organized 1nto six divisions TR-1 to TR-6 under aix Gl't up Leaders and he 1a assiat ed ln pJ anning and c r'l'J 1Dg out the work by a number or comul tani a and by of'1 1cara ot the Post ' he organisation chart of tha proJeot aa ot the preaen't date 1a approxtmtel7 as t'ollawa Qrganization mart or it T • Ba1nbr14ge V• W•1aakopr the Trinitz Project ·Bead •• J Penne1 Oonaultant on heorJ' Consultant OD Damage L w oariaoa Conaul tant on Expected mad or Consal tan1 on atZ'uotm-ea · Ena G T Re lda J e l d e r ·s ··tteraha• Capt s p Daval oa Lt B C Buah Lt 11 A 'l'q'lor -· f ---· J 11 W1llSew · _ r·•• - - i--·If-'·' --Di l z- m-1 Conamltant on Damage Sat'et ' COllll1t'8e Repreaentatlve c o BngSne• De't at Tr1n1 o U Det at C 'lr tn1tJ' 11llitll17 seov1 '7 abrd cal Senioea - _-· · bipii7 ·-- _ _ • _ -·- r2ndpg J oold D8 telepbom comamioat1on Jlanba IG-4 a J van Guart Bad1o ea m1oati ona am tollc 1r-up Air Blaaia and BU'th Sboak aoiio iiau gauges Pleao gaugePapR·gntp• BJaat IJIIP' l• BZO•aa blaat Yel 001- BIIJ 'th dlaplaomant aa4 U'Ater O opbonea and aei■l908 pba m-a ft-4 l L B 1'1 laan ·2• R ' J 4E B llooD B Wllacm B WilllB Sepe JP B llooll - ·iB - L lDlluao1l f L JI BeapelMDn · · J • Bubbard Lt C D CUrh1 a -· j - TR-6 J E Jla ok TR-6 B Wal dam With team 7 111th team from· 0-11 51a1 oa1 urementa onaulGiii natena1 t7 · prmpt gUllllll nya Intanait- delayed neutPODa Inteuait7 of delayed g r - r JB Intena1tJ' o clelaya4 s - N'J'II Aaeay r4 69 oomenlon · BZteat r4 oom•w1mt1 on lfeteoro sci-SA on cornei- ref'lectora Jlot1 on or bal l of f'lre PhotograpbY and spectroscop7 Airborne Measurements trom o-a ' E RET _ _ · Memo to General Groves r1 -6- April 1945 his organization chart gives only a partial pio ture o£ the responsibillt ies that will have to be assumed by the nan listed and by others who·will be aaaoc1ated 'l'be picture 11111 be supplemented by more detailed descriptions or the ditterent measurements in later sectiom In add1t 1on to the operating organization as described 1n the above chart appropriate co mm1 tteae have been set up ror glv1ng pr l1mmr - approval to nn mea emanta or dil'rerent kinda tba t •'J' be proposed tor inclusion in tihe program and a aatu- comm1ttee baa been set tor g1V1ng final approval •1th due ocma14erat1on to the program aa a whole time aohe4ul e spaoe and 1d r8 aYa1lab1e priority possible duplication poaaibl e- fial 4 1nted'BNDM eto '1'ba exten o the pl'OgNJll la also- llm l ted b7 oef U i aga 111posecl bJ' the D1reotor on tbe T1IJllber or man-ah op-hours adl O'IIINl both 1D the Mab1ne and eleotrord o abop■• ra ·tbe 1'rinit7 projeot •• •1' now turn o a brief' but mon cleta1le4 4eaor1pt1on am the dttterent maaauremanta obaenat10DS that have been aooepa6 1ti l a t be-a o f a- t'a - IP888Dti daA a • 5 ot Behav laur •·- '· · the Imp1os1on Deterlld Dlt1on or the obaraotv ot t be implosion wb1 ch 1eada ·1 o the mo1ear up1osion 1a ot the greatest 1mportanoe ftla atucl7 or 1llp oa1ona baa however turmd ou1 to be 'h'l 'J' d 1t't'1oult even at Ndl»e4 aoal e and 1n tba abaenoe ot nuclear ateru l In the ' rnn1 ty teat onl7 the toll owing meaaureaenta oan be prot ta l7 • • • - ' - t· · ' • • · -_ _ ··Dei ona- SfMJltanell•·· 'fba aundal'd eJ eoR'Old o appaiiatua deviiopii for u ·ti nna men drop teau to de- tend Da tba t1mtng or a t onat-o'ra 1naerted 1mo •d'UldilQ'• bM cka will be adapted tor the TnD11 J' taa1 • apparatus will FOVide a Nool'd or the ts 1ntar a1 batw'41@1 • r1r1z2g or the tlrat and last ' uaed to detoza the high •Jr§t1oa1ve It auoceaa tul tbia 1 1 -· interval gh91 114 not be lcmgei- than L It - a oona14eral l7 longer ti me lm enal ooaura an aaaJJD9tr oal 111pl oalm and a nuclear exploaioA or reduced err1cienoy are to be ozpeoA4 W A lf1g1Dbotballl and L Greiaen will be reapon • - - apparat u uect aal tbe a tbad aauremen 1a ·-apeo1J•5'o- be · aucoeaa tul beo•va- ot the standard character of •pppatua A 1• am Nuc1ear Act1 on Ume Int ervai between the ftme Iuterval Between Da'tcma tor ••8 1Ntlllfmi -will be nacie of SECRET f- I DECLASSIFIED Authority N t - 5 2 30 • 03' - - _ 17 April 1945 Memo to General Groves · action of' the detonators and the reception o the first · gamma ra7s comiDg__trom the nuclear l eaction Thia ti me 1nterva1 ahould be By comparing the a ct 'u a i va1ue £oWld w1 th that whichltould be predicted or a successfu1 implosion combined with a aucceasf'ul initiation or tbe nuc1ear reaction at the right time - it ma be possible to di-aw conc1ua1ons as to the actual behaviour of the 1mp1os1on process and or the be17ll1mra-pol on1um initia- tor which produ cea the burat or neutrons that starts the nu- clear reaction 'rhis measurement will be made by R R Wilson and baa a high ahanae ror suoceaa tul performance but ma7 be d1 tt1cul t to calibrate c • Determ1Dat1on or the Buol ear Reaction Arter the imcJ ear reaot oii a liiitia£aa the ln£anaiti the react1 on 1 e the rate at which neutrons are being 'onaed or at whiah t1aaioDa are ooOUl ring 11 7 be aet proportional to a tam ot the tO Jll trr • where ck •Y be oalled the aot1Y1t7 ot the 49 core and t 1a the time arter 1n1 t1at1on he activity 6- depends ·on the denaity or tbe 49 core and 1a a or · - ee 1 - D tli1 - Mlz 1 mm - BeDO• i ir tl•- naot1oa J a 1n1t1atact while the core ·1a still being oompreasecl by the imp1os1on cJ - will be ·leas tbaJl its maximum poaldb1e va1ue and will 1ncreaae 1'1th t1Ja un t11 the e tt'eots DDClear re- aot1on ·tbem••lvea start to roroe the ocre • • Ir the reaattoa h 1D1t1atec1 ·at the opt i Jlma inatan ot w rtn1■ demity cJ - 11111 have ita medDIDP val ue and ld ll N•1n auba'8Dt1al 17 conatant until aecban ioal rect a bom the naclear reao•1cm take hold An4 it the reaot1 ou la 1D1t1ate4 Arter tbe opti1mnm 1Dstan tJ will be laea than 1ts mex1JIIDI· posa1b1a val a am 11111 decrease w1ta tiaa Purthermore 1 t -1• be notecl that · - will 1-· · f'1tc a- tha ftlue 1t otbeJi'ld aa- woa14 ha••• by USJIIBtr J· o Saploai ou which leads to poor· aoapresa Jm or b7 a mx1 ag or·act v• 1111ter1a1 with tamper HeDo• a deter·m1Datioa or d U a tw MltiOD or tbla would gift a Vfll 7 pollerhi method or atm71Dg the imploaJ on and 1ta lil 1olear oonnquenoea SUch a clatermination will be a ver'7 dll t1cult matter but will be undertaken by B R Wilson For tb 18 purpose he will aet up to meaaure aeconde17 gamma raya produoe4 aa a oonsaquenae or the absorption or neutzons 1n the outer l ye o the tub 11o7 tllapt0- •·1JJC•·· 1 t bu been sbolnl aD theoretical unda that thetr 1ntenat 7 r111 ·be· proport 1cma1 to th• 1ntenait7 o the naoloar raaot 1on during the short period be- fore maob•n1ca1 eft'ea ta from the rwclear axp1oa1on take hold The great dir1 '1cu1t7 or the experimeni is comiected with the low 1Dt t7 of the gamma rays alJd t h e short time intarva1 I · ·· _ during which the change in--°'- -maat be i-ollowed Tbls makes--1t neoeaaary to employ retlned IIBtboda 1nvo1v1ng electron mult1pl1ers and time d1scr1mJnat1ng circuits 5 -·'1 · SECRET · - -DECLASSIFIED · - l Aut hmilyl Jt 'D 73003 w memo to General Groves -a- 17 Apr111945 Olr1ng to the great d1tr1culty of the complete experiment a set-up will also be made b7 Wilson to determine_ only a single value tor duril Jg the com-ae of the reaction Alao a set-up proposed by Roaai for determiai g a single val ue of - by measuring the er feet or gamma ray ionization on the tl'anam1 as10D ot radar waves intba neighborhood of the bomb may be mt de by Rad1 at1on Laboratory personnel U this can be arranged The probab1llt7 or coapl ete aucoeaa tor the proposed exporl menta rar datormintng tJ_ is not high but their 1mporta 7ica is very great 6 · truol Enerp Be1•sed j · The releaae or nuc1aar •rm a- 1a the w1D t mcU01l of llhlob tbia occurs 1a or •tbod• tor ctelenld n1ng·tbe IIJIIOUDt or naolear eners - released 11111 be uaed Bo one the bomb and the e rnc1ems - wit h pr1Jlar importama snera1 theae la cfftain to pr-ovide aoourate reaulta bu t the 1ntepretat1on -ot tbs1r combined results oan be importan't I• aonveraion of 49 to P1aa1on Products l J' dJ iaecv deiW ca £lon or the ex£en£ A relativa- ot the nuclear reaot1 on could be made by a successful asa J' the amoUDta of unconverted 49 and conve2 ted 49 - i e fission prod uots - in 1-be products of the expl oa1on Thia Will be undertaken by H L Anderson by radio-ohemtcal anal 7a1a or soil 1n the neigbborhood SECR ET f - I f ECLASSiFiED i Authority N 6 P 2 30 OJ i 17 April 1945 · Memo to General Groves of the exp1osion ' 'he work is made di ficult by the b1ghl7 toxic contamination or the soil from which samples must be collected It 1s also mado d1 t '1cult by uncertainties as to distribution but preliminary studies on the d1atribut1on or tracer material in the 100 ton shot •111 help 1n this connection It is probab1e tba t useful results will be obtained by tbia method 7 Damage Etfeota ProDm64 A oona1derabl8 mmber or measurements ror determim J Jg tha damage to be expeotecl ti-om the elp loa1on are possible SOIia or 'tbaae are·at a aut 1o1entq atamlud 1se4 aharaot er·ao·tba• uaeful reai1ta are to be expected The maasuremen ta a oonoenred wJ th the etreota ot air blast and oE eai-th shook to1 Blllfr will be de·terained at various distances to ge ratii ror cHrra claaaea or daaage ' 'he lat-ter 111 ll be 1mp t in cheold Dg the merg or the • los1on but 1'111 not be or much millt817 lmp oe • P1 •soren••·· on · --- -A r-- · Bl aa u l'reaaure a Grouml Level b'om - • preaaure in tbi ai r biiat will Se measured •• a or time at various dlatancea b-om the explosion ua1ng atam·U'd p ezo gauge technique 'fhe pico gauges wU1 pz-o b17 have to be comtruDte4 quartz rather than or t01D-1MtlSna as ia mere OODPRDD 1J1 Aaariaan prao'tio•• aime tbe tourJlllll 1De guagea have been tolmll to be b1ghl7 aana1t1ve to tempaatlare nb•ns••• a property llhioh does not interfere 111 th thell' vndezttntter use or uae tor air blaat waves ot abort dun ti would be troubloacma tor t he blut wave 1oxig daraUoD 1'roa an 8DOnlalla •ion QUIIJ lb gmagea m 7 bav A o - _o 1aSm4 h'oa BDsltm4• _·Pluo gage -uuraamu--are--·tha ruponaDU11 r·-- · Gr R •· L Wal'lllnt • • o m·· Blaat Preaaure a't Oround·Leve1 t iroa Oond onaer Simiir WIIUl UIIDU of biuE preaaure illl a ob m4 b m coDdanaez gaug•a tbat have bean 4eve1opocl ail Ort by Dumond and P aq gauges are urange4 t o trwad t their 1ntormat1on b7 trequ9D07 modu1at1on ot a radio a1gnal be•• Thia 'Ork 1a the reaponaibll1t7 oE - w c Br1gh · Blast Preaam-ea at around Level ri-om BZoeaa · Vel 0013 · mi vitooiij of- a bliai wave tbzouifi_·ai la peat than t '- ot ordlnazT- ·aoum by an excess _amoamt ·mtall· 1iJoNuea w1 th the pressure dU'f erenoe across the blast front Bame suf' t cientl7 accurate meaaurenmnts of velocit7 can be used to measure pressure Suah Dl8a urements will be made by B B Baz-scbalJ using crd1 m ry microphones The velocity or or41nary · · --I f - --------- -· DECLASSIFIED J i l I Autherity N tJ P2 30 03 I 11 I Memo ta General Groves l 7 Apri1 l 945 -10- · soUDd w1 ll be determined just before the main explosion by shooting a small charge or high e xplosive Measm-ements or excess vellcit ' will a1so be nade under tbs direction or J E Mack by tba photography on a moving film or flash bombs placed at difrerent diat anees from the explosion and set otr oy blast operated switches Peak Pressure at Ground Level ram Paper·o il5es id ti Se estlm ted ditferent distances by tbe uae ot the Aberdeen type of paper gauge 1n which paper oovel'iDg hol ea ot varioua a1zea is exposed to rupture by the blast Alumtmm toil will be used d a 1'l 18 peupresaure in the bliat wave 1Datea4 o paper ainoa th1a baa been ouml to give maoh DION nproduoibl a rosu1ta ' 'be work 1a tba reapomd billtJ' of c J Boogtarp · •• Blaa't Imlao at GrouDi Level trom P1aton Aotil on PluiC Jliiauremon a o tl ie iif egrai a preaaure-El mii ao on of the l aat will be determ1md b7 tb8 movement ot a piston wb10h 1'orcea fluid through a small bol e his work 1s the Naponaib 111 o t - _ - JorgenaOD•·· •-·- ·- · _ _ • -· --• - -- - - _ - c ' ·' · • · •·· • -·• · - t ·- Blast- Pressure at Bipr Levela f'rom Comena 6 1 S•t nam • irc u • 1 tft r b on pa aol mtea bom a ·plane to give •• ta or prasave ppecl at b1gber levels above groum hla mtaaurement 1a ot iJlpar- tpo• on eooUJlt or the ef'1'eot o the llaah wave on preaaure as a 1 mot1on or height ot expl oaive am _height or reoe1V1ng point 111 tJ'heae measurements m1ah are belng developed tor ua• uie under t u 41» eoUoD or B waldnn OOJ■ il d eli'VU' f ' • •• • -t · ··- -· --- --· _ ' · • • • • Barth Shock he veloo1'7 cd earth movemema prod uoeclo7 £he e xpioalon w tll be wauftd ldth tba help or convertotl geophonea permanent earth d1aplaoementa •111 be measured With tba ba1p ot auitable stakes driven in the ground and crater dimensions will be DBaaured d1reotly beae rmure- menta u-e the reapona1b1llt7 or 11 •• Boughton and J R Coon It 1a ••t 1 ma ted by Ensign Reynolds tbat at a height ot 100 teet ODl 7 about one per cant of the eJlN'U the explosion may be expected to go into crata or•t1on EVen so the main shot should produce a crater 275 reet aoroaa end 80 feet deep J etend z la t1on ot earth movements in the oaae or the preliminary 100 ton shot will be vory important i n dea1gn1ng apparatus and apparatus shelters ror the maJ n shot a OVera l l Behaviour or the Expl oai on and 1ta A t ter Er 'ecta In accordance Yd th the latest version coming from tho d1 tr1cu1t theoret1oa1 studies wblch have to be made the overall I-·eRc T DECLASSIFIED - I Authority hJ tJ 2 30 D3 I • · _ 1 7 April 1 945 -ll - · Memo to Genernl Groves behaviour of the exolosion n nd its at'ter e ff'eots are now expected to have the 'ollowing character The energy emitted by the fission process oroduoos m chaniotl expansions wbich start a rt er- initiation These expansions Eri ng the ener miasion subs tantial ly tQ an end 9 or neutrons emitted The shock wave which accompanies e expaoaions passes ou ward from the sU ' face or tho sphere or 49 and heats up the sorround1ngs to a very high temperature At about 50 miaroseoonda this gives a sgiiere o f about 10 meters radius at a· tempera ture o f 250 000 • 1'h1s hot apti re 'ball or fire expa nda rapidly end at about 40- m1lllseoonda b s reached a radius or 1 50 matera a douait7 io-6 and a temperature or- about 20 000° '1'ba ball or 'ire n l l Ja ep 1-ta shape and poa1ticm r-or several seconds Becaus• or ita low denai t -- it 1DOVea s1owly upward and atarta c11aintegrat1ng by tarbul ent m x1ng A ter about a m1 nute ·it will have completed disintegration at a height or l to 2 kilometers o material that •u in the sphen will however contimla to rise and f 1 na l ly mushroom out at a height or about 5 kilometers · DariJJg the• t1rat one-tent n aeao ad • the balU ·of · t1 re · ia ·expeo ted · to give an average 1llum1 nat1on equal to ·that 0£ the sun and at the end two seoonda to have fallen to OJ 1e tonth th1a intensity 'l'he behaviour tl ie bal l or '1re and at'ter etteota will be roll owed by photograpbic and spectrographic obaervations carried out bJ' s E Jl Ck and hia group Bny thaae oSsel VB tiom should be sucaeaatu 1 • iz -iSbaJ r Behaviour and Path · tm Ball Paa oameraa • a ldtoheii oamera and a hcimi movie oamara will be used tar rollow111g tba be baviour tbe ball of f1rc •• P1re - · - b Radi ation and TSD rature or Bal l or Fire Hilger speotrographs a Bausch andmb spectrograph a 35 GD movie camera •1th filters a eiwa ·camera with photo cell s and thermopiles with galvanometers will be used or analysing the radi ation 'rom the ball o 'ire and determining its temperature or E • Behaviour d Mach 1in v e and Air Vel oc i ty Hot Col umn Aer o mapping cameru lrl 11 be used f or obta liilng a space - t i me plot or the behaviour or the hot c oll ll Dl and i ts f'inal mus hrooming out Observa t i oI18 on the Mach wave whiah is expected I n the neighborhood of the explosion wi 11 be rra de by photographing t he appearance or a RET 1 DECLASSIFIED -7 f uthority N tJ 27 30 D •• C I•· · 'St CR c f Remo to General Groves 17 April 1945 -12- · · detonati Dg prima cord hUDg i'rom a sui tably placed balloon 'llhen the branches or tbe lfach wave i-ss aver the primaoorci 1ta intensity should increase Furthermore the -motion or tbe primacord should give intor m1tion as to the velocity or air in ita neigbborhood 9 Meteorological Obaervati OJll • Aa alread7 mentioned in addition to tha primal7 obaervationa •teorologica1 obaarvat10Da and at 141ea will be needa4 the behaviour or wi ma over the mountaina to tho east and tor forecasting a suitable tlme ror the shot to avoid bad attar er teota and ollow1 ng -teorolog1ca1 erreota or the a xploaicm Por tina work • • Babbard and Lt curtia 11111 be iron dad 1r1 th a ttel4 bal l ooD aet tor theodolite obaenat4 ona rad1o aoDde■• and a SCB•68 radar aet w1tb tor datermim ng ror- oornw renectora £or attachment to bal locma 10 Beal th- Control n • l eenn 11111 be·· pzt0Tided···11d th appustam·• needed · · · ·· - 1D comeot1on wltb hea1th control both 1D local am remote areaa Parthia pm-poae he 'd ll ba'n a portable alpha c l e ail' aamplara b portable alpba partiole a1r fllten c l ortable gamma r-s atera detem1n1ng doa- 1n t be range 0 001 to o os Boemgena per 8 bom-8 d portable meters ror 4oau 1D the nelgbbori lood of' 10 Jloen1Spm per 8 holirs am f Ndio-equippe4 oars ror omnm1 1 1ng the utent or con- - • •t tam net tOD toun4 · 11 - - 3 latU1oat1on and Propoaia tor tbe hop J he progr• or exper1ment a on daaoribe4 above at r1rat Bight uDduJ 7 elaborate op1n1on or tb cae aaaoo1atad tb8 ma 7 aema I ahare however the '111 t he progna tba th1a ia not I t the bomb tails to detomte b1gb order 1 will be neaea to ba ve extreme17 good 1n1'ora ti011 as to 1 ta aotual bebari our 1n orcler to introduce moclUloationa which will lead to a auooeaarul dea1gn The need tor a succeaatu1 implosion deaigD is a real on a 1nce we can no l onger regard the 1mploa1on tn a or bomb aa meral7 an alterna1 e to the gun tJpe _ since we now know that the latter c DDOt be uaerS •1th 49 as aotu l l J' manufactured at Hanford ' o aaaure the necesa r7 1ntora t1on a very cona1derab1e number measurements of lmploai ve and miclear bebarlour mu st be made aime nano of the poaa1b1e experiments 1s certain to be suocess tul or to prov1cle accurate results nnd the combined lnformation they provide will certa1 nly be needed · r DEC LASSIFttl ' JWl1lmitY NtfiY7 3DIB ·• • Memo to General Groves -13- 17 April 1945 I the bomb does detonate high order we shall still be interested in its implosive and nuclear behaviour but will now also be concerned for mil itary reasons with its damage and upper air e£tects Here too duplication ot experimental metb ods 1s needed to assure successful collectl on ot the needed data As a prognosis I agree with those associated with the program that the proposed tests will COJ le ott approximately on schedule and tba t a aui ticient number of the d1r£erent kinds or measurements will be success£ul to provide a good £ract1on or the necess r7 information Richard c Tolman V1oe-o 1rman _ N D R c atw _ • - DECJ ASSil'IED J Authority N '1 - - -I P 2 3 0 03q I - I -st CRs P