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"-'2 ' '' FINAL REPORTACCE$-.1.C)N NC&....... ....... .

.....T .... .. . ... ... . .. .. . . ._To hb$ r pea u uses for nuclear explosivesUNITED STATES ATOMIC ENERGY COMMISSION I PLOWSHARE PROGRAM

project SEDANNEVADA TEST SITE / JULY 6, 1962.I-I

0 10

Las Vegas

Close-in Air Blast from a Nuclear Eventin NTS Desert Alluvium

L. J. VortmanSANDIA CORPORATION ISSUED- OCTOBER 2, 1964"'I)T, UL:T_ N -S,T ET A

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LEGAL NOTICEThis report was prepared as an account of Government sponsored work. Neither the UnitedStates, nor the Commission, nor any person acting on behalf of the Commission:

A. Makes any warranty or representation, expressed or implied, with respect to the accu-racy, completeness, or usefulness of the information contained in this report, or that the useof any Information, apparatus, method, or process disclosed in this report may not infringeprivately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from theuse of any information, apparatus, method, or process disclosed in this report.

As used in the above, "person acting on behalf of the Commission" includes any em-ployee or contractor of the Commission, or employee of such contractor, to the extent thatsuch employee or contractor of the Commission, or employee of such contractor prepares,disseminates, or provides access to, any information pursuant to his employment or contractwith the Commission, or his employment with such contractor.

This report has been reproduced directly from the bestavailable copy.Printed in USA. Price $2.00. Available from the Clearing-house for Federal Scientific and Technical Information, Na-tional Bureau of Standards, U. S. Department of Commerce,Springfield, Va.

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NUCLEAR EXPLOSIONS - PEACEFUL APPLICATIONS

PROJECT SEDANPNE-211F

CLOSE-IN AIR BLAST FROM A NUCLEAR EVENT IN NTS DESERT ALLUVIUM

L. J. VORTMANSandia CorporationAlbuquerque, New Mexico

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ABSTRACTClose-in air blast from th e Sedan event was considerablygreater than expected on th e basis of previous measurements of blast

from nuclear events in basal t and from HE events in both basal t andalluvium. In spite of overranging of th e pressure gages, th e measure-ments permit derivation of a lower l imit of peak overpressure and anupper l imit on th e amount of blast suppression resulting from chargeburial. Comparison of Sedan blast suppression with that of previousburied HE and nuclear shots shows that Sedan blast suppression wa sconsiderably less than would have been predicted from HE shots atcomparable burst depths. Sedan peak overpressures were two to threetimes those of Stagecoach III at approximately th e same cube-rootsealed burial depth and four times those of Scooter or Buckboard 12(at or near the burial depth for maximum crater). The scaled totalpositive-phase impulse for Sedan was about th e same as those ofStagecoach III, Buckboard 12, and Scooter, while the scaled posit ive-phase duration was much shorter. Blast suppression factors, basedon peak overpressure and impulse, reflect th e above differences. Thedifferences may be due, in part at least, to a higher pressure in arelatively smaller cavity volume at th e time of venting for Sedanthan fo r th e HE shots.

ACKNOWLEDGMENTSThe author wishes to thank Mr. Ralph E. Reisler, Ballistic

Research Laboratories, for making th e blast measurements and reducingth e data for Project Sedan, and Mr. F. Shoemaker fo r coordinating th eproject in th e field.

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TABLE OF CONTENTS

PageCHAPTER 1 INTRODUCTION 5

1.1 Objective 51.2 Background 51.3 Instrumentation 13

CHAPTER 2 TEST RESULTS 152.1 Summary of Results 152.2 Peak Overpressure 152.3 Positive Phase 19

CHAPTER 3 DISCUSSION 213.1 Peak Overpressure 213.2 Positive-Phase Impulse 213.3 Positive-Phase Duration 213.4 Wave Shape 223.5 Blast Suppression by Charge Burial 243.6 Inferred Yield of Sedan 30

CHAPTER 4 CONCLUSIONS 37

REFERENCES 39

3-4

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CLOSE-IN AIR BLAST FROM A NUCLEAR EVENT IN NTS DESERT ALLUVIUM

CHAPTER I

INTRODUCTION

1.1 ObiectiveThe air-blast measurement program ha d as its objective th e

determination of the overpressure t ime-distance relat ionship atground level along a single blast line. The purpose of th e measure-ments was to determine th e extent of close-in blast suppression andto compare this suppression with those of other subsurface detona-t ions. The experiment extends blast observations from a 1/2 kilotonhigh-explosive (HE) charge (Project Scooter)' to a nuclear charge inalluvium with a yield of 100 kilotons. That is, Sedan was 200 timeslarger than any previous detonation a t a comparable burial depth.Data from this experiment yield some knowledge on th e differences inblast suppression between Sedan and the smaller shots but they do notindicate conclusively to what extent these differences should beattributed to differences in th e type of explosive (nuclear orchemical), differences in th e media, or differences in th e yield.

1.2 BackgroundTable 1.1 summarizes cratering experiments1- 8 using charges

larger than 256 pounds, both HE and nuclear, on which close-in air-blast measurements have been made; it includes charge weight, burstdepth, and th e source of information on these experiments. Table 1.2summarizes experiments with 256-pound charges. The conclusions fromthese earlier experiments were that :

a. Differences in peak overpressures of th e close-in airblast emanating from HE charges buried in differentmedia are small if they exist at a ll 6 . This con-clusion was based on a comparison of blast from

5

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Stagecoach and Buckboard charges of equal yield inalluvium and basalt, respectively. The peak wave inboth cases was that attributahle to the venting gases.The initial ground-shock-induced peak was considerablyless t~han the main peak and was slightly lower inalluvium than in basalt. Some media differences, how-ever, were noted for 256-pound charges at the deeperburst depths. 9

b. There were no detectible departures from cube-rootscaling of blast phenomena. 5' 6

Table 1.1 makes it clear that, based on cube-root scaling ofburst depth, the best comparisons fo r Sedan are the Stagecoach IIIHE shot and the Danny Boy nuclear event.* If WI/3.4 scaling is used,the comparisons should be with Scooter and Danny Boy; Sedan fallsnearly midway between Buckboard 12 and 13. On th e basis of over-burden scaling, the best comparison is with Stagecoach I, Buckboard13, and Scooter. Based on overburden scaling and density considera-tions, the best comparisons are with Buckboard 13, Stagecoach I, andDanny Boy. There has yet been no experimental evidence of departuresfrom cube-root scaling of air blast from subsurface bursts. Hence,only cube-root scaling will be considered in this paper.

In view of scaling uncertainties, greater emphasis is givenhere to the comparison with Scooter, since one may not wish to basethe comparison on the same scaled burst depth but rather on the factthat charges were at or very near the optimum burial depth, as bothScooter and Sedan presumably were. This choice avoids the dilemmawhich arises from the fact that crater dimensions, including burialdepth, scale as a power of yield or charge weight smaller than one-third, whereas no departures from cube-root scaling have beenobserved fo r air blast.

*Since the crater dimensions of subsurface bursts scale as apower of yield smaller than 1/3, one may wish to make a comparisonfo r air blast on the basis of other than cube-root scaling.

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0

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TABLE 1.2

ChargeShot Date Weight Medium DOB/WI/2 Reference101 6/28/52 256 Utah dry clay 1 9102A 7/6/52 1104 7/13/52 -. 13105 7/17/52 1106 7/19/52 .26107 8/20/52 0202 9/14/52 256 NT S alluvium 1203 9/19/52 .5204 10/4/52 .26205 10/8/52 .13206 10/11/52 0207 10/15/52 -. 13212 10/24/52 1.0301 9/15/53 256 California wet sand 0.5302 9/18/53 0.5304 9/23/53 0.75305 9/26/53 0.26306 10/8/53 0.13307 10/10/53 0308 10/13/53 -. 13311 10/20/53 256 California Moist Clay 0.5313 10/24/53 1 -0.13401 10/23/53 256 NTS alluvium 0.5402 10/26/53 0.75403 10/28/53 0.13404 10/30/53 1.0405 11/2/53 0.26406 11/4/53 0.5Sandia I 1/20/59 256 NTS alluvium 1 10

1/21/59 111/23/59 1.51/23/59 I21/24/59 2.51/26/59 2.51/27/59 3.0

8

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A typical blast waveform resulting from buried chemicalexplosions is shown in Figure l.la. Project Danny Boy held surprises"in that the air-blast waveform was of the type shown in Figure l.lb.For HE, the initial or ground-shock-induced peak was slightly higherin basalt (Buckboard 12) than in alluvium at the same cube-root-scaled depth (Scooter) (Figure 1.2). This is as one would expect fromthe differences in sonic velocity in the two media. However, theground-shock-induced pulse was higher fo r Stagecoach III-than forBuckboard 12 because of the shallower burial of the Stagecoach shot.The gas-venting pulse, however, was not greatly different between HEshots at equal scaled burial depths in the two media. The principaldifference was that the shock gas-venting wave from the shot in ,allu-vium decayed with distance more rapidly than that from the shot inbasalt.

FIRST WAVE SECOND WAVE(GROUND- SHOCK- INDUCED) (FROM VENTING GASES)

(a) HIGH-EXPLOSIVE DETONATION

FIRST WAVE SECOND WAVE THIRD WAVE(GROUND-SHOCK INDUCED) (FROM VENTING GASES) (INDIRECT PATH FROM SOURCEOF FIRST OR SECOND WAVE)

(b) DANNY BOY DETONATION

Figure 1.1

9

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S I N.0 C4- -- -

C.))

4.- : - oNee -

ooeo

iJ000oo a

o o0

)G-K . + 0 0 .

.'"~-- 2;/ /_

" ./

.- ***... *,S ,x/.,,/

I * I *. [ 1 I I ,

(!Sd) 31lnSS3ldHI3AO

10

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Figure 1.3 shows pressure-distance curves fo r the first andsecond peaks from Buckboard 12 and Scooter, together with the ob-served data from Project Danny Boy. The major surprise from ProjectDanny Boy was that the second peak was far smaller than the firstpeak, quite the opposite from the HE shot. This difference may beattributable to the lower gas pressure of a nuclear shot in a rela-tively dry medium. In view of the uncertainties in scaling burstdepth, there was not sufficient difference between the first peaksobserved in the Buckboard 12 basalt and Scooter alluvium shots andthose of the Danny Boy shot, to say that there is an appreciabledifference in the first peaks of HE and nuclear shots. It can besaid, however, that the major difference between an HE and a nuclearshot in basalt is the almost complete absence of the gas-ventingpulse (second peak) fo r the nuclear shot. This was the backgroundwithin which ranges of expected peak overpressures were set for theSedan event.

SDANNY BOY FIRST PEAKS (GROUND-SSHOCK-INDUCED)--- DANNY BOY SECONDPEAKS (GAS VENTING PULSE),x, DANNY BOY PEAKS ATnRIBUTED TO NEARBY HE

DETONATION.

_\\ \, NW _-SECOND PEAKS

\1-4

K>4 \ \JFIRST PEAKS

ro 100SCALED GROUND RANGE (th/IbVS)

Figure 1.3

11

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Figure 1.4 shows pressure-distance lines representing firstand second peaks in the Scooter and Buckboard shots, together withthe anticipated peak overpressure fo r the Sedan event. Expectedoverpressures fo r Sedan were originally based on the results ofScooter air-blast measurements. When the results of Danny Boybecame available, the expected overpressure estimates were reviseddownward (as shown in the figure) to agree with the first peaks ofboth Scooter and Danny Boy. Since the lower second peak of DannyBoy was attributable to the low moisture content (-0.5 percent) ofthe medium, a larger second peak could be anticipated from Sedan,where the medium had a moisture content estimated at 5 percent. Itwas not expected, however, that this difference would raise th esecond peak to much more than the amplitude of the first (ground-shock-induced) peak.

0 00

0 MAXIMUMEXPECTEDPRESSURE0 SET RANGES FOR SEDAN BASED ON SCOOTER"0 - SET RANGES FOR SEDAN BASED ON DANNY

BOY0

+ %+

+ N\++

0

00 +

1 ID 100

SCALED GROUND RANGE (FT/lb I)

Figure 1.4

12

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1.3 InstrumentationMeasurements were made with Ballisfic Research Laboratory

self-recording pressure gages. In these gages, a battery-operatedmotor drives a turntable carrying either an aluminized glass disc ora stainless-steel disc. A pressure-sensitive diaphragm, connected toa scribe, permits the pressure record to be inscribed on the disc asthe turntable rotates. The gage motor is started by a timing signalat minus I second. Standard pressure-time gages (PT's) were used atStations I through 6 and very low pressure gages (VLP's) at Stations7 through 9.

Gages were located along the 150-degree radius at the followingradial distances:Station 1 2 3 4 5 6 7 8 9Distance 1000 1260 1670 2200 2960 3970 5290 7050 15,500(ft)

13-14

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CHAPTER 2

TEST RESULTS

2.1 Summary of ResultsTable 2.1 summarizes th e results of th e pressure measurements.

No records were recovered from Stations 1 through 4, and th e gage atStation 6 was overranged and damaged. Peak pressures only were ob-tained at Station 8, because th e gage turntable did not operate.Pressure records of those gages which did operate are shown inFigure 2.1. In th e figure, time is shown from th e arrival of thepressure signal; arrival-time data were not obtained because no zero-time f iducial was inscribed on the records. Venting occurred at 3.2seconds, and th e source of th e air blast at th e edge of th e crater(611 feet) may be presumed at that time.

2.2 Peak OverpressureAt most of th e s tat ions th e gages were overranged. At

Station 5 th e scribe struck th e edge of th e turntable, producing aflat section during th e early portion of th e wave., Peak overpressurewas obtained by extrapolating back to shock arrivbi from that portionof th e curve which occurred at a later time and was not dis torted.There is a range of uncertainty in th e extrapolation which has beenindicated in both Table 2.1 and th e subsequent evaluation of th edata. Peak overpressure versus scaled distance,: compared withStagecoach III, Buckboard 12, and Scooter are shown in Figure 2.2.

No explanation is offered for th e late spike which occurs onthe records from Stations 5 and 7. Figure 2.1 makes clear that th ewaveforms were different from those of Figure 1.1, were indeed morelike those from above-ground shots than from buried ones.

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16

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00mN

- -d 0 040 107m v0CD In

K)o ILi c',1- -~j 4 >33 IL>wN

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17

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i-".- SEDAN

U)IL

w

0

w ., I__ N~x" SECOND PEAKSa-

IFIRST PEAKS

.01, 1 10 100SCALED GROUND RANGE (ft/IbV3)

Figure 2.2

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2.3 Positive PhaseIn Figure 2.3, the scaled duration of the positive phase is

shown as a function of scaled ground range. It is compared withScooter and Stagecoach III values.

Figure 2.4 shows the scaled positive-phase impulse as afunction of scaled distance, again compared with Stagecoach III andScooter values.

0 SEDAN

6E SCOOTER TOTALPOSITIVE-PHASEz DURATION0

~-10- STAGECOACH MTOTAL POSITIVE-

o PHASE DURATION-J4

SCOOTER MAINWAVE DURATION

00

10 10 0SCALED DISTANCE (ft/Ib

Figure 2.3

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10 SEDAN

TOaA IMUS

1010

.20

'Iia_-J0.

STGCAHD

o.

SCAEDDITACE( f / l

Figure 2.4

,20

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CHAPTER 3

DISCUSSION

3.1 Peak OverpressurePeak overpressures were two to three times those of Stagecoach

III at the same scaled distance, four or more times larger thanwould have been expected from Buckboard and Scooter results, andabout ten times larger than would have been predicted by simple cube-root scaling of Danny Boy pressures. (This latter disparity comesfrom the fact that Sedan second peaks are compared with Danny Boyfirst peaks.) The value obtained at the most distant station is notcredible and is discounted here, in spite of the fact that it agreesmost nearly with the expected pressures.

3.2 Positive-Phase ImpulseThe scaled values fo r the positive-phase impulse are about th esame (Figure 2.4) as the total positive phase fo r Stagecoach III andScooter. The total positive phase for Stagecoach III and Scooterincludes the ground-shock-induced wave as well as the gas-ventingwave. Sedan values are in effect slightly larger scalewise thanthose of the HE shots since ground-shock-induced impulse is includedfo r Stagecoach III and Scooter but not fo r Sedan.3.3 Positive-Phase Duration

Sedan durations were shorter (Figure 2.3) than those of th eScooter main (gas-pressure) wave by 2 to 2-1/2 times, and shorterthan the Scooter total positive-phase duration by nearly a factorof 10. They were one-fifth the Stagecoach III total positive-phaseduration.

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3.4 Wave ShapeExcept as noted below, th e waveforms of the Sedan pressure

waves are more like those of surface or very shallow bursts thanthose of comparable buried charges. There was no indication of aground-shock-induced wave at any station, and this was unexpected.Since ground-shock-induced overpressures are proportional to surfacepeak velocities, and the latter are related to burial depth, th efirst peaks of Sedan should have been about th e same as those ofStagecoach III at comparable scaled distances (that is about one-tenth the amplitude of the Sedan second-peak overpressure) and shouldtherefore have been easily discernible on the records.

The records from 2960 feet and 5290 feet (Stations 5 and 7,respectively) show a spike occurring at later times. The spikeoccurs so late that it is not easily attributable to a venting ofgases after the main venting.

The record from th e gage at Station 5 was saturated fo r aboutthe first 250 Psec, but the decay of the balance of the record permitsan approximation of th e peak pressure by extrapolating back to thearrival time. Ordinarily th e ratio pt+/I+ is greater than 2, reflect-

\ing the decay of the wave in a concave upward slope. However, thevalues obtained at both the 2960- and 5290-f6ot stations showpt+/I+ ; 2, which is in effect a triangular wave.

From consideration of Figures 2.2 to 2.4, the differencesbetween Sedan and both the Stagecoach III and Scooter waves emerge.The differences between Sedan and Scooter are even more apparentwhen compared in Figure 3.1. Although the two waves have been super-imposed in the figure, it should be borne in mind that absolute timeis unknown fo r th e Sedan wave. One can deduce not only that th ehigher gas pressures of the nuclear event caused the higher pressurepeaks for Sedan, bu t that smaller volumes of gas and more rapidventing through a relatively larger vent caused the shorter durationsof Sedan. That the scaled impulses were nearly the same suggeststhat the amount of gas produced was nearly equal scalewise for theHE and nuclear detonations. The shorter durations may also be dueto the rapid condensation of superheated steam behind the shockfront.

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Cun

2 ~r-'U

22

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3.5 Blast Suppression by Charge BurialBlast suppression may be defined as th e factor by which th e

peak overpressure is reduced by charge burial below some referencepressure. The reference pressure may be taken from any of severalcurves: th e ones chosen here are (a) th e Kirkwood-Brinkley' 2 free-air curves for cast TNT, (b) th e IBM Problem M fo r nuclear bursts,13and (c) measured values of peak overpressures from surface bursts(predominantly HE). 5 In th e case of measured overpressures at th egreater ranges where fractional-psi pressures are involved, meteor-ological effects enter into consideration and give results whichshould not be expected to agree with calculations for an infinitehomogeneous atmosphere. Figures 3.2 to 3.4 show th e blast suppressionrelative to (a), (b), and (c), respectively, for buried nuclear andlarge HE explosions. Data points for Project Sedan have been addedto the figures. From these data points, it is clear that Sedan peakpressures were suppressed less than would have been expected for theSedan burial depth. In other words, the peak overpressures are thosewhich would have been expected from the same yield at a shallowerburial depth.

The possibility exists that this observation results fromimproper scaling of ground range. A comparison of Sedan and Scooterpeak overpressures shows that this is not the case. If ground rangeis proportional to Wn, n must be greater than one-half to bring thevalues into agreement--a scaling which is without physicaljustification.

Figures 3.2 to 3.4 distinguish between the suppression of theground-shock-induced air blast and the gas-venting air blast. Theformer disappears for the shots at the shallower burst depths becauseit is overtaken by the latter at all except very close ranges. Inall cases, except for the Buckboard 13 ground-shock-induced air blast,the blast suppression factor decreases with increased scaled groundrange. The only nuclear shot other than Sedan for which blast sup-pression can be compared is Teapot ESS, which also shows a smallerblast suppression factor than the corresponding HE charge. LikeSedan, it also appears to have originated at a comparatively shallowerscaled burst depth.

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"SEDAN--- FIRST PEAK

SECOND PEAK,BUCKBOARD 13

/ 1.75 ft/lb 1/3\ /1000

X\ \/- \ /BUCKBOARD -2,\1.25 ft/b'1 3 / STAGECOACH I

. 2.3 ft/Ib'/3

STAGECOACH Z f/3,' 0.5 ft/lb" 3 N "SCOOTER -1.25 ft/lb"ir 'BUCKBOARD 13

to0 , 1.75 ft/lb'/3

z -0 -. STAGECOACH r3) 1.0 ft/lb"/3

.\NDANNYBO1 X1.165 ft/lb/0. BUCKBOARD ItD 0.75 ft/lb'/3

, r E \ SCOOTER1.25 ft/lb"tBUCKBOARD 121.25 ft/lb"/3

1 STAGECOACH 3MTEAPOT ESS 1.0 -fl/lb '/30.5 ft/lb' 3

BUCKBOARD, I BASED ON KIRKWOOD -0.75 fl/lb"/ 3 BRINKLEY CURVE FORFREE AIR BLAST FROMCAST TNT.

STAGECOACH II0.5 ft/lb"/3

10 100SCALED GROUND RANGE(ftlib'"')

Figure 3.2

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"X SEDAN- - - FIRST PEAKSECOND PEAK

IBUCKBOARD 1311.75 ft/Ib'/3

1000\ /\ / S/\/\ /

STAGECOACH I-- \~ / 2. 3 ft/lb"'/0.

I- \ N N UCKBOARD 13Ia 4..N" 1.75 ft/lb '/'z TAGECOACH , TCOOTEo 0.5 ft/lb 1/3 N STACAC

"..= S . ft /lb 1/ 3)- BUCKBOARD 12 B O, 1.2 5 ft/tlb V/3-\ N N N DANNYBOY

- 1:165 ft/lbBUCKBOARD 110.75 ft/lb'1/3

m .SCOOTER

1.25 ft/Ib /3

STAGECOACH 311.0 f1/lbt/

BASED ON IBM PROBLEM MBUCKBOARD 11 FREE AIR ASSUMING I b. E0.75 ft/ib I lb NE

TEAPOT ESS0.5 ftl/lb

STAGECOACH U0.5 ft/lb' 1 3

10 tooSCALED GROUND RANGE(ft/lb"/ 3 )

Figure 3.3

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"" EDAN--- FIRST PEAK

SECOND PEAKBUCKBOARD 131.75 ft/IbV3/N. /

1000-\ /

STAGECOACH I- / \"'-2.3 ft/lb" 3

ff \SCOOTER.. 525lb/U OBUCKBOARD 13I00 STAGECOACH Z 1.75 ft/b1/33

0.5-. .t/lbb .f/'

a: ". 'DANNYBOYif. 0.75I~r. t/IbIb /'

0.5f/b" -STAGECOACHBUKOR6 tl"

UBUCKBOAR 12\

S O IISTAGECOACH1 51.0 ft/lb"

TEAPOT ESS .__-0.5 ft/lb'BU BUCKBOARD II0.75 ft/lb"1/ 3

' BASED ON MEASUREDSURFACE- BURST OVERPRESSURES

SSTAGECOACH .5 ft/lb"3 /, , , 1 ,11 i I I11 ,,,1 ,'I I iii

I0 W00SCALED GROUND RANGE (ft/Ib/ 3 )

Figure 3.,4

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Figure 3.4 discloses that over the ground ranges between2 and 30 ft/lb1/3 the blast suppression factors fo r HE second peaksare proportional to a constant power of the burst depth (see Figure3.5 fo r an example). This observation, taken at several ground ranges,permits derivation of the approximation:

f 412r/W). 6.4 dob2"85,

where f is the blast suppression factor, r/W 1 /3 is the scaled sroundrange in ft/lbl 3, and dob is the scaled burst depth in ft/lbl/3

Data are insufficient to derive a similar expression fornuclear shots, but Teapot ESS and Sedan suggest that a similar ex-pression fo r nuclear detonations would have the form:

f (W'a + b dob) 75 (see Figure 3.5).When peak overpressure blast suppression factors fo r the first

(ground-shock-induced) peak were compared, there was a relationshipwith burst depth over a certain range of scaled ground range butnot at others (Figure 3.6). Also, no consistent relationship withground range could be derived. (Since Sedan had no first peak, itis not represented in Figure 3.6).

The blast suppression factors of Figures 3.2 to 3.4 haveassumed that air blast from HE is the same as that from nuclear ex-plosives. For comparable bursts above ground, it has been observedthat the air blast from 1 kiloton of nuclear explosives (radiochemicalyield) is equivalent to that from 1/2 kiloton of HE. No comparableobservation has been made fo r below-surface bursts, nor is thereadequate data to do so. Let such a relationship as is observedbetween blast from HE and nuclear explosives for above-surface burstsbe assumed fo r buried explosions. Then, when comparing with IBM-Mcurves, the values fo r nuclear charges bear the same relationship tothe IBM curves as they did in Figure 3.3. The HE values of blastsuppression, however, shift upward (see Figure 3.7). The net effect,illustrated in Figure 3.8, is a shifting upward of blast suppressionfactors fo r HE relative to those fo r nuclear explosives. There is a

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greater spread between the suppression factors fo r the two types,and the rate of suppression of blast for HE is essentially twice thatfo r the two nuclear explosions. Thus, fo r nuclear explosions th epreceding equation may become[ la ) + b ] 5where the radiochemical yield is used, and suppression is the ratioof IBM-M overpressures to those observed for the nuclear explosions.

When impulse blast suppression factors (the ratio of th epositive-phase impulse for a surface burst to the positive-phaseimpulse observed fo r the subsurface burst) are considered, th eresults are as shown in Figures 3.9 through 3.11. There is no singleuniform relationship with burst depth or with ground range, as in thecase of the blast suppression factors fo r peak overpressure (Figure3.12). In fact, there is an abrupt change in suppression with burstdepth at scaled depths deeper than Scooter and Buckboard 12, forwhich the total positive-phase impulse includes both the gas-ventingpulse and the ground-shock-induced pulse. This suggests a differencein venting, and hence in crater mechanism, between the rising andfalling portions of the crater depth-of-burst curve.

One may speculate that fo r shallower burst depths, the gas-venting impulse declines in importance with burial depth--declinesfrom being the sole source fo r a surface burst to contributing nothingat containment. The gound-shock-induced impulse thus becomes rela-tively more important with burial depth, since it becomes the onlysource for a contained burst.

The most interesting point to be made from Figures 3.2 through3.5 and Figures 3.9 through 3.11 is that whereas the impulse sup-pression values for Sedan agree with those fo r Scooter, Buckboard 12 ,and Stagecoach III HE explosions, the overpressure suppression factorsare much lower, making the overpressure appear to arise from a largeryield or a shallower burst. By contrast, the scaled impulse forDanny Boy was nearly 40 times smaller than that of HE explosions atcomparable scaled burst depths, while the overpressure (first peakonly) was comparable to that from the other explosions.

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Comparison of the Sedan blast wave with those of HE explosionsat comparable burial depths suggests that the Sedan gases were con-fined in a relatively smaller cavity at higher pressures at the timeof venting and that, as a consequence, they vented more rapidly oncethe mound ruptured- This is borne out by calculations. Knox 1 4 reportsthe initial conditions for Scooter and Sedan determined by the SO C(underground nuclear explosion effects) code to be:

Scooter SedanCavity Pressure 77 bars 147.2 bars (302 bars)Cavity Radius 42 feet 175 feet

Knox found that achieving agreement with observed surface motionrequired a cavity pressure of 302 bars. It is interesting that the302 isaotheseratio of Sedan to Scooter cavity pressures, 77 is about the sameas the ratio of the observed peak overpressures. It may also beobserved that the ratio of Sedan scaled cavity volume to that ofScooter* (0.362) is about the same as the ratio of the scaled positive-phase durations of their gas-venting pulses (0.33 to 0.5) (seeFigure 3.1).

The approximate equality of scaled impulses for Scooter,Stagecoach III, and Sedan suggests that, relative to the yields, thequantity of air-blast energy available with HE is about the same asthat available from a nuclear explosion in a soil with the moisturecontent of Sedan alluvium. This observation, together with thepreceding one concerning the relatively smaller cavity and higherventing pressure of a nuclear burst, indicates either (1) a mecha-nistic difference between nuclear and HE explosions or (2) a changewith size of charge which gives rise to a wave with a higher peakand shorter duration. In either case, higher peak pressures thanthose predicted by HE explosions may be expected for nuclear ex-plosions in desert alluvium.3.6 Inferred Yield of Sedan

From the preceding information, an apparent yield can bededuced for Sedan, albeit with considerable skepticism.

*For the purpose here, cavity volumes may be calculated asspheres, since departures from sphericity are assumed to be similarin the two cases.

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Figures 3.11 and 3.12 showed that the scaled positive-phaseimpulse of Sedan agrees well with those of Stagecoach III and Scooter.This would indicate that the yield was about -as stated, if oneassumes no difference in the impulse of nuclear and HE shots.

Figure 3.8 (based on IBM-M) shows that the peak overpressurefrom nuclear shots is suppressed less by burial than that from HEshots. This is true only if the yield of Sedan is 100 kilotons andits cube-root-scaled burst depth is 1.1 ft/ lb"/. What if the rateof suppression is th e same fo r HE and nuclear explosives, and theSedan yield is in error? Then the Sedan value in Figure 3.8 shouldli e on a line through Teapot ES S and parallel to the HE data. Sedanwould then have an apparent scaled burst depth of 0.75 ft/lbl/3.Only a 300-kt device buried at 635 feet would have such a scaledburst depth. If a similar comparison is based on Figure 3.5 ratherthan Figure 3.8, a scaled burial depth of 0.84 ft/lbl/3 and hencea yiel'd of 215 kilotons is indicated.

If one returns to Figure 3.12 and again assumes that the rateof suppression is the same fo r HE and nuclear explosives and thatthe Sedan yield is in error, a line through the Teapot ES S datumindicates a scaled burst depth of 0.84 ft/lbl/3 and hence an apparentyield of 215 kilotons. Thus, either the Sedan yield may be presumedcorrect, in which case the rate of suppression is not the same forHE and nuclear explosives or the suppression ratios may be assumedalike, in which case the yield must be greater than 100 kilotons.The former is, of course, the more reasonable.

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xa>2

I. ms-- 0 +

utJn 0f

-4Pz

0 x

tici

(p*,n-.d/lj-lQ .. 1-~d,)WOIOVJ NOlSS3WddnS ISV-18

32

0 o 4

o 8 0({P*0n*0ud./(lln '09llnd) 8O1OV=i NOISS]8d8AS L.sv-8

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10,000

SEDAN__ __ ,FIRST PEAK

SECOND PEAK

BUCKBOARD 13\ /\ /\ \ /

, oo BUKOAD1

NI/\ /\ /\ /SSOSTAGECOACH

A

U)

\SCT SCOOTERSBUCKBOARD 13

00- BUCKBOARD 12I-

S~~~' .. ST G C A C I

UCKARDGOUND ANNY

TEAPOT ESS

STAGECOACH "IT

I0 I00 1000SCALED GROUND RANGE (ft/lb '3)

Figure 3.7

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1000BLAST SUPPRESSION AT

ft/lbV 3 - 5

IBM-M/HE DATAASSUMING - KT HE=IKT NE-- ,-.,49 dab t'*5 (FIG, 3.7)

SBUCKBOARD 13 / I M-M/HE DATA

ASSUMING IKT HE IKT NE"0 ~30.dob2 ' 8 (FIG. 3.3)

oBUCKBOARD 12 /0.

STAGECOACH 13 D

4

0.

/,ASMN IKTH/N

0. BUCKBOARD II1

0 /I. 0-.BM- DTm 10 X SEDAN

-- / 9.2 dob1,4 5STAGECOACH "3'/

STEAPOT ESS_ * ALLUVIUM H EO BASALT HE

-- X ALLUVIUM NE

0.1 1.010 SCALED GROUND RANGE (ft/Ib'/)

Figure 3.8

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Ioo- STAGECOACHI

BUCKBOARD13

10SCOOTER

BUCKBOARD 12STAGECOACH T0

"< 1 SEDAN------ BUCKBOARD I.

STAGECOACHt

, I , , ,I I I I I I 11 l1, rI0 100 I000

SCALED RANGE (IAbV')

Figure 3.9

IO0 I1B M PROBLEM M

STAGECOACH I

BUCKBOARD IS

21 0

_ SCOOTER2 -- _ _BUCKBOARD 12STAGECOACH X4 BUCKBOARDIt .I SEDAN

STAGECOACHUl

, I , ,I , , , I , , , , , I 1 1I , , ,IO I00 1000

SCALED RANGE (ft/lb"/R)

Figure 3.1035

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STAGECOACH I

BUCKBOARD 13

!j

10 -- SCOOTERS' BUCKBOARD 12z STAGECOACH "

, BUCKBOARD II . 1 SEDAN

STAGECOACH 3

, I , 1 , ,1 , , , I 1 ,1, 1 , ,0SCALED RANGE (ft/IbV/0

Figure 3.11

Go0 /STAGECOACHII! - o/

=: /UCKBOARD 3 0

OTAOCOAOC.7BUCKBOARDIt

TEAPOTESS X/ IMPULSESUPEIO

/

ISI

STAE AACECOAC f/bU

*ALLUVIUM RE0 BASALT HE

ISEDAN RE

.1 I0SCALED BURST DEPTH Ilf/IbI'/)

Figure 3.12

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CHAPTER 4

CONCLUSIONS

Peak overpressures from Sedan did not show the ground-shock-induced pressure pulse (first peak) typical of cratering explosions.Only a gas-venting pulse (second peak) was observed.

Peak overpressures measured on Sedan were about two to threetimes those of Stagecoach III, four times the values which wouldhave been predicted by the second peaks of Scooter or Buckboard 12 ,and ten or more times the first peaks of Scooter, Buckboard 12 , andDanny Boy.

The scaled duration of the positive phase of the Sedan shockwave was less than one-half the scaled duration of the Scooter gas-venting pulse, almost one-tenth the scaled duration of the entirepositive phase of the Scooter blast wave, and about one-fifth thatof Stagecoach III.

The scaled impulse of the total positive phase of the Sedanblast wave is about equal to those of Stagecoach III and Scooter,indicating that the gas pressure produced by a nuclear charge inalluvium with the moisture content of the Sedan alluvium is aboutthe same as that produced by HE.

The suppression of peak overpressure fo r Sedan was considerablyless than would have been expected for its burial depth; similarly,the peak overpressures appear as those which would be expected fromthe same yield at a shallower burial depth. A blast suppressionfactor (ratio of peak overpressure of an equivalent surface burst

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to peak overpressure observed for a buried charge) for other HEexplosions can be approximated by:

S4126.4]f = (r/W' /3 )1.4 + 6. do " ,

where r/W /3 is the scaled ground range in ft/lb'/3 and dob is thescaled burial depth in ft/ibl/3.. For nuclear explosions the aboveexpression may be expected to have the form,

f r//3 + b ]dob' "In spite of the lack of agreement of Sedan peak overpressure

suppression factors with those of HE events at comparable scaledburst depths, there is quite good agreement for impulse suppressionfactors. There is a change in rate of impulse suppression withscaled burial depth at about the peak of the crater depth-of-burstcurves which suggests a difference in crater mechanismbetween therising and falling portion of the depth-of-burst curves.

Peak overpressure appears to be related to cavity pressure,at the time venting occurs, and positive-phase duration appears tobe related to cavity volume at the same time.

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REFERENCES

1. Perret, W. R., et al., Project Scooter Final Report, SC-4602(RR),Sandia Corporation, October 1963.2. Doll, E. B., and Salmon, V. Scaled HE Tests--Operation Jangle,WT-377, Final Report on Project 1(9)-1, Menlo Park, April 1952.3. Bishop, J. A., and Lowance, F. E., Cratering Phenomena, OperationJangle, WT-373, May 1952.4. Lewis, J. G., Crater Measurements, WT-1105, Armed Forces Special

Weapons Project, July 18, 1958.5. Vortman, L. J., et al., 20-Ton HE Cratering Experiment in DesertAlluvium, Project Stagecoach, Final Report, January 1962,SC-4596(RR).6. Vortman, L. J., et al., 20-Ton and 1/2 Ton High ExplosiveCratering Experiments in Basalt. Rock, Project Buckboard, FinalReport, SC-4675(RR), Sandia Corporation, November 1960.7. Nordyke, Milo D., and Wray, William R., Preliminary Summary

Report, Project Danny Boy. UCRL-6999, July 20, 1962.8.. Project Sedan, Crater Measurements. Lawrence Radiation Laboratory,PNE-216P. To be published.9. Sachs, D. C., and Swift, L. M., Small Explosion Tests, ProiectMole, Vols. I and II, AFSWP-291, Menlo Park, December 1955.

10. Murphey, B. F., High Explosive Crater Studies: Desert Alluvium,Sandia Corporation Research Report, SC-4614(RR), May 1961.

11. Vortman, L. J., Close-in Air Blast from a Nuclear Detonation inBasalt, Project Danny Boy. POR-1810(WT-1810) September 15, 1962.12. Kirkwood, J. G., and Brinkley, S. R., Jr., Theoretical Blast-Wave Curves for Cast TNT, OSRD 5481, NDRL A-341, August 23, 1945.13. Broyles, C. D., IB M Problem M Curves. Sandia Corporation

Technical Memorandum, SCTM 268-56-51. December 1, 1956.14. Knox, J. B., and Terhune, R. W., Cratering Physics ConceptsDerived from an Analysis of Ground Surfaces Motion. LawrenceRadiation Laboratory, Report UOP/KA 63-18, October 1963.

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TECHNICAL REPORTS SCHEDULED FOR ISSUANCEBY AGENCIES PARTICIPATING IN PROJECT SEDAN

AEC REPORTSAGENCY PN E NO. SUBJECT OR TITLE

USPHS Z0OF Off-Site Radiation SafetyUSWB Z01F Analysis of Weather and Surface RadiationDataSC 202F Long Range Blast PropagationREECO 203F On-Site Rad-SafeAEC/USBM 204F Structural Survey of Private Mining Opera-

tionsFAA 205F Airspace ClosureSC ZlIF Close-In Air Blast From a Nuclear Event in

NTS Desert AlluviumLRL-N Z2ZP Scientific PhotoLRL 214P Fallout StudiesLRL 2 5F Structure ResponseLR L 2 16P Crater MeasurementsBoeing Z17P Ejecta StudiesLR L 2 18P Radioactive PelletsUSGS 219F Hydrologic Effects, Distance CoefficientsUSGS 221P Infiltration Rates Pre and Post ShotUCLA 224P Influences of a Cratering Device on Close-InPopulations of LizardsUCLA 225P Fallout CharacteristicsPt. I and II

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TECHNICAL REPORTS SCHEDULED FOR ISSUANCEBY AGENCIES PARTICIPATING IN PROJECT SEDAN

AGENCY PNE NO. SUBJECT OR TITLEBYU 226P Close-In Effects of a Subsurface NuclearDetonation on Small Mammals and Selected

InvertabratesUCLA 228P Ecological EffectsLRL 231F Rad-Chem AnalysisLRL 232P Yield MeasurementsEGG Z33P Timing and FiringWES 234P Stability of Cratered SlopesLRL 235F Seismic Velocity Studies

DOD REPORTSAGENCY PN E NO. SUBJECT OR TITLE

USC-GS 213P "Seismic Effects From a High Yield NuclearCratering Experiment in Desert Alluvium"

NRDL 229P "Some Radiochemical and Physical Measure-ments of Debris from an Underground NuclearExplosion"NRDL 230P Naval Aerial Photographic Analysis

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ABBREVIATIONS FOR TECHNICAL AGENCIES

STL Space Technology Laboratories, Inc., Redondo Beach, Calif.SC Sandia Corporation, Sandia Base, Albuquerque, New MexicoUSC&GS U. S. Coast and Geodetic Survey, San Francisco, CaliforniaLRL Lawrence Radiation Laboratory, Livermore, CaliforniaLRL-N Lawrence Radiation Laboratory, Mercury, NevadaBoeing The Boeing Com pany, Aero-Space Division, Seattle 24, WashingtonUSGS Geological Survey, Denver, Colorado, Menlo Park, Calif., and

Vicksburg, MississippiWES USA Corps of Engineers, Waterways Experiment Station, Jackson,

M ississippiEG G Edgerton, Germeshausen, an d Grier, Inc., Las Vegas, Nevada,

Santa Barbara, Calif., and Boston, MassachusettsBYU Brigham Young University, Provo, UtahUCLA UCLA School of Medicine, Dept. of Biophysics and Nuclear Medicine,Los Angeles, Calif.NRDL Naval Radiological Defense Laboratory, Hunters Point, Calif.USPHS U. S. Public Health Service, Las Vegas, NevadaUSWB U. S. Weather Bureau, Las Vegas, NevadaUSBM U. S. Bureau of Mines, Washington, D. C.FA A Federal Aviation Agency, Salt Lake City, UtahREECO Reynolds Electrical and Engineering Co., Las Vegas, Nevada

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SUPPLEMENTARY DOD DISTRIBUTION FOR PROJECT SEDAN

PNE NO. DIST. CAT. PNE NO. DIST. CAT. PNE NO. DIST. CAT.200 26, 28 214 26 226 42201 2, 26 215 32 228 42202 12 216 14 229 26, 22203 28 217 14 230 100204 32 218 12, 14 231 22205 2 219 14 232 4211 12 221 14 233 2212 92, 100 224 42 234 14213 12, 14 225 26 235 14In addition, one copy of reports 201, 202, 203, 211, 214, 215, 216, 217,

218, 221, 225, 229, 230, 232, 234, an d 235 to each of the following:The Rand Corp. Mitre Corp.1700 Main St., Bedford, MassachusettsSanta Monica, CaliforniaAttn: Mr. H. Brode General American Transportation Corp.Mechanics Research Div.U. of Illinois, 7501 N. Natchez Ave.,Civil Engineering Hall Niles 48, IllinoisUrbana, IllinoisAttn: Dr. N. Newmark Attn: M r. T. Morrison; Dr. SchiffmanStanford Research Institute Dr. WhitmanMassachusetts Institute of TechnologyMenlo Park, California Cmrde ascuetCambridge, M as sacliusettsAttn: Dr. Vaile

E. H. Plesset Associates1281 Westwood Blvd. ,Los Angeles 24, CaliforniaAttn: M r. M. Peter