fireball 2

8/11/2019 Fireball 2

1/16

LA-7833-MSInformal Report

C.3Cl C- l 4 REPORT COLLECTI ON

REPRODUCTIONCOPY

Fireball Shape as a Height-of-Burst Diagnostic

,1

i

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LOSALAMOS SCIENTIFIC LABORATORYPostOf f i ceBox 1663 Los Al amos, New Mexi co87545


2/16

An Affirmative ActIon/Equal Opportunity Employs

This report was not edited by the TechnicalInformation staff.

Work supported by the Defense NuclearAgency.

T h, s rewtt was p rw. rrd s a n a cc ou nt o f work s pwwu mdb y th e U ntt ed S ta te s G ov rm me nt. N cIt he r th e U mle d S ti le sn or th e U .il ed S U1e s De mri men t o f En . rg v. n or an y of th ei r

m pl oy ee s. n ot a ny of th em c .nt mc wws . s ub con tr.ct o: s. o rtheir mployers, makes any warrantY. x vrei s o r Imp li ed . o ra ss um es M -Y 1 ,s s1 h .b il my 0 , re=vo nx tb d, t v fo, t he d CC U CY.c omp le te neu , ? r u sef uln es s of an . mf on nau o?. ap pdr at us ,n roduct . o r DIC.CeUdswlowd. or raaresents that m usc wouldn ot i n ft ln sc p nv.t .l y o wn ed n sh ls .

UNITED STATICS

DEPARTMENT OF lcNcIRGV

CONTRACT W-740 B-ZNG. 36


3/16

LA-7833- MSI nf ormalReport

Swcial DistributionIssued: June 1979

Fireball Shape as a Height-of-Burst Diagnostic

Eric M. JonesJeffrey D. Colvin*

EG&G, Inc., P.O. Box 809 Los Alamos, NM 87544.


4/16

i

FI REBALL SHAPE AS A HEI GHT- OF-BURST DI AGNOSTI C

by

Er i c M J ones and J ef f rey D. Colvin

ABSTRACT

The shock wave produced by an atmospheri c nucl earf i rebal l ref l ects f rom the ground and st r i kes thebot t om of t he gl ow ng f i r ebal l at t he t i me when t he sumof the f i rebal l radi us and the shock radi us equal st w ce t he bur st hei ght . RADFLO cal cul ati ons have beenused t o def i ne the f unct i on R f i rebal l ) + R shock) =f Y, t) . Fi rebal l shape i nf ormat i on i s used todet er mne t he t i me when shock/ f i r ebal l i nt er act i onoccurs and to deri ve the hei ght- of- burst .

I . I NTRODUCTI ON

The evol ut i on of an atmospher i c nucl ear f i rebal l i s governed by the weapon

mass, yi el d and conf i gurat i on, the pressure and temperature of the atmosphere,

and the hei ght- of - burst. I n many ml i t ary appl i cat i ons hei ght s-of - bur st ar e l ow

enough t hat i nt eract i on between the gl ow ng f i r ebal l and t he shock wave

r ef l ect ed f r om t he gr ound sur f ace occur s l ong bef or e buoyancy f or ces become

i mport ant . I n many of these appl i cat i ons, the desi r ed ef f ect i s a sensi t i ve

f unct i on of bur st hei ght . Real - t i me hei ght -of - burst data may be of potent i al

val ue, part i cul arl y i f t he dat a can be determ ned f rom a si ngl e observi ng

stati on.


5/16

Let us suppose t hat an at mospher i c nucl ear bur st of unspeci f i ed y-

occurs at an unknown range from a proper l y i nstrumented observi ng stat i on.

parameter s to be determned are yi el d, range, azi muth, and hei ght -of - burst .

pr opose t hat al l f our par amet er s can be det er m ned w t h t wo pr i mar y i nst r um

el d

The

We

nt s

and a smal l computer or processor. The two i nst ruments are a bhangmeter and a

fast read-out , real - t i me i magi ng ar ray. The bhangmeter i s used to determnem ni mum t i me and, hence, t he yi el d whi l e r eal - t i me f i r ebal l shape i nf or mat i on

provi des the three remai ni ng parameters.

II. METHOD

We presume that burst s of i nterest w l l be l ow- mass ai r burst s. The

assumpt i on of l ow mass assur es t hat we w l l be deal i ng w t h weapons w t h hi gh

radi at i ng temperatures and t hat t he ear l y f i r ebal l growth w l l be vi r tual l y

spher i cal . U. S. at mospher i c t est s of weapons i n massi ve t ower s or suspendedfrom bal l oons show consi derabl e asymmetr i es and bri ghtness i r regul ar i t i es even

at very l at e t i mes. Ai r dr ops of l ow mass- t o- yi el d rat i os al l pr oduce ver y

spher i cal f i rebal l s.

The yi el d i s determ ned fr om ti me- of- mni mum measured w th a bhangmeter.

Duri ng the bl ast wave phase of expansi on t he radi us i s cl osel y

approxi mat ed by

R= 301 Y/ P) l / 5 t */ 5, 1)

where R i s the radi us i n meter s; Y the yi el d i n ki l otons; p the ambi ent

at mospher i c densi t y i n m l l i grams per cubi c cent i meter ; and t the t i me i n

seconds. Because the

acceptabl e to assume a

as yet t o be det er m ned

I magi ng data can

radi us i s so i nsensi t i ve t o densi t y i t w l l probabl y be

val ue f or t he densi t y. An i t er at i ve scheme based on t he

burst hei ght coul d be adopted i f deemed necessary.

be used t o der i ve t he t i me hi st or i es of t he ver ti cal and

hor i zontal angul ar di ameter s. Know edge of the yi el d and the hor i zontal angul ar

di amet er l eads di r ect l y t o t he r ange and, f r om t he posi t i on of t he i mage on t he

detector, azi muthal data i s obtai ned.


6/16

The f i nal pi ece of data, the hei ght - of -burst , can be obtai ned f rom

compari son of the two angul ar di ameters.

The f i r ebal l expansi on w l l be t spher i cal unt i l t he r ef l ect ed shock wave

st ri kes t he gl ow ng f i r ebal l . Shor tl y af t er shock/ f i r ebal l i nt er act i on t he

bot tom sur f ace of t he f i r ebal l i s sever el y f l at tened. Before the i nteract i on,

t he r at i o of t he ver t i cal di amet er t o t he hor i z ont al di amet er i s appr oxi mat el y

equal one but as t he i nt er act i on pr oceeds t he r at i o dr ops shar pl y. Anal ysi s of

t he t i me hi st or y of t he di amet er r at i o pr ovi des a t i me- of - i nt er act i on whi ch can

then be used to deri ve the hei ght- of - burst.

III. HEI GHT- OF- BURST SCALI NG DATA

The LASL one-di mensi onal , spher i cal , radi ati on tr ansport / hydrodynam cs

pr ogr am RADFLO has been ver y successf ul i n cal cul at i ng at mospher i c nucl earf i r ebal l evol ut i on. Fi r ebal l and shock r adi i pr oduced by t he progr am ar e i n

good agreement w th data.

We assume w th some conf i dence that the shock/ f i r ebal l i nteract i on occurs

when

SH = 2H- RFB 2)

where RSH i s the shock radi us, RFB i s the f i rebal l radi us and H i s the burst

hei ght Fi gur e 1) . We r ecogni ze t hat t he r ef l ect ed shock t r aver ses sl i ght l y

heat ed ai r bef or e st r i ki ng t he f i r ebal l and t hat t he i nt er act i on act ual l y occur s

sl i ght l y bef or e t he t i me gi ven by equat i on 2) . However, we expect that the

ef f ect i s smal l compar ed t o l i kel y yi el d uncer t ai nt i es.

A ser i es of RADFLO cal cul at i ons have been made f or burst s of var i ous

yi el ds at sea- l evel densi t y 1. 2x10- 3 gcm 3) . The f i r ebal l r adi us was chosen as

the 0. 2 eV temperature contour whi l e the shock radi us was chosen as the l ocat i on

of maxi mum densi ty i n the computed shock prof i l e. Posi t i onal uncer tai nt i es are

about one cel l w dt h or about one per cent of t he r adi us. These data were used

to compute t i me hi stor i es of RSH + RFB. The r esul t s ar e pr esent ed i n f i gur e 2.

3


7/16

UNCLASSI FI ED

Fig. 1Determnat i on of the t i me of f i rebal l / shocki nteract i on permts der i vat i on of burst hei ght .

1 ?

BLAST WAVE

~ REGIME

fa

102,:2 ,~-1 d

TI ME see)Fig. 2

The f i rebal l radi us RFB) and shock radi us RsH)are cal cul ated w th RADFLO. Know ng the yi el dand t i me of f i rebal l / shock i nteract i on gi ves2H = RFB+RSH f r om t he gr aph. See t he t ext f or afur ther di scussi on of thi s f i gure.

UNCLASSI FI ED


8/16

The curves i n f i gure 2 are l abel ed w t h t he paramet er 301 Y/ P) l / 5. The

curves, i n ascendi ng order, correspond to sea- l evel burst s w t h yi el ds of 1,

3. 5, 12, 32, 75, 200, 800, and 1600 ki l ot ons.

The pl ane of f i gur e 2 i s di vi ded i nt o t hr ee phenomenol ogi cal r egi ons.

Dur i ng t he ear l y f i r ebal l expansi on t he ai r i mmedi at el y behi nd t he shock hasbeen heated t o great er than 0. 2 eV and the shock and f i rebal l radi i are

i denti cal . Dur i ng t hi s bl ast wave phase bot h r adi i ar e cl osel y appr oxi mat ed by

equati on 1. At a t i me gi ven by t he l ef t most dashed l i ne, t he weakened

no l onger capabl e of heat i ng ai r above 0. 2 eV and t he shock det aches

f i rebal l .

shock i s

f rom the

At very l ate t i me, f i r ebal l s whi ch have not yet under gone shock i nt er -

act i on are def ormed by buoyancy f orces. The ver t i cal def ormat i on i s

approxi matel y gi ven by

AR = gtz 3)

wher e g = 9. 8 m S- 2 i s t he gr avi t at i onal accel er at i on. Dur i ng t he l at e f i r ebal l

evol ut i on t he f i r ebal l r adi us r eaches a maxi mum and sl ow y decl i nes t her eaf t er

whi l e the shock wave vel oci ty approaches the sound speed. The upward curvature

of the RFB + RSH l i nes i s a resul t of thi s behavi or . ) The maxi mum f i rebal l

r adi us i s desi gnat ed as RM I f t he buoyant def or mat i on exceeds a f ew per cent ,

t he hei ght - of - bur st anal ysi s suddenl y becomes mor e compl ex. Thi s buoyancy

regi me has been del i neated by the AR = 0.02 RM l i ne at the r i ght of f i gure 2.

The graph

determned f rom

di ameters. The

the burst hei ght

Iv. TEST DATA

i s used as f ol l ows: t he t i me of shock/ f i r ebal l i nt er act i on i s

the hi story of t he rat i o of the ver t i cal to hor i zontal

known yi el d i s t hen used t o i nt er pol at e bet ween t he cur ves and

i s read as hal f t he sum of t he t wo radi i .

We have anal ysed photographi c

t est s conduct ed i n Nevada f or whi ch

dat a f or seven U. S. atmospher i c

uncl assi f i ed yi el ds ar e avai l abl e

nucl ear

and one

Paci f i c t est . Al l were l ow mass ai r drops. The rel evant data for t h e seven

events w t h t he uncl assi f i ed yi el ds are gi ven i n Tabl e I . Al l had p= 1.OX1O-3

5


9/16

gcm 3. The hi st or i es of t he r at i o of t he ver ti cal and hor i zont al di amet er s ar e

gi ven i n f i gures 3 t hrough 9. For t he pur pose of t hi s paper we have m r el y

est i mat ed t he i nt er act i on t i me as t he t i me of a si gni f i cant , sust ai ned dr op of

t he di amet er rat i o. The range of t he est i mat ed i nt er act i on t i me t i ) f or each

event i s gi ven i n Tabl e 1,

The der i ved bur st hei ght s HD) ar e pl ot ted agai nst t he act ual hei ght s i n

f i gure 10. Cl ear l y, the error s are l ess t han 50 meters i n al l cases. The

rel at i ve error s are gi ven i n Tabl e I f or t he seven uncl assi f i ed events. Al 1

ei ght event s have er r or s l ess t han 20 per cent .

TABLE I

THE SEVEN NTS AIR DROP EVENTS EXAM NED I N THI S STUDY

NAME

GRABLE

FI ZEAU

CLI MAX

TS-DOG

BJ-EASY

BJ-CHARLIE

WASP-PRIME

T&-15

11.4

62.8

19

31

14

3

7160

152

407

317

401

345

222

65

68

102

119

128

143

157

s

. 075- . 1

. 08- . 1

. 3- . 45

. 4- . 5

. 3- . 5

. 45- . 5

. 4- . 5

518

490

689

543

599

511

375

180

180

415

350

368

328

224

HD- H

T

. 13

. 18

. 02

.10

-.08

-.05

-.01


10/16

v. REFI NEMENTS

Thi s si mpl i st i c di scussi on of shock/ f i r ebal l i nteract i ons has l ed t o

f ai r l y accurate burst hei ght esti mati on f or ei ght nucl ear t est s. Some f i ne

t uni ng of the model may i mprove the resul t s and/ or i ndi cat e present l y

uni dent i f i ed l i mtat i ons.

1 For bur st s whi ch suf f er gr ound i nt er act i on bef or e m ni mum t i me, ~l N i s

a f unct i on of burst hei ght . Cal cul at i onal wor k has been done t o def i ne t he

var i at i on w th hei ght f or a ser i es of burst s w th the I VY- KI NG yi el d 540 kt ).

These r esul t s ar e pl ot ted i n Fi gur e 11. The anal ysi s r out i nes f or det er m ni ng

bur st hei ght shoul d i ncl ude an i t er at i ve scheme t o account f or modi f i ed yi el d

est i mates at l ow burst hei ghts.

2) Numer i cal test s of exi st i ng photographi c data must be made to determne

t he ef f ect s of f i ni t e resol ut i on el ement s and t hreshol d sensi t i vi t i es on t he

resul ts. We i magi ne t hat there i s a t radeof f between f i ne resol ut i on and

accur at e di amet er r at i o measur ement s on t he one hand and r educed i nt egr at i on

t i mes w t h coar se gr i ds on t he ot her . We i ntend to perf orm computer si mul ati ons

of sel ected data f rames to quant i f y these ef f ect s, and to determ ne the

l i m t at i ons i mposed by t he f r ame t i me r esol ut i on of t ypi cal i magi ng devi ces RJ

1/ 30 s) .

3) Si m l ar l y, at mospher i c at tenuat i on and decr easi ng i nt ensi t i es w t h

i ncreasi ng range may i ntroduce errors. Fi r ebal l s whi ch suf f er i nt er act i on af t er

a few t i mes second-maxi mum do not have par t i cul ar l y wel l def i ned edges. Unl ess

properl y tr eated, range and hei ght -of - burst er ror s may be i nt roduced whi ch are,

themsel ves, f uncti ons of range.

4) The speed of def or mat i on dur i ng t he ear l y st ages of t he i nt er act i on i s

a f unct i on of yi el d and hei ght - of - bur st . Anal ysi s of t hi s mot i on may pr ovi de an

i ndependent bur st hei ght i ndi cat or al t hough we ant i ci pat e t hat i t w l l not be

par t i cul ar l y sensi t i ve. Def i ni t i on of scal i ng l aws w l l requi r e anal ysi s of

t wo- di mensi onal cal cul at i ons.

Fi gur e 12 r epr esent s t he anal ysi s f l ow i n a hypot het i cal syst em i ncl udi ng

an i t erat i ve consi derat i on of t he ef f ect s of hei ght - of - burst on ~l N. We are

cur rent l y i mpl ement i ng such an anal ysi s scheme t o t est t he val i di t y of t hi s

hei ght- of - burst determnati on techni que.

7


11/16

141 1I I 1 8 1 I I 1 I 1 1 I I I I 1 I I II .3

1.2

11

uPSHOT-KNOTHOLE /GRABLERecord 1798 I (Original)

1.1

1.0

0. 9 :

0. 8 ~A 0. 7 .

, ,**9

0. 6 b. ~0. 5

tt

0. 4 , t 18/ 22m0a

0. 3 tB/ 5

0. 20.1

t0.0 I 1 I 1 1 I 1 1 1 1 I 1 1

1 1 1 1 1 1 0. 2 0. 4 Of i 0. 8 1.0 1. 2 1. 4 1. 6 1. 8 2. o

TIME (StlC)

Fi g. 3

Rat i o of t he ver t i cal t o t he hor i z ont al di amet eras a f unct i on of t i me f or GRABLE. GRABLE was a 15 ktexpl osi on 160 m above the ground surface at the NevadaTest Si t e NTS). t2~X i s the cal cul ated t i me ofsecond thermal maxi mumwhi l e tB, the buoyancy t i me, i sgiven by R t2AX) = g t?.

RExamnati on of the GRABLE

phot ogr aphs s ows i ni t i al i nt er act i on at about 0. 07 sal though no substanti al deformati on occurs unti l about0. 1 s.

: v~q

1.0 *:.

.0.9 :

0.8 :

A 0.7 ttR

0.6

0.5

0.4

0.3

0.2I

. . .

.. .

9

?

tfj/2

0.1

0.0 1 I I I I I 1 1 1 1 t I 1 1 1 1 1 I I 1 0.2 04 06 O. I .0 1.2 1.4 16 1.8 20

TI ME (see)

Fi g. 4

FI ZEAU was a 11. 4 kt expl osi on at 152 meter s. tRi s t he t i me of i ni t i al i nt er act i on det er m ned f r omvi sual i nspecti on of the photographi c records.

8


12/16

1.4 I I 1 I 1 1 I I I I I I I I I I f I I1.3

J1.2

t

UPSHOT-KNOTHOLE/CLIMAX1.1 Record 171081 (Originol)

1.0 &*.~

0.91 , .. -10.8

I

t= .A 0.7 .. .

0.6.

.* .*

0.5.**.

.

04 10.3

0.2

[

ft~/5

o. I

ttB/2

0.01 I I I t I I I I I I I I I I I I I I 10.0 04 0s

I1.2 1.6 2.0 2.4 2B 3.2 3.6 40

TIME see

Fig. 5

CLIMAXwas a 63 kt explosion at 407 m burst height.

14 I I I I I t 1 I 1 I r I r I I I I I I1.3

-1

A

I .2 -

1.1-

1.0-

0.9 -

0.8 -

0.7 -

0.6 -

0.5 -

04 -

0.3t

0.2t

TUMBLER-SNAPPER /OOG

Record 13382 (Pr int)..

.

.

I

. . .

c J 1 1 1 I2.4 2B

J3.2 3.6 4.0

TIME (WC)

Fi g. 6

TS- DOG was 19 kt expl osi on at 317 m burst height.

9


13/16


14/16

1.4 I 1 I I I I 1 I I I i 1 I I 1 1 I I 11.3 -

1.2- TEAPOT/ WASP-PRIME

1.I - Record 29339 (Print)

1.0 - .0.9 -

**

0.8 - . 9 .9 . .A 0.7 - . **.* . . .

**06 - 9.

0.5 -

0.4 -

0.3 -

0.2-

0.1-

0.0 1 t 1 1 1 1 1 1 1 I I 1 1 1 I I I to 0.4 0.8 I .2 1.6 2.0 2.4 2B 3.2 36 40

TIME (StiC)

Fi g. 9

WASP PRI ME was a 3 kt expl osi on at 222 m burst hei ght .

DERIVEOHEIGHT

900. I I I I

800 -

700 -

600 -

500 -

400 -

1300 -

200 -=

100 -

00 100200300400500600700 60090JJ

BURST HEI GHT

Fi g. 10For each of the seven Nevada test studi ed and onePaci f i c Test DOM NI C AZTEC) the deri ved hei ghtsagr ee wel l w t h t he act ual hei ght s. The r ange f oreach test i ndi cated the hei ght uncertai nty producedby t he uncer t ai nt y i n t he t i me of i nt er act i on.

11


15/16

.

[

ed 12 A3900- woo ABdll k1600-5600~9d 10 A5600- 6800 ~Bd9 A8800-a240a9d 8 A8240- I oooo~

Bd 12

II

10

9

8

I 200 m 400 500

Burst Hei ght m

Fi g. 11

Ti me of thermal mni mum tM N) i n Vi3riOUSwavel ength bands cal cul ated for 540 ki l otonexpl osi ons at vari ous al t i tudes.

12


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fireball 2

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