High temperature stable detonators

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DISCLAIMER This report was preparedas an account of work sponsoredby an agencyof the United Stales (ksvemment Neither the United States Governmentnor any agencythereof, nor asryof their employees,makesJny warranty, expressor implied, or assumesany legalliabilityor responsibilityfor the accuracy.complctcrtcss.

or usefulnessof any information, apparatus, product, or processdiaclo=d, or representsthat its use would not Infringeprivatelyowned rights Reference herein to any specificcornrrrerciafproduct proce= or sertice by trade name, trademark, marrufactuser,or otherwise,does not nec-y constitute orimply its endorsement, recommendation, or favoring by the United States Government or any agency thereof llrc views and opiniona of authors expressed herein do not necessarily state or reflect thoserrf theLIniled

States Governmentor any agencythereof.

UC-45 Issued: October 1984

High-Temperature-Stable Detonators

Robert H Dinegar

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DETONATORS

RobertH Dinegar

ABSTRACT

stable detonators involve using HMX, KP, HNS, and PYX

explosives The test.devicesemployboth

hot-wireflying-plate and slappermodes of operation Hot-wiredetonators

using HMX as the donor explosive,with HMX, KP, and HNS as

the intermediateacceptormaterialand HNS as the booster

225°C Very limitedsuccesswasachieved using PYX

explo-sive in a few experiments The program of investigation

hot-wiredevice functioningin the DDT mode of operation

explosive has been initiated to detonationby low-energyslapper

foils

The developmentof a detonatorthat will withstandelevatedtemperatures

is governedby both the temperatureregimedesiredand whetherthe explosives that are stable at those temperaturescan be initiatedto detonation In addition,it must also be determinedthat practicaland realizableamountsof

Two methodsof explosiveinitiationare consideredin this report,i.e., hot-wire and slapper-foil In the first, a small wire in contactwith an

explo-sive (donor)is ignited,and the gases that are producedrupturea metallic disc The flyingplate formed strikesa second explosive(acceptor)that is initiatedto detonation In the second,the slappersystem,the rapidpassage

process drives material coveringthe foil into an explosive,whichis

ini-tiated to detonation A

functioning

The test device is

fractionof 1 J of energy is sufficientfor proper

mode of operation Two parallelNichromeV bridgewires,0.05 mm in diameter

densityof 1.6 g/cm3

/

waster Explosive

Hat”

2

““’S-=-.IVNM—

Steel

Acceptor Explosive

\ ,.,

-.:,

~L:;::[p’o’e

>. Al Disk Becomes

‘Flying Plate”

9EiiRi’rse: ,

Steel J - J’///i

~Ta Firing Unit

because0.2 mm of an overall

6061-T6A1 The flyerdesignis called“Top l.O-mm-thickshim fits snugglydown inside

the flyer barrel forming a “Top Hat.” The flyer barrel has a diameterof 2.5 mm and is 7.0 mm in length The acceptorcharge holder has the same dimensions Both parts are made of 303 stainlesssteel and are screwedto-gether The boosterpellet is confinedin a brass hexagonalring glued onto the end of the acceptor charge An aluminum witness block (usually2024 Dural) is glued onto the metal ring that containsthe boostercharge

maxi-mum temperatureat which we have done experimentsis 250°C The majorityof the testing in hot-wireassemblieswas done with HMX explosive KP and HNS were looked at in some detail; the daLa on PYX were sparsebecauseof its relativeinsensitivity.The specificsurface(S.)of the explosivesdiffered HMX used in the donor and the acceptorwas 8500 and 3450 cm2/g,respectively

KP donorpowderwas 7600 cm2/gand the acceptorexplosive2350 cm2/g HNS was

balls to an S of about 30 000 cm2/g for this testing

The donor explosiveswere all fired at 10 A or more This is far above

currentvalue is only about twice the thresholdvalue

Figure2 shows the slapperdetonator Electricalenergyfrom an external source is depositedextremely rapidly in a metallic foil of the order of 0.01 mm thick There is a rapid productionof vaporizedmetal and plasma

than 0.1 mm thick placed againstthe bridge down a barrel a few tenths of a millimeterin length The impact of the rapidly moving material upon an attachedhigh-densityexplosivepellet providesenoughenergyto initiatethe explosiveto detonation

~~-potassiumpicrate

~~ 2,6-bis(picrylamino)-3,5-dinitropyridine

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I

enough to generatea usable pressurethat forms flying

PYX decomposesjust plates from aluminum discs The flying plates have energiesgreat enough to dent both 6061-T6A1

will work, but whether the probabilityof an explosiondevelopinginto a detonationis high enough for practicaluse remainsto be seen Extrapolation

min-utes for all-KPdetonators

donor material,HNS decomposedupon hot-wireheating to form a flyingplate but not with sufficientenergy to reactKNS or KP at 1.0 and 1.2 g/cm3 in the 4

acceptorbarrel As an acceptormaterial, initiatedby a flyingplate driven

by anotherexplosive,it performsmuch better

of severalhours into the 200°C region It is certainlyworth seeingat how high a temperatureit will function(TableI)

TABLE I

AT ELEVATEDTEMPERATURES

NUMBER

2

2

2

2

2

1

1

1

6

9

7

EXPLOSIVE

HNs-1

II HNs-1 Km-l

f!

S = 13000 cm2/g HNs-1

It HI/s-l

t! s = 3450 HNs-1

HNs-1

CYLINDRICAL DENT VOLUME (cm3) 0.69a o.39a o.47a o.3oto

0.32t0.01 0.29

o.44a o.49a 0.29t0.02 0.32t0.04 0.32t0.04

TEMPERATURE (’JC) + 74 +100 +150 +200

+200 +225

+100” +150 +150 +200” +225

a6061-T6Alwitnessblock;all others2024 Dural

HMX donorswill initiateHMX, KP, andHNS-1 acceptorexplosivesto deto-nation by driving flying plates withoutmuch difficultyup to +150°C Fol-lowingare detailsof the resultsof all-HMXdevicesat highertemperatures

failedto ignitedue to an open bridgewire One donor did not shear the flyer plate, and one threw the flyer only halfwaydown the barrel Althoughsome engineeringproblems still seem

Its auto-ignitiontime appears

to exist, hot-wiredetonatorsusing HMX as appearusableat 200°C

to be less than 30-45 minutes The solid

plate that was recoveredat the end of the flyerbarrel The gases evidently causedbridgewiresto come loose from their welds in severalcases The HMX

of low density (-1.2 g/cm3) in the acceptorbarrelsublimedcompletelyin two

dent in the witnessblock

explodedspon-taneouslyat differenttimes of heating (less than 30 minutes) No evidence

of initiationto detonationwas observed

W Hemsingand I M Garcia (M-7)have foundthat PYX can be detonatedin slapper-typedetonatorsat fairly low energylevels(~0.3-Jstoredenergy)at ambient temperature At high temperatures,the required energy should be significantlylower Therefore,in principle,a detonatorcapableof with-standing+300°C is at hand We are endeavoringto make a

pro-vidingthe cryogenicprotec~ionneededby present-dayfiringsystemsin under-groundwork

REFERENCE

Ex-plosives,” Los Alamos National Laboratoryreport LA-5829-MS(January 1975)

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