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DISCLAIMER
Thisreport waspreparedas an account of work sponsoredby an agencyof the UnitedStales (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 hereinto any specificcornrrrerciafproduct. proce=. or
sertice by trade name, trademark,marrufactuser,or otherwise,does not nec-y
constitute or imply its
endorsement, recommendation,
or favoring by the United States Government
or any agency thereof.
views and opiniona of authors expressed herein do not necessarily state or reflect those
States Governmentor any agencythereof.
rrfthe LIniled
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LA-10172-MS
UC-45
Issued: October 1984
High-Temperature-Stable Detonators
Robert H. Dinegar
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LosAlamosNationalLaboratory
LosAlamos,NewMexi..87545
.
HIGH-TEMPERATURE-STABLE
DETONATORS
by
RobertH. Dinegar
ABSTRACT
Current experimentsin the area of high-temperaturestable detonators involve using HMX, KP, HNS, and PYX
explosives. The test.devicesemployboth hot-wireflyingplate and slappermodes of operation. Hot-wiredetonators
using HMX as the donor explosive,with HMX, KP, and HNS as
the intermediateacceptormaterialand HNS as the booster
pellet,were successfullyfired at temperaturesas high as
225°C. Very limitedsuccesswasachieved usingPYX explosive in a few experiments. The program of investigation
also calls for the developmentof a high-temperature-stable
hot-wiredevice functioningin the DDT mode of operation.
PYX explosive-a truly high-temperature-stable
explosive-has been initiated to detonationby low-energyslapper
foils.
-.
I. INTRODUCTION
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 determinedthatpracticaland realizableamountsof
energywill sufficefor the properfunctioningof the system.
Two methodsof explosiveinitiationare consideredin this report,i.e.,
hot-wire and slapper-foil. In the first, a small wire in contactwith an
explosiveis heatedby the passageof currentof the orderof 1 A. The explosive (donor)is ignited,and the gases that are producedrupturea metallic
disc. The flyingplate formedstrikesa secondexplosive(acceptor)that is
initiatedto detonation. In the second,the slappersystem,the rapidpassage
of an electriccurrentthrougha foil vaporizesit. The resultantexpansion
process drives materialcoveringthe foil into an explosive,which is initiated to detonation. A fractionof 1 J of energy is sufficientfor proper
functioning.
11. EXPERIMENTALDETAILS
A. Hot-WireDetonators
The test device is shown in I?ig.1. It functionsin the flying-plate
mode of operation. Two parallelNichromeV bridgewires,0.05 mm in diameter
and 2.5 mm long, are resistance-welded
to FeNi alloyelectrodesembeddedin a
compressed-glass
header. The explosivechargeholderis made of Teflonand is
4.4 mm in diameterand 4 mm long. A chargemass of 100 mg gives a loading
densityof 1.6 g/cm3.
waster
/
—
““’S-=-.IVNM
\
Explosive
Acceptor Explosive
,.,..
-.:,
~L:;::[p’o’e
Al Disk Becomes
>.
‘Flying
Plate”
Steel
9EiiRi’rse:..,...
Steel
J. - J’///i
~Ta
Firing Unit
Fig. 1. Flying-plateassembly.
The flying-platematerialis 6061-T6A1. The flyerdesignis called“Top
Hat” because0.2 mm of an overall l.O-mm-thickshim fits snugglydown inside
2
the flyer barrel forminga “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 screwedtogether. The boosterpellet is confinedin a brass hexagonalring gluedonto
the end of the acceptor charge. An aluminumwitness block (usually2024
Dural)is gluedonto the metal ring that containsthe boostercharge.
HMX,’”
KP,-~*HNS,~ and PYXl_~explosiveshave been investigated.The maximum 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
the fine-particlevariety (lINS-l)
with the same S. value of 13 000 cm2/g in
both the donor and acceptor. Large-particle
PYX was wet-groundby porcelain
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
the 1-A threshold-current
value for HllX,KP, and HNS. Since PYX explosive
requiresa larger-diameter
bridgewire(0.127mm vs 0.05 mm) for ignition,this
currentvalue is only about twice the thresholdvalue.
B. SlapperDetonators
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.
The high pressureaccelerateshigh-tensile-strength
insulatingmaterialless
than 0.1 mm thick placed againstthe bridge down a barrel a few tenths of a
millimeterin length. The impact of the rapidly moving materialupon an
attachedhigh-densityexplosivepelletprovidesenoughenergyto initiatethe
explosiveto detonation.
* l,3,5,7-tetranitro,
1,3,5,7-tetrazacyclooctane.
~~-potassiumpicrate.
+ 2,2’, 4,4’ , 6,6’ hexanitrostilbene.
~~ 2,6-bis(picrylamino)-3,5-dinitropyridine.
!,
.
:.
*
Fig. 2.
.
.
‘.
. ..
I
Slapperdetonator.
III.EXPERIMENTALRESULTS
A.
Hot-WireDetonators
1. PYX. At room temperature,+75,
and +150°C, PYX decomposesjust
enough to generatea usablepressurethat forms flyingplates from aluminum
discs. The flying plates have energiesgreat enough to dent both 6061-T6A1
and 2024 Dural witnessblocks. The system is also sufficientlyenergeticto
ignite PETN acceptor/boosterpellet combinationsto violent deflagration.
2. KP.
KP donors at elevated temperaturesof +75 and +lOO°C caused
explosionsof larger-particle
KP in the acceptorbarrelin 12/14shots,one of
which detonated. The success shows that the all-KP,flying-platedetonator
will work, but whether the probabilityof an explosiondevelopinginto a
detonationis high enough for practicaluse remainsto be seen. Extrapolation
of time/temperature
data on KP indicatesa survivaltime at 300°Cof 30 minutes for all-KPdetonators.
3. HNs. HNS is a very heat-stablematerial. Its melting point is
1 As a
-3150C, and it has an excellentvacuum-thermalstabilitybehavior.
donor material,HNS decomposedupon hot-wireheatingto 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.
4. HMx. While not truly a high-temperature
explosivein the same sense
as KP, HNS, or PYX (certainly),HMX has a meltingpoint almost 250°C above
room temperatureand a reasonablevacuum-thermal
stabilityfor periodsof time
of severalhours into the 200°C region. It is certainlyworth seeingat how
high a temperatureit will function(TableI).
TABLE I
HIGH-TEMPERATURE,
HOT-WIREDETONATORPERFORMANCE
AT
ELEVATEDTEMPERATURES
NUMBER
DONOR
2
2
2
2
KP
S.=8500
cm2/g
!1
2
II
1
f!
1
1
6
It
9
7
EXPLOSIVE
ACCEPTOR
t!
!!
S. = 2350
cm2/g
!t
HNs-1
S. = 13000 cm2/g
s. = 3450
!!
cm2/g
!!
It
t!
BOOSTER
CYLINDRICAL
DENT VOLUME
(cm3)
PETN
0.69a
ins-l
HNs-1
HNs-1
o.39a
o.47a
o.3oto
Km-l
0.32t0.01
+200
HNs-1
0.29
+225
HI/s-l
o.44a
+100”
HNs-1
HNs-1
o.49a
+150
+150
HNs-1
HNs-1
a6061-T6Alwitnessblock;all others2024 Dural.
0.29t0.02
0.32t0.04
0.32t0.04
TEMPERATURE
(’JC)
+ 74
+100
+150
+200
+200”
+225
HMX donorswill initiateHMX, KP, and HNS-1
acceptorexplosivesto deto-
nation by driving flying plates withoutmuch difficultyup to +150°C. Followingare detailsof the resultsof all-HMXdevicesat highertemperatures.
a. Temperature= 200”C. Seven of ten detonatorsfunctionednormally.
The detonatedHNS-1 boosterpellet gave good witness-block
dents. One device
failedto ignitedue to an open bridgewire.One donordid not shearthe flyer
plate, and one threw the flyer only halfwaydown the barrel. Althoughsome
engineeringproblemsstill seem to exist, hot-wiredetonatorsusing HMX as
donorand acceptor-barrel
chargesappearusableat 200°C.
b. Temperature= 225°C. At this temperatureHMX is basicallyunstable.
Its auto-ignitiontime appears to be less than 30-45 minutes. The solid
decomposedpartially,and the pressurebuildupspontaneously
burst the flyer
plate that was recoveredat the end of the flyerbarrel. The gasesevidently
causedbridgewiresto come loose from their welds in severalcases. The HMX
of low density (-1.2g/cm3) in the acceptorbarrelsublimedcompletelyin two
assemblies. Severalothersshowedtypicalbrownish-colored
partialdecomposition of the HMX. One device fired spontaneouslyand gave a good (average)
dent in the witnessblock.
Temperature= 250°C. Six detonators“cookedoff” and explodedspontaneouslyat differenttimes of heating (less than 30 minutes). No evidence
c.
of initiationto detonationwas observed.
B. SlapperDetonators
W. Hemsingand I. M. Garcia (M-7)have foundthat PYX can be detonatedin
slapper-typedetonatorsat fairlylow energylevels(~0.3-Jstoredenergy)at
ambient temperature. At high temperatures,the required energy should be
significantlylower. Therefore,in principle,a detonatorcapableof withstanding+300°C is at hand. We are endeavoringto make a high-temperaturecapablefiringsystem that will avoid the complications
associatedwith providingthe cryogenicprotec~ionneededby present-dayfiringsystemsin undergroundwork.
REFERENCE
1.
6
John F. Baytos,“High-Temperature
Vacuum ThermalStabilityTests of Explosives,”Los Alamos National Laboratoryreport LA-5829-MS(January
1975).
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