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Dany
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Detonation Velocity of organic explosive cannot exceed 11 Km/s
In 2 separate interesting article published by Pepekin et al. in 2007 and 2008, they came to an important conclusion that detonation velocity
of an organic explosive cannot exceed 11km/s. Thermochemical calculation shows that the limiting velocity of powerful, dense explosive is almost
reach. These results are supported by experimental findings on synthesized powerful explosive like CL-20 (Dcj=9.9 Km/s) and
dinitrodiazenofuroxane (Dcj=10 Km/s) (these detonation velocity are obtained at crystal density of the two explosive). Also, in a second
article, Pepekin et al., found a simple corrolation between impact sensitivity (given as critical pressure Pcr) and the volumetric
heat of explosion (which is the density * heat of detonation, in cal/cm3). the correlation is obtained after a study on a number of high
explosive with negative oxygen balance. what is interesting is that when extrapolating the Pcr down to 1 bar (ambient atmospheric pressure)
a value of 4100 cal/cm3 is obtained which mean that an explosive having this volumetric heat of explosion will spontaneously explode (it
cannot exist at normal pressure). comparing the value of 4100 to values of experimentally synthesized explosive yield a value of 3750
cal/cm3 (for dinitrodiazenofuroxane). dinitrodiazenofuroxane is highly sensitive and is considered a primary explosive. The conclusion, in
the second article also support the fact that detonation velocity of 11 km/s are the limiting VoD of organic explosives. any increase of volumetric
heat of explosion will lead to a compound with higher Dcj but having an extreme sensitivity to external stimilus (having very low
Pcr) Although a general correlation is observed between power of an explosive materials and its sensitivity, some compounds may deviate.
Octanitrocubane and TKX-50 (recently synthesized by Klapotke et al.) are example of two powerful explosive materials but with moderate
sensitivity. These conclusions, don't include homoleptic polynitrogen explosive which in theory are more dense and performs better than organic
energetic materials. Unfortunately, apart from pentazolium cation, no synthesis have been reported in open literature for other homoleptic
polinitrogen species, due to their high reactivity and positive enthalpy of formation which lead to decomposition to the stable molecular
N2.
Any discussion on the topic is welcomed!
Dany.
The two studies of Pepekin et al. can be dowloaded from the following links:
Attachment: Propellant performance of organic explosives and Their Energy Output and Detonation Velocity Limits.pdf (615kB)
This file has been downloaded 1278 times
Attachment: Initiation of Solid Explosives by Mechanical Impact.pdf (174kB)
This file has been downloaded 1181 times
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franklyn
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Those are very good articles
I'm sure
PHILOU Zrealone will want to comment on this also.
This may hold valid for a compound made of a carbon containing molecule ,
with conventional chemistry but I would not bet the farm on it. If speed of
reaction is limited so that propagation time does not exceed some benchmark
it does not prevent more energy from being contained in the same volume or
restricting the pressure which might be generated applying means other than
chemical bonding alone. The velocity of detonation is only a property that serves
to indicate overall performance , the detonation pressure being the important
one. The highest speed of sound in any material is that of Beryllium , 13 km/s ,
and that's not an energetic wave , so there is ample room for improvement.
High nitrogen content polymers are sure to exceed any projected cap.
Metastable materials produced by the action of extreme isostatic compression
such as polycarbonyl , or hydrogen metal which as yet remains a gleam in the
eye , are not accounted for as limiting conditions. Polycarbonyl monomer :
is metastable at ambient conditions and is synthesized by compressing liquid
carbon monoxide at pressures exceeding 5GPa , that's 50,000 atmospheres.
www.i-b-r.org/docs/polycarweb.pdf#search="polycarbonyl"
http://pubs.acs.org/doi/abs/10.1021/cm0524446
Carbon dioxide also polymerizes remaining stable so it could be mixed with
nano particles of magnesium and form a very dense explosive compound.
http://prl.aps.org/abstract/PRL/v83/i26/p5527_1
www.pnas.org/content/106/15/6077
www.esrf.eu/UsersAndScience/Publications/Highlights/1999/che...
www.sciencedaily.com/releases/2009/03/090325132901.htm
This same methodology can be applied to force hydrogen into , for example
carbon nano tubes contained as the fuel in an oxygen rich energetic compound.
www.sciencemadness.org/talk/viewthread.php?tid=23314#pid2743...
www.sciencemadness.org/talk/viewthread.php?tid=23314#pid2744...
The included hydrogen is not chemically bonded so does not reduce the energy
available and also does not increase the volume of the matrix. The volume of
explosion however will be.
An explosive device can be built in which aluminum foil which serves as fuel
doubles as the plate of a capacitor so that the dielectric explosive can also
provide some energy in the form of neutralized static electric charge. It is in
practice at least 1000 times less than what is available from the chemical
bonding. This however is scale dependent and there is no reason it cannot
be done at a nanoscale. Ionic salts achieve high density by arrangement in
a lattice of alternating charged ions. Organic molecules known as electrides
form positively and negative charged components. In the same way two
different neutral energetic molecules could be induced to acquire charge much
the same as explosive ionic salts of heterocyclic nitrogen molecules. The binary
compound would in effect be charged as if a capacitor , increasing the energy
content of the material. Some radical energic materials are discussed here _
www.dtic.mil/dtic/tr/fulltext/u2/b088771.pdf
www.dtic.mil/dtic/tr/fulltext/u2/750554.pdf
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Dany
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Hello Franklyn,
I don't think that the example of Berylium is true. Although soud speed of beryllium is High (13 Km/s), the metal cannot support detonation wave by
its own. so 13 km/s will not be exceeded. A high explosive detonating in beryllium tube for example will send a precursor wave in beryllium tube at
soud speed of beryllium ahead of the detonation wave.
Extended CO solid are interesting but the do not offer much energy. in an article entitled "Extended CO Solid- A New Class of High Energy Density
Material" the authors mentioned that the polymeric CO solid had an energy comparble to Organic explosive 1-3 Kj/g-nothing special about these polymer-
plus they are sensitve and unstable at ambient pressure.
PS: the authors in the mentioned article committed a mistake by saying in page 9 the following "Furthermore,
p-CO could be synthesized in carbon foam to reduce its sensitivity, similarly to the way how highly sensitive TNT was developed into dynamite." Indeed
the sensitive explosive is Nitroglycerine and not TNT...
I will added to your exotic HEDM articles, a conference presented by Dr Betsy RICE from the U.S Army Research Laboratory. In this conference Dr RICE
talk about energetic material and she mentioned nano diamond as possible new HEDM. nano diamond possess high strain energy, this strain energy can be
relased so fast to the surrounding, just like a detonation process.
http://www.youtube.com/watch?v=GftyIvDvqpw
https://e-reports-ext.llnl.gov/pdf/312891.pdf
Dany.
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Microtek
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When I see this kind of statement (the conclusion of the articles mentioned in the first post), I always think of all the times something similar has
been said in the past. These spring to mind:
"X-rays will prove to be a hoax."
-- Lord Kelvin, president, Royal Society, 1895
"Radio has no future."
-- Lord Kelvin
"Heavier than air flying machines are impossible."
-- Lord Kelvin
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DubaiAmateurRocketry
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Nice, is it possible for non organic to exceed over 11kms ?
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Dany
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Many theoretical studies mention that Homoleptic polynitrogen explosive, are denser and more energetic than organic explosives. Christe K.O. who
synthesized the linear pentazolium N5+ cation predict that this cation detonate at VoD=12 Km/s, indeed doubts still exists in
the absence of measured VoD.
Dany.
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Ral123
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Why is there so much talk on all nitrogen explosives and stuff, when fluorine and aluminium are still not a common part of an explosive molecule. Why
we associate nitrogens with energy when some generic oxidations like O2-H2 are more energetic.
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Dany
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Quote: Originally posted by Ral123  | | Why is there so much talk on all nitrogen explosives and stuff, when fluorine and aluminium are still not a common part of an explosive molecule. Why
we associate nitrogens with energy when some generic oxidations like O2-H2 are more energetic. |
Hello Ral123,
It is true that reaction like O2-H2 are very energetic but their detonation speed cannot exceed the VoD of powerful organic explosive. One of the
principle cause is their low density even in condensed state. Fluorine as a difluoroamino group (the fluorine analogue of nitro group) are promising
explosophoric noiety for HEDM, but their performance slightly increase that of oxygen analogues and are difficult to synthesis. Aluminium and other
reactive metals, although very energetic when react with air for example, do not have high VoD. an example of metal containing energetic materials are
nano-thermite. nano-thermite possess siognifically higher energy content than organic HEDM, but the detonation speed of nano-thermite is of the order
of 3 Km/s. the reason for this slow detonation wave is that the reaction in thermite is limited by slow process such as diffusion and other transport
mechanism.
Dany.
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TheBackyardScientist
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"The question is whether you're going to be able to get a long enough look at the material before it realizes its dream of turning into an expanding
cloud of hot nitrogen gas."
A nice article about C2N14.
http://pipeline.corante.com/archives/2013/01/09/things_i_won...
If anybody can get the paper here it might state the VOD.
http://onlinelibrary.wiley.com/doi/10.1002/anie.201100300/ab...
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Dany
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Hello TheBackyardScientist,
I know about this compound, beside it's high sensitivity, calculated detonation performance for this compound are Dcj=8960 m/s and
Pcj= 339 Kbar. With this detonation parameter C2N14 is inferior even to HMX.
you should look at this paper by Klapotke et al.. This compound is a promising new HEDM having detonation properties equal to epsilon CL-20
and a sensitivity close to TNT
http://www.sciencemadness.org/talk/viewthread.php?tid=25484
Dany.
Attachment: C2N14- An Energetic and Highly Sensitive Binary Azidotetrazole.pdf (403kB)
This file has been downloaded 1194 times
[Edited on 11-8-2013 by Dany]
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PHILOU Zrealone
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Hi Franklyn and all the others  ,
I found those two articles interesting but I find that some things are a bit categorical and that they make maybe too fast conclusions...on a little
amount of chozen molecules... not counting the fact that they disgard two of them saying that the reason is not clear why they behave so bad in their
predictions...pretexting the probable influence of the OB.
To my feeling with chosen molecules you can make the curve go where you want it to go. Maybe it is a pure hazard or a bad luck but I think they missed
a lot by taking into account such diverse molecules into too little amount.
By analysing families of compounds one find very different results and I will try to explain this later down this tread.
I think that those articles speaks about propellant and HE but as most of us do know, HE and propellants are not aimed to be the same.Their wished
effect and nature of their properties are not meant to be identical...
1°)HE are by nature meant to break and destroy a target... the speed of detonation is very important in that effect mostly by contact or close
viccinity to it, the brisance and detonation wave are primordial for those wished properties.
To temper sensitivity one uses additives in a few %. The higher the density the best.
2°)Propellants are meant to propulse a projectile or a recipient (shuttle)...this precludes the use of HE at full detonating power. No shuttle could
withdraw the inner detonation wave of a HE...at least without a very hard and heavy armouring what is contradicting with inherent shuttle design
principle. So the power must be strongly tempered by addition of inert materials, dillutors, inhibitors or plasticizers.
Dillution (by air or vaccuum) can simply be the introduction of limited amounts of propellant into the combustion chamber.
Too fast the burning rate and the canon or shuttle may crack/burst/explode or detonate. Too hot a burning flame and pressure and the canon or shuttle
will deform or be brought to softening or melting loosing integrity.
This explains why ballistic industry tries to get low temperature burning powders. The powder form allows dillution of the explosive by air but also
to give desired shape for specific burning rate/properties and sometimes surface treatment to slow down some process.
One of the main aspect that is not listed in the article on propellants is the need for low molecular weight output products (exhaust)...thus hydrogen
is usually a must in those explosives. H2 is the best exhaust molecule, then comes HF, H2O, CO and N2, O2 and at least CO2 what is eavier and has the
lowest quadratic speed. In fact H2 can be used to dillute up to 5 times a mix of H2 and O2 without arm...it reduces the risk of detonation, and
increases the specific impulse what is not mentionned also into the article and stil a major aspect of the rocketry theories. NH3 and N2H4 are very
good because they are hydrogen carriers and poduces some H2, N2 in the exhaust they are also more handelable than H2 in a tinier volume (less eavier
tank, less insulation needed) thus more aerodynamic shuttle... Carbon containing molecules are less interesting (except maybe methane because of its
hydrogen content) because lower Specific Impulse are acheived.
Long time ago I had the feeling and good intuition (by compulsing explosive stuffs databases) that hydrogen-free explosives was a way to acheive
higher VODs and here they explain why ... and this is fine!
The explanation for the insensitivity of TATNB (Triaminotrinitrobenzene) is not only what they exposes but also in great part because of the reaction
of transformation into another molecule they speak about what is Benzotrifuroxan... this processus is endothermic and catch a good deal of the impact
energy also in the process water is lost what tempers the heat generated...
(-C(-NH2)=C(-NO2)-)3 <--> (-C(=NH)-C(=N(O)-OH)-)3
(-C(=NH)-C(=N(O)-OH)-)3 <--> (-C=N-O-N(O)=C-)3 + 3H2O (the underlining is for the junction of the two carbons via sp3 bonding).
As expected the breaking of the aromaticity of the benzen ring (what is stabler) giving exo-benzenic sp2 bonds cost a lot of energy (endothermicity)
and gives more unstability to the resulting benzotrifuroxan.
I disagree with their conclusion that when plotting rho*Qmax you get a curve line that implies that above a certain value the compound is too unstable
to exist.
All explosives are a compromise between a molecule and its stabler decomposition products... the weakest link between the two is the activation energy
barrier... and they don't seem to take this really into account the activation energy barrier is strictly dependant on the molecule structure. Some
molecule have a low Ea vs Ed (Energy of decompositon (detonation)) while other have a higher one. A low Ea means a little external energy is needed to
go from the explosive molecule to the decomposition products in this process energy is released and if energy dissipation processes is insufficient it
can trigger the Ea of several viccinal molecules in an exponential fashion leading to explosion and detonation if the volume is big enough. By kinetic
rules the temperature increases the amount of molecules having enough energy to pass the energy barrier and reduces the amount of dissipating energy
modes. So Nitroglycerine (propantriol trinitrate ester) sample made by Sobero itself more than a century ago is stil integer and preserved at ambiant
temperature. There is a little decomposition happening (statisticaly a little amount of the molecules gather their energy so that a few get high
enough energy to pass the energy barrier...while the remaining molecules lower their energy) so this explains that the half life of NG is quite long
despite sensitivity (low Ea barrier). This is related to the "PETN halflife of 12 million years" tread you opened...
In their study of initiation of HE they took in account quite exotic molecules with inherently unstable explosophoric groups; the more you get such
explosophoric groups into the molecule, the more the power per volume unit and sometimes the higher the density but also, the more unstable the
molecule is. The initiation of such unstable "domino" or "card castle" molecules is triggered by the weakest link; very often a diazo group or
nitro-nitrite rearrangement.
If you start from known molecules of the same family kind you will notice that the weakest link is generaly of the same kind/order of magnitude.
Then increasing the density, the VOD and the brisance is only a matter of increasing the molecular weight, by increasing the molecular lenght.
Franklyn refers to that when implying that polymeric high nitrogen containing molecules might go above the 11km/s cap. Multimerisation paradoxally
decreases the sensitivity because the amount of vibrational energy dissipation modes increases (bending, stretching, twisting, rotations, flipping,
resonances,...).
To reach the 11km/s detonation wave with CHNO explosives, one would need to be over the 2,3 g/ccm (followig plotting of real HE datas) and over the
2,5 g/ccm (following empirical equations listed hereunder).
VOD (m/s)= 3810*(0,392+d)
P(kbars) = 2,5/1.000.000*d*VOD2
At d=2,5... 11018 m/s are reached and P= 758,7986 kbars.
I know those are approximations but they give ideas about the terra incognita /not wel explored or inexplored regio of >10 km/s VOD explosives.
Real data ploting gives more VOD dependance to density to display a slope of 4285 instead of 3810...thus the empirical formula underevaluates
apparently the reality...
To reach and surpass 2,3 or 2,5 g/ccm will be hard work but this seems feasible with extended polynitro polyaromatic ring because graphite has a
density of 2,35. The planar graphite leaflets (planar polyaromatic) are held together by pi stacking (what is a good way to increase density and lower
sensitivity) and introducing some nitrogen and oxygen into the molecule as nitrogroup already increases the density of aromatic compounds by a lot.
By example C6H6 (benzene) has a density of 0,8941 passing to naphtalene (C10H8) you get a density of 1,145...then adding an extracolladed aromatic
ring (anthracene C14H10) you go to 1,25...and with tetracene (C18H12) to 1,3. So by iterations you get a fully aromatic ribon.
I suppose you have noticed the already high density of those pure hydrocarbons?...yeah we were all told to school that hydrocarbons float on water
 .
I take as an example that familly with two NO2 per aromatic ring. If you consider the para-dinitrobenzene you already get to a density of 1,486 to
compare to the density of benzene.
If you consider the density of 1,4,5,8-tetranitronaphtalene, some list it to be 1,8-1,95...to compare with that of naphtalene.
Following you what would be the tendency for 1,4,5,6,9,10-hexanitroanthracene, 1,4,5,6,7,10,11,12-octanitrotetracene, and higher homologues?
Also you have to take into account the increase of oxygen balance at each step passing from the bad dinitrobenzene asymptotically with a high number
of colladed aromating rings to slighly better than the OB of TNB. This invariably means more power, more density, higher VOD, higher heat of explosion
but not extensively sensitive!
[Edited on 21-8-2013 by PHILOU Zrealone]
[Edited on 21-8-2013 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Dany
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Reply to PHILOU Zrealone
When you say "HE are by nature meant to break and destroy a target... the speed of detonation is very important in that effect mostly by contact or
close viccinity to it, the brisance and detonation wave are primordial for those wished properties." be careful of taking the detonation velocity as a
criterion to judge power of explosive. Detonation energy and pressure are more important when talking about brisance.
also you are saying that :"One of the main aspect that is not listed in the article on propellants is the need for low molecular weight output
products (exhaust)...thus hydrogen is usually a must in those explosives. H2 is the best exhaust molecule, then comes HF, H2O, CO and N2, O2 and at
least CO2 what is eavier and has the lowest quadratic speed. In fact H2 can be used to dillute up to 5 times a mix of H2 and O2 without arm...it
reduces the risk of detonation, and increases the specific impulse what is not mentionned also into the article and stil a major aspect of the
rocketry theories. NH3 and N2H4 are very good because they are hydrogen carriers and poduces some H2, N2 in the exhaust they are also more handelable
than H2 in a tinier volume (less eavier tank, less insulation needed)...Carbon molecule are less interesting because lower SI are acheived" first, the
author is treating the case of organic molecule and explosives so no need to mention the propulsion by hydrogen or other inorganic/cryogenic
propellant. second, the author is treating the propellant performance in term of accelerating metal plate (explosive material that accelerate metal
plate) and not the propellant that we know to burn in rocket chamber and eject gaseous product from the nozzle. In the 2 case the product of reaction
are different and depend on the local conditions. Anyway, here's an important article on the "misuse of detonation velocity"
Dany.
Attachment: About the Misuse of the Detonation Velocity for the Characterization of High Explosives.pdf (802kB)
This file has been downloaded 1039 times
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AndersHoveland
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I would guess that a possible way to exceed this limitation might be to use boron compounds with -SF5 groups, possibly even pentaborane
mixed with liquefied SF6 under pressure.
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Dany
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Reply to AndersHoveland
Reply to AndersHoveland
it is not true that fluorine and boron containing compound are advantageous over normal C-H-N-O organic explosive for the following reason: the
detonation of boron containing explosive generate complex high molecular weight detonation products like BF3 and B2O3
which also have high degree of freedom (more degree of freedom than normal detonation products like CO, CO2 and N2). The result
is that these detonation product (BF3 and B2O3) will retain much of the energy of detonation as internal, thermal
energy rather than doing mechanical work on the surrounding. The net effect is that you will get higher detonation temperature but the energy
contained in detonation product will be available at late time and at high expansion of the detonation product cloud (when the adiabatic exponent
cofficient Cp/Cv approach the value of 1.4 down the isentrope). for more information on boron containing explosive see
Numerical Modeling of Explosives and Propellants, Second Edition for Charles L. Mader.
Also, energetic materials containing fluorine explosophoric group (e.g., -NF2, -SF5...) shows that they increase little the
crystal density when compared to nitro bearing group and that detonation performance is of the order of powerful classical explosive, nothing special.
Dany.
[Edited on 21-8-2013 by Dany]
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AndersHoveland
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| Quote: Originally posted by Dany | | the detonation of boron containing explosive generate complex high molecular weight detonation products like BF3 and
B2O3, these detonation product (BF3 and B2O3) will retain much of the energy of detonation as
internal, thermal energy rather than doing mechanical work on the surrounding. The net effect is that you will get higher detonation temperature but
the energy contained in detonation product will be available at late time |
That is certainly a factor, but consider this: a tripropellant rocket, burning lithium with fluorine, and using the resulting heat to vaporize excess
liquid hydrogen, has a higher specific impulse (is more energetic) than just burning liquid hydrogen with oxygen. In the situation here, the hot
boron-containing decomposition products will transfer much of their heat to the nitrogen gas, causing it to expand.
You forgot to mention that H2O, a fairly ubiquitous decomposition product, also absorbs a fairly large amount of energy.
One potential decomposition product is boron oxyfluoride, and its formation may be the most optimal of the possible boron decomposition products, from
the standpoint of what gaseous products will occupy the greatest volume. (not sure how much energy the gaseous trimer absorbs before decomposing into
the monomer)
| Quote: Originally posted by Dany | | energetic materials containing fluorine explosophoric group (e.g., -NF2, -SF5...) shows that they increase little the crystal
density when compared to nitro bearing group and that detonation performance is of the order of powerful classical explosive, nothing special.
|
The fluorine-containing oxidizing groups release much more energy when they are combining with a fuel other than carbon atoms. What this means in
practice is that -NF2 groups would add the most energy to organic molecules that already have a high oxygen balance.
The S-F bond is fairly strong, and such a group is only worth having if there is other atoms very preferential for the fluorine to bond to (not
carbon).
Generally -NF2 groups are not really practical from a performance perspective because the oxygen in an -NO2 group can form two bonds, whereas a
fluorine atom can form only one. Usually there is no shortage of fuel in the molecule and the oxidizing groups are the limiting factor. The formation
of a molecule of H2O releases more energy than an HF, and hydrogen atoms are very easy to incorporate into an energetic molecule. -NF2 groups also
result in the explosive being more sensitive, though in some cases they can have advantages over nitro groups. For example, two nitro groups on the
same carbon tend to be thermally unstable, but if it is a nitro group and a difluoramino group it is very much more thermally stable.
Another possible area to explore may be the use of lithium clusters, of the type found in n-butyl lithium, a fairly common reducing reagent.
[Edited on 22-8-2013 by AndersHoveland]
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caterpillar
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Well, there is at least one crazy idea. What if one will be able to construct a cumulative charge from one molecule? As you, boys, definitely know,
jet stream from a cumulative charge may have speed up to 15 km per second. Let's try to imagine chain of microscopic cumulative charges. The first
ignites the second and so on. I mean, if it is possible to restrict propagation of a shock wave in some directions at molecular level? If so, the
threshold (11 km/s) could be exceeded.
Women are more perilous sometimes, than any hi explosive.
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Dany
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| Quote: Originally posted by caterpillar | | Well, there is at least one crazy idea. What if one will be able to construct a cumulative charge from one molecule? As you, boys, definitely know,
jet stream from a cumulative charge may have speed up to 15 km per second. Let's try to imagine chain of microscopic cumulative charges. The first
ignites the second and so on. I mean, if it is possible to restrict propagation of a shock wave in some directions at molecular level? If so, the
threshold (11 km/s) could be exceeded. |
You can increase the detonation performance of a particular explosive and this by colliding detonation wave and forming mach wave in the explosive
charge, but in this case you have an overdriven detonation. Overdriven detonation are unstable state and will decay back to the normal champan-jouguet
state. Anyway, we are talking about organic explosive compositions that can sustain stable detonation wave and exceed 11 km/s.
Dany.
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caterpillar
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But if we may construct such molecular construction, where detonation wave is focusing itself? Such anisotropic medium, where shock wave is not a
sphere? What about sandwich-shaped structures? Nano-tubes? What I'm trying to tell is that analysis, based on only brutto- formula of a compound is
not very accurate. There is surely some reserves, lying deep in molecular structures. Large molecules may have some unexpected properties. for
example, can you predict, if some protein is extremely toxic or absolutely harmless, knowing its formula (or even structure)?
Women are more perilous sometimes, than any hi explosive.
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Dany
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Hello caterpillar,
The only way to increase the detonation performance beyond the normal Champan-Jouguet point of a given explosive is to take the explosive to an
overdriven state. This can be accomplished in several way, for example detonating an HMX cylinder in close contact with an TNT cylinder, will cause
the TNT to detonate in an overdriven fashion but only for a short run distance, which can be detected using ionizing pin method for measuring
detonation velocity. Shock wave shaping is another mean of achieving overdriven detonation like colliding oblique detonation wave or convergent
detonation wave. The impact of a high projectile (e.g., metal plate fired from a gas gun) cause an explosive to be in overdriven state. In some case,
like the homogenous initiation of liquid explosive (e.g., nitromethane) the shock wave enter the explosive and heat the material at the interface.
after a certain time, a detonation wave appear at the boundary and travel in the explosive in overdriven fashion, because the detonation wave is
traveling in a medium that has been shocked and warmed by the passage of the first inert shock wave. Our experience with explosives and detonation of
energetic shows that a great deal of properties can be predicted based on a few information (e.g, physical state, basic thermodynamics, and an assumed
equation of state).
Some high explosive display what we call shock anisotropy. PETN has this property. But shock anisotropy affect the sensitivity of the explosive
materials and not the detonation performance.
check this paper for more info on shock anisotropy in PETN
Dany.
Attachment: Shock Wave Initiation of Pentaerythritol Tetranitrate Single Crystals Mechanism of Anisotropic Sensitivity.pdf (189kB)
This file has been downloaded 1388 times
[Edited on 22-8-2013 by Dany]
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AndersHoveland
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What about using exploding wire filaments throughout the explosive to detonate the mass simultaneously? Or shape propagating hollow channels into the
explosive to transmit a high velocity explosive jet? If the detonation is being initiated by a source other than itself, the detonation velocity could
potentially be exceeded.
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Dany
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Reply to AndersHoveland
You will always get an overdriven detonation that will decay to stable chapman-jouguet state.
Dany.
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caterpillar
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Hello, Dany, you think in terms of continuous media. Let's open your mind. Assume you have a super-molecular constructor, which is able to construct
any molecule (if this one is stable, of course) and any combination of them. What me and Anders trying to say is that some things is possible, if not
now, but may be some decades later with tomorrow technology. A micro cumulative charge may generate a jet with velocity higher than 11 km/sec. This
jet may initiate the next micro charge and so on. We may get 15 km/sec at macro level. What prevents us to reproduce it at micro level? Only our too
thick fingers. If a molecule blows up, their splinters fly at random directions. What is something like a laser effect is possible? A photon hits an
activated media and generate two photons, moving at the same direction. What if something like it is possible in case of molecules? A splinter (one
atom or some simple molecule like H2O, CO) hits the next molecule of HE and it generates splinters, moving at the same direction? And what has came to
my mind just now. There is a way to obtain extremely hi speed of detonation. I read about it some years ago. What about 1000 miles per second? Or
more? Detonation may be caused by light, generated during explosion of a molecule. Mixture of Cl2 and H2 blows up, been illuminated with UF beam. And
during reaction this mixture generates such beams, which propagate with light velocity and transmit detonation. Detonation, initiated by light is
possible in solid or liquid medias too. Well, I suspect that such media would be too sensitive, if one single photon may cause detonation of a
molecule with hi probability. But we are speaking about possible ways (eq. pure theory) how to get extremely speed of detonation, but not about its
practical realization.
Women are more perilous sometimes, than any hi explosive.
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Marvin
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Light, electric current, nuclear criticality - there are plenty of ways of doing it but I think you are moving outside of what can reasonably be
called a detonation wave. A constructed 'lattice' could have copper strips to detonate micro caps throughout the charge, propagation could be a
significant percentage of the speed of light but it's not a VoD.
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Microtek
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I agree that these highly speculative methods of achieving VODs above 11 km/s are not really within the boundaries of the article that stated this
limit. However, I also think that this limit is quite artificial, and akin to past assertions that eg. the speed of sound could not be exceeded, or
that rockets wouldn't work in a vacuum.
It is good statistical practice to not use a fitted model to try to predict beyond the boundaries of said model, and that is exactly what the authors
are doing here: They are making a model based on a selection of already synthesized energetic materials, and then try to predict the future from that.
But this only works as long as the initial assumptions and paradigms hold, and we have seem, time and again, that science progresses in leaps and
bounds, precisely when a revolutionary discovery is made.
So, in essence I would call this article an entertaining theoretical excercise, but nothing more.
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Dany
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After reading what other member wrote , i would like to give some remarks:
first, the title of the topic is clear regarding the material studied which is organic explosive. Nobody said that, in general 11 km/s cannot be
exceeded. As i mentioned above 11 km/s can be achieved and exceeded using homoleptic polynitrogen explosives. Pentazolium cation N5+ is an example (at
least theoretical calculation predict a VoD of 12 km/s, no measurement has been made). Anyway, although Dr. Pepekin studied a small sample of
explosive to derive his correlation, i can say that many of the compound can be treated as an extrem case of his group. For example,
dinitrodiazenofuroxan is the denset and the most energetic of all furazan and furoxan derivatives. As we know, no furoxan derivative reported in the
literature can surpass ~9.5 km/s. We also know that all known explosophoric moiety has been used in almost every combination we can imagine and the
result shows that VoD is around ~10 km/s. These finding support the conclusion in Pepekin papers that 11 km/s is the limiting value of organic
explosives. I believe, that there is some space for increasing VoD beyond 10 km/s if new, exotic organic explosophoric group are discovered (which is
not very plausible). Also, As i mentioned in the thread, octanitrocubane is very energetic (VoD~9.8 km/s, Pcj~45 GPa) but with moderate sensitivity,
so synthesizing new platonic hydrocarbon with very high heat of formation (>>650-700 kJ/mol) and high crystal density (>2.2g/cm3) may be
helpful for exceedind 10 km/s. As it is clear from the literature, explosive scientist are working on high content nitrogen compounds because they are
almost convinced that increasing the detonation performance with carbonaceous compound is almost exhausted.
Dany.
[Edited on 23-8-2013 by Dany]
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