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Using Galculations to Determine Internal ResidualOverpressures in Explosive Breaching ApplicationsBy Ed Stark and Charles O'Connor

Inaword: DON'T!Why not?Because they simply don't work to de-

termine anything useful in the explosivebreaching world.

Should you still use them? Yes.whv?One: Because they validate to YOU

that they don't work to determine any-thing useful in the explosive breachingworld.

And Two: Because you cant take ourword for it, and have to prove it to your-self firsthand-this is the only way foryou to be that subject matter expert weall MUST be.

W'hen it comes to contemporary tac-tical explosive breaching training andpractices today, the community is be-sieged with data and information for thepurpose of making the "operator" moreknowledgeable in the discipline of usingexplosives in a surgical manner, whilereducing the chances of bodily injuriesand/or collateral damage.

This is done with the introductionof scientific equations and formulas tohopefully give the breacher a somewhataccurate prediction of where it's safe forthem to stack, or what can be expectedon the inside of the target objective. Andit makes us look really, really smart tool

Here lies the problem-many of thecalculations being used in this commu-nity (and the "industry" in general) arebeing applied incorrectly, and trainers/users have absolutely no knowledge ofwhere these "magicaI" formulas originat-ed, or for what purpose they were creat-ed. Yet the data continues to be regurgi-tated from one source to another, over aperiod of years, to the point that it's nowconsidered to be the standard-when ittruly provides nothing pertinent for us.

'Worse yet, it's responsible for gettingpeople hurt and causing a tremendousamount of unpredicted damage, leading

55 - November/December 2O1O

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to unnecessary litigation, the end ofpro-grams, and the complete loss of credibil-ity for breaching teams.

And now there are some "new" mathequations being introduced to our com-munity by people who don't even have afundamental knowledge of what tacticalexplosive breaching really entails in anurban environment.

One issue is people blindly followingwhat they were taught, without havingthe first hand experience or the referenceinformation to support such action. Theol'"that's what they told me in schoolj' or"he said so, and he's really smart" doesn'tquite cut it on its own merit, and won'tprotect you as the subject matter expertyou are expected to be.

On that note, let's discuss the"Weibull" formula that breachers ev,erywhere are told will predict residualinternal overpressure within a specificinternal volume (i.e. room), by pluggingin your net explosive weight (in poundsof TNT). This will purportedly tell you ifyou can stage a team within a room andpredict the damage inside.

P =2410(WlV1'zz

For argumenti sake, let's completelyignore the fact that everybody has theirown opinion on the correct RE chart todetermine the TNT equivalent for yourexplosives. This is more about your un-derstanding why you use what you do,rather than actual resulting values. Let'salso forget that some people dont evenuse this equation properly. How manybreachers have been using this to deter-mine safe stacking locations for their per-sonnel? Too many. Why? Because they'vebeen taught that it will do exactly that.

"Even a broken clock is accurate twotimes every 24 hoursl'

Ifyou can't articulate what a "Weibull"is, where it came from, or why it's beingapplied (but still use it for one reason oranother), then youve already failed as

that subject matter expert in the field.Truth is, most people out there teachingthe formula can't tell you either, but un-fortunately for you, they aren't the oneswho will be held responsible for YOURimproper use of it. And improper useby some, will then often lead to judicialoverview, affecting the rest ofus.

Hans R.!f. Weibull of the RoyalSwedish Fortifications Administrationpublished a paper using this equationentitled "Pressures Recorded in PartiallyClosed Chambers at Explosion of TNTCharges (U)'l Annals of the New YorkAcademy of Sciences, Vol. 152, Art. 1, pg.357, 1968, which resulted from a seriesof tests conducted in 1966 to determinesome basis for designing an explosionchamber of a nuclear blast simulator.Hmmm... so far this isn't translatingvery well to my explosive breaching stripcharge.

Playing devil's advocate for a minute,let's just say it actually has some relation-ship with breaching charges and the ef-fects one can anticipate within a 3 dimen-sional environment (which it doesn't).More recent studies have concluded thatthis formula ignored important "physicalphenomena" that makes it "impossible toextend to any other explosives other thanTNTI' Okay, do we need to buy someTNT now to make this work?

Tests of this nature are usually per-formed with either spherical or cylindri-cal explosives suspended from the air andcenter detonated (which also produces acompletely different effect than what weuse in breaching). And contrary to popu-lar belief, most of us aren't doing nucleardetonations.

So tet's juit use logic to figure this allout:

If, by properly doing the math in theformula, we get an answer of, for exam-ple, 2 PSI within a room, where exactlyis that "2 PSl" suppose to be? Talking tohundreds (if not thousands) of breachers

trained to use this calculation, they are very "safe" figure. Again, we know andclearly under the impression that any- see this from examining thousands ofwhere within that volume there would shots on real structures; none of whichexist a "2 PSl" value. So with that under- can be properly duplicated on ranges orstanding, does that mean you can stand facades in open terrain.one inch from the chargeland still sustainonly 2 PSI?... one foot from it?... Ten

nerearesomeexarnptes:

feet? W'hat about reflective surfaces, in- Example #l: A "slider" breachingtersection points and corners? 2 PSI as charge was placed on a metal outwardwell? And if you ARE using this to pre- opening door inside a large structure.dict potential injuries and/or damages, The area of the breach point "room" waswhich charts and exposure durations are absolutely humongous, and the resulting Sensors setup for Example 3 shotyour references to make those determi- PSI prediction based on the charge andnations: I millisecond exposure? 10 mil- volume using Weibull was an estimated Example #3: An internal thru-wallliseconds? And what is a safe PSI value value of .36 (psi). It should be noted that charge inside an industrial building of-to stack inside a room anyway? Another the calculated volume was reduced and fice; 32 feet span from the charge to theone of those elusive questions with vari- 'tubed" significantly to create a "smaller" back wall. Using the formula, the calcu-ous answers out there; all vague. than actual area and produce a higher lated psi was determined to be .92 inside

Others believe that the magical 2 PSI "worse case" figure using the calculation the breach point room. Pressure gaugescan be found in the center of the room... and did not take into consideration large were again placed at various locations,Another myth which has been disproved openings leading to the building exteri- with one (Gauge #2) placed 12 feet di-time and time again. or, halls, stairways and numerous other rectly behind the charge. Monitoring

Complicated? You bet. But if you're rooms and areas which would allow blast equipment captured the incident over-planning to use something like this cal- pressure to vent. Pressure monitors at pressureonGauge #2initiaIIyat2.S3psi;culation, you better understand how and various locations throughout captured but it was struck again due to reflectivewhyitwasdeveloped,because YOUARE readings from the breach point as fol- surfaces, and re-spiked to 3.5 psi. ThatTHEEXPERTandresponsibleforthat lows:3.1 psi (19 feet),3.68 psi (23 feet), gauge received the highestvalues of therelea.se of energy, 4.53 psi (19 feet) and a whopping 5.96 psi six pressure gauges used in this test,

From performing thousands of deto- at only 18 feet awayl So where exactly was making the area near the center of thenations inside real structures, we know this .36 psi suppose to be anyway? room more than three times the calcu-that the Weibull calculation provides you r !^ ) ̂ ̂ .- ^L .-_ lated psi... and on secondary reflection.with nothing useful in explosive breach-

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ing, except to validate ii"i ,i t."J, with a higher NEW in the same environ- So again' how did this calculation' in

work. rhis comes r.o- y"u.,'or.."!..,- :'?i, ::j":,j::T'lig-:]":,1"^1^:11:: ""tx;l'f i^::tJ:$[T.';.", any for-

ltilffii;'}::t [T:",:*;:'tff ii ff;?i;:1*fi,'"";ffiUj{i;i#* }"iu:ti:"::.!:i:: '}".1x[*'tl";actually is, providing us with a "worst , .. .o, -o _, " , points) ever provide us with the infor-case scenario" calculation. Understand-

varlous locatlons wltnln tnat area) we oD-

ing also, that this i, ;; ";"i;"-"",

tainedreadings from3.44at27fe'etaway, llation we need to determine property

where we actuaily have the ability r'10'2PSlat20feet' o"-lt;:;:li1$;.?:xtt#J,lffiiilil;

to do measurements, but not under x in those environments is the onlyffi cueiea' rrior" rsnd&

operational situations where we'd be cAuc's,Bn.,romch,4" & --"'--1 ,*_--*-i,el way to make those predictions ac-m PLACEMENT: Hing6

very unlikely to do so. - if!+:r -. - ffi ;;;, -

ffi curately.Over the years, and with the as- ' $fu* I cakah,drntemat Under most circumstances, a

sistance of folks out there with really \ I r:':::::'sistance of fblks out there with really \ L Ncsidilatur: team should be inside an adjoining

big brains (unlike our small ones),

various national labs using sophis- ,,';*;',;" \ & I *- since you CANNOT calculate orticated blast pressure monitoring 3J-!!! *-===\.'*$

| lf##ffi1 predici reflective pressure or.inter-

equipment and cameras, have con- _-zq mg f-*;;t section points-which can truly ruinfirmed this much-depending on ,/---'' i I ffi | errrem I your entire day and keep you fromexactly WHERE within that volume ffi9'- / H S ffil focusing on the threat you're facingyou monitor, you could experience "^"""::;;;:-'""" / # eW The belief that you just need to "suckdangerously high values when the :- "'- / ffi @ l:6iiii#"'J it up" and get "punished" by gaining*'"":::'..:i'*""" &Weibull calculation falsely provides ,. .,,1.:t!,s .,RY & a few feet distance advantage is mis-you with what you may consider a Sefup for Example 2. guided. If the stack can't focus on the

Vol. 37. No. 6. The Detonator - 56

staging location forpersonnel (whetherinside or out)-orthe insane belief thatby using a ballisticshield, the team canreduce by half thecalculated "minimumsafe distances" fromthe breach point...maybe on a range, inthe middle of the des-ert, or someplace elsethat is without anyreflective surfaces.

But in real life, inthe real world, de-

Debris pattern to interior of a wall .r ,breach,

penolng on tnese anq some or tne otner"new" calculations being offered out

mission at hand because of injuries, or there (versus your training and experi-

having their bell rung, the entry is now ence) will get you in a world of trouble-

jeopaidized. eventuallY'

And since these calculations are be- But that's another story'

ing used by the majority of the breachingcommunity, it's imperative that the con-temporary breacher, as a subject matterexpert, be familiar with the calculation,the history of its use and purposes. Butmore than that, they must know the dan-gers of following along because "some-body said soj' without validating the re-sults themselves.

Unfortunately the community, byembracing this calculation, has now re-quired you to disprove this theory withyour own life experiences (and not withour "heresay"). Of all the words in thevocabulary of serious breachers, two ofthe favorites should be show me, andthey should be used everytime there areclaims that using this or that will makeyour job safer (whether it be calculations,equipment or even tactics).

Relying solely on a calculation todetermine the personal safety of teammembers, potential hostages, bystand-ers and suspects in explosive breachingapplications, without taking into consid-eration everything in your environment,is like driving down the street with youreyes closed-you may get away with it...this time.

This falls directly in line with thecommonly misused practice of relying ona calculation to determine a "4 PSI" safe

About the Authors

Ed Stark is a 3}-year veteran of law enforce-ment, and is a recognized expert in explo-sives and other disciplines. Stark workshand-in-hand with various state, federal andforeign entities, providing, explosives train-ing and consultation. He can be contactedat: eds@northvector.com

Charles O'Connor spent his career in theNavy Special Forces, accruing decades ofextremely rare first- and third-world tacticalexperience. After his military career, he con-tinued to provide a variety of services to theU.S. and foreign governments. He can beco ntacte d at: ch u c k@ n orthvecto r. co m

O'Connor and Stark (members of Region 7)presently work with national laboratoriesand lead the only team currently providin!,an 8j-hour DHS-certified tactical exp/osivebreaching course in the country. Their groupis also recognized and approved by lnterna-tional Traffic in Arms Reglulations (TAR) andSpecla/ Operations Command to providethis training to various Allied countries.

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Vol. 37. No. 6. The Detonator - 58