NAVSWC TR 91-102 AD-A238 844 A REEXAMINATION OF THE AIRBLAST AND DEBRIS PRODUCED BY EXPLOSIONS INSIDE EARTH-COVERED IGLOOS BY MAICHAEL M. SWISDAK, JR. RESEARCH AND TECHNOLOGY DEPARTMENT 28 JANUARY 1991 Approved for public release; distribution is unlimited. NAVAL SURFACE WARFARE CENTER S Dahlgren, Virginia 22448-5000 * Silver Spring, Maryland 20903-5000 DEFENSE TECHNICAL INFORMATION CENTER 9196501 .. ,z ..
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NAVSWC TR 91-102
AD-A238 844
A REEXAMINATION OF THE AIRBLAST ANDDEBRIS PRODUCED BY EXPLOSIONS INSIDEEARTH-COVERED IGLOOS
BY MAICHAEL M. SWISDAK, JR.
RESEARCH AND TECHNOLOGY DEPARTMENT
28 JANUARY 1991
Approved for public release; distribution is unlimited.
5-4 COMPARISON OF STANDARD WITH UPPER BOUND OFPREDICTIONS .......................................... 5-13
vi
NAVSWC TR 91-102
CHAPTER 1
INTRODUCTION
At the request of the Department of Defense Explosies Safety Board (DDESB),the Naval Surface Warfare Center (NAVSWC) has conducted a review of theavailable airblast and fragmentation/debris information that was been produced byexplosions within standard earth-covered, explosive storage magazines. The effortbegan during the 1990 fiscal year with the collection and collation of the data.During the current fiscal year (1991), the data have been compared with existingDepartment of Defense (DOD) explosives safety standards. The goals of this effortare to recommend possible changes to the standard (if needed) and to provide the bestavailable prediction tools for both fragmentation/debris and airblast.
According to DOD-6055.9-STD, 1 standard earth-covered magazines areapproved for all quantities of explosives up to 500,000 pounds (227,273 kg) netexplosive weight. The standard defines five basic types of standard magazines:(1) reinforced concrete, arch-type magazines, (2) Navy-type magazines, (3) box-type Amagazines, (4) earth-covered, corrugated steel, arch-type, and (5) earth-covered,circular composite arch. During the past 40 + years of testing, most or all of thesetypes have been tested at one time or another. For the remainder of this report, theauthor will use the generic term "earth-covered igloo" when referring to all of thesetypes. The United States Air Force has conducted many tests in what they havetermed Modular or Hayman Igloos. These are also earth-covered but of a muchsimpler design. The data from these tests will be referred to as from "igloostructures" or from a modular igloo. The "igloo structures" have not been establishedas a standard type of magazine, therefore, they are only approved for storage up to250,000 pounds.
The earliest documented testing of earth-covered igloos occurred shortly afterWorld War 11.2.3 These tests were conducted at the Naval Proving Ground, Arco,Idaho. During the 1960s, tests were conducted at the Naval Ordnance Test Station(NOTS) (now, Naval Weapons Center, China Lake, CA).4 These tests examinedearth-covered, steel arch type magazine construction. Beginning in 1971, theDDESB began a series of tests call ESKIMO (ESKIMO is an acronym for ExplosiveSafety Knowledge IMprovement Operation).5 These tests have continuecFthrough1986 and constitute the source for the bulk of our knowledge regarding the blast andfragmentation/debris produced by explosions within these types of structures.'"' TheAir Force igloo structure and modular igloo data have only recently beenreported.12
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NAVSWC TR 91-102
CHAPTER 2
EVENTS CONSIDERED
Table 2-1 presents a summary of the events considered for this analysis. Manyof them were not suitable for inclusion in the analyses that follow. The reasons forthis range from the type of event (models, external shots, etc.) to the type of datacollected (or not collected).
The ARCO tests3 did not collect or consider fragmentatiordebris data. Theairblast data were collected with paper and foil gauges. As a result, these events areof little primary use to this study. A collateral test series to the ARCO tests used aseries of scale models. 2 Again, the airblast was extremely crude and no debris datawere collected. Because of the small scales involved and the fact that the donorcharge was not scaled, these results are deemed inapplicable to the current study.
The NOTS Test Series4 used a series of scale models to study the behavior ofearth-covered, steel-arch magazines. Again, the scale was small and the donorcharges were not scaled. As can be seen in the data comparison section, these eventsobviously constitute a different data set than the remainder of the igloo tests. One ofthe NOTS tests, NOTS 6, was a full-scale test and these results seem to belong to thesame data set as the remainder of the full-scale igloo tests.
There have been seven ESKIMO tests since the start of that test series in1971.-11 Of the seven, however, only three are applicable to this effort-ESKIMO I,ESKIMO I, and ESKIMO VI. The remainder did not have a donor chargedetonating inside a magazine; rather, they were designed to study other aspects ofigloo construction and safety.
In 1984, the U.S. Army conducted a series of tests to examine the minimumcharge weight that could be contained within standard igloos. 1 7 Because of thenature of the tests, the charge weights and the loading densities were very low. Thecharge weights ranged from 12 to 150 pounds of TNT. In addition, there was a blastshield directly opposite the front door. Only limited low pressure (less than 2 psi)airblast data were recorded. Debris densities as a function of range and azimuth outthe front were also recorded. Because of the nature of these events, the airblast datawill not be considered in the general data base, but will be compared with thepredictive methods derived in this study.
As part of the Air Force Buffered Storage Program, several tesL were conductedinside both simulated and actual earth-covered igloos. The following criteria wereapplied to these tests in selecting which data to include in this study: (1) the NetExplosive Weight (NEW) had to be known; i.e., either the accepLor stack did notdetonate (NEW = donor stack) or the acceptor detonated totally (NEW = donor plusacceptor) and (2) the structure had to have earth cover.
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NAVSWC TR 91-102
TABLE 2-I. EVENTS CONSIDERD FOR THIS STUDY
EVENT NAME DATE DONOR MAGAZINE TYPE CHARGE SIZE/TYPE COMMENTS REFERENE
ARCO i 11/1WO EarfI,-mvered. 930 MK 36 1000-poind bombs~ (1) crude urtol. ASESB To 5
ESKIMOI 11 /622r73 Open revstrent 72 M117 bomrbs (1) Not psicibs NWC TP $567(24,000_pounldsTNT eculvalent) __________ _________
ESKIMO III 6/12f74 Eaflh-covered, 916 M117 bombs (1) srbitaldue NWC TP 5771____________ steel arch (374,406 pounds TNT oufirslsntl 12) no debr ils _________
ESK(IMO IV Sep-75 Oen, hosttpher"oa 4.62S blocks of TNT (1) Not applicable NWC TP 5873wtlei (37,000 pounds TNT)
ESKIMO V Aug-77 Oen, hemispfsrtci 9,376j blocks of TNT (1) Not apkicls NWC TP 5873____________stack (n______00_ pounds_______
ESKIMO VI 7/2&W8 mass propaflaugeomeLry 60 MK It torpeo watsaftad (1) 1/2-scale model ?ICEI TR-889of earth-coversd Tp lID (51.300 pounds TNT equioslert (2) alrtlat data
Only three events collected debris information that might be considered useful-ESKIMO I, ESKIMO VI, and HASTINGS IGLOO. Of these three, the ESKIMO Ievent collected detailed fragmentation/debris data over a full 3600 azimuth. All thedebris information collected is presented in Appendix A. ESKIMO VI presented onlydescriptive information, so no quantitative detei-,ninations can be drawn from it.
DEFINITIONS AND CRITERI.
The DDESB defines a hazardous fragment density as "A density of hazardousfragments exceeding one per 600 sq ft. (55.7 m2 )."' 1 A hazardous fragment is definedas "one having an impact energy of 58 ft-lb (79 Joules) or greater." Recentinterpretations by the Secretariat of the DDESB h've taken the 600 ft' to bemeasured trajectory-normal as opposed to ground surface pickup. Procedures for thestandardization of the analyses of debris have also been p-oduced.18 Thesestandardized procedures have been used to reexamine the aebris data collected onboth FSKIMO I and the HASTINGS IGLOO tests.
ESKIMO I
Both magnetic and hand pickup were used on this test. Three 5' sectors (off thefront, side, and rear of the structure) were burveyed in and clea ed if vegetation anddebris before the test. These sectors were collected by magnetic pickup. In addition,foot search and hand pickup were conducted in selected 100 ft x 100 ft areas. Theseadditional areas were selected to supplement the data derived from the magneticpickup as well as to extend the collection areas into locations not accessible to thetruck-mounted magnet. For this test, calculations indicated that for a free-fallingfragment or piece of debris to be hazardous, it would have to have a weight of at least0.28 pound.
The data were presented in graphs in terms of debris densities as a function ofrange for various debris weights (_>0.125 pound, _ 0.28 pound, _> 1.0 pound). For thisanalysis, the density-range data were read off the graphs for the ->0.2S poundinformation. These data were then converted to pseudo-trajectory normal de: sitiesand analyzed according to the procedures of Reference 18. Figures 3-1 through 3-5present the results. Reiiiember that the hazardous fragment range is the range atwhich a lez.,. squares exponential fit through the pseudo-trajectory normal datareaches a value of 1. Also shown on each graph is the 90 percent confidence intervalfot the hazardous debris range.
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NAVSWC TR 91-102
Thus, out the front of the igloo on this test the hazardous fragment range N.as3857 feet; off the side it was 2743 feet; o ,the rear it was 2376 feet. These correspondto scaled ranges of 66.0, 46.9, and 40.6 ft/lb 3, i espectively.
HASTINGS IGLOO
Significant debris data were collected on. 3ur of the HASTINGS IGLOO testy,the 69-, 80-, 100-, and 150-pound tests. Fragment density distributions at distancesless than 175 feet (53 meters) were not used due to the masking effect of a blast shieldin front of the structure.
It is probably appropriate to describe the test structures before the results arepresented. Th -_ site was part of an abandoned Navy Ammunition Depot that wasconstructed during World War II. All of the igloos exhibited structural failures in theform of hairline cracks in the sidewalls, arch crest, backwall, and headwall. Erosionof the earth cover was observed ir many cases due to a lack of maintenance. Themagazine headwalls faced an earth-backed concrete blast shield. I ne distancebetween the vet-t.ical he'idwalls and the blast shields varied between 12 feet at thebase and 15 feet at the top.
The debris results are summarized in Figures 3-6 to 3-9. On each test, debriswas collected .n three separa+e zones: 0' to 50, 5' to 100, and 100 to 45' . The hazardoufragment range (i.e., the range at which the hazardous fragment density becomes 1)extended to significant scaled distances out the front. The unscaled ranges are shownon each graph. In addition, the 90 percent confidence interval is shown for each of theranges. These ranges correspond to scaled distances of 112.9, 143.7, 103.0, and150.2 ftllb"r3 . These scaled ranges are much greater that those measured onESKIMO I. They may be affected b, the poor condition of the structures existing atthe time of the test. Moreover, the loading densities (charge weight/internal volumeof structure) used on these tests were quite low; thus, the roof and sides of thestructure did not fail-channeling the debris out the front. The range of hazardousfragme.its is less than 670 feet for less than 100 pounds and the maximum range isless than 700 feet for 150 pounds.
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NAVSWC TR 91-102
1000 -D=415 48 *exp (-0.0015632*R)
< Correlation Coefficient 0.9805
~Lju
-) <Q0 COFDEC INEVL3800-3f
00
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(n FRAGMENT HAZARD RANGE 3a27 feeta. < ~ 90/ CONFIDENCE INTERVAL. 23 t-2895 ft0
0.1
500 1000 1500 2000 2500 3000 3500 40
RANGE, R (feet)
FIGURE 3-2 ESKIMO I: HAZARDOUS FRAGMENT D)ENSITY VERSUS RANGE (SIONE)
1 0 0.. .. ... .. . . . ... .. . .. 3...3
NAVSWC TR 91-102
100 1
AD = 315.90 *exp (-0.0025126-R)Correlation Coefficient: 0.9387
wOL
............. FR A G M EN H A ZA RD R A N GE.. 230... feet............... ..................................
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0
o a: FRAGMENT HAZARD RANGE -283 feetW 90% CONFIDENCE INTERVAL: 2750 11-240 ftI
20 000 2500 000 50 300
RANGE, R (feet)
FIGURE 3-. ESKIMO 1: HAZARDOUS FRAGMENT DENSITY VERSUS RANGE ER
(FON/SD DIAGONAL
3-4
NAVSWC TR 91-102
D D1170500 exp (-0.0069142*R)A Correlation Coefficient: 0.9522
1 . £ 05 - y 17495.78 eA(0.0108683x) R 0.953829 ........................o sio- y=361.............0..............5......
0.1 *
0 100 200 300 400 50060 70 80
FIGURE 3-9. HIASTINGS IGLOO-I150-POUND TEST HIAZARDOUSFRAGMENT DENSITY VERSUS RANGE
NAVSWC TR 91-102
CHAPTER 4
AIRBLAST
Airblast information has been collected on almost all of these events.Unfortunately, the coverage has been somewhat spotty. Moreover, the quality of thefar-field data (below 10 psi) has ranged from barely adequate to totally lacking. All ofthe airblast data that has been obtained is presented in tabular form in Appendix B.Only the following events will be analyzed in detail: NOTS 6, ESKIMO I,ESKIMO ITm, and ESKIMO VI.
DEFINITIONS AND CRITERIA
DOD 6055.9-STD' and NATO guidelines define several acceptable exposureswhich might be applied to aboveground magazines. These are:
1. Permissible exposure to airblast overpressure-barricading required: 9W""3
6. Inhabited Building Distance-Rear of earth covered magazine-W< 100,000 pounds: 25W" ( 2.2 psi)
7. Public Traffic Route Distance-W>250,000 pounds: 30W" 3 (1.7 psi)
8. Inhabited Building Distance-Front and Side of earth covered magazine-
W<100,000 pounds: 35W"3 ( 1.4 psi)
9. NATO Public Traffic Route: 37.5W"3 (1.3 psi)
10. Inhabited Building Distance-W<100,000 pounds: 40W 13 (1.2 psi)
11. Inhabited Building Distance-W>250,000 pounds: 50W"3 (0.9 psi)
12. NATO Inhabited Building Distance: 58.7W"1 3 (0.725 psi or 50 mbar)
13. NATO Twice Inhabited Building Distance: 115W"/3 (0.29 psi or 20 mbar)
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NAVSWC TR 91-102
The scaled distances which these criteria refer to are directly related to peakoverpressure. The relationship is based on the Kingery compilation of surface burst,hemispherical TNT data, 19,20 referred to hereafter as the Kingery TNT standard.Table 4-1 presents an excerpt of the data contained in this standard. This will formthe basis for all the airblast comparisons that will be performed later.
Figures 4-1 through 4-8 present the airblast results measured on the followingevents: NOTS 6, ESKIMO I, ESKIMO III, and ESKIMO VI. The data presented inAppendix B have been scaled to sea level conditions for each event. In addition, thecurve marked standard on each graph is the Kingery hemispherical standard curvefor the TNT weight of the event. Least square curves have been fitted to each of thesedata sets, so that the ranges to various pressure levels can be computed. This curvefit information is presented in Table 4-2.
The Air Force simulated igloo (buffered storage) and modular igloo data arebeing considered separately since they do not represent an, as yet, approvedmagazine design. This data is also presented in Appendix B. There seems to be aproblem with the impulse information. For this reason, none of these data will beanalyzed or discussed further.
Instead of discussing each test within the buffered storage and modular igloodata sets, the Appendix B information has been scaled to sea level conditions and to acharge weight of 1 pound. These results are presented in Figures 4-9 and 4-10 for thefront and side directions. Also shown on each graph is the Kingery hemisphericalstandard. Least square curves have also been fitted to this data set so that the rangesto various pressure levels can be computed. This information is presented inTable 4-2.
Using the information presented in Table 4-2, ranges and pressures can becalculated for each of the potential criteria presented above. This will then allowdirect comparison for each of the standards. These results are presented in Table 4-3.Only the data for ESKIMO VI show any violation of the criteria. In this case, thenumbers are so close to the standard that there is no statistical difference betweenthe least square curve fit value and the standard itself. Thus, based on thisinformation, the standard appears to be safety conservative.
4-2
NAVSWC TR 91-102
............. ................... ...... ----........ . ................ ...... ................. FRONT
NOTE: Fit is of the foim : P-A*RangeABScaled to 1 pound
4-9
NAVSWC TR 91-102
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NAVSWC TR 91-102
CHAPTER 5
DISCUSSION OF AIRBLAST RESULTS
It would be extremely useful if the airblast data presented in the previouschapter could be collapsed into a set of curves representing the three directions (front,side, and rear) for all types of igloos. A basic approach would be to use cube-root orHopkinson-Cranz scaling. A basic assumption here, however, is that the amount ofearth cover and the type of construction are of secondary importance to thephenomena being considered (pressure and debris throw).
The information presented in the last chapter (both the igloo data and thebuffered storage/modular igloo) has been scaled by the cube root of the equivalentTNT charge weight. The results are presented in Figures 5-1 to 5-6 for theigloo/Eskimo data. When the buffered storage/modular igloo data are included, theresults are shown in Figures 5-7 and 5-8. Bad or erroneous data points have beeneliminated. Both sets of data (Eskimo and Buffered Storage/Modular Igloo) appear tobe from the same family. Least squares curves have been fit to each set of data,separately, as well as to the combined data. Shown on the figures are the results of apower law fit of the form:
F = A*XB
where:
F = either peak pressure (P) in psi or scaled positive impulse (I/W1"'3)in psi-ms/lb" 3
A power law fit represents a straight line to the logarithms of the data. In addition tothis fit, a second order polynomial was also fit to the logarithms of the pressure-distance data. The form of this fit is shown below:
F = A*(B+ C * In())
The improvement in the correlation coefficient was, at best, marginal. Table 5-1presents a summary of all of the curve fitting coefficients.
EQUIVALENT WEIGHT
The definition of equivalent weight is the weight of a standard explosiverequired to produce a selected shock wave parameter of equal magnitude to thatproduced by a unit weight of the explosive in question. The standard which is used is
5-1
NAVSWC TR 91-102
the Kingery hemispherical TNT standard. 19 The selected shock wave parameters arepeak pressure and positive impulse.
Using the second order polynomial curve fit to the logarithms of the pressure-distance data and a power law fit to the impulse-distance data (Table 5-1),Figures 5-9 to 5-11 were generated. These are the equivalent weight versus pressurecurves for the three directions. The curves for the pressure and impulse outside adetonating earth-covered magazine are not parallel to the Kingery standard.Because of this, the equivalent weight varies with the range (pressure level). It isstill useful, however, to talk about an average equivalent weight. These arepresented in Table 5-2.
GENERALIZED PREDICTIONS FOR PEAK PRESSURE
The least squares curve fits presented in Table 5-1 can be used to makegeneralized predictions. However, because of the nature of the data and because thedata are coming from such varied sources, the upper bound of the 90 percentconfidence interval for a power law fit will be used. The equations of these upperbound curves are presented in Table 5-3. Figure 5-12 compares the 90 percent upperbound composite of the Eskimo pressure-distance data with the Kingery hemi-spherical standard. Figure 5-13 presents similar comparisons for positive impulse.Figure 5-14 presents comparisons based on a composite of the igloo and bufferedstorage/modular igloo data.
To be safety conservative, the upper bound of the 90 percent confidence intervalshould not exceed the values prescribed in the DOD standards and guidelines. Thiscomparison is presented in Table 5-4. As can be seen, only one of the values exceedthe standard-out the side at the 0.9 psi level for the Eskimo data. Because of thelimited amount of data out the side and rear, definitive conclusions cannot bereached. However, it appears that the standard is not met in the side direction at thelower pressure levels.
The limited amount of airblast data recorded on the HASTINGS IGLOO testsindicate pressures occurring at much shorter ranges than those given by thestandards-scaled distances between 11 and 31 ft/lWI, white the standard wouldindicate distances on the order of 40 or greater for the measured pressure levelsk1.2 psi).
....-.. ........................................ S DL N .Front Side,................... and.Rear.curves .are.the .upper.bound.ofoI he O c fi ecinte..............r.............. ..a......l........
CURVES.. WITH.. HEMIPHE ICA STANDARD........... .,z.....ST N A D ..
SIDE 53.202 -1.0040 0.9732REAR 20.695 -0.7658 0.9334
NOTES:(1) Fit is of the form: F=A*ZA(B+C*In(Z))(2) Z is scaled distance (ft/lbAl/3)(3) The impulse data for buffered storage/modular igloo were not used
EW-P is equivalent weight based on peak pressureEW-I is equivalent weight based on positive impulse
NOTE: Standard is Kingery hemispherical TNT standard
5-11
NAVSWC TR 91-102
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5-1
NAVSWC TR 91-102
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NAVSWC TR 91-102
REFERENCES
1. Ammunition and Explosives Safety Standards, DOD 6055.9-STD, change 2,28 Oct 1988.
2. Scale Model Igloo Magazine Tests, ASESB Technical Paper No. 4, Aug 1946,
AD 223 342.
3. Igloo and Revetment Tests, ASESB Technical Paper No. 5, Oct 1946.
4. Sound, A. R., Summary Report of Earth Covered, Steel-Arch Magazine Tests,NOTS TP 3843, Jul 1965, AD 619 241.
5. Weals, F. H., ESKIMO I Magazine Separation Test, NWC TP 5430, Apr 1973.
6. Weals, F. H., ESKIMO II Magazine Separation Test, NWC TP 5557, Sep 1974,AD 000 089.
7. Weals, F. H., ESKIMO III Magazine Separation Test, NWC TP 5771, Feb 1976.
8. Weals, F. H. and Wilson, C. H., ESKIMO IV Magazine Separation Test, NWCTP 5873, Mar 1977, AD A039 343.
9. Weals, F. H. and Finder, B., ESKIMO V Magazine Separation Test, NWCTP 6076, Feb 1979, AD A070 918.
10. Tafoya, P. E., ESKIMO VI Test Results, NCEL TR R889, Nov 1981,AD B064 461.
11. Murtha, R. N. and Beyer, M. E., ESKIMO VII: Test Data Report,NCEL TM 51-86-26, Dec 1986.
12. Lewis, M. J., Friesenhahn, G. J., and Nash, P. T., MK 82 Buffered Storage TestSeries: Part I-Technical Report, MMW-TR-87-C77865A, Dec 1988.
13. Lewis, M. J., Friesenhahn, G. J., and Nash, P. T., MK 82 Buffered Storage TestSeries: Part II-Data Report, MMW-TR-87-C77865A, Dec 1988.
14. Lewis, M. J., Friesenhahn, G. J., and Nash, P. T., MK 84 Buffered Storage TestSeries: Part I-Technical Report, MMW-TR-87-50102AC, Dec 1988.
15. Lewis, M. J., Friesenhahn, G. J., and Nash, P. T., MK 84 Buffered Storage TestSerLes.- Part II-Data Report, MMW-TR-87-50102AC, Dec 1988.
6-1
NAVSWC TR 91-102
REFERENCES (Cont.)
16. Lewis, M. J., Friesenhahn, G. J., and Nash, P. T., Modular Igloo Test: DataReport, MMW-TR-88-71002 AC, Dec 1988.
17. Reeves, H. and Robinson, W., Hastings Igloo Hazards Tests For Small ExplosiveCharges, ARBRL-MR-03356, May 1984.
18. Swisdak, M. M., "Procedures For the Analysis of the Debris Produced ByExplosion Events," Minutes of the 24th Department of Defense Explosives SafetySeminar, St. Louis, MO, Aug 1990.
19. Kingery, C. N. and Bulmash, G., Airblast Parameters From TNT Spherical AirBurst and Hemispherical Surface Burst, ARBRL-TR-02555, Apr 1984.
20. Kingery, C. N., Air Blast Parameters Versus Distance For Hemispherical TNTSurface Bursts, BRL Report No. 1344, Sep 1966.
6-2
NAVSWC TR 91-102
APPENDIX A
FRAGMENTATION[DEBRIS DATA
NOTS TEST 5
Donor: Three complete missiles-total weight of energetic material = 1,275 pounds
Date: 4 April 1963
A-I/A-2
NAVSWC TR 91-102
FRAGMENT DISTRIBUTION, TEST NO. 5
FragmentID No. Description
1 Large piece corrugated steel arch, #1.2 Four large pieces corrugated steel arch (in immediate vicinity
of crater and near acceptor igloo C), #2.3 Concrete fragment with reinforcing rods (11" x 14" x 17"), #3.4 Bottom right side of donor door frame and pilaster, #4.5 Motor entrance nozzle, #5.6 Top piece of south door of donor (45" x 42"), #6.7 Bottom piece of south door of donor (51" x 56"), #7.8 Piece of north door of donor (44" x 38"), #8.9 Piece of corrugated steel arch (45" x 38").
10 Small (about 5 Ib) concrete fragment (6" x 7" x 8").11 Large concrete fragment with reinforcing rods (40" x 29" x 17").12 Large concrete fragment with reinforcing rods (39" x 26" x 16").13 Motor exit nozzle.14 Piece of motor (about 8 Ib).15 Piece of motor (about 10 Ib).16 Piece of motor (about 5 Ib).17 Limitation of debris.18 Large piece of concrete with reinforcing rods. Part of donor
door frame and pilaster (est. 6' x 20" x 18").19 Piece of door frame.20 Motor entrance and exit nozzles (attached).21 Motor exit nozzle.22 Large piece metal door frame.23 Concrete fragment (about 50 Ib).24 Piece of donor door (24" x 24").25 Plow-shaped piece of donor metal door frame.26 Piece of metal donor door frame.27 Part of donor door hinge-strap.28 Small part of internal door framing.
A-3
NAVSWC TR 91-102
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NAVSWC TR 91-102
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NAVSWC TR 91-102
Appendix E
ESKIMO VI DEBRIS STUDY
Figure E-1 summarizes the results of a debris study conductedfollowing the ESKIMO VI test. The objective of the study was to quan-tify the amount and size of fragments generated by the test. Thesedata will be used to estimate initial velocities of the particles and willbe entered into the NCEL data base for explosion-generated fragmenta-tion. Only large items were listed (tabulated in Table E-l) out to arange of about 2,000 feet. Special attention was paid to the wingwalltrajectories (items 21 and 22) since they were the largest projectilesgenerated by the test. In general, most fragments were generated bythe roof breakup.
Figure E-2 illustrates the soil distribution following the test.e19 0
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Form ApprovedREPORT DOCUMENTATION PAGE OMB No. 0704-0188
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28 January 1991
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
A Reexamination of the Airblast and Debris Produced by ExplosionsInside Earth-Covered Igloos
6. AUTHOR(S)
Michael M. Swisdak, Jr.
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Naval Surface Warfare Center (Code RI 5)10901 New Hampshire AvenueSilver Spring, Maryland 20903-5000
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Department of Defense Explosives Safety Board2461 Eisenhower AvenueAlexandria, VA 22331-0600
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13. ABSTRACT (Maximum 200 words)
The airblast and fragmentation produced by explosions inside earth-covered explosive storagestructures (IGLOOS or bunkers) have been reexamined and assembled into one document. The data wereexamined with the following questions in mind: (1) How do they compare with current Department ofDefense Standards? (2) Can the data be scaled to produce general empirically-derived predictionequations? (3) I)o the structures tested during the Air Force Buffered Storage Test Program come fromthe same data family? These goals were met. Generalized prediction equations (with confidence limits)are provided for airblast. It was discovered that there is a major deficiency in the data relating to thedebris/fragmentation produced by explosions in such structures.
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