Effects of Nuclear Earth-Penetrator and Other Weapons (2005) / Chapter Skim
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4 Effectiveness of Nuclear Weapons Against Hard and Deeply Buried Targets
4 Effectiveness of Nuclear Weapons Against Hard and Deeply Buried Targets
Pages 30-51
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From page 30... ...
The following are elements of target destruction: · Finding, identifying, and characterizing the target; · Weapon-system survival and arrival at the target; · Weapon penetration and detonation; · Energy coupling of weapons effects to the ground; · Shock propagation through the ground to the target facility; and · Response and vulnerability of the target facility. Finding, Identifying, and Characterizing the Target This report examines the relative effectiveness of and collateral damage associated with nuclear earth-penetrator and other weapons.
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From page 31... ...
The committee did not study the probability of any of these events. Energy Coupling of Nuclear Weapons Effects to the Ground The energy coupled by a nuclear weapon to the ground is expressed as the fraction of the total weapon yield converted to kinetic energy of downward-moving solid or nonvaporized ground material.
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From page 32... ...
1/3 = 0.45) , the ground-shock-coupling factor is about 20, which is equivalent to a contact burst of about 6.0 megatons.4 This example illustrates the "efficiency" of an earth-penetrator nuclear weapon in generating comparable levels of damaging ground shock at target depth with significantly lower yield relative to a surfaceburst or airburst weapon.
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From page 33... ...
, a 300 kiloton weapon would need to be buried about 800 meters6,7 and the emplacement hole would need to be carefully stemmed.8 Because the practical penetration depth for an EPW is but a small fraction of the depth for full containment and the penetration hole would not be stemmed, there will be surface venting, prompt and residual nuclear radiation, and fallout effects from an EPW. For maximum energy coupling, analysts are most interested in the maximum depths.
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From page 34... ...
Nonetheless, the design and vulnerability assessment methods derived from this test experience underlie many of today's target-planning procedures (e.g., determination of the ground vulnerability number (GVN) or the characterization of the hardness of underground facilities by the Defense Intelligence Agency)
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From page 35... ...
This test is scheduled for late 2005. Ground-Shock Attenuation with Depth The effectiveness of nuclear weapons against deeply buried targets can be estimated by calculating the intensity of the ground shock in the vicinity of the buried target in relation to target hardness.
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From page 36... ...
At this range, target hardness expressed in terms of peak free-field stress is about 1 kilobar. Thus, either the 5.6 megaton contact burst or 300 kiloton EPW at 3 meters' depth of burst can drive damaging levels of ground shock to depths of around 350 to 400 meters (range to effect)
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From page 37... ...
and "damage equivalent" 5.6 Mt contact burst.
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From page 38... ...
As indicated in Table 4.1, the effectiveness of weapons with two target-damage potential equivalent (a 300 kiloton EPW at 3 meters' depth of burst and a 5.6 megaton contact burst) can differ by about 20 percent (yield factor variation of 60 percent)
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From page 39... ...
TARGET DAMAGE PROBABILITY ESTIMATES This section explores the destructive capabilities of various nuclear weapons -- ones that are "contact burst" at the ground surface, ones that penetrate the surface, and ones that are burst in the air. The calculations were done using PDCALC (see Attachment 4.1 in this chapter)
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From page 40... ...
needs to be of sufficient yield to be effective against targets of interest. Note: CEP = circular error probable (i.e., accuracy)
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From page 41... ...
Examining these figures, one observes the following: · The effectiveness of a 250 kiloton contact burst is about the same as that of a 10 kiloton EPW, as expected from the analysis earlier in the chapter showing the 15 to 25 yield factor for equivalent ground shock. · Accuracy (i.e., CEP)
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From page 42... ...
While PDCALC does not contain any nuclear weapons effects models, it utilizes VN to specify the hardness of targets to various nuclear weapons effects such as overpressure, dynamic pressure, cratering, ground shock, thermal radiation, and initial nuclear radiation. The vulnerability of a deeply buried target is given by a 10-character ground vulnerability number (GVN)
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From page 43... ...
basement bunkers (Figures 4.14 through 4.18) are generally under 30 psi, the chemical weapon/biological FIGURE 4.8 Contact burst with 100 meter circular error probable (CEP)
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From page 44... ...
For a fixed CEP, effectiveness is not strongly dependent on target hardness. Deeply Buried Target 1 · Site Geology: Granite · EPW at 3 m Depth of Burst · 100 m CEP 0.8 3 4kbar 1 kbar 300 kt 0.6 1.5 kbar Damage of 0.4 Probability 3 4 kbar 1 kbar 10 kt 0.2 1.5 kbar 0 0 100 200 300 400 500 600 700 Target Depth (m)
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From page 45... ...
120 Deeply Buried Target ¥ Site Geology: Granite 100 ¥ Target Hardness: 1 kbar ¥ Contact Burst 80 (m) ¥ PD = 0.95 CEP 60 1 Mt 40 250 kt 20 0 0 50 100 150 200 250 Target Depth (m)
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From page 46... ...
(kt) ield Y eapon W FIGURE 4.14 Contact burst against surface and near-surface point targets.
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From page 47... ...
FIGURE 4.16 Large, hard, area targets vulnerable to contact or fallout-free height of burst (HOB) , with weapon circular error probable (CEP)
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From page 48... ...
kt( 100 m CEP Yield 100 Weapon 10 m CEP 10 10 psi 50 psi 100 psi 500 psi 1000psi 5 ksi 10 ksi 50 ksi 1 10 20 30 40 50 60 Target Vulnerability Number FIGURE 4.18 Fallout-free height of burst (HOB) 180 W 0.4: yield for probability of damage (PD)
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From page 49... ...
Figure 4.15 is similar to Figure 4.14, except that the weapon is detonated at the fallout-free HOB. Comparison of Figures 4.14 and 4.15 shows the following: · The minimum yield for a particular target vulnerability level is somewhat lower for the contact burst owing to higher air-blast levels predicted at the lower detonation altitude.
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From page 50... ...
6. Based on a historical rule that requires a minimum depth of burst of 183 meters or a scaled depth of burst of 122 m/kt1/3 to ensure containment at the Nevada Test Site for a carefully stemmed emplacement hole.
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From page 51... ...
1974. Mathematical Background and Programming Aids for the Physical Vulnerability System for Nuclear Weapons, Washington, D.C.
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