Following is a concise summary of target destruction:

• For deeply buried targets:

  • An EPW is more effective than a contact burst of the same yield. The probability of damage for a 300 kiloton EPW at 3 meters’ DOB is equivalent to that for a 5 to 6 megaton surface-burst of the same accuracy.

  • For an EPW, yields in the range of several hundreds of kilotons to a megaton are needed to effectively hold deeply buried targets of interest at risk with a high probability of destruction.

• For surface and near-surface targets of interest, as shown in Figures 4.17 through 4.19 (in Attachment 4.2), detonating a weapon at its fallout-free height of burst could effectively destroy a target without producing local fallout, although significant casualties would result from the other weapon effects (as at Nagasaki and Hiroshima).

The Probability of Damage Calculator (PDCALC) calculates the probability of damage (PD) to targets caused by, for example, overpressure, dynamic pressure, cratering, and ground-shock coupling due to nuclear weapons effects. PDCALC can also calculate weapon radius or offset to a desired probability of damage. PDCALC handles a variety of targets, including soft urban/industrial buildings, shallow buried bunkers, bridges, silos, and deeply buried tunnels. This calculator is also used to make personnel casualty assessments.

Government agencies and contractors use PDCALC as an analytical tool for planning and studies regarding nuclear weapons effectiveness, weapon requirements, and target vulnerability and survivability. DTRA manages the development and maintenance of the calculator and sponsors the PDCALC Oversight Panel and the PDCALC Users’ Group.

PDCALC is based on two Defense Intelligence Agency publications: Physical Vulnerability Handbook—Nuclear Weapons¹¹ and Mathematical Background and Programming Aids for the Physical Vulnerability System for Nuclear Weapons.¹² DIA provides the mathematical formulations embedded within PDCALC, as well as target vulnerability information used to develop target vulnerability numbers (referred to as VN). DTRA provides nuclear weapons effects data and algorithms and structural loading and response prediction methods required to develop estimates of vulnerability. 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). GVNs are developed by DIA using the DUG1c ground-shock model. Results of depth-to-effect as a function of contact-burst yield are fit by a GVN, which is used by PDCALC. For heights of burst (HOBs) or depths of burst (DOBs) other than a contact burst, PDCALC makes use of a coupling curve to determine the equivalent contact-burst yield. This coupling curve was recently updated to incorporate the latest knowledge of energy coupling from near-surface nuclear explosions.

Currently under development is an improved GVN methodology in which DUGlc, the one-dimensional engineering ground-shock propagation code, is replaced by WinGS, a two-dimensional physics-based ground-shock code, as well as a finite-element-based tunnel response model. (See Chapter 5 for additional details.)

Front Matter (R1-R12)

Summary (1-8)

1 Introduction (9-12)

2 Hard and Deeply Buried Targets (13-17)

3 Earth-Penetrator Weapons (18-29)

4 Effectiveness of Nuclear Weapons Against Hard and Deeply Buried Targets (30-51)

5 Fallout and Tools for Calculating Effects of Release of Hazardous Materials (52-72)

6 Human and Environmental Effects (73-98)

7 Conventional Weapons (99-102)

8 Uncertainty in Estimates of Effects (103-109)

9 Conclusions (110-114)

Appendix A: Committee and Staff (115-121)

Appendix B: Agendas (122-129)

Appendix C: Equivalent Yield Factors for Energy Coupling (130-131)

Appendix D: Acronyms and Abbreviations (132-134)