The B61-based "Robust Nuclear Earth Penetrator:" Clever retrofit or headway towards fourth-generation nuclear weapons?

TL;DR

The paper evaluates the feasibility and technological limitations of the B61-based 'Robust Nuclear Earth Penetrator' and suggests its development may be driven more by technological and political factors than military necessity.

Contribution

It provides a technical assessment of the capabilities and limitations of earth-penetrating nuclear devices based on existing technology and discusses the strategic motivations behind their development.

Findings

Building a B61-7 based earth penetrator is scientifically feasible but technically challenging.

Marginal improvements are possible with better materials and components.

The program may be motivated more by technological advancement and political factors than military needs.

Abstract

It is scientifically and technically possible to build an earth penetrating device that could bury a B61-7 warhead 30 meters into concrete, or 150 meters into earth, before detonating it. The device (based on knowledge and technology that are available since 50 years) would however be large and cumbersome. Better penetrator materials, components able to withstand larger stresses, higher impact velocities, and/or high-explosive driven penetration aids, can only marginally improve the device. It is concluded that the robust nuclear earth penetrator (RNEP) program may be as much motivated by the development of new technology directly applicable to next generation nuclear weapons, and by the political necessity to periodically reassess the role and utility of nuclear weapons, than by the perceived military need for a weapon able to destroy deeply buried targets.