Nuclear Weapon Effects Tests
Some nuclear weapons effects (NWE) can be modeled mathematically using powerful computers; others, and in particular the combination of several effects, are beyond valid analytic or numerical assessment. The only way to know if friendly systems or target assets will endure a given nuclear attack may be to expose representative equipment to real nuclear explosions or to construct complex simulators which reproduce a part of the spectrum of NWE. Until the conclusion of the Limited Test Ban Treaty (LTBT) in 1963, the United States conducted atmospheric tests of nuclear weapons, and it was relatively simple to include effects testing in the experiment. By signing the 1963 accord, the United States, the UK, and the Former Soviet Union agreed to discontinue atmospheric testing, testing in outer space, and testing under water. The only environment in which nuclear devices could be detonated was underground in circumstances where radioactive debris did not drift beyond national boundaries.
In the years between 1963 and 1992 the States Parties to the LTBT conducted underground tests to study NWE. As a result of congressional action the United States unilaterally entered a testing moratorium, which was made permanent with the signing of the Comprehensive Test Ban Treaty (CTBT) in 1996. Because it is no longer considered acceptable for the United States to conduct any nuclear explosions for any reason, future U.S. assessments of the vulnerability of its systems or of potentially hostile systems will have to rely upon the use of simulation and analysis validated by comparison with the results from almost 50 years of testing.
Combinations of nuclear weapons effects pose particularly difficult simulation problems. The thermal pulse can weaken or ignite a target, permitting the blast wave to be more effective than against a "cold" object. X-ray radiation can damage electronics and protective systems, making the target more vulnerable to neutrons. EMP and transient radiation effects in electronics (TREE) can operate synergistically. Thermal effects could conceivably damage some components designed to harden a system against EMP. Low-energy x-rays absorbed by a target in space can heat surface material to the vaporization point, causing it to explode away from the system, producing shock effects within the target. The effects produced and the ranges at which they are effective depend upon the yield of the nuclear weapon and the height of burst (HOB) and may depend upon the design of the device itself.
Theoretical predictions of NWE based on computer codes and algorithms that have not been compared with experiments may not be accurate, and the details of such experiments are not generally available. Those codes and algorithms which have been validated by experiment usually contain adjustable parameters and are much more reliable predictors of NWE. Such codes are termed "substantiated." Physical simulation provides more confidence in predicting NWE because it does not rely upon the mathematical approximations of codes and algorithms but uses physical phenomena closely related to those produced by a nuclear detonation to test the behavior of real systems. But physical simulation remains "second best" compared to testing against a real nuclear detonation.
Underground testing (UGT) can provide much insight into weapon design, radiation effects (gammas, neutrons, x-rays) on military systems, selected aspects of shock and blast, thermal effects, and source region EMP (SREMP). Countries with limited defense budgets are less likely than the major nuclear powers to have had exhaustive underground testing programs.
An understanding of TREE and System-Generated Electromagnetic Pulse (SGEMP) is of critical importance in designing and building equipment that can survive a nuclear attack. It is not clear, however, that a nation having limited financial and technical resources could develop unique radiation-hardened devices and/or systems. These countries could, however, test a few critical subsystems or systems in an established foreign simulation facility. Although there are certain aspects of TREE and SGEMP technology that are of general scientific interest, for nations which have interests in the acquisition of nuclear weapons, the desire to evaluate and test systems at SGEMP and TREE dose rate levels typical of nuclear weapons is a useful indicator that they plan on nuclear combat, whether as a user or as a victim of the weapon. While TREE and SGEMP may indeed be effective, a nuclear planner without the benefit of extensive simulation and substantiated codes will probably rely on the gross NWE such as blast, shock, and thermal radiation.
In the absence of nuclear testing, simulation equipment, numerical simulation, and theoretical analysis of NWE are the only means states can verify how NWE will affect their own forces and those of their opponents in a nuclear environment. NWE simulation, as well as survivability and hardening programs, have both offensive and defensive aspects, and may be desired by both nuclear possessor states and those with neither nuclear weapons nor plans to build them.
Most of the relevant equipment and specialized software has been developed in parallel by many countries including Russia, China, the UK, and France, as well as Japan, Germany, Switzerland, Sweden, Canada, and members of the former Warsaw Treaty Organization. Although the simulation, survivability, and hardening equipment available from non-Western countries is inferior to that produced in the West ("years behind" in the case of HEMP simulation), it may be good enough to permit a nuclear aspirant to understand how to make its own equipment more survivable than otherwise. The most advanced capabilities usually only are necessary when one is trying to design equipment to be the lightest, most effective, and most efficient; when one backs away from the edge of the envelope, less-detailed analysis and testing may suffice. After all, the NATO allies operated acceptably survivable equipment decades ago.
|Join the GlobalSecurity.org mailing list|