What Happens When a Nuclear Warhead Is Intercepted Mid-Air?

The interception of a nuclear warhead remains one of the most complex and critical aspects of strategic national security. Consider the scenario where a warhead with a nuclear warhead is targeted and destroyed by an interceptor approximately 50 kilometers in the air. Would this still cause significant damage on the ground?

Understanding the Missile Intercept Process

The powered phase of an ICBM (intercontinental ballistic missile) or SLBM (submarine-launched ballistic missile) flight lasts only a few minutes after launch. These initial minutes are the only vulnerable period over the launch site. Once past this phase, the missile's warheads, which are usually traveling in a ballistic trajectory, are difficult to hit due to their spread out pattern and hypersonic speed, immune to EMP (Electromagnetic Pulse) and radar detection by ionized gas shrouding them.

While the warheads themselves are hard to intercept, the successful interception of one would most likely result in a dirty explosion rather than a full-scale nuclear detonation. The complex physics package of a Teller-Ulam device requires a very specific sequence of events to occur for a thermonuclear explosion. Even if detonation happens, the damage would be minimized compared to a full-scale blast.

Challenges in Intercepting Nuclear Warheads

Intercepting a nuclear warhead is an incredibly difficult task. Interceptors must contend with sophisticated technologies such as MIRVs (Multiple Independently targetable Reentry Vehicles) and decoys that make a successful 100% interception improbable. Moreover, the terminal phase of interception lasts only 12 to 15 seconds, presenting a brief but critical opportunity for the interceptor.

Aftermath of Successful Interception

If a nuclear warhead is intercepted successfully at an altitude of 50 kilometers, the aftermath would involve the fallout of radioactive materials. Many modern warheads consist of a fission/fusion mix, with a primary fission stage and a secondary fusion stage. These warheads are generally not designed to be critical or armed until a certain altitude. In theory, this provides the launch commander an option to destroy the missile in the air after launch. However, there are scenarios where accidental or false launch indications could occur. In such cases, only a self-destruct mechanism or BMD (Ballistic Missile Defense) could prevent disaster.

Even with successful interception, the remaining radioactive material could still pose significant risks. These materials, due to their long half-life, could cause severe environmental damage and health risks in the areas where they fall. The extent of damage would be less than a full-scale detonation, but still considerable. Meteorological factors play a crucial role in determining where the radioactive materials would land. For instance, wind patterns can shift the fallout over different geographic areas.

Historical Precedents

A significant historical example is the B-52 crash in Palomares. In 1966, a B-52 carrying four nuclear bombs collided with a fuel tanker, leading to a breakup. Despite the bombs not detonating due to not being armed, there was significant environmental contamination from the leaking radioactive materials, highlighting the potential for dirty fallout even without a full-scale explosion.

In conclusion, while intercepting a nuclear warhead at around 50 kilometers can prevent a full-scale explosion, the resulting fallout would still pose significant risks and damages.