Spears and Shields: A brief look

America’s National Intelligence Council said in 1999 that China and Russia had devised numerous countermeasures to protect offensive missiles and were probably willing to sell the technology.

A statement in May by the office of the assistant secretary of defence for research and engineering noted that the proliferation of such advanced countermeasures was rendering America’s missile defences “no longer practical or cost-effective”.

Among nuclear powers, neither North Korea nor Pakistan is presently capable of building a ballistic-missile triggering system that is able to detonate a nuclear payload if an interceptor was drawing near. But with time and enough effort, this could change: At least one type of nuclear device detonated by North Korea “is not inconsistent” with efforts to build a bomb designed for an Electro Magnetic Pulse (EMP) attack. Effects of a EMP depend on factors including the altitude of the detonation, energy yield, gamma ray output, interactions with the Earth's magnetic field and electromagnetic shielding of targets, but in any case rapidly changing electric fields and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges. The threat grows as potential attackers continue to acquire “more complex, survivable, reliable and accurate” ICBMs equipped with countermeasures

Land- and Sea-Based Spears: ICBMs

The trajectory of an ICBM runs in three consecutive phases: Atmosphere-Space-Atmosphere. The first phase is the "easyest" one in order to incercept the ICBM, so it is neccesary to place interceptors close enough to reach the missile before it leaves the atmosphere... But it is not easy, indeed. Ronald Reagan hoped to put interception satellites into low orbit, but the “Star Wars” scheme, as it was known, presented three main handicaps:

1. It would have required a lot satellites costing billions of dollars.
2. Satellites could be shot up with missiles
3. Satellites could be blinded with lasers

Space-Based Spears: Satellites

• In December 2012 North Korea launched a satellite on a southerly track. The launch reveals a vulnerability in missile defences which could be exploited for an EMP attack.
• A nuclear device fitted into a subsequent southerly launched satellite would circumvent America’s defences against long-range weapons because these are positioned to hit warheads flying from over the North Pole, not those coming from the south.
• A nuke concealed in a satellite in an orbit used by many civilian satellites could be detonated on a flyover above America. There is no point in having a missile-defence system that cannot prevent such an attack.

Air-Based Shields: Lasers and interceptors

• MDA believes that aircraft-mounted anti-missile Solid-state lasers may “play a crucial role” in defeating ICBMs during the boost phase. Experiments have begun with General Atomics’ Reaper and Boeing’s Phantom Eye drones.
• Dale Tietz, a former senior Star Wars official, says that North Korean missiles could be prevented from reaching space by just three interceptor-armed Global Hawk UAVs.

Sea-Based Shields: Aegis

• 30 of America’s warships carry Aegis anti-missile systems, but these were designed to strike shorter-range missiles.
• With recent upgrades, Aegis is thought to be capable of intercepting warheads in space, in limited circumstances.
• With additional radar near America’s east coast, Aegis destroyers in the Atlantic could theoretically intercept ICBMs coming from Europe and Asia.

Ground-Based Shields: GMD

• The GMD system consists of an “exoatmospheric kill vehicle” with steering rockets and its own X-Band Radar system.
• There are 30 GMD interceptors at Vandenberg AFB and Fort Greely in Alaska.
• The MDA has begun work at Fort Greely to prepare for a field of silos that will contain an extra 14 interceptors by 2017.