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The US Navy’s air defense Standard missile family evolved from the original Terrier/Tartar air defense missiles of the 1950s. And the Standard missile has been subject to a continuous series of improvements to the electronics, warhead, and motors. It’s kinda like George Washington’s hatchet- three new handles and two new blades since he owned it, but it’s still his old hatchet.

The latest production version of the Standard missile is the SM-6, or RIM-174 Extended Range Active Missile.

The SM-6 is fired from Aegis equipped DDG-51 Arleigh Burke class destroyers, and CG-47 Ticonderoga class cruisers. Since their introduction to the fleet in the early 1980s, the main battery of Aegis ships has been the semi-active radar homing (SARH) SM-2 missile. A pencil beam radar aboard the ship called an illuminator tracks the target, and the SM-2 flies toward the reflected radar energy.

But the illuminator radar has a limited range, right about 90-100 nautical miles. And improvements in search radar, and more importantly, improvements in rocket motors, means the Standard Missile family can fly much further than that.

And so the US Navy and Raytheon got together and built an improved Standard missile. The M72 thrust vectored booster from the anti-ballistic missile SM-3 was added to increase range. And a variant of the active radar seeker from the AIM-120 air to air missile was placed in the nose.

In a typical engagement, the Aegis ship’s SPY-1 radar will track a target. When an SM-6 is launched, steering commands embedded in the radar signal from the SPY-1 will tell the missile’s autopilot the best course to steer for the future point of intercept. These steering commands are regularly updated until the missile is close enough to the target that it’s own active radar seeker can acquire the target. Once that happens, the SM-6 steers itself to intercept.

Of course, now the Navy found itself with a missile that had a longer range than the Aegis system. That opened up the possibility of Cooperative Engagement Capability. Previous datalink systems such as NTDS allowed ships in the network to share a common picture of air and surface contacts (known as tracks) but the resolution was rather poor. But newer datalinks, with greater bandwidth and the resolution provided by GPS, means that a sensor can provide fire control quality resolution to the network.

For instance, let us suppose that an E-2D Hawkeye is flying a surveillance patrol in support of a carrier battle group. It detects an inbound strike of enemy aircraft. The battle group’s own Combat Air Patrol is poorly positioned to intercept. The E-2D can, however, through its datalinks, enable an SM-6 shot at the target well before the battle group’s Aegis ships even paint the strike on their radars.

Just how far can SM-6 engage?*

Well, the Navy isn’t saying. It did, however, last week announce that they’ve made the longest ranged ever surface to air missile interception using an SM-6.

There’s a lot of speculation, but the range numbers tossed out most frequently are 200 to 250 nautical miles.

That means a ship operating off Boston harbor could engage targets over New York city. And that’s pretty impressive for a missile family that started with an effective range of about 15 miles.