I’ve been asked a lot in the past couple of days about the significance of the ‘missile defence’ aspect of Prime Minister Turnbull’s announcement ^[1] about the combat system for the future frigates. That’s not surprising, given some of the things the PM said:

This decision will maximise the Future Frigate’s air warfare capabilities, enabling those ships to engage threat missiles at long range. A number of states, notably of course, North Korea, are developing missiles with advanced range and speed. We must have the capability to meet and defeat them.

Each of the first two sentences in that quote is correct in isolation. But juxtaposed like that, they potentially give a misleading impression that the future frigates will be capable of dealing with threats to Australia from ballistic missiles launched from North Korea. Mr Turnbull also told the press ^[2] that the nation’s naval capability is ‘stronger than ever at every level and in every field, whether it is defending Australia from regional or global threats, from threats from rogue states like North Korea’.

Before I explain why that isn’t quite the case—at least for now—I should say that the decision that was announced seems to be a very good one. As James Mugg and I wrote last week ^[3], there are good reasons to build on the success of both the US Navy’s Aegis combat system and the combination of the locally designed and built CEAFAR radar and Saab 9LV combat system. How they’ll all come together as a single system of systems in the future frigates remains to be determined.

I’ll also note that we shouldn’t lose sight of the fact that this week’s decision is only part of the story for the frigates. In government policy documents, they have been described as ‘optimised for anti-submarine warfare’ (ASW). The air defence systems of this week’s announcements have nothing to do with ASW, and we won’t know what the ASW capabilities will be until the hull and the ASW sensors are chosen sometime next year. For now, the state of play could be summarised as ‘jack up ship, fit air defence systems’.

What we do know is that the air defence combat management system will include both Aegis (presumably the new baseline 9 or some future derivative) and 9LV, and that the radar will be a more capable evolution of the smaller CEAFAR system now on the Anzac-class frigates. Aegis brings with it a capability against short- to medium-range ballistic missiles ^[4], and the new CEAFAR radar will exploit a wider range of frequencies that will give it the ability to detect airborne threats of all kinds, including ballistic missiles inside or outside the earth’s atmosphere.

So there’s no doubt that Australia’s capability for ballistic missile defence (BMD) will improve markedly when these ships are delivered. (And, for that matter, when the Hobart-class air warfare destroyers are upgraded sometime next decade.) But it’s worth understanding what we will and won’t have. As Rod Lyon and I have written before ^[5], BMD is

workable against short-range missiles, launched in small numbers, and endowed with simple countermeasures. Once any of those three variables change, BMD becomes significantly more challenging. If all three change—and the defensive system is confronted by long-range missiles, launched in large numbers, with sophisticated countermeasures—BMD will surely fail.

The first and foremost role of any ship-borne air defence system is to protect the ship and those around it, so that the navy can pursue its other tasks. As well as cruise missiles, ballistic missiles are part of the threat spectrum, but they are of a shorter-range type—the term of art is ‘theatre ballistic missiles ^[6]’—not intercontinental ballistic missiles (ICBMs) with the range required to target Australia from North Korea. To provide theatre defence, the US Navy employs SM-2 and SM-6 missiles for in-atmosphere interception and the larger SM-3 for exo-atmospheric shots.

Targeting incoming ICBMs is formidably difficult because of their very high re-entry speeds. It’s not impossible, and the US has successfully intercepted one ^[7], but it didn’t do it with the type of missile found on its warships. The ground-based interceptor missile ^[8] weighs over 20 tonnes and is 16 metres long. Surface vessels can’t deploy such weapons. In comparison, the SM-3, the largest weapon in the SM family, weighs 1.5 tonnes and is 6.55 metres long.

That’s not to say that surface vessels can’t play a role in national BMD, but probably not as ‘goalkeepers’ parked off the Australian coast waiting for an incoming missile to knock down—which they’ll probably fail to do. There are claims that ships armed with SM-3 missiles could provide continental defence ^[9], but they seem to be optimistic (see the comment below that article), and the ground-based interceptor will always have better performance in that role.

A possible (though untested) approach might be to deploy them off the coast of a launch site (for example, in the Sea of Japan or the Yellow Sea in the case of North Korea) and engage missiles in the boost phase immediately after launch. That sort of operation would probably have to be done in coalition with the American and Japanese navies.

The take-home message is that Australia is heading down the road of acquiring a formidable ability to protect its fleet at sea from a range of credible air threats, as well as the ability to work with partners to tackle long-range missiles at their source. But don’t throw away those bomb-shelter plans just yet—we aren’t going to have a national defence system anytime soon.