For America's Submarine Force, both transformational working concepts and innovative deployed capabilities have been multiplying in recent years at a breathtaking pace. Some projects now in the pipeline -- which I'll cover in my next essay -- include firing supersonic Sidewinder anti-aircraft/anti-ship missiles from a submerged SSN's existing Tomahawk Vertical Launch System tubes, shooting clutches of conventional theater ballistic missiles out of one of a converted SSGN's (ex-SSBN's) former Trident sub-launched nuclear ballistic missile (SLBM) tubes, and launching and retrieving unmanned aerial vehicles (some armed) through the SSGN's “repurposed” seven foot inner diameter tubes. Today's discussion will focus on another timely yet controversial notion: rearming some of the latest Trident II D5 missiles with high-explosive warheads and deploying them in a few tubes on Ohio-class SSBNs -- which would continue to serve primarily in their thermonuclear deterrent roles.

An idea will be offered below which might, after further study, fix the biggest problems with fielding non-nuclear (“conventionally”) armed Tridents on an SSBN thus tasked to perform such new double duty. But first, why does this subject even come up, and just what are these problems as noted by critics?

The Pentagon has expressed the compelling need for one or more systems that achieve precision non-nuclear strike missions promptly against “time urgent targets” globally. Here precision means hitting the target with GPS-guided (or equivalent) accuracy, say a maximum miss of ten yards. Prompt means an extremely rapid cycle from receipt of intel on a target's location to munitions arriving to obliterate said target. (“Prompt” has been formally defined as one hour, so in this context it requires a weapon flight time of barely thirty minutes, even less.) Global means exactly that: the capacity to “reach out and touch someone” -- or some thing -- anywhere on Planet Earth.

Achieving this Prompt Global Strike in practice is a rather tall order. But it's absolutely necessary, to meet the expanding medley of threats America faces today and tomorrow. For one example, suppose Osama Bin Laden is spotted getting a bit of fresh air outside a cave redoubt in the eastern Afghanistan mountains. He's vulnerable, but not for very long. As another illustration, imagine a ballistic missile is spotted on a North Korean launch pad, busy being fueled before launch -- and the DPRK just fired one high-explosive missile at Japan. This second missile might carry an A-bomb. American and allied forces are exhausted and out of position due to a month-long combined exercise in southern WESTPAC -- so what do you do? Or posit that an advanced diesel sub is sitting at a pier in Iran, about to unload nuclear weapon technology smuggled by the Russia mafia via a covert rendezvous with a “neutral” merchant ship in the Gulf of Oman. That surfaced, stationary sub is a target of opportunity that, in some imaginable scenarios, we'd very much want the option to blast to pieces, before its nefarious cargo could be dispersed and trucked to Iran's hardened underground bunkers. Every minute would count.

Now comes the issue of implementing Prompt Global Strike truly promptly. This isn't as easy as it sounds. A Tactical Tomahawk cruise missile is subsonic, flying as fast as a 747, and to reach its maximum range of about 1,500 nautical miles will take more than two hours -- too long. Bombers and fighter-bombers, whether land or sea based, even if supersonic, can take just as long or much longer to penetrate to their objective, even when using stand-off weapons. Prompt Global Strike thus calls for a different approach, one based on intercontinental-range ballistic missiles. Depending on their programmed flight path, these reach speeds approaching Mach 16.

Two competing solutions are being bandied about in the Pentagon, one from the Air Force and one from the Navy. What makes the debate complex is the big fundamental risk behind Prompt Global Strike, whatever form(s) the hardware takes and regardless of which armed forces branch or branches “own” it: An intercontinental-range ballistic missile launched by America against a deserving third party could be mistaken by Russia or China as the start of a nuclear strike against them, inviting immediate retaliation by ballistic missiles armed with H-bombs. When individual warheads have yields of hundreds of kilotons, and one modern ICBM or SLBM can carry several independently targeted warheads (MIRVs), it pays to not take any chances.

Both the Air Force and the Navy, no slouches, have offered solutions to this potentially fatal drawback of Prompt Global Strike. The Air Force suggests building some new ICBM silos on America's coasts, well away from the nuclear ICBM silos in the Midwest, to reduce ambiguity of intent. The hope is that anyone likely to panic and try to nuke us due to a Prompt Global Strike attack will “realize” that these coastal launch points indicate a conventional warhead is bound for some terrorist or rogue state. This idea, unfortunately, is dependent on Russia and China having precise launch-detection sensors and flawless, utterly rigorous command-and-control -- dangerous assumptions. Open inspection of the conventionally armed coastal ICBMs, and advance notice via Hot Lines to Moscow and Beijing when a Prompt Global Strike against some bad actor is slated to occur, sound great but might not make adequate allowance for Murphy's Law. And Murphy's Law rules when the ICBM trajectories would probably pass over Russia or China or both before hitting their targets.

The Navy's suggestion is to include some Trident II D5s armed with non-nuclear warheads on SSBNs when they go on patrol. This provides our Commander in Chief with the option to use a strategic deterrent nuclear sub for a second purpose: to launch a conventional Prompt Global Strike from a stealthy platform hiding underwater. There are considerable challenges with this approach, however. Reconfiguring an SSBN to be able to fire two types of missiles -- given the maze of hardware, software, safeguards, and radiation protection already required when some of the warheads are nuclear -- could lead to expense and delay. It also requires the same vessel to have two separate logistics, maintenance, and crew training tracks, further making the arrangement sound like a bundle of nasty headaches. If the SSBN is on station in its assigned alert patrol area near Russia or China, there's the same issue with SLBMs as with ICBMs -- seemingly-nuclear trajectories coming toward countries able to shoot back at America with their own missile nukes. Or, to avoid this geographic conflict, the SSBN could cruise to a better launch point. But that takes considerable time, compromising the “prompt” part. It also takes the whole sub far off station, compromising its nuclear deterrent value, and spoiling its all-important stealth once it launches a single conventional missile.

And there's another problem which I think naysayers could never be convinced to ignore: If the same SSBN carries two types of missiles, and a conventional Prompt Global Strike order ever does comes through, what stops a worst-case tragic error where the wrong type of missile gets launched? The mistake doesn't ever have to happen. The mere possibility of it might not go over well in Congressional subcommittee hearings scheduled soon. Plus, Congress has already expressed reluctance over steps that appear to make crossing the threshold to going nuclear any easier or more likely -- a mixed missile load on...