Earlier today, India test-launched a short-range Agni I missile, described in press reports as "nuclear capable." What's a nuclear-capable missile?
At a minimum, any missile that can tote the crudest of nuclear devices. Arms experts estimate that the least sophisticated warheads, like those in India's arsenal, will weigh a minimum of 500 kilograms. To be deemed "nuclear capable," then, a missile must simply be able to deliver the 500 kilogram payload to a target. The category is often further limited to missiles with ranges greater than 300 kilometers, as that is considered the smallest possible distance between two nuclear combatants. (The distance and carrying standards are laid down by the 33-nation Missile Technology Control Regime, a consortium that restricts the export of flying rockets.)
For an advanced member of the nuclear club, like the United States, the weight issue is a rather piddling one—the American military has the technology to miniaturize nuclear arms virtually at will, as evidenced by the number of "backpack" bombs in the Cold War arsenal. India, on the other hand, is still fiddling with fat, unwieldy contraptions and thus must piggyback its nukes on massive rockets like the Agni I. (Many observers believe that Pakistan, which purchases its conventional missiles from North Korea, may be slightly ahead of its neighbor in the subcontinent's arms race, at least in terms of getting well below the 500 kilogram benchmark.) The lighter the warhead, the better the chance a military has of shoehorning it into a stealthier, more agileprojectile, such as a Cruise or Tomahawk missile. The U.S. arsenal boasts nuclear-tipped versions of both.
Were a nuclear confrontation to break out between the two powers, chances are the weapons would be delivered via aircraft rather than rockets. Test launches make for impressive gunboat diplomacy, but the failure rates for ballistic missiles make them a dicey gamble, especially for a still-nascent nuclear nation. And, of course, a missile can't be recalled once launched, no matter how successful last-minute diplomatic talks may be. It's marginally safer to have the bombers circling.
Explainer thanks Jon Wolfsthal of the Carnegie Endowment for International Peace.