A while back, I mentioned a Darpa plan to have soldiers survive major injuries -- despite losing half or more of their blood. In this month's Wired magazine, I've got a short piece on the Darpa project, with a few more details.

When marine mammals like whales and seals dive deep, they let sections of their bodies go cold, cutting their metabolic rates dramatically. Darpa hopes that drugs or tech might allow soldiers to pull off the same trick - the agency's goal is to enable a rat to survive more than six hours after 60 percent of its blood has been drained.

Even Darpa managers admit it's far-fetched. Plan B: minimize bloodshed at the source, including spurting arteries. The Deep-Bleeder Acoustic Coagulation project aims to build on the work of researchers at the University of Washington and elsewhere. They're using concentrated, intense sonic blasts to heat the damaged cells. "Focused ultrasound allows a noninvasive method of cauterizing" - without fire or a laser - the scientists say. But these specialized ultrasound machines are big and bulky – and need an expert hand to guide them. Darpa's looking for a portable emitter for combat that doesn't need an expert operator.

In a recent report, Darpa worried that flesh-and-blood soldiers could become the "weak link" in the military chain. This is one of a bunch of ways the agency is planning to make it stronger.