One moment it's a chilly afternoon. But as I learned, in the very next moment, and without warning, your chest and neck feel like they've gotten a blast of unbearable steam heat.

That's because of an imposing device the U.S. military calls the Active Denial System. It's an energy weapon, commonly known as the "Pain Ray," that turns electricity into millimeter wave radio frequency. And heat. Lots of heat.

The military wants it to burn suspicious people who might pose a threat to a base. Yet the Active Denial System has never fired a millimeter wave in anger, despite 15 years in development. On a crisp Friday afternoon, however, the military wants the Active Denial System to burn a different target. Me.

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A field-grade officer on a grassy, calm field on the Marine base here beckons me to stand between four cones, on a spray-painted orange X. I am advised to jump sideways when the heat becomes unbearable. Whatever, I think, this isn't really going to burn me.

Especially because I can't see the Pain Ray, even though it's mounted on two big, goofy looking trucks. One model is a tricked-out green Humvee topped with a huge, flat backboard and a gun barrel; the other is much bigger, mounted on an eight-wheeled flatbed truck. Their handlers call the smaller one Ralph and the bigger one Pete. But since Ralph and Pete are seven football fields away - far beyond the reach of every other non-lethal weapon - they don't seem threatening.

This turns out to be pure journalistic arrogance.

When the signal goes out over radio to shoot me, there's no warning - no flash, no smell, no sound, no round. Suddenly my chest and neck feel like they've been exposed to a blast furnace, with a sting thrown in for good measure. I'm getting blasted with 12 joules of energy per square centimeter, in a fairly concentrated blast diameter. I last maybe two seconds of curiosity before my body takes the controls and yanks me out of the way of the beam.

I'm feeling the heat for a good ten seconds afterward. Then, like a genius, I go back for seconds. (Some friends from al-Jazeera wanted to film me - or so they said.) If I was, say, an Afghan at the gates of a Forward Operating Base who seemed indifferent to a flash-grilling, the guards would probably have used their regular and very lethal carbines to light me up. Instead, I decide that I don't really want thirds.

That reaction is among the reasons why the technicians at the Pentagon's Joint Nonlethal Weapons Directorate consider the Active Denial System one of their most impressive weapons. But it's a troubled system. Some of the Pain Ray's woes are technical. Others are more fundamental.

Usually the Active Denial System is described as a "microwave" weapon. That's not really correct. True, Pete and Ralph's guts contain a gyrotron, the older brother of your microwave's magnetron, through which energy passes through a magnetic field to become heat. But millimeter waves don't penetrate nearly as deeply as microwaves - only 1/64th of an inch. Even though the weapon uses much, much more energy than a microwave, the Directorate has tried and failed to use it to cook a turkey.

That's not all the Active Denial System has failed at.

The system's gone through battery after battery of tests, including one that put an airman in the hospital. (The Directorate's rejoinder: it's tested the Pain Ray 11,000 times and only two people, including that airman, got hurt.) But its "attenuation" - that is, its potency - goes down when it's raining, snowing or dusty, concedes one of its chief scientists, Diana Loree of the Air Force Research Laboratory, without specifying the degree of reduction. And that's not its biggest design flaw.

Loree says the boot-up time on the Pain Ray is "sixteen hours." So if the system is at a dead stop on a base and, say, the locals protest the burning of a Koran, guards at the entry points won't be burning anyone. The Directorate says that in a realistic deployment, the Active Denial System will be kept in ready mode - that is, loudly humming as its fuel tanks power it, or hooked up to a base's generator. But that makes it a gas guzzler, at a time when the military's trying to reduce its expensive fuel costs.

"That's something we've really got to look hard at, how do we make the system as efficient as possible," says Marine Col. Tracy Tafolla, the head of the Joint Non-Lethal Weapons Directorate, "to make sure that we're not running a lot of fuel."

Another problem is less technological and more fundamental. In 2010, Gen. Stanley McChrystal, then the commander of U.S. troops in Afghanistan, sent the Pain Ray back to the States after a deployment of mere weeks. His reasoning: it was too great a propaganda boon to the Taliban, who'd say the U.S. was microwaving Afghans, giving them cancer, making them sterile, and so forth.

The Directorate is quick to say it's done extensive "bio-effects" testing, and the system can't do any of that - so, surprise, Taliban propaganda is bogus. But commanders in Afghanistan may not be so quick to embrace the Pain Ray while Afghan tempers stay inflamed. The system is effectively in limbo, as none of the services want to purchase it - and it hasn't even been upgraded since 2010. It's fundamentally the same Pain Ray that McChrystal returned to sender.

That's actually why I've been burned. The military's interest in bringing the press out to Quantico was basically to generate a rare round of good-news stories for the system. That stings worse than my shoulder.