Half the US forces in Afghanistan may be coming home, but K-MAX, the little unmanned helicopter, will stay until the end. A pair of the remote-controlled cargo choppers arrived in Afghanistan in late 2011 for what was billed as a short-term experiment, but the Marines liked it so much that the trial deployment was repeatedly extended, and now the military has confirmed it will keep them on “indefinitely.” (The extension was first reported yesterday by Reuters). Three love letters to the remote-controlled cargo chopper from military officers, obtained exclusively by Breaking Defense, show why.

Technologically, K-MAX is just plain neat. It’s a small one-man chopper built by Kaman Aerospace Corp. – originally for logging operations, where it airlifted tree trunks out of tight areas . It was converted to a remotely piloted vehicle by Lockheed Martin. Tactically, K-MAX allows delivery of supplies to forward outposts by air, without risking human pilots or, worse yet, sending ground convoys through the gauntlet of Taliban ambushes and roadside bombs.

“What stood out most in my mind … was the permanent scorch marks burnt into the earth up and down ‘ambush alley,'” recalled Marine Corps Maj. Kyle O’Connor, who served in Afghanistan in 2004 and 2011. So many improvised explosive devices (IEDs) had gone off in one narrow mountain pass, an unavoidable chokepoint for US supply convoys, that “that stretch of road continually had scars marking where explosions had scorched the earth,” O’Connor wrote in a letter endorsing the K-MAX for the prestigious Collier Trophy. “Those memories,” he went on, “are what drove me to be part of a program meant to save lives by limiting the amount of exposure our ground convoys had to danger”: the unmanned K-MAX, whose first six-month deployment had O’Connor in command.

“Every piece of cargo flown via [K-MAX] is one piece of cargo that doesn’t need to put personnel in harm’s way going by ground convoy,” O’Connor wrote. Unlike manned choppers, “since it was an unmanned system, we were able to conduct flights during inclement weather when other helicopters couldn’t fly,” added O’Connor, a pilot himself. “We flew during the night, in the rain, dust and high wind.”

K-MAX is also cheaper than manned choppers, according to statistics from the Navy admiral overseeing the program for the Marines. K-MAX cost “less than $1,400 per flight hour,” wrote Rear Adm. Mathias Winter, Naval Air Systems Command (NAVAIR) program executive officer for unmanned aviation, “an order of magnitude less than other manned rotary wing assets in the inventory.” A big part of that low cost is that K-MAX has required less than 90 minutes of maintenance on the ground for every 60 minutes in the air, wrote Winter, yet remained mission-capable 94 percent of the time.

K-MAX “saves lives every day by taking Marines and Soldiers out of harm’s way and convoys off the road,” wrote a third officer, Army Col. Paul Howard, who coordinates K-MAX support from the Army’s Research, Development, and Engineering Command (RDECOM). “The need for unmanned resupply with remain in Afghanistan for an indefinite amount of time.”

As troop numbers come down and US forces are spread more thinly on the ground, the distance and danger truck convoys must cover will only increase, and aerial resupply – especially aerial resupply with no pilots exposed to danger from the Taliban or the notorious Afghan weather – will only become more attractive.

That said, K-MAX is not a silver bullet for logistics. First of all, it’s not a truly autonomous robot: It requires a pair of human operators running it by remote control from the launch site and a third person at the destination to direct it where to drop the cargo, either by remote control or by placing a hockey-puck-sized homing beacon. In between, it flies automatically along a pre-set course, although the operators can always take back control to evade enemy fire or other hazards.

Further, while K-MAX is cheaper than manned helicopters, it still carries a lot less cargo per dollar than old-fashioned trucks. K-MAXes have delivered 2.7 million pounds of cargo in Afghanistan so far — an impressive figure — but it took them 932 flights for what amounts to 270 truck loads. (Oshkosh, interestingly, developed an experimental unmanned truck called TerraMax, also for the Marine Corps).

In a place like Afghanistan, of course, those ground convoys aren’t so cheap because they require escorts and sometimes get blown up anyway, at a terrible cost not just in property but in human lives. But against a better-armed enemy than the Taliban – one with shoulder-fired anti-aircraft missiles or even just a lot of heavy machineguns – an unmanned aircraft might not be able to evade enemy fire, either.

That’s perhaps the reason why the Marine Corps has not ordered more K-MAX aircraft than the two now in service. Nor did K-MAX win the Collier Trophy for which the three officers quoted above endorsed it, although since the winning competitor was the NASA Mars rover, Curiosity, the competition was pretty stiff. Nevertheless, whether on Mars or in Afghanistan, robots are getting ever better at extending human capabilities, without risking human lives, in some very hazardous places.