Four prototype HALTT (" helicopter Alert and Threat Termination ") sensors are now on board Black Hawk helicopters and deployed to Afghanistan, as Danger Room alum Nathan Hodge reports.

四件HALTT(直升机预警与威胁解除)传感器样件目前已装在黑鹰直升机上，应用于阿富汗，如险情办公室Nathan Hodge所报道的。

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Mr. NATHAN HODGE (Writer, Jane's Defense Weekly): Well, when Ronald Reagan made his famous "Star Wars" speech back in 1983, the goal of missile defense is quite ambitious.

NPR: Missile Defense, the U.S. and Europe

Barnes, Nathan Hodge, and Yaroslav Trofimov contributed to this article.

WSJ: Obama to Speed Troop Exit

The current tensions have renewed focus on the whole U.S. missile defense program and we asked Nathan Hodge of Jane's Defense Weekly to come in and remind us what it's all about.

NPR: Missile Defense, the U.S. and Europe