Soldiers some day could go into battle equipped with an arm-like robotic exoskeleton, designed to significantly improve marksmanship. Dan Baechle, an engineer at the U.S. Army Research Laboratory at Aberdeen Proving Ground, Md., is designing the device so that it automatically stabilizes the shooter’s arm. Baechle got the idea for the robot device, called MAXFAS, years ago while watching the deployment of a similar device in the movie “Aliens.”