The U.S. Marines have suspended the development of the robotic pack mule created by Boston Dynamics for its contract with the Pentagon's research arm, Defense Advanced Research Projects Agency or DARPA. This came after AlphaDog, which is also known as the Legged Squad Support System or LS3, proved to be too noisy for actual Marine operations.

AlphaDog was built to support troops on the field by carrying up to 400 pounds of equipment. In addition, it is also capable of running 24 hours straight for 20-mile mission on rough terrain, according to NBC News. It is made of metal, has a built-in gas engine and voice control that allows it a certain degree of autonomy absent in older robot used for the same purpose. What all this means is that the machine can keep more Marines on the fight. Watch it in action in the video below.

However, the noise generated by AlphaDog's gas-powered engine outweighed its utility. It is too loud, recalling the sound of angry swarm of bees, Ars Technica noted. "As Marines were using it, there was the challenge of seeing the potential possibility because of the limitations of the robot itself," Kyle Olson, a spokesman for the Warfighting Lab, said in Military report. "They took it as it was: a loud robot that's going to give away their position."

In addition, the AlphaDog is also hard to repair.

Boston Dynamics has created a quieter version, which is the electric-powered and hydraulically actuated version called Spot. This pack mule is significantly less noisy, but it can only carry 40 pounds of weight. The Spot project was also shelved along with AlphaDog.