The U.S. Marines’ famous robomules have been put out to pasture, as the larger robotic mule (LS3) was deemed too loud for combat situations and the smaller, quieter version (Spot) could not carry enough load.

The Pentagon’s main research lab announced last week it was suspending the “robomule” program.

Google's Robomules Axed: Marines Pull The Plug On LS3

The military has been working to develop autonomous robots to complement their highly successful manned drone program for some time.

History of robomules LS3 and Spot

The robomule program initially came about through a $32 million contract between the military’s Defense Advanced Research Projects Agency and Boston Dynamics signed in 2010. Boston Dynamics was eventually bought out by Google.

The original contract saw DARPA partner with the Marine Corps Warfighting Lab for the development an autonomous four-legged robot that could transport 400 or more pounds.

Another $10 million contract was awarded in 2013 for a second phase of the LS3 program to demonstrate how the quadruped robot, also known as “Alpha Dog”, would perform accompanying troops on foot through rugged terrain, carrying gear, and taking verbal and visual commands.

Of note, the contract also called for the construction of an upgraded version of LS3 with better armor and a quieter power supply.

The robo-mule was deployed as a part of the 2014 at Rim of the Pacific exercise, a large-scale military exercise across the Pacific. Both the versions saw action in a number of field tests with Marines who  used the devices on patrols and demonstrated how it could respond to commands and follow them across a variety of rugged terrains.

Current robomules are too noisy or too small

The recent use of the robomules in the Rim of the Pacific exercise also made clear some of the shortcomings of the prototype, Kyle Olson, a spokesman for the Marines Warfighting Lab, explained to  Military.com in an interview.

“As Marines were using it, there was the challenge of seeing the potential possibility because of the limitations of the robot itself,” Olson noted. “They took it as it was: a loud robot that’s going to give away their position.”

Although the robomule program spent $42 without producing a usable robot, Olson emphasized that the Marine Corps did learn a great deal about autonomous technology and its potential.

“We tend to play with things that are fanciful and strange,” Olson commented. “Learning from it was a big part, and we’re still learning.”

Of note, DARPA has several other robotics related projects in various stages of development, and the Warfighting lab is actively involved in research with drones and other unmanned vehicles, including using them for medical resupply and reconnaissance.

More on all-electric Spot robomule

The second 2013 contract included funds to develop a quieter robomule, so the team built “Spot,” a four-legged robot that looked kind of like a large dog that ran on quiet electric power. The smaller robot was put through its paces in the woods of Quantico, Virginia last year.

Although Spot was much quieter, it could just carry 40 pounds or so and didn’t include much of the advanced autonomous technology in the larger LS3.

“I see Spot right now as more of a ground reconnaissance asset,” noted Capt. James Pineiro, the Ground Combat Element branch head of the Warfighting Lab. “The problem is, Spot in its current configuration doesn’t have the autonomy to do that. It has the ability to walk in its environment, but it’s completely controller-driven.”