It takes about six minutes for a firefighter with a full load of gear to reach the top of a 30-story building by running up the stairs–and when he gets there, he’s tired. A group of MIT students have designed a rope-climbing device that can carry 250 pounds at a top speed of 10 feet per second. They have a contract to make the climbing device for the U.S. Army for use in urban combat zones, and they hope to make it available to rescue workers.

The students founded a company, Atlas Devices, based in Cambridge, MA, to commercialize the device, which is about the size of a power drill. Nathan Ball, Atlas’s chief technology officer, says that such a device has never been made before because the batteries and motors needed to generate enough power for rapid rope ascents have been bulky and heavy. Atlas’s 20-pound machine uses a fast-charging, high-power-density lithium-ion battery made by A123 Systems, based in Watertown, MA. (See “More Powerful Batteries.”) To use the device, a soldier or rescue worker wraps a rope around its cylinder and clips it to a harness worn around the waist.

Ball says the biggest design challenge in making the climber was a mechanical one. “We had to come up with a clever mechanism to grip the rope securely while not damaging it,” he says. The device relies on the capstan effect: the more times a rope is wrapped around a cylinder, the stronger the device’s grip on the rope. To take advantage of the effect, the MIT students had to make a device that could tightly grip a few turns of a rope while still rapidly advancing it.

The Atlas rope climber can be attached at any point along a rope–a rescue worker could get onto a line from a second-story window, for example. It takes about 10 seconds to wrap the rope three times around the capstan. The climbing device can’t shoot a rope up to the top of a building, but Ball says the army already uses grappling hooks to set ropes that soldiers must then climb by hand. A first wave of firefighters or other emergency workers might climb up using the stairs and set a rope for others to follow, or a soldier might be dropped to the top of a building from a helicopter and set a rope.