In a high-rise building, cyber attackers are wreaking havoc on the U.S. economy and already cost lives by taking down a power grid. The Pentagon has to take action.

The problem is that the high-rise is located in the middle of a sprawling Middle Eastern city of 12 million inhabitants. It would be easy to send cruise missiles to destroy the building, but most floors are occupied by innocents, including dozens of children.

This is a scenario military thinkers are increasingly worried about: fighting in urban environments, particularly the so-called megacities of the future, defined as having 10 million or more residents.

DARPA is thinking ahead, and has kicked off a series of programs to help warfighters operate in these complex conditions.

“As more populations across the world move to larger and larger cities, we need to understand the three-dimensionality of cities and how to operate in those very crowded, very three-dimensional spaces,” DARPA Director Dr. Steven Walker told reporters recently. “That’s going to become more important in the future.”

“We need to see around the corner and observe enemy activities before they target us,” he said. Currently, the way ground forces detect enemies is by being shot at. “Not ideal,” he noted.

Dr. Thomas J. Burns, former director of DARPA’s Strategic Technology Office (STO), said that the scenarios that scare him most are ones involving city-dwelling terrorist cells – whether they are state, non-state actors, or their proxies – which use cybertools to bring down cities around the world.

“If that becomes a reality, we are going to have to find ways to get in there, find them, and dig them out,” Burns said. “The United States military does not have a doctrine per se that they can follow to conduct warfare in those cities,” he added.

But it will soon need one.

Jean-Charles Ledé, a program manager at DARPA’s Tactical Technology Office (TTO), said: “War is a human affair. You fight where people are. The likelihood of us having to fight in the urban environment is increasing.”

 

Megacities of the Future

People move to cities to pursue opportunities. While 54 percent of the world’s population lives in urban areas, cities already account for more than 80 percent of global economic activity (as assessed by gross domestic product measures), according to the World Bank. Those numbers will only increase. The number of megacities is expected to rise from 28 in 2014 to 41 by 2030, and by 2050, 66 percent of the world’s population is expected to live in urban areas, according to a recent report by the United Nations’ Department of Economic and Social Affairs.

Fighting in urban environments is not new for the U.S. military, but the cities of the future may be vastly different from what U.S. forces have seen in the past. They pose all sorts of complications for troops, Ledé said.

Cities are not only growing bigger, they are growing taller. “The verticality element is continuing to grow, and that is a challenge for many reasons: detection, targeting, and prosecution of targets in a 3-D environment is a considerable challenge,” he said.

“The aircraft are launched automatically, and they are assigned an air corridor to deconflict with one another. Before the first drone has to fly back, the second one is sent,” Ledé said. “The person doesn’t have to do anything.”

Fighting in urban areas is marked by corner-to-corner engagements over short distances with equally short timelines, he noted. There are only seconds to discriminate between hostile actors and innocent bystanders.

“We need to see around the corner and observe enemy activities before they target us,” he said. Currently, the way ground forces detect enemies is by being shot at. “Not ideal,” he noted.

 

C3D – Drone Scouts to the Fore

DARPA’s TTO is wrapping up a program called Centralized Control for Commercial Drones, or C3D, which is using small, inexpensive unmanned aerial systems (UAS) to provide a better vanguard for troops.

The idea is to send these intelligence-gathering systems ahead of troops to make sure routes are clear, set up perimeter overwatch, and maintain surveillance on a building or intersection, said Ledé, who is C3D’s program manager. It is important that the workload is carried out automatically, he added.

Operators submit the mission they want performed through an intuitive interface. The software decides how many drones are needed and how often. “The aircraft are launched automatically, and they are assigned an air corridor to deconflict with one another. Before the first drone has to fly back, the second one is sent,” Ledé said. “The person doesn’t have to do anything.”

When the system detects something – perhaps a person of interest coming out of a building, or carrying a weapon – a warning is sent to the human operator. The system requires a great deal of autonomy, artificial intelligence, and machine vision to complete its task, Ledé added. The program already is transitioning to the Marine Corps, and has sparked the interest of U.S. Special Operations Command and the U.S. Air Force, which could use it for base defense, Ledé said.

Along with drones that serve as the eyes of ground forces, DARPA’s TTO is also working on swarms of ground and air robots that both move ahead of troops and fight alongside them.

 

OFFSET – A Swarm of Unmanned Allies

The Offensive Swarm-Enabled Tactics (OFFSET) program’s goal is to dramatically augment small-unit forces in an urban environment with upwards of 250 small ground and air robots, said its program manager, Dr. Timothy Chung.

“Can we speak a language of swarm tactics – coding as well as operator level – to convey a commander’s intent in a highly dynamic urban environment?” he asked.

OFFSET is in the beginning stages of trying to answer this question. It is expected to advance the science of swarm technology.

“Human-swarm teaming has to dramatically change compared to what we do today,” Chung said. That may give rise to what would be a new job in the military: the “swarm tactician.” This operator will have to go beyond the mouse, keyboard, and screen to control swarms of hundreds of robots, he said.

The ultimate goal will be to seize urban terrain with 250 ground and air robots. They must capture a city square, bridges, or other objectives and hold onto eight blocks for four to six hours, he said.

“We don’t exactly know what the best concept of operations is for these swarms,” he said. It could entail pushing the robot mass forward without troops, where they serve as a vanguard. Or they could march or fly amongst the warfighters. They could be called on to make first contact with enemies, then be joined by soldiers or Marines, he said.

OFFSET will have three increments. The first is based on Army and Marine Corps tactics, techniques, and procedures. It will first demonstrate isolating an urban objective with 50 robots over a two-square city block for 15 to 30 minutes. The swarm will establish a perimeter, and “put eyes on” potential avenues of attack or reinforcement.

The second objective will be based on a raid and boost the number of robots to 100. They will be expected to do building ingress, localize targets or signals of interest, and maneuver indoors and outdoors for one to two hours over four square city blocks, Chung said.

The ultimate goal will be to seize urban terrain with 250 ground and air robots. They must capture a city square, bridges, or other objectives and hold onto eight blocks for four to six hours, he said. Along with a physical testbed, the program will have a virtual testbed using synthetic technology.

“It allows us to develop swarm tactics ahead of, and at a pace faster than, technology that currently exists,” Chung said. For example, what if the robotic systems had see-through-wall sensors. What if they had unjammable communications? The software developed in the virtual testbed could then be transferred to the real world once these features are mature, he added.

The main impediment is that in a big city, the terrain is almost all non-line-of-sight. That means multi-modal solutions – radar, optical, or acoustic – he said. With high-rise buildings, the aircraft can approach from above as well.

Burns noted that rivals already are employing drones against U.S. forces. They have even used swarm tactics, although not in large numbers. These small aircraft will be particularly hard to defend against in urban environments.

Troops “need eyes 360 degrees around them and above them. You just don’t know what’s coming at you from above. The Marines and Army have seen a lot of examples in Iraq of … swarm-like IEDs,” or improvised explosive devices, Burns said.

John Waterston, a program manager in the Strategic Technology Office, said, “If we want to have freedom of movement in an urban environment, we are going to have to figure out how to deal with these kinds of threats.”

It’s relatively easy to detect and defeat a rogue drone out in a field or the middle of the desert, but not so in the cities. “The traditional sensing approaches do not work well in an urban environment,” Waterston said. There is lots of radio-frequency interference and clutter. Audio sensors have to deal with noise from cars, and radars with motion from fans in windows or people on the street.

 

Aerial Dragnet – Above the Streets and Buildings

The Aerial Dragnet program is seeking to deal with the unmanned aerial vehicle threat using a series of sensors.

“It’s not really focused on countering these threats; it’s really focused on the first part, which is detection and discrimination between unmanned platforms” within the clutter of everyday urban life, Waterston said.

The main impediment is that in a big city, the terrain is almost all non-line-of-sight. That means multi-modal solutions – radar, optical, or acoustic – he said. With high-rise buildings, the aircraft can approach from above as well.

“We cannot start shining a multi-kilowatt laser with a building in the background,” Ledé said. “We have to have counter-UAS systems that will not have hazards for civilian populations.”

“Sensors can hear the UAS rotors or a radar could bounce off a building to pick them up. You can tell someone is using their weedwacker even though you don’t see their weedwacker,” Waterston said, to give a sense of the kind of detection he envisions emerging from the Aerial Dragnet program. The catch is that the program seeks technologies that are relatively inexpensive.

 

Defending Mobile Forces Against Hostile Drones

Even once hostile drones are detected, defeating them in an urban environment is tricky. Ledé is managing the Mobile Force Protection (MFP) program, which seeks to defend high-value convoys against rogue drones.

Today’s counter-UAS systems mostly rely on jamming or taking over the UAS’ data links. The program will track, ID, and engage the small UAS of the future, which may not rely on radio-frequency signals for command and control.

The proximity to civilians and innocent bystanders makes the problem particularly difficult in cities. “We cannot start shining a multi-kilowatt laser with a building in the background,” Ledé said. “We have to have counter-UAS systems that will not have hazards for civilian populations.”

“Kinder, gentler solutions include nets that entangle the aircraft, or obscuring optics to blind them,” Ledé said.

The already-completed first phase of the MFP program sought to stop unmanned aerial vehicles in a relatively open space outside a forward operating base. In the upcoming Phase 2, the program will try, in an urban scenario, to deny the operation of unmanned aerial systems that are no longer using radio frequency signals to communicate. Phase 3 will up the anti-UAS challenge by tasking performers in the program to handle scenarios with multiple drones attacking a friendly convoy on the move.

 

Beneath the Streets – The SubT Challenge

While cities are growing taller, and ground forces must look to the skies for threats such as rogue drones, there is a whole additional layer to the urban environment below.

“As much as the cities are building upwards, I think they are going to build downwards as well,” said Chung. “The subterranean environments pose an increasingly more threatening environment for our warfighters.” That could include clandestine tunnels or city infrastructure such as sewers or subway lines, he said.

Chung is managing the DARPA Subterranean (SubT) Challenge, which will distribute prize money to teams that can demonstrate that they can map, navigate, and search underground structures. They will have to find objects quickly, check air for breathability, and determine the navigability of the tunnels, he said.

Phase 1 tasks technology developers with demonstrating the ability to map illegal tunnels. Such tunnels have been found under borders for smuggling, and have also been used in war going back centuries. The Viet Cong famously used such tunnels in the Vietnam War, with some being built under Army bases. Phase 2 of the SubT Challenge will include the mass-transit tunnels, sewage systems, and other underground structures found in urban settings. Phase 3 of the competition will be the most challenging. Contestants will survey naturally occurring caves – replete with their complex irregularities – rather than the structures found in cities.

The SubT Challenge will ask teams to map all three together. Similar to the OFFSET program, contestants can write software and try their ideas on a synthetic course rather than a physical course. The winner of the synthetic course will receive $750,000 and the winner of the physical course will receive $1 million, Chung said.

Over centuries of warfare, urban combat has traditionally been among the bloodiest and most dangerous of operational scenarios. Today, DARPA research is finding ways to trade technology for blood, providing eyes, ears, and allies for troops fighting the battles of tomorrow in an increasingly perilous urban battlespace.