Destroying to Protect
UTSA professors use virtual explosives to keep cities and soldiers safe
Keith Clutter loves to blow things up.
So far he’s unleashed 17 truck bombs in various locations around San Antonio and set off dozens of explosive devices close to U.S. troops.
An associate professor in the UTSA Department of Mechanical Engineering, Clutter has a Ph.D. in aerospace engineering and is an expert in blast dynamics, the modeling of combustion and explosive shock waves. He’s also a major in the Air Force Reserve and an Iraq veteran. He’s seen the effects of terrorism firsthand. That’s why he’s trying to simulate it.
Fortunately, Clutter’s explosions happen only on a computer. By attacking buildings in a virtual world, Clutter hopes to identify San Antonio’s most at-risk locations so they can be reinforced in the real world. And by studying the often unseen physical effects of up-close explosions on soldiers, he plans to give military medical personnel a better way to prioritize and treat injuries resulting from blasts.
The City
Terrorists choose their targets based on vulnerability and consequence. They select locations that are easy to reach and whose destruction will produce the greatest overall consequence, whether financial, tactical or in loss of life. Clutter chooses his targets the same way, and uses bombs that are a little more than twice the size of the one used on the Alfred P. Murrah Federal Building in Oklahoma City in 1995.
“Sometimes when I tell people about what I’m doing, they say we shouldn’t even be talking about it, that we’ll give terrorists ideas,” Clutter says. “I tell them, ‘The bad guys are certainly talking about it.’ We need to beat them to the punch to determine our softest spots and defend them.”
Clutter identifies targets based on the assessed value of the buildings themselves. He recognizes that some high-value targets, such as a city’s Emergency Operations Center or a unique medical facility, may be located in low-value buildings. But since the assessed value of most buildings is readily available on the Internet, it’s a likely way for terrorists to choose their targets. The overall concept of determining the targets’ value versus vulnerability is still sound, even if the definition of “value” varies.
Using a cross-section of downtown San Antonio containing 280 infrastructures of varying height, size and orientation and collectively valued at $1 billion, Clutter has simulated the damage a 10,000-pound truck bomb would do at 17 different locations. This geometric representation of the city is used along with computational fluid dynamic technology to pinpoint locations where the combination of property value and blast profiles maximize the damage such a bomb would produce.
Every scenario is unique, since various building materials, such as concrete and glass, respond to explosive pressures differently. Surrounding buildings’ proximity to one another, changing terrain and the size and number of vehicles in the vicinity can also reflect blasts in different directions, causing varying results.
Clutter’s simulations have resulted in a range of damages, from shattered windows to leveled buildings. The projected financial impact has ranged from $2.7 million in one scenario to $126 million in another.
“There are experts who’ll tell you they can predict exactly where terrorists are going to strike,” Clutter says. “If that were true, we’d all be waiting there for them with our guns drawn. My opinion is you focus on understanding your consequences and trying to minimize them.”
Clutter explains that every large city interacts with the Department of Homeland Security (DHS) to get funding. “If the City of San Antonio can go to the DHS with this kind of rock-solid data—pinpointing exactly where it needs to maybe create a pedestrian-only thruway or put up security cameras to monitor a parking garage—it has a much better chance of receiving the kind of support it needs.”
Emergency response planning is another application for Clutter’s research. By modeling the effects of blasts in various parts of the city, he’s able to predict the probable locations and types of injuries as well.
Explosions create upside-down triages, with the more serious injuries being found later in the rescue process as responders work their way toward the center of the blast zone. Clutter says the data he’s collecting will help emergency personnel find the most seriously injured more quickly by predicting where blast forces will be the highest.
“There’s a lot of data going all the way back to World War II that correlates building damage to occupant injuries,” says Clutter. “We can determine the building occupancy and compare that to the level of damage to estimate how many and what kind of injuries there are going to be.”
The Soldiers
During his tour of duty in Iraq, Clutter served on an Explosive Ordnance Disposal team. These teams, dealing with roadside explosive devices, can be exposed to blasts that may do unseen damage.
While some wounds are easy to see, others, like head injuries and especially concussions, can be less obvious. Clutter wants to make those unseen injuries as recognizable as any other.
An explosion is recorded as a pressure time history—a time-based schematic of the position and force of a pressure wave as it expands outward after an explosion. As the blast sweeps over a soldier, the difference in the pressure load will cause the head to move. Since the brain moves independently of the skull, this can result in it slamming against the front of the skull, much like whiplash.
Again using computational fluid dynamic technology and explosion modeling, Clutter can measure the forces a soldier is exposed to. Working with fellow UTSA engineer Tom Connolly, Clutter is developing a sensor that can be built into soldiers’ helmets capable of recording blast data in real time. That data is then correlated to Clutter’s models to project the type of injuries it’s likely to cause.While Clutter is involved in computational fluid dynamics, which model the bomb explosions, Connolly is involved with dynamic systems modeling, which measures impact on the brain.
“I build a model of the brain and skull to measure what that pressure wave does to a human head,” Connolly says. That’s important because medics often don’t know that a person has received a brain injury until symptoms begin.
“If you ask the soldier, he’s going to tell you he’s fine and ready to go,” Clutter says. “He may have an injury where the brain begins to swell. If the doctors know that, they’ll actually cut out a piece of his skull, give the brain a chance to swell and then go down again and then repair the skull. The problem is they don’t know if your brain is going to swell or not, and there’s no outward indication that it’s going to happen.”
The sensor they are developing will serve as that outward indication. By recording the intensity of the pressure wave, the sensor can provide a history of the force to which the soldier has been exposed.
“The troop doesn’t even have to be conscious,” Clutter explains. “The medic can plug the sensor in the soldier’s helmet right into a handheld computer and get an instant readout of what it’s been exposed to. He can then make an informed decision about whether that soldier’s brain is likely to have been injured. Then there are lots of ways that [it] can be treated.”
Clutter’s devastated model of San Antonio has been presented to city officials. He has a working prototype of his helmet sensor and is seeking additional funding to develop more sophisticated models of the device.
Until that happens, Clutter will continue working in his virtual world, gradually making the real world safer by doing what he loves—blowing things up.
— Randy Lankford
Illustration by Michael Morgenstern c/o theispot.com