JEFFREY BROWN: Now: how investigators are breaking down the inner workings of a bomb. That particular kind of forensic work often happens out of the spotlight, but the Boston bombings and the device that was used brought it back to public attention.
NewsHour science correspondent Miles O'Brien reports.
MILES O'BRIEN: We all watched the chaos of the Boston Marathon bombings with horror, but in Socorro, N.M., the raw emotion was mixed with scientific insight.
VAN ROMERO, New Mexico Institute of Mining and Technology: It's really almost schizophrenic, I think, from my standpoint is, part of my brain is going into analysis mode, what -- that white smoke, what does that mean? I started looking for broken windows. Where is the pattern of broken windows from the video that I saw?
Because that tells me where the pressure wave went and how big the pressure wave was. Is there a crater? So, all that analytical stuff is going through your brain.
MILES O'BRIEN: Van Romero is the vice president of research at the New Mexico Institute of Mining and Technology, which operates the Energetic Materials Research and Testing Center, the most active explosives testing facility in the U.S.
Name a terror bombing, Marine barracks in Beirut, Khobar Towers, Oklahoma City, the first attack on the World Trade Center, the London transit bombings. In each case, investigators have come here to test their notions of what happened to build a court case and find new ways to defend against future attacks.
VAN ROMERO: You look at the scene of a terrorist bomb, it's just a mess. People have to go in and collect some very important and some very minute evidence that they make a big case out of.
And so making sure that that evidence is accurate to the scenario that we assumed happened, that's the important role that we play, is, how do we put the pieces of the puzzle together so that we know they fit?
MILES O'BRIEN: Every workday, at least two or three explosions echo across 40 square miles of barren desert canyons here. It began as and remains a favorite place for weapons-makers to measure the menace of their missiles and ordnance.
We wanted to know more about what makes a pressure cooker bomb like those used in Boston tick. So, we hired these white hat bombers to show us how it's done. Fear not. We will not show you anything here about the device that isn't readily available on the Internet.
VAN ROMERO: These are the basic ingredients for a pressure cooker device. It's just a pressure cooker that you would have in your home, and the way the pressure cooker works is that it creates a seal, if we can get it to come together here.
It creates a seal. The pressure will build up on your stove. And this releases -- there is a vent here that releases all that pressure so it doesn't build up too much pressure in your kitchen. If we put energetic materials in here that create a lot of heat and a lot of gas very quickly, the pressure will build up so fast that the cooker can't contain it, and it will burst open, it will explode, throwing shrapnel all over into the environment.
MILES O'BRIEN: The Boston bombers used nails and BBs. Here, they use nuts, because they are less hazardous and just as useful for an experiment.
VAN ROMERO: These fragments will be going 1,000, 2,000 feet a second, so their shape really doesn't matter. Anything going that fast is going to penetrate into just about anything it hits.
MILES O'BRIEN: Lighting gunpowder in this dish on a lab bench is not a problem, but tightly packed in a sealed container, it is another matter.
They didn't show us how to trigger the bomb, and even if they did, we wouldn't share those kind of details. Suffice to say a simple how-to is not hard to find for someone who is determined. But could an untrained amateur stage such an attack without any hands-on training?
VAN ROMERO: The fact that they were two for two kind of indicates to me that it was a little bit more than luck. And the fact that they were so close together -- 10 seconds, 10 to 15 seconds away is essentially simultaneous.
And if you think about it, two different people planning two different bombs that went off at almost exactly the same time, to me, it indicates some level of sophistication.
MILES O'BRIEN: Pressure cooker bombs are new to the U.S., but are a familiar instrument of terror globally. In 2006, Islamic terrorists set off seven of them in 11 minutes on crowded commuter trains in Mumbai, India, killing more than 200, injuring 700 others.
When our bomb was ready, the warning siren sounded and we retreated to a bunker high above the site, 2,000 feet away.
MAN: Five, four, three, two, one.
MILES O'BRIEN: When the smoke cleared and the site was declared safe, we went back for a look.
VAN ROMERO: OK. So, as we walk up, one of the things we will notice is, here's some of the nuts that they were -- be careful. They may be warm. This one has cooled down. Here's the lid from the pressure cooker.
And -- but this is going to be a really important piece of forensic evidence, because this obviously was something that wouldn't be in the environment in a street city. Right? So, you find this, and you go, OK, this was part of the device.
And now that I know that part of the device, I can analyze this metal and figure out what the brand, the model, the make of the pressure cooker, where the metal was forged, where this thing was manufactured. And then, as I collect other fragments, I want to make sure that they match the origin of this piece here.
MILES O'BRIEN: Stinks -- sulfur smell.
MAN: Yes, from the -- yes.
MILES O'BRIEN: In Boston, investigators found one pressure cooker lid on roof of a six-story building nearby. They walked shoulder to shoulder, picking up every fragment they could find. And so it went here as well.
MIKE STANLEY, New Mexico Institute of Mining and Technology: And I will dump some of these out, so that we can take a look.
MILES O'BRIEN: But these -- these would be traveling. And these are things that would hurt you. These would be traveling how fast?
MAN: Those could be going up to 1,500 feet per second.
MILES O'BRIEN: In the lab, engineer and associate director Mike Stanley sifted through the fragments.
MIKE STANLEY: Even though you have a detonation, all of the pieces are still there; they have just been separated. So, with enough time and enough diligence, you could actually probably put the entire pressure cooker back together.
VAN ROMERO: OK. Mike, let's go ahead and run the high-speed video.
MILES O'BRIEN: Explosions here at New Mexico Tech are all captured with high-definition high-speed cameras at 6,200 frames a second, allowing the experts to see how a bomb explodes in super-slow motion and minute detail.
VAN ROMERO: One of the fragments, which appears to be part of the sidewall of the pressure cooker -- and let's run it just a little bit. As you will see, there's -- this seems to be the bottom. So if that is the bottom of the pressure cooker, we found that 100 yards away.
MAN: One hundred yards.
VAN ROMERO: Right, yes. And that's one that we measured the velocity. What did you say?
MAN: Two hundred and seventy meters per second.
VAN ROMERO: Two hundred and seventy meters per second, OK.
You never stop really trying to understand what's going at the scene. Just because you identify one molecule or piece of a certain type of device doesn't mean that there wasn't other things that occurred at the same time. And you have to make sure you have peeled back all the skin of the onion to understand what's going on.
MILES O'BRIEN: The plywood got completely blown out, huh?
Authorities probing the Boston bombings have already reached out to these experts. Chances are they will once again be asked to help solve a troubling puzzle.
JEFFREY BROWN: In his next report, Miles examines the facial recognition software that allowed investigators to match high-resolution images to the faces of the Boston bombers.
And he continues his reporting on tonight's edition of NOVA, examining the role modern technology played in allowing detectives to unravel millions of clues. It's part of NOVA's night of special reports, which also includes a look at Oklahoma's deadly tornadoes. NOVA airs tonight on most PBS stations, and you can find a link to their website on ours.