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How to watch a declassified nuclear test film like a weapons physicist

How to watch a declassified nuclear test film like a weapons physicist


‘We're working our little rear ends off trying to perfect a product that none of us ever want to use.’

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Greg Spriggs likes to joke that if he were a better golfer, he would never have become a nuclear weapons physicist. But it’s a good thing he’s not professionally smacking golf balls right now, because Spriggs has an important mission. He’s working with film preservation expert Jim Moye to save decades-old films of nuclear blasts that are among the last, best sources of real-world information about nuclear explosions.

The best way to test what happens when a nuclear weapon explodes is to just blow it up. So from 1945 to 1963, the US exploded 210 nuclear devices in the air. Scientists captured the massive fireballs and mushroom clouds on camera — preserving the data in at least 10,000 films. The films were then analyzed to determine key details like the energy unleashed by the blast, or its yield.

Those measurements, however, were done without the assistance of computers — and Spriggs discovered that some of that data wasn’t quite right. He works for Lawrence Livermore National Laboratory, where he and other scientists write computer codes to predict how modern nukes will perform and the damage they will cause. The US no longer explodes nuclear devices in order to test them, so scientists run their models against the historical data to see if predictions match reality.

Jim Moye (left), a film preservation expert, and nuclear weapons physicist Greg Spriggs (right) are working together to save thousands of nuclear test films.
Jim Moye (left), a film preservation expert, and nuclear weapons physicist Greg Spriggs (right) are working together to save thousands of nuclear test films.
Photograph: Lawrence Livermore National Labs

A few years ago, Spriggs had been trying to model nuclear fallout, but his computer codes wouldn’t match that historical data. So he went back to the source — the old films. Using a computer program to take more accurate measurements, he found that there were a few mistakes — like the height of the cloud rising to the sky after the blast, which hadn’t been measured accurately enough in the 1950s. “That's why my code never worked, because I had the wrong cloud height,” he says. “Once I got the cloud height right, everything fell into place.”

But then he noticed that the yield measurements were off, too. And that’s a problem, because the destruction a bomb causes and the radioactivity it produces are both connected to its yield. So he decided to find all 10,000 of those films to reanalyze them from scratch. Lawrence Livermore National Laboratory recently published 60 of the declassified nuclear test films on YouTube, where anyone can watch them. But there are many more to digitize and save, and the team is working as fast as it can.

After 60 years in storage, the films are quickly disintegrating. With the help of nuclear historians Alan Carr at Los Alamos National Laboratory and Pete Kuran, Spriggs and Moye have scanned 4,200 of the 6,500 films they’ve recovered, and analyzed between 400 and 500 of them.

The Verge sat down with Spriggs and Moye in their windowless lab to learn how to watch these films like an expert. In the video above, you can see Spriggs analyze a fireball and mushroom cloud produced during Operation Teapot in 1955. We talked about nukes, films, and the new details they’re learning from nuclear devices detonated more than half a century ago.

This interview has been edited and condensed for clarity.

So how did you start this project?

“If the data is wrong then we need to grab a whole lot of these films and reanalyze them.”

Greg Spriggs: By accident. My boss had me write this computer code trying to calculate nuclear fallout, and I couldn't get the data to agree. And I kept saying, I'm not doing anything wrong with my code, so there must be something wrong with the data! What I need to do is look at some old films and reanalyze the data before I start tearing myself down. Sure enough, we had about 12 of these films over in our archives, and I had them scanned. And whenever I analyzed them, we had a big enough difference that my boss said well, if the data is wrong then we need to grab a whole lot of these films and reanalyze them, and get the right data. So I was a one-man show, I was the scanner and the analyzer. I would work 12 to 14 hours a day — I would sometimes take a nap in the middle of the day. I had a pillow and would curl up under my desk. And work strange hours.

How long has it taken you?

GS: We've been going at it for almost five years. I realized that scanning [the films] was a full-time job, analyzing was a full-time job, and I just told my boss, “I can't do this. My wife is going to divorce me because I never see her.” And so [we hired] Jim [Moye]. And then we hired Pete Kuran — he's more of a historian and he taught me about the data sheets [that described the camera’s technical specs and its distance from the blast]. And Jim did all the scanning and film repair. We had a critical mass, and off we went!

What are you measuring in the films?

GS: You can't really see the fallout, per se. You can see a cloud, and that's potential fallout. But you had to know what the cloud heights were in order to predict [fallout]. So that's what we were trying to measure — an accurate cloud height.

In order to figure out the yield, there's an equation that relates the size of the shockwave at a particular point in time to how much energy was dumped into the atmosphere, i.e., the yield. So if we measure the shockwave position as a function of time, then we can figure out what the yield of the device is. 

Why was  the original data wrong?

GS: It was primarily because they had to do it manually [back in the 1950s]. They had to put the [video] frame in this enlarger, project it onto a grid, center it as best as [they] could, and then read what the radius was. And by looking at the film that way, it's very difficult to get an accurate measurement.

Jim Moye: It's like trying to build a house without a level.

GS: They were rushing to get it done, and move to the next one. The thing went off and went bang, everybody was happy — let's test the next one! And that's what happened. So they didn't really have the time to concentrate on the details that you needed to do it right, to get it really accurate. We're just fine-tuning the data.

Why is it important to fine-tune that data?

GS: We don't test [nuclear devices] anymore, and we have to convince our bosses at the [Department of Energy] that our [computer] codes are giving them the right answer. So if you validate your code against crappy data, the validation doesn't mean anything. If you validate it against good data, and you say it matches, well then they believe you. So the point is, we need really good data so we can go back and say we've got a 99 percent confidence that this thing, when it goes off, is going to give you a yield of 20 kilotons. And they say great, prove it to us. Well, here's the validation data we've got. So that's why.

Greg Spriggs analyzing an atmospheric nuclear test.
Greg Spriggs at work analyzing an atmospheric nuclear test film.
Photograph: Lawrence Livermore National Laboratory

How did you get permission to declassify these films?

GS: Back in the 1950s, these films were all born classified. And the reason was the yields were never announced. And then the DOE — which used to be the AEC, Atomic Energy Commission — decided that the public needed to know the yields, so they started to announce [them]. At which point, those films became declassifiable, but no one would declassify them because it took a lot of effort. So somewhere along 1960, 1970 — in that time frame — someone declassified about half, maybe one-third of them. And they left the rest classified. We had to declassify the films so Jim could handle them.

Greg, I hear you're one of the few people who's seen an atmospheric test in person?

“The sky lit up like it was noon.”

GS: My dad was in the Navy and he was stationed on Midway Island. I was about 11 years old and they were doing some high-altitude detonations up in outer space, in the Pacific, over Johnson Island. Johnson Island is about 400 miles south of Midway. They told us, “This is where it's going to be, look in this direction and you'll see it.” Didn't matter what direction you were looking. When it went off it was 10 o'clock at night and the sky lit up like it was noon and then it started getting progressively darker and darker, and it went through all these different colors, kind of like the Northern Lights, and it lasted for about 15 minutes before it went back to being pitch black again. It was called Starfish Prime, 1.4 megatons. It was up 237 miles. And we have a film of it. As a kid, I was too dumb to even appreciate.

Did seeing that test make you decide to do the work that you do?

GS: Until I was 22 I would have bet anybody a million dollars that I was going to be a professional golfer. And then at 22, the golf coach at the University of Arizona said, “What are you studying otherwise?” I said nuclear engineering, and he said: "You gotta stick with it."

JM: Good thing you had a backup.

GS: I had no clue I was going to be a weapons designer. None whatsoever.

So what made you want to major in nuclear engineering in the first place?

GS: I opened up the [course] catalog and the “N” was in the middle and it [said] “Nuclear Engineer.” And I said, “Well, that sounds okay.” I didn't care, because I was going to play golf.

JM: He's a good golfer.

GS: But not good enough! That was the problem.

You worked at Los Alamos National Laboratory before you came to Lawrence Livermore. What did you do at Los Alamos?

GS: Just about everything. The last 10 years I worked there, I worked as a primary designer — designing primaries for nuclear weapons. That's the uranium or the plutonium pit that initiates the nuclear weapon.

How does that compare to what you’re doing now?

GS: To me, it was kind of like chipping paint. You run computer codes day in and day out, that's all you do. Sitting in front of a computer reading fireballs and seeing this kind of stuff is a lot more exciting. Every time I see a new film, I see something new and get to try out things — it's experimental data.

JM: It's old but it's new — hasn't been seen in a long time.

GS: And there are things they simply didn't have time to study back in those days, in the ‘50s — we're picking out things that nobody's ever seen before. New correlations, new ways of figuring out the yield, all kinds of funny little things.

What do you guys wish that people knew about our nuclear weapons program?

“It’s kind of an irony, isn’t it? That we have a product that we hope nobody ever uses.”

GS: One of the ironies of this lab is that we have all these smart people, and we're working our little rear ends off trying to perfect a product that none of us ever want to use. We don't want to use a nuclear weapon. But we've got to have it, so that if we ever get attacked, and the president decides to retaliate with nuclear weapons, it's got to work. We've got a lot of peoples' lives at stake here. It’s kind of an irony, isn’t it? That we have a product that we hope nobody ever uses.