Receive emails about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens. Email Address Zip Code Subscribe Scott Hubbard was well-suited for the CAIB, having overseen complex space programs. He was also responsible for putting NASA's Mars program back on track following the costly mission failures of 1999. Support Provided By Learn More © WGBH Educational Foundation

A shocking loss

NOVA: Do you remember how you first heard about the accident?

Scott Hubbard: I remember very clearly. It was about 6:30 in the morning West Coast time, and I wasn't up yet. But the radio was on and my wife said, "Listen to this." She turned the volume up just as the announcer said, "The shuttle is overdue." Now, there is no such thing as an overdue shuttle. Once you commit to reentry, you are going into Earth's atmosphere. So I quickly pulled on some clothes, grabbed my cell phone, and ran upstairs. I turned the television to CNN and began to see what the rest of the country saw—that terrible sight of the shuttle breaking up over Texas.

When did you join the investigation team?

Well, within about a half hour, my cell phone went off, and it was NASA's deputy administrator. He said, "We are putting an accident board together. There's a place for a single individual from NASA—a senior person—and the administrator would like you to be that person. Will you do that?"

So that very first afternoon the board was pulled together with its initial eight members. [It eventually grew to 13.] And they asked us to go to Lackland Air Force Base, where they were doing search and recovery.

So you went to Texas. What happened in those early days?

The first month was largely devoted to recovery of the debris. We had 20,000 volunteers searching for remains of the shuttle as well as the astronauts' remains. It was a very emotional time. I remember when they brought in some of the first remains of the crew. It was a very solemn ceremony—bringing the casket out and carrying it through the crowd. The military people were all standing at attention. That got to you, you know. You really felt a sense of loss.

Jonathan Clark, widower of astronaut Laurel Clark, stands beside her casket with their son, Iain Clark, 8, during a service at Arlington National Cemetery on March 10, 2003. © J. Scott Applewhite/A.P. images

Sifting the evidence

Did you participate in the search?

The board's job was not to collect debris, but we did go out and walk up and down the areas being searched. We were shown how some pieces were found, because one important question was: How are you doing this search? It's like in a trial: How are things being bagged up, do you use a GPS to note exactly where you found it, and so forth. The board had to decide if the debris was telling a story or not.

Did it? Did the debris give you a sense of what had happened?

Oh, absolutely. The debris spoke to us; it told us a story. When the flight recorder was found, that was a huge piece of data, but the debris itself also held clues.

What pieces of debris spoke to you the most?

Probably the pieces of the reinforced carbon from the wings—both the pieces the search teams found and the ones they couldn't find. They recovered much more of the right wing than of the left, for example, which meant the left wing most likely disintegrated first. Also, the debris from that left wing had very sharp edges, which meant that it had been exposed to very high temperatures for an extended period of time. These clues, combined with data from the flight recorder and the later foam test, gave us a sense of what had happened.

The debris showered down on a vast area spreading from east Texas to southwestern Arkansas. At the Kennedy Space Center, the recovery team laid the debris out within an outline of the shuttle. Courtesy CAIB/photo by Rick Stiles 2003

Early in the investigation, you suspected that a piece of foam hitting the wing during launch had caused the accident. Why did you suspect the foam early on?

Well, one of the first things the board did was look at videotape [of the launch] showing one side of the shuttle and a 35 mm film showing the other side. Neither view was perfect. But you could see the foam coming down and then this shower of stuff coming out the other side. You never saw the actual impact.

"I was not going to conceal anything, and I was going to do what I thought was right to figure out what happened."

The nation's very best experts, people who work in the spy satellite business and the movie business, cleaned up the images. There was a group at Johnson Space Center that did photo enhancement, and I went over there many times. Early on, it just seemed so clear that this was a big piece of foam that had hit in a spot on the left wing.

Hubbard suspected early in the investigation that a briefcase-sized chunk of insulating foam, such as these samples, had caused fatal damage to the shuttle's left wing. Courtesy CAIB/photo by Rick Stiles 2003

Yet people in the shuttle program said the foam was too light to cause significant damage—that it would just bounce off the wing.

It was not just bouncing; it hit it. Shortly after Doug Osheroff joined the investigation team, I said, "Doug, you won a Nobel Prize in physics. Let's just do some high school arithmetic here, okay?" They knew on the second day of the mission that a piece of foam hit the wing leading edge and that it was the size of a small briefcase and probably weighed two pounds. They knew this. So I said, "Let's do some simple high school physics. Check my numbers." And Doug said, "Yup. If the foam hit at a relative velocity of 500 miles an hour, it would impart a force of about 3,000 pounds—roughly a ton of force."

Yet we had people in the shuttle program saying, "Oh, these guys are 'foamologists'!" They would hold a piece of foam up on national TV and ask, "How could anything this light do any damage?"

The problem is that human beings don't have a sense of what 500 miles an hour is really like. When you are driving along and you stick your arm out the window, you can feel what 40, 50, 60 miles an hour is like. But 500 miles an hour is hard to imagine. That was the mistake of professional engineers and scientists in the shuttle program. And they somehow didn't do the simple calculation to understand the foam's impact. [For more on the calculation, see Force of Impact.]

A flawed model

What about the analysis of the foam impact that was done during the first week of the mission? Why didn't the shuttle engineers see that it posed a real threat?

They used a model built for a completely different purpose to try to evaluate this foam strike, and it didn't work. This is the famous "crater model."

The board asked the engineers who did the analysis a series of questions. The engineers said, "Well, we used the database and so and so." And I said, "Yeah, but that database is for little pieces, not for something the size of a briefcase." And they said, "Well, you know, hey! We're just using what the guys from Huntington Beach gave us—this is a Boeing thing. Boeing gave us the program, and they told us how to use it, and we're using it. And we think it's okay."

So that caused the board to realize two things: One is that critical information and critical processes had been handed off with minimal training [from Boeing, the contractor that built the shuttle, to NASA]. And secondly, that we needed to take a closer look at this model. We had a number of independent tests to evaluate the model, and the conclusion was universal.

Even before the Columbia accident, foam fragments had broken loose from the external fuel tank during several shuttle launches. As the disaster tragically brought home, managers within the shuttle program underestimated the risk of damage from such loose foam. Courtesy CAIB/photo by Rick Stiles 2003

What did they find?

It didn't take very long—maybe a day or two of looking at the details—to figure out that the crater model didn't apply in this case. However, it kept showing up. Every time we had an evaluation of the physical cause of the accident, somebody would say, "But the crater model says...." And I found myself continually repeating, "But the crater model is irrelevant!"

This model is, first of all, not based on physics. It's more like just a list of numbers—say, if you get a 25 you go over here, and this is a 6 and that tells you something. They put numbers in and got numbers out.

That's all they did? They didn't calculate anything?

That's all they did. Here's what happened [during the mission]: The photography people said, "Our best guess is that the piece of foam was about so big." They gave that estimate to the people using the so-called crater model. The people using the crater model just plugged it in and got a number out. And the number said, "You're gonna dig a divot that's less deep than the thickness of the tile."

They should have realized that something was wrong, but they didn't. Every computer coder in the world has a famous rule of thumb: "Garbage in, garbage out." Okay? And they put assumptions and numbers in there that had no connection with the kind of computer code it was.

Did you ever talk to the guy who originally wrote this code?

I did. I talked to the guy who had written the original program 20 or more years before, and he explained to me where it was valid and where it wasn't, and that it wasn't written for reinforced carbon [the material of the wing presumably damaged by the foam], and that it was written primarily for small, bullet-like projectiles, not a big piece of foam.

Was the crater model used routinely even before the Columbia accident?

Yeah! It was used all the time. The crater model incident, I think, was typical of the shuttle program. The fact that they were willing to use something completely inappropriate for evaluating this accident says that somewhere people were not really thinking very critically.

Hubbard's team conducted the definitive tests of the foam strike at the Southwest Research Institute in San Antonio, Texas. Here, he briefs the media. Courtesy CAIB/photo by Rick Stiles 2003

A definitive test

You set out to recreate the foam strike with your own test. I understand you faced some resistance to getting the parts you needed.

When we were planning these tests, I had a major, wild disagreement with some people within the shuttle program who were telling me they didn't see any reason to do a full-up test, that it could be just simulated and so forth. They really didn't want to give up those pieces of flight hardware to do the test. And I said, "That doesn't make good engineering or physics sense. There's no way that we can reproduce this without having the actual pieces."

Do you think, somehow, they saw you as betraying your own "NASA family?"

No. I got the sense that they understood that I was representing the Columbia board, that I was not going to conceal anything, and I was going to do what I thought was right to figure out what happened.

You eventually got what you needed. Tell me about the final test, which was widely televised.

Yes, and a number of the engineers working with me said, "Are you sure you want to have these TV guys in here?" But if you try to do something like this behind closed doors, there will be people who will say, "conspiracy, cover-up, how do we know?"

I went up in front of the press—a room full of 60, 80 people. I explained to them, "We've got it organized with the actual flight hardware. We've got the gun lined up to reproduce what happened. So as far as I know, this is going to be the definitive experiment." And I remember walking out of the room thinking, "I hope we did everything right, because there are a lot of people watching us."

"There was no hiding from this. There was no spin doctor here. It was done in front of live television."

Were the astronauts' families there? Did you feel that this test was also for them?

Yes. There were people from the astronaut corps, people representing the families. You know, we had a picture of the crew in every single room at the Columbia board, and we would always remind ourselves, "We're here, in part of course, because of these people who died and what we owe to them and their families to figure out what happened."

In the test, an airgun would fire a foam projectile toward a replica of the wing. Months of work and painstaking research led to this moment. © WGBH Educational Foundation and The Factory All Rights Reserved

How did you feel during the test itself?

It was a very powerful, emotional moment. We had done all this work for months to get everything ready. There were all these people. It was very hot—down there in San Antonio it's a hundred degrees everyday. And the place is full of snakes and stuff—it's all outdoors.

I was standing with all these other officials, and two astronauts came up to stand right behind me. There was a countdown to the firing of the gun, and the gun went "Boom!" And all of a sudden there was this giant hole in the wing leading edge. At first I went "Yes!" and then I went "Oh." Because part of me said, "Okay, you've demonstrated it," but then part of me said, "Oh, this is how these people actually died." I felt these two completely conflicting emotions at the same time. And the astronauts were glued to either side of me, and they said, "So this is what happened." And I said, "Yeah, this is what happened."

So we walked up there. I looked at the mark closely. There was one engineer, a middle-aged woman who had worked with us very closely who came from Johnson Space Center, and she actually had tears in her eyes, because she, you know, didn't want to believe that the foam had done it. But this was so dramatic a test—it showed that there was just no doubt.

Do you think that the people assembled—the astronaut corps, the shuttle engineers and officials—were grateful to have a definitive answer?

The astronaut corps was universally supportive. They said, "We're glad you did this. Now we know for sure, now we can get on with it." I think most of the engineers were supportive and would say, "Okay, now we've got the data, we can move on, we can start to figure out how to prevent such an accident in the future."

I did sense, though, among some people in the management ranks that they might have been happier if there had been some room left for ambiguity. I don't know if this went on for very long. It's a human reaction, I think. It was difficult for them to have this demonstrated in such a public way. There was no hiding from this. There was no spin doctor here—nobody could come from inside the beltway and put a spin on this. It was done in front of live television, and there it was. You know, it's like the stages of coming to terms with somebody's death, and there were people there who simply didn't want to believe that something they worked on could have resulted in a tragedy.

The crew of Columbia STS-107 (from left to right): Mission Specialist David Brown, Mission Commander Rick Husband, Mission Specialist Laurel Blair Salton Clark, Mission Specialist Kalpana Chawla, Payload Commander Michael Anderson, Mission Pilot William McCool, and Payload Specialist Ilan Ramon Courtesy NASA

Lessons learned

What did you learn, personally, from being involved in the investigation?

I learned a great deal about what it means to manage very complex, very high-risk projects and missions. I had been involved in such projects before—the Mars program, the Lunar Prospector Mission—but I got an even deeper understanding of how you can take nothing for granted. Over time, big organizations can fall into bad habits. And unless people insist on being absolutely rigorous, bad engineering can begin to take over. Day after day, you have to question assumptions; you have to ask yourself whether you have covered all the bases. And I definitely got much more aware of what it means to act with safety in mind. That's Job One.

Do you think that NASA has learned this lesson in considering the future of human spaceflight?

Well, where is NASA headed today? As the board was getting ready to write the final report, I remember distinctly making the comment—and I wasn't alone—that if you're going to risk peoples' lives that it ought to be for a purpose. I remember saying, "If we can push NASA in the direction of defining a purpose for human space exploration, then these people would not have died in vain—they would have been part of a new vision for the future." And it's my belief that part of our report led directly to NASA's new vision for space exploration.