Q: So, it was just this misguided notion that there’s a ton of space in space?
Kessler: Yes. And, you know, that’s sort of the nature of all environmental issues. You start off thinking you got plenty of room, you don’t need to worry because the oceans are endless, the air is endless, it couldn’t possibly end. It just—and after a while, you run out of space.
Q: When you sat down to write your paper—which I attempted to read, I understood parts of it—what was your initial goal?
Kessler: It was to draw attention to the fact that if we didn’t do something different, we would create an environment that was self-perpetuating and that we needed to change the way that we operated in space.
Q: And the way you described it was you wanted people to understand the possible consequences of “continued unrestrained launch activities.” What did you mean? Just that we just keep going as we’re going, and we don’t do anything preventative?
Kessler: Right, exactly. And, of course, when they did the Space Junk movie, I remember the narrator was surprised to learn they just turn things off, leave them in space. And, of course, the only thing that will bring an object down is in the lowest parts of low Earth orbit. Below about five hundred kilometers, you’ll reenter within twenty-five years. But if you’re above that, say, between five hundred and one thousand kilometers, it can be centuries before things reenter. And if you’re above one thousand kilometers, it can be billions of years before things come down because there’s no—there’s insufficient atmosphere at those altitudes. So, it would continue to accumulate. There’s no question about that.
But it gets to the point in low Earth orbit—where most of the material is—it’s a question of how fast this debris is being generated verses how quickly it’s being emptied by the natural atmosphere. There’s a term I started using, the critical density, at what point do you reach that where you’re going over this critical density so that things, even if you don’t put anything else up there, the collisional process will generate debris faster than it can be removed? And my calculations and most of the calculations from the rest of the world, except for France, have come to the conclusion that we’ve already exceeded that critical density in low Earth orbit. And the only way you can bring it back to an equilibrium is to remove some objects. The number that NASA has come up with is that you need to remove five objects per year for the next one hundred years, or a total of five hundred objects. . . . Now, whatever you put in space, you have twenty-five years after you’re finished using it to get it out of space. And the way that’s usually done is in low Earth orbit, if you’re above five hundred kilometers, you just use the last bit of fuel to drop it down to below five hundred kilometers, and it will reenter naturally within that twenty-five years, so . . .
Q: Are those rules part of the UN rules on orbital debris?
Kessler: They are—yes, they are. They’ve accepted now all the way through. We formed an organization called the Inter-Agency Space Debris Coordination Committee, IADC for short, that has fourteen member nations all over the world. One of the things I’m doing now is I’m representing NASA on that group. And through the IADC, we—everyone has agreed that, yes, we—the whole world should conform to these rules. And they have recommended them to the United Nations, and the United Nations has accepted them in principle, but they haven’t added any numbers to that. They say, you should get out of orbit as soon as you can, something of that nature, rather than saying the twenty-five years. But the rest of the world pretty [much] uses that number of twenty-five years.
Q: What is it about the twenty-five years?
Kessler: Well, it was kind of an arbitrary decision. When you run the models, whether it’s twenty-five years or immediately, there’s very little difference. And when we came up with the rule, part of what we were looking at is we had to do something that was inexpensive. I had people in the military approach me afterwards who said, “Gee, if I had known you were going to give us twenty-five years, we wouldn’t have been against the program so much.” It’s a cheaper way of doing things. You keep the expenses down. And that’s what we were mainly concerned about early in the program. Because if we started telling people that we were going to raise their cost significantly, we wouldn’t have gotten anywhere. And, so, it was a compromise. And we’re still feeling that the twenty-five years is sufficient, but the problem really is, well, there’s no agency or anybody to enforce that rule. We even referred to them as guidelines, but within the United States, NASA, for example, is bound by them; ESA is, as I said, they’re bound by them. But they can still go to the secretary of state and ask for a waiver. And they have been doing that a lot in the past, but there are now people within the military, within NASA saying, no more waivers. We’re getting serious.
Q: What was the first piece of orbital debris, space junk. Was it the first Russian launch?
Kessler: Yeah, Sputnik.
Q: Sputnik, is that true?
Kessler: Yep. Some of those very early launches are still in orbit. I think Sputnik was launched at a pretty low altitude and reentered fairly quickly, but there was an elliptical orbit I know is still up there. But, gosh, nobody . . . I mean, some of my colleagues, they were convinced that there just wasn’t an issue with satellites colliding with one another.
And that was true very early in the program, but what they didn’t do is look, well, how is this going to progress? Because what happens is that when you’re looking at collision frequency generating debris, it goes at the square of the number of objects that you have in orbit. You double the number, you quadruple the collision rate. And when I wrote that it was at one collision every seventy-six years, and there were roughly less than five thousand objects in Earth orbit. Today there are three times that many. Three times squared is nearly ten—factor of ten—squared, and three squared, and you end up with ten times collision frequency, which is once every 7.6 years, which is pretty close to what everyone’s predicting today. That’s what you would expect with catalogued objects. So, it will continue to increase that way—it will increase as the square—you can get there fairly quickly because of that.
Q: I’m not sure what the right language to this question is, but are there certain launches or missions that create more debris than others, more junk?
Kessler: Well, there have been. For example, there for a long time, nobody really worried about the shroud put over a space craft. They just dump it overboard. They had explosives and cables that would come off. And now most of those things are tethered to make sure that they don’t do that.
Q: Does space junk ever decay in any way once it’s up there?
Kessler: There are some forms of decay; for example, you put up a plastic, there’s enough atomic oxygen in the upper atmosphere that it will slowly oxidize. And you’ll see these satellites that look like they’re gold. They’re actually covered with Mylar, which is a plastic surface, and the atomic oxygen will eventually—and they’re very thin—over periods of years, that will eventually eat away and you’ll see pieces of the Mylar come off. Same thing happens with paint. Paint flakes end up coming off. But other than that, the only other mechanism for eroding the surfaces is actually either meteorites or debris hitting those surfaces and taking hunks out of it all. And, of course, in the long term, that’s exactly what everything will end up doing.
Q: An average collision, what would be the result?
Kessler: Well, an average collision really could be catastrophic because the smallest of the trackable objects are really not massive enough to catastrophically break up another satellite, but it would generate a lot of debris. And the only hint that you would have that that was going on is you may see a few pieces come off of a satellite. . . . And these are pieces that [are] ten centimeters, or roughly a softball size and larger, but not as massive as a softball. But—we see that happening quite frequently—there are satellites, for some reason, that are generating fragments.
Q: So a small collision could be more problematic than
the occasional catastrophic one.
Kessler: That’s right. We’re just not seeing them because we don’t have the sensors to be able to determine what’s going on. But the catastrophic ones do get people’s attention because the whole satellite breaks up. It’s, like, you might as well have put a hundred pounds of TNT in it and blown it up. So the numbers that I use now, you end up with about a hundred fragments that are large enough to go on and cascade and cause another catastrophic collision, plus hundreds of thousands of centimeter-size objects that are capable of stopping just about any satellite from functioning, and then plus millions of millimeter-size particles that are capable of causing a satellite to stop functioning depending on where it hits, and it has [happened]—depending on whether or not it has shielding on it. For example, on the International Space Station, partially, when that was being planned, the debris issue was developing to the point that we could supply them with enough data that they planned to put shields on their spacecraft that would protect the habitation areas against roughly one-centimeter debris and smaller. And they, of course, they do collision avoidance against debris that’s ten centimeters and larger, but in between one centimeter and ten centimeters, there’s—they have no protection.
Q: In your opinion, what’s been the collision of space junk or the incident that’s been the most troubling to you?
Kessler: Well, what we don’t know is most troubling. Since the end of the shuttle program, the shuttle has always been looked at as a reusable vehicle, so it has to be inspected after every flight, and one of the things that you discover when you inspect it is it’s got craters on it. Some of those craters require some repair. And we started very early in the program analyzing the source of those craters and using that as data for our models as to what the real environment is. We’d rather have raw data to define the environment like we did during the meteorite days where we flew satellites and actually measured the meteorites penetrating surfaces. We’ve never purposely done that with debris yet—and I think that’s a big failing of the space program, not having done that.
Q: So the shuttle was an unexpected sort of space spy in a way. Because it came back with all this information that you didn’t necessarily—it wasn’t sent up to get this information, but it came back with it about orbital debris?
Kessler: We also repaired the Hubble Telescope and we brought some pieces back, and that has provided data. But by far, the best has been the shuttle. And within the last couple of years, they finished the analysis of the shuttle data. And one of the things that it’s showing is a large number of millimeter-sized particles, larger than we expected, that are stainless steel in origin, and they’re—we don’t know where they’re coming from. And there could be something going on; for example, the collisional cascading phenomena that I have come up with is the big stuff, and it gradually grinds it up into the little stuff. This—there could be a phenomena going on where the little stuff is eroding the surfaces of spacecrafts so much now that it’s creating an increase in debris from the smaller end. So, you got both ends started clawing away at each other. That’s pure theory. But these stainless steel particles could be a symptom of that, and that’s one of the things that we’re trying to—that NASA right now is trying to get a grasp on.
Q: One of the things that I found so interesting was the idea that it’s hard to come to a solution about what to do because of international issues.
Kessler: Yes.
Q: Because space doesn’t belong to one country. Do they really know whose debris it is?
Kessler: That’s one of the jobs of the space command, to identify the country of origin of everything they catalogue. In fact, their ground rules are it cannot become part of the catalogue until you know what country it came from. And so, consequently, there’s an awful lot of stuff waiting to be catalogued because they’re not sure where to assign it. But if you go to the US Space Command Catalogue, you will find literally a couple of thousand objects associated—several thousand—with the Iridium Cosmos collision that says this came from that collision.
So, they do work toward doing that, but the problem is that the way international law is set up, it’s different than the law of the sea. The law of the sea says if there’s an abandoned ship and you get a hold of it, it’s yours. But the law in space is that you’re always responsible for it; even if it’s abandoned, no one else can go up and touch it or you’re breaking the law.
And in severe cases, a nation might even consider it an act of war because by getting even a dead satellite, you’re trying to learn how they’re made or, you know, learn some secrets.
Q: So, if the US figured a solution for space junk it can’t go get a Russian piece of debris and apply the solution.
Kessler: That’s right, [not] without the cooperation and the blessing of the Russians. And, of course, there are ways around that. Russia is a member of the IADC. And, so, consequently, they could work together. In fact, they could easily, whatever nation develops the technique to do it could say, OK, here it is. Here’s the technique to do it, you use it, you go—you take care of it. And because it represents a danger to everyone, I really don’t see the downside of any nations saying, OK, yeah, I’ll remove my own debris, especially if somebody else pays—helps pay for it.
Q: What’s the possibility of a piece of space junk falling and landing on the Earth somewhere?
Kessler: Oh, it does it all the time.
Q: Oh, we just don’t know about it?
Kessler: We just—right. The small stuff mostly burns up, but there are—there is a material in there like titanium and some other metals that have a high melting temperature, and they consequently don’t burn up, and they do represent a hazard on the ground. But you’re more likely to get hit by a natural body reentering or an airplane falling on you than you are by space junk.
Q: The danger, in your opinion, is the collisions that happen in space. It’s not what happens on the ground here.
Kessler: Yes. The astronauts would much rather . . . if they had a choice, just surely, purely from a hazard standpoint, they’d be a lot safer on the ground than in space. In fact, right now EVAs [Extravehicular activity, a space walk] are [meticulously] planned. They don’t want to spend a lot of time in EVA because [a] millimeter-size particle could penetrate the space suit.
Q: So, why do we have to clean it up?
Kessler: Well, it depends on our infrastructure; what it really boils down to, it’s going to get more and more expensive to put things in space. Because you can get around all of this simply by adding shielding to the spacecraft. And that’s what the space station did. And one of the satellites that we looked at that’s being planned to be launched, they didn’t plan to add shielding, and we evaluated it and said, You need shielding, and they said, Oh, OK. But they didn’t like to do it. One of the requirements that we have on them now is that you’ve got to be able to do this maneuver—after you finished using the satellite, you have to be able to drop it down to less than twenty—so that it reenters within twenty-five [years], if it’s not functioning, you can’t do that. So, you have to assure everybody that it’s going to be functioning—that least only one chance in one hundred that it won’t be—and consequently, they end up having to add shielding just to be sure that you’re able to reenter it within the twenty-five years.
Q: So, the preventative measures cost money.
Kessler: That’s right.
Q: And avoiding space junk is costing money at this point.
Kessler: That’s right. And with time, that amount of money will continue to increase because you need to add more and more shielding. And it doesn’t pay off in the long term because the more mass, the fundamental problem is you got so much mass in Earth orbit all going in different directions, and the more mass you add, it’s like adding fuel to a fire. It’s going to want to grind up sooner or later. And, so, consequently, it’s not a long-term solution. The long-term solution, if you’re planning to use space in the future, is you’ve got to hav
e a different way of managing space. And one of the first things you have to do is ensure that whatever space you’re operating [in], that it represents a stable environment—a sustainable environment. And right now, we don’t have that.
Q: Recently we both have seen all these solutions popping up. Let me run a couple of them by you. You tell me why they would work or why they wouldn’t work. The vacuum idea?
Kessler: Vacuum?
Q: . . . of vacuuming it up?
Kessler: (laughter)
Q: That makes you laugh.
Kessler: Well, when they use the term vacuum cleaner, for a long time I laughed at that, too, because you, you know, you can’t—a vacuum just doesn’t work in a vacuum. You’re not going to suck anything up.
Q: How about the idea of lasers; the idea of zapping the junk with lasers?
Kessler: The problem is you got to get rid of the big stuff, and most of the people that are proposing lasers are only going after small stuff. And that’s just temporary. I mean, for example, this laser cannon that they want to put on the space station, it will have a range of one hundred kilometers. So, you’re not doing very much. What some people will [use] the lasers [for is moving] the big stuff, and the way they do that is they shoot a beam at it and vaporize part of the surface, and that vapor . . . then acts as a jet that that then propels it hopefully in the right direction, which is to make it drop down to a lower orbit and eventually reenter.
Q: The solar sail, the idea that it would drag it down into the orbit?
Kessler: The only way that you could cost effectively do that is put the solar sail on it before you launch it because you don’t want to go up there and attach it. You could do that. But, yes. In fact, there’s one company called Tethers Incorporated that actually is building an attachment you can put on any space craft, and it drops a tether down, and that acts like a silver sail in the sense that this tether then can use the Earth’s magnetic field to generate electricity, and that electricity—the process of generating that electricity—takes energy out of the orbit and actually causes it to reenter more quickly. So, it acts in principle, like a solar sail. [With] a solar sail you’re using the sun to slow it down, and in this case, they’re using the Earth’s magnetic field to slow it down.
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