A Silver Lining When Rockets Fail In The Clouds

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Robert Siegel speaks with Jonathan McDowell, an astrophysicist at the Harvard Smithsonian Center for Astrophysics, about what can be learned from rocket failures like North Korea's.

ROBERT SIEGEL, HOST:

This is ALL THINGS CONSIDERED from NPR News. I'm Robert Siegel. Getting a missile into space is complicated. The math, the physics, the engineering. In fact, it is rocket science.

Witness the 92nd flight of North Korea's Unha-3, which crashed into the Yellow Sea. The crash, as embarrassing to the North Koreans as it may be, could yet possess some silver linings for them. From every failure comes knowledge.

Joining me is Jonathan McDowell, an astrophysicist at Harvard University and an expert on the history of missile programs. Welcome to the program.

JONATHAN MCDOWELL: Great to be here, Robert.

SIEGEL: And, if I were a North Korean, could I plausibly call this failure a learning experience?

MCDOWELL: Oh, absolutely. The critical thing about these very complex systems, it's very hard to make sure all the systems are going to work together right the first time. So the important thing that you do is, every second, you radio back thousands of pieces of information about how the rocket is doing, how hot it is, how much fuel you're using, so that, if that's the last second you hear from it, you can then figure out what it is that went wrong.

So I'm sure that the engineers in North Korea will be poring over that data and hoping to do better next time.

SIEGEL: Is that data more important than actually finding bits of the missile and being able to examine them to see what might have happened?

MCDOWELL: Yes. Probably, because the chance that you find the right bit of the rocket that will give you the clue you need is pretty low. I think that Western intelligence agencies are going to be very interested to fish what they can out of the sea to understand the design of the rocket. But for the North Koreans, the telemetry, the radio data is probably the more important thing right now to figure out what happened.

SIEGEL: From what you know about the history of missile failures in other countries, first of all, can one glean anything from 90 seconds and say, oh boy, they must have had umpteen things wrong? Or could that have been one number, one bolt that was out of place?

MCDOWELL: Right. Well, this would have been at the end of the first stage burn. So rockets are made up in sections called stages because what you do is you don't want to carry the dead weight of the fuel tanks all the way to space with you, so you use up one fuel tank and you throw it away.

And Unha-3 was a three stage rocket. The last time they flew in 2009, the first two stages worked fine and it was the third stage that didn't. So actually, they didn't get as far this time as last time, which is going to be a disappointment for them.

And so what you can figure out is that things were working pretty well for the first part of the first stage burn. Either it didn't shut down correctly or it didn't separate from the second stage correctly.

SIEGEL: This seems like an incredibly expensive process of trial and error to have a launch of a missile and learn from it and try to take a few steps forward.

MCDOWELL: Well, you know, in the first few years of the space age, both the United States and Soviet Union had about a 50 percent success rate of getting their rockets into orbit and that was even after a lot of trials of suborbital missiles. And so it is tricky and it is expensive, particularly for a very poor country like North Korea. What they really need to be doing is launching dozens of these, but they just don't have the resources to do that to learn properly.

SIEGEL: Are there some famous stories, good lore of learning from failure in rocket science?

MCDOWELL: Well, you know, I think there are really two kinds of failures. There are the ones where you go, oh, you know, we'd never have guessed this, and you learn something new about how materials operate at high temperatures, at high pressures. And then there are the ones where you go, oh, doh, we should never have made that mistake.

The classic one is one of the first Venus probes where a simple dash omitted in the guidance equation made it fly the wrong way, so it ended up at the bottom of the Atlantic instead of deep space.

Certainly, what you want to end up with is to be able to tell your boss that the mistake that lost your $100 million rocket was one that you could not have foreseen, not a units error like the one that the Mars probe, you know, crashed into Mars because they were using English units on one side of the fence and metric units on the other.

SIEGEL: Yes. That's the one that lives on in lore. I guess, you know, the North Koreans said this was to launch, I think, a weather satellite, but it was widely suspected it was designed for launching an atomic warhead, at some point - a nuclear warhead.

The whole notion of using nuclear-tipped long-range missiles in war has to assume a hugely high level of confidence. Otherwise, you fire off your missile and the other side responds and you're finished and you haven't hit anything.

MCDOWELL: That's right. I don't think that a North Korean long range missile program is a serious deterrent from their side because they know that if they ever were to launch such a system in war the United States and its allies would just obliterate them. So, you know, the most they're ever going to have is a few intercontinental missiles and we have 1,000.

SIEGEL: Well, Dr. McDowell, thank you very much for talking with us.

MCDOWELL: Thank you, Robert. It's been a pleasure.

SIEGEL: Jonathan McDowell is an astrophysicist at the Harvard Smithsonian Center for Astrophysics.

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