#by david wright

[allthingsnuclear]

Iran Exaggerates Missile Accuracy

Iran announced today that it had successfully test launched a new version of its short-range Fateh 110 missile, claiming it has an upgraded guidance system that gives it high enough accuracy to “hit and destroy both land and sea targets, enemy concentration points, command centers, missile sites, ammunition dumps, radars and other targets with 100 percent precision.”

A ballistic missile is only guided during the first minute or so of flight when its engines are burning. During that time, the guidance system attempts to steer the missile to put in on the right trajectory to hit the intended target. Once the engine burns out, the missile flies without power and cannot be steered. This is like throwing a ball: you aim the ball by the speed and direction your arm gives it, but once the ball leaves your hand it flies on its own. (The fact that missiles fly unpowered for most of their flight is why ballistic missiles are called “ballistic.”)

Once they are launched, ballistic missiles have two main sources of inaccuracy.

The guidance system steers the missile while the missile’s engines are burning. One source of inaccuracy is the inability of the guidance system to put the missile on exactly the right trajectory to hit the target. These errors in accuracy are called “guidance and control errors.”

A missile of this range will reach a maximum altitude of about 75 km, which is above the bulk of the atmosphere. When the missile reenters through the atmosphere toward the ground at high speed, it is subjected to a number of forces that can knock it off its intended trajectory. It is buffeted by high altitude winds and density variations in the atmosphere. In addition, atmospheric forces due to asymmetries in the missile body or warhead or a spiraling of the missile as it reenters also affect its reentry. These are called “reentry errors.”

Even if Iran had developed a perfect guidance system so there were errors of type (1), there would still be very significant reentry errors, which are not reduced by a better guidance system. The reentry errors could be many hundreds of meters.

As a result, the idea that this missile has an accuracy high enough to allow it strike relatively small targets like ships, command centers, or radar bases, is simply not credible.

[allthingsnuclear]

AllThingsNuclear is Moving

After more than two years on Tumblr, allthingsnuclear is moving to another platform and we don’t want to lose you.

Our new site should be live on August 7. Our url will continue to be http://allthingsnuclear.org If you follow us on Tumblr and want to keep following us, please sign up for an RSS feed. Those of you who currently have RSS feeds should be automatically transferred to the new platform, but if for some reason you aren’t, please re-subscribe. Thanks for reading our blog.

[allthingsnuclear]

24th International Summer Symposium on Science and World Affairs

A second goal of the Symposiums is to create an international community of these technical experts who know each other personally as well as professionally. This allows people to share ideas and information, and to collaborate on what are inherently international problems. Since the beginning, these meetings have included some 500 people from 35 countries.

We have also used these meetings to help young researchers make a career in this field. More than two dozen scientists from Russia, China, India, Pakistan, South Korea, and Iran have spent time as research fellows at UCS and several other institutions, including MIT, Harvard, Princeton, and the University of Maryland.

And over the years, many of the Symposium participants have gone on to work on these issues as professors, government officials, researchers at think tanks, etc., in institutions around the world.

The meetings are currently funded by a grant from the Carnegie Corporation of New York.

[allthingsnuclear]

Lochbaum and Lyman Address NAS on US Response to Fukushima

The National Academy of Sciences (NAS) is working on a study called “Lessons Learned from the Fukushima Nuclear Accident for Improving Safety and Security at US Nuclear Plants.” It is currently in the phase of collecting information through public meetings.

The NAS website says the report will address the following issues:

1. Causes of the Fukushima nuclear accident, particularly with respect to the performance of safety systems and operator response following the earthquake and tsunami.

2. Re-evaluation of the conclusions from previous NAS studies on safety and security of spent nuclear fuel and high-level radioactive waste storage, particularly with respect to the safety and security of current storage arrangements and alternative arrangements in which the amount of commercial spent fuel stored in pools is reduced.

3. Lessons that can be learned from the accident to improve commercial nuclear plant safety and security systems and operations.

4. Lessons that can be learned from the accident to improve commercial nuclear plant safety and security regulations, including processes for identifying and applying design basis events for accidents and terrorist attacks to existing nuclear plants.

The two-year study is due out in 2014.

[allthingsnuclear]

Concrete Concerns at Seabrook

                                     ASR in a tunnel at Seabrook

One of the issues that has complicated the license renewal process at the Seabrook nuclear plant in New Hampshire is the discovery of potentially serious concrete degradation in some of the buildings.

This problem was first officially noted a year ago, when NRC inspectors confirmed that widespread cracks in the plant’s concrete due to a process called alkali-silica reaction (ASR) resulted in a “moderate to severe” reduction in concrete strength in five buildings.

ASR can occur when certain forms of silica in the bulk material in concrete (such as crushed rock and sand) react in the presence of water with such chemicals as sodium or potassium, which are commonly found in the cement paste. This reaction produces a gel that forms in the pores of the concrete and then expands, causing stress and cracking. Over time, those cracks can join together to form larger fissures in the cement and compromise the concrete’s structural integrity.

To better understand the technical issues related to the concrete damage, we hired a concrete expert to review the publicly available documents. Paul Brown, a professor of ceramic science and engineering at Penn State University, wrote a report that discusses the problem and identifies some outstanding questions that need to be answered. Working with the group C-10, we released his report along with a summary of the issues.

Prof. Brown concluded that neither plant owner NextEra Energy nor the NRC fully understand the scope or origins of the problem and therefore cannot adequately assess the plant’s structural status. His report provides a list of key questions the NRC and NextEra Energy need to address before they can assure nearby communities they are not at heightened risk.

In particular, NextEra and the NRC must determine to what extent ASR is occurring, what other negative reactions—including corrosion of embedded steel in the concrete—are occurring, and what basis there is for knowing which steps will be effective in addressing these problems.

NextEra Energy applied to the NRC in 2010 for a 20-year renewal of the operating license for Seabrook. Its current license was issued in 1990 and does not expire until 2030; the license renewal would allow Seabrook to operate until 2050. NRC and NextEra analysis of the plant must therefore identify and understand aging issues well enough to predict its behavior for the next 40 years.

[allthingsnuclear]

Questions about North Korea's Unha-3 Failure

Three weeks have passed since the North Korean failed satellite launch and we’re still waiting for more information to accurately assess what happened. The United States, as well as Japan and South Korea, deployed many sensors in the region to watch the launch, and should have gathered very good data on what happened. However, it is unclear how much of that information will ever be made public, since countries tends to be very careful about releasing anything that might provide information about “sources and methods” of gathering information. However, I expect the basics of the event will eventually come out.

In the meantime, here is what we know:

North Koreans called this launcher the Unha-3 (Korean for “Galaxy-3”). Whereas US officials referred to it as a Taepodong-2 missile, since it appeared to be a derivative of a missile US intelligence first saw near the Korean city of Taepodong in early 1994.

North Korea said the three-stage rocket was intended to launch a small (100-kilogram) satellite, the Kwangmyongsong-3, into polar orbit. The satellite reportedly carried a camera to send back photographs of the earth, but the main goal was simply to try to place it into orbit and gain experience operating and communicating with it.

Photographs of the Unha-3 show it was very similar to the Unha-2 that North Korea used in its failed April 2009 satellite launch. One noticeable difference is that it appears this rocket carried more fuel in its third stage. This was expected, however, since the Unha-3 was launched from the new Sohae Satellite Launching Station on the west coast to the south, rather than to the east (as the Unha-2 was), to avoid flying over Japan early in flight (see figure above). This change in flight path is significant because rockets launched east gain speed naturally from the rotation of the earth. Therefore, the extra fuel aboard the Unha-3 was needed to compensate for this difference when fired south.

The Unha-3 launch took place on Friday, April 13, 2012 at 7:39 am Korean Standard Time (KST) (Thursday at 6:39 pm EDT) and failed shortly thereafter, with the rocket splashing down after traveling less than 400 km.

What May Have Happened

The engines of the first two stages of this rocket burn for about two minutes each, so knowing the exact time at which the failure occurred can help us understand which stages were involved and may give clues as to the cause. As of now, this information has not been released. As an alternative, we can try to glean this information from the reported splashdown zones.

From reports in the past three weeks, the two most credible splashdown locations are these:

A. In a statement shortly following the launch, an official US report gave the splashdown point as 165 km west of Seoul. In particular, North American Aerospace Defense Command (NORAD) and US Northern Command stated that:

Initial indications are that the first stage of the missile fell into the sea 165 km west of Seoul, South Korea. The remaining stages were assessed to have failed and no debris fell on land. At no time were the missile or the resultant debris a threat.

This location would be roughly 300 km from the launch site.

B. However, South Korean reports have said that the splashdown occurred 200 km west of the South Korean city of Gunsan. This location would be about 400 km from the launch site and just short of the intended splashdown zone for the first stage announced by North Korea before the launch.

      Based on these two locations, we can conclude several things:

Several media have reported that sensors had detected an abnormal “flare” around the rocket at 81 seconds after launch. However, whatever happened at that point, which is unclear from the information publicly available, the rocket must have continued accelerating well past that point. We know this because if the engines had stopped at 81 seconds, then the debris would have fallen very close to the launch site—within 100 km—and therefore well short of either points A or B.

If the stages fell at point A, that is consistent with the first stage burning roughly as intended for about 104 seconds. In this case, the failure would have occurred during the operation of the first stage and before staging took place. If it failed at that point, all three stages would have fallen into the Yellow Sea about 300 km from the launch site after reaching a maximum altitude of about 120 km, as some reports have stated. Atmospheric forces as the rocket fell would have broken it into pieces.

It is also possible that problems with the first stage could have caused the engines to burn with less than the intended thrust, so that the first stage could have burned to completion but not gone as far as was expected. If the staging process did not work correctly, all three stages could have fallen around point A.

If instead the stages fell at point B, that would suggest that the first stage worked essentially as intended, but that ignition and separation of the second stage did not occur properly so that it fell with first stage into the sea at this location. A study by Chang Young Keun, a professor at the Korea Aerospace University, was cited in the JoongAng Ilbo and argued that staging was the problem. However, his analysis reportedly assumes a 10-second delay between first-stage burnout and second-stage ignition, which is unlikely for technical reasons and therefore raises questions about his analysis.

It is also possible that relatively large objects fell at both points A and B. In this case:

One possible scenario is that a large object fell off the rocket about 104 seconds after launch, which would have splashed down at point A, while the rest of the rocket continued to burn. A staging failure could have then caused the rest of the rocket to fall at point B. Some reports suggest that either the shroud covering the front sections of the launcher, or even the third stage, may have broken off during first stage burn. However, it is not clear what might have caused this; one suggestion is that it resulted from the rocket passing Mach 1 or experiencing peak atmospheric forces (“Max Q”), but those things happened much earlier in the flight.

A second possibility is that the first stage burned to completion, but with low thrust, and fell at point A, and that the second stage ignited and burned briefly before failing, which carried it to point B. This option assumes that the staging was successful. If this was the case, it means there would have been problems with both of the first two stages.

It is also possible that the launch was aborted by the command center before mechanical failure could fully set in. North Korea reportedly announced prior to the launch that the rocket was equipped with a flight termination system that would allow operators to shut down the engines manually if the ground station detected a problem. It is not clear whether this is the case. However, it is possible that if, as some sources have suggested, the first stage burned to completion but there was a problem with staging, that the North may have aborted the flight at that point.

What Would Help to Understand the Launch Failure?

Four pieces of information that would help pin down what may have happened:

Exactly how long after launch did the failure take place? This would help clarify whether the failure was during the operation of the first stage or involved the staging process and the second stage.

Where did the rocket debris splash down, and what splashed down at those points? Knowing, for example, whether the first stage traveled 300 or 400 km, or whether any part of the rocket traveled 400 km, would shed light on what actually malfunctioned.

Were there any irregularities in the path of the rocket or the operation of the engines while the engines were burning? The type of abnormality observed may help identify the cause of the problem. For example, if the launcher was seen to be deviating from the intended trajectory, it is possible that it was destroyed intentionally.

Was there was an explosion that destroyed the rocket, or did it simply lose power?

What North Korea May Have Learned from the Launch

North Korea clearly did not learn anything about operating a satellite from this launch, since it did not succeed in placing the Kwangmyongsong-3 into orbit. Moreover, after several attempts, it still has not learned much about using the third stage to launch a satellite into orbit. The closest it has gotten to achieving this was its 1998 launch, when the third stage ignited and separated, but apparently then became unstable and broke apart.

Most countries launching rockets put sensors on all the major systems that constantly send back information about the status of the rocket during launch. If something goes wrong, sorting through this data can help experts determine what happened, like looking at an airplane’s black box. We don’t know how much “telemetry,” as this is called, the Unha-3 was designed to send back. Without it, Pyongyang would have little chance of understanding in detail what went wrong.

However, assuming the Unha-3 was sending at least some telemetry, how much could the North learn? The first two stages apparently worked in the 2009 launch, suggesting that the rocket’s systems work in principle, but have reliability problems. The telemetry from the Unha-3 may tell them which system failed this time, and might give them enough information to reduce the likelihood of it happening again to that particular system. But the failure happened so early in flight that they would have gotten little or no information about the performance of several key systems in the upper stages.

On the other hand, it is worth keeping in mind that having a string of failures is not unusual for countries developing a launch capability, so it is difficult to draw strong conclusions from this failure about the overall state of North Korea’s rocket development program. For example, both of South Korea’s attempts (in 2009 and 2010) to launch a satellite failed, and the first stage of its launcher is built by Russia, which has a lot of experience with this technology.

However, North Korea’s successive failures coupled with other facts, like the lack of flight testing and questions about how reliant North Korea’s program is on foreign technology, does suggest a program that is less advanced than is widely assumed.

                         This post also appears at 38north.org.

[allthingsnuclear]

CSIS Briefing on NK Missiles

                   Last Friday I gave a talk at the Center for Strategic and International Studies (CSIS) in DC about the recent North Korean launch failure and its missile program. The audio of that talk is on the CSIS website, as are the slides that went with it.

One amusing thing that resulted from this talk was a set of press reports in Asian papers stating that I claimed the KN-08 missiles seen in the North Korean parade were fakes made of “layers of paper.” I do think the missiles seen were mockups and not real missiles, but I never said they were made of paper.

As far as I can tell this started with a Japanese-language article in Yomiuri that I’m told used the word “haribote,” which apparently literally translates to “made with think paper.” If that was intended to convey the sense that the mockups might represent a missile that currently exists only as a design on paper and not an actual missile, that’s in keeping with the spirit of what I said. Other newspapers in the region, however, seem to have picked this up from Yomiuri but interpreted it much more literally.

[allthingsnuclear]

North Korea’s New Missile: Not an ICBM

                                Before North Korea’s failed launch a week ago, there was a lot of talk about the North unveiling a new long-range missile in its April military parade. As a result, when North Korea did display a missile body not seen before, people began calling it an ICBM. For example, yesterday the New York Times wrote:

During the parade in Pyongyang, the North’s capital, six trucks hauled what appeared to be a new type of intercontinental ballistic missile.

This idea seemed to be reinforced by the fact that it was carried on a larger truck than had previously been seen in North Korea, so people were left with the impression that “big truck = big missile.”

But the missile—even if real—is too small to be an ICBM using any of the technology North Korea appears to have.

The picture above shows, to scale, the new missile body (called the KN-08 in the west) on the left and the Unha-3 launcher on the right. The Unha-3 is about 30 m long and 2.4 m in diameter. The KN-08 appears to be about 18 m long and 2 meters in diameter.

If used as a ballistic missile, the liquid-fueled Unha-3 could likely carry a nuclear-weapon sized warhead to roughly intercontinental distances. If the KN-08 was also liquid fueled it would have a range much shorter than intercontinental. It simply could not carry enough propellant to reach the high speeds needed for a long-range missile.

So some people have asked whether it might instead be fueled by solid rather than liquid propellant. But North Korea does not have the ability to build long-range solid-fueled missiles. Its only solid-fueled missile is believed to be the Toksa—which appears similar to the Soviet SS-21 missile—with a range of about 100 km. And it is not clear whether Pyongyang has learned to produce even such a small solid-fueled missile or whether it purchased SS-21s.

In either case, producing large, solid-fueled rocket motors is a very significant technical challenge. For example, the propellant must be rigid enough to support its own weight, but must not be so hard and brittle that it forms cracks, which can cause the propellant to explode when it burns. These requirements are especially demanding for a mobile missile, since the propellant must be able to withstand the additional stresses associated with moving. China only built a road-mobile solid-fueled ICBM recently, after several decades of development. This appears to be well beyond North Korea's capability.

I have not been able to identify any known missile with the same size and shape as the KN-08 that it might be based on. Some people have claimed a resemblance to the Chinese DF-31 road-mobile ICBM, but they do not have the same length, diameter, or shape, so that comparison is pretty meaningless.

Is the KN-08 Real?

An analysis by two German missile experts of the six KN-08 missile bodies seen in the parade in Pyongyang leaves little doubt that what was seen in the parade were mockups—and not terribly good ones.

The question then is whether these were simply Potemkin missiles paraded with the hope of gathering press like the excerpt from the New York Times above, or whether they represent mockups of an actual missile that is being developed. If it’s the latter, there are several things to keep in mind:

As the German analysis shows, the six mockups in the parade differed from one another in the placement of key parts, etc., and appeared to show contradictory details, such as ports appropriate for filling liquid propellant tanks but also channels for electric cables that are appropriate to solid engines. This suggests there either is no underlying design, or the design is so preliminary and schematic that it does not flesh out basic details.

If a real development program exists and the missile is liquid fueled, then it is possible that the missile could appear in the coming years, but it would not be a long-range missile, as discussed above.

On the other hand, if the mockups indicate an interest in developing a solid-fueled missile with potentially ICBM range, then that missile cannot be expected to appear any time soon for the technical reasons discussed above.

The KN-08 Transporter

The truck seen carrying the KN-08 in the recent parade has drawn a lot of attention in the past week.  The missile transporter (top photo below) appears to be a modified version of a large Chinese truck (lower photo below). This raises questions about whether China violated UN sanctions against North Korea by selling it trucks of this kind. If China modified the truck by adding the bed that carries the missile it would be a clear violation, but it may well be that the same people in North Korea who built the mockups built the bed. Whether this is a violation of sanctions will probably depend on details like who China thought it was selling the trucks to, assuming the transaction was handled by a North Korean front company. UN experts will have to sort this out.

But it is important that people not conflate the truck and the missile and jump to the conclusion that China was involved in developing the KN-08 missile. I have not seen anything yet related to the missile that suggests Chinese involvement. As noted in our previous analysis, the technology we see throughout the North Korean rocket programs appears to be of Soviet/Russian origin, not Chinese.

“Mobile” vs. “Moveable”

Finally, as I’ve pointed out before, it’s important to understand what it means to put a large liquid-fueled missile on a transporter. Because these missiles are so large and heavy and the rocket body has very thin walls, they would be transported without fuel in them. They could then be transported to a location, erected, loaded with fuel, and  launched.

Making missiles “moveable” can be useful since it means they are not tied to a known launch site. But a liquid missile would have to be serviced by a fleet of trucks carrying the fuel (about 70 tons of fuel for a rocket the size of the Unha-3). And it would likely take a couple of hours to prepare for launch by erecting and fueling the missile, during which time it would be vulnerable.

This is different from what people usually think of as a “mobile” missile, which is assumed to be fueled when it is transported, so that it can quickly get into position, be erected, and fired.