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Timeline of the 5 April 2009 U’nha-2 Launch

Ok, so I don’t have the amount of confidence in my prediction as the title seems to indicate. But everybody else is making blanket statements so why can’t I?

After returning from the Mid-East on Thursday, I had to catch up quickly on what was going on with North Korea’s missile/rocket program. My post wondering where the launch notification was represents my first attempt to catch up on the DPRK’s activities, after thinking exclusively about Iran for the last two weeks. I’m really uncertain why July 4th was picked up by so many people as the expected launch date. It seems just too soon (I’m talking here about the practical arrangements, not the time necessary to diagnose what went wrong with the last launch and correct it, which is also too short!) and, as far as I can tell, there was absolutely no sighting of the rocket on either launch pad.

Taking a look at the timeline, as determined by various milestones of the previous U’nha-2 launch as reported in the media, indicates it takes about two months to move the rocket to the launch site, assemble it horizontally in an assembly building, erect it on the launch pad, fuel it and wait for good weather to launch. That includes about three weeks warning time North Korea gave by filing a launch notification with international organizations. If we (naively) assume the same amount of time, then they should launch in early August. That assumes the June 1st initial indication of launch preparations (shipping large cylindrical objects by train) that I found was the first one published. It also assumes that intelligence agencies and media organizations are just as efficient as publishing the information as they were the last time. Furthermore, it assumes that North Korea does not need to make any long term preparations that might have been performed for the last launch before the preparations were spotted by the West.

If all of this is true, the first indication should be DPRK’s filing a notification of stay clear zones, probably in about a week. If that happens, everything will be on target for a launch during the first week in August.

Of course, given all these assumptions, I could be proved wrong any day now!

North Korea is expected by just about everyone to launch at least one (and possibly two?) large missiles/rockets this weekend. And yet, they do not seem to have filed a warning to mariners and airmen notification with the International Civil Aviation Organization (ICAO). This is something they seemed to have been very proud to do over three weeks before the April 5th launch. What’s going on? Have they abandoned their adherence to the Outer Space Treaty already? Or are they just not as far along in their preparations for these (this) launch(es) as they are being given credit for?

Never take anything for granted. I’m afraid I put off something that Peter Brown, who is always on top of the interesting stories in Asia as he writes for the Asia Times, has been bugging me about. Sorry Peter! I thought I knew what the answer would be and I put off calculating the elevation of the U’nha-2 as a function of time far too long as I worked on other stuff. I assumed that the U’nha-2 probably had its second staging event below North Korea’s horizon. It turns out that I was wrong. The rocket was almost certainly 10 degrees, or perhaps even more, above the launch pad’s horizon when its third stage would have burnt out. In fact, the rather simple model I have for the trajectory (which does fit the observed contrail and have its first and second stages splash down in their respective zones ) has the rocket finally disappearing below the horizon 736 (well past the 535 seconds the rocket was actually under power) seconds into its flight. North Korea should have been able to receive telemetry from the rocket using land-based receivers all the way to orbital injection and even past that. (Peter has been investigating reports that a ship he believes was sent out to monitor the rocket had to return to port before the launch because of mechanical problems. It turns out, however, that such a ship was probably not needed.

A couple of thoughts immediately jump to mind:
-They most likely have not had enough time to correct what ever problem caused the April 5th failure unless it was the same type of failure that caused the August 2008 Safir second stage to fail. (I believe that the U’nha-2’s third stage is the same as the Safir’s second stage.) In that case, they could use the Iranian expertise to quickly fix the problem. But if that was the cause of the failure, why didn’t they fix it before the April launch attempt?

-The fact that they already have a rocket body ready to move to the West coast launch complex means that they are following what in the US would be called “concurrent acquisition.” In such an development path, the North would be “mass producing” U’nha-2’s even as it develops it. This has been practiced in the US, and has in fact, been used for many of the US ICBM development programs; programs which are judged so vital to the national interest that the US has been willing to run the risk of building into a number of missiles any design/production problems that might be discovered during the testing program.

-The comments above assume that simply because the rocket was visible to North Korea, the DPRK had telemetry and was able to diagnose the cause of the April 5th failure. Just because that makes a lot of sense doesn’t mean they actually had telemetry. It is conceivable that they simply have no idea why the rocket failed. (I’ve argued before that the North’s rocket scientists might not have told Kim Jung-Il that the missile didn’t make it into space. I hadn’t really thought that they might not know it failed either. However, it would not be the first time a country spent years and millions of dollars on developing missiles without any telemetry. Iraq never had telemetry on any of Al Hussein’s it fired off.)

Update: Murray Anderson pointed out a significant error I had in an earlier version of this post. Thanks! I’ve corrected that error, which I blame on my bad eyesight in confusing Isp with stage burn time in my rush to get this analysis done.

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The reconstructed flight path angle and the fitted pitch program are shown as a function of time after launch. The flight path angle is found using the fitted trajectory to provide a smooth curve. The start and stop of the fitted trajectory are marked with a square and a circle respectively. (Note that the rocket passes through the speed of sound during the fitted trajectory.) The slope from the portion corresponding to the reconstructed trajectory is projected back, as a dotted line, to the launch.

I’ve just finished my paper on reconstructing a significant portion of the U’nha-2 trajectory using the DigitalGlobe/GlobalSecurity.org’s satellite image of the launch. (I’ve just submitted it to Science and Global Security.) It’s interesting because the U’nha-2 passes through both the speed of sound and the maximum dynamic pressure (Max Q) during the reconstructed trajectory. What’s particularly interesting is that the rocket is not following a gravity turn as it does so. Instead, it is changing its flight path angle at a much slower rate. Now, it is possible that it could arrange to pass through the speed of sound at a zero angle of attack , or it could pass through Max Q at zero angle of attack, but not both. It also indicates that the DPRK was trying to get the maximum boost from lift.

If it had been trying to do the same thing for its 2006 Tae’podong II launch, perhaps the rocket experienced too high of an aerodynamic load? Another tantalizing feature that I found, though since it was before the fitted trajectory it has to be considered only an interesting indication, I found the vertical rise time was about 15 seconds (15 seconds between launch and when the rocket kicked over) while the optimal vertical rise time for a rocket with a thrust to weight ratio of 1.35 would be 12 seconds. Not bad! What is certain, however, even if it does come before the fitted trajectory, is that the U’nha-2 was kicked over a lot harder immediately after the vertical rise than it was being tilted during the fitted portion of the trajectory. The North Koreans were trying to minimize gravity losses as much as they could before Max Q. An interesting feature that might also contribute to why the 2006 launch attempt failed.

…and they should be yours too! There is a question of when an international practice becomes a binding law. Some invoke the Treaty of Vienna, a highly controversial subject in the United States, to say that a treaty obligation arises as soon as a country signs a treaty regardless of whether or not it is ratified. Others talk about international norms becoming binding international law if enough countries follow it for long enough. I think I discovered the answer as far as space goes: its the “law” as soon as the space insurance industry decides it is.

The space insurance industry is now thinking that space-debris mitigation guidelines being propagated by the United Nations might define whether or not a satellite operator is at fault for any damage fragments from that satellite (or its launch vehicle) might do if those guidelines are not followed. That means if they don’t “re-orbit” a geostationary satellite to the so-called super-sync region several hundred kilometers above the geostationary altitude, they will be liable for any future damage. If they don’t have plans for doing that at launch time, they might not get launch insurance. If they orbit their satellite anyways and it does cause damage, the insurance companies of third party satellites damaged as a consequence will sue to recover the damages. This will probably be the financial incentive necessary to get satellites owners to comply with those guidelines (and codes of conduct).

This is in line with the unsung role insurance companies have played in preventing terrorists from sending WMD into US ports in shipping containers.

So, thanks insurance companies! Now about my auto rates…

I’m in Montreal for a conference on space debris. It’s a wonderful city (we wondered into Chinatown for dinner last night and, spiritually, I haven’t left yet) and I hope the conference is half as good. It opened today with a round table discussion on the governance of space: what can and should be agreed on to protect the commons that all space faring nations share. It’s the first conference I’ve been dedicated to some aspect of space I have already learned one thing about such conferences that they share with conferences about nuclear energy: there is a high fraction of the participants who believe their job is to boost human space flight (or, in the case of conferences on nuclear energy, nuclear power plants). One of the panel members in the opening roundtable suggested allowing states to “own” areas of the moon provided they establish permanent human occupation there. It would, he suggested, provide significant motivation for nations to establish permanent manned moon bases. He is a lawyer, too.

Article I of the Treaty of Outer Space says:

Outer space, including the Moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies.

[Emphasis added.]

So he was willing to junk all that in order to encourage the exploitation of space. Of course, with a new race to the Moon shaping up, this is a funny time to start throwing out key parts of a treaty that forms the basis of all space law and enshrines some of the finest principles the world community has agreed to, but what are you going to do?

What would happen if we did allow countries to claim parts of the Moon as their own? He is undoubtedly right it would encourage countries, preferentially those who already have established space programs, to establish Moon bases if for no other reason than to prevent theoretically valuable resources from being claimed by other nations. The next thing that would happened (about 5 seconds after a new treaty establishing that right was signed) is scientific studies of the Moon would be declared state secrets and humanity’s quest to understand it’s the origins of the solar system would become proprietary information. A good example of that is the recent quest to find water on the Moon. Can you really imaging any country releasing the information that there was valuable water close to the surface of such-and-such crater? It has also turned out that the distribution of important minerals has yielded clues to the mystery of the Moon’s origin. And that is just the scientific implications. What would granting sovereignty on the Moon do to international collaboration in space? Would all space technology become state secrets?

Perhaps I’m being overly dramatic. Perhaps only good things would come from granting sovereignty over different parts of the Moon. But I’m glad the U.S. went there in peace, for all mankind.

Jan Stupl’s contour of pixel intensity of the U’nha-2 contrail image

Jan Stupl, who is a Science Fellow at Stanford’s CISAC this year and who has done an amazing experimental and theoretical analysis of the US Airborne Laser, produced a very important processed image of the DigitalGlobe/Globalsecurity.org image of the U’nha-2 launch. This has allowed me to add a considerable number of points to the reconstructed trajectory. That in turn clarified a number of points that earlier analyses (that, fortunately, I did not post here) had seemed to indicate that the U’nha-2 was using a rather primitive pitch program with a step function in its thrust vector control algorithm; much like Iraq’s Al Samoud II used. (The pitch program on a guided rocket or missile “kicks” the rocket over from its vertical liftoff orientation and controls the shaping of its powered flight toward its target or orbit insertion point.) In those step pitch programs, the jet vanes of the Al Samoud, for instance, were set at one angle for a certain amount of time and then switched very fast to another angle creating a “step” in the off axis thrust. Its not at all clear that the U’nha-2, which is probably rather fragile, especially in its third stage, could take such kicks. (By the way, I seem to recall that the SCUD-B also uses such step functions in TVC but I can’t seem to find confirmation of that in my records. Do any of you readers know for sure? Documentation of that one way or another would be greatly appreciated.)

With more points on the trajectory, I can rule those sorts of primitive pitch programs out. The U’nha-2 used a more continuous pitch program perhaps more suited for either vernier or gimbaled engines than jet vanes. To determine this, I fitted an arbitrary pitch program run on a rocket model developed by Ted Postol to the reconstructed trajectory. The fit was free to move the times of the pitch steps as well as the angles of thrust to any point that created the best fit. Perhaps surprisingly, it picked times corresponding to ranges outside the reconstructed trajectory and a continuous linear change in thrust angle inside the reconstructed points. (I’ve pointed out the closest “step” in thrust angle rate at 35 s.)

I actually expected, especially when I had fewer points, that it would get a step in thrust angle corresponding to the “kink” at 1.2 km range. After more work, it turns out that the “kink” corresponds to the points on and to either side of the highest ridge in the image. The altitudes of the points of the terrain at which the contrail is projected onto is important in reconstructing the actual trajectory and any error in that terrain height directly produces errors in the reconstruction. I suspect that the altitudes I found for that peak are somehow approximations (perhaps created by averaging nearby altitudes?) and that is what caused this kink.

I’ve also looked at various types of trajectories that maximize the range of the U’nha-2, what would be called ICBM trajectories. All of these trajectories, independent of whether or not they had the same or shorter burn times for the third stage or even if they had a third stage, were shallower than the reconstructed trajectory and would seem to say that the DPRK flew a space-launch trajectory. However, my program for simulating trajectories is what is known as a “three degree of freedom model” and does not include very important factors such as bending forces on an extended rocket body. I’m hesitant to use such a model in this very important region very close to the launch point to answer such questions.

It’s Patriot’s Day here in New England and I have to run off and see the Boston Marathon run by my house. Happy Patriot’s Day!

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Or, to be more precise, 44 seconds. For those of you very few who can possibly muster enough interested in reading a third posting on this subject, DigitalGlobe has just told Globalsecurity.org the exact time the contrail image was taken: 2:31:16 GMT. (I have to thank Tim Brown and his colleagues at Globalsecurity.org for being so generous as to provide me with all this support. You guys are the best!) This 44 seconds difference in timing makes a big difference in the reconstructed trajectory. You have to remember that the Worldview-1 satellite is moving at nearly 7.7 km/s so it is 340 km closer to North Korea then previously thought. This changes the viewing angle enough to make the reconstructed trajectory much more consistent with various models. We will have to wait to see if those modelers can use this to tell the difference between ICBM trajectories or space launch trajectories.

Update: A number of people, including Wonk-reader Allen Thomson, have pointed out that in addition to the vapor contrail near the end of the trajectory imaged on the DigitalGlobe/Globalsecurity.org photograph, there is a “thermal contrail” extending much farther back to the launch point. Computer-wiz Jan Stupl who needed a break from writing what is going to turn out to be a ground-breaking paper on the Airborne Laser, did a contrast enhancement on it and made it clearly visible for nearly 3/4 of the way to the launch pad. Thanks everyone! I wont be reporting anymore intermediate results but as soon as I finish the complete analysis, I’ll post a link to it.

This plot from Google Earth shows the announced splashdown zones and the locations of the splashdowns from a story in the Yomiuri. Credit: David Wright.

Based on where the second stage fell, it is clear that the North Korean satellite launch was another failure.

Oh-for-three. These guys really suck.

NORTHCOM says:

Stage one of the missile fell into the Sea of Japan/East Sea. The remaining stages along with the payload itself landed in the Pacific Ocean.

No object entered orbit and no debris fell on Japan

(I would also direct you to SEESAT, where they have a nice discussion going.)

Update. The wags are out. “Paul” writes:

According to the US Navy the highly unique North Korean satellite has entered subaquatic orbit in the Pacific Ocean, and is transmitting melodies of the immortal revolutionary paeans Song of General Kim Il-sung and Song of General Kim Jong-il on a 15 kHz acoustic channel.

Seriously, the best thing about this blog are the readers. That is pure genius, right down to the frequency.

Weather conditions over the Korean peninsula look like they favor a Saturday, 4 April 2009 launch. Hopefully, we will see something more of the launch than the 10 seconds or so of video that came out for the Tae’podong 1 launch in 1998. So, what should the casual observer look for? Here is my list:

1) Relative size of the first, second and third stages

2) How many engine nozzles are sticking out of the first stage?

3) Can you see vernier engines? (Little engines that help keep the rocket vertical and on the proper trajectory during flight.) They might either be down at the bottom of the first stage with the other engine nozzles or perhaps sticking out of the side of the first stage.

4) How big is the nose fairing (the nose cone covering whatever payload is there). Does it have a bigger diameter than the third stage? Can you tell its size relative to, say, the Safir rocket’s nose fairing?

Assuming any satellite makes it into orbit:

1) What are the apogee (maximum height of the orbit) and perigee (minimum height of the orbit)?

2) Did North Korea announce the payload mass the way Iran did? If they do, is it more massive than the Omid? Or on the same scale as the Omid?

3) Did the first and second stages land in the announced stay clear zones? (I expect that other countries, like Japan, will announce this.)

Other readers will, of course, have their own list of things to look for and I imagine they will not be shy in listing them.