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Iran’s aerospace program has been so active in the last few years it should be possible to say something about their development philosophy: the technological arc or trajectory they are following. For instance, why did they “jump” from SCUD-type missiles to the Shahab-3-type? Why didn’t they put a higher priority on clustering engines in order to achieve greater ranges before moving on to the Shahab-3? Many of my friends believe they should have. A large portion of their argument is centered on the fact that they believe Iran would have established a missile capable of hitting Israel much sooner if they had done that, perhaps as early as the mid-1990s. Of course, such arguments place an extraordinary amount of emphasis on such a military objective, especially when Iran’s nuclear program was much, much less advanced.

I’ve always thought, however, that Iran did make a strategic decision about the direction its missile development program was going in. But it was not a military-strategic decision but an industrial-strategic decision even if there were military advantages to be had further down the road. I believe Iran decided they needed to assimilate the technology for producing large engines indigenously and that this was a much higher priority for them than early production of a longer range missile. New images released at the same time as the “Kavoshgar-3” sounding rocket (with its animal passengers) was launched. Two amazingly important images were released:

A new, large, two-stage rocket with the Iranian space agency logos on it. The second stage appears to be the same stage (and nose fairing) as the Safir’s second stage.

Assuming that the smaller diameter second stage is the same as the Safir’s second stage (with a diameter of 1.25 meters), then the much larger first stage is consistent with a diameter of 1.95 meters. That is, of course, considerably smaller than twice the Shahab-3’s diameter of 2 times 1.25 (or 2.5) meters. So it is fair to ask “What can you put in there?” I think the answer is a cluster of four “Nodong engines.” And, voila, the Iranians show a new rocket power plant with a cluster of four Nodong engines at the same gathering where Pres. Ahmadinejad watched the Kavoshgar-3 launch:

An Iranian rocket scientist unveils the new cluster of four Nodong engines, known as the Phoenix (if Google translate is working properly). The yellow struts above the engines are for transmitting the thrust to the rocket’s airframe. Their presence implies that the first stage will use jet vanes for thrust vector control.

Phoenix, the name of the new power plant, is an interesting name. I’m not sure what the Iranian mythological implications are but as a Westerner, to me it means rebirth in fire. Perhaps they are implying the rebirth of this engine design in a new form. Of course, it is always dangerous to use one cultural point of view to analyze another culture’s literary allusions.

The yellow struts rising above the engine cluster (and their multiple turbopumps, perhaps four? one for each engine?) are for fastening the power plant to the rocket body and for transmitting the thrust they develop. They are angled slightly outward for increased structural strength. Pads at the top of the struts are the connections with corresponding strong points inside the first stage. But is the first stage wide enough to accommodate this cluster?

To answer that question, I have had to go through a chain of photo-interpretation; each of which undoubtedly contributes a certain amount of uncertainty or error to the final answer. First, I had to determine the diameter of the Nodong engine. (I know these are Shahab-3 engines, but I am so used to calling them Nodongs, it would be too painful to switch. Let it be known that I think these engines are indigenously produced in Iran, though Iran probably bought or licensed the production line for them from North Korea.) I get a diameter for the combustion chamber, just below the strong points for the struts, of 0.57 m.

Then, transfer this diameter to the image of the Phoenix power plant:

The top of the Phoenix power plant, showing the combustion chambers and the full diameter of the struts. Calculations by the author indicate that this cluster of four engines would certainly fit inside the large rocket body shown above.

Using this combustion chamber diameter as a reference point on length, I get a total separation between opposite pads at the top of the struts of 1.87 meters. Of course, a rather long chain of analyses was needed to estimate this length. And even the assumption that the farthest right strut pad and the farthest left strut pad represent the full diameter of the support system introduces a certain amount of uncertainty (though that is reduced by a cosine theta effect). Nevertheless, this is remarkably close to my estimate for the diameter of the new rocket’s first stage. Close enough to convince me that this is the new first stage’s power plant.

Note that there are at least superficial differences between this rocket’s first stage and the DPRK’s U’nha-2’s first stage. If nothing else, Iran has designed the airframe itself. (I am being extra cautious about this, my own feeling is that Iran has designed the entire first stage itself. But that is such a key step in my understanding of Iran’s missile development trajectory, that I am hesitant to state it as a conclusion.)

So what do I think has happened? First, Iran purchased a production line for Nodong engines (and the other components of the Shahab-3 missile) from North Korea. However, though the years of producing them, flight testing Shahabs, and modifying them with the design and production of the Safir and other rockets, Iran has fully assimilated this technology and they are moving on to the next stage of development—clustering large engines (they obviously gained some highly important experience with the cluster of two engines on the Safir’s second stage)— and they are probably doing this largely on their own.

Note: a future post will estimate the range of this missile using the “hypothesis” developed here.

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These two views show a target warhead 350 km directly above the Jiuquan Satellite Launch Center at 7:45 pm (local time) on 11 January 2010. The image on the left shows what the target warhead (with an altitude of 350 km) would see if it looks at the Sun and the right shows the geometry of the Sun, Earth, and target warhead at at that instant.

I am starting to conclude that the “eyewitness” to the Chinese missile defense test is probably real, the reported time (7:45 pm, “local time”) is reasonable, and the target vehicle was most likely a relatively short range missile such as the DF-21. The slower the target vehicle, the more reasonable the streak seen on the camera phone’s image becomes. One very important question can still be addressed: was the target illuminated by the Sun? The answer to this question is vastly important. If the target could not be illuminated by the sun, it would mean that the Chinese have developed much more sophisticated infrared sensors than they have flown previously. If, on the other hand, it could be illuminated by the sun, perhaps by selecting an intercept point high enough for the sun to illuminate the target, then we are not forced to conclude a dramatic improvement in IR technology.

7:45 pm sounds pretty late at night. (Especially during the winter!) However, we must not forget that China is a very large country that uses a single time zone. That means that when it is 7:45 pm in Beijing, it is also 7:45 pm local time at the Jiuquan Satellite Launch Center almost 1,400 km west. On 11 January 2010, that corresponded to11:45 UTC. How high up would the target have to be to still be illuminated by the Sun?

At that time, the Sun was 17.4 degrees below the horizon at Jiuquan SLC. It’s a simple exercise in geometry to show that an object needs to be at an altitude of 305 km or greater if it is to be illuminated by the Sun. That is easily achievable by a DF-21 flying a maximum range trajectory.

I suppose that some people will still want to believe that China has achieved a quantum leap in IR technology. I cannot prove them wrong. However, I believe that such improvements come in systematic ways; especially if the developing country wants to master the technology for the long term. This test is still consistent with the Chinese hit-to-kill technology using a visible light tracker.

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I’ve been working on a rather long piece about the recent Chinese Ballistic Missile Defense test but persistent reports of an eyewitness (complete with photos) have sidetracked me. These reports purport to be from a Chinese citizen who appears to have witnessed multiple flashes/explosions. (The original English translation seems to have disappeared, luckily I printed it out to pdf, which can be viewed here.) The question is: are these credible reports/photos?

For the moment, let us assume the photograph is associated with the interception. What could it be? My guess is that it is not the initial interception. The eyewitness seems to have watched a number of phenomena in the sky before taking out his cell phone and taking a picture. (That is certainly believable. In fact, it would be too incredible a coincidence for him to capture the interception.) Also, the first things he witnessed do not appear to have been the plume from the interceptor rocket. He certainly would have reported an initial streak of light if that had been the case rather than “moons” appearing.

Instead, the image above could be a large fragment from the target burning up in the atmosphere as it reenters. Using a typical camera phone field of view of 50 degrees implies that the streak is about 1 arc second long. If it originates at about 50 km altitude—somewhere around the altitude where the atmosphere starts to get fairly dense—then that corresponds to about 0.8 km long. Of course, it has been foreshortened by some unknown amount.

For the moment, and for the sake of continuing to speculate, let us assume there is no foreshortening. We might expect a target velocity (depending on the unknown range of the target rocket) to be somewhere between 3 and 6 km/s. With no foreshortening, that implies a “shutter” time of between 0.15 to 0.3 seconds. (Shorter range target rockets would imply longer shutter times.) I’m not an expert on cell phone cameras, but that seems to be somewhat longer than I would expect possible. (Readers?) The inevitable foreshortening would lengthen that shutter time still further and assuming a higher altitude would imply an even longer shutter time. These same arguments rule out this being an image of the initial interception. So the credibility question comes down to: how long does a cell phone camera integrate over a scene at night?

There is still some wiggle room here. I need to try to calculate where in its trajectory (ie what altitude) a piece of debris would become visible but my initial reaction— subject to a lot of further work —is that this is not directly associated with the interception. It is still possible that it is a piece of debris burning up.

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The most recent satellite reported to be joining China’s constellation of Beidou navigation satellites is shown in yellow. An example of a geostationary Beidou satellite is shown in white and China’s one and only navigation satellite in a medium Earth orbit (MEO) is shown in green.

The launch of what is reported to be a seventh Chinese navigation satellite (on 16 January 2010) provides an opportunity to review what we know about this system of satellites. First, it is clear that the satellite, which has yet not been officially designated a Beidou satellite on the NASA space-track website (at least as of 12 noon, 18 January 2010), is intended to be a geostationary satellite. It, and the third stage of the CZ-3 launch vehicle, are in a geostationary transfer orbit (GTO), as the image above shows. Within a few days of launch, the satellite’s apogee motor will fire, positioning the satellite in to its final orbital.

If the case of Beidou 1D is any indication, we will not know which satellite it is replacing until China moves it into position. China, as a responsible spacefaring nation, moved Beidou 1D into a supersync orbit just days after the launch of its replacement satellite, Beidou G-2. Beidou 1D as only about two years old when China replaced it with what is reported to be a second generation Beidou satellite. That is somewhat surprising since Beidou 1 was over six years old at the time and one might have expected it to be replaced before the much younger 1D. If China decided to replace 1D because it was failing, they must have had plenty of warning since they were still in control of that satellite.

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Current Beidou Constellation is shown (at the top) with the ground tracks for three orbits for each satellite projected onto the Earth’s surface; (lower left) an equatorial view of the satellites; (lower right) a polar view of the constellation. Note the Beidou 1D’s ground track shows both a large longitudinal displacement over three days and a large inclination—the up and down motion of the ground track. Dates indicated are the launch date of each satellite.

China’s first generation of navigational satellites did not have an onboard atomic clock. That, of course, complicated their operation and limited the number of users. Instead of broadcasting their own timing, as GPS satellites do, the satellite operated as a “bend in a pipe” with the time standard generated on Earth and, in fact, the “user” position determined by a central location after a round trip of radio signals from the center to the satellite to the user and back. It would be very interesting to know if the second generation satellites had their own space qualified atomic clocks.

With this latest satellite, we are also starting to see a pattern in Beidou launches. About every three years (2000, 2003, 2007, 2009*, 2010) a new wave of satellites is plugged into the constellation. (The asterisk for 2009 indicates that this launch might well have been accelerated to replace a dying satellite.) That might indicate the length of time it takes to design and/or build a new satellite. If it includes design time, I would expect evolutionary changes; something we might expect from China in any case given their known history of systematic development.

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Quite a few of my friends have been urging me to write something about the “new” images of Iran’s space center that have shown up recently on Google Earth.

The trouble is, I hate rehashing stuff I wrote about almost two years ago when I “discovered” the facility—much like Columbus “discovered” America—and wrote about it in Jane’s Intelligence Review (see Geoffrey Forden, “Smoke and Mirrors: Analyzing the Iranian missile test”, JIR, April 2008, pp. 47-51; I have never understood how the editors pick titles for my papers).

Perhaps the most interesting part of the imagery now, given the connection between these two countries’ missile programs, is the similarity between a building at North Korea’s launch site and one at Iran’s. For those who would like to examine the site themselves, let me replicate the coordinates I published in the open literature for the first time nearly two years ago:

35.234440° N, 53.920798°E.

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Slide from a talk I gave on Capital Hill (sponsored by the AAAS) in March 2008.

Media reports today indicate that China has tested “ground-based midcourse missile interception technology.” Details necessary for evaluating exactly what system has been tested have not emerged yet. Nevertheless, it bolsters a prediction I made soon after the 2007 ASAT test: that China would continue testing its hit-to-kill technology in the form of a missile defense system. After all, there is no functional difference between an ASAT and a missile defense system; the closing speed is the only important parameter for classifying any exoatmospheric interceptor.

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Iran is justifiably proud of its satellite launch last February. After all, both North and South Korea failed in their satellite attempts in that same year. It appears from images that are starting to show up on the web—pointed out to me by the ever observant Wonk-Reader Tal Inbar—that they have taken the show given to President Ahmadinejad at the Iranian Space Center on the road. These images show new and revealing details of both the Safir/Omid system and some indication of the quality of workmanship that goes into it. The image above is another image of the back of the Safir’s second stage engine platform showing more about how the turbopump is enclosed. Compare it to the image shown here, which shows more of the turbopump. The very frail looking “flaps” are light-weight baffles to prevent the fuel from sloshing about particularly during staging. Other images show what appear to be drain holes to the fuel tanks, a new telemetry dish antenna, and several nice views of the first stage engine (and are those indigenously produced components laid out on little pedestals?) Any help translating the Farsi on any and all these images would be gratefully appreciated!

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As this penultimate year of the decade draws to a close, our thoughts naturally turn to all the changes we have seen. (Don’t ask me why this year and not next, there is just something special I suppose about seeing that tens digit change.) One thing that strikes me is all the convincing proof we had this year about the spread of sensors around the world. Sensors are becoming ubiquitous!

Nothing makes this clearer than the launch of the U’nha-2, North Korea’s third attempt to put a satellite into orbit. Not only did a high resolution photo-imaging satellite catch the actual launch, but it turns out that a vast array of GPS sensors spread over Japan sensed its passage through the upper atmosphere. I’m sure Wonk-readers can think of other examples that illustrate the spread of sensors around the world. (My favorite example involves Iraq, but I can’t really talk about that.)

But if the world has access to more and more sensors, it’s not clear we have the capability of analyzing all of the data. (I don’t mean the sort of brilliance Kosuke Heki, a geodesy specialist at Hokkaido University, displayed in analyzing the change in GPS signals the U’nha-2’s passage caused. That sort of creativity cannot be counted on as standard operating procedure.) It’s a lot like sitting down in front of Google Earth and simply scanning the Earth’s surface, looking for something interesting. You quickly find out you need to be clued into where to look. Dealing with this data overload will be the challenge for the next decade; when it starts in 2011.

Note: The figure above shows the dense GPS array with annual crustal strains.

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This is the second in a series of preparatory posts leading up to a discussion on the Safir’s guidance system. The first discussed the orientation of the Safir at launch and showed, as closely as the errors associated with photo-interpretation would allow, that it’s first stage guidance and control system was a standard SCUD-type system: Fin I is oriented along the direction of flight of the missile and its pitch program operates in that plane.

This short blog post discusses the ground terminal trucks Iran used to communicate with the satellite. Iran, in accordance with the “rules of the road” organized by the International Telecommunications Union (ITU), had an uplink (401 MHz) and a downlink (465 MHz) frequency for the Omid satellite recorded in the ITU-R’s Master Registry. Various computer animations of the launch show mobile ground stations positioned around Iran for communicating with the satellite and it would be nice to confirm that images taken of ground station trucks are used for that purpose. It also turns out to be a very satisfying exercise in photo-interpretation. A future post will discuss communications for guidance purposes, as was implied in the secret missile memos.

As the image above—taken during a visit to the Iranian Space Center by President Ahmadinejad—shows, there are trucks with potentially suitable antennas. The dual antennas are of a Yagi-Uda design (often simply called a Yagi antenna) with 12 passive “directors,” a looped Balun-type element for radiating the signal and, at the very rear of the array, a somewhat larger “reflector.” The reflector is to ensure that there is a preferred direction to the antenna as opposed to being sensitive to signals from both directions along the boom. The Balun radiator matches the impedance from the simple coaxial cable to the array and the directors increase the “gain” or directionality of the antenna. Interestingly, there are both vertical and horizontal arrays on each boom with the horizontal array set back a quarter wavelength (see below), perfectly suited for detecting or radiating circularly polarized radio waves. That is needed because the Omid satellite tumbles as it orbits and its polarization—while not circular—is directed in an arbitrary, time varying manner. The bulky cable run up to the antenna hub is for controlling the direction of the antenna arrays and could, though there is no way to know from the photo, be capable of autonomous direction if it is set to maximize the strength of the signal.

Yagi antennas are nice from a photo-interpretation point of view because their dimensions are so easily related to their wavelength. For instance, an optimal 13 element (counting the radiator but not the reflector) Yagi for 401 MHz has a boom length of 2.7 meters. That’s from reflector to last director. It also has a reasonable antenna gain, which means that half the uplink beam is radiated into a cone with a half angle of about 16 degrees. The question then becomes: is the observed array consistent with these expectations?

The image to the left is taken from a more suitable perspective for photo-interpretation. The antenna arrays are nearly horizontal and close to being aligned with the rear of the truck. I have drawn two vertical lines continuing up the truck’s rear edges and a third, horizontal, line paralleling the antenna booms. Of course, there are a great number of approximations taken in this drawing. But then again, there are some approximations still to come. The most important of those is to assume that the truck’s rear cabin is approximately two meters in width. With that assumption, we can estimate the boom length to be approximately 2.9 meters long (from radiator to last director). This is consistent with the Omid satellite’s uplink frequency given all the approximations we have made. Either the far antenna in the image is shorter than this (if it is used for the downlink) or they are running the antennas nonoptimally for reception or there is a different receiver somewhere not on the truck.

What I find most interesting is the conclusion that if there are antennas on the Safir that have significantly different lengths than the Omid’s, then these trucks are not being used to communicate with them.

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This video is just a little more interesting than watching paint dry—until you realize that it is sound causing that little bright dot in the center! Sonoluminescence, light emitted by a plasma created at the center of a converging spherical sound wave, can be yours for about $100. Here are the instructions and here is a Scientific American article on the phenomena, which is closely related to the UD3 neutron generator.

I’ve been thinking about a small detail involving UD3 imitators ever since Jeffrey first published his very interesting post showing A. Q. Khan in front of a blackboard detailing Pakistan’s bomb design: why uranium deuteride? The uranium doesn’t participate in the nuclear aspects of the neutron generation, so why use it? I’m still not convinced I’ve understood the reasons behind this choice of material but the process of trying to understand it has been very enlightening.

Of course, one answer might be purely practical: there’s a whole bunch of uranium sitting in a bomb not doing anything until the first burst of neutrons is generated. Why not use it in the initiator? Such practical considerations undoubtedly do play an important role. But uranium has a very nice property that deuterium gas, for instance, does not: it’s very massive, an important consideration for shock compression. That mass, and how it’s packaged, might play a critical role in generating the pressure spike that compresses and heats up the deuterium to the 12 million degrees as reported in the Chinese paper.

What potential benefits does that mass bring to the initiator? The internal energy caused by the shock of the collision at the center of the device is proportional to the density of the material. Not the density of deuterium alone, but the total mass density. And the change in internal energy is also proportional to the shock pressure associated with this collision, which is much, much more intense than the shockwave that propagated through the UD3 to get it accelerating toward the center.

I’ve been trying to guess how fast that initial shock velocity was; another thing the Chinese paper—by not fully describing their experimental set up (they only give the outer radius of the high explosive as 8 cm)—has managed to conceal. I’ve estimated it as between 7 and 17 km/s, depending on how big the air gap between the aluminum and steel liner and the core really is. (The particle velocity is less than that.) One possible measure of just how important the uranium mass is comes from the paper reviewing Kaliski’s experiments using D2 gas, as pointed to by Robert Cross in Jeffrey’s original post. Through a fairly complex apparatus for focusing the shockwaves from a shaped charge (complicated if you wanted to place it next to a nuclear weapon’s pit, that is), Kaliski reported a particle velocity striking the deuterium gas of 50 km/s. Needless to say, the smaller the required velocity of the “strike,” the easier it should be to cause fusion.

But It’s More Than Just the Mass

Of course, just because deuterium is bonded to uranium doesn’t mean the compound has a high density. The theoretically maximum density of UD3 is about 11 g/cc; still quite dense if considerably less than the 19 g/cc for uranium metal. But that 11 g/cc is for a monolithic crystal. This is where material engineering really comes into play. You can increase the shock pressure—a seemingly important factor for increasing the final temperature—by increasing the density of the material. But you can also increase the temperature by making it more porous. In the language of shockwaves, you are increasing the change in “specific volume” (which is just the inverse of the density) as the material is crushed by the shock. This crushing, or compression, performs work on the material and heats it up. (That’s why the sonoluminescence experiment mentioned above needs a bubble in the center.) A monolithic crystal of UD3 would have a high pressure associated with the collision but not much work would be done—because of the relatively small compression associated with the solid crystal—and hence would not produce much of an increase in temperature. The Chinese, on the other hand, used a material with an initial density of 6 g/cm^3, which I assume is in the form of a sintered powder.

The effects of increasing the porosity of a material has been well documented in the open literature. Furthermore, increases in temperature appear to increase with increasing density of the porous metal’s “parent material” (bulk copper, for instance, is the parent material of copper powder). But most reproducible results involve temperature changes less than 10,000 K; about a factor a thousand less than the Chinese report. Of course, it is possible that the results mentioned in the literature were based on bulk temperatures and the fusion-type environments only happen over a very small volume that can only be measured by looking for the fusion-induced neutrons. (Just to be clear, I’m purposely grasping at straws here.) On the other hand, the Chinese measured a maximum of 48 neutrons in their detector and “corrected” that value by a whopping big factor to infer a yield of 50 thousand neutrons. To make maters worse, I saw nothing in the Chinese paper to indicate that they measured the effects of setting off 252 high speed detonators close to the sensitive preamps attached to their barium fluoride proportional counters. That might cause a lot of ringing in the signals.

Figure from the Chinese paper. After reading their caption, try saying “preamp noise” to see how that fits. (The darker black areas are in the original article.)

At the end of this process, I still don’t know why it is uranium deuteride. Can such high density materials like uranium be used to provide exactly the right balance between the two countervailing needs: high shock pressure and crushability? Or is UD3 a red herring and that famous (or infamous?) blackboard photograph an instance of carefully constructed of misdirection? As you might have guessed, I’ve become increasingly skeptical about the possibility of using UD3 as a source of fusion neutrons initiated by conventional explosives.

Note on Proliferation: I’ve tried mightily to extract the UD3 shock Hugeniot from the Chinese paper and haven’t figured out a way of doing it. Through a carefully selected set of information actually published, I think the Chinese have managed to convey their results without creating a proliferation problem since that Hugeniot is really what you need to design an initiator. However, just because I can’t do it doesn’t mean it is impossible so I agree with Jeffery’s decision not publish the paper here. This, of course, just propagates the problems arising from censoring science: a lack of full peer review etc.

I’d like to thank Prof. Andrew Higgins for pointing me to a number of important papers in the literature and helpful pointers as I tried to understand this issue. I highly recommend one of Andrew’s suggestions: Paul Cooper’s “Explosive Engineering” Of course, any mistakes I’ve made here are entirely mine.

Appendix: Hugoniots “Explained”

Once again, it has been pointed out to me that I’m way too techno-wonky on this one and failed to explain what a Hugoniot is. Of course, the best way to learn about them would be to read chapters 14 through 17 from Explosives Engineering. (Don’t worry, the book is excellent and you can jump in right to those chapters, which give a very readable physical explanation of shock waves. They get progressively more “mathy” but its all algebra and I urge you to work through them. If you don’t feel like that, just read Chapter 14, which doesn’t use any math at all.) But for the skinny, let me say that a material’s response to shocks can be characterized almost entirely by one graph and that graph can, for most materials, be characterized by a single number. The graph is a plot of the shock velocity vs. the velocity of the particle and the single number is the slope of that line in what is, in most cases, a straight line. This is called the U-u Hugoniot and other Hugoniots associated with the material are simply derived from it.

As you might expect, a shock wave, which is just a pressure wave has a higher velocity that the particles that get accelerated by the shock as it pass over them. But once the these parameters have been determined, it can be used to plot the same Hugoniot line but in terms of different variables, all of which are related to the original line by the laws of physics. In particular, you can plot the pressure of the shock wave verse the “specific volume,” the inverse of the density. This plot is important because the area under a line drawn from the initial, unshocked state, to the state after the shock wave has passed through is equal to the internal energy of the material. In our case here, by increasing the porosity of the material, we have increased the area under the graph and hence the total internal energy. A word of warning: the temperature is different from the total internal energy.

An example of a typical Hugoniot where pressure is plotted against specific volume (i.e. the inverse of density). The area under the Raleigh line is equal to the shock induced internal energy (including potential energy stored in chemical bonds of compressed materials.)

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