Figure 3. The Unha-3, inside the gantry at Sohae, comes up to only the fourth set of work platforms.
Sohae's mobile launch pad provides another clue about the physical dimensions of the new North Korean rocket. The commercial satellite photograph in figure 4 shows this platform in 2008, while it was being assembled, with a four-meter hole in its center. Next to the mobile launch pad, however, there is a plug that reduces the hole to just 2.5 meters, enabling the stand to hold the Unha-3 rocket. But the plug can be removed to accommodate a larger rocket, like the one presumably planned.
Other clues can be found at the new launch site. Commercial satellite photography from 2006, when Sohae was still under construction, show that the number and size of storage tanks inside the large buildings near the launch pad that are used to store Unha-3's first-stage propellants greatly exceeded what would be needed to fuel the rocket for this week's launch. In other words, the tanks appear to have been built for a larger rocket. The same is true for the rocket engine test stand at Sohae, which is designed to fire larger, higher energy engines than the facility at the old Tonghae site, where the smaller Unha engines were tested.
Figure 4. Mobile launch stand and its plug under construction.
Pictures recently seen on display at the Three Revolutions Museum's space exhibit in Pyongyang may provide another clue to the mysterious rocket's existence and characteristics. Figure 5 shows a photograph of an artist's concept of a large satellite launch vehicle and gantry tower. The rocket and gantry portrayed in this picture differ from the Taepodong 1 launched in 1998 and the Unha rocket tested in 2009 and soon to be launched this week. But is this just another piece of propaganda or a representation of a future large DPRK space launch vehicle?
It's impossible to say for sure. The space exhibit is full of false or misleading claims, including that the two satellites launched during previous tests achieved orbit, which they did not. Another photo shows a Chinese satellite that the North Koreans claim as one of their own. On the other hand, both launch videos and models of earlier rocket tests are accurate.
Figure 5. Artist's concept of a possible larger new North Korean rocket.
Assume for a moment, then, that the photo -- propaganda though it may be -- bares some resemblance to a future large North Korean rocket. The depiction of the confirmed gantry at Sohae doesn't look quite the same, but let's also assume that the dimensions are close. Given our detailed knowledge of the Sohae gantry from commercial satellite imagery, and now ground photos, the rocket in the picture can be roughly scaled to obtain its dimensions: about 38 to 40 meters long and 3.5 to 4 meters in diameter. The dimensions are similar to the large rocket reported by the press, the height of the Sohae gantry, and the diameter of the hole in the mobile test pad.
To carry this analysis one step further, a rocket of this size would be able to comfortably mount inside its first stage nine engines used by the Nodong medium-range missile -- more than twice as many as the Unha-3 first stage. The second stage looks to be 2.5 meters in diameter, similar to the Unha first stage, and could thus mount four engines. The two stages alone would give the next-generation North Korean rocket nearly 450 tons of thrust, much more than the current generation of North Korean rockets and more than enough to power a highly capable ICBM or space-launch vehicle.
Of course, none of the information regarding the image in figure 5 is definitive. And information about North Korea's WMD programs is scarce, even for governments watching Pyongyang closely. But the pieces of this unclassified puzzle -- press reports, commercial satellite pictures of the new test facility, and exhibits from a Pyongyang museum -- allow us to put together a more complete picture of North Korea's new rocket than has been previously available. It also gives us a rare glimpse into Pyongyang's future plans as it moves down the road to becoming a small nuclear power, a development that has major implications for international peace and security.