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Entering the North Korean re-entry debate

It's likely there was indeed no successful re-entry on the North Korean test, but that should not be immediately interpreted as a setback for the program.

Entering the North Korean re-entry debate
Published 12 Jul 2017 

South Korean intelligence claims that the recent test of a North Korean ICBM possibly failed to produce a successful warhead re-entry.

The statement from Yi Wan-young (a member of the South Korean parliament’s intelligence committee) seems intended to soothe concerns over the potential for North Korea to launch missile strikes against the US and other distant nations. It is highly probable there was indeed no successful re-entry on this flight, but that should not be immediately interpreted as a setback for the program – North Korea has successfully tested re-entry technology on previous missile launches, effectively proving that a warhead can survive the plunge to its target. It is thus possible that North Korea did not actually install a proper re-entry vehicle on this ICBM test, choosing instead to focus on the performance of the missile itself.

Dropping hardware into the ocean is risky. Many nations have the capability to inspect or retrieve items from the seabed, but these capabilities are not generally discussed. Neither are their covert missions. Ostensibly innocent programs such as deep-sea vessels designed to rescue crews from stricken submarines or marine science vessels can be used for other purposes. In the Asia Pacific region, such advanced submarines are fielded by Russia, China, Japan and South Korea. The real leader in such activities is the US, which has been carrying out these missions for decades. The most ambitious US sea grab was the legendary Glomar Explorer mission, where a ship was specifically and secretly built with the intention of lifting an entire Soviet submarine (broken into three segments) from the seabed for inspection in 1974. Modern missions involve remotely operated vehicles as well as advanced crewed submarines.

Getting hold of a DPRK re-entry vehicle would be a Golden Fleece for any military intelligence service. The dimensions of the vehicle would give clues to the size and design of the nuclear package inside. The materials used on the thermal protection system (heatshield) would also be relevant, as sensors could be trained to look for their spectrographic signatures. This could help to distinguish a real warhead from decoys.

North Korea has sometimes installed self-destruction systems on its satellite launch vehicles to prevent the retrieval of rocket stages. In theory, a small conventional explosive could be placed on a re-entry vehicle, but it is possibly not as practical. What if a pre-programmed system fails to detonate on schedule, or detonates prematurely? Sending a radio self-destruct command could be tricky at long range. Installing a self-destruct system could also compromise the design and mass distribution of the re-entry vehicle, thus reducing its fidelity as a test of a nuclear delivery system.

Questions over the design and performance of this new missile are flooding the boffin universe. It will take time before we really understand it all

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