The press has again been running hot recently over stories that North Korea is about to launch, or attempt to launch, another rocket.
It brings to mind the run-up to the 70th anniversary of the Workers’ Party of Korean in October, when an allegedly imminent satellite launch was widely bracketed with a nuclear test and described as a “threat”; thus the Korea Times (“South vows stern action against NK threats”) and the Hankyoreh (North Korea sounding off with missile and nuclear threats). The Chosun Ilbo was particularly agitated by the prospect of what it described as a test of a ‘long-range missile’ and warned of “dire consequences.”
However, the South’s ire was never put into the context of the South being miffed that the North beat it (just) in the race to launch a satellite. Moreover, the North did it on an entirely Korean-made rocket whereas the South’s was basically Russian – with two South Korean stages sitting atop the Russian first stage booster which provided the grunt. South Korea’s three other satellites, including the last, which went up March 26, 2015, are entirely launched by the Russian on a commercial basis.
What gets the press acreage is the confusion, sometimes through ignorance but often surely deliberate, between a rocket that launches a satellite … and one which is designed to deliver a missile
However, the North-South competition is seldom mentioned. What gets the press acreage is the confusion, sometimes through ignorance but often surely deliberate, between a rocket that launches a satellite, usually known as a space launch vehicle (SLV), or a carrier rocket, and one which is designed to deliver a missile. A little elementary physics clarifies the situation.
IT IS ROCKET SCIENCE
A rocket is basically a tube in which fuel is burnt. The resulting expanding gas is expelled through a nozzle and the rocket, demonstrating Newton’s Third Law – action and reaction are equal and opposite – is propelled in the other direction. Rockets, unlike jets for instance, burn their fuel quickly so what we have is an initial thrust, followed for the rest of their journey by an unpowered cruise. Because fuel is heavy bigger rockets are usually multi-stage, three being the usual configuration. As a stage uses up its fuel it is separated and the rest of the rocket, now lighter, goes on its way. However, rockets have to contend with gravity and the resultant trajectory is called a ballistic one, after the Roman device for hurling rocks at the walls of enemy cities, the Ballista.
Rockets, of course, are not alone in describing a ballistic trajectory. The famous Australian sport of throwing stones at crows illustrates the same physics. If you have thrown a stone, at a crow or anything else for that matter, you will know that the harder you throw (the bigger the initial thrust) the further it will go. But you also have to throw it high to get it to go a long way. In other words, on a ballistic trajectory. Even rifle bullets which are light and go much faster have to fight gravity and so follow a ballistic trajectory, although a much flattened one. If the final stage of a ballistic rocket achieves sufficient velocity its centrifugal force balances gravity and it goes into orbit around the Earth. If it goes faster than that it escapes the Earth’s gravitational pull and goes off into space, to the Moon, to Pluto, or wherever.
All satellites are launched by ballistic rockets so the UN resolution condemning North Korea for launching a satellite on the grounds that it used ballistic rocket was a pretty outrageous violation of the UN Charter. Politics not physics. But ballistic rockets can be used to deliver a warhead, most likely a nuclear one, and in this configuration are called missiles. In case you were wondering, there is no law against missiles, so the UNSC was not innocently confused. It was a matter of power politics not international law though it masqueraded as such.
Back to the physics.
A Space Launch Vehicle is not a missile, though they both utilize ballistic rockets. And expertise in one suggests that the other is not out of reach. Nevertheless, there are considerable differences between the two. When an SLV has put a satellite in orbit its job is finished and if falls back to Earth, usually burning up in the process. A missile, on the other hand, goes up then it goes down, landing if things go according to plan, on a designated target. It thus requires a different guidance system. It also requires a heat shield so that it does not burn-up on reentry. And finally it requires a warhead that is light enough to be to be carried, robust enough to survive take-off and reentry, and packs sufficient punch to make it worthwhile. The first nuclear bombs were large and heavy and miniaturization has been a crucial part of developing ICBMs.
While an SLV is clearly not a missile journalists often mix up the two. Not merely journalists, though. The Leap Day Agreement between the US and the DPRK reached on February 29, 2012 announced by Victoria Nuland, then State Department spokesperson but famed subsequently as the woman who brought us the Ukraine crisis, contained the phrase “the DPRK has agreed to implement a moratorium on long-range missile launches.” The DPRK subsequently attempted to launch a satellite and the U.S. cried foul, claiming that this violated the agreement. The Koreans, quite correctly, pointed out that it did not – “The launch of the working satellite is an issue fundamentally different from that of a long-range missile,” and added, “More than 100 space vehicles are put into the orbit around the earth by carrier rockets in a year on an average worldwide.” It is curious that the Americans who pride themselves on being punctilious about legal language would confuse the terms in such a cavalier manner. Or perhaps not so curious. According to the Korea Herald there were reports that the North Koreans had informed the Americans the previous year of their plans to launch a satellite (which was on the cards anyway given previous attempts, and the ongoing competition with the South to be the first to get into space) so perhaps the Agreement was designed to fail.
THREAT TO WHOM?
… if North Korea did convert its SLVs into ICBMs then this would demonstrate capability in missile technology, but would not pose any direct threat to South Korea
The current brouhaha also has some curious aspects. It may come as no surprise that the only country to which this confusion between satellite and missile applies is North Korea. Significantly Japan’s SLVs are never described as ICBMs in disguise although Japan, with many satellites in orbit and advanced rockets could quickly translate its civilian nuclear and rocket resources into formidable military assets once the political decision is taken to unshackle itself further from its ‘Peace Constitution.”
Furthermore, if North Korea did convert its SLVs into ICBMs then this would demonstrate capability in missile technology, but would not pose any direct threat to South Korea. Back to crows. If you are only able to throw at an angle of 60 degrees or above, then you cannot throw a stone at the crow at your feet. You cannot lob an ICBM into the country next door. South Korea’s latest long-range missile, on the other hand, cannot launch a satellite but can deliver a warhead to the furthest reaches of the North (and into China).
Whilst SLVs can be converted into ICBMs, though historically it has usually been the other way round, some are more suitable for the purpose than others. North Korea’s Unha-3 seems eminently unsuitable. It is liquid-fueled which is more efficient in terms of payload but makes it very vulnerable during the fuelling process. Solid fuel is by far the preferred option for missiles. And for Japan’s SLVs. Furthermore, Western expert analysis of the Unha-3 suggests that it is specifically configured as a satellite carrier and that “reports that the launch was really a ballistic missile test parading as a satellite launch are not true.” Although it could be converted ‘North Korea would find it difficult to build an operational ICBM founded on the Unha-3 technology.” John Schilling, in 38 North, concludes that “The Unha-3, by comparison (to the KN-08 missile], looks like it was designed to launch satellites rather than warheads.”
Everyone is so fixated on North Korea’s SLV being a de facto missile that it is never asked why they should want satellites. The answer would seem to be that they have the same needs as other countries. All those satellites in orbit perform a range of useful functions – communication, GPS, surveillance – that no country can afford to disregard. Even tiny Laos wants one. In this case surveillance probably tops the list, both for civilian purposes and military ones. It must be very frustrating, and frightening, for the generals in Pyongyang to know that the enemy can see what they are up to, but they can’t reciprocate.
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