[Interview] Missile defense systems expert says THAAD could prove useless
Posted on : Feb. 14, 2016 07:37 KSTThe propellant explosion technology seen in N. Korea’s latest rocket launch can render the interceptor unable to identify a potential warhead
Massachusetts Institute of Technology (MIT) emeritus professor Theodore Postol
A expert in missile defense systems said the propellant explosion technology seen in North Korea’s recent long-range rocket launch on Feb. 7 could render useless the Terminal High Altitude Area Defense (THAAD) system South Korea and the US have all but officially decided to deploy on the Korean Peninsula.
Massachusetts Institute of Technology (MIT) emeritus professor Theodore Postol explained the situation in a series of email and telephone interviews with the Hankyoreh in the wake of the launch and the announcement that South Korea and the US have begun official discussions on THAAD deployment.
Postol, who earned a doctorate in physics from MIT and previously served as senior adviser to the US chief of naval operations, is a noted expert in missile defense systems who has explored the area for over 30 years academically and for the US Department of Defense, Argonne National Laboratory, and Congress.
One point Postol particularly noted about North Korea’s recent launch was the first stage’s explosion and separation into hundreds of scattered fragments. Indeed, the South Korean Ministry of National Defense noted on Feb. 9 that Aegis radar showed tracks from some 270 exploded fragments from the first stage.
“The explosion is believed to have been carried out through a self-destruct mechanism to prevent South Korea from collecting the propellant,” the ministry said at the time.
Postol said use of the same self-destruct technology with North Korea's Nodong missile would prevent THAAD radar from identifying an actual warhead. At the moment THAAD launches an interception missile, North Korea could explode its own warhead-carrying missile into multiple fragments.
“Once the rocket completes its powered flight, it is at very high altitude where for all practical purposes there is no air-drag to slow up light objects relative to heavy objects,” Postol observed.
“Thus, if a missile is cut into many pieces after it has completed its powered flight, all of the pieces will float along with its warhead payload on the same general trajectory,” he continued.
“Cutting the missile into many pieces simply makes it possible for an adversary to create many false targets that a distant infrared homing interceptor would not be able to see in any detail.”
In short, an interception missile would be rendered useless because of the large number of more or less identical targets.
“All the interceptor sees are unresolved points of light, any one of which could be the warhead,” Postol explained.
In particular, he noted that “[objects that are elongated and tumbling . . . will appear to change their brightness when they rotate from orientations that present a large projected area to the interceptor relative to orientations that present a small projected area.”
“However, this information is not useful to the sensor because any of the objects, including the warhead, could be tumbling,” he concluded.
Postol went on to note that “this technology could be applied to a North Korean Nodong ballistic missile carrying a nuclear warhead aimed at South Korea.”
Postol was also highly critical of Seoul and Washington’s public claims that THAAD would not pose a threat to China.
“To suggest that the THAAD radar is not capable of the FB [forward-based] mode is the same as suggesting that a tank that can travel 100 km to a destination and then return from that destination . . . is not capable of traveling 200 km to a more distant location,” he said in response to the argument that THAAD radar on the Korean Peninsula could not be used in FB mode.
“It is the right of the South Korean government and people to choose to deploy THAAD in spite of this technical situation, but they should not take this action under the mistaken belief that China will not correctly assess the THAAD radar as a potential danger to its nuclear deterrent forces,” he added.
In closing, Postol noted that he has “extensive experience with general officers at the levels” of USFK Commanding General Eighth Army Maj. Gen. Thomas Vandal and USFK Commander General Curtis Scaparrotti.
“It is very disturbing for me as an American citizen to see two senior US general officers improperly attempting to interfere with the domestic political decision-making in South Korea by stoking unfounded fears about long-range rockets and nuclear weapons developments,” he said.
By Yi Yong-in, Washington correspondent[Analysis] US experts question THAAD's ability to intercept North Korean missiles
Posted on : Jun. 25, 2015 19:00 KST
Free flight locations of ballistic missiles shown at 10 second intervals
THAAD system limited in its ability to differentiate between real missiles and decoys, and to intercept tumbling and spiraling missiles
The US Missile Defense Agency (MDA) has claimed that Terminal High Altitude Aerial Defense (THAAD) interceptors have demonstrated effectiveness against short- and medium-range targets, announcing that in nine flight tests so far, THAAD intercepted all 10 target ballistic missiles.
However, the tests were conducted under circumstances that provide little, if any, information about how the THAAD interceptors would actually perform in real combat. Theodore Postol, a professor at the Massachusetts Institute of Technology (MIT), and George Lewis, a visiting scholar at the Cornell University Institute of Peace and Conflict Studies, have raised questions about the MDA’s performance claims, based on three main factors.
First, North Korean ballistic missiles could fly in irregular and unstable ways on the way to targets. Due to their design, these missiles could well tumble at high altitudes and spiral at lower altitudes, as was observed in the Gulf War of 1991, and almost certainly led to the complete failure of Patriot interceptors to destroy even a single SCUD warhead in combat. Patriot interceptor tests prior to the Gulf War were successful in 17 of 17 tests. In Gulf War combat, the Patriot was almost certainly 0 for 44, defined as destruction of SCUD warheads.
Missiles tumbled in the Gulf War due to random lateral forces from rocket motors as they shut down. The motors shut down at high altitudes where the air was so thin that the fins at the back of the missiles could not prevent the tumbling. In effect, these missiles acted in flight like arrows that had no feathers. When fired from a bow, they simply tumble end over end. The low-altitude spiraling phenomena could be made intentionally by modifying the fins at the backend of missiles. Tumbling at high-altitudes happen intentionally with tiny rocket motors attached to the back of the missile that are fired as soon as the rocket’s main motor shuts down.
In addition, when the missiles reenter the atmosphere, they could be affected by aerodynamic forces. As shown in the case of Al Hussein Scud during 1991 Gulf War, if the warhead is too light to force the missile to maintain a stable orientation, lateral aerodynamic lift forces are generated that cause it to move laterally, tracing out a spiraling trajectory. The two scholars pointed out that a target following a spiraling trajectory is the most difficult target to hit.
According to their analysis, it is estimated that in the case of North Korean Scud B, the THAAD interceptor would have to be launched while the missile is still at an altitude of 60 to 70 km, where the tumbling phenomenon could occur. The spiraling movement could occur at an altitude of 10 to 20 km. In the case of Scud C, if it reenters the atmosphere in a side-on orientation it will likely remain intact until it reaches an altitude of roughly 30 km, where it will break up due to the increase in aerodynamic forces, the two scholars said. If it reenters the atmosphere oriented nose-on relative to its velocity vector, it will disintegrate at about 10 to 12km. Both of these altitudes are below the THAAD minimum intercept altitude, they said.
Events during Al-Husayn(SCUD C) ballistic flight and reentry that caused low-altitude manueuvers and breakups that defeated Patriot.
Secondly, the US missile defense systems including THAAD are limited in their capability to discriminate between the real warheads and decoys. It is because the radars and infrared sensors could tell only the exterior properties of missiles in space such as shape and brightness. Potential enemies could undermine the radars and sensors’ ability to differentiate between the warheads and decoys by conducting countermeasures including cutting a missile into many pieces using explosive cutting cords. The explosive cutting cord, which is a piece of rope manufactured from strands of high explosives, could intentionally cut the missiles into tens of fragments. If the shape of these fragments is similar to the real warheads, it is difficult to determine which one is the real warhead.
These fundamental constraints could be applied when the THAAD intercepts the Nodong missiles. Since THAAD interceptor would have to be launched while the complex of incoming objects is at an altitude of 105 km or higher, the effects of the atmosphere causing the lighter objects to slow up will be minimal, two scholars said. Hence, when the THAAD interceptor needs to be launched, there will be no way for the THAAD system to determine which of the many incoming objects would be the warhead, they said.
Proponents of missile defense systems believe that they could succeed in discriminating between the warheads and decoys by conducting more research and development in the future. However, Dr. Postol argued, “Research aimed at exploiting physical phenomena that do not exist can never produce anything but nonsense.” He said, “In effect, radars and infrared sensors see the exterior properties of objects in space. Those exterior properties can easily be manipulated so that it is fundamentally impossible to know what is beneath the exterior.”
Patriot intercept where damaged Lance-target continues to fall to the ground with its indamaged warhead
Thirdly, if the THAAD systems succeed to intercept the North Korean missiles, it must hit and destroy the front end of target-missiles exactly. However, it would be daunting challenge. The THAAD interceptor would have difficulty in homing on the part of warhead at the front of missile. For instance, in the test of SM-3 took place on July 30, 2009, the infrared sensor failed to determine where the warhead is, even two seconds prior to impact.
Postol highlighted an important difference between destroying attacking aircraft and attacking missiles. He said, “Anywhere an antiaircraft interceptor hits an airplane will likely result in either the destruction of the airplane and loss of its pilot or the inability of the aircraft to complete its mission. This means that relatively low levels of damaging against an aircraft will result in a successful outcome for the antiaircraft defense. In contrast, a ballistic missile can be heavily damaged and still succeed in its mission - delivering a warhead into the area under attack.”
He also warned, “Nuclear warheads that fly on ballistic missiles are by design very rugged. If the THAAD interceptor were to hit any part of the incoming Nodong other than the front end, the warhead could be expected to fall to the ground and detonate.”
Two scholars pointed out that most of Patriot missiles failed to hit the warhead of Iraqi Scud missiles during the Gulf War of 1991 and also SM-3 succeeded in hitting the warhead only one to two times of ten tests that they analyzed in 2009, all of which were done under exactly the same intercept conditions. The analysis on the intercept tests of THAAD is not available because their detailed results were not disclosed to the public.
The point is that North Korea is capable of developing countermeasures to avoid the THAAD interceptors. The two scholars argued that North Koreas has it well within their ability to make such countermeasures as tumbling and cutting into fragments. In particular, the technology of explosive cutting cord was demonstrated when they launched both the Taepodong-1 and the Taepodong-2 long-range ballistic missiles.
But most high-level decision-makers in the US and South Korea are not familiar with the technological details of these systems.
By Park Hyun, Washington correspondent