North Korea is capable of hitting the US naval base in Yokosuka, Japan, with its short-range ‘Scud’-derived missiles, multiple sources in the South Korean military were quoted as saying by the JoongAng Ilbo newspaper on 28 June.
“We previously assumed the ‘Scud-ER’, a modified version of the ‘Scud C’, could fly about 700 km. But our joint assessment with US intelligence indicates that it can fly more than 1,000 km,” a senior South Korean military official told the Seoul-based daily on condition of anonymity. “North Korea imported . . . Soviet era-made ‘Scud B’ missiles in the early 1980s through Egypt and has been constantly working to upgrade their specifications,” he added.
Scud –ER Revealed
The North Korean Scud–ER was first observed through intelligence imagery in 2005 in North Korea but was first revealed publicly in the 75 th anniversary of the Korean People’s Army, military parade held in Pyongyang on April 25, 2007. Its development was completed in 2003 with deployment that followed.
The Scud-ER (extended range) Scud derivation utilizes a single stage with storable propellants. This Scud variant range has been extended from the Scud-C range of 500 kilometers with a conventional warhead mass of 700-800 kilograms to a range of 750-800 kilometers or more with a conventional warhead mass of 450 kilograms or more.
Its engine stage combination is believed to be the same as used for the second stage on the Taepo-dong-1 satellite launch vehicle with its SAM-2 step throttled engine and propellant change. In its Taep’o-dong-1 second stage configuration it utilized an altitude thrust chamber verses the Scud-ER sea level thrust chamber. By Step throttling the turbine fed engine drives the Scud-ER over a longer range with a smaller mass warhead of 450 kilograms or more. This is not done merely or exclusively by reducing the warhead mass but also by using the higher launch thrust lower than that of the Scud-B but then step throttling the thrust at altitude down to a lower sustainer thrust level that extends the missile range performance. Literally the range performance can be shortened or extended by the phases of the thrust level performance from 100 % at launch to as low 65% or less at altitude which can in turn lengthen the single stage burn time or shorten it for a given propellant mass. That is the primary key to understanding the Scud-ER performance characteristics.
Scud-ER Performance Estimates
Designation – Scud –ER
Range – 750-800 or more km
Diameter – 0.855 m
Height – 9.5 – 11.37 meters depending on warhead size
Fin Span – 1.8 – 2.0 m
Launch Weight – 5,300 – 5,600 kg
Dry weight – 1,100 kg minus warhead
Guidance – Strap-down inertial
Thrust – 13,150 kgf max to [ 8,300 kgf at launch and 5,000 kgf at altitude]
Derivation on the SAM-2 step throttled engine using Scud-B propellants.
Thrust Chambers – 1
Steering – Rotating vanes in the exhaust jet (-4 to -5 sec Isp losses)
Isp. – 226 – 263 sec actual sea level to vac.
Mp – 3,771 – 3760 kg
Fuel – TM-185 =20% Gasoline, 80% Kerosene
Oxidizer – AK-27I =27% N2O4 + 73% HNO3 with Iodium inhibitor Nitrogen Tetroxide & Nitric Acid
Thrust/Weight -1.48 – 1.56 Gee’s
Burn time – Variable over flight duration
Warhead mass – 700 – 450 kg
C. P. Vick 2008 All Rights Reserved March 25, 2008 @wetgeo.com