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The DF-21D Antiship Ballistic Missile

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## The DF-21D Antiship Ballistic Missile

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**The DF-21D AntishipBallisticMissile**Ralph Savelsberg Netherlands Defence Academy**Introduction**PRC is developing an Antiship Ballistic Missile against U.S. aircraft carriers**Introduction**ASBM has a maneuverable re-entry vehicle (MaRV) MaRV has on-board radar and control fins to steer towards its target**Introduction**MaRVs are not a new concept U.S. Pershing II Chinese DF-15B Photo: user rocbolt on www.flickr.com**Original DF-21 is two-stage nuclear-tipped missile**DF-21A has lighter structure and longer range DF-21C has a conventional warhead DF-21D is ASBM Introduction The ASBM is a variant of the DF-21**Introduction**Few concrete details are available in open sources Questions: • How large is missile range (U.S. DoD 1500 km +)? • How far can MaRV deviate from ballistic trajectory? • What profiles can the MaRV fly? Computer simulations are used to find the answers For unknown parameters, use data from • earlier versions of DF-21 • Pershing II • conservative estimates**Introduction**Trajectory simulation is split into two parts Ballistic trajectory model MaRV trajectory model**Ballistic trajectory simulations**Ballistic trajectory model • Point mass model • Model similar to GUI_missile_flyout by G.E. Forden* • Equations solved in Simulink® *GUI Missile Flyout: A General Program for Simulating Ballistic Missiles, Science and Global Security, Vol. 15, 2007.**Ballistic trajectory simulations**Some specifications of the DF-21 and DF-21A have been published Parameters needed to model DF-21 were derived by G.E. Forden* Source: Jane’s strategic weapons systems *A Preliminary Analysis of the Chinese ASAT Test, Tech. rep., MIT, 2007**Ballistic trajectory simulations**DF-21A parameters are derived from Forden’s DF-21 parameters • Same propellant • Same burn time • Propellant is 87% of stage mass vs. 85% • Increased mass and mass saved by lighter structure used to lengthen 2nd stage**Ballistic trajectory simulations**Simulated ranges agree well with published values The derived missile parameters are reasonably accurate DF-21A booster parameters are used for DF-21D**MaRV mass is estimated using Pershing II data**• Mass of Pershing II MaRV is 677 kg, including nuclear warhead • Approx. mass of DF-21D MaRV is 1000 kg, including 500 kg conv. Warhead With this mass, DF-21D range is 1.8•103 km**Ballistic trajectory simulations**Visualization in Google Earth™**Ballistic trajectory simulations**Total flight time is 12 minutes At start of re-entry speed is 3.7 km/s (Ma=13) at an angle of 39.7o below horizontal**MaRV trajectory simulations**MaRV trajectory model • 2D polar coordinates • Includes lift and drag • Equations of motion are those by Hankey* • Equations solved in Simulink® *Re-entry Aerodynamics, AIAA Education Series, AIAA, Washington DC, 1988.**MaRV trajectory simulations**The model includes more of the vehicle aerodynamics • Vehicle is steered by changing angle-of-attack a • Model uses quasi-static approach (vehicle is treated as though it is trimmed in pitch) • CL and CD as function of Ma and a are calculated using USAF missile DATCOM code However, this requires knowing the shape and location of center of gravity**MaRV trajectory simulations**Shape of the DF-21D MaRV is unknown DF-15B MaRV is too small**MaRV trajectory simulations**DF-21D is modeled as Pershing II with 500 kg warhead**MaRV trajectory simulations**Maximum angle of attack depends on Ma**MaRV trajectory simulations**From 50 km to target, missile is steered using proportional navigation • Commanded acceleration: with N = 3 • Time delay of 0.5 s between commanded and actual acceleration nM • Actual acceleration is limited by alimit**MaRV trajectory simulations**Intercept of opening target During 12 minute flight time, carrier can move roughly 12 km (at 30 knots). This is not enough**MaRV trajectory simulations**Lateral acceleration is less than the maneuvering limit**MaRV trajectory simulations**The MaRV is sufficiently maneuverable to hit targets at 30+ km**MaRV trajectory simulations**At the extreme end of the range, it flies almost horizontally**MaRV trajectory simulations**A closing target at 20 km is approached from directly overhead This is inside the blind spot of radars on the ship**MaRV trajectory simulations**Lateral acceleration peaks at -50 g This is close to maneuvering limit for surface-to-air missiles**Conclusions**Conclusions • The range of the ballistic part of the trajectory is 1.8•103 km • The aircraft carrier cannot evade • The MaRV can fly trajectories that make it extremely hard to intercept