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Aerodynamics Series

2018년 10월 13일 토요일

AIM-120C Study using Missile-SIM : Part 1 - Sensitivity

Previous Work Status

Initial Version of Missile-SIM for Performance evaluation

Aerodynamic Validation of Missile-SIM for Trajectory 

 Recently, I have configured some Python Missile-SIM for trajectory simulation; trajectory calculation and aerodynamic validation of CFD method are shown upper link.

 As the first study object, AIM-120C is chosen, and the objective of the study is sensitivity analysis for range performance and its optimization. Range of study includes "Rocket parameter", "Launch condition", and "Multi-stage version of CUDA". 

 This Part 1 will show sensitivity analysis of rocket parameter for AIM-120C baseline missile; Part 2 is optimization of rocket parameters and launch condition for longer range; Part 3 is proposal of AIM-120 sized dual-stage CUDA missile with optimized configuration. 

 Part 1 : Sensitivity Analysis of AIM-120C

 As shown in Fig. 1-1, baseline of AIM-120C is modeled; some part of the data like propellant weight, and burn time are referenced from previous estimation work. Target parameters of the sensitivity are propellant weight, burn-time, ISP, Drag(CD), Lift(CL), and usage of dual-pulse. 

 Reference launch condition is set as M1.3 at 30000ft, and I assumed missile go straight without altitude change. Range is calculated when speed of the missile is re-decreased as M1.3 (The missile should pursue target having at least M1.3 speed). 

Fig. 1-1. Specification of baseline model of AIM-120C and its sensitivity analysis range

Fig. 1-2 shows geometry modeling and part of CFD result; tail fin is cut-off to represent C-model, and both missile with and without flame shape. Missile-SIM could consider coefficient change via burn or burned-out status. Contour shows pressure and Mach number change around the missile for certain Mach number and AoA. Aerodynamic DB is calculated from M1.1 to 5 with AoA from 0 to 6 deg. High AoA region more than 6 deg is not considered because Missile-SIM trajectory is not re-enact turning-maneuverability of the missile yet. Drag coefficient of the missile with flame is smaller than that of flame-less shape because shape of the flame is mitigate effect of the base area caused by nozzle. 

Fig. 1-2. Geometry and CFD result of AIM-120C baseline model

1) Propellant Weight

+-20kg change of propellant weight is applied to calculate the sensitivity

2) Burn-Time

+-3s change of burn-time is applied to calculate the sensitivity

3) ISP

+-40s change of ISP is applied to calculate the sensitivity

4) Drag

+-10% change of drag is applied to calculate the sensitivity

5) Lift

+-10% change of lift is applied to calculate the sensitivity

6) Dual Pulse

Separation time are 2.5, 5.0, 7.5s are applied to calculate the sensitivity

7) Sensitivity Result

As a summary of Sensitivity (M1.3, 30kft)

(1) 1.2 km Range↑, M 0.1 Speed↑ via 1.0 kgof Propellant (in given total weight)

(2) 0.67 km Range, almost zero Speed change via 1.0 sof Burn time (smaller mass-flow)

(3) 0.2 km Range, M 0.01 Speed via 1.0 sof ISP

(4) 0.65 km Range, almost zero Speed change via 1.0 % Drag reduction

(5) almost zero Range, almost zero Speed change via 1.0 % Lift↑(negligible)

(6) 0.4 km Range, M 0.02 Speed↓ via 1.0 s increase of Dual pulse interval

Change of Lift is almost negligible for both range and peak speed performance. Higher lift configuration having more, longer, or larger fins is related to maneuverability and stability. 
It is natural that increase of some parameters (Propellant, and ISP) are directly proportional to the range and speed increase. 

Longer Burn-time and Drag reduction can increase range without change of speed performance. 
(Tendency can be changed at different reference condition)

It could be interesting result that increase of Pulse interval can extend range while small decrease of peak speed.  

In given hardware specification (weight, propellant, ISP, lift, and drag), longer burn-time and pulse interval are recommended to extend the range of the AIM-120C class missile. 

Improvement via optimization will be performed at Part 2; Result of this sensitivity is applied while study for trajectory and launch condition will be conducted

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