MITESD_77S10_pres06 (1)

MITESD_77S10_pres06 (1) - 16.888 Final Presentation...

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1 16.888 Final Presentation Airbag-Based Crew Impact Attenuation Systems for the Orion CEV Anonymous MIT Students 1
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Background and Motivation Orion CEV performance has been continually downgraded over the past two years due to continuing mass constraints Exploring an alternative airbag-based landing attenuation system concept 2
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Problem Formulation Problem Definition: Venting Mechanism Baseline Design Concept Project Goals: Optimize over a single airbag system to: -Gain insight into the influence of the design variables on overall impact attenuation performance -Develop a framework for future use with a multi-airbag model Fixed Parameter Value Venting Area Equiv. 2xØ2” area Operating Medium ( γ ) A i r ( 1 . 4 ) Impact Velocity 7.62m/s Gravitational Acceleration 9.81m/s 2 Atmospheric Pressure 101.325kPa 3 Design Parameters -Radius [R] -Length [L] -Inflation Pressure [P bagI ] -Valve Burst Pressure (measured as pressure in addition to inflation pressure) [ P burst ] Formulation min. β = Injury risk s.t. 0.1 R 0.5 [m] 0.3 L 0.85 [m] P bagI 101325 [Pa] P burst 0 [ P a ] Loaded Mass 2.5kg
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Lander Velocity vs Time Acceleration vs Time System Modeling Low fidelity model used 30 Velocity Validation -Based on preliminary design code for Mars Pathfinder airbag system (BAG) 20 -Approx. 3sec function evaluation time Design Vector (R, L, P bagI , P burst ) 10 Gas Dynamics Orifice Flow Dynamic s P w t , P t , V t , V AFP Iteration w Brinkley DRI X t t , U t t P Shape Function Fixed Parameters -40 0 Time Loop -20 0 0.02 0.04 0.06 0.08 0.1 Time (s) Acceleration Validation 0 -10 a(t) -30 β -50 Ac ce le ra ti on ( Eart h gs ) Ve lo ci ty (m /s Internal Variables Calculator -60 w mass of gas within airbag V airbag volume -70 V change in airbag volume AFP airbag footprint area 0 0.02 0.04 0.06 0.08 0.1 4 MATLAB Code BAG MATLAB Code
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5 Single Objective Optimization Design of Experiments: Orthogonal Array • Efficient and balanced • Reduced number of experiments required Starting Point R=0.2m, L=0.3m, P bagI =1.1atm, P burst =8kPa Sequential Quadratic Programming • Gradient based method • No analytical expression for gradient • Availability of the program ‘fmincon.m’ Simulated Annealing • Heuristic method • Noisy design space • Reasonable number of function evaluations Factor Level 1 Level 2 Level 3 Radius (m) 0.2 0.3 0.4 Length (m) 0.3 0.5 0.7 P bagI (atm) 1.0 1.1 1.2 P burst (kPa) 81 21 6 R L P bag P burst 0.122 0.311 101820 4088 DRI 2.890 R L P bag P burst 0.100 0.300 101325 8000 DRI 3.220
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Single Objective Optimization 4.5 6 R 0.122 L 0.311 P bagI 101820 P burst 4088 DRI 2.890 Sequential Quadratic Programming Unscaled x 0 = DOE Solution 1 2 3 4 5 6 3.5 4 5 5.5 6 X: 6 Y: 3.762 Iteration Number 1 1.5 2 2.5 3 3.2 3.4 3.6 3.8 4 Iteration Number Scaled x 0 = Unscaled SQP Solution Simulated Annealing
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This note was uploaded on 11/08/2011 for the course AERO 16.851 taught by Professor Ldavidmiller during the Fall '03 term at MIT.

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MITESD_77S10_pres06 (1) - 16.888 Final Presentation...

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