Support structure for Orbital Transfer Vehicle OTV Tim

Support structure for Orbital Transfer Vehicle (OTV) Tim Rebold STRC [1] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Propulsion System Support Structure PPU § Truss / Frame Electronics Module – Statically determinate m = 106 kg • Less members , less complex • More efficient (mass savings) • Reduces cabling • Easier Integration • Easier Testing Xenon Tank & Propellant • Thermal balance issue – Only carry axial loads • Hard to realize • Joints need to carry predicted bending & shear m = 1. 6 kg Longer cabling Plumbing / Valves / Etc. – Loads (launch) are evenly distributed [2] PSU Thruster m = 5. 7 kg AAE 450 Spring 2009 *Not to scale **Contingency mass unrepresented [Tim Rebold] [STRC]

OTV Configuration § Goals – Center of Mass (CM) as close to aft (base) of spacecraft (s/c) – Design truss efficiently to minimize mass – Factor of Safety = 1. 5 Lander Electronics Module A A Propulsion System & Support Structure § § § Primary Mass: 31 kg Support Mass: 15. 24 kg Minert budget: <3. 76 kg finert = 0. 3 *Not to scale [3] § Conclusions AAE 450 Spring 2009 [Tim Rebold] [STRC]

References (1) Delta II Payload Planners Guide http: //snebulos. mit. edu/projects/reference/launch_vehicles/Delta/DELTA_II_User_ Guide_Update_0103. pdf (2) Skullney, W. E. Fundamentals of Space Systems. 2 nd Edition. Ch. 8, pp. 465 -564 Oxford University Press, 2005. (3) “Properties of Materials. ” 2009. Purdue University. http: //www. lib. purdue. edu/eresources/wts/result. html? WTSApp. Name=Lib_edupac kk (4) Sun, C. T. Mechanics of Aircraft Structures. New York: John Wiley and Sons, 2006. (5) Dnepr User’s Guide http: //snebulos. mit. edu/projects/reference/launch_vehicles/DNEPR/Dnepr_User_G uide. pdf (6) Larson, W. J. Spacecraft Structures and Mechanisms. Microcosm, Inc. , 1995 [4] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Future Work § Mount Solar Arrays, Reaction Control Wheels, Antenna, and Thermal components into OTV § Matlab script – Read data from Excel spreadsheet to calculate entire OTV (with payload) CM, and inertia matrix (about CM coordinates) in stowed (launch) and deployed (trans-lunar) stages § FEM analysis – Obtain better approximation of CM and inertia values – Perform modal analysis to see if OTV meets stiffness requirements placed on launch vehicle payloads [5] AAE 450 Spring 2009 [Tim Rebold] [STRC]

OTV CM Tracker - Current Best Estimate (Axial) Acronyms • PPU: Power Processing Unit • PSU: Power Supply Unit • RCS: Reaction Control System Lander, 1. 75 m, 220 kg x Electronics Module, 1. 25 m, 24. 3 kg • PPU • PSU MOTV = 550 kg CM = 1. 056 m 1. 5 m 1 m Structural / Thermal Control, 0. 75 m, 110. 88 kg Xenon Tank & Propellant, 0. 685 m, 106 kg Solar Arrays, 0. 50 m, 13. 3 kg Feed system & Contingency Mass, 0. 45 m, 4. 7 kg 0 m *Not to scale [6] RCS Wheels, 0. 05 m, 6 kg Electric Propulsion Thruster, 0. 10 m, 5. 7 kg Antenna / Mount, 0 m, 9. 12 kg AAE 450 Spring 2009 [Tim Rebold] [STRC]

Truss Configuration – 2 D Planar F 1 y 4 R 2 x F 1 x Stability Criterion 4 joints (j) 4 Reaction DOF’s (r)* 4 members (m) 2 Aluminum 7075 -T 6 material selected for all structural elements Distributed forces from propulsion system through launch 3 2 j = m + r 8=8 R 1 y R 1 x 1 F 2 x F 2 y [7] AAE 450 Spring 2009 *4 th reaction DOF not utilized for given applied loads [Tim Rebold] [STRC]

Support Structure Analysis Summary Propulsion Frame Support SYSTEM SUPPORT MASS Mass (kg) Equatorial Mount 4. 48 Bottom Mount 1. 08 Frame 1. 61 Electronic Module 8. 07 Total 15. 24 Member Cross Sectional Area (mm 2) 1 18. 82 2 111. 97 3 5. 71 4 44. 96 Electronic Module Support h t No. Beams t (mm) b (cm) h (cm) 6 1. 4 2. 5 5. 0 b [8] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Dimensions Electronics Module 0. 320 m PPU PSU 0. 7950 m 0. 236 m φ = 0. 470 m 0. 9350 m 0. 5 m 1. 03 m 0. 2 m *Not to scale [9] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Tank Support - Equatorial Mount Tank Mounting Flange Bolted Attachment Support Structure Xenon Tank To avoid high shell stresses, introduce loads tangentially to tank surface rather than radially *Figure based from Reference 6 [10] AAE 450 Spring 2009 [Tim Rebold] [STRC]