Mass Savings and Finite Element Analysis FEA Preparation

Mass Savings and Finite Element Analysis (FEA) Preparation for Orbital Transfer Vehicle (OTV) 100 gram Case Tim Rebold STRC [1] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Mass Savings A-A Lander § Savings 1. 2. 3. 4. § Skin panel reduction Reduced OTV diameter to match Lunar Lander Attachment interface being separated Modified truss and electronic floor beam dimensions A A Added supports stiffen stringers for mounting equipment Skirt / Payload Attach Fitting (PAF) Ø = 2. 06 m Standard launch vehicle (Dnepr) interface Mass Reduced § § § [2] Mass reduction: 27. 73 kg (59% reduction) Total Structural Mass: 49. 37 kg (excluding 14. 3 kg thermal control) finert = 0. 22 AAE 450 Spring 2009 *Not to scale [Tim Rebold] [STRC]

FEA Preparation § Model – Thin wall & beam elements model structural components – Lumped masses represent non-structural components § Concerns – Assumption used to size truss frame was based on capability to only carry axial loads • Moments might produce yielding stresses – Stresses at joints and connections – Axial and lateral modes (resonant frequencies) • Can stiffen skirt until requirements are satisfied – Vibrations transmitted to electronics and solar array structure [3] 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 § FEM analysis – Obtain better approximation of center of mass and inertia values – Perform modal analysis to see if OTV meets stiffness requirements placed on launch vehicle payloads – Perform stress and strain analysis for various load cases – Ensure all components will be protected from a dynamic environment [5] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Arbitrary Payload Case § Variables – OTV payload (Lander) : Expected to scale linearly – Number of engines & propulsion system size : Increases structural support but should be scaled relatively linearly – Solar Array size : Increased structural support mass and will most likely be scaled exponentially [6] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Mass Savings Summary Aluminum 6061 -T 6 material selected for all structural elements MASS SAVINGS (kg) Components Old New Reduction Savings (%) E-MOD floor beams 7. 07 3. 80 3. 27 46 E-MOD floor overlay 4. 88 3. 52 1. 36 28 Shear / Skin panels 13. 82 3. 91 9. 91 72 Propulsion support frame 4. 30 2. 07 2. 23 52 Stringers / Stiffeners 6. 28 6. 07 0. 21 3 PAF release 10. 75 0 10. 75 100 Total 47. 10 19. 37 27. 73 59 Abbreviations • E-MOD: Electronics Module [7] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Structural and Thermal Budgets MASS (kg) Components [8] E-MOD floor beams & overlay 7. 32 Shear / Skin panels 3. 91 Propulsion support frame 2. 07 Stringers / Stiffeners 6. 07 Integration (Lander and propulsion module) 22* Fasteners (welds, rivets, bolts, adhesives) 8* E-MOD thermal control 11. 1 Propulsion thermal control 3. 2 Total (structures) 49. 37 Total (thermal) 14. 3 TOTAL 63. 67 AAE 450 Spring 2009 *Estimates [Tim Rebold] [STRC]

Dimensions - OTV x Lander 1. 8 m 1. 45 m Stiffener / C-Channels 0. 95 m Skin panels removed 0 m Skirt / Payload Attach Fitting (PAF) *Not to scale [9] Ø = 2. 06 m AAE 450 Spring 2009 [Tim Rebold] [STRC]

Integration Ring Dimensions 1 cm 3. 6 cm Lander 2. 00 m *Not to scale [10] Ø = 2 cm (6 equally spaced over C-Channels) AAE 450 Spring 2009 Mass = 5. 93 kg [Tim Rebold] [STRC]

Payload Attach Fitting Dimensions A Mass = 40. 08 kg A 6 cm Cross Section 3. 6 cm 2. 12 m 1 cm Web thickness = 4 mm 14. 8 cm Ø = 4 cm (8 equally spaced) 1 cm A-A 6 cm *Not to scale [11] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Dimensions – C-Channels 2. 75 cm Cross sectional area = 0. 000252 m 2 Length = 1. 45 m Mass = 1. 0114 kg ρ = 2768 kg/m 3 3 mm 3. 5 cm Stringer / Stiffener Cross-Section Why a C-Channel? • Easy access for making connections to other members • Provides a relatively high moment of inertia *Not to scale [12] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Dimensions – Propulsion Support Electronics Module 0. 50 m 0. 66 m 0. 57 m 0. 30 m (includes 1 cm clearance over Xenon tank) Ø = 0. 58 m 0. 65 m 0. 36 m 0. 90 m OTV Base 0. 20 m *Not to scale [13] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Dimensions – Propulsion Support Frame 4 Stringer / Stiffener Cross-Section Might need to thicken flange to tolerate local stresses Weld 2 b 3 Pinned joint Propulsion truss frame 1 [14] Member 1 2 3 4 t (mm) 0. 77 3. 2 0. 5 1. 52 h (cm) 0. 75 2. 20 0. 75 AAE 450 Spring 2009 b (cm) 0. 75 2. 20 0. 75 t h b [Tim Rebold] [STRC]

Dimensions – Electronic Module Electronics Module Ø = 0. 25 m 0. 50 m Thin (0. 5 mm) floor skin 0. 03 m 0. 05 m, Floor beam height Components not placed under lander nozzle and above floor lacking beam supports 6 beams spanning from OTV stiffeners of length 0. 57 m Beams welded to thin (mm’s) circular ring *Not to scale [15] AAE 450 Spring 2009 [Tim Rebold] [STRC]

Dimensions - Electronic Module Floor Support Electronic Module Support No. Beams t (mm) b (cm) h (cm) 6 2. 9 2. 5 5. 0 Battery DC / DC Converter Stringer / Stiffener Cross-Section PCDU PSU b Thin 0. 5 mm floor overlays beam supports h t Electronic Module floor beam supports b [16] AAE 450 Spring 2009 Weld Electronic Module floor beam supports Acronyms • PCDU: Power Conditioning Distribution Unit • PSU: Power Supply Unit [Tim Rebold] [STRC]

FEA – Set Up [17] AAE 450 Spring 2009 [Tim Rebold] [STRC]