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Tim Rebold STRC

Mass Savings and Finite Element Analysis (FEA) Preparation for Orbital Transfer Vehicle (OTV) 100 gram Case. Tim Rebold STRC. [1] . Mass Savings. A-A. Lander. Added supports stiffen stringers for mounting equipment. Skirt / Payload Attach Fitting (PAF). A. A.

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Tim Rebold STRC

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

  2. Mass Savings A-A Lander Added supports stiffen stringers for mounting equipment Skirt / Payload Attach Fitting (PAF) A A Standard launch vehicle (Dnepr) interface Ø = 2.06 m • Mass Reduced • Mass reduction:27.73 kg (59% reduction) • Total Structural Mass: 49.37 kg (excluding 14.3 kg thermal control) • finert = 0.22 *Not to scale [Tim Rebold] [STRC] [2] • Savings • Skin panel reduction • Reduced OTV diameter to match Lunar Lander • Attachment interface being separated • Modified truss and electronic floor beam dimensions

  3. FEA Preparation [Tim Rebold] [STRC] [3] • 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

  4. References [Tim Rebold] [STRC] [4] (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. 2nd 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?WTSAppName=Lib_edupackk (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_Guide.pdf (6) Larson, W.J. Spacecraft Structures and Mechanisms. Microcosm, Inc. , 1995

  5. Future Work [Tim Rebold] [STRC] [5] • 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

  6. Arbitrary Payload Case [Tim Rebold] [STRC] [6] • 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

  7. Mass Savings Summary Aluminum 6061-T6 material selected for all structural elements • Abbreviations • E-MOD: Electronics Module [Tim Rebold] [STRC] [7]

  8. Structural and Thermal Budgets *Estimates [Tim Rebold] [STRC] [8]

  9. Dimensions - OTV x 1.8 m 1.45 m Stiffener / C-Channels Lander 0.95 m Skin panels removed Ø = 2.06 m 0 m Skirt / Payload Attach Fitting (PAF) *Not to scale [Tim Rebold] [STRC] [9]

  10. Integration Ring Dimensions 1 cm 3.6 cm Lander 2.00 m Ø = 2 cm (6 equally spaced over C-Channels) Mass = 5.93 kg *Not to scale [Tim Rebold] [STRC] [10]

  11. 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 1 cm Ø = 4 cm (8 equally spaced) 1 cm 6 cm A-A *Not to scale [Tim Rebold] [STRC] [11]

  12. Dimensions – C-Channels 2.75 cm Cross sectional area = 0.000252 m2 Length = 1.45 m Mass = 1.0114 kg ρ = 2768 kg/m3 Stringer / Stiffener Cross-Section 3 mm 3.5 cm • Why a C-Channel? • Easy access for making • connections to other • members • Provides a relatively high • moment of inertia *Not to scale [Tim Rebold] [STRC] [12]

  13. 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 [Tim Rebold] [STRC] [13]

  14. Dimensions – Propulsion Support Frame 4 t h Stringer / Stiffener Cross-Section Might need to thicken flange to tolerate local stresses b 2 3 Weld Weld t (mm) 0.77 3.2 0.5 1.52 h (cm) 0.75 2.20 0.75 0.75 b (cm) 0.75 2.20 0.75 0.75 b Member 1 2 3 4 Pinned joint Propulsion truss frame 1 [Tim Rebold] [STRC] [14]

  15. Dimensions – Electronic Module Ø = 0.25 m Electronics Module 0.03 m 0.50 m Thin (0.5 mm) floor skin 0.05 m, Floor beam height Components not placed under lander nozzle and above floor lacking beam supports Beams welded to thin (mm’s) circular ring 6 beams spanning from OTV stiffeners of length 0.57 m *Not to scale [Tim Rebold] [STRC] [15]

  16. Dimensions - Electronic Module Floor Support Battery DC / DC Converter Stringer / Stiffener Cross-Section PCDU PSU Thin 0.5 mm floor overlays beam supports Weld b Electronic Module floor beam supports Electronic Module floor beam supports h t • Acronyms • PCDU: Power Conditioning Distribution Unit • PSU: Power Supply Unit b [Tim Rebold] [STRC] [16]

  17. FEA – Set Up [Tim Rebold] [STRC] [17]

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