AAE450 Spring 2009 Mass Savings and Finite Element Analysis (FEA) Preparation for Orbital Transfer Vehicle (OTV) 100 gram Case Tim Rebold STRC [Tim Rebold] [STRC] [1]

AAE450 Spring 2009 Mass Savings [Tim Rebold] [STRC] *Not to scale  Savings 1.Skin panel reduction 2.Reduced OTV diameter to match Lunar Lander 3.Attachment interface being separated 4.Modified truss and electronic floor beam dimensions [2] Skirt / Payload Attach Fitting (PAF) A-A Added supports stiffen stringers for mounting equipment Standard launch vehicle (Dnepr) interface Lander A A Ø = 2.06 m  Mass Reduced  Mass reduction: kg (59% reduction)  Total Structural Mass: kg (excluding 14.3 kg thermal control)  f inert = 0.22

AAE450 Spring 2009 FEA Preparation [Tim Rebold] [STRC]  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]

AAE450 Spring 2009 References [Tim Rebold] [STRC] (1) Delta II Payload Planners Guide Guide_Update_0103.pdf (2) Skullney, W.E. Fundamentals of Space Systems. 2 nd Edition. Ch. 8, pp Oxford University Press, (3) “Properties of Materials.” Purdue University. kk kk (4) Sun, C.T. Mechanics of Aircraft Structures. New York: John Wiley and Sons, (5) Dnepr User’s Guide uide.pdf uide.pdf (6) Larson, W.J. Spacecraft Structures and Mechanisms. Microcosm, Inc., 1995 [4]

AAE450 Spring 2009 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 [Tim Rebold] [STRC] [5]

AAE450 Spring 2009 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 [Tim Rebold] [STRC] [6]

AAE450 Spring 2009 Mass Savings Summary [Tim Rebold] [STRC] [7] MASS SAVINGS (kg) ComponentsOldNewReductionSavings (%) E-MOD floor beams E-MOD floor overlay Shear / Skin panels Propulsion support frame Stringers / Stiffeners PAF release Total Aluminum 6061-T6 material selected for all structural elements Abbreviations E-MOD: Electronics Module

AAE450 Spring 2009 Structural and Thermal Budgets [Tim Rebold] [STRC] [8] MASS (kg) Components E-MOD floor beams & overlay7.32 Shear / Skin panels3.91 Propulsion support frame2.07 Stringers / Stiffeners6.07 Integration (Lander and propulsion module)22* Fasteners (welds, rivets, bolts, adhesives)8* E-MOD thermal control11.1 Propulsion thermal control3.2 Total (structures)49.37 Total (thermal)14.3 TOTAL63.67 *Estimates

AAE450 Spring 2009 Dimensions - OTV [Tim Rebold] [STRC] *Not to scale [9] Skirt / Payload Attach Fitting (PAF) 1.8 m x 0 m 1.45 m 0.95 m Lander Ø = 2.06 m Skin panels removed Stiffener / C-Channels

AAE450 Spring 2009 Integration Ring Dimensions [Tim Rebold] [STRC] *Not to scale Lander [10] Ø = 2 cm (6 equally spaced over C-Channels) 2.00 m 3.6 cm Mass = 5.93 kg 1 cm

AAE450 Spring 2009 [Tim Rebold] [STRC] *Not to scale [11] 1 cm Payload Attach Fitting Dimensions 6 cm 2.12 m Ø = 4 cm (8 equally spaced) Cross Section 3.6 cm 1 cm 6 cm 1 cm 14.8 cm A-A Web thickness = 4 mm Mass = kg A A

AAE450 Spring 2009 Dimensions – C-Channels [Tim Rebold] [STRC] *Not to scale [12] Stringer / Stiffener Cross-Section 2.75 cm 3 mm 3.5 cm Cross sectional area = m 2 Length = 1.45 m Mass = kg ρ = 2768 kg/m 3 Why a C-Channel? Easy access for making connections to other members Provides a relatively high moment of inertia

AAE450 Spring 2009 Dimensions – Propulsion Support [Tim Rebold] [STRC] *Not to scale Electronics Module [13] 0.36 m 0.65 m 0.57 m 0.20 m Ø = 0.58 m 0.30 m (includes 1 cm clearance over Xenon tank) 0.50 m 0.90 m 0.66 m OTV Base

AAE450 Spring 2009 Dimensions – Propulsion Support Frame [Tim Rebold] [STRC] [14] Member t (mm) h (cm) b (cm) t h b b Weld Propulsion truss frame Stringer / Stiffener Cross-Section Weld Might need to thicken flange to tolerate local stresses Pinned joint

AAE450 Spring 2009 Dimensions – Electronic Module [Tim Rebold] [STRC] *Not to scale [15] 0.05 m, Floor beam height 6 beams spanning from OTV stiffeners of length 0.57 m Electronics Module 0.03 m Ø = 0.25 m Thin (0.5 mm) floor skin Beams welded to thin (mm’s) circular ring Components not placed under lander nozzle and above floor lacking beam supports 0.50 m

AAE450 Spring 2009 Dimensions - Electronic Module Floor Support [Tim Rebold] [STRC] [16] t b h Electronic Module floor beam supports PCDU PSU Thin 0.5 mm floor overlays beam supports BatteryDC / DC Converter Acronyms PCDU: Power Conditioning Distribution Unit PSU: Power Supply Unit Electronic Module Support No. Beamst (mm)b (cm)h (cm) b Weld Electronic Module floor beam supports Stringer / Stiffener Cross-Section

AAE450 Spring 2009 FEA – Set Up [Tim Rebold] [STRC] [17]