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s 3.4.3.4 TMI module design HMM Assessment Study Report: CDF-20(A) February 2004 page 240 of 422 The tank design includes an inner and outer vessel(s), stiffening rings, insulation system, a fluid acquisition system (piping, valves), and a thermal system. The inner vessel will be constructed from inconel (corrosion resistant) and the outer vessels from aluminium (lower density). A cylindrical geometry (4.8 m length, 4.7 m diameter) has been retained for the hydrogen vessel and a nested spherical vessel (4.7 m diameter) for the oxygen (type Ariane-5 ECP). The primary objective of the tank thermal design is to minimise the heat transfer to the inner vessel and optimise its related mass. The heat loads have been considered on the basis of a worst case assumption). Sun + IR planet LH2 LOx LOx Figure 3-76: Tanks schematic Sun + IR planet Boiling of cryogens occurs when temperature exceeds locally the saturation temperature at a certain pressure. Tanks are initially pressurised at 2 bars before launch, which gives the liquid properties shown in Table 3-67: At 2 bars Temperature Latent heat of vaporization Density (liq.) Saturated hydrogen 22.9 K 4.29E5 J/kg 67.4 kg/m3 Saturated oxygen 97.2 K 2.06E5 J/kg 1120 kg/m3 Table 3-67: Cryogens properties 3.4.3.4.1 Shielding and insulation, passive techniques In vacuum, Multi Layer Insulation (MLI) is the best=performing insulation compared to other types including permeable insulations (gas filled powders, evacuated powders) or solid foams with closed or open cells (Airex, Rohacell). Insulation Expanded Gas-filled Evacuated Opacified MLI foams powder powders powders Conductivity 0.026 W/m/K 0.019 W/m/K 5.9E-4 W/m/K 3.3E-4 W/m/K 1.4E-5 W/m/K Table 3-68: Insulation properties MLI efficiency comes from an effective reduction of conductive and radiative coupling with the use of multiple layer radiation shields interspaced by an insulant. Without pressure loads, the equivalent efficiency depends on the number of layers, and the global heat transfer to the vessel can be simply assessed providing the following hypothesis: • heat transfer to the fluid per conduction only (steady fluid), no contact resistance
s HMM Assessment Study Report: CDF-20(A) February 2004 page 241 of 422 • radiative foils are parallel. A correlation factor is considered to fit experimental data (20 layers). The variation of the efficiency at cryogenic temperatures is assumed close to zero • parasitic heat transfers through piping, rings and other structural elements are provisioned to 5W per default (sensitivity to the design and the temperature of elements) • antireflective external layer (requirement for visiting vehicles) is imposed with betacloth Hydrogen heat loss [W] 30 25 20 15 10 5 0 1.0E- 04 2.0E- 04 3.0E- 04 4.0E- 04 5.0E- 04 6.0E- 04 7.0E- 04 equivalent emissivity 8.0E- 04 9.0E- 04 1.0E- 03 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 boil off [kg/mth] Oxygen heat loss [W] 40 35 30 25 20 15 10 Figure 3-77: Heat loss 5 0 1.0E-04 6.0E-04 1.1E-03 1.6E-03 2.1E-03 2.6E-03 equivalent emissivity Therefore, considering the here above geometry, Hydrogen Oxygen maintaining boil-off below 70 kg/mth 430 kg/mth requires at least an MLI equivalent efficiency of 3.6E-4 2.2E-3 and leaves a residual heat loss of 11 W 33W Table 3-69: Requirements Constrained by the attachment points (compression loads), MLI performance (ratio efficiency / mass) degrades beyond a certain thickness (40-50 layers). A solution is to have different supporting structures. The equivalent efficiency for Double Aluminized Kapton (DAK) and Double Goldenized Kapton (DGK) is indicated in Figure 3-78. To meet the mentioned requirement, 190 of DGK (320 layers of DAK), interspaced with Dacron would be needed. equivalent efficiency 4.6E-03 4.1E-03 3.6E-03 3.1E-03 2.6E-03 2.1E-03 1.6E-03 1.1E-03 6.0E-04 1.0E-04 20 50 80 110 140 170 200 230 260 290 320 number of layers DAK DGK Hydrogen heat loss [W] 50.00 40.00 30.00 20.00 10.00 500 475 450 425 400 375 350 325 300 275 250 225 200 175 150 125 100 75 50 25 0 0.00 20 50 80 110 140 170 200 230 260 290 320 number of layers DAK DGK sun shade - DAK sun shade - DGK Figure 3-78; Equivalent efficiency and heat looses as a function of the number of layers boil off [kg/mth]
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s HMM Assessment Study Report: CDF-
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s STUDY TEAM HMM Assessment Study R
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s T A B L E O F C O N T E N T S HMM
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s L I S T O F F I G U R E S HMM Ass
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s L I S T O F T A B L E S HMM Asses
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s 1 INTRODUCTION 1.1 Background HMM
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s 2 GENERAL ARCHITECTURE 2.1 Study
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s 2.2.4.2 Accelerations HMM Assessm
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s 2.2.4.4 Temperature and relative
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s Figure 2-10: Trajectory Overview
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s 2.4.3.5 TEI and planetary protect
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s Mars Excursion Vehicle Transfer H
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s 2.7.5.1 Mission elements dry mass
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s 2.7.5.8 MEV release The MEV is re
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s Total mission time (days) 1200 10
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s stack 9 Propellant mass of the ne
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s The core supporting structure has
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s 2.7.7.1.3 Mars excursion module S
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s 2.7.7.1.4 Earth return capsule HM
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s Mission Phase Description Event s
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s Mission Phase Description Event s
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s 2.7.10 Mission performance Table
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s Days on Martian surface 450 400 3
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s Maximum manoeuvre duration 6 mont
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s % of loss from baseline 20 18 16
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s 2.7.15 Sensitivity analysis HMM A
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s 2.7.15.4 Influence of the mass of
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s Parameters used: • No Shuttle
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s 2.8.3.3 Launch 3- Front node Figu
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s 2.10.1.4 Communications HMM Asses
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s 2.10.2.2.2 LEO assembly HMM Asses
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s Basic RF link Four 70-m Ka-band s
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s 3 TRANSFER VEHICLE 3.1 Systems…
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s Operational Requirements It shall
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s Trans Mars Injection Module Mars
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s Figure 3-2: Parallel configuratio
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s Figure 3-6: Global dimensions com
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s Front Node 3.2.3.1.3 EVA systems
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s Trans Mars Injection (three stage
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s Figure 3-16: Recommendations for
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s Factors to be considered Impacts
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s Figure 3-24: Baseline design back
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s Figure 3-26: Baseline design priv
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s Module part 3............= 0 m 3
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s 3.3.2.1 Requirements and design d
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s flux [W/m2] 250 200 150 100 50 0
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s Figure 3-38: Power required to ma
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s 3.3.4.3 Assumptions and trade-off
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s 3.3.4.3.3 Power conditioning and
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Page 193 and 194: s Configuration Length (m) Total ma
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s cryocooler heat lift [W] cryocool
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s • a duty cycle value (duration
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s Figure 4-48: MAV Power Inputs HMM
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s 4.3.5.4.2 Power storage HMM Asses
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s Figure 4-52: Regenerative Fuel Ce
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s Figure 4-54: Solar irradiance on
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s 450.00 400.00 350.00 300.00 250.0
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s 4.3.6.1 Budgets HMM Assessment St
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s Surface Surface Container MAV Con
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s 4.3.9.3 Baseline design 4.3.9.3.1
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s Bio-Lock Masses: Core Samples No.
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s Figure 4-72: Entry Velocity (L) a
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s 2 3.9 233 923.1 347 923 12.3 352
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s Figure 4-85: Communications MEV/M
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s 4.4.5.3.2 GNC equipment HMM Asses
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s 4.4.5.4 Control laws generation H
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s Finally, the Figure 4-97 shown th
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s velocity (m/sec) altitude (km) 50
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s 4.5 Mars Ascent Vehicle 4.5.1 Tra
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s Term Value Unit Radius of equator
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s Inclination (deg) 47.5 47 46.5 46
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s 4.5.3 Structures HMM Assessment S
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s 4.5.5 Thermal HMM Assessment Stud
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s 4.5.5.3 Baseline thermal design H
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s Crew Ingress/Egress Hatch: HMM As
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s Element 3: Mars Ascent Vehicle HM
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s 4.5.7.5 Budgets Characteristic Va
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s PER DAY PER MISSION DRINKING WATE
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s 5 OVERALL CONCLUSIONS HMM Assessm
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s 6 APPENDIX A - MARTIAN SURFACE NU
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s Figure 6-1: Example of buried rea
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s 7 APPENDIX B - REFERENCES [RD1] C
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s [RD26] IES2, Phase A0: Final Repo
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s [RD85] Mars Transportation Enviro
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s 8 APPENDIX C - ACRONYMS AAA Avion
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s MLI Multi-Layer Insulation MMH Mo
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