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s HMM Assessment Study Report: CDF-20(A) February 2004 page 76 of 422 • The global dust storm season on Mars. This occurs for approximately 3 months on either side of the Martian perihelion passage. • Superior conjunction (i.e. the Earth and Mars are on opposite sides of the Sun). In this situation there is a communications difficulty that can last for up to 55 days (an angle of 10° either side of the Sun). • Martian winter at the landing site if power is supplied by solar arrays. The power subsystem provides a cut-off associated with the size of the solar arrays. In winter the solar flux reaching the Martian surface is reduced so the lander would have insufficient power. The exact length of the excluded time period depends on the landing site latitude. There is a trade-off to ensure that the size of the solar arrays does not impact too greatly on other subsystems by providing more opportunities for surface stays. In the case of a fuel cell power source, the landing site and hence the Martian season are immaterial. In addition there are several mission operations during which the surface stay cannot take place. These are: • Aerobraking • Final Martian orbit acquisition • System check. These are assumed to last 1 week after arrival in the final Martian orbit and 2 weeks before departure on the return journey to Earth. • MAV-TV rendezvous. This can take several days at the end of the surface stay. The analysis took into account: • Selection of the power source used, whether solar arrays or fuel cells. • Selection of one of four landing site latitudes: 21°N, 12.5°N, 12.5°S and 22.5°S. However, in the case of using fuel cells, the landing site is immaterial. • Selection of whether or not to include dust deposition on the solar arrays when considering the power constraints. Figure 2-38 shows how the opportunities vary when the landing site and the aerobraking manoeuvre are taken into account. Note that the fuel cell case is the same as the best case of each of the solar cell launch window scenarios. Aerobraking manoeuvres are considered to last six months in this case also.
s Days on Martian surface 450 400 350 300 250 200 150 100 50 0 01. 23/11/2028, Aero-braked, 12.5N 01. 23/11/2028, Aero-braked, 12.5S 01. 23/11/2028, Aero-braked, 21N 01. 23/11/2028, Aero-braked, 22.5S 01. 23/11/2028, Not aero-braked, 12.5N 01. 23/11/2028, Not aero-braked, 12.5S 01. 23/11/2028, Not aero-braked, 21N 01. 23/11/2028, Not aero-braked, 22.5S 02. 17/02/2031, Aero-braked, 12.5N 02. 17/02/2031, Aero-braked, 12.5S 02. 17/02/2031, Aero-braked, 21N Surface opportunity 1 Surface opportunity 2 Surface opportunity 3 02. 17/02/2031, Aero-braked, 22.5S 02. 17/02/2031, Not aero-braked, 12.5N 02. 17/02/2031, Not aero-braked, 12.5S 02. 17/02/2031, Not aero-braked, 21N 02. 17/02/2031, Not aero-braked, 22.5S 03. 16/04/2033, Aero-braked, 12.5N 03. 16/04/2033, Aero-braked, 12.5S 03. 16/04/2033, Aero-braked, 21N 03. 16/04/2033, Aero-braked, 22.5S 03. 16/04/2033, Not aero-braked, 12.5N 03. 16/04/2033, Not aero-braked, 12.5S Mission scenario Figure 2-38: 40-day-plus surface opportunities, using a solar cell power system 03. 16/04/2033, Not aero-braked, 21N 03. 16/04/2033, Not aero-braked, 22.5S 04. 27/06/2035, Aero-braked, 12.5N 04. 27/06/2035, Aero-braked, 12.5S 04. 27/06/2035, Aero-braked, 21N 04. 27/06/2035, Aero-braked, 22.5S 04. 27/06/2035, Not aero-braked, 12.5N 04. 27/06/2035, Not aero-braked, 12.5S 04. 27/06/2035, Not aero-braked, 21N 04. 27/06/2035, Not aero-braked, 22.5S 05. 15/08/2037, Aero-braked, 12.5N 05. 15/08/2037, Aero-braked, 12.5S 05. 15/08/2037, Aero-braked, 21N 05. 15/08/2037, Aero-braked, 22.5S 05. 15/08/2037, Not aero-braked, 12.5N 05. 15/08/2037, Not aero-braked, 12.5S HMM Assessment Study Report: CDF-20(A) February 2004 page 77 of 422 Figure 2-39 shows the timeline for the architecture selected for the study case; 2033 opportunity, no aerobraking, and fuel cells as power generation on the surface. There are two surface opportunities greater than 40 days in length: 202 and 218 days. Power Power Power out out out Insufficient power (Martian winter) Superior conjunction Global dust storms possible Mars surface operations possible Currently selected TMI date 16/04/2033 Mission breakdown and surface opportunities for the selected TMI launch date Mission scenario: E-M launch date = 16/04/2033, Aero-braking = no (0 days), Landing site latitude = Any, Power system = fuel cells Points to consider: - An assembly time of 4.5 years is assumed, including an in-orbit commissioning time of 90 days - The conjunction blackout is taken as 10° on either side of the actual conjunction - The TMI and TEI launch dates are the optimum cases. The launch window extends for 10 days on either side of this date - Surface operations can only take place outside the dust storm season, when there is no superior conjunction of Earth and Mars and when their is sufficient solar flux to provide the requisite power. Surface opportunities: Opp 1: 01/01/2034 to 22/07/2034 (201.8 days) Opp 2: 15/09/2034 to 21/04/2035 (218.7 days) Dust storms Assembly time Jun-2023 Jun-2025 Jun-2027 Jun-2029 Jun-2031 Jun-2033 Jun-2035 Jun-2037 Jun-2039 Dust storms Commissioning E-M transfer Dust storms Figure 2-39: Mission timeline Several conclusions can be drawn from the surface opportunities assessment: • Generally, aerobraking is not recommended. If it is required it should be aimed to reduce the duration to the order of six months. For longer durations the landing opportunities are reduced, even non existing. • When solar arrays are used as power generators on the surface, the opportunities are reduced and constrained by the landing latitude. This implies that some latitudes will not Stay at Mars Dust storms M-E transfer Dust storms Dust storms 05. 15/08/2037, Not aero-braked, 21N 05. 15/08/2037, Not aero-braked, 22.5S
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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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Page 25 and 26: s 2.2.4.2 Accelerations HMM Assessm
Page 27 and 28: s 2.2.4.4 Temperature and relative
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Page 33 and 34: s Figure 2-10: Trajectory Overview
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Page 45 and 46: s Mars Excursion Vehicle Transfer H
Page 47 and 48: s 2.7.5.1 Mission elements dry mass
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Page 51 and 52: s Total mission time (days) 1200 10
Page 57 and 58: s stack 9 Propellant mass of the ne
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Page 67 and 68: s 2.7.7.1.3 Mars excursion module S
Page 69 and 70: s 2.7.7.1.4 Earth return capsule HM
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Page 87 and 88: s 2.7.15 Sensitivity analysis HMM A
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Page 93 and 94: s Parameters used: • No Shuttle
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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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s 3.3.5 AOCS HMM Assessment Study R
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s Configuration Length (m) Total ma
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s 3.3.5.5 ACS for TMI 1 st HMM Asse
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s 3.3.6.2 Baseline design HMM Asses
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s 5 Reduce 2dB pointing precision t
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s 70-m antenna 70-m antenna 3.3.7.5
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s Angular separation SEM > 10º SEM
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s Figure 3-63: Communications MEV/M
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s Element 1: Transfer Habitation Mo
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s Radiation Shielding Shielding Req
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s The propulsion system and its cha
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s Item Nr. Mass [kg] Margin [%] Mas
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s 3.4.4 Mechanisms HMM Assessment S
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s 4 MARS EXCURSION VEHICLE 4.1 Syst
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s Figure 4-2: Option 2: Vertical co
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s 4.3 Surface habitation module Fig
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s Figure 4-11: Section through the
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s 4.3.1.5.3 Top level Figure 4-20:
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s Schedule in hours for the most ac
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s 4.3.3.6 Waste production HMM Asse
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s Figure 4-26: Total pressure vs. O
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s ECLS system mass: Figure 4-27: Ma
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s Figure 4-28: Mars albedo (L), ars
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s sun flux (W/m2) 450 400 350 300 2
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s Insulation structure (external) F
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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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