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Technical Resource Allocations

Technical Resource Allocations. Michael Pryzby. Technical Resource Allocations Flight Dynamics. Delta V Propellant. dV/Fuel Mass Allocation. Assumes 1480 kg wet launch mass MRD-24: The launch vehicle must be capable of delivering a 1480 kg payload to a trajectory with a C3 > -1.85

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Technical Resource Allocations

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  1. Technical Resource Allocations Michael Pryzby

  2. Technical Resource AllocationsFlight Dynamics Delta V Propellant

  3. dV/Fuel Mass Allocation • Assumes 1480 kg wet launch mass • MRD-24: The launch vehicle must be capable of delivering a 1480 kg payload to a trajectory with a C3 > -1.85 • Given dV budget, determine fuel mass assuming maximum wet mass at liftoff • Derives allocation for spacecraft dry mass • dV budget determined by analysis & lunar mission experience • MCC1 allocation is 3-sigma, could be improved by performing maneuver earlier than 24 hours but holding worst case • MRD-25: TLI accuracy at orbiter sparation from the LV third stage shall be within +/- 3 m/sec (TBR) (3-sigma) of target inertial velocity. • FDS 2.3.1: LRO shall perform an MCC1 maneuver at L+24 (TBD) hours to correct for LV dispersions. • LOI allocation is deterministic, detailed analysis exists to support, all physics not a function of perturbations • Stationkeeping is deterministic, detailed analysis exists to support, actual dV cost is only 150 m/sec, may move extra 30 m/s to margin • MRD-12: The primary mission shall be conducted in a circular mapping orbit with a nominal mean altitude of 50 +/- 20 km (altitude is measured to mean lunar surface). • Extended mission is place holder only, allows many options for unknown extended mission, could be used for contingency in mission orbit if needed • MRD-22: LRO shall carry sufficient consumables to allow for a four year extended mission in a low maintenance orbit. • Margin is 20 m/s • LOI and extended mission dV should not be used to calculate dV percent margin • 8% dV margin on MCC1 and SK dV budgets (22% if 30 m/s moved from SK to margin)

  4. Mission Phase LRO Baseline dV (m/sec) Fuel Mass (kg)  Comments  MCC 75 52 3s, MCC @ L+24 hours Lunar Insertion – 1st burn 391 210 1st insertion burn, finite dV, any launch date, 20% off-pulsing Lunar Insertion – All other burns 535 288 All other insertion burns, finite dV Station-keeping 180 77 +/- 20 km altitude, 3s including errors Extended Mission 125 48 Placeholder only Margin 20 8 Momentum Unloading 16 Other 14 De-spin, Residuals, Pressurant Total 1326 713 dV/Fuel Mass Allocation * Assumes 1480 kg launch wet mass

  5. Technical Resource AllocationsMass Consumables Spacecraft Wet Mass Spacecraft Dry Mass

  6. Mass • Technical Resource Allocations Document, 431-SPEC-000112 • Mass allocations budges include: • Spacecraft Allocation – Wet • Spacecraft Allocation - Dry • Wet Mass Allocation (Consumables) • Allocation Derivations: • Spacecraft Wet Mass Allocation • MRD-1: The max allowable spacecraft mass – 1480 kg • MRD-24: The launch vehicle must be capable of delivering a 1480 kg payload to a trajectory with a C3 > -1.85 • Wet Mass Allocation • Derived from dV / Fuel Mass Allocation • Spacecraft Dry Mass Allocations • Derived from Current Best Estimates • Contingency based upon Design Maturity Factor

  7. Subsystem Components Allocation  Comments  SubSystem Mass (kg) Consumables 715.30 Propellant 713.0 Derived from Delta V budget - includes 3s Pressurant 2.3 Wet Mass Allocation - Consumables Table 3‑2 - Spacecraft Wet Mass Allocation - Consumables

  8. Subsystem Components Allocation  Comments SubSystem Mass (kg) L/V Wet Mass Capability 1480.00 MRD Req’t: 1.2.10 Derived Wet Mass Allocation 715.30 Propellant Budget derived from Delta V budget Max Dry Mass Allocation 764.70 Remaining mass Spacecraft Mass Allocation - Wet  Table 3‑1 - Spacecraft Mass Allocation - Wet Table 3‑2 - Spacecraft Wet Mass Allocation

  9. Subsystem Components Allocation  Comments SubSystem Mass (kg) Total Dry Mass 710.3 Concept J Spin balance Weight 25.0 Place holder S/C Bus Subtotal 595.5 Mechanical 155.1 Mechanisms 52.8 Thermal 32.4 Power 76.2 ACS 63.4 PDE 16.8 Propulsion (Dry Mass) 105.8 C&DH 19.5 S Comm 12.6 Ka Comm 18.5 Electrical 40.0 Instruments Subtotal 89.9 CRaTER 6.4 Diviner 11.9 LAMP 5.3 LEND 23.2 LOLA 15.3 LROC 19.0 Mini RF 12.6 Spacecraft Mass Allocation - Dry Table 3‑3- Spacecraft Mass Allocation - Dry

  10. Mass Allocation Summary • Margins meet GOLD requirement (20%) – 20.8% on CBE • Allocation – 710.3 kg • Current Best Estimate – 632.8 kg • Max Dry mass – 764.7 kg • System Margin – 54.4 kg (7.7%) • Or 79.4 kg (11.2%) including spin balance mass • Assume 1480 max LV capability

  11. Technical Resource AllocationsPower Un-Switched Power Instrument Heater Power Switched Power

  12. Power Allocations • Technical Resource Allocations Document, 431-SPEC-000112 • Power allocations include: • Un-Switched Power • Instrument Heater Power – Operational & Survival • Switched Power • Spacecraft Power Allocations • Switched and Un-Switched • Derived from Current Best Estimates • Contingency based upon Design Maturity Factor for each switch • Heater • Operational heater power allocations for each instrument/component are based on Beta=90° cold case orbit average predictions plus margin. • Survival heater power allocations for each instrument/component are based on Safe-hold orbit average predictions plus margin

  13. Power Allocation Driving Requirements • Worst Case is based on “S+Ka Orbit” mission phase from LRO Mission Concept of Operations Document, 431-OPS-000042 as documented in the Master Equipment List • Driving Requirements • Power System • MRD-103: System sized for 823W On-Orbit Average • Solar Array Properties • 1849W @ 35V • EOL properties for 14 month design life • Battery Spec • Max Depth of Discharge (DOD) is 30% • EOL properties for 18 month design life • Nominal 28V output • Energy Balance for Beta 0 case • 48 minute eclipse • full battery recharge in single orbit

  14. Power Allocation - Un-Switched Table 4‑1- Un-Switched Power Allocations

  15. Power Allocation – Instrument Heaters * - Current analysis shows no heater power is necessary  Table 4‑2 – Instrument Heater Power Allocations

  16. Power Allocation - Switched Table 4‑3 - Switched Power Allocations

  17. Power Allocation Summary • Margins meet GOLD requirement at SRR (15%) – 21% on CBE • On-Orbit Average designed for 823W power system (MRD-103) • Power Allocations set at 745W max for S+Ka Orbit, Beta 0 case • 10%+ margin on power system • Current Best Estimate for worst case power average is 680.4W • S+Ka Orbit from Mission Concept of Operations Plan • Margin = 21%

  18. Technical Resource AllocationsFlight Software Processor Memory 1553 Bus

  19. Data Allocations – Key Assumptions • 750 Processor or equivalent • GNC Software resident on Main Processor • Using cFE for core FSW • Interfaces include only: • 1553 bus interface • 1355 (Spacewire) • Baseline no science data processing/compression onboard

  20. Flight Software Allocation Summary * From GSFC-STD-1000 (GOLD Rules - FSW)

  21. LRO Processor Memory Utilization

  22. 1553 Allocation

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