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PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations

PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations Maneuver Calculator d V & ACS fuel budget Liens and recovery plans. Launch mass versus CBE. LV capacity=829kg to current orbit 10% wet mass margin (12% dry) 1.43% wet mass contingency (2% dry)

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PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations

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  1. PROPELLANT BUDGET UPDATE • Vassilis Angelopoulos • Covered in this presentation: • Allocations • Maneuver Calculator • dV & ACS fuel budget • Liens and recovery plans

  2. Launch mass versus CBE • LV capacity=829kg to current orbit • 10% wet mass margin (12% dry) • 1.43% wet mass contingency (2% dry) • Total dry margin: 14.56%

  3. Probe Mass History Probe Dry Mass Trending and Status • Not to Exceed (NTE) = 80.8 kg • Allocation = 76.57 kg • Current Best Estimate (CBE) = 77.24 kg (note: September update is unofficial) • %Contingency (Allocation vs. CBE) = -0.86% • %Program Managers Margin (NTE vs. Allocation) = 5.52% • %Total Margin (NTE vs. CBE) = 4.61% SCN #1 Larger Tanks (34.5 kg to 38.7 kg fuel, 750m/s) SCN #CDR Reduce NTE dry mass to 80.8kg Towards a higher deltaV (910m/s) needed SCN #8 Pressurant Tank (38.7 kg to 48 kg fuel, 867m/s) ? (regulate) ? (shed mass)

  4. Instrument Mass History ? (EFI AXB full descope on 3 probes =3.4kg)

  5. Bus Mass History Regulate? PDR repress CDR Service valve regulation under investigation: Could provide ~3kg of dry mass (~back to CDR values) + 2% increase in Isp (~negates 3sigma errors in Isp) Mass reduction options under investigation: Reduce BAU thickness (~0.625kg) Lower S-band antenna (?) Self-balance booms (~0.75kg) Reduce RCS harness (?) Reduce cover glass thickness (-6mils = 0.550kg) Remove thermistors and redundant T-stats (?)

  6. Propellant Status Dry mass allocation of 80.8kg with Isp=222s gives 910m/s with 4kg of ACS

  7. Allocations • Maneuver Calculator • dV & ACS fuel budget • Liens and recovery plans

  8. Maneuver calculator, summary • Used since Phase A to perform orbit design • Tracks with Hohman transfers all (main) maneuvers, reors, total contingencies etc. • Now includes all deterministic inefficiencies • Still to include: Latest revision of MRD allocations, latest revision ascend profile. • However, total inefficiencies are a good measure of final deterministic inefficiencies

  9. Maneuver calculator: inefficiencies considered • dV inefficiencies [for P1, total=9.7%] • Side thrust finite pulse width: Isp degradation = sin(phi)/phi [2.7%] • Axial or radial thruster misalignment [0.2%] • Beta inefficiency (sin(beta) + cos(beta)) [2.3%] • Finite arc losses: 0-15% fuel loss for 0-7.5deg in mean anomaly (2% /deg-ma) [4.4%] • ACS inefficiencies [for P5, total=4.74kg] • Reor fuel with appropriate Izz (no booms deployed, w/MAGs, w/MAGs and EFI) [2.07kg] • Spin up fuel for MAG deploy and EFI deploy as appropriate [0.97kg] • Spin maintenance with separate burns [0.70kg] • - Compensate spin changes due to axial/radial thruster misalignment • CM offset from radial thruster plane resulting in torque [1.kg] • - Compensated by axial pulsing

  10. Maneuver calculator: dV and ACS inefficiencies considered

  11. Allocations • Maneuver Calculator • dV & ACS fuel budget • Liens and recovery plans

  12. DeltaV, ACS Status DeltaV and ACS fuel Status • Step #1: Maneuver Calculator (RevC2) • Step #2: Forward Runs (GTDS, from launch to orbit to de-orbit with accurate perturbations) * From maneuver calculator for P3 up to raise, and from GTDS for P1 raise up to end of T1

  13. DeltaV, ACS Status • Step #3: Deterministic inefficiencies and ACS fuel (get as percentage from maneuver calculator). • Step #4 Summary

  14. Allocations • Maneuver Calculator • dV & ACS fuel budget • Liens and recovery plans

  15. Known performance liens andpossible recovery options • A difficult mission design profile, but stable for chosen elements including dispersions. Any launch delay will affect fuel margins. Watching launch date very carefully. • Isp reduction by 1.5% due to range safety (reduce pressurant-tank pressure to avoid over-pressurization of hydrazine tank in case of inadvertent pyro actuation at the pad). With the solenoid valve this is assumed a non-issue. • Isp 3-sigma errors = +/-2.8% at average system pressure of 125psi. Not included here. Must use mission profile adjustments to recover. • Launch vehicle dispersions not included in GTDS now because of the forward-run nature of modeling. A 36m/s effect on P1 (or a 4% additional loss). Resolution:Ask LV to inject us higher (13Re) at a higher inclination (~10deg): helps P1 at a loss for P4/5. If excessive this might affect differential precession, but for now it only affects P4/5 margin. • Other delta V reduction steps not shown • Ask LV for RAAN=310deg (not 322deg) avoids T2 long shadows <- HELPED, WILL IMPLEMENT • Shadow avoidance maneuver still under investigation (GSFC/MESA looking at it) <- DIDN’T WORK • Go to a 3-day orbit for P1 (Science team looking at substorm yield) <- YIELD BELOW BASELINE • Slew maneuver at perigee (drives mission ops complexity but gives up to 4% back) <- COMPLEX

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