PROPELLANT BUDGET Vassilis Angelopoulos Covered in this presentation: Allocations

1. PROPELLANT BUDGET • Vassilis Angelopoulos • Covered in this presentation: • Allocations • Maneuver Calculator • dV & ACS fuel budget • Deterministic inefficiencies

2. MRD consistent with CBEs (TBR once Boeing gets on contract)

3. Launch mass versus CBE • LV capacity=829kg to current orbit • 17% wet mass margin (24% dry) • 5% wet mass contingency (7% dry)

4. Probe dry mass allocation versus CBE • Probe dry mass NTE=86kg (allows dV=867m/s and 4kg of ACS fuel) • 12% dry mass program manager’s margin (for emergencies or science) • 7% dry mass contingency • 20.2% dry mass reserve of NTE relative to CBE

5. Probe deltaV, ACS allocation Dry mass allocation of 76.6kg gives 922m/s with 5kg of ACS

6. 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

7. 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

8. Maneuver calculator: dV and ACS inefficiencies considered

9. Probe deltaV, ACS Summary • Probe dry mass NTE=86kg, allows dV=867m/s and 4kg of ACS fuel. • dV max estimate w/o inefficiencies = 628m/s (allows for ODA and 3s LV insertion errors) • dV allocation = 725m/s (allows 15% contingency relative to early predicts) • dV NTE = 825 m/s (allows 15% margin relative to allocation for operator errors) • Allocation exceeded by forward runs even without consideration of inefficiencies. • ACS fuel allocation of 4kg tracked separately • Allocation = 4kg violated by P5: Reallocation or lump ACS with dV immediately post CDR • SUMMARY • Adding deterministic inefficiencies (~10%) to Sabine’s forward run dV estimates (733m/s)brings total dV above allocation of 725m/s (806m/s) which reduces operator margin to 2.3% • Keep optimizing ascend. (Shadow avoidance mnvr, lower prg prior to d(inc), …) • Track probe mass very carefully • If probe mass does not exceed mass allocation (effectively becoming new NTE), then operator margin is: ~15% • Known risks • 1% loss of Isp (and fuel) from repress system pressure reduction to satisfy range safety • LV performance loss from allTLX, fairing doors, new Boeing data, may result in further inc increase which may have to be taken out by probes by fuel, resulting in further increase in dV • CONCLUSION: REALLOCATE NTE DRY MASS, TO HELP dV and PC MASS SIMULTANEOUSLY