THEMIS FDMO Review Propellant Budget Update − 1 October 5, 2004 PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations Maneuver Calculator  V & ACS fuel budget Liens and recovery plans

THEMIS FDMO Review Propellant Budget Update − 2 October 5, 2004 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%

THEMIS FDMO Review Propellant Budget Update − 3 October 5, 2004 Probe Mass History Probe Dry Mass Trending and Status –Not to Exceed (NTE) = 80.8 kg –Allocation = kg –Current Best Estimate (CBE) = 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 #8 Pressurant Tank (38.7 kg to 48 kg fuel, 867m/s) SCN #CDR Reduce NTE dry mass to 80.8kg Towards a higher deltaV (910m/s) needed ? (regulate) ? (shed mass)

THEMIS FDMO Review Propellant Budget Update − 4 October 5, 2004 Instrument Mass History ? (EFI AXB full descope on 3 probes =3.4kg)

THEMIS FDMO Review Propellant Budget Update − 5 October 5, 2004 Bus Mass History 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 (?) PDRCDRrepress Regulate?

THEMIS FDMO Review Propellant Budget Update − 6 October 5, 2004 Dry mass allocation of 80.8kg with Isp=222s gives 910m/s with 4kg of ACS Propellant Status

THEMIS FDMO Review Propellant Budget Update − 7 October 5, 2004 Allocations Maneuver Calculator  V & ACS fuel budget Liens and recovery plans

THEMIS FDMO Review Propellant Budget Update − 8 October 5, 2004 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 P1P2P3P4P5P3->P1  V w/o inefficiencies 618m/s490m/s463m/s 599m/s665m/s  V w/ inefficiencies 670m/s520m/s491m/s 703m/s729m/s %  V fuel inefficiency 9.7%7%6.8% 20.2%11.2% ACS fuel3.22kg3.05kg3.09kg 4.78kg4.21kg

THEMIS FDMO Review Propellant Budget Update − 9 October 5, 2004 Maneuver calculator: inefficiencies considered  V 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

THEMIS FDMO Review Propellant Budget Update − 10 October 5, 2004 Maneuver calculator:  V and ACS inefficiencies considered

THEMIS FDMO Review Propellant Budget Update − 11 October 5, 2004 Allocations Maneuver Calculator  V & ACS fuel budget Liens and recovery plans

THEMIS FDMO Review Propellant Budget Update − 12 October 5, 2004 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 P1P2P3P4P5P3->P1* Oct 19, 2006 launch, approximate 729m/s475m/s417m/s418m/s(see FDMO Thu, 6/17/06) 690m/s (from C3+T1)

THEMIS FDMO Review Propellant Budget Update − 13 October 5, 2004 P1P2P3P4P5P3->P1  V w/o inefficiencies 618m/s490m/s463m/s 579m/s665m/s  V w/ inefficiencies 670m/s520m/s491m/s 662m/s729m/s %  V fuel inefficiency 9.7%7%6.8% 14.3%11.2% ACS fuel3.22kg3.05kg3.09kg 4.58kg4.21kg DeltaV, ACS Status –Step #3: Deterministic inefficiencies and ACS fuel (get as percentage from maneuver calculator). –Step #4 Summary P1P2P3P4P5P3->P1  V from GTDS 729m/s475m/s417m/s418m/s(see FDMO Thu, 6/17/06) 690m/s (from C3+T1)  V w/ deterministic inefficiencies 800m/s520m/s491m/s 662m/s729m/s ACS fuel3.22kg3.05kg3.09kg 4.58kg4.21kg RCS gives at this ACS fuel930 m/s935 m/s934 m/s 895 m/s905 m/s Margin required at launch15 %  V Margin to CBE available 16.3%80%90% 35%24%

THEMIS FDMO Review Propellant Budget Update − 14 October 5, 2004 Allocations Maneuver Calculator  V & ACS fuel budget Liens and recovery plans

THEMIS FDMO Review Propellant Budget Update − 15 October 5, 2004 Known performance liens and possible 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