THEMIS FDMO Review Propellant Budget Update − 1 October 5, 2004 PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations

THEMIS FDMO Review Propellant Budget Update − 1October 5, 2004

PROPELLANT BUDGET UPDATE

Vassilis Angelopoulos

Covered in this presentation:

• Allocations• Maneuver Calculator • 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)

• Total dry margin: 14.56%

PCA WET MASS vs. LV CAPABILITY

340.00

440.00

540.00

640.00

740.00

840.00

940.00

Date

Ma

ss

(k

g)

LV Capability

PCA Wet Mass Allocation

PCA Wet Mass CBE


PROBE DRY MASS

58.00

62.00

66.00

70.00

74.00

78.00

82.00

86.00

PhaseA

8/03 10/03 12/03 2/04 4/04 6/04 8/04

Ma

ss

(kg

)

Probe Dry Mass NTE

Probe Dry Mass CBE

Probe Dry Mass Allocation

Probe Mass HistoryProbe 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 #8 Pressurant Tank(38.7 kg to 48 kg fuel, 867m/s)

SCN #CDR Reduce NTE dry mass to 80.8kgTowards a higher deltaV (910m/s) needed

? (regulate)

? (shed mass)


INSTRUMENT MASS

18.00

19.00

20.00

21.00

22.00

23.00

24.00

25.00

PhaseA

8/03 10/03 12/03 2/04 4/04 6/04 8/04

Mas

s(kg

)

Instrument Allocation

Instrument CBE

Instrument Schedule

Instrument Mass History

? (EFI AXB

full descope on 3 probes =3.4kg)


Bus Mass HistorySPACECRAFT MASS

40.00

42.00

44.00

46.00

48.00

50.00

52.00

54.00

PhaseA

8/03 10/03 12/03 2/04 4/04 6/04 8/04

Mas

s (

kg)

Probe Allocation

Probe CBE

Probe Schedule

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 (?)

PDR CDRrepress Regulate?


dV versus dry mass characteristics(for ACS fuel, kg)

600

700

800

900

1000

1100

1200

1300

60 62 64 66 68 70 72 74 76 78 80 82 84 86Dry mass (kg)

del

taV

(m

/s)

0 4 6

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

Propellant Status




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

P1 P2 P3 P4 P5 P3->P1

V w/o inefficiencies 618m/s 490m/s 463m/s 463m/s 599m/s 665m/s

V w/ inefficiencies 670m/s 520m/s 491m/s 491m/s 703m/s 729m/s

% V fuel inefficiency 9.7% 7% 6.8% 6.8% 20.2% 11.2%

ACS fuel 3.22kg 3.05kg 3.09kg 3.09kg 4.78kg 4.21kg


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


95%0.5 100% 1%2.0 100% 3%30 (+/-)deg28 deg

2%0.32 1.149 14.3110.03 mCM Offset from radial thruster plane=

Inefficiencies

Radial misalignment (deg;%ineff)=

Side thrust angle=

Beta angle=

Finite arc (%/deg-ma)=

Reor fuel (grams/deg)=

Thruster mismatch (%)=

Axial misalignment (deg;%ineff)=

MAG deply EFI deploy

rleboeuf 0.082 0.871D.P.,V.A. 0.066 0.907 P1 P2 P3 P4 P5 P3->P1

rleboeuf 0.707 0.480 0.866 0.866 0.778

D.P.,V.A. 0.360 0.185 0.844 0.844 1.738 0.270

rleboeuf 1.278 1.275 1.109 1.109 1.291

D.P.,V.A. 1.892 1.892 1.272 1.272 2.073 2.968rleboeuf 2.937 2.707 2.928 2.928 3.022D.P.,V.A. 3.225 3.050 3.088 3.088 4.784 4.211

ACS FUEL SUMMARY (kg)

SUM=

reor

s

Maneuver calculator:V and ACS inefficiencies considered




DeltaV, ACS StatusDeltaV 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

Probe Operational Parameter P1 P2 P3 P4 P5 P3->P1

Base delta-V Total (m/sec) 618 490 472 472 579 665

Associated Maneuver Propellant Used 23.38 17.95 17.24 17.24 21.71 25.43

Attitude and Spin Control Propellant Used 3.22 3.05 3.07 3.07 4.58 4.20

Base Propellant Subtotal 26.60 20.99 20.31 20.31 26.29 29.64

Reserve Propellant Subtotal 6.12 4.56 4.09 4.09 6.61 6.27

Limit Fuel Mass 48.00 48.00 48.00 48.00 48.00 48.00

Probe Number

Delta-V Propellant

P1 P2 P3 P4 P5 P3->P1*

Oct 19, 2006 launch, approximate

729m/s 475m/s 417m/s 418m/s (see FDMO

Thu, 6/17/06)

690m/s

(from C3+T1)


P1 P2 P3 P4 P5 P3->P1

V w/o inefficiencies 618m/s 490m/s 463m/s 463m/s 579m/s 665m/s

V w/ inefficiencies 670m/s 520m/s 491m/s 491m/s 662m/s 729m/s

% V fuel inefficiency 9.7% 7% 6.8% 6.8% 14.3% 11.2%


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

– Step #4 Summary

P1 P2 P3 P4 P5 P3->P1

V from GTDS 729m/s 475m/s 417m/s 418m/s (see FDMO

Thu, 6/17/06)

690m/s

(from C3+T1)

V w/ deterministic inefficiencies

800m/s 520m/s 491m/s 491m/s 662m/s 729m/s


RCS gives at this ACS fuel 930 m/s 935 m/s 934 m/s 934 m/s 895 m/s 905 m/s

Margin required at launch 15 % 15% 15% 15% 15% 15%

V Margin to CBE available 16.3% 80% 90% 90% 35% 24%




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 toavoid over-pressurization of hydrazine tank in case of inadvertent pyroactuation 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-runnature 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 P1at a loss for P4/5. If excessive this might affect differential precession, butfor 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

Documents

THEMIS FDMO Review Propellant Budget Update − 1 October 5, 2004 PROPELLANT BUDGET UPDATE Vassilis Angelopoulos Covered in this presentation: Allocations