bob g. beaman may 13-17, 2002

Final Version

Bob G. BeamanMay 13-17, 2002

Micro-Arcsecond Imaging Mission, Pathfinder (MAXIM-PF)

Electrical Power System (EPS)

MAXIM-PF, May 13-17, 2002Goddard Space Flight Center

Electrical Power System

Final Version

EPS Summary

The Phase I Hubcraft is undeployed Single Hub spacecraft attached to the Six FreeFlyer spacecraft.

The EPS for the Hubcraft is a distributed EPS with 10 ah LiIon batteries in each Spacecraft. Three sun side FreeFlyer spacecraft solar arrays are enough power to provide the Hubcraft power requirement.

Batteries are provided for Launch loads and contingency.

Technology areas that should be available by 2015 are: Distributed EPS, 35% eff Quad Junction solar cells, EPS Autonomy and use of Structural Batteries.

Solar Array Temp was assumed at 105 deg C.

MAXIM Pathfinder to full MAXIM. Solar array size increase by 1.4%

from 5 to 7 years additional life. Unused EPS margin may provide this. With no S/A increase full operational

requirements can accomplished except for 53 days during the 6th year and 71 days during the 7th year.

Use of 35% efficient solar cells would provide this and reduce solar array area.

Beginning Of Life (BOL) Solar Array power can accommodate up to 41.5 deg off pointing for the first year with decreasing angles as the solar array degrades.



Final Version

EPS Conclusions

There are no Big EPS show stoppers.

Dual Cosine angles are used. First +/- 30 degrees comes from an instrument requirement. And +/- 15 degrees is needed the Phase II operation to avoided one FreeFlyer from shadowing the other when they are in the same plane with the sun.

The Phase I mission Hubcraft requires 3.72 M2 from 3 FreeFlyer Spacecrafts. Each FreeFlyer Spacecraft requires 1.25 M2 for the Phase II mission which is just slightly larger. The design goal was to keep the Phase I Hubcraft solar array size to be equal for less that the 3 FreeFlyer Phase II size.

Further analysis or additional development may increase the Phase I Hubcraft solar array size. If that happens, the sun lead FreeFlyer will need additional solar panels each adjacent side. Higher efficient (35%) solar cells can be used.

Final Version

EPS Detail Charts





Final Version

Electrical Power System Driving Requirements & Assumptions

Launch: 21 July 2015

Orbit: L2. No eclipses

Life: 2 year Phase I3 year Phase II

Battery: For Launch and contingency

Solar Array: Needed to provide Power for loads. Solar Array temp 105 deg C.



Final Version

Electrical Power System Options Considered

Deployed Solar Array. A body mounted Solar Array size was achievable so solar array deployments were eliminated.

Phase I “sun lead” FreeFlyer adjacent side solar panels were not needed. The Phase II FreeFlyer solar Array size was large enough to be used as one third of the Phase I Hubcraft solar array.

Baseline a distributed EPS for the Phase I Hubcraft. The distributed EPS needs to be broken up for Phase II mission phase for individual FreeFlyer spacecraft and Hub spacecraft operation.



Final Version

Electrical Power System Selected Configuration & Rationale

Use of 28% Tj GaAs solar cells. Provides enough power and will be a mainstay for 2015 launch. By 2015 35% QjGaAs cells may be available.

Use of LiIon battery. For launch loads and contingency in L2.

MAP type PSE, however must be modified to provide Distributed EPS functions. A Voltage regulated bus is recommended over a Battery Dominated Bus.

Final Version

Detector Spacecraft Phase I & II EPS Baseline





Final Version

Detector Spacecraft Load AnalysisLAI MAXIM-Detector Spacecraft

5.0 Mission Life in Years

Nominal Mode Day

Nominal Mode Night

Safe Hold

EPS Load Item Description Avg. Power Watts

Avg. Power Watts

Power in Watts

Peak Power Launch Power Requirement

Total Power 743.1 743.1 148.6 1,190.3 148.6Time Period Over Which Averaging Is Done For Each Mode (min.) Contingency

Inst Global Contingency 20

Instruments with Contingency 300.0 300.0 60 450.0 60.0

X-ray CCD 50.0 50.0 10.0 75.0 10.0Contingency 20 10.0 10.0 2.0 15.0 2.0

Super Star Tracker (ISAL) 200.0 200.0 40.0 300.0 40.0Contingency 20 40.0 40.0 8.0 60.0 8.0

Instrument #3 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0




Spacecraft Loads with Contingency 443.1 443.1 88.6 740.3 88.6

Spcft Global Contingency 20

PSE MAP like (95.4% eff) 34 34.0 34.0 6.8 51.0 6.8Contingency 20 6.8 6.8 1.4 10.2 1.4

Electrical - Harness Losses BGB 4.3 4.3 0.9 6.4 0.9Contingency 20 0.9 0.9 0.2 1.3 0.2

Command & Data Handling Terry S. (generic) 28.0 28.0 5.6 42.0 5.6Contingency 20 5.6 5.6 1.1 8.4 1.1

Solid State Data Recorder N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Solar Array Drive Motor N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Attitude Control Eric S. 60.0 60.0 12.0 90.0 12.0Contingency 30 18.0 18.0 3.6 27.0 3.6

Com, X-Band HGA (2) (gimbales) Ron V. 1.0 1.0 0.2 16.0 0.2Contingency 20 0.2 0.2 0.0 3.2 0.0

Com, X Band Xpndr Ron V. 25.0 25.0 5.0 42.0 5.0Contingency 20 5.0 5.0 1.0 8.4 1.0

Com, S Band Xpndr Ron V. 22.0 22.0 4.4 22.0 4.4Contingency 20 4.4 4.4 0.9 4.4 0.9

Com, S Band HPA Ron V. 40.0 40.0 8.0 40.0 8.0Contingency 20 8.0 8.0 1.6 8.0 1.6

Thermal Dan N. & Wes O. 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Propulsion Bob E. 150.0 150.0 30.0 300.0 30.0Contingency 20 30.0 30.0 6.0 60.0 6.0



Final Version

Detector Spacecraft EPS Curve

LAI MAXIM-Detector Spacecraft Mission Over 5 Yr Life With Deployable Panel; 28% Eff Cells; Average Load During Day=743.1W; Average

Load During Night=743.1W

750

800

850

900

950

1000

1050

1100

0 365 730 1095 1460 1825

Mission Time (Days)

Daylight Average Solar Array Power Provided

Daylight Average Solar Array Power Required



Final Version

Detector Spacecraft Summary

Total Total

Dimensions (M) # Area or Vol Mass(Kg) Cost

Solar Array TJ GaAs 1 4.03 17.80 $2,016

Battery LiI on 10 0.19 0.13 0.08 1 0.00 5.76 $13

PSE MAP like 0.43 0.28 0.22 1 0.03 14.00 $750

Electrical Cable 2.52 $6

Total Materials $2,785Man Yr

Hardware Design/Procurement 10 $1,640

EPS I ntegration 2 $240

EPS Launch Site Support 1 $120

Grand Total 40.08 $4,785

Final Version

HubCraft Phase I EPS Baseline





Final Version

Hubcraft Load Analysis

LAI MAXIM-Hubcraft, Phase I5.0 Mission Life in Years

Nominal Mode Day

Nominal Mode Night

Safe Hold


Avg. Power Watts

Power in Watts


Total Power 661.7 661.7 132.3 955.4 132.3Time Period Over Which Averaging Is Done For Each Mode (min.) Contingency


Instruments with Contingency 137.4 137.4 27.48 206.1 27.5

75 Module @1.46w/module 109.5 109.5 21.9 164.3 21.9Contingency 20 21.9 21.9 4.4 32.9 4.4

Beacons @ 5w 5.0 5.0 1.0 7.5 1.0Contingency 20 1.0 1.0 0.2 1.5 0.2

Star Teacker @ 10.0w off 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Laser Ranging @ 15w off 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Special Processor @ 5w off 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Instrument #6 N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0





Command & Data Handling Terry S (previous #) 28.0 28.0 5.6 42.0 5.6Contingency 20 5.6 5.6 1.1 8.4 1.1



Solar Array Drive Electronics N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0


Com, S/UHF-band Transponder (2) Ron V. 22.0 22.0 4.4 22.0 4.4Contingency 20 4.4 4.4 0.9 4.4 0.9

Com, S-Band HPA (2) Ron V. 40.0 40.0 8.0 40.0 8.0Contingency 20 8.0 8.0 1.6 8.0 1.6

Com, N/A N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0





Final Version

Hubcraft EPS Curve

LAI MAXIM-Hubcraft, Phase I Mission Over 5 Yr Life With Deployable Panel; 28% Eff Cells; Average Load During Day=661.716W; Average

Load During Night=661.716W

600

700

800

900

1000

0 365 730 1095 1460 1825

Mission Time (Days)



Final Version

Hub Spacecraft Phase II EPS Baseline





Final Version

Hub Spacecraft Load AnalysisLAI MAXIM-Hub Spacecraft, Phane II


Nominal Mode Day

Nominal Mode Night

Safe Hold


Avg. Power Watts

Power in Watts





9 Modules @ 1.46w/module 13.1 13.1 2.6 19.7 2.6Contingency 20 2.6 2.6 0.5 3.9 0.5

Lisa Laser 18.0 18.0 3.6 27.0 3.6Contingency 20 3.6 3.6 0.7 5.4 0.7

Beacon 5.0 5.0 1.0 7.5 1.0Contingency 20 1.0 1.0 0.2 1.5 0.2











Solar Array Drive Electronics N/A 0.0 0.0 0.0 0.0 0.020 0.0 0.0 0.0 0.0 0.0


Com, S/UHF-band Omni Antennas (4)Ron V. 22.0 22.0 4.4 22.0 4.4Contingency 20 4.4 4.4 0.9 4.4 0.9

Com, S-Band HPA (2) Ron V. 40.0 40.0 8.0 40.0 8.0Contingency 20 8.0 8.0 1.6 8.0 1.6






Final Version

Hub Spacecraft EPS Curve

LAI MAXIM-Hub Spacecraft, Phane II Mission Over 5 Yr Life With Deployable Panel; 28% Eff Cells; Average Load During Day=276.516W; Average Load During Night=276.516W

200

250

300

350

400

450

0 365 730 1095 1460 1825

Mission Time (Days)





Final Version

Hub Spacecraft Summary

Total Total


Solar Array TJ GaAs 1 1.50 6.62 $750

Battery LiI on 10 0.19 0.13 0.08 1 0.00 5.76 $13

PSE MAP like 0.43 0.28 0.22 1 0.03 14.00 $750







Final Version

FreeFlyer Spacecraft Phase II EPS Baseline





Final Version

FreeFlyer Spacecraft Load AnalysisLAI MAXIM-FreeFlyer Spacecraft, Phase II


Nominal Mode Day

Nominal Mode Night

Safe Hold


Avg. Power Watts

Power in Watts





11 Modules @1.46w/module 16.1 16.1 3.2 24.1 3.2Contingency 20 3.2 3.2 0.6 4.8 0.6

Star Tracker (Use ones in ACS) 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0

Laser Ranging 15.0 15.0 3.0 22.5 3.0Contingency 20 3.0 3.0 0.6 4.5 0.6

Special Processor 5.0 5.0 1.0 7.5 1.0Contingency 20 1.0 1.0 0.2 1.5 0.2








N/A N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0


Solar Array Drive Electronics N/A 0.0 0.0 0.0 0.0 0.0Contingency 20 0.0 0.0 0.0 0.0 0.0


Com, UHF xnpndr Ron V. 10.0 10.0 2.0 10.0 2.0Contingency 20 2.0 2.0 0.4 2.0 0.4







Final Version

FreeFlyer Spacecraft EPS Curve

LAI MAXIM-FreeFlyer Spacecraft, Phase II Mission Over 5 Yr Life With Deployable Panel; 28% Eff Cells; Average Load During Day=220.2W;

Average Load During Night=220.2W

50

100

150

200

250

300

350

400

0 365 730 1095 1460 1825

Mission Time (Days)





Final Version

FreeFlyer Spacecraft Summary

Total Total


Solar Array TJ GaAs 1 1.25 5.5 $625

Battery LiI on 10 0.19 0.13 0.08 1 0.00 5.76 $13

PSE MAP like 0.43 0.28 0.22 1 0.03 14.00 $750









Final Version

EPS Technology Required

A distributed EPS system must be developed. Recommend the use of a voltage regulated system with distributed batteries and solar arrays.

By 2015 Quad junction gallium arsine (QjGaAs) solar cells at 35% efficiency would be available and can reduce mass but may increase cost and have life concerns.

Use of a Structural Battery would decrease mass. This technology should be available by 2015.



Final Version

EPS Requirements Verification.

Standard verification for PSE and Solar Array. A life test should be done on the battery design to ensure it

will meet the cycle life requirement with normal eclipse seasons.



Final Version

Electrical Power System Additional Trades to Consider

Scrub the load analysis to reduce the solar array size and battery ampere-hour requirement.

Trade Battery Dominated Bus (BDB) vs Voltage Regulated Bus (VRB) for a distributed bus design.

Peaking analysis, This EPS design has limited extra solar array due to full sun orbit and no

battery recharge requirements. Battery Life Test characteristics. Cable harness inductive characteristics that will choke the peak current. Use of a ultra capacitor near the peaking load device so harnessed do not see

peak currents. Look at propulsion orbit adjust maneuver and the power that is available.



Final Version

Electrical Power System Issues and Concerns

None

bob g. beaman may 13-17, 2002

Documents