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s HMM Assessment Study Report: CDF-20(A) February 2004 page 184 of 422 As regards power, the OEM mode does not need closer study. Indeed, the link with a platform providing the request power is assumed. This platform has not been designed in this study. During all the propulsion modes (TMIM, MOAM and TEIM), the mechanical load of the solar panels is too high. Therefore, the solar panels will be folded during these manoeuvres. For covering all these modes and also for safety purposes, the power system shall be able to supply the nominal required power for a duration of 6 hours without relying on the solar panels. 3.3.4.2.2 Power requirements In this study, the power requirements have been computed module per module, unit per unit and mode per mode. Each unit power profile is defined by 3 values: • a peak power • a standby power • a duty cycle value (duration of the peak power compared to the total duration) For every mode, the peak and standby values have been added to obtain values at system level. An equivalent duty cycle is also computed to keep the same level of energy (See Table 3-29). Table 3-29 also shows the power consumption requested for the MEV and the ERC modules. Table 3-29: Computation of power inputs The equivalent power profiles obtained are not realistic for all points of view. The system peak power (which consists of the sum of the individual unit peak power) is a worst case never reached. It corresponds to the case in which all the equipment is simultaneously: that is dishwasher, laundry, communications, thermal, heaters… Better insight in the power profiles cannot be obtained at this stage of the study.

s 3.3.4.3 Assumptions and trade-offs HMM Assessment Study Report: CDF-20(A) February 2004 page 185 of 422 3.3.4.3.1 Power generation: solar arrays The strategy is to first size a design without the use of nuclear technology. The high level of energy that has to be supplied implies that a power generation has to be included in the power system. Therefore, the use of photovoltaic cells is taken into account. Until now, it is the only non-nuclear power generation system used in spacecraft. In this field, important research is taking place on to increase the efficiency of the cells. Also, research is being don on the development of thin film cells that could fit on flexible or inflatable structures. Such technologies may be available in 2015. Nevertheless, their development and qualification may need more time than expected. Consequently, the design will be performed with three types of cells: • AsGa Multi-Junction Cells with the present state of art (Column 1 of Table 3-30): Efficiency AM0 (28ºC): 26.8%. At end of life, the efficiency drops to 17.73% • AsGa Multi-Junction Cells with the performances expected for 2015 (Column 2 of Table 3-30): Efficiency AM0 (28ºC): 32%. At EOL, this value is estimated at 25.85% • Thin-Film CIS Cells also projected in 2015 (Column of Table 3-30): 15% is assumed in AM0(28º) conditions. At the end of the mission it decreases to 12.94% AsGa Multi-Junction Cells AsGa Multi-Junction Cells ( 2015) illumination sunlight (worst case) 450 W/m2 Concentrator multiplier 1 net illumination 450.00 W/m2 Solar Cells net conversion efficiency temperature 70 C AM0 cell efficiency at 28C 26.80% temperature coefficient 0.07% at operating temperature 23.86% direct terms radiation 5% 95% 22.67% spectrum shift 0% 100% 22.67% light intensity effect on Voc 2% 98% 22.21% other 0% 100% 22.21% product of direct terms 93.10% 22.21% cell efficiency on Mars 22.21% Solar Array stat terms Mismatch 1% Calibration 5% Random failure 5% UV-micrometeorites 1% total stat terms 7.2% 92.8% 20.61% electrical Diode loss 2.5% 97.5% 20.10% Harness loss 2.0% 98.0% 19.69% optical Orientation loss (perp =>0%) 0.0% 100.0% 19.69% Packing factor loss 10.0% 90.0% 17.73% Shadow 0.0% 100.0% 17.73% summary mass Margin 0% 100.0% 17.73% conversion efficiency 17.73% including dust (last day) 0.00% mass / m2 2.90 kg/m2 79.76 W/m2 27.50 W/kg illumination sunlight (worst case) 450 W/m2 Concentrator multiplier 1 net illumination 450.00 W/m2 Solar Cells net conversion efficiency temperature -12 C AM0 cell efficiency at 28C 32.00% temperature coefficient 0.07% at operating temperature 34.80% direct terms radiation 5% 95% 33.06% spectrum shift 0% 100% 33.06% light intensity effect on Voc 2% 98% 32.40% other 0% 100% 32.40% product of direct terms 93.10% 32.40% cell efficiency on Mars 32.40% Solar Array stat terms Mismatch 1% Calibration 5% Random failure 5% UV-micrometeorites 1% total stat terms 7.2% 92.8% 30.06% electrical Diode loss 2.5% 97.5% 29.31% Harness loss 2.0% 98.0% 28.72% optical Orientation loss (perp =>0%) 0.0% 100.0% 28.72% Packing factor loss 10.0% 90.0% 25.85% Shadow 0.0% 100.0% 25.85% summary mass Margin 0% 100.0% 25.85% conversion efficiency 25.85% including dust (last day) 0.00% mass / m2 2.70 kg/m2 116.34 W/m2 43.09 W/kg Thin-Film CIS Cells (2015) illumination sunlight (worst case) 450 W/m2 Concentrator multiplier 1 net illumination 450.00 W/m2 Solar Cells net conversion efficiency temperature 7C AM0 cell efficiency at 28C 15.00% temperature coefficient 0.09% at operating temperature 16.89% direct terms Solar Array stat terms electrical optical summary mass radiation 2% 98% 16.55% spectrum shift 0% 100% 16.55% light intensity effect on Voc 2% 98% 16.22% other 0% 100% 16.22% product of direct terms 96.04% 16.22% cell efficiency on Mars 16.22% Mismatch 1% Calibration 5% Random failure 5% UV-micrometeorites 1% total stat terms 7.2% 92.8% 15.05% Diode loss 2.5% 97.5% 14.68% Harness loss 2.0% 98.0% 14.38% Orientation loss (perp =>0%) 0.0% 100.0% 14.38% Packing factor loss 10.0% 90.0% 12.94% Shadow 0.0% 100.0% 12.94% Margin 0% 100.0% 12.94% conversion efficiency 12.94% including dust (last day) 0.00% mass / m2 0.60 kg/m2 58.25 W/m2 97.08 W/kg Table 3-30: Comparison of multi-junction cells and thin-film cell power generation For compliance with the high level of load during the propulsion phases, the solar panels are mounted with a deployment and folding mechanism. Therefore, the polar platform solar arrays

s<br />

3.3.4.3 Assumptions and trade-offs<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 185 of 422<br />

3.3.4.3.1 Power generation: solar arrays<br />

The strategy is to first size a design without the use of nuclear technology. The high level of<br />

energy that has to be supplied implies that a power generation has to be included in the power<br />

system. Therefore, the use of photovoltaic cells is taken into account. Until now, it is the only<br />

non-nuclear power generation system used in spacecraft. In this field, important research is<br />

taking place on to increase the efficiency of the cells. Also, research is being don on the<br />

development of thin film cells that could fit on flexible or inflatable structures. Such<br />

technologies may be available in 2015. Nevertheless, their development and qualification may<br />

need more time than expected. Consequently, the design will be performed with three types of<br />

cells:<br />

• AsGa Multi-Junction Cells with the present state of art (Column 1 of Table 3-30):<br />

Efficiency AM0 (28ºC): 26.8%. At end of life, the efficiency drops to 17.73%<br />

• AsGa Multi-Junction Cells with the performances expected for 2015 (Column 2 of Table<br />

3-30):<br />

Efficiency AM0 (28ºC): 32%. At EOL, this value is estimated at 25.85%<br />

• Thin-Film CIS Cells also projected in 2015 (Column of Table 3-30):<br />

15% is assumed in AM0(28º) conditions. At the end of the mission it decreases to<br />

12.94%<br />

AsGa Multi-Junction Cells AsGa Multi-Junction Cells<br />

( 2015)<br />

illumination<br />

sunlight (worst case) 450 W/m2<br />

Concentrator multiplier 1<br />

net illumination 450.00 W/m2<br />

Solar Cells net conversion<br />

efficiency<br />

temperature 70 C<br />

AM0 cell efficiency at 28C 26.80%<br />

temperature coefficient 0.07%<br />

at operating temperature 23.86%<br />

direct terms<br />

radiation 5% 95% 22.67%<br />

spectrum shift 0% 100% 22.67%<br />

light intensity effect on Voc 2% 98% 22.21%<br />

other 0% 100% 22.21%<br />

product of direct terms 93.10% 22.21%<br />

cell efficiency on Mars 22.21%<br />

Solar Array<br />

stat terms<br />

Mismatch 1%<br />

Calibration 5%<br />

Random failure 5%<br />

UV-micrometeorites 1%<br />

total stat terms 7.2% 92.8% 20.61%<br />

electrical<br />

Diode loss 2.5% 97.5% 20.10%<br />

Harness loss 2.0% 98.0% 19.69%<br />

optical<br />

Orientation loss (perp =>0%) 0.0% 100.0% 19.69%<br />

Packing factor loss 10.0% 90.0% 17.73%<br />

Shadow 0.0% 100.0% 17.73%<br />

summary<br />

mass<br />

Margin 0% 100.0% 17.73%<br />

conversion efficiency 17.73%<br />

including dust (last day) 0.00%<br />

mass / m2 2.90 kg/m2<br />

79.76 W/m2<br />

27.50 W/kg<br />

illumination<br />

sunlight (worst case) 450 W/m2<br />

Concentrator multiplier 1<br />

net illumination 450.00 W/m2<br />

Solar Cells net conversion<br />

efficiency<br />

temperature -12 C<br />

AM0 cell efficiency at 28C 32.00%<br />

temperature coefficient 0.07%<br />

at operating temperature 34.80%<br />

direct terms<br />

radiation 5% 95% 33.06%<br />

spectrum shift 0% 100% 33.06%<br />

light intensity effect on Voc 2% 98% 32.40%<br />

other 0% 100% 32.40%<br />

product of direct terms 93.10% 32.40%<br />

cell efficiency on Mars 32.40%<br />

Solar Array<br />

stat terms<br />

Mismatch 1%<br />

Calibration 5%<br />

Random failure 5%<br />

UV-micrometeorites 1%<br />

total stat terms 7.2% 92.8% 30.06%<br />

electrical<br />

Diode loss 2.5% 97.5% 29.31%<br />

Harness loss 2.0% 98.0% 28.72%<br />

optical<br />

Orientation loss (perp =>0%) 0.0% 100.0% 28.72%<br />

Packing factor loss 10.0% 90.0% 25.85%<br />

Shadow 0.0% 100.0% 25.85%<br />

summary<br />

mass<br />

Margin 0% 100.0% 25.85%<br />

conversion efficiency 25.85%<br />

including dust (last day) 0.00%<br />

mass / m2 2.70 kg/m2<br />

116.34 W/m2<br />

43.09 W/kg<br />

Thin-Film CIS Cells (2015)<br />

illumination<br />

sunlight (worst case) 450 W/m2<br />

Concentrator multiplier 1<br />

net illumination 450.00 W/m2<br />

Solar Cells net conversion<br />

efficiency<br />

temperature 7C<br />

AM0 cell efficiency at 28C 15.00%<br />

temperature coefficient 0.09%<br />

at operating temperature 16.89%<br />

direct terms<br />

Solar Array<br />

stat terms<br />

electrical<br />

optical<br />

summary<br />

mass<br />

radiation 2% 98% 16.55%<br />

spectrum shift 0% 100% 16.55%<br />

light intensity effect on Voc 2% 98% 16.22%<br />

other 0% 100% 16.22%<br />

product of direct terms 96.04% 16.22%<br />

cell efficiency on Mars 16.22%<br />

Mismatch 1%<br />

Calibration 5%<br />

Random failure 5%<br />

UV-micrometeorites 1%<br />

total stat terms 7.2% 92.8% 15.05%<br />

Diode loss 2.5% 97.5% 14.68%<br />

Harness loss 2.0% 98.0% 14.38%<br />

Orientation loss (perp =>0%) 0.0% 100.0% 14.38%<br />

Packing factor loss 10.0% 90.0% 12.94%<br />

Shadow 0.0% 100.0% 12.94%<br />

Margin 0% 100.0% 12.94%<br />

conversion efficiency 12.94%<br />

including dust (last day) 0.00%<br />

mass / m2 0.60 kg/m2<br />

58.25 W/m2<br />

97.08 W/kg<br />

Table 3-30: Comparison of multi-junction cells and thin-film cell power generation<br />

For compliance with the high level of load during the propulsion phases, the solar panels are<br />

mounted with a deployment and folding mechanism. Therefore, the polar platform solar arrays

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