. 

NASA Technical Memorandum 102102 

Lunar Production of Solar Cells 

Geoffrey A. Landis 

Lewis Research Center 

Cleveland, Ohio 

and 

Maria Antonietta Perino 

Aeritalia 

Space Systems Group, Research 

Torino- Corso Marche, Italy 

Prepared for the 

9th Biennial SSI/Princeton Conference on Space Manufacturing 

sponsored by Space Studies Institute 

Princeton, New Jersey, May 10-13, 1989 

{UASA-TH-l02102) LUNAR PBODUCTIOU OP SOLAR 189-276 19 

CEtLS tlli&Sa. Levis Research Center) 18 p CSCL 038 

Unclas 

G3/91 0224998 _- I 
LUNAR PRODUCTION OF SOLAR CELLS 

Geoffrey A. Landis* 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44 135 

and 

Maria Antonietta Perino 

Aeritalia 

Space Systems Group, Research 

10 146 Torino-Corso Marche, Italy 

The feasability of manufacturing of solar cells on the moon for 

spacecraft applications is examined. Because of the much lower escape 

velocity, there is a great advantage in lunar manufacture of solar cells 

compared to Earth manufacture. Silicon is abundant on the moon, and 

new refining methods allow it to be reduced and purified without extensive 

reliance on materials unavailable on the moon. Silicon and amorphous 

silicon solar cells could be manufactured on the moon for use in space. 

Concepts for production of a baseline amorphous silicon cell is discussed, 

and specific power levels calculated for cells designed for both lunar and 

Earth manufacture. 

'National Research Council-NASA Research Associate. 

1 
1. Introduction 

A first step toward realization of a lunar manufacturing base is to 

identify near-term products that could be manufactured on the moon for 

cost-effective use on-site and elsewhere. In this paper we discuss 

manufacture of photovoltaic solar arrays as one such product. 

A lunar base is projected to require 100 kW to 1 MW or more of power, 

and a mining and manufacturing facility considerably more. It is a natural 

assumption to require that a manufacturing facility produce from locally 

available materials the solar arrays for its own expansion in a "bootstrap" 

process. Once it is accepted that a lunar base may manufacture its own 

power source, it is a straightforward extrapolation to the lunar production 

of solar arrays for other uses, taking advantage of the greatly reduced 

transportation costs due to the lower escape velocity of the moon. 

The widely discussed manned Mars mission, for example, could 

require 1 MW or more. Transportation costs alone for a Mars power 

source could be on the order of a billion dollars. While these costs can be 

projected to decrease with the future availability of advanced launch 

systems and use of in-situ propellant production, the possible economic 

gains are nevertheless extremely large. This is a strong incentive for 

seeking ways of lowering transportation costs for the solar arrays. One 

route to doing this is to increase the array (and storage system) power to 

weight ratio ("specific power"). Another possibility is to manufacture the 

arrays in space. 

Most current plans for a lunar base assume that the base will include an 

industrial facility, primaril to produce oxygen for propulsion systems by 

reduction of the lunar soil $1. A second product for such a facility could be 

solar arrays. While the primary user of lunar- produced solar cells would 

undoubtably be the lunar base itself, there would be many markets. Figure 

1 shows some of these possible uses of lunar produced photovoltaics, 

including solar- electric propulsion for orbital transfer vehicles and for 

solar system exploration, and power systems for geosynchronous Earth 

orbit (GEO) and low Earth orbit (LEO) satellites. 

Use of lunar-manufactured solar cells for high-power solar-electric 

propulsion is an especial1 attractive option. Recent proposals for a 

manned Mars mission 61, for example, propose an unmanned, 

electric-propulsion cargo vehicle to ferry supplies to Mars orbit in advance 

of the crew on a low-thrust orbit. The power system for the electric 

propulsion is a 5 MW nuclear generator, which could be replaced with 

lunar-manufactured thin-film solar cells for a considerable savings in 

required weight to orbit. For a "sprint" mission, a high-power electric 

propulsion vehicles of 200 MW power and a specific impulse of 20,000 sec 

could make the round-trip to Mars as short as 7.5 months f21. 

Solar-electric transport vehicles would also greatly reduce the required 

mass for servicing the lunar base itself. B.G. Logan 131, for example, 

proposes a 6 MW Manned Lunar Shuttle powered by a pulsed plasma gun, 

2 
estimating tha this could halve the transport costs, even for relatively 

modest specific power solar arrays. 

Use of lunar material has also been wide1 proposed for manufacture of 

The cost of transportation from the Earth's surface to orbit and beyond 

can be quite high. Figure 2, for example, shows the cost of delivering 

conventional and advanced power systems to orbit, the moon, and Mars, 

using cost estimates typical of current technology space boosters. For 

example, a one-megawatt power system delivered to Mars could have 

transportation costs alone in the ten to hundred billion dollar range. While 

these costs are likely to be decreased with advanced transportation, they 

are likely to remain high. 

The advantage of lunar manufacture is that the escape velocity is only 

22% that of the Earth. Table 1-A shows the AV (velocity increment) 

needed to achieve various destinations from the Earth's surface and from 

the moon. The payload fraction decreases exponentially with the delta-V, 

and a much higher fraction of the lift-off mass can be useful payload, as 

shown in table 1-B, which shows the theoretical maximum fraction of 

lift-off mass which can achieve the listed orbit if launched from the Earth's 

surface, compared to launched from the moon. (Actual rockets never 

achieve these values; typically only 1-20? of the mass of a rocket launched 

from the Earth is useful payload.) Even to low Earth orbit, five times the 

payload can be delivered if launched from the moon than if launched from 

the Earth's surface. For the commercially valuable geosynchronous orbit, 

almost nine times the payload can be delivered. This is a strong leverage 

factor for lunar manufacture. 

The design criteria for lunar manufactured solar cells depends on the 

mission. The most important criteria for most missions are maximum 

power/weight ratio (specific power) and minimum usage of materials 

transported from Earth. For use on the lunar surface, specific power is not 

an important criterion. 

solar cells for satellite solar power stations [4 Y 

3. Lunar Materials 

3.1 Materials Availability 

Silicon is not only one of the most abundant elements on the Earth, it 

is also present in great quantity in the lunar soil. 

Table 2 shows the lunar abundance of materials important for 

production of solar cells 151. While high-efficiency solar cells can be made 

from a wide variety of semiconductors, lunar material scarcity rules out 

production of indium phosphide, gallium arsenide, copper indium 

selenide, or cadmium teluride solar cells, (Note, however, that the lunar 

surface has to date only been superficially examined, and that the 

possibility exists of mineral deposits with much greater concentrations 

than those listed here), The available semiconductor material is clearly 

silicon. Candidate solar cell types are crystalline silicon and amorphous 

silicon. 

Production of the structural elements of the array is also important, 
than those listed here). The available semiconductor material is clearly 

silicon. Candidate solar cell types are crystalline silicon and amorphous 

silicon. 

Production of the structural elements of the array is also important, 

and in fact contributes more than half of the total mass of the finished 

array. Materials for producing structural elements are available on the 

moon (4961. Aluminum is a major constituent of the lunar soil, and titanium 

is also available in varying amounts depending on location. Nearly pure 

nickel-iron can be obtained by magnetic separation of the small (1-2Vo) 

amounts of mejteoric material from the soil. Glass fiber can be 

manufactured from readily available lunar silica for use in composites [7*81. 

We further note that for a solar-powered moonbase it may also be 

important to manufacture from locally available materials a storage system 

to provide power for the 14-day lunar night. This is discussed in more 

detail in reference [9]. 

3.2 Silicon Production 

Although silicon is abundant (second most abundant element, after 

oxygen, in the lunar crust), typically hydrogen, carbon, and halogens are 

required for existing technologies of refining and purification, although it 

is reasonable to expect that a process sequence adapted to lunar 

conditions may minimize usage of these materials. Calculations show that if 

recycling efficiency is good, transportation of these materials from Earth 

will not be a limiting factor. 

The most common soil material is anorthite, CaAI2Si208, which can be 

considered to be a mixture of calcium, aluminum, and silicon oxides: CaO + 

AI203 + 2Si02. In the literature several methods are proposed to process 

extraterrestrial ores, but none have been tested in situ. The primary 

criteria for the process selection are low power requirement and low 

requirement for non-lunar materials. Other important criteria include the 

end products provided, the process complexity, and suitability for 

manufacturing under 1 /6 G. 

Processes considered include fluoroacid leaching, vapor phase pyrolysis [lo], carbothermal processing, and slag electrolysis. For the candidate 

process we considered aluminum reduction followed by electrolysis to 

recover the aluminum, as shown by the following reaction: 

3Si02+4Al + 3Si+2A203, 

2 AI203 (electrolysis) + 4 Al + 3 02 

This process has been develo ed and demonstrated by Keller and 

co-workers at EMEC corporation [llf) The aluminum acts simultaneously as 

a reducing agent for the silicon dioxide and as a solvent for the silicon that 

has been formed, which can subsequently be crystallized out of the solution 

in a nearly pure form by cooling. Because the reduction is exothermic, the 

reaction vessel needs to be heated externally only during the initial phase 

of melting of the slag and the beginning of the reaction. 

An alternative process is electroreduction from an alkaline-earth oxide 

melt, which has been demonstrated by DeMattei, Elwell, and Feigelson at 

4 
Stanford 1121, as shown in the reaction: 

3 BaSiO3 (electrolysis)+ Si + 3 BaO + 2 Si02 + 02 

This has the disadvantage that the flux metal, barium, is not available 

on the moon. It is possible that other metals can be used. This is not a 

problem as long as the material recycling efficiency is high. 

The silicon obtained must be purified for use in semiconductor devices. 

A candidate process for purification is by float-zone recrystallization, where 

the silicon rod is melted in a zone that passes along the length of the rod. 

Impurities are segregated to the end of the material. This process is slow, 

but has the advantage of zero materials consumption. 

For crystalline silicon, assuming 17.5% efficiency, 65 p. thick cells, and 

65% utilization of the silicon refined, 1000 kg/yr of silicon is required for 

a production rate of 1 MW/year. This is small amount compared to the 

processing of 12,000 metric tons/yr of lunar soil required for the 1,000 

ton& lunar oxygen production envisioned in the lunar base/Mars evolution 

scenario We thus conclude that it is indeed reasonable to expect that 

even large-scale photovoltaic manufacturing can be considered to require 

no additional mining facilities. 

3.3 Synthesis of Silane 

If the solar cells are to be amorphous silicon cells made by the standard 

plasma deposition process, the silicon must be manufactured into silane 

(SiH4) gas. There are many different process sequences currently used for 

manufacture of silane 1131. We need to evaluate these methods considering 

availability of materials on the moon. All of the reactions involve materials 

which are not available on the moon. It is therefore important that the 

recycling efficiency of the process be high. The largest scale process, 

developed by Union Carbide [14* 151, converts powdered, 98% metallurgical 

grade silicons to trichlorosilane at 500°C in a fluid-bed reactor and then 

sucessively disproportionates the trichlorosilane to an end product of 

silane according to the following sequence of reactions: 

Si + 2 H2 + 3 Sic14 + 4 HSiCl3 

6 HSiC13 + 3 Sick + 3 H2SiC12 

4H~SiCl2 + 2HSiCl3 +2H3SiCl 

2 H3 Sic1 + HzSiClz + SUI4 

The intermediate reaction products are recycled. Metallic impurities 

in the initial metallurgical grade silicon are converted to chlorides and 

settle out in the first distillation step. For maximum recycling efficiency, 

these should be electrolyzed to recover the chlorine for reuse. 

It should be noted that the actual mass of material to be manufactured 

5 
is not very large. If the cell manufacturing line is to produce amorphous 

silicon cells, for example, at 10% efficiency, the actual silane used in 

producing the two micron thick active layer is only 25 kg per year for a 

one megawatt/yr production line. If the production line capacity is 

increased to ten megawatts/year to produce panels for base expansion, 

solar-electric propulsion for a Mars mission, and for powering satellites in 

GEO, the requirement for silane, including waste, could be around 300 

kg/year. By Earth production standards, this would be considered a 

laboratory-scale production level--there are at least 14 silane 

manufacturing plants worldwide with production rates over one ton/year 

[131. 

4. solar Celts 

Primary considerations for the choice of a production process are (1) 

Low use of Earth-supplied materials, including reactants, etchant, and 

replacement parts; (2) low labor requirements, (3) energy efficiency, and 

(4) low mass equipment. As part of consideration (3). it is important to 

minimize the amount of silicon required, since the major part of the 

energy expenditure needed in manufacture comes from the silicon refining 

process. It is also useful to distinguish processes requiring only heat, 

which can be obtained by a relatively simple solar furnace, from processes 

requiring electrical power. 

4.1 Crystalline Silicon 

Typical crystalline silicon solar cells have an efficiency of about 15% 

under the space illumination of 1.35 kW/m2. The best cells made have an 

efficiency of 19%. The main problem with conventional crystalline silicon 

is the low power to weight ratio due to the thickness of the silicon 

substrate. This may be solved by use of ultra-thin cells using light-trapping 

techniques to increase the effective optical absorption [Is]. Calculations 

indicate that such cells also have greatly improved radiation tolerance. 

Another possibility for increasing specific power is to use light-weight 

concentrator elements. For space use, a concentrator system does not 

require great structural strength. A low concentration system made from 

1.5 micron thick aluminized plastic with a support structure of equally low 

mass could improve specific power by a factor of nearly ten. The design 

has an advantage of a large acceptance angle compared to highconcentration systems, thus not requiring high-precision pointing, and 

allowing one-axis tracking. For Mars operation, where winds can reach 

speeds imposing dynamic loading roughly the same as a 25 MPH terrestrial 

wind, either stiffer arrays, or ones which could be stowed in high wind 

conditions, would be required. 

The candidate process sequence is designed to take maximum 

advantage of the lunar environment. Silicon purification by (ch1oro)- silane 

distillation as discussed above should be avoided in the interest of 

simplifying the process and minimizing dependence on imported 

materials. Instead, the required purification process could be done by 

6 
multiple vacuum float-zone refining. This step would be followed by 

single-crystal growth, also by the float-zone process. Since float-zone 

processing is done in a solar oven, the process is not energy intensive. 

The boule is then sawed to the desired cross-section followed by wafer 

slicing, thinning, and surface etching to form the substrate silicon wafers. 

Silicon removed during the sawing and slicing operations would be 

re-melted and reused: nevertheless, a considerable amount of silicon is 

likely to be wasted. While the assumed utilization of 65% may be 

optimistic by current practice, it is likely that a process designed to 

minimize waste could do considerably better. 

Solar cells would be formed on the substrate wafers by ion-implantation 

using a non-mass analyzed, solid source implanter [171, followed by 

annealing in a solar furnace, back-surface deposition of aluminum for a 

back-surface field and back contact: deposition of Al front contacts; and 

finally by vacuum evaporation of the Ti02 AR coating. The cell 

manufacturing process is followed by bonding the cells to a lunarmanufactured coverglass with silicone adhesive (which may have to be 

imported) and interconnection of the cells into an array. 

Major disadvantages of crystalline silicon for lunar manufacture are the 

complexity of the process, the mass of the processing equipment needed, 

and the comparatively high usage of refined silicon. 

4.2 Amorphous SkH 

Amorphous silicon solar cells have efficiencies of 5-6% AMO, with 

-10% likely for the near term [la]. The advantage of amorphous silicon 

cells is that the active thickness may be as low as 1-2 microns, thus 

requiring very little use of refined silicon. The disadvantage is the 

comparatively low efficiencies and the yet-unsolved problem of 

light-induced degradation. Preliminary studies suggest that amorphous 

silicon cells are more radiation tolerant than single crystal silicon, by a 

factor of 3 for electron irradiation, and by as much as a factor of 50 for 

proton irradiation [1**191. Further, it may be possible to remove radiation 

damage by annealing at temperatures of 200" C or less [201. 

An advantage of amorphous silicon is that, in principle, the process 

sequence can be made extremely simple. 

While the silicon is readily available, hydrogen would have to be 

imported from earth. As 2-10 atomic percent of the composition of 

amorphous silicon, it is a negligible weight percentage, so this will not be a 

major problem. Dopants for a-Si typically are boron (diborane) and 

phosphorus (phosphine). The boron would have to be imported; this is 

also a small component. It also may be possible to dope the material with 

aluminum. Current technology amorphous silicon cells use indium-tin 

oxide, tin oxide, or cadmium sulfide for a transparent conductive surface 

layer. If material is not to be imported for the front contact, a possible 

substitute is zinc oxide, a highly transparent semiconductor. This would 

require refining zinc from the low (0.03%) concentration present. If this 

is not possible, it would be possible to use a very thin layer of aluminum. 

Most projected high power/weight amorphous silicon arrays use 

polymer films (e.g., Kapton, Tedlar) as substrates. The absence of hydrogen 

7 
and carbon on the moon will require these to be brought from Earth. If 

specific power is not an issue (e.g., if the arrays are to be used on the 

moon), cells could be fabricated on glass (possibly silica or alumina), which 

is easily available from lunar material. 

For uses where specific power is important (e.g., arrays which will be 

used elsewhere, for example for SEPS missions or for a Mars base), a likely 

substrate would be a thin metal foil. Production of amorphous silicon cells 

has been demonstrated on 7.5 to 25 micron electroformed nickel sheets, 

or stainless-steel sheets thinned by etching [20]. Iron is a major 

component of the lunar crust: very thin steel sheets (density 7.9 gr/cm3) 

would be an available substrate. Nickel is not easily available in the bulk 

soil, but can probably be refined from meteoric material magnetically 

separated from the soil. 

A much better substrate would be thin aluminum or titanium, since the 

density is much lower (2.7 and 4.5 gr/cm3 respectively). Use of such 

substrates is unproven. 

One advantage to the moon as a location for an amorphous silicon 

manufacturing site is the presence of a good vacuum. Ambient pressure on 

the moon is in the range of 106 molecules/cm~. While exhaust from the 

transport spacecraft and leakage from the habitat will degrade the ambient 

high-vacuum environment somewhat, the pressure is still expected to be at 

most in the range of 10-9 torr (21). Since existing amorphous silicon 

processes have base pressures in the mid- to low- 10-6 torr range, this is 

an excellent production environment. 

4.3 a-Si Cell Production 

An advantage of amorphous silicon is the base of production experience 

in large-scale, semi-automated factories. The world output of amorphous 

silicon solar cells is 10- 15 MW/yr, with additional production facilities 

under construction. 

Amorphous silicon cells are currently made by a plasma process at 0.1 

to 1 torr. Glow-discharge processing seems to give the best results. 

Typical deposition conditions are sumarized in table 3 [22]. Three a-Si 

deposition chambers, a chamber for the deposition of the transparent 

conductor and one for deposition of the metal contacts, plus a loading 

chamber and an unloading chamber are required. In the roll-to-roll 

process [231, a flexible substrate is passed sequentially through chambers 

which deposit the p, i, and n amorphous silicon layers and the transparent 

conductor. In the continuous multichamber in-line system, the solar cell 

is deposited on a substrate, e.g., glass, which need not be flexible. 

For a typical production output of 1.5 MW per year, the production 

equipment for such a line on Earth would occupy about 750 m2 of floor 

space, with a volume of about 230 m3 and a total mass of 45,000 kg [241. 

However, it must be noted that typical production processes are not 

optimized to minimize the equipment mass. 

The lunar vacuum ambient will simplify the production process, since 

the vacuum chamber can be omitted. The process will require an 

enclosure to prevent the gas from leaking out into the lunar vacuum, but 

this can be light, since the pressure is negligible. It will also be necesary 

8 
to collect and compress the "waste" gas to recycle the hydrogen. This is 

done with vacuum pumps acting as compressors. The reaction chamber 

itself can be made extremely light in weight. The irreducable mass 

elements are the three RF generators, 50 kg each, the seven vacuum 

turbopumps, 30 kg each (450 l/min), and a primary pump to back the 

turbopumps, 250 kg (200 m3/hr). The total mass for this is about 600 kg. 

Likely other elements could increase this total by a factor of two or three. 

Provision of automated machinery would be likely to increase this yet 

further. 

We also note that an alternative process sequence for lunar manufacture 

of amorphous silicon cells, based on vacuum evaporation using solar 

concentrators followed by hydro enation of the material as a separate step, 

has been proposed by Fang [851. While this rocess to date has only 

mechanisms that prevent efficiencies from advancing to levels comparable 

to other technologies. If higher efficiencies can be obtained, the process 

proposed by Fang has an advantage over the plasma process discussed 

above in that the silane manufacturing process is unnecessary. 

produced cells of comparatively low efficiency P 261, there are no known 

4.4 a-Si Mass and Speci@ Power 

Amorphous Si cells are not yet proven in space. In the near term, a-Si 

will likely not reach efficiencies high enough to be competitive in low 

Earth orbit, where drag is an important factor. For cells to be used on the 

moon, weight is not a particular issue. For this application amorphous 

silicon is very likely the best technology. For other uses, it is worthwhile 

to make an approximate calculation to determine whether high specific 

power can be reached despite comparatively low efficiency. 

The baseline cell considered was that of Mrig and Jackson [271, 

modified for lunar materials by replacing tin oxide by zinc oxide, and 

assumed to be deposited on a 25 micron thick Kapton substrate. It has 

been suggested 112.131 that an amorphous silicon array may require little or 

no coverglass, since the radiation damage is low, especially if the array is 

periodically annealed. This is likely optimistic, and applications such as 

Mars surface power will certainly require some protection to avoid 

abrasion by dust. Silica covers could easily be manufactured from materials 

available on the moon. The array weight, shown in table 4-A, is calculated 

both with and without a silica cover. 

If the cell has an efficiency of 5%. a very conservative assumption, this 

translates to a uncovered cell specific power of 1700 W/kg. Since the 

Earth-manufactured substrate is 88% of the total cell mass: clearly there is 

no significant weight advantage to manufacturing such a cell on the moon. 

Addition of the cover reduces the specific power by a factor of four. 

For a cell manufactured from all lunar materials, a lunar-manufactured 

steel substrate is substituted for the Kapton. This greatly increases the 

mass. A 25 micron steel substrate weighs 200 gr/m2, leading to a specific 

power (again assuming 5% efficiency) at the cell level of 350 W/kg without 

cover, or 220 with. 

Despite the low efficiency assumed, even with the glass covers the cell 

specific power is competative with baseline single crystal silicon cells. Cell 

9 
specific power is only one factor in the overall array specific power, and 

the structural mass of the array is also a consideration. In general this 

should be expected to scale with the cell mass. 

Table 4B shows cell-level mass for a more advanced cell. Here we 

assumed a thinner substrate can be used, as well as slight reductions in the 

cell thickness (primarily the back contact). The thinnest Kapton currently 

available from Dupont is 7 micron. Tensile strength is 30,000 PSI, more 

than adequate for stretching out the array. 

For this case the substrate is 80% of the total mass. For the advanced 

cell we assume a lower-mass and an efficiency increase to lo%, which is 

typical of the best single-junction cells currently made in the laboratory. 

Considerably higher performance is predicted for advanced structures. 

The cell-level specific power is 9880 W/kg without cover, or 1900 W/kg 

with a thin (25 micron) cover. For a cell from all lunar materials, a 7.5 

micron steel substrate weighs 60 gr/m2, leading to a cell specific power of 

2200 W/kg without cover or 1100 W/kg with the 25 micron cover. 

5. Conclusions 

Solar cells manufactured on the moon could significantly reduce the 

cost of transportation of power systems to space destinations, including 

the moon, Mars, Earth orbit, and transfer orbits. Silicon is abundant on 

the moon, and refining processes have been demonstrated which do not 

depend on extensive use of reactants imported from Earth. Because of the 

lower requirements for refined silicon, the amorphous silicon process is 

preferred, despite lower efficiencies. Calculations show that specific 

power of amorphous silicon cells can be adequate for most uses. 

Production of structural elements for the arrays, such as struts, frames, 

beams, etc., is also an important part of the array manufacturing process, 

although not discussed in depth here, as is production of the substrates. 

Assuming mining operations already in place on the moon for other 

purposes, such as oxygen extraction, production of silicon for lunar 

photovoltaic arrays is not a major difficulty. Lunar-produced photovoltaics 

are likely to be a practical product only if the predicted demand for power 

in space is large, at a minimum several megawatts per year. Such 

requirements are likely if there is a vigorous human presence in space, if 

solar-electric propulsion vehicles become a significant fraction of the 

in-space transportation system, or if satellite solar power systems become 

a power source for terrestrial power. 

10 
6. References 

(1) Lunar Bases and Space Activities in the 21st Century Symposium, 

5-7 April 1988, Houston, TX. 

(2) NASA Office of Exploration, Exploration Studies Technical Report 

FY 1988, Vol. 1, NASA Technical Memorandum 4075, 21-22 (Dec. 1988). 

(3) B.G. Logan, “Initiative for the 21st Century: Advanced Space Power 

and Propulsion Based on Lasers,” presented at NASA Lewis April 25-26, 

1988; Lawrence Livermore Laboratory preprint UCRL-98520. 

(4) G.E. Maryniak and B. Tillotson, “Design of a Solar Power Satellite 

for Construction from Lunar Materials,” Space Power 7, No. 1, 27-36 

( 1988). 

(5) Representative data from: G.H. Morrison et al., “Multielement 

analysis of Lunar Soil and Rocks” Science Vol. 167 (special issue on Apollo 

11 results), 505-507 (1970); Apollo Preliminary Science Report (Apollo 1 1 

through Apollo 17); Proc. 9th Lunar and Planetary Science Conf., 

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Manufacturing,” J. Brit. Interplanetary Soc., 30, 3 14-3 16. 

(6) D. Bhogeswara Rao et al., “Extraction Processes for the Production 

of Aluminum, Titanium, Iron, Magnesium, and Oxygen and Nonterrestrial 

Sources,” Space Resources and Space Settlements, NASA SP-428, 

(7) D. Ho and L.E. Sobon, “Extraterrestrial Fiberglass Production Using 

Solar Energy,” Space Resources and Space Settlements, NASA SP-428, 

(8) R.J. Williams, “Mining and Beneficiation of Lunar Ores,” Space 

Resources and Space Settlements, NASA SP-428, 225-232 (1979). 

(9) G.A. Landis, “Solar Power for the Lunar Night,” 9th Biennial 

Princeton/SSI Con. on Space Manufacturing (1989); to be published in 

Space Manufacturing 8 (AIAA, 1989). 

(10) D.R. Sparks, “Vacuum Reduction of Extraterrestrial Silicates,” J. 

Spacecraft 25 (2). 187-189 (1988). 

(10) D.L. Anthony et al., “Dry Extraction of Silicon and Aluminum from 

Lunar Ores,” Paper No. LBS-88-066, Lunar Bases and Space Activities in 

the 21st Century Symposium, 5-7 April 1988, Houston, TX. 

(1 1) R.C. DeMattei, D. Elwell, and R,S. Feigelson, “Electrodeposition of 

Silicon at Temperatures above its Melting Point,” J. Electrochem. SOC., 

( 12) P.A. Taylor, “Silane: Manufacture and Applications,” Solid State 

Technology, July 1987. 

(13) J.H. Lorentz, ‘The Silicon Challenge,” Proc. Flat-Plate Solar Array 

Workshop on the Science of Silicon Material Preparation, Aug 23025, 

(14) Union Carbide, “Feasability of the Silane Process for Producing 

Semiconductor Grade Silicon,” Final Report, June 1979, DOE/JPL 

Contract 954334. 

( 15) G.A. Landis, “Thin, Light-Trapping Silicon Solar Cells for Space,” 

20th IEEE Photovoltaic Specialists Conference, Las Vegas, NV, 708-7 12 

(1988). 

(16) A.J. Armini, S.J. Bunker, and M.B. Spitzer, “Non-Mass Analyzed 

Ion Implantation Equipment for High Volume Solar Cell Production,” 16th 

257-288 (1979). 

225-232 (1979). 

128, 8, 1712-1714 (1981). 

1982, DOE/JPL-1012-81. 

11 
~ 

IEEE Photovoltaic Specialists Conference, 895-899 ( 1982). 

(17) G.A. Landis, S.G. Bailey and D.J. Flood, “Advances in Thin-Film 

Solar Cells for Lightweight Space Photovoltaic Power,” NASA Tech. Memo. 

TM-102017 (1989); to appear in Space Power, Vol. 8 (1989). 

(18) J.J. Hanek et al., Space Photovoltaic Research and Technology 

1986, NASA CP-2475, 99-110 (1986); C.F. Gay et al., 17th IEEE 

Photovoltaic Specialists Conference, 15 1 - 154 ( 1984). 

(19) C.E. Byvik et al., 17th IEEE Photovoltaic Specialists Conference, 

(20) G.A. Landis, “Degradation of the Lunar Vacuum by a Moon Base,” 

submitted to Acta Astronautica (1988). 

(2 1) M.A. Perino, “Introduzione Alle Celle Fotovoltaiche”, A.I.T. 

SG-NT-AI-065, Sept. 1987; see also M.A. Perino, “Celle Solari in Silicio 

Amorfo Idrogenato,” A.I.T. SG-PL-AI-040, Oct. 1986. 

(22) A. Madan, ”GSI’s Continuous Multichamber Approach for Mass 

Production of Amorphous Silicon Solar Cells,” Proc. I987 Amorphous 

Silicon Subcontractors’ Review Meeting, Palo Alto, CA Jan 26-27, 1987. 

(23) A. Madan, private communication ( 1989). 

(24) P.H. Fang, “A Lunar Solar Cell Production Plant,” Solar Cells, 25, 

(25) P.H. Fang et al., “Combined Microcrystal and Amorphous Silicon 

(26) L. Mrig and B. Jackson, Amorphous Silicon Conceptual Design and 

155-160 (1984). 

31-37 (1988). 

Solar Cells,” Appl. Phys. Lett. 41 (4). 365 (1982). 

Cost Estimate, SEN technical report SEN-RR-2 16-2668, Aug. 1985. 

Acknowledgements 

An earlier version of this paper was presented at the 20th IEEE 

Photovoltaic Specialists Conference in Las Vegas, NV, September 1988. 

The authors would like to thank Dr. A. Madan of Glasstech Solar, Inc, 

for information concerning amorphous silicon deposition systems, and 

Maria Antonietta Perino would like to acknowledge the International Space 

University - Commercial Operations Group for discussions on the 

utilization of amorphous silicon solar cells for a moon base power supply. 

12 
~ ~~ ~~~ ~ 

Table 1-A: AV in km/sec 

(minimum velocity change needed to launch payload) 

kan: 

To: WMQQg 

LE.0. 9.3 3.3 

G.E.O. 11.9 3.2 

Moon 13.6 - Marstransferorbit 13.6 5.2 

rable 1-B: Theoretical Maximum Payload Fraction 

(in percent) 

lhm: 

To: 

LEO. 9.8 43' 

G.E.O. 5.1 45 

Moon 3.3 100 

Mars transferorbit 3.3 27 

Calculated using Vehusy4 km/sec 

IHz/02 propellantl. 

*assumes aerobraking at perigee. 

~ 

Table 2: 

Abundance of Elements in the Lunar Crust and Soil 

Mqjor Consfituents: 

maximum concentrutions in percent 

Oxygen 45 

Silicon 28 

Iron 18 

Al 14 

11 

<)a 9 

s 0.3 

P 0.2 

Mg 

Other components of interest Ippmj 

Germanium 450 Boron 24 

Zinc 300 Copper 18 

Carbon 200 Gallium 8 

Arsenic e100 Sn < 10 

Hydrogen 70 Se. Cd <1 

Tellurium 60 

Abundances listed are peak concentrations found in rocks or sod from ApoUo misswns. 

Table 3: Glow-discharge processing of a-Si 

Gcs 

A-essure 0.1 to 10 Torr 

Substrate temperature 200 - 300" C 

Gasc@sbnuelodty 20 - 30 sccm 

Sa4 (pure or in HZ or At) 

(other constituents such as SiF4 also sometimes added) 

Discharge power 4w 

ndopantgcrs pH3 

PdOPantF BZHS 

13 
Table 4: Specific Power of Thin-Film Cells 

&Baseline 

CellElement Matt T M 

ARCoating Ti02 0.95 4.3 0.4 

TCO ZnO 0.1 5.6 0.6 

a-Si Si 0.54 2.3 1.2 

Back Contact &l - 1.0 2.7 2.7 

total cell 2.59 4.9 

- lul ferPcm3) -2) 

Substratq Kauton 25. 1.4 35.5 

total, cell plus substrate 40.4 

Cover Si02 50 2.6 125 

efficiency: 5% (AMO): specific ower (excluding array structure): 

1700 Wpkg without cover; 

410 W/kg with cover 

Cell made from all-lunar materials: 

cell 2.59 4.9 

substrate steel 25. m2QQ 

total, ell plus substrate 205 

Cover Si02 50 2.6 125 

efficiency: 5% (AMO): 

specific power (excluding array structure): 

350 W/kg without cover; 

220 W/kg with cover 

Cell Element Material M 

cell 1.9~ a-Si 2.7 

substrate 7uKauton 10.8 

total 13.7 

efficiency: 10% (AMO): specific power: 9900 W/kg without cover; 

1900 W/kg with 

- [er/m2) 

AU-lunar materials: 

cell 1.9~ a-Si 2.7 

substrate 7.5usteel 

total 62.7 

efficiency: 10% (AMO): specific power 2200 W/ without cover 

with 25p glass cover: 11 5 0 W/kg 

14 
LEO - Space Station upgrades 

Intermediate - ion-propelled transfer 

GEO - Commercial satellites 

Moon - Lunar base power 

Mars - Mars mission--vehicle power 

Deep Space - power and propulsion 

Space manufacturing facility 

Satellites 

vehicle 

Mars mission --surface power 

solar etectric 

Figure 1: 

Uses for Lunar Manufactured Photovoltaic Arrays 

15 
Icn 

0 

0 

z 

0 

IIIT 

0 

a 

cn 

z 

< 

U 

I- 

- 

a 

LEO G EO W 0 0 N MARS 

s1,ooo B - 

$100 B - 

310 B - 

31 B5100 M - 

$lo 1 

Figure2 

Estimated transportation costs of delivery of 100 kW of electrical 

power to orbit, moon, and Mars using current technology boosters. Shown 

is state of the art (SOA) photovoltaic technology and storage, SP-100 

nuclear power system, and a representative future technology "advanced" 

power system. The high cost of PV/storage for the moon is due to the 

mass of the storage required for the lunar night. 

16 
NASA National Aeronautics and Report Documentation Page 

Space Administration 

2. Government Accession No. NASA TM-102102 1. Report No. 

Corrected Copy 

4. Title and Subtitle 

Lunar Production of Solar Cells 

7. Author@) 

Goeffrey A. Landis and Maria Antonietta Perino 

9. Performing Organization Name and Address 

National Aeronautics and Space Administration 

Lewis Research Center 

Cleveland, Ohio 44135-3191 

2. Sponsoring Agency Name and Address 

National Aeronautics and Space Administration 

Washington, D.C. 20546-0001 

3. Recipient's Catalog No. 

5. Report Date 

6. Performing Organization Code 

8. Performing Organization Report No. 

E-4866 

10. Work Unit No. 

506-41-11 

11. Contract or Grant No. 

13. Type of Report and Period Covered 

Technical Memorandum 

14. Sponsoring Agency Code 

5. Supplementary Notes 

Prepared for the 9th Biennial SSI/Princeton Conference on Space Manufacturing sponsored by the Space Studies 

Institute, Princeton, New Jersey, May 10-13, 1989. Geoffrey A. Landis, National Research Council-NASA 

Research Associate; Maria Antonietta Perino, Aeritalia, Space Systems Group, Research, 10146 Torino-Corso 

Marche, Italy. 

6. Abstract 

The feasability of manufacturing of solar cells on the moon for spacecraft applications is examined. Because of 

the much lower escape velocity, there is a great advantage in lunar manufacture of solar cells compared to Earth 

manufacture. Silicon is abundant on the moon, and new refining methods allow it to be reduced and purified 

without extensive reliance on materials unavailable on the moon. Silicon and amorphous silicon solar cells could 

be manufactured on the moon for use in space. Concepts for production of a baseline amorphous silicon cell is 

discussed, and specific power levels calculated for cells designed for both lunar and Earth manufacture. 

7. Key Words (Suggested by Author@)) 

Moon base 

Lunar exploration 

Space industrialization 

Solar cells 

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