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UNCLASSIFIED Space Power Station First Order Assessment 22 Apr 2007

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UNCLASSIFIED Objective Provide a perspective on viability of Space Solar Power for a variety of applications Big down to small applications System charateristics - how big/massive, how many launches, how many years … Scope: Addresses only orbital hardware required to collect solar energy - will not address: Hardware to convert to w power and transmit to Earth Terrestrial hardware to receive w power and conversion to electrical power

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UNCLASSIFIED Space Power Station - Concept GEO Solar Power Stations (SPS) Converts solar flux into electrical power using photovoltaics Converts electrical power to microwave ( w) power Beams (transmits) w power to Earth Earth Receive Station (ERS) Receives w power Converts w power to electrical power Feeds National Power Grid (NPG) Motivation - become hydrocarbon independent Total annual US energy consumption is ~ 10 16 W Hourly US consumption rate is ~ 1.14x10 12 Wh (Watts/hour) ~ 85% of US energy is hydrocarbon based Hourly US hydrocarbon consumption is ~ 9.7x10 11 Wh

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UNCLASSIFIED Space Power Station – Assumptions What is efficiency of conversion process is – use ~20% < 28% solar flux to electrical conversion in SPS < 90% electric to microwave conversion in SPS < 90% transmission efficiency < 90% microwave to electric conversion in ERS Solar flux is ~ 1370 Wh/m 2 Effective flux is therefore ~ 275 Wh/m2 US hydrocarbon consumption is ~ 9.7x10 11 Wh Surface area of GEO photovoltaic array needed to generate ~ 9.7x10 11 Wh is ~ 3.5x10 9 m 2 (~ 60 km on a side) Assumed volume of array is 3.5x10 7 m 3 (1.0 cm thick) Mass of array is ~ 9.5x10 10 kg (using Al as basis @ 2.7x10 3 kg/m 3 ) or ~ 8.2x10 10 kg (using silicon @ 2.33x10 3 kg/m 3 )

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UNCLASSIFIED Space Power Station – A Small Problem EELV Heavy can place ~5x10 3 kg in GEO Deploying ~ 9.5x10 10 kg using current Heavy EELV would require ~1.9x10 7 launches - assuming no replacement require for wear-out – no maintenance … Deployment would require ~ 51,781 years at a launch rate of one EELV Heavy a day Numbers do not include any w hardware

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UNCLASSIFIED Space Power Station – A Big Problem If all conversion efficiencies were 100% and the effective thickness of the array remained 1 cm, system would require ~ 1/5 the mass and therefore 1/5 the launches … would only take >10,356 years to deploy as long as all parts had MTBFs on the order of 10,000 years At 100% efficiency and effective array thickness of 0.001 m (1 mm) mass on-orbit would be down by factor of ten – so it would only take ~ 1000 years to deploy at one EELV Heavy launch a day If array needs to be replaced every 100 years because of radiation damage, etc … deployment and never closes

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UNCLASSIFIED Space Power Station – Terrestrial Alternative Max solar flux in desert regions approaches 1000 Wh Overall terrestrial efficiency for a 24 hour day is less than orbital efficiency … ~ 5% … about a quarter if well sited 50% daylight 50% weather 70% trapped by tracking arrays 28% solar to electrical conversion efficiency Yields ~ 50 Wh/m 2 average for a 24 hour day Solar collector array area needs to be about 5.6 times space based alternative or ~2.0x10 10 m 2 or ~2.0x10 4 km 2 That corresponds to about a terrestrial patch that is about 140 km on a side – relatively easy to site as smaller parts in a variety of Western States – but still big by any standard – about 6% of New Mexico ~315,194 Km²

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UNCLASSIFIED Space Power Station – Tactical Application What is efficiency of conversion process is ??? – use ~20% Solar flux is ~ 1370 Wh/m 2 - effective flux ~ 275 Wh/m2 Target tactical consumption at ~ 9.7*10 7 Wh (97 Mega Wh) Why? ~ 100 M1-A1 tanks ~ 100 MWh Surface area of a GEO photovoltaic array needed to generate ~ 9.7x10 7 W/hr is ~ 3.5x10 5 m 2 (~ 0.6 km on a side) Assumed volume of array is 3.5x10 3 m 3 (1.0 cm thickness) Mass of array is ~ 9.5x10 6 kg (using Al as basis @ 2.7x10 3 kg/m 3 ) or ~ 8.2x10 6 kg (using silicon @ 2.33x10 3 kg/m 3 ) If thickness were 1.0 mm, mass would be 95,000 kg

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UNCLASSIFIED Space Power Station – Tactical Application Heavy EELV can place ~5x10 3 kg in GEO Deploying ~ 9.5x10 6 kg using current Heavy EELV would require ~1.9x10 3 launches - assuming no replacement require for wear-out – no maintenance … Deployment would require 5.2 years at a launch rate of one a day At a rate of 1/month … takes >62 years If effective array thickness was 1 mm, time to deploy would drop by factor of 10 to 6.2 years at one launch per month – but need to add in w hardware

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UNCLASSIFIED Space Power Station – Going the Other Way Heavy EELV can place ~5x10 3 kg in GEO Let 50 EELVs be dedicated to deploying array at one launch/month – yields 2.5x10 5 kg in GEO in ~ four years If array has an effective structural thickness of: 1 cm and a density near that of Aluminum (~2700 kg/m 3 ) – yields 27 kg/m 2 or 9,259 m 2 of solar array 1 mm and a density near that of Aluminum (~2700 kg/m 3 ) – yields 2.7 kg/m 2 or 92,590 m 2 of solar array If 1.0 cm array provides 275 Wh/m 2 on the ground – get 2,546,296 Wh or ~ 2.5 mWh = output from 2.5 M1-A1s 1.0 mm array would yield 10x or ~25 M1-A1s Now, need to discount output by mass (and $$$) of w hardware

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