Space Power Station First Order Assessment 22 Apr 2007

1. Space Power Station First Order Assessment 22 Apr 2007 UNCLASSIFIED

2. 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 mw power and transmit to Earth • Terrestrial hardware to receive mw power and conversion to electrical power UNCLASSIFIED

3. Space Power Station - Concept • GEO Solar Power Stations (SPS) • Converts solar flux into electrical power using photovoltaics • Converts electrical power to microwave (mw) power • Beams (transmits) mw power to Earth • Earth Receive Station (ERS) • Receives mw power • Converts mw power to electrical power • Feeds National Power Grid (NPG) • Motivation - become hydrocarbon independent • Total annual US energy consumption is ~ 1016 W • Hourly US consumption rate is ~ 1.14x1012 Wh (Watts/hour) • ~ 85% of US energy is hydrocarbon based • Hourly US hydrocarbon consumption is ~ 9.7x1011 Wh UNCLASSIFIED

4. 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/m2 • Effective flux is therefore ~ 275 Wh/m2 • US hydrocarbon consumption is ~ 9.7x1011 Wh • Surface area of GEO photovoltaic array needed to generate ~ 9.7x1011 Wh is ~ 3.5x109 m2 (~ 60 km on a side) • Assumed volume of array is 3.5x107m3 (1.0 cm thick) • Mass of array is ~ 9.5x1010 kg(using Al as basis @ 2.7x103 kg/m3) or ~ 8.2x1010 kg(using silicon @ 2.33x103 kg/m3) UNCLASSIFIED

5. Space Power Station – A Small Problem • EELV Heavy can place ~5x103kg in GEO • Deploying ~ 9.5x1010 kgusing current Heavy EELV would require ~1.9x107 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 mw hardware UNCLASSIFIED

6. 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 >10,356years 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 UNCLASSIFIED

7. 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/m2 average for a 24 hour day • Solar collector array area needs to be about 5.6 times space based alternative or ~2.0x1010m2 or ~2.0x104 km2 • 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 UNCLASSIFIED

8. Space Power Station – Tactical Application • What is efficiency of conversion process is ??? – use ~20% • Solar flux is ~ 1370 Wh/m2 - effective flux ~ 275 Wh/m2 • Target tactical consumption at ~ 9.7*107 Wh (97 Mega Wh) • Why? ~ 100 M1-A1 tanks ~ 100 MWh • Surface area of a GEO photovoltaic array needed to generate ~ 9.7x107 W/hr is ~ 3.5x105 m2 (~ 0.6 km on a side) • Assumed volume of array is 3.5x103m3 (1.0 cm thickness) • Mass of array is ~ 9.5x106 kg(using Al as basis @ 2.7x103 kg/m3) or ~ 8.2x106 kg(using silicon @ 2.33x103 kg/m3) • If thickness were 1.0 mm, mass would be 95,000 kg UNCLASSIFIED

9. Space Power Station – Tactical Application • Heavy EELV can place ~5x103kg in GEO • Deploying ~ 9.5x106 kgusing current Heavy EELV would require ~1.9x103 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 mw hardware UNCLASSIFIED

10. Space Power Station – Going the Other Way • Heavy EELV can place ~5x103kg in GEO • Let 50 EELVs be dedicated to deploying array at one launch/month – yields 2.5x105kg in GEO in ~ four years • If array has an effective structural thickness of: • 1 cm and a density near that of Aluminum (~2700 kg/m3) – yields 27 kg/m2 or 9,259 m2 of solar array • 1 mm and a density near that of Aluminum (~2700 kg/m3) – yields 2.7 kg/m2 or 92,590 m2 of solar array • If 1.0 cm array provides 275 Wh/m2 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 mw hardware UNCLASSIFIED