AIAA-2010-791690

Solar Power Satellite, Space Elevator, and Reusable Launch

Dr. James A. MartinConsultant, Associate Editor JSR

Space 2010 ConferenceAnaheim, CA

August 30, 2010

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Solar Power Satellites (SPS)

Also called space-based solar power (SBSP), space solar power (SSP)

Studied for decades

Can provide large quantities of clean energy

Requires large investments

Satellite prototype

Low-cost launch and transfer to GEO

Ground receivers and distribution

Possibly competitive electricity costs

More competitive if pollution effects considered

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SPS Design Examples

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Space Elevator

Also called gravity ladder, tether

Studied for decades

Potential for low-cost transfer from Earth to GEO and beyond

Requires large investments

Problems

No current materials allow practical size

Atmosphere interactions

Debris and satellites, especially in low Earth orbit (LEO)

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Space Elevator Illustrations

Looking at North Pole

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Space Elevator Design

Geosynchronous altitude (GEO)

Counterweight

Earth arm

Space arm

Gravity-gradient stabilized,under tension

Elevator car climbs to GEO

Space arm

Propulsion system

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Partial Space Elevator

Similar to full space elevator

Centered at GEO

Stops before reaching Earth

Has no atmospheric interactions

Avoids highest debris orbits near LEO

Length toward Earth can be adjusted to allow practical design with current materials

Carbon nanotubes may allow ~LEO to GEO

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Earth Arm of Space Elevator

Geosynchronous altitude (GEO), maximum area

Bottom, area must carry elevator car and payload

Area ratio depends on material

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Elevator Area Growth

Radius from Earth center ratio, radius at bottom over radius at GEO

0.5 0.6 0.7 0.8 0.9 1

0

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4

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Area ratio, area at GEO over

area at bottom

Fiberglass

Graphite whiskers

2.2

10.0

Strength/densitykm2/s2

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Earth Arm Example

Geosynchronous altitude (GEO), maximum area

Bottom, area must carry elevator car and payload

Fiberglass exampleradius ratio = 0.6

length = 17,000 km

1 cm X 1 cm

1 cm X 18 cm

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Reusable Launch Vehicles (RLV)

Studied for decades

Space Shuttle is a partly reusable system

Compromises during development

Never achieved projected cost reductions

Economics require large traffic volume

Partly reusable has lower development costs

Lower technology risks

Easier to justify development

Good for moderate traffic levels

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Reusable Launch Vehicles (RLV)

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Direct Ascent to GEO

In normal launch to GEO

Ascent to LEO, achieve stable orbit

Hohmann transfer

Direct ascent goes straight up

Never in orbit until GEO

Stays above equatorial launch site

Low atmospheric speed

Higher total ideal velocity to reach GEO

Works well with partial space elevator

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Phased Approach

3 phases

Provides a path to SPS, Elevator, and RLV

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Initial Phase

Use existing launch vehicles

Build initial partial space elevator (SE1)

Materials such as graphite whiskers

Bottom at ~0.6-0.7 GEO radius

Develop partly reusable vehicle

Reusable first stage

Expendable 2nd and 3rd stages

Direct ascent (?) to bottom of SE1

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Partly Reusable Launch Vehicle

Payload 11400

Propellant 19700

Stage 2440

Propellant 58100

Stage 6080

Propellant 488000

Stage 122000

Gross 709000

Mass in kg

Ideal velocity 4 km/s each stage

Expendable 3rd stageoxygen-hydrogen

Expendable 2nd stageoxygen-hydrogen

Reusable1st stageoxygen-RP

VTOVL shown

7 AJ-26 enginesengine-out capability

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Phase 2

Use partly reusable launch vehicle and SE1

Launch to GEO (at reduced cost)

Any payloads to amortize costs

SPS experiments and demonstrators

Build 2nd partial space elevator (SE2)

Materials available at the time

Bottom at ~0.3-0.5 GEO radius

Larger payload than SE1

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Partly Reusable Launch Vehicle (2)

Mass in kg

Ideal velocity 4 km/s each stage

Expendable 2nd stageoxygen-hydrogen

Reusable1st stageoxygen-RP

AJ-26 (7)

Payload 33540

Propellant 58100

Stage 6080

Propellant 488000

Stage 122000

Gross 709000

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Phase 3

Use partly reusable launch vehicle (2) and SE2

Launch to GEO (at further reduced cost)

Any payloads to amortize costs

SPS prototype

Build 3rd partial space elevator (SE3)

Materials available at the time (carbon nanotubes?)

Bottom at ~500 km

Larger payload

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Reusable Launch Vehicle

Mass in kg

Ideal velocity 4 km/s

Reusable1st stageoxygen-RP

AJ-26 (7)

Payload 97720

Propellant 488000

Stage 122000

Gross 709000

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After Phase 3

Use reusable launch vehicle (3) and SE3

Launch to GEO (at very reduced cost)

Any payloads to amortize costs

Facilities for SPS construction and operations

SPS operational satellites

Launch beyond GEO using space arm of elevator

Exploration

Colonization

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Angular Momentum Effect

Geosynchronous altitude (GEO)

Counterweight

Earth arm

Space arm

Elevator car climbs to GEO

Propulsion system

Direction of motion

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Concluding Remarks

SPS, Space Elevator, and RLV go together

3 phase program is proposed

Reusable stage serves all 3 phases

Increased payload and length of Space Elevator with each phase

Final system allows SPS, exploration, colonization

Additional work is needed

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Reference