Space Research Institute SPACE RESEARCH INSTITUTE Rutgers Symposium on Lunar Settlements, June 4-8, 2007 A Solar Electric Propulsion Mission with Lunar Power Beaming Henry W. Brandhorst, Jr., Julie A. Rodiek and Michael S. Crumpler Space Research Institute, Auburn University Mark J. O’Neill ENTECH, Inc. June 4, 2007
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A Solar Electric Propulsion Mission with Lunar Power Beaming
A Solar Electric Propulsion Mission with Lunar Power Beaming. Henry W. Brandhorst, Jr. , Julie A. Rodiek and Michael S. Crumpler Space Research Institute, Auburn University Mark J. O’Neill ENTECH, Inc. June 4, 2007. Outline. Introduction Getting to the moon Lunar Orbit Equatorial Orbit - PowerPoint PPT Presentation
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Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
A Solar Electric Propulsion Mission with Lunar Power Beaming
Henry W. Brandhorst, Jr., Julie A. Rodiek and Michael S. Crumpler
Space Research Institute, Auburn University
Mark J. O’Neill
ENTECH, Inc.
June 4, 2007
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Outline
Introduction
Getting to the moon
Lunar Orbit» Equatorial Orbit
Orbital analysis Power delivery
» Polar Orbit Orbital analysis Power delivery
Summary and Conclusions
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Rationale
NASA’s Vision for Space Exploration to return to the moon» Lunar south pole desired location
Up to 70% sunlight per year
» Other locations being driven by science Equatorial and high latitude locations
Energy storage for the lunar night is massive» Solar array/RFC system – 20 kWe
» Weight ~6 MT with cryogenic storage Can power beaming reduce the mass of night time storage?
» Orbital options to provide power to locations within ±45º of the equator» Molniya-type orbits for polar -90 to 45º S (or +90 to 45º N)» Two year orbital analysis
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Getting to the Moon
Solar electric propulsion mission» ~4343 kg spacecraft
1400 kg Xe propellant Hall thrusters – 10 to 50 kW (3)
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Polar Power Beaming Satellites
Two satellites in polar elliptical orbit
» Offset by ~180º» 500 x 5,000 km orbit» ~7.5 hr orbital time» Apogee over the south pole
850 nm laser beam» 1.5 m2 aperture (1.38 m dia)
Increases beam size on surface vs previous case
Uses 1-J GaAs tracking array on surface
» Can track only one satellite» Or can use fixed array
Reduces surface power
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Satellite Parameters – 8/23-24/08(500 x 5,000 km Polar Orbit)
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Access Times for Polar Orbits
Polar orbits give excellent access times
» From the pole to ~30º
» 5,000 km apogee has least time Requires the second satellite Both satellite access times are
comparable Access time depends on satellite
altitude» Higher provides more access
Longer beam distance reduces power received
» Second satellite can provide more power
If it can also be tracked Or use planar array
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Power Delivered to Surface
With a tracking array, power to the surface is essentially constant
» ~16.8 kW per satellite» 50% power conversion to laser beam» 45% conversion of laser into power
Includes other losses as well
» Assumes a 15 kW surface array (in sunlight, 62 m2 in area)
Neither receiving array area nor laser beam intensity is excessive
Can also adjust beaming parameters
With two satellites, the longest time a receiver at 45º does not receive power is:
» Only 1.5 hours maximum, less for a polar site» Substantially reduces storage!
Beaming is a very plausible option!
Space Research Institute
SPACE
RESEARCH
INSTITUTE
Rutgers Symposium on Lunar Settlements, June 4-8, 2007
Summary
Two cases of lunar power beaming were studied» Equatorial orbit, ±45º N-S, two satellites, 500 x 30,000 km (2 year)
850 nm laser, 4 m2 beaming aperture Delivers up to 18 kW with two satellites to GaAs surface array
› Partial tracking
Eight times with storage times of 84 hrs, rest of time <54 hrs
» Polar orbit, -90 to 45º S two satellites, 500 x 5,000 km (same for N) 850 nm laser, 1.5 m2 beaming aperture Delivers 16.8 kW with either satellites Maximum dark time of only 1.5 hrs
› Insignificant storage time
Laser power beaming to lunar surface seems feasible» Multiple orbits are possible» Substantial reduction in energy storage times for any location» Can yield significant mass savings for exploration architecture