Study of Space Transportation for Space Solar Power System

Paper number

IAC-05-C3.4-D2.8.03

Author

Dr. Shoji Kitamura, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Dr. Yasushi Okawa, Japan Aerospace Exploration Agency (ISTA/JAXA), Japan

Coauthor

Mr. Hiroshi Aoki, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Mr. Hirofumi Taniguchi, Japan Aerospace Exploration Agency (JAXA), Japan

Year

2005

Abstract

The Japan Aerospace Exploration Agency (JAXA) has been conducting research of space solar power systems (SSPS) in cooperation with universities and industry.  SSPS have the potential to provide abundant quantities of electric power for use on the earth.  However, there are a lot of hurdles to realize them, and one of the major hurdles is the transportation of SSPS to the operational orbit, which presumes to be geostationary earth orbit (GEO) for the SSPS as in most of past SSPS concepts.
	The objectives of this study are to examine the transportation of the SSPS from the ground to GEO, to give a reference scenario of the transportation and to indicate the requirements for the SSPS design, fabrication and assembly.  These will provide the first step for evaluating the feasibility of the SSPS.  This study presumes that the SSPS have a mass of 10,000 tons in GEO and are constructed at the rate of one per year.
As a reference transportation scenario, reusable launch vehicles (RLV) with 50-ton payload capability are assumed for the transportation to low earth orbit (LEO), and orbit transfer vehicles (OTV) propelled by a solar electric propulsion system with ion thrusters are assumed for the transportation from LEO to GEO.  The payload element delivered to LEO by each launch is individually transferred by each OTV transportation service to GEO, where the elements are assembled into a whole SSPS.  This transportation system can avoid some problems that would be caused if the whole SSPS were assembled in LEO.
	The OTV flight time from LEO to GEO and back is assumed to be a year, and then the OTV is reused to deriver the element of another SSPS.  The solar arrays to provide the power to the OTV is assumed to be exchanged after each flight because the solar cells may be significantly degraded in each flight through the radiation belt around the earth.  With these operations and reasonable estimations for specific masses of OTV subsystems, OTV payload ratio was obtained. This, with a SSPS element mass, gave the total mass that has to be launched by RLV.  The result indicated that about 300 times of launch is required per year.
	Cost considerations showed that RLV cost is much higher than OTV cost, which means that improvement in the payload ratio of OTV is important to reduce the total cost for SSPS transportation. Two ways were discussed to improve OTV payload ratio. One is to allow longer trip time for OTV flights. The other is to develop solar cells that are highly resistive to radiation, which would provide reusable solar arrays. CIGS cells are promising in this point.

Abstract document

IAC-05-C3.4-D2.8.03.pdf

Manuscript document

IAC-05-C3.4-D2.8.03.pdf (🔒 authorized access only).

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