Space Solar Power, A Fresh Look
Source: NASA
Date: 6/15/97    Record No.: 10459
Contact: John Mankins, Advanced Projects Office, NASA Headquarters.

Space Solar Power, A Fresh Look

In 1968, Peter Glaser of AD Little put forth a concept to put solar power stations in earth orbit and beam power to ground stations using microwaves. After extensive study in the 1970's by NASA and DOE, the idea was found infeasible for many reasons, especially the costs to put payloads into orbit and the a design approach that involved massive amounts of equipment and people in space, i.e. many large geostationary space stations. Even if the approach could could have claimed overall cost effectivenss, the huge upfront capital investment (with no incremental revenues along the way) would have prevented it from going forward.

NASA has just completed a new review entitled "Space Solar Power, A Fresh Look at the Feasibility of Generating Solar Power in Space for Use on Earth". April 4, 1997. SAIC-97/1005. The NASA/HQ Advanced Concepts Office directed the 18 month study, which assessed newer concepts that might have the potential to enable affordable production of energy in space for use on Earth.

The NASA team characterizes the work as *very preliminary*, but is optimistic that technologies and systems approaches have emerged in the last 20 years that make the potential for space solar power far more feasible than traditionally believed, perhaps as soon as 10-15 years from now.

**They want involvement and participation by the utility industry in the next phases.**

For more information, or to request a copy of the report, contact:

John Mankins, Advanced Projects Office, NASA Headquarters.

A good summary also appears in the May 1997 issue of Aerospace America, published by the American Institute of Aeronautics and Astronautics (AIAA). (I have a copy.)

(The following summary was prepared by UFTO, based on material contained in the report)

"Space Solar Power, A Fresh Look at the Feasibility of Generating Solar Power in Space for Use on Earth". April 4, 1997. SAIC-97/1005.

With the original SSP from the 70's, as a "reference concept", the new study looks at new concepts, architectures, and techologies that have been identified or developed since that time. These include modular designs, advanced materials, automated assembly and deployment (in orbit), and new orbital configurations. Most interesting are ideas that produce incremental returns for incremental investment (e.g., small self-deploying launch packages).

Six concept architectures were defined and studied in detail,, based on many ideas identified through exhaustive brainstorming and elicitation of ideas at "Interchange Meetings"

The study's findings include:
1. Markets -- the global need for power will increase dramatically, with advances in the developing countries, and more and more concerns about global climate. SPP could play a significant role.

2. System Architecture -- New concepts involving modularity, non-geo stationary configurations, small launch vehicles make a major difference in the cost outlook, and in possible approaches to financing.

3. System Cost -- High efficiency PV arrays achieving 500 watts or more per kg could be sufficient for economic viability, but low cost space transportation (less than $200 per pound to low earth orbit) is the most important factor.

4. Public Acceptance -- The study is refreshingly forthright in discussing the challenges that safety claims will face, though they are convinced that health and safety risks are negligble.

5. Other Applications -- The technology will have a better chance if it can also be applied in other applications. In particular, a lot of work was done under SDI to develop concepts for beaming power to satellites and aircraft. NASA could use the same techniques to power space craft.

***One especially intriguing idea is to use satellites to relay power from place to place on the earth, much as telecommunications are handled. The implications would be truly staggering, with power deliverable from anywhere to anywhere.***

6. Critical Technologies
-- Space Transportation: Needto have modular launch packages of 20,000 kg or less, to be able to use general purpose launch systems currently under development for a wide array of projected space industries (NASA Reusable Launch Vehicle and Advanced Space Transportation Program). Payload costs must approach $100-200 per pound.
-- Wireless Power Transmission: a new generation of solid state devices might enable the use of a higher microwave frequency. Existing klystron technology may be initially cheaper but would not offer improved packaging and beam steering capabilities. Trade offs need to be carefully examined.
-- Energy Storage: Storage (on board or on Earth) was not considered in this study, but might be needed to have the ability to deliver uninterrupted quality power.
-- Solar Conversion: Terrestial PV has made dramatic gains in the last 20 years, and their space counterparts must be developed (radiation hardening in particular).
-- Guidance, Navigation, and Control: Advanced concepts proposed in the study are potentially less cumbersome than conventional (gyro-thruster) techniques.
-- On Board Power Transmission and Thermal control: The ability to use high voltage high temperature superconductors is critical (to move power from the PV array to the RF beam system).
-- Telecommunications/Data Processing/Autonomy/Command and Control: Systems must have a high degree of operational autonomy. Staffing levels must be low. New data system architectures may be required, involving a high degree of distributed computing power.
-- Structure: Very light weight tension-stabilized structures will be used, instead of the trusses and braces of the original space station approach.

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