38 Overview The Aerospace Corporation was tasked by NASA’s Office of Technology, Policy, and Strategy (OTPS) with conducting an Analysis of Alternatives to evaluate SBSP systems and inform NASA leadership on their costs and benefits as compared to other sustainable energy sources. Aerospace considered two systems — SPS-ALPHA Mark III and the Tethered Solar Powered Satellite — reviewed source documentation for each system, considered representative design reference systems for comparison, and decomposed each into modular components. To summarize each design reference system: • The Innovative Heliostat Swarm is broadly derived from the SPS-ALPHA Mark III concept (Mankins, SPS-Alpha Mark-III and an achievable roadmap to space solar power, 2021). This design reference is a lower TRL modular design that can generate power for 99.7% of the year because of its concentrator and reflectors. The Mankins concept proposes that one system, with a mass of 7,500 MT, is capable of delivering 2 GW to one ground-based site. • The Mature Planar Array is broadly derived from the JAXA Tethered Solar Power Satellite design: (Sasaki, A new concept of solar power satellite: Tethered-SPS, 2006), and updated with elements of Caltech’s SSPP design: (Pellegrino, 2022). This is a relatively higher TRL concept consisting of a large panel and a bus system. One system can generate power for 60% of the year. The Sasaki concept proposes that each system, with a mass of 20,000 MT, is capable of delivering an average of 0.75 GW (and 1.2 GW maximum) to one ground-based site, while the 2023 in-space demonstration of Caltech’s technology suggests a design with less mass is possible. Aerospace assessed overall system specifications and made informed assumptions about information that was not available in the source material. Sources describe their systems as modular in nature; however, they have different module mass and size assumptions for each subsystem. To simplify calculations, Aerospace decomposed the SBSP systems into modular hardware units. The mass of one of these modular hardware units is derived by the ratio of each SBSP subsystem’s mass to the total SBSP system mass (power, structure, attitude and determination control, propulsion, telemetry tracking and command, command and data handling, and thermal). Other spacecraft hardware assessed was not divided into modular units, and include servicer spacecraft and active debris removal spacecraft. Aerospace assessed the research, development, deployment, operation, and disposal of SBSP systems based on NASA cost modeling work breakdown structure (WBS) elements. Aerospace then used a combination of proprietary models and NASA models to calculate fiscal costs in a combination of statistical and parametric methods. Final costs were provided according to the following WBS: space hardware, land use, ground receiver of SBSP systems, access to space, orbital assembly, operations of the space segment, maintenance of the space segment, and debris mitigation.
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