ii Key Findings Question 1: Under what conditions would SBSP become competitive? System Designs We assessed two representative SBSP designs: Innovative Heliostat Swarm (Representative Design One, RD1) and Mature Planar Array (Representative Design Two, RD2), based on existing concepts. The SBSP designs serve simply as point designs for assessment purposes and should not be viewed as endorsements to or by NASA. RD11 and RD22 are broadly derived from historical, publicly available designs that include recent updates and provide enough data from which to perform a first-order analysis of this kind. RD1 generates power 99% of the year and collects solar radiation by autonomously redirecting its reflectors toward a concentrator to focus sunlight throughout each day. RD2 uses flat panels, with solar cells facing away from Earth and microwave emitters facing toward the Earth. RD2 generates power 60% of the year due to its limited capability to reposition itself or redirect solar radiation toward its solar cells. Each SBSP design is normalized to deliver 2 gigawatts (GW) of power to the electric grid to be comparable to very large terrestrial solar power plants operating today.3 Therefore, five RD2 systems are needed to deliver roughly the same amount of power as one RD1 system. The functional representation of each design is illustrated in Figure 1. Each SBSP design’s size (which is dominated by the area of its solar panels) and mass is significant. To provide context, consider two examples of space systems with significant mass and solar panel area: an aggregated mass, the International Space Station (ISS); and a distributed mass, a constellation of 4,000 Starlink v2.0 satellites4. The solar panel area is 11.5km2 for RD1 and 19km2 for RD2. The RD1 solar panel area is more than 3,000 times and 27 times greater than that of the ISS and Starlink constellation, respectively. The mass is 5.9Mkg for RD1 and 10Mkg for RD2. The RD1 1 John C. Mankins “SPS-Alpha Mark-III and an Achievable Roadmap to Space Solar Power,” 72nd International Astronautical Congress, October 15, 2021. 2 Susumu Sasaki et al. “A new concept of solar power satellite: Tethered-SPS” Acta Astronautica 60 (2006) 153-165 and Pellegrino et al. "A lightweight space-based solar power generation and transmission satellite." (2022) https://doi.org/10.48550/arXiv.2206.08373. 3 Voiland, Adam, “Soaking up Sun in the Thar Desert,” NASA Earth Observatory, January 26, 2022. https://earthobservatory.nasa.gov/images/149442/soaking-up-sun-in-the-thar-desert 4 The >4,000 Starlink satellites in orbit today are smaller than the v2 and include 4 different configurations, but offer us an example of the kind of upmass that is already approved for this and other existing satellite constellations. Other large constellations are comparable, but of existing constellations, Starlink has already delivered the most mass into orbit. Assuming a mass of 1250kg and solar array area of 105 m2 per Starlink v2 satellite. These systems were chosen because at the time of this report’s publication they represent the most massive single monolithic system in Earth orbit (ISS), and the most massive single distributed system (Starlink constellation).
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