Solar augmentation

Design and Structure

The VSAT/RSA concept is built around a central telescoping mast that extends to 10 m, carrying a horizontal cross arm from which a pair of flexible solar cell blankets hang freely. NASA technical documentation describes the configuration as "a pair of solar cell blankets freely hanging from a horizontal cross arm supported by a vertical, slender, telescoping mast resting on a deployable tripod base." The blankets hang on either side of the cross arm, presenting a vertical photovoltaic surface optimised for the low solar elevation angles characteristic of the lunar south pole.

The vertical orientation is a deliberate engineering choice: at south-polar latitudes the Sun never rises more than a few degrees above the horizon, so a horizontal array would generate little power and would be easily shadowed by surface features. Elevating the blankets 10 m above the surface extends the array's line-of-sight to the Sun across local terrain, enabling near-continuous energy generation even through local winter periods.

Deployment is designed to be largely autonomous. The telescoping mast extends using a winch-and-cable system, and the solar blankets unfurl in a manner analogous to a Venetian blind. The lunar gravitational environment — one-sixth of Earth's — enables the use of extremely slender, low-mass structural members that would be impractical under higher gravity. The deployable tripod base provides stability on unprepared regolith with slopes up to 15 degrees. Once deployed, the system can be stowed and relocated to a new site without loss of functionality, with the design supporting up to ten separate redeployments over its ten-year service life.

The solar blanket assembly accounts for approximately 36 kg, with the upper and lower cross arms, winch, and cable deployment hardware adding roughly 14 kg, for a combined blanket-and-structure mass of approximately 50 kg. The entire 10 kW system stows in a volume of approximately 0.5 m³, corresponding to a packaging power density of about 20 kW/m³.

Electrical Architecture and Grid Integration

Each VSAT unit is sized to deliver approximately 10 kW at around 100 VDC on the array side. NASA's emerging International Space Power System Interoperability Standard (ISPSIS) defines 120 VDC as the standard exchange voltage between sources and loads at distances under 100 m, and surface microgrids are generally designed for the 120–200 VDC range at the source and load interface.

For power distribution over longer distances — up to 10 km between solar or fission sources and remote loads — NASA architecture studies call for step-up conversion to higher transmission voltages (1,000–1,500 VDC or greater than 3,000 VAC at approximately 1 kHz), with a target distribution loss of no more than 3 percent per kilometre. A representative power conversion component described in NASA technical literature is the Universal Modular Inverter/Converter (UMIC) rack, which operates at a nominal 10 kW (12 kW peak), converts between a 120 VDC source/load interface and a three-phase, approximately 3,000 VAC, 1,000 Hz grid side, targets a power density of approximately 350 W/kg at flight specification, and achieves efficiency greater than 95 percent. Multiple UMIC units can be paralleled to deliver more than 10 kW at a single location.

Individual 10 kW VSAT units are intended to function as modular building blocks for larger surface power networks. NASA architecture documents treat surface solar modules in the 2 kW to 10 kW range as standard aggregation units, with multiple units combined at a site or distributed across a local grid to meet the power demands of habitats, science payloads, rovers, and in-situ resource utilisation (ISRU) systems.

Energy Storage

Solar augmentation systems are paired with surface energy storage to buffer periods when solar generation is interrupted or reduced. A storage capacity of approximately 360 kWh, which appears in surface power architecture studies as a representative figure for an early Artemis-class outpost, can serve different roles depending on the site and solar architecture.

At an equatorial site where the lunar night lasts approximately 14 Earth days (roughly 336 hours), a 360 kWh storage system could sustain a survival load of approximately 1.1 kW continuously through the full night, or support higher-power operations — such as ISRU processes or habitat peak loads of 10–15 kW — for shorter durations. At a near-polar site equipped with VSAT systems that achieve near-continuous sunlight, 360 kWh functions primarily as contingency storage, providing approximately 36 hours of full 10 kW backup in the absence of solar input, with substantially longer coverage at reduced emergency load levels.

NASA microgrid analyses for lunar ISRU base-camp scenarios treat energy storage as a central DC microgrid element, sized from load profiles, maximum charge and discharge power requirements, and the defined operating time horizon. In ISRU microgrid contexts, a 360 kWh energy storage system (ESS) would typically support one or more 10–20 kW-class processes such as water electrolysis or mineral processing for several hours, and provide load levelling between variable ISRU demand and the relatively steady output of a solar array.

Lithium-ion batteries are the most likely near-term baseline technology for lunar surface energy storage, given their spaceflight heritage and energy density. At a system-level specific energy of 150–200 Wh/kg — accounting for cells, packaging, thermal management, and battery management electronics under lunar-qualified design — a 360 kWh system implies a mass of approximately 1,800 to 2,400 kg. Actual mass is driven as much by the required power capability in kilowatts as by the energy capacity in kilowatt-hours, since high discharge rates demand additional parallel cell strings. NASA guidance also identifies Hybrid Energy Storage Systems (HESS), which combine high-energy-density batteries with high-power-density capacitors or other devices, as a potential approach to improving lifecycle performance under the thermal and radiation environment of the lunar surface.

Solar Augmentation vs. Fission Surface Power

NASA and the U.S. Department of Energy have identified nuclear fission surface power as the primary power generation technology for sustained human presence on both the Moon and Mars, with solar augmentation treated as a secondary or supplementary source rather than the baseline. The fundamental driver is assured, continuous power under environments where sunlight is intermittent or unreliable.

On the Moon, the 14-Earth-day lunar night at most latitudes makes continuous solar-only operation very difficult without enormous energy storage systems. Near south-polar permanently shadowed regions (PSRs), which contain scientifically valuable water-ice deposits, solar energy is unavailable entirely. Fission systems are designed to produce 10–40 kW of electrical power continuously for at least ten years, independent of the day-night cycle and shadowing conditions. Four approximately 10 kWe fission units are described in NASA and DOE documentation as sufficient to support robust early outpost operations. Lockheed Martin and DOE materials emphasise that such systems can operate continuously through multi-week lunar nights and in shadowed craters where solar systems are ineffective. In this architecture, solar augmentation provides supplemental power where illumination is adequate — particularly at near-polar sites with favourable terrain — but is not the baseline generation source.

For Mars, NASA's 2024 Mars Surface Power Technology Decision report documents a formal trade study comparing nuclear fission systems against photovoltaic arrays plus energy storage. Although solar power carries lower per-unit cost, NASA concluded that fission is more robust and better suited to the Martian environment. Key fission advantages cited include consistent power at many landing sites around the clock, independence from the approximately 12-hour Martian night and from seasonal insolation variation, and resilience during global dust storms that can last weeks to months and reduce or eliminate solar generation. Mars surface solar flux reaches at most about 45 percent of typical Earth values and varies strongly with latitude and season. Additionally, because Mars gravity is roughly twice that of the Moon, large deployable solar structures originally designed for lunar gravity require higher structural strength for Mars deployment. NASA therefore baselined fission power as the primary surface power technology for initial crewed Mars missions on robustness, scalability, and reliability grounds.

Across both destinations, the long-term architectural vision combines fission surface power with solar arrays, batteries, and fuel cells. Fission provides assured base-load power for life support, habitat thermal control, and critical ISRU, while solar contributes variable, peak, or distributed power for remote assets and non-critical loads. NASA and DOE literature describes this hybrid approach as the preferred framework for sustained human and robotic presence on and around the Moon and Mars.

Recent Technology Developments

VSAT development is led by NASA's Space Technology Mission Directorate Game Changing Development program with involvement from Langley Research Center and Glenn Research Center. In 2024, NASA selected three companies — Astrobotic, Honeybee Robotics, and Lockheed Martin — to further develop deployable solar array systems for the Moon, awarding a combined total of $19.4 million for prototype development and environmental testing.

In the broader domain of rigid deployable solar arrays relevant to surface power, recent developments have pushed specific power toward 50–80 W/kg at flight specification for rigid panel systems, compared with the historical norm of approximately 25–45 W/kg. Commercial offerings include Sierra Space's deployable rigid solar arrays, which use surface-mount technology (SMT) micro-cells with a packing density greater than 95 percent, providing 10–40 percent higher power density than conventional layouts; an example wing configuration delivers 3.2 kW and the product line is described as scalable to a wide range of power levels. Sierra Space SMT panels have been selected and qualified for lunar surface missions, with a rated operating temperature range of −240 °C to +160 °C. MMA's compact rigid-flex PCB-based Hawk array has demonstrated specific power up to 121 W/kg. These developments establish a clear commercial path toward modular wings in the 1–5 kW range that can be aggregated into 10–30 kW surface systems.

NASA analysis of solar power for non-nuclear planetary exploration explicitly identifies the need for low-risk, lightweight solar arrays in the 10–30 kW range. At 30 kW, improving specific power from 80 W/kg to 200 W/kg yields a mass saving exceeding 200 kg — a significant factor for landed surface systems where every kilogram of delivered mass carries a high cost.