Advanced aerobots that would be powered by solar photovoltaic batteries and that would be capable of storing energy for occasional operation during short intervals at power levels far beyond those of the photovoltaic batteries have been proposed. Aerobots are robotic balloon-buoyed airborne apparatuses that can be used for exploration of other planets and can be used on Earth for diverse purposes, including monitoring weather, military and law-enforcement surveillance, and entertainment.
The aerobots that have been built thus far utilize various combinations of atmospheric and transported gases for buoyancy control, subject to limitations of available power. The operation of the proposed aerobots would be much less restricted by limitations of available power because they would utilize solar energy and would store excess solar energy in various ways for consumption during such power surges as might be needed for rapid ascents, drilling into the ground, transmitting signals, or other short-term functions.
According to the proposal, part or all of a balloon surface would be covered with solar photovoltaic cells. Detailed calculations show that, with state-of-the-art photovoltaic technology, the mass penalty would be less than 10 percent, since the substrate is already available as the balloon surface. The electric power generated by the cells could be used to electrolyze, compress, liquefy, or freeze a transported or atmospheric gas or to sublimate or boil a frozen or liquid phase of an atmospheric or transported gas. Such physical and chemical manipulations of atmospheric and/or transported gases would be performed to effect changes in buoyancy, to store energy, or to satisfy demands for power surges, depending on circumstances. To cite three examples:
- Products of electrolysis could be stored in canisters or balloon compartments and later consumed in a fuel cell to generate a surge of electric power.
- A compressed gas could be released to provide a rapid change in buoyancy and/or a surge of propulsive force, which could be directed horizontally or could be directed wholly or partly vertically to aid or oppose the change in buoyancy.
- An atmospheric gas could be condensed or frozen to take on ballast and later allowed to warm up toward ambient temperature to release ballast.
This work was done by Kumar Ramohalli of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Machinery/Automation category, or circle no. 189 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).
NPO-20155
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Solar-powered aerobots with power-surge capabilites
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Overview
The document presents a proposal by NASA for solar-powered aerobots that utilize advanced balloon technology to enhance aerial exploration capabilities on planetary bodies, particularly Mars. The primary innovation lies in integrating photovoltaic (PV) cells into the surface of the balloons, allowing them to generate electrical power from solar energy. This approach addresses the challenge of power limitations faced by traditional systems, enabling the aerobots to perform a variety of functions, including rapid mobility, surface exploration, and subsurface drilling.
The document outlines the technical aspects of the proposed system, emphasizing the use of the balloon's surface as a substrate for PV cells. With a representative balloon diameter of 10 meters, the system can generate approximately 1 kW of power, sufficient for various scientific experiments and operational needs. The PV cells, operating at a conversion efficiency of 15%, require only a small area of the balloon's surface, leaving ample space for other functionalities, such as radiators for heat rejection.
A significant application of the generated power is in In-Situ Resource Utilization (ISRU), specifically the condensation of Martian carbon dioxide (CO2) into solid form for ballast. The document details the energy requirements for this process, indicating that with 1 kW of power, the system can efficiently condense CO2, which can later be vented to adjust buoyancy as needed.
The proposal also highlights the potential for energy storage, allowing the aerobots to manage power surges for tasks that require sudden bursts of energy, such as rapid ascents or drilling. The ability to electrolyze atmospheric gases and store the products for later use further enhances the operational flexibility of the aerobots.
Overall, the document emphasizes the novelty of combining solar energy with traditional balloon technology to create a versatile platform for scientific exploration. By overcoming power constraints, these solar-powered aerobots could significantly advance our capabilities in planetary exploration, enabling more extensive and efficient missions on Mars and potentially other celestial bodies. The integration of renewable energy sources into robotic systems represents a promising direction for future space exploration endeavors.
