The High Altitude Airship (HAA) has various potential applications and mission scenarios that require onboard energy harvesting and power distribution systems. The energy source considered for the HAA s power budget is solar photon energy that allows the use of either photovoltaic (PV) cells or advanced thermoelectric (ATE) converters. Both PV cells and an ATE system utilizing high performance thermoelectric materials were briefly compared to identify the advantages of ATE for HAA applications in this study. The ATE can generate a higher quantity of harvested energy than PV cells by utilizing the cascaded efficiency of a three-staged ATE in a tandem mode configuration. Assuming that each stage of ATE material has the figure of merit of 5, the cascaded efficiency of a three-staged ATE system approaches the overall conversion efficiency greater than 60%. Based on this estimated efficiency, the configuration of a HAA and the power utility modules are defined.

/pdf/power-budget-analysis-for-high-altitude-airships-4bpekj415e.pdf

Power budget analysis for high altitude airships

The High Altitude Airship (HAA) has various potential applications and mission scenarios that require onboard energy harvesting and power distribution systems. The energy source considered for HAAs is solar photon energy that allows the use of either photovoltaic (PV) cells or advanced thermoelectric (ATE) converters. Both PV cells and an ATE system were briefly compared to identify the advantages of ATE for HAA applications in this study. Utilizing the estimated high efficiency of a three-staged ATE in a tandem mode, the ATE generates a higher quantity of harvested energy than PV cells for mission scenarios. When the ATE performance figure of merit of 5 is considered, the cascaded efficiency of a three-staged ATE system approaches an overall efficiency greater than 60%. Based on this estimated efficiency, the configuration of a HAA and the power utility modules are defined.

Power Technology for Application-Specific Scenarios of High Altitude Airships

Space debris in Earth orbit poses significant danger to satellites, humans in space, and future space exploration activities. In particular, the increasing number of unidentifiable objects, smaller than 10 cm, presents a serious hazard. Numerous technologies have been studied for removing unwanted objects in space. Our approach uses a short wavelength laser stationed in orbit to vaporize these small objects. This paper discusses the power requirements for space debris removal using lasers. A short wavelength laser pumped directly or indirectly by solar energy can scan, identify, position, and illuminate the target, which will then be vaporized or slow down the orbital speed of debris by laser detonation until it re-enters the atmosphere. The laser-induced plasma plume has a dispersive motion of approximately 105 m/sec with a Lambertian profile in the direction of the incoming beam [1-2]. The resulting fast ejecting jet plume of vaporized material should prevent matter recombination and condensation. If it allows any condensation of vaporized material, the size of condensed material will be no more than a nanoscale level [3]. Lasers for this purpose can be indirectly pumped by power from an array of solar cells or directly pumped by the solar spectrum [4]. The energy required for vaporization and ionization of a 10 cm cube (~ 2700 gm) of aluminum is 87,160 kJ. To remove this amount of aluminum in 3 minutes requires a continuous laser beam power of at least 5.38 MW under the consideration of 9% laser absorption by aluminum [5] and 5% laser pumping efficiency. The power needed for pumping 5.38 MW laser is approximately 108 MW, which can be obtained from a large solar array with 40% efficiency solar cells and a minimal area of 450 meters by 450 meters. This solar array would collect approximately 108 MW. The power required for system operation and maneuvering can be obtained by increasing solar panel size. This feasibility assessment covers roughly the power requirement, laser system, and a potential operational scenario.

Assessment Study of Small Space Debris Removal by Laser Satellites

A new power concept has been contemplated for High Altitude Airship (HAA) under the consideration of 
direct energy conversion cycles, such as photovoltaic (PV) cells and advanced thermoelectric (ATE) generator. 
The HAA has various potential applications and mission scenarios that require onboard energy harvesting 
and power distribution systems. Both PV cells and an ATE system were briefly compared to identify the 
advantages of ATE for HAA applications in this study. Utilizing the estimated high efficiency of a threestaged 
ATE in a tandem mode, the ATE generates a higher quantity of harvested energy than PV cells for 
mission scenarios. The ATE's performance figure of merit of 5 was considered to estimate the cascaded 
efficiency of a three-staged ATE system. The estimated efficiency of a tandem system appears to be greater 
than 60%. Based on this estimated efficiency, the configuration of a HAA and the power utility modules are 
defined. Conventional photovoltaic cells have been used 
for NASA's long duration airplanes, the solar-powered Pathfinder, and remotely piloted aircraft [1]. However, the 
cost and weight of high efficiency photovoltaic cells pose a shortcoming for wide and unlimited applications. 
Among others is the fuel cell, but it is a fuel-carrying power generation system. A conceptual study for the HAA 
power budget plan has been done at NASA Langley Research Center by utilizing new nanomaterials for solar power 
harvesting.

Wireless power technology for application-specific scenarios of high-altitude airships

Recent progress with powerful, efficient, and coherent monolithic diode master-oscillator/power-amplifier (M-MOPA) systems is promising for the development of a space-based diode laser power station. A conceptual design of a 50-kW diode laser power module was made for space-based power stations capable of beaming coherent power to the moon, Martian rovers, or other satellites. The laser diode power module consists of a solar photovoltaic array or nuclear power source, diode laser arrays (LDAs), a phase controller, beam-steering optics, a thermal management unit, and a radiator. Thermal load management and other relevant aspects of the system (such as power requirements and system mass) are considered. The 50-kW power module described includes the highest available efficiency of LD M-MOPA system to date. However, the overall efficiency of three amplifier stages, including the coupling efficiency, turns out to be 55.5 percent. Though a chain of PA stages generates a high-power coherent beam, there is a penalty due to the coupling loss between stages. The specific power of the 50-kW module using solar power is 6.58 W/kg.

E. J. Conway

Papers

Diode laser power module for beamed power transmission