You are here

High Performance Radiation Hardened Solar Power

Description:

TECHNOLOGY AREA(S): Space Platforms 

OBJECTIVE: Develop high-efficiency, radiation-tolerant solar array technology that retains high end-of-life efficiency after many passes thru the radiation belts in a solar-electric orbit raising trajectory. 

DESCRIPTION: The Air Force is pursuing a development path towards a High Power Solar Electric Propulsion (HPSEP) Orbital Transfer Element (OTE) to deliver next generation Space Enterprise Vision (SEV) satellites from either a LEO parking orbit or a geosynchronous transfer orbit (GTO) to higher energy orbits including MEO (for GPS), GEO, and HEO. These OTE’s leverage low thrust orbit transfer to achieve dramatic reductions in required launch mass. However they do require many months to complete the delivery of the satellite to its final mission orbit. Currently, several NSS spacecraft, including AEHF and WGS, employ low thrust trajectories to transfer from GTO to their final GEO orbits. Modern solar arrays undergoing development and qualification, such as the Deployable Space Systems’ ROSA and Orbital ATK’s Megaflex, offer greater than 130 W/kg beginning of life (BOL) specific power, and BOL packaging densities of well over 20 kW/m^3. However, these arrays currently employ traditional multijunction solar cells that suffer from an unacceptable, radiation induced ~25% loss in power output during an 8 month low thrust LEO to GEO transfer through the Van Allen belts. Therefore, advanced solar cells and/or blanket/panel designs are sought that offer (1) an EOL to BOL ratio that is >>75% after 5 round-trips through the Van Allen belts (energetic particle exposure may exceed 1e17 1 MeV equivalent electrons/cm^2), (2) >130 W/kg BOL array-level specific power, and (3) >20 kW/m^3 BOL array-level stowed volume efficiency when integrated in advanced solar array structural architectures. Note that new solar array structural/deployment architectures are not sought. Instead, solar cell/blanket/panel technologies are sought that can be integrated into existing, higher TRL approaches (e.g. ROSA and Megaflex) to provide the enhanced radiation tolerance. In addition, the solar cell and/or solar blanket/panel technology developed should be capable for passing AIAA S-111 and AIAA S-112 qualification testing. One potential approach is to use solar concentrating technology that is suitable for integration into advanced high performance solar arrays. Concentrators can substantially reduce the solar cell area that requires coverglass protection, which allows relatively thick coverglass material to be used with minimal mass penalty. Of course, one challenge is to achieve the solar concentration with an optical system mass that does not exceed the savings offered by reducing the required coverglass material. In addition, concentrating systems should not impose overly restrictive solar pointing requirements that significantly exceed what is typical for conventional solar arrays. 

PHASE I: Develop solar cell or solar blanket/panel designs that can be integrated with existing high performance solar array structural architectures and provide the desired radiation tolerant performance for the OTE mission. Perform preliminary testing and analysis of the identified options, and use that data to predict the array performance potential. 

PHASE II: Leveraging the development and testing performed in Phase I, mature the most promising cell and/or blanket/panel options. Perform required testing and analysis to understand the technology behavior in the OTE mission and design for integrating the technology into an existing high-performance solar array. The goal is to have the technology matured to TRL 4 or higher at the end of the Phase II effort. 

PHASE III: Fly technology demonstration unit on-board an OTE demonstration to be flown in the 2022-2023 timeframe. SMC/AD, SMC/LE, and NASA are collaborating on this development. Take in-space measurements of the performance to verify ground testing results and provide TRL 6 final products. 

REFERENCES: 

1: Jay P. Penn, John Mayberry, Chris Ranieri, and O'Brian Rossi. "Re-Imagining SMC’s Fleet with High-Power Solar Arrays and Solar Electric Propulsion", AIAA SPACE 2014 Conference and Exposition, AIAA SPACE Forum, (AIAA 2014-4328)

2:  Lynn Capadona, Jeffrey Woytach, Thomas Doehne, David Hoffman, Mark Klem, Robert Christie, Eric Pencil, Tyler Hickman, Robert Scheidegger, Feasibility of Large High-Power Solar Electric Propulsion Vehicles: Issues and Solutions, AIAA SPACE 2011 Conference & Exposition Long Beach, California

3:  David C. Byers and John W. Dankanich. "Geosynchronous-Earth-Orbit Communication Satellite Deliveries with Integrated Electric Propulsion", Journal of Propulsion and Power, Vol. 24, No. 6 (2008), pp. 1369-1375

4:  Julie Rodiek, Henry Brandhorst, and Mark O'Neill. "Stretched Lens Solar Array: The Best Choice for Harsh Orbits", 6th International Energy Conversion Engineering Conference (IECEC), International Energy Conversion Engineering Conference (IECEC), (2008)

KEYWORDS: High-efficiency, Radiation-tolerant, Solar Array, HPSEP 

CONTACT(S): 

David Wilt (Aerospace Corp, SMC/AD) 

(505) 846-2462 

david.wilt@us.af.mil 

US Flag An Official Website of the United States Government