Description: Spacecraft thermal control is a critical element to maintaining spacecraft, manned, unmanned or robotic, at proper temperatures for humans, instruments and electronics to function properly. Simple, passive thermal control in which excess heat is radiated to space via blackbody radiators used to be adequate, however, as spacecraft power levels increase and mission environments become more complex, more flexible and capable thermal control systems and mechanisms are needed. Variable heat rejection is an enabling technology to reliably vary heat rejection during human and robotic spaceflight missions with wide variation in thermal environments & vehicle heat loads. Quest Thermal Group is proposing a novel Variable Gas-Conductor Radiator (VGCR) that uses variable gas conduction within an IMLI structure to control heat conduction. A VGCR could provide both high and very low heat rejection, operating as both effective radiators and high performance insulation, and capable of turndown ratios of 76:1. The NASA 2012 TA14 Thermal Management Roadmap stated radiator advancement is perhaps the most critical thermal technology development for future spacecraft and space-based systems. NASA is seeking unique solutions for thermal control technology providing low mass highly reliable thermal control systems. As NASA moves beyond LEO, spacecraft must accommodate various mission scenarios and need variable heat rejection. Current state of the art variable radiators offer heat rejection turn-down ratios up to about 4:1. Phase I goals are to develop a new variable spacecraft radiator that can simply and efficiently provide a highly variable heat rejection using variable gas conduction within IMLI insulation, and prove feasibility of the VGCR concept to help improve radiator capabilities for future NASA and commercial spacecraft. A VGCR prototype will be modeled, designed, built and tested for thermal performance and variable heat rejection.

Benefits: NASA's Thermal Management Roadmap emphasizes the need for variable heat rejection. As NASA moves beyond LEO, exploration vehicles and space instruments must accommodate various mission scenarios, operating in environments from full sun to deep space, managing a wide range of heat rejection. Variable radiators are needed that can be turned down to low heat flux in cold environments. Current state of the art turndown ratios are 4:1, NASA's goal is 6:1, and Quest's Variable Gas-Conductance Radiator (VGCR) is modeled to have a turndown ratio of 76:1. Advances in heat rejection technologies could provide more capable thermal control across a wider range of thermal environments and heat loads. Variable radiators offer substantial system-wide benefits, including lower power requirements to maintain spacecraft temperatures in cold environments. Variable radiators are an important enabling technology needed for NASA's future exploration and science missions. It is needed for NASA Design Reference Missions 8 & 9, which are crewed missions to Mars. Both NASA Science and Space Technology Mission Directorates are seeking new technology. VGCR technology, if proven successful, could be infused into future NASA spacecraft, including manned spacecraft, robotic exploration vehicles, Earth observing satellites, science and interplanetary spacecraft. VGSR could help NASA meet needs for improved spacecraft thermal control for various spacecraft and mission environments.

All commercial satellites require thermal control systems. The purpose of the thermal control system is to maintain the spacecraft or satellite within allowable temperature limits for all thermal environments it operates in. Spacecraft and related equipment (such as electronics or optics/sensors) require some level of thermal control, and the design approach and technologies employed vary widely depending on application. As spacecraft power levels increase and mission environments become more complex, more flexible and capable thermal control systems and mechanisms are needed. A new, advanced, low mass, highly variable radiator would be of interest to satellite manufacturers, and once proven out and tested, could be fairly rapidly adopted and incorporated into new satellite thermal control systems. New satellites are being built and launched at an increasing rate, there were 285 large satellites launched in 2014. Many of these new spacecraft are high power requiring good thermal control and heat rejection capability. The target markets for VGCR technology are satellites and spacecraft. This includes future NASA spacecraft and commercial satellites, including those for communications, Earth observing and remote sensing, Defense, science, navigation, Earth imaging and meteorology. Aerospace companies supplying radiators include Orbital ATK, Lockheed Martin/Vought, Sierra Nevada Corp and SSL. These suppliers are target commercial customers for this new technology.