Entech Solar Space Technology
Background
Entech Solar and its predecessor organization, ENTECH, Inc., have been involved in space solar array R&D for NASA (National Aeronautics and Space Administration), the U.S. Department of Defense (DOD), and aerospace companies in the USA since 1986. Entech Solar and its government/industry/academia team have developed a series of ever-improving refractive photovoltaic concentrators for space power applications.
Each new generation has provided higher performance at lower mass, stowed volume, and cost. The basis of Entech Solar’s space solar array technology is a high-efficiency, low-mass, highly error tolerant refractive Fresnel lens concentrator which captures and focuses space sunlight onto high-efficiency multi-junction solar cells. Entech’s space concentrator technology has flown in space on flight experiments [e.g., the USAF/NASA PASP+ (Photovoltaic Array Space Power Plus Diagnostics) flight test in 1994-95] and as the primary power source for a NASA/JPL spacecraft (Deep Space 1), with excellent performance and durability on orbit.
The SCARLET (Solar Concentrator Array with Refractive Linear Element Technology) performed flawlessly during an exciting three-year mission to visit both an asteroid (Braille) and a comet (Borrelly). SCARLET powered not only the spacecraft, but also the ion engine which propelled the spacecraft throughout the Deep Space 1 mission. SCARLET was also the first array to use triple-junction cells to power a spacecraft. SCARLET was awarded the NASA TGIR (Turning Goals into Reality) award and the Schreiber-Spence award.
Entech’s newest concentrator array is the Stretched Lens Array (SLA), a remarkably lightweight and efficient space power system with unprecedented performance metrics. SLA recently was highlighted by NASA in a technology success story which describes how Entech Solar’s space technology and ground technology are truly synergistic. Entech Solar’s space power heritage and technology evolution are shown in the graphic to the right.
Entech Solar’s SLA offers significant space power system advantages, such as low mass, low stowed volume, high efficiency, high-power and high-voltage capabilities, for most space operations including those for NASA, the military and commercial missions. The SLA offers specific and significant additional advantages for military missions in space, including improved hardness and survivability against nuclear and laser attack. Hardness against degradation or damage from both natural and manmade hazards in space is a key attribute of major importance to military missions.
Since SLA focuses sunlight by typically about 10X, the solar cells only cover about one-tenth as much area as for a one-sun array of equal power output. Therefore, the solar cells can be heavily shielded with transparent material on the illuminated side and any material on the non-illuminated side to block the damaging effects of electrons and protons and other charged particles on solar cells. This is important for “belt flyers” which travel through the high-radiation Van Allen belts, and also for any military spacecraft which could be affected by a nuclear weapon detonation near its orbit. Laser hardness is also easier to achieve with the small cells and optical concentration of SLA.
In summary, Entech Solar’s Stretched Lens Array (SLA) has a unique, lightweight, and efficient design that leads to outstanding performance metrics in real power density (watts per square meter), stowed power density (kilowatts per cubic meter), specific power (watts per kilogram) and overall cost-effectiveness. SLA’s intrinsic design characteristics also protect against electrical discharge, micrometeoroid impacts, radiation degradation, and other natural/manmade degradation events.
SLA can also provide arc-free high voltage operation because the solar cell strings/circuits are significantly separated from one another, and can be more robustly encapsulated from the space environment, minimizing space plasma interactions. The SLA is particularly well suited to Solar Electric Propulsion (SEP) missions in space, including reusable space tugs for carrying cargo from low earth orbit to geostationary orbit, lunar orbit, Mars orbit, or beyond.
Present Activities
In response to emerging space power demands, Entech Solar is continuing to work with NASA, DOD, and its aerospace partners to develop even more advanced space solar array technologies to enable future space missions. The new solar array technology under development through funding from NASA provides game-changing affordability, scale-up, and performance to enable future missions with high power requirements.
