NASA Developing Solar-sailing Cubesats for Inaugural SLS Launch

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WASHINGTON — NASA is developing a pair of solar-sailing, science-collecting cubesats that will hitch a ride on the Space Launch System’s inaugural July 2018 launch.

The two spacecraft, currently envisioned as six-unit cubesats with deployable solar sails, will travel beyond low Earth orbit to conduct scientific observations of an asteroid and the moon.

NASA’s Near Earth Asteroid Scout, or NEA Scout, cubesat will conduct a 2020 flyby of asteroid 1991 VG to determine its size, movement and chemical composition.

The aptly named Lunar Flashlight cubesat will sail into a polar orbit around the moon by early 2019 then use its solar sail as a mirror, reflecting sunlight onto the cold, dark regions of the lunar poles. Once the polar regions are illuminated, onboard sensors will help determine the composition and distribution of frozen water and other volatiles hidden in the moon’s shadows.

NEA Scout and Lunar Flashlight are being led by principal investigators based, respectively, at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the Marshall Space Flight Center in Huntsville, Alabama.

JPL spokesman DC Agle told SpaceNews in an email that both missions completed mission concept and system requirements reviews last fall. Initial estimates show the missions will cost about $16 million each, he said.

Assuming the missions stay on track, Lunar Flashlight and NEA Scout will be the second and third solar sailing spacecraft to venture beyond Earth orbit. Japan’s Ikaros spacecraft was the first to do so when it deployed a thin sail in 2010 and relied on the sun’s gentle push to complete a six-month voyage to Venus.

Although the acceleration due to sunlight is slow, solar sailing technology offers a way to build a spacecraft that does not require onboard propellant and that can reacher higher speeds than conventional chemical propulsion systems over time. That said, the technology and techniques used to drive spacecraft with a solar sail are still largely experimental.

NASA had planned to launch a solar sail mission called Sunjammer this year but canceled project, which included the spacecraft and its 1,200-square-meter solar sail, due to a lack of confidence in the contractor’s ability to complete the vehicle on time.

NASA’s longstanding interest in developing propellent-free technologies goes beyond the NEA Scout and Lunar Flashlight cubesats. In early July, NASA awarded funding to a team from the Marshall Space Flight Center in Huntsville, Alabama, for continued study of a an electric solar sail. The concept uses positively charged wires that could deflect protons emitted in solar wind and gently push the spacecraft. Researchers predict this form of solar sailing could be faster than the current method of using ultra-thin, mirror-like sails to harness solar pressure.

The most recent solar sail spacecraft to be sent into orbit was the Planetary Society’s LightSail cubesat. The experimental spacecraft, which launched in May, encountered software glitches and computer crashes while on orbit but finally deployed its sail in June, successfully completing it mission to test solar sail hardware for a more ambitious follow-on mission.

The Pasadena, California-based Planetary Society plans to launch its second solar sail cubesat in 2016. When it does, NASA will be watching and learning from the non-profit’s successes or failures.

“The Planetary Society has agreed to let us observe and also to share any lessons they have learned about solar sails,” Agle said. Both parties have signed a Space Act Agreement outlining the details of their cooperation.

When NASA’s Space Launch System launches the Orion spacecraft in 2018 on an unmanned test flight, it will stow 11 six-unit cubesats behind the capsule in the stage adapter. Once Orion decouples from the adapter, the breadbox-sized satellites will be free to go about their missions.

NASA’s Human Exploration and Operations Directorate, Space Technology Mission Directorate, and Science Mission Directorate are in charge of selecting the eleven cubesats.

Kathryn Hambleton, a NASA spokeswoman, said in an email to SpaceNews that besides Lunar Flashlight and NEA Scout, only one other cubesat, BioSentinel, has been selected so far.

The BioSentinel mission, managed my NASA’s Ames Research center in Mountain View, California, will observe the effect of deep space radiation on yeast to see how organisms react to such environments.

Hambleton could only confirm that NEA Scout and Lunar Flashlight are using solar sails for propulsion, but she did say future selections could have them as well.

Using its solar sail, it will take two years for NEA Scout to reach its asteroid. Lunar Flashlight, for comparison, will need an estimated 18 months to reach a lunar orbit. Agle said that these travel-time estimates are based upon a July 2018 launch, and may change if the Space Launch System/Orion launch is further delayed.