Steering the Deep Space Gateway with a Solar Sail.

NASA, international partners consider solar sail for Deep Space Gateway

Anatoly Zak * September 25, 2017 It sounds like it comes straight from an Arthur C. Clarke story, but an international team of engineers is considering equipping a future human outpost orbiting the Moon with a solar sail.

 From article, (It sounds like it comes straight from an Arthur C. Clarke story, but an international team of engineers is considering equipping a future human outpost orbiting the Moon with a solar sail. Harnessing the slight pressure of solar radiation, a super-thin reflective film might help steer the Deep Space Gateway, or DSG, which is being designed by five space agencies to succeed the International Space Station.

The baseline concept used for initial calculations calls for a rectangular sail spanning an area of about 50 square meters, deployed on the exterior of the station by a robotic arm. This could reportedly save at least 9 kilograms of hydrazine per year needed to keep the outpost correctly oriented in space. Although a relatively small number, 9 kilograms per year adds up over the station's projected 15-year mission, especially when considering the tremendous cost of delivering cargo to lunar orbit. The station's current design allocates 135 kilograms of hydrazine fuel for counteracting gravitational disturbances, as well as solar radiation pressure exerted on the station's exterior in lunar orbit. At least part of this attitude-control job could be shifted to a solar sail.

When the solar sail is not needed, it could be either folded or hidden behind the station's solar panels relative to the Sun, so that solar radiation no longer presses on its surface.
To keep the mass of the sail to a minimum, engineers considered Dupont's polyamide film, which measures just 7 to 25 micrometers thick.

Before its journey to the vicinity of the Moon, a prototype of the sail could be brought to the ISS to test its deployment mechanism and operations.According to a NASA source, the solar sailing concept will need further analysis, but is already being seen as promising and considered to be a good candidate at least as a demonstrator aboard the DSG, if not a fully operational system.

The construction of the Deep-Space Gateway is expected to begin in the first half of the 2020s with the help of NASA's SLS rocket and Orion spacecraft. The near-lunar outpost will be the main destination for the Orion during the next decade, promising to give NASA and its partner agencies enough experience for human missions beyond the Moon and, possibly, to Mars in the 2030s.)

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