A new type of solar sail could revolutionize space exploration

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In a program Advanced innovative NASA concepts (NIAC), the US space agency has selected a solar sail project, which could open the way to new destinations. This innovation, called Diffractive Solar Sail, could be more efficient than existing solar sails. Thanks to the phenomenon of diffraction, it can make the most of all the collected sunlight. So a spacecraft equipped with this sail will be more efficient and maneuverable.

Most spacecraft today run on rocket propellant or ion engines. So it’s strange to imagine a sailing ship traveling through space. However, the solar gliding propulsion system has already proven itself. Due to the low output thrust, this device obviously does not allow the machine to leave Earth, but it is fully usable on devices that are in orbit or have reached escape velocity.

The concept was notably tested by the Japan Aerospace Agency (JAXA), which in 2010 launched its IKAROS spacecraft equipped with a 200-square-meter polyimide solar sail, covered with solar cells on 10% of its surface. This technology demonstration is intended to evaluate the performance of this type of payment. Recently, The Planetary Society – a global non-profit organization dedicated to space exploration – also tested solar navigation with two projects, LightSail 1 and LightSail 2, launched in 2015 and 2019 respectively. LightSail 2 continues its mission today and allows basic data to be collected about this payment mode.

A sail based on the phenomenon of diffraction

Solar sails work due to the pressure that photons of sunlight exert (called radiation pressure) when they hit their surface. This force is relatively weak, but the larger and more reflective the sail, the greater its increase (if a particle is reflected rather than absorbed, it transmits twice its momentum). By adjusting the inclination of the sail, it is possible to act on the force applied – by presenting a sail surface more or less to light – and thus guiding the vessel (such as a sailing boat).

The main advantage of this mode of propulsion is that it makes it possible to do without fuel, giving the ship a very long range to explore the solar system. However, the concept shows certain limits: thrust is at its maximum only when the rays of light are directed directly at the sail. Thus, maneuverability is limited, since a ship equipped with such a sail cannot move in any direction.

The fission solar sail project specifically aims to circumvent this “defect”. In fact, this technique exploits the phenomenon of diffraction of light. When light waves encounter the edges of an obstacle (eg an slit, or other narrow slit, on an opaque plate), they are deflected from their initial path and scattered in different directions on the other side. This is exactly the effect that this new solar sail seeks: it will therefore consist of several small networks embedded in thin films, which will distribute the received light over the entire sail. In theory, this would allow the spacecraft to use sunlight more efficiently without sacrificing maneuverability.

This technology could make it possible to visualize missions to places that are particularly hard to reach via traditional propulsion patterns, such as orbits around the sun’s poles. Scientific instruments placed in this position will improve our understanding of the Sun, as well as our ability to predict space weather.

A critical project for solar physics

Exploring the universe means we need new tools, new ideas, and new ways to get around Jim Reuter, associate administrator for NASA’s Space Technology Mission Directorate (STMD), said in a statement. That is why NASA does not hesitate to invest in the most innovative and promising projects. ” Our goal is to change the possible, and Solar Split Sail promises to do so for a number of exciting new mission applications. Mike LaPointe, NIAC’s Acting Program Director added.

Now that a fission solar sail has been selected for the third phase of the NIAC program, the project team — led by Amber Dubill of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland — has secured $2 million in funding over two years to continue development of its technology.

The sail must be strong and light. Thanks to the phenomenon of diffraction, it may be smaller than the solar sails tested so far. Dobell and his colleagues have already designed, created and tested different types of materials for refractive sails. Their new funding will improve these materials. Several ground tests are also planned to better prepare for future missions.

The team is confident that its yaw sail will provide unparalleled solar monitoring capabilities; It also plans to place an entire constellation of reflective solar sails around the sun, to collect images and other data. “ With our team’s combined expertise in optics, space, conventional solar sail and metamaterials, we hope to enable scientists to study the Sun like never before. said the project manager.

Source: NASA

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