A new type of (diffractive) solar sail could revolutionize space exploration

voile solaire diffractive

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In program NASA’s innovative advanced concepts (NIAC), the US space agency has selected a solar sail project that could pave the way for new destinations. This innovation, called Diffractive Solar Sails, could prove to be much more efficient than existing solar sails. Thanks to the diffraction phenomenon, it can make the most of all the sunlight it collects. A spacecraft equipped with this sail would therefore be more efficient and more manoeuvrable.

Most spacecraft today run on rocket propulsion or ion engines. It is therefore strange to imagine a space sailing ship. However, the solar sail drive has already proved its worth. Of course, due to the low thrust generated, this device does not allow the machine to leave the ground, but it is quite applicable to devices in orbit or after reaching the escape velocity.

The concept was particularly tested by the Japanese Space Agency (JAXA), which in 2010 launched its IKAROS spacecraft equipped with a 200 m2 polyimide solar sail covered with solar cells on 10% of its surface. The purpose of this technological demonstration was to evaluate the performance of this type of drive. Recently, The Planetary Society – a global non-profit organization dedicated to space exploration – also tested solar navigation through two projects, LightSail 1 and LightSail 2, which were launched in 2015 and 2019. LightSail 2 continues its mission today and enables the collection of key data on this type of drive.

Tarpaulin based on the diffraction phenomenon

The solar sails work due to the pressure exerted by photons of sunlight (so-called radiation pressure) when they hit their surface. This force is relatively weak, but the larger and more reflective the sail, the more it increases (if the particle bounces instead of being absorbed, it transmits twice its momentum). By adjusting the slope of the sail, it is possible to act on the applied force – by offering the light a larger or smaller area of ​​the sail – and thus to steer the vessel (like a sailboat).

The main advantage of this type of propulsion is that it allows you to do without fuel, which gives the ship a very long range to explore the solar system. However, the concept has certain limits: the thrust is maximal only when the light rays point directly at the sail. Maneuverability is therefore limited because a ship equipped with such a sail cannot move in any direction.

The goal of the Diffractive Solar Sail project is to circumvent this “defect”. This technology actually takes advantage of the phenomenon of light diffraction. When light waves hit the edges of an obstacle (such as a slit or other narrow hole in an opaque panel), they deviate from their original trajectory and propagate 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 nets integrated into thin films that will distribute the received light throughout the sail. Theoretically, this will allow the spacecraft to use sunlight more efficiently without sacrificing maneuverability.

This technology could make it possible to predict missions to places that are particularly difficult to access by traditional propulsion methods, such as orbits around the Sun’s poles. Scientific instruments placed in this position would improve our understanding of the Sun as well as our ability to predict space weather.

Major project for heliophysical science

Exploring the universe means we need new tools, new ideas and new ways to move Jim Reuter, an associate administrator of NASA’s Space Technology Mission Directorate (STMD), said in a statement. That is why NASA does not hesitate to invest in the most creative and promising projects. ” Our goal is to change the possible and Diffractive Solar Sail promises this in a number of exciting new missions. added Mike LaPointe, acting program manager at NIAC.

Now that the diffractive solar sail has been selected for Phase III of the NIAC program, the project team – led by Amber Dubill of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland – has $ 2 million in funding. its technology.

The tarpaulin must be firm and light. Due to the diffraction effect, it can be smaller than the solar sails tested so far. Dubill and his colleagues have already designed, developed and tested different types of diffraction veil materials; their new funding further optimizes this material. Several ground tests are also planned to best prepare for future missions.

The team believes that its diffractive sail will provide unrivaled Sun observation capabilities; it also plans to place the entire constellation of diffractive sails around the Sun to gather images and other data. “ With our team’s combined expertise in optics, aviation, traditional solar sails and metamaterials, we hope to enable scientists to study the Sun like never before. said the project manager.

Source: NASA

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