What’s so innovative about a “refracting solar sail” that NASA is paying attention? | sorae space portal site

NASA supports the innovative development of space「NIAC （NASA Innovative Advanced Concepts）」The program is led by a research group at Johns Hopkins UniversitySolar Sail Diffraction ProjectHe was selected for the third stage of 2022.

The NIAC project includes “Phase I” (duration: up to 9 months), which aims to explore feasibility and improve the level of technology readiness (TRL), and “Phase II” (duration: up to 2 months), which outlines a development roadmap. the year) ,“Phase III” Strategic planning for transition to a concept that will have the greatest impact on NASA (duration: up to two years)It consists of three stages. The 2022 Phase III open call for participants was announced in December 2021.May 2022The topic was selected for.

[▲ فيديو تعريف ناسا لمشروع NIAC]
credit: NASA

A solar sail is a spacecraft that moves using the “solar radiation pressure” generated when sunlight hits a sail, like a yacht using the wind to cross the sea.It is a source of paymentSunlight exists indefinitelyIt can not only be considered, but also compared to the existing propellantCheapThere is an advantage that it is.

Differences from JAXA “reflective” solar sail

The idea of ​​a solar sail was born in the late seventiesHowever, it was implemented by JAXA in 2010.AR IKAROS 」The project did not materialize. The current solar sail achieved by the IKAROS project is driven by the pressure of solar radiation generated when photons are reflected off the sail’s surface, so to speak.“reflector”I depend.

[ضغط الإشعاع الناتج عن حيود الضوء (الشكل الأيسر) وضغط الإشعاع الناتج عن انعكاس الضوء (الشكل الأيمن). ضغط الإشعاع الناتج عن F (Credit: Amber Dubill)]

In the case of a reflective solar sail, the larger the sail area, the greater the solar radiation pressure. However, with the increase in the sail area, the mass of the sail also increases and the thrust efficiency decreases, so it is necessary to make the sail from a lightweight material.

In addition, in order to accelerate or slow down the orbital speed, it is necessary to tilt the sail of the solar sail with respect to the direction of the incident sunlight. However, as the inclination of the sail increases, the solar radiation pressure cannot be efficiently allocated to the thrust.There is a trade-off between solar sail maneuvering and energy.It is said that there is a problem.

On the other hand, it was designed by a research group at Johns Hopkins University.“deviation”Solar sails generate solar radiation pressure by diffraction of light using the “diffraction phenomenon”.Since it is possible to obtain a driving force in a direction close to perpendicular to the direction of incident sunlight, the force generated by the photons can be used efficiently.called.comparison to reflective solar sails, according to Amber Dobel, who heads the research group.23% or moreIt is said that payment can be obtained efficiently.

Solar sail technology that facilitates access to the polar orbit of the sun

[▲ Antarctic of the Sun (Credit: ESA & NASA / Solar Orbiter / EUI Team) التي تم التقاطها بواسطة جهاز التقاط الصور فوق البنفسجية القصوى (EUI) للمركبة الفضائية الشمسية “Solar Orbiter”]

Although the sun’s north and south poles are thought to be the key to unraveling solar activity, current propulsion systems are difficult to use to launch spacecraft into polar orbits where the sun’s polar regions are easy to observe.“Ulysses”It was the only case where the distance was within 1.3 astronomical units (au)

.The solar probe is currently in operation by the European Space Agency (ESA)“solar orbit”In the event, even if the orbit is changed by oscillation using the gravitational pull of Venus and Earth, until it reaches the orbit within 0.3 au from the Sun and tilt angle of 25 degrees.3 yearsIt seems that it takes. On the other hand, “split” solar sails do not require the use of planetary gravity or additional fuel.You can reach an orbit of about 0.32 units from the Sun and an angle of inclination of 60 degrees.

is expected.
Connection・

A high-resolution image of the sun taken by the European spacecraft Solar Orbiter.

* Astronomical unit: The unit of distance with the distance from the Sun to the Earth as one astronomical unit.Johns Hopkins University Research Group, Selected for Phase III NIAC,$2 million in funding over the next two yearsIt is used for solar sailGround tests were conducted to improve metamaterials

It looks like it will be set to do so.

metamaterials: a synthetic material that manipulates the optical properties of a material by creating a structure that is finer than the wavelength of light.

• source Image Credit: Mackenzie Martin
• Phys.org – A NASA-powered solar sail can take science to new heights
• Dobel（2020） – Position control for sailing around the sun using fission solar sails
• doi.org/10.48550/arXiv.2206.10052 Theory of radiative stress on a refractive solar sail
• NASA – Refractive lights