A NASA NIAC study is developing the technology to get within 0.5 solar radii of the sun. The goal is to scatter 99.9% of the solar radiation. A solar radii is 700,000 kilometers. They want to get to 0 to 10,000 kilometers away from the surface of the sun.
In 2018 the Parker Solar Probe launched, planning to approach the Sun to within 8.5 solar radii of its surface. This is seven times closer than any previous mission, allowing first-time particle, radiation, and magnetic field measurements of the Sun’s corona.
Getting even closer to the Sun would grant further data to improve heliophysics models, while enabling study of the physics within the transition zone.
* they are grinding down materials to 200-300 nanometers so that the particles will reflect the infrared heat
* they switched from silver to tantalum and now to yttrium oxide
* they needed hydrophobic materials because water was limiting the solar radiation scattering to 99% efficient. This was still an improvement over current 94% efficient scattering.
* they have made 3-inch discs for testing and will move up to 1-meter diameter curved test articles.