Solar Surfing with coating that will reflect up to 99.9 % of solar radiance
This will be accomplished by leveraging off of their low temperature coating, currently being developed under NIAC funding. They will modify the existing models to determine an optimal high temperature solar reflector, predict its performance, and construct a prototype version of this coating. This prototype will be sent to their partner at the Johns Hopkins Applied Physics Laboratory where it will be tested in an 11 times solar simulator. The results of this modeling/testing will be used to design a mission to the Sun, where they hope to come to within one solar radius of the Sun's surface, 8 times closer than the closest distance planned for the upcoming Solar Probe Plus. This project will substantially advance the current capabilities of solar thermal protection systems, not only potentially allowing "Solar Surfing", but allowing better thermal control of a future mission to Mercury.
A very close flyby of the sun with a spacecraft that could deploy an ultrathin solar sail would allow for higher final speeds. It would also allow for deceleration at a target star from higher speeds. Getting with 5 solar radii would allow for speeds 13% of the speed of light.
This is from a 1999 NASA NIAC paper that discussed ultrathin solar sails and close flyby of the sun.
Acceleration and the distance of closest solar approach are the key variables that determine if a solar sail can reach velocities of interest for interstellar travel. Usually, the characteristic acceleration, ac, i.e., the sail self acceleration at 1 AU (the Earth's orbit), is a good means of comparing one sail design to another. If solar pressure force is integrated from closest solar approach to infinity, which is the kinetic energy (mv2) gained by the sail, the terminal velocity of a solar sail will be given by:
