This 2013 JPL presentation Solar System Escape Architecture for Revolutionary Science March 2013 Conference NIAC Phase 1: 2012-2013 by PI: Jeff Nosanov Co-Is: Dr. Daniel Grebow, Dr. Brian Trease, John West, Dr. Henry Garrett found in this comment shows a proposed solar sail craft capable of reaching the heliopause.
The trajectory includes a relatively close flyby of the Sun to maximize impulse from sunlight.
I noticed that the annotations for the image of the craft on page 20 show the "front" or Sun-facing side of the sail would be coated with aluminum for maximum reflectivity, and the back side would be coated with chromium for maximum emissivity.
- What is the importance of high emissivity in this application?
- Why would a shiny metal like chromium have a high emissivity value?