  Spacecraft kinematics, peak perihelion temperature and space environment
effects during solar-radiation-pressure acceleration for a beryllium
hollow-body interstellar solar sail inflated with hydrogen fill gas are
investigated. We demonstrate that diffusion is alleviated by an on-board fill
gas reserve and electrostatic pressure can be alleviated by increasing
perihelion distance. For a 0.1 AU perihelion, a 937 m radius sail with a sail
mass of 150 kg and a payload mass of 150 kg, perihelion sail temperature is
about 1000 K, peak acceleration is about 0.6 g, and solar-system exit velocity
is about 400 km/s. After sail deployments, the craft reaches the 200 AU
heliopause in 2.5 years, the Sun's inner gravitational focus at 550 AU in about
6.5 years and 2,550 AU in 30 years. The Be hollow-body sail could be applied in
the post 2040 time frame to verify general relativity predictions regarding the
Sun's inner gravitational focus and to explore particles and fields in the
Sun's inner Oort Comet Cloud.
