The concept goes back to Joerg Strobl, who first published it in a 1989 paper for the Journal of the British Interplanetary Society. And it’s a design that seems to scale well if properly deployed. The team studied two configurations, one a generation ship with inflated sail radius of 541.5 kilometers, a payload of 107 kg, and a separation between the sail faces of one kilometer. A second is a near-term extrasolar probe with sail radius of 937 meters, a 30 kg payload and a 1.8 meter separation. The numbers show how well the concept adjusts to different missions:
From the point of view of kinematics, mechanical stress, and thermal effects, the hollow-body solar photon sail scales well. Both conﬁgurations had a spacecraft areal mass density of 6.52 × 10−5 kg/m2, a peak internal gas pressure of 1.98 × 10−4 Pa, and a peak perihelion temperature of 1412 K. If fully inﬂated at the 0.05 AU perihelion of an initially parabolic solar orbit, both had a peak radiation-pressure acceleration of 36.4 m/s2 and exited the solar system at 0.00264c after an acceleration duration less than one day.
The new paper looks hard at the issues these designs face, including problems with the proposed 0.05 AU close pass by the Sun and the effects of solar radiation on sail materials and the hydrogen fill gas. The result is a modification of the near-term concept discussed above, with perihelion adjusted to 0.1 AU.
The tensile strength of beryllium degrades with temperature, the sail could burst from electrostatic pressure at the earlier 0.05 AU perihelion. Increasing the perihelion distance lowers the electrostatic pressure dramatically and makes the mission feasible.
There is a lot of coverage of the first directly imaged extrasolar planets.
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
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