Based on estimates of the density of dust in the local interstellar medium, over the course of a journey to Alpha Centauri each square centimeter of the frontal cross-sectional area of the StarChip and lightsail would encounter about 1,000 impacts from dust particles of size 0.1 micron and larger. However, there is only a 10% probability of a collision with a 1 micron particle, and a negligible probability of impact with much larger particles.

A 0.1 micron dust particle moving at 20% of the speed of light would penetrate and melt the StarChip to a depth of order 0.4mm. To estimate scale effects, calculations were made assuming a 10cm X 0.1mm thickness. Traveling with the nanocraft’s edge facing parallel to the velocity vector would reduce the cross section to 0.1cm2, for a 10 cm StarChip with a 0.1mm thickness. A protective coating of beryllium copper could be added to the leading edge of the StarChip, as a sacrificial layer for additional protection from dust impacts and erosion. If needed, the StarChip geometry could be elongated (‘needle’ geometry), to further minimize the cross-section.

To mitigate the impact of dust further the sail could potentially be folded into a streamlined configuration during the cruising phase to Alpha Centauri. This would minimize the frontal area of the sail. The nanocraft’s electronics could also be designed so as to be less vulnerable to localized damage from dust.

The momentum kick from 0.1 micron dust particles is small, and its effect on the nanocraft’s trajectory might be compensated for by photon thrusters.

Research:

• E. Grün et al., “Interstellar dust in the heliosphere.” Astron. Astrophysics, Vol. 286, pp. 915-924 (1994)
• Draine, B. T. “Physics of the Interstellar and Intergalactic Medium,” Princeton University Press (2011)