Astronomy and Astrophysics, volume 641A, 45-45 (2020/9-1)
Low-cost precursor of an interstellar mission.
HELLER R., ANGLADA-ESCUDE G., HIPPKE M. and KERVELLA P.
Abstract (from CDS):
The solar photon pressure provides a viable source of thrust for spacecraft in the solar system. Theoretically it could also enable interstellar missions, but an extremely small mass per cross section area is required to overcome the solar gravity. We identify aerographite, a synthetic carbon-based foam with a density of 0.18kg/m3 (15000 times more lightweight than aluminum) as a versatile material for highly efficient propulsion with sunlight. A hollow aerographite sphere with a shell thickness εshl=1mm could go interstellar upon submission to solar radiation in interplanetary space. Upon launch at 1AU from the Sun, an aerographite shell with εshl=0.5mm arrives at the orbit of Mars in 60d and at Pluto's orbit in 4.3yr. Release of an aerographite hollow sphere, whose shell is 1µm thick, at 0.04AU (the closest approach of the Parker Solar Probe) results in an escape speed of nearly 6900km/s and 185 yr of travel to the distance of our nearest star, Proxima Centauri. The infrared signature of a meter-sized aerographite sail could be observed with JWST up to 2AU from the Sun, beyond the orbit of Mars. An aerographite hollow sphere, whose shell is 100µm thick, of 1m (5m) radius weighs 230mg (5.7g) and has a 2.2g (55g) mass margin to allow interstellar escape. The payload margin is ten times the mass of the spacecraft, whereas the payload on chemical interstellar rockets is typically a thousandth of the weight of the rocket. Using 1g (10g) of this margin (e.g., for miniature communication technology with Earth), it would reach the orbit of Pluto 4.7yr (2.8yr) after interplanetary launch at 1AU. Simplistic communication would enable studies of the interplanetary medium and a search for the suspected Planet Nine, and would serve as a precursor mission to α Centauri. We estimate prototype developments costs of 1 million USD, a price of 1000 USD per sail, and a total of <10 million USD including launch for a piggyback concept with an interplanetary mission.