412 research outputs found
Combining Magnetic and Electric Sails for Interstellar Deceleration
The main benefit of an interstellar mission is to carry out in-situ
measurements within a target star system. To allow for extended in-situ
measurements, the spacecraft needs to be decelerated. One of the currently most
promising technologies for deceleration is the magnetic sail which uses the
deflection of interstellar matter via a magnetic field to decelerate the
spacecraft. However, while the magnetic sail is very efficient at high
velocities, its performance decreases with lower speeds. This leads to
deceleration durations of several decades depending on the spacecraft mass.
Within the context of Project Dragonfly, initiated by the Initiative of
Interstellar Studies (i4is), this paper proposes a novel concept for
decelerating a spacecraft on an interstellar mission by combining a magnetic
sail with an electric sail. Combining the sails compensates for each
technologys shortcomings: A magnetic sail is more effective at higher
velocities than the electric sail and vice versa. It is demonstrated that using
both sails sequentially outperforms using only the magnetic or electric sail
for various mission scenarios and velocity ranges, at a constant total
spacecraft mass. For example, for decelerating from 5% c, to interplanetary
velocities, a spacecraft with both sails needs about 29 years, whereas the
electric sail alone would take 35 years and the magnetic sail about 40 years
with a total spacecraft mass of 8250 kg. Furthermore, it is assessed how the
combined deceleration system affects the optimal overall mission architecture
for different spacecraft masses and cruising speeds. Future work would
investigate how operating both systems in parallel instead of sequentially
would affect its performance. Moreover, uncertainties in the density of
interstellar matter and sail properties need to be explored
Chasing Nomadic Worlds: A New Class of Deep Space Missions
Nomadic worlds, i.e., objects not gravitationally bound to any star(s), are
of great interest to planetary science and astrobiology. They have garnered
attention recently due to constraints derived from microlensing surveys and the
recent discovery of interstellar planetesimals. In this paper, we roughly
estimate the prevalence of nomadic worlds with radii of . The cumulative number density
appears to follow a heuristic power law given by . Therefore, smaller objects are probably much more numerous
than larger rocky nomadic planets, and statistically more likely to have
members relatively close to the inner Solar system. Our results suggest that
tens to hundreds of planet-sized nomadic worlds might populate the spherical
volume centered on Earth and circumscribed by Proxima Centauri, and may thus
comprise closer interstellar targets than any planets bound to stars. For the
first time, we systematically analyze the feasibility of exploring these
unbounded objects via deep space missions. We investigate what near-future
propulsion systems could allow us to reach nomadic worlds of radius in a
-year flight timescale. Objects with km are within the purview
of multiple propulsion methods such as electric sails, laser electric
propulsion, and solar sails. In contrast, nomadic worlds with
km are accessible by laser sails (and perhaps nuclear fusion), thereby
underscoring their vast potential for deep space exploration.Comment: 22 pages including "Highlights" page; accepted by Acta Astronautic
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