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Electric sail performance analysis

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This is a summary of our paper "Electric sail performance analysis" by G. Mengali, A. Quarta and P. Janhunen, Journal of Spacecraft and Rockets, in press, 2007.

Because of copyright restrictions, we cannot put the whole paper on
the web. Here is thus only the abstract and the figures. Electronic
PDF reprints can be asked from Pekka Janhunen, firstname.lastname@fmi.fi.
*Abstract:*
An electric sail uses the solar wind dynamic pressure to produce a
small, but continuous thrust by interacting with an electric field
generated around a number of charged tethers (the electric sail). Due
to the weakness of the solar wind dynamic pressure, quantifiable in
about 2 nPa at Earth's distance from the Sun, the required tether
length is \pekka{of} the order of some kilometers. Equipping a 100 kg
spacecraft with one hundred of such tethers, each one being of 10 km
length, is sufficient to obtain a spacecraft acceleration of about 1
mm/s^2. These values render the electric sail a potentially
competitive propulsion means for future mission applications. The aim
of this paper is to provide a preliminary analysis of the electric
sail performance and to investigate the capabilities of this
propulsion system in performing interplanetary missions. To this end
the minimum time rendezvous transfer problem between circular and
coplanar orbits is considered and the optimal steering law is found
using an indirect approach. The main differences between electric sail
and solar sail performance are also emphasized.

Figure 1: Conceptual sketch of an electric sail.

Figure 2a: Propulsive force as function of Sun distance: Dimensionless propulsive force.

Figure 2a: Accuracy of the simplified model, see Eq. (4).

Figure 3: Dimensionless propulsive acceleration at 1 AU (see Eq. (10)).

Figure 4: Optimal tether voltage.

Figure 5: Optimal dimensionless propulsive acceleration (see Eq. (12)).

Figure 6: Total tether length (rw=10 um).

Figure 7: Reference frame and thrust angle.

Figure 8a: Minimum time circle-to-circle rendezvous: Earth-Mars transfer

Figure 8b: Minimum time circle-to-circle rendezvous: Earth-Venus transfer

Figure 9a: Earth-Mars circle-to-circle rendezvous with aEarth=0.5 mm/s^2 and alpha_max=20 deg: time histories of distance and velocity
Figure 9b: Earth-Mars circle-to-circle rendezvous with aEarth=0.5 mm/s^2 and alpha_max=20 deg: acceleration components

Figure 10: Optimal trajectory for an Earth-Mars transfer using an electric sail.

Figure 11: Sail angular rate for an Earth-Mars circle-to-circle transfer.

Figure 12: Minimum time Earth-Mars transfer as a function of aEarth.

Minimum transfer times for an electric sail (aEarth = 0.5 mm/s^2 and alpha_max=30 deg) and a solar sail.