Antonio Sanchez-Torres

A Proposed Two-Stage Two-Tether Scientific Mission at Jupiter

A two-stage mission to place a spacecraft (SC) below the Jovian radiation belts, using a spinning bare tether with plasma contactors at both ends to provide propulsion and power, is proposed. Capture by Lorentz drag on the tether, at the periapsis of a barely hyperbolic equatorial orbit, is followed by a sequence of orbits at near-constant periapsis, drag finally bringing the SC down to a circular orbit below the halo ring. Although increasing both tether heating and bowing, retrograde motion can substantially reduce accumulated dose as compared with prograde motion, at equal tether-to-SC mass ratio. In the second stage, the tether is cut to a segment one order of magnitude smaller, with a single plasma contactor, making the SC to slowly spiral inward over several months while generating large onboard power, which would allow multiple scientific applications, including in situ study of Jovian grains, auroral sounding of upper atmosphere, and space- and time-resolved observations of surface and subsurface.

Electrostatic Tether Application for Scattering of Relativistic Particles in the Earth’s Radiation Belts

An electrostatic tether could be a recent technology application for removing energetic particles in the earths radiation belts. Both hollow cathode and high-voltage source will keep the conductive tether at high positive/negative bias. An effective Coulomb deflection of the particles into the loss cone will produce a high rate of atmospheric penetration, decreasing the amount of high-energy particles in the radiation belts. This paper focuses on the high positive-bias case with a sheath that is correctly modeled. For small radius and extremely high bias, the tether does collect the relativistic orbital motion limited current. Relativistic effects modify both potential and density profiles, decreasing the range of the sheath and, in turn, increasing tether current collection. The remediation time will increase if relativistic effects are considered. A remediation time of about six years is determined for 100 1-MV tethers moving in a circular equatorial orbit at an altitude of about 2000 km. In addition, the presence of both Coulomb and Lorentz forces may induce thrust or drag on the tether. Both forces are briefly studied with plasma condition characteristic of the inner radiation belt.

Propulsive Force in an Electric Solar Sail for Outer Planet Missions

An electric solar sail (E-sail) is a recent propellantless propulsion concept for a direct exploration of the solar system. An E-sail consists of an array of bare, conductive tethers at very high positive/negative bias, prone to extract solar-wind momentum by Coulomb deflection of protons. This paper focuses on the positive-bias case with a thick sheath that must be correctly modeled. Ion scattering within the sheath and the resulting thrust are determined. Use of E-sail for outer planet missions would reduce the time of flight; a 2-ton spacecraft might reach Jupiter in less than two years.

Analysis of Tether-Mission Concept for Multiple Flybys of Moon Europa

All four giant planets, far from the Earth and sun and having deep gravitational wells, present propulsion and power mission issues, but they also have an ambient plasma and magnetic field that allows for a common mission concept. Electrodynamic tethers can provide propellantless drag for planetary capture and operation down the gravitational well, and they can generate power to use along with or be stored for inverting tether current. The design for an alternative to NASA’s proposed Europa mission is presented here. The operation requires the spacecraft to pass repeatedly near Jupiter, for greater plasma density and magnetic field, raising a radiation-dose issue that past analyses did take into account; tape tethers tens of kilometers long and tens of micrometers thick, for greater operation efficiency, are considered. This might result, however, in attracted electrons reaching the tape with a penetration range that exceeds tape thickness, thereby escaping collection. The mission design requires keeping ...