Arxiv - EMMI – Electric Solar Wind Sail Facilitated Manned Mars Initiative
Abstract
The novel propellantless electric solar wind sail concept promises efficient low thrust transportation in the Solar System outside Earth’s magnetosphere. Combined with asteroid mining to provide water and synthetic cryogenic rocket fuel in orbits of Earth and Mars, possibilities for affordable continuous manned presence on Mars open up. Orbital fuel and water enable reusable bidirectional Earth-Mars vehicles for continuous manned presence on Mars and allow smaller fuel fraction of spacecraft than what is achievable by traditional means. Water can also be used as radiation shielding of the manned compartment, thus reducing the launch mass further. In addition, the presence of fuel in the orbit of Mars provides the option for an all-propulsive landing, thus potentially eliminating issues of heavy heat shields and augmenting the capability of pinpoint landing. With this E-sail enabled scheme, the recurrent cost of continuous bidirectional traffic between Earth and Mars might ultimately approach the recurrent cost of running the International Space Station, ISS.
The electric solar wind sail (E-sail) provides thrust in the solar wind without consuming fuel. The E-sail uses charged tethers to extract momentum from the solar wind ions (mainly protons) by electrostatic Coulomb interaction with the plasma flow to produce thrust. According to current estimates, the E-sail is 2-3 orders of magnitude more efficient than traditional propulsion methods (chemical rockets and ion engines) in terms of produced lifetime-integrated impulse per propulsion system mass, if the mission duration is 10 years and the mission does not proceed too far into the outer solar system. This is based on numerical simulations. When these simulations are run for plasma representing LEO conditions, their predicted electron sheath width (which is a proxy for E-sail thrust per length) is in good agreement with laboratory measurements of the sheath width in LEOlike conditions.
To enable maneuvering and trajectory control, the E-sail thrust can be vectored in a cone of ∼ 30◦ around the solar wind velocity vector. It is possible to adjust the magnitude of the thrust between 0-100 % by modifying the current and voltage of the electron gun. Turning E-sail propulsion off is possible at any time by turning off the electron gun. A strategy of maximizing available thrust by matching the electron gun current with the current gathered by the tethers leads by certain natural negative feedback mechanisms to a situation where the thrust varies much less than the solar wind dynamic pressure. Even with simple trajectory control law, the maneuverability of the E-sail is sufficient to allow navigation to, for example, Mars.
A large E-sail, that can provide 1 N of thrust at 1 au from Sun, can travel from the Earth to the asteroid belt in a year, and bring back three tonnes of water in three years. One E-sail based spacecraft is capable of repeating the journey multiple times within its estimated lifetime of at least ten years.
The E-sail has been tested in space with the EST-Cube1 cubesat
There was a presentation on the status of Esail work late in 2014
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Reposted via Next Big Future
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