Using a near-earth tether system for a flight to Mars

The possibility of using the tether system for a flight to Mars is considered. The tether system is located on a near-Earth orbital station. The paper compares two options for launching a spacecraft to Mars in terms of fuel costs. The first is a launch from a reference orbit two hundred kilometers high. The second is a preliminary flight from the reference orbit to the space station and a further launch from the upper platform after the deployment of the tether system. Next the spacecraft using its engines makes the transition to the elliptical orbit of the Homan flight to Mars. After separation of the spacecraft, the tether system is folded. The main mass of the orbital station is located on the lower platform of the tether system. The mass of the upper platform, with the spacecraft docked to it for the flight to Mars, is no more than 10 percent of the mass of the lower platform. As a result, the center of gravity of the tether system will be located near the lower platform. After the spacecraft is separated from the upper platform, the position of the center of gravity of the tether system will shift. To transfer the rolled-up tether system to the initial circular orbit, additional fuel costs will be required. It is assumed that when the tether system is opened, the position of its center of gravity in the radial direction does not change, and all the orbits are in the same plane. The tether is oriented in a radial direction with relative to the Earth, and all points of the tether have the same angular velocity. The cross-sectional area of the tether is constant. Analytical relations are obtained. They allow us to estimate the mass of the tether and the fuel economy when using the tether system, taking into account the additional fuel costs for restoring the orbit of its center of gravity after the separation of the Martian spacecraft. The results of calculations of the main parameters of the tether made of real materials are presented.