Space Tether

A Space Tether ( v. Engl space. , "Space" and tether, " leash ", " tether ", " fetter " ) is a long, strong rope, the spacecraft stick together in groups and a scientific proposal, the fuel-saving change in the orbit can be used by spacecraft, as well as for the production of electrical energy. In the 1970s and early 1980s presented Giuseppe Colombo, a professor at the University of Padua (Italy ), studies showing the possibilities of Space Tether.

For the production of high-strength materials are required, Dyneema is currently with the polyethylene fiber experiments, should future carbon nanotubes are used.

Colombo - orbit changes and electrical effects

A missile is on a constant orbit around a planet or a sun, so there is a balance between the gravitational (gravity) that pulls the missile in the direction of the center of mass of the object to which it revolves, and the centrifugal force, which by the circumnavigation formed on the orbit at a predetermined speed. Gravity takes the square of the distance between missile and ( center of the ) planet.

In extensive body now affects the so-called tidal power, because the force on the side facing the gravitational partner is stronger than that on the side facing away from the gravitational partner. If two missiles connected in different orbits by a tether, so they can be understood as extended object. The tidal power now provides a tension of the rope, because the missiles on the lower orbit a higher attractive force acts on the higher than in the.

There are two objects on orbits at different heights above a planet, the low flying body needs a higher speed than the higher flying to meet the balance between gravity and centrifugal force. If the two missiles now connected to a tether, so the rope is tensioned by this rate difference. Here, the originally faster partner is slowed and accelerated the originally slower partner, eventually both move through the connection with the same speed on orbits at different heights.

Does a space shuttle, the task of releasing a satellite, then it might be this abseil over a Space Tether. The satellite would thereby roped to a higher orbit than the one on which the orbiter is. Space shuttle and satellite moving on different orbits at the same speed, which, as described, the satellite of the higher web moved faster than necessary, the shuttle slowly. Would cut the connection in this state, the satellite would free-flying take a higher orbit because the authorization granted by the tether speed for the current track is too high. The Space Shuttle would be too slow for its orbit and would return to the planet.

Colombo suggested that having to tether electrical energy could be obtained: If an electrical conductor moving through a magnetic field is induced in this voltage. Thus could be a satellite, the long interprets Tethers to supply about it with energy. The benefit of this effect is impaired by the fact that the conductor in which the voltage is induced, even the earth's magnetic field produces an opposing field. This results in a deceleration of the entire system from spacecraft and Tether ( Lenz's Law ).

Accordingly, one could tether through which a large current flows, even on the situation or help train change of a satellite, as on a current- carrying conductor in a magnetic field, a force acts ( Lorentz force). Studies show that such electrical Tether (English electrodynamic tethers ) despite only slower track changes due to the fuel savings could be effective.

Research projects and experiments on the subject

The idea of ​​using to tether to connect the spacecraft reaches back to the original phase space. In 1966, the Gemini capsule was 11 coupled to the Agena rocket stage during manned Gemini program of NASA. The astronauts broke again the coupling and were only connected to a safety rope. They could produce a rotation of the coupled objects around the common center of gravity by controlling maneuvers, so that they actually (albeit imperceptibly ) manufactured artificial gravity. The experiment was repeated using Gemini 12.

In the years 1992 and 1996, NASA flew the shuttle missions STS -46 and STS -75, whose tasks will include the testing of the " Tethered Satellite System" ( TSS) was one of the Italian Space Agency (ASI ). The TSS was a 550 kg heavy spacecraft should be lowered to a 20 km long tether. The purpose of the experiment was to test the production of electricity. The attempt in 1992 failed, but in 1996 was the emergence of a voltage of 3500 volts are shown at current levels on Amp level. Although the mission ended with a technical failure of the insulation of the tether, but it was still a success: In addition to the detection of the electrical effect was now known that the electrical yield was twice as high as previously thought. Furthermore, the satellite was after disconnecting the tether into orbit, 140 km above the shuttle, transported, which represented the effect of the orbit change by Tether proof.

In September 2007, a Russian Foton -M3 - scientific satellites under the YES2 project ( Young Engineers Satellite ), which was almost exclusively carried out by students and young engineers, a 30 km long tether has been tested on board with the exposed on Tether Probe Fotino was brought to a re-entry trajectory.

On 23 January 2009, the Japanese Space Agency JAXA launched the Satellite Development Project of Kagawa University Kagawa developed Space Tethered Autonomous Robotic Satellite ( STARS ), to be tested with the use of Tethersystemen for future propulsion systems.