Tether injection of a satellite into a higher orbit
- Paper number
IAC-05-D4.3.09
- Author
Ms. Ana Blasco, European Space Agency (ESA)/ESTEC, The Netherlands
- Year
2005
- Abstract
Whip dynamics is one of these problems of physics that we take for granted. Different kinematic models have been proposed based on energy conservation: a wave runs down the cord and carries energy to the lash at the end. The moving part of the whip gets localized in an increasingly smaller section of the whip close to the tip. If energy is conserved, the velocity of this section must increase. If the whip/tether is tapered this effect should be further enhanced as the mass of the moving part decreases even faster. Conventional maneuvering in orbit implies that the working medium exhausted by thrusters as a reactive mass is lost forever. Tether-assisted maneuvers allow for a pure exchange of energy and angular momentum between tethered satellites and promises sizable savings in fuel. Whip dynamic provides a frame of reference for analyzing the end mass increase in speed while retrieval takes place. So, the goal of our work is to study whether it’s possible or not to use this effect in a controlled way, and to analyze if we really can be able to apply results to the satellite injection into a higher orbit from an orbiter through a tether momentum transfer maneuver including retrieval. Let consider a rotating tether system that consist of a massive tether and two masses (orbiter and satellite) attached to both tether ends. Supposing an initial state of out of orbital plane motion for the tether system, tether totally deployed and the mass center of the tether system following a circular Keplerian orbit. Then, retrieval process starts from the orbiter. During the retrieval process, the massive tether transfers energy and angular momentum from the system to the satellite, and so, satellite rotates progressively faster. This fact is studied to use, in a controlled way, the accumulated energy in the satellite for lifting it from a lower energy state to a higher one, (at expense of the tether system energy, which leads to boosting the satellite orbit apogee and lowering the orbiter orbit perigee). If we choose the optimum instant for satellite injection, great and perhaps amazing results could be achieved. But, how general could we take advantage of this whip effect? There are several limitations related to the process. For instance: in theory, by increasing tether length we could achieve as much satellite velocity as we desire, but not also in practice because of the tether material. The dependence of the tether mass on the velocity-ratio can result in a very large increase in tether mass for a given tip velocity. Hence, it’s critical to choose a material with as high characteristic velocity as possible. But, is material knowledge advanced enough to make tethers that could be able to resist the huge tip velocity that may be reached? Other possible complication is the well-known retrieval instability. Basically, it’s akin to the effect of speeding up a rotating body with decreasing its inertia. One of our goals is to determine if it’s possible to control this instability and the motion of the satellite. Also, the study of the characteristic time of the process (the time the process takes to reach the needed subsatellite velocity to reach the desired trajectory) should be considered to know what kind of missions it could be applied to. This whip effect will make possible even more ambitious space activities, offering us the chance of travelling towards deep space. Deep space exploration sounds like science fiction, but science fiction begins always where reality ends, and this reality is closer every time.
- Abstract document
- Manuscript document
IAC-05-D4.3.09.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.