2009, Articolo in rivista, ENG
Pardini C.; Hanada T.; Krisko P. H.
By using electrodynamic drag to greatly increase the orbital decay rate, an electrodynamic space tether can remove spent or dysfunctional spacecraft from low Earth orbit (LEO) rapidly and safely. Moreover, the low mass requirements of such tether devices make them highly advantageous compared to conventional rocket-based de-orbit systems. However, a tether system is much more vulnerable to space debris impacts than a typical spacecraft and its design must be proved to be safe up to a certain confidence level before being adopted for potential applications. To assess space debris related concerns, in March 2001 a new task (Action Item 19.1) on the "Potential Benefits and Risks of Using Electrodynamic Tethers for End-of-life De-orbit of LEO Spacecraft" was defined by the Inter-Agency Space Debris Coordination Committee (IADC). Two tests were proposed to compute the fatal impact rate of meteoroids and orbital debris on space tethers in circular orbits, at different altitudes and inclinations, as a function of the tether diameter to assess the survival probability of an electrodynamic tether system during typical de-orbiting missions. IADC members from three agencies, the Italian Space Agency (ASI), the Japan Aerospace Exploration Agency (JAXA) and the US National Aeronautics and Space Administration (NASA), participated in the study and different computational approaches were specifically developed within the framework of the IADC task. This paper summarizes the content of the IADC AI 19.1 Final Report. In particular, it introduces the potential benefits and risks of using tethers in space, it describes the assumptions made in the study plan, it compares and discusses the results obtained by ASI, JAXA and NASA for the two tests proposed. Some general conclusions and recommendations are finally extrapolated from this massive and intensive piece of research.
2007, Articolo in rivista, ENG
Pardini C.; Hanada T.; Krisko P. H.; Anselmo L.; Hirayama H.
Over 9000 satellites and other trackable objects are currently in orbit around the Earth, along with many smaller particles. As the low Earth orbit is not a limitless resource, some sort of debris mitigation measures are needed to solve the problem of unusable satellites and spent upper stages. De-orbiting devices based on the use of conducting tethers have been recently proposed as innovative solutions to mitigate the growth of orbital debris. However, electrodynamic tethers introduce unusual problems when viewed from the space debris perspective. In particular, because of their small diameter, tethers of normal design may have a high probability of being severed by impacts with relatively small meteoroids and orbital debris. This paper compares the results obtained at ISTI/CNR, the Kyushu University and NASA/JSC concerning the vulnerability to debris impacts on a specific conducting tether able to de-orbit spacecraft in inclinations up to 75◦ and initial altitude less than 1400 km. A double line tether design has been analyzed, in addition to the single wire solution, in order to reduce the tether vulnerability. The results confirm that the survivability concern is fully justified for a single line tether and no de-orbit mission, from the altitudes and inclinations considered, is possible if the tether diameter is smaller than a few millimeters. The survival probability is shown to grow for a double line configuration with a sufficiently high number of knots and loops. The results are strongly dependent on the environment model adopted and the MASTER-2001 orbital debris and meteoroids fluxes result in survival probabilities appreciably higher than those of ORDEM2000 coupled with the Grün meteoroids model.
2003, Presentazione, ENG
Pardini C.
De-orbiting devices based on the use of conducting tethers have been recently proposed as innovative solutions to remove satellites and upper stages from low earth orbit when they have completed their missions. Studies of such devices are currently being planned, or are in the early development phase, in the US and Europe. A flight experiment to validate the performance of the bare electrodynamic tether in space and demonstrate its capability to produce thrust is planned by NASA in the first half of 2003. The main objective of this presentation will be to show the various electrodynamic tether systems recently proposed to de-orbit LEO spacecraft, and to emphasize their performances in terms of the orbital decay times.
2003, Presentazione, ENG
Pardini C.
By using electrodynamic drag to greatly increase the orbital decay rate, an electrodynamic space tether can remove spent or dysfunctional spacecraft from LEO rapidly and safely. Moreover, the low mass requirements of such tether devices make them highly advantageous compared to conventional rocket-based de-orbit systems. However, a tether shall be designed to assure its correct deployment and dynamical stability against the perturbing electrodynamic torque as well. In addition, a tether system is much more vulnerable to space debris impacts than a typical spacecraft and its design must prove to be safe to a certain confidence level before being adopted for a wise range of promising applications. Therefore, the aim of this presentation will be to assess and show the main potential advantages, difficulties and risks related to the use of electrodynamic tether to de-orbit spacecraft.