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The ElectroDynamic Delivery Express (EDDE) is an autonomous space vehicle that can deliver multiple small satellites from any low earth orbit (LEO) to any other desired low earth orbit within months, without using fuel. EDDE uses solar power to drive multiampere currents through a multi-kilometer aluminum tape. The tape sees a force normal to both...
Contexts in source publication
Context 1
... has units of N·s/kg. Table 1 on the next page compares EDDE with other electric propulsion systems, using our best estimates of key parameters. ...
Context 2
... the first few captures (or maybe even a few dozen!) might best be done with satellite-sized orbital debris, to test the concept without risking even a failed satellite. 500 200 2000 13 800 1 6K SPT-100 72 25 78 17 1600 8 12K DS-1 Ion 82 253 92 27 3100 14 7K 10 kW Hall 400 250 450 22 3000 13 18K Test-EDDE 4 21 20 50 - 24 19K EDDE 15 85 500 20 - 60 295K EDDE thrust is for typical orbit changes; all run times are calendar months, sun-only operation. ...
Context 3
... we need only one mounting surface on the payload rather than two. Table 2. Mass Budget for 36 kg Test Version of EDDE Component Description Mass, kg Conductor/collector 2 X 400 m Al foil w/quartz & cores 3.4 Solar array & end rails 1 kW thin film or 500 W crystalline 3 Power handling Batteries & power control 1 Avionics Computer, GPS, telemetry, etc. 1 Hollow cathode emitter Assumed mass, with gas for 1 year 10 EDDE structure & PAF 1 kg PAF + 12% of other EDDE 4.9 Structure on Delta Marman clamp, supports, misc. 3 Non-conducting tether 4 km flat Spectra braid + deployer 2 EDDE payloads Satellites, diagnostic sensors, etc. 8 Total Max Delta/GPS secondary payload 36.3 ...
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Citations
... The feedback control algorithms have been developed. An assessment was made of the dynamics of the system, tether tension, accelerations, etc. [118][119][120][121][122]. ...
... The diagram (Fig. 18) shows different variants of the system. The first one has 36 kg, and can be launched by the Delta launch vehicle [121]. ...
... However, at the altitudes above 600-1200 km (depending on the eleven-year cycle of solar activity), the low plasma density limits the collection of electrons and, consequently, the thrust of the system [121]. The use of EDDE in GEO seems to be problematic due to the extremely low strength of the Earth's magnetic field at such altitudes, and the need in the propellant consumption to generate plasma when the electrical circuit is closed outside the Earth's ionosphere. ...
The term “space debris” refers to spacecraft not removed from orbit at the end of their service life, upper stages in the geostationary orbit region, as well as to the fragments of spacecraft and upper stages formed as a result of deliberate or accidental collision of spacecraft and upper stages with each other or with natural space debris.
The problem of removing space debris from outer space is a global problem. Many countries are realizing projects on space debris cataloging, various technical means are being studied for space debris removal into graveyard orbits with parameters agreed upon by the international community. Various countries conducting space exploration have adopted special standards and guidelines for preventing the space debris formation [1,2,3,4].
The report [5] emphasizes that contamination of the near-Earth space is growing steadily. The probability of spacecraft collisions with each other is significantly increasing. This can lead to the functioning spacecraft characteristics degradation and even to complete loss of performance.
The article presents a brief overview of the methods and techniques that can be used to space debris removal into disposal orbits using flexible or virtual connection between space debris and service spacecraft.
... The use of electrodynamic tethers (EDT) to de-orbit satellites from Low Earth Orbit (LEO) has been studied for more than a decade12345678 . This technique could be particularly useful for defunct satellite removal as well as post mission disposal of end-of-life spacecraft from crowded orbital regions, thus reducing the chances of Kessler Cascading [9]. ...
Electrodynamic tethers (EDT) represent one of the possible means to de-orbit defunct satellites from Low-Earth-Orbit at end-of-life. However, considering the large area exposed to the space environment and the consequent high number of debris impacts per unit time, a high tether survivability to orbital debris is of primary importance. This paper provides an estimation of the number of fatal impacts per unit time and per unit length on a tape tether, using for the first time an experimental ballistic limit equation that was derived for tapes and accounts for the effects of both the impact velocity and impact angle. It has recently been shown that, tape tethers, as opposite to round wires, are more resistant to space debris impacts. It is shown that considering a tape tether with cross section , the number of critical events due to impact with non-trackable debris is always less than 0.01/yr/km, being maximum for orbit inclination of .
... Orbit manoeuver or power generation systems (Gallagher et al., 1998) are among other versatile modes that tethers are capable of working, apart from orbit decay. For more than a decade till now different studies have been carried out on various tether configurations and de-orbiting performance (Forward et al., 1998;Vannaroni et al., 1999;van der Heide and Kruijff, 2001;Gilchrist et al., 2002;Nishimine, 2002;Pearson et al., 2003;Sanmartín et al., 2010), providing a propellantless, cost-effective solution to deorbiting dead satellites as well as future satellites after their desired work-life. The bare tether concept, which has the tether bare 3.3. ...
... An EDT works on the basis of the interaction between the electric current flowing along the tether and the geomagnetic field, which produces a Lorentz drag force, the current being itself induced by the tether motion relative to the Earth's magnetized ionosphere; this reflects on the thermodynamic character of that interaction, always leading like air-drag, to a decrease in the relative motion of tether and ambient plasma. For more than a decade till now different studies have been carried out on various tether configurations and deorbiting performance (Forward et al., 1998; Vannaroni et al., 1999; Van der Heide and Kruijff, 2001; Ahedo and Sanmartin, 2002; Gilchrist et al., 2002; Nishimine, 2002; Pearson et al., 2003 ), providing a propellantless , cost-effective solution to deorbiting dead satellites as well as future satellites after their desired work-life. The bare tether concept, which has the tether bare of insulation, collecting electrons itself, has eliminated the need for a plasma contactor at the anodic end (Sanmartin et al., 1992; Sanmartin et al., 1993). ...
The low earth orbit (LEO) environment contains a large number of artificial debris, of which a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Deorbiting defunct satellites at the end of their life can be achieved by a successful operation of an Electrodynamic Tether (EDT) system. The effectiveness of an EDT greatly depends on the survivability of the tether, which can become debris itself if cut by debris particles; a tether can be completely cut by debris having some minimal diameter. The objective of this paper is to develop an accurate model using power laws for debris-size ranges, in both ORDEM2000 and MASTER2009 debris flux models, to calculate tape tether survivability. The analytical model, which depends on tape dimensions (width, thickness) and orbital parameters (inclinations, altitudes) is then verified with fully numerical results to compare for different orbit inclinations, altitudes and tape width for both ORDEM2000 and MASTER2009 flux data.
... The tether as a de-orbiting device will be ultimately destroyed at re-entry. Although very few in-situ experiments have been carried out till now, studies have been done for more than a decade on the deorbiting performances and various tether configurations [4][5][6][7][8][9][10]. A tether can be damaged or cut due to mishandling during deployment from spacecraft, manufacturing defects, or material degradations. ...
The current space environment, consisting of a huge population of
man-made debris in addition to natural micrometeoroids, pose a serious
risk to safe operations in space, and the situation is continuously
deteriorating due to in-orbit debris collisions and to new satellite
launches. Bare electrodynamic tethers can provide an efficient mechanism
for rapid de-orbiting of satellites from Low Earth Orbit at end of life.
A tether, however, might itself be victim of fatal damage by orbital
debris. First, due to its particular geometry (length very much larger
than cross-section dimensions), a tether may have a relatively high risk
of getting severed by the single impact of small debris. A comparison is
made of survivability against debris impacts of round-wire and thin-tape
tethers of equal length and mass. NASA's ORDEM 2000 flux model, which
shows debris flux one order of magnitude higher than ESA's MASTER 2005
model at the range of debris-size of interest, and allows for a simple
analytical approximation, is used. The analysis shows that a tape-tether
will have probability of survival about one to one-and-half orders of
magnitudes higher than the corresponding round-wire tether. Results are
then confirmed by numerical evaluation using both ORDEM and MASTER flux
models. Secondly, due to the low cross-section depth, multiple close-by
impacts by abundant very small debris might result in critical
deterioration of tether material. This is analysed using NASA's GRUN
micrometeoroid model. Results show that effects accumulated over times
much longer than estimated times for de-orbiting are entirely
negligible.
... Despite a small number of full-scale experiments carried out so far using space tethers [1], the possibility of de-orbiting spacecraft by means of electrodynamic tethers has been on the drawing board of theorists for almost a decade. Various conducting tether configurations have been studied and their de-orbiting performances have been extensively assessed by several authors [2][3][4][5][6][7][8][9][10][11][12]. ...
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.
... Despite a small number of full-scale experiments made so far using space tethers [9], the possibility of de-orbiting spacecraft by means of electrodynamic tethers has been on the drawing board of theorists for almost a decade. Apart from the Terminator Tether solution, various conducting tether configurations have been studied and their de-orbiting performances have been extensively assessed by several authors [10][11][12][13][14][15][16][17]. ...
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.
... 4 The system design described in these limited-distribution documents is given in a published paper. 5 Spinning not only allows the tether to be driven much harder than conventional ED tethers can be driven without going unstable, but the constantly varying tether and magnetic field line orientations allow the tether to better "tack" against the magnetic field. This allows relatively efficient change of any desired combination of orbit elements, in any orbit inclination. ...
Electrodynamic tethers produce low thrust through interaction of the electric current in the tether with the Earth's magnetic field. The thrust is comparable with that of ion rockets and Hall thrusters, and they have the added advantage that they are propellantless, allowing them to produce an order of magnitude greater velocity changes than ion rockets. However, the long conductors of such electrodynamic thrusters typically exhibit unstable behaviors with higher currents. Instability affects both libration and bending modes of tether motion and significantly limits the performance characteristics of electrodynamic tether thrusters. Previous concepts for electrodynamic tethers have proposed stabilizing them by hanging vertically under the gravity gradient, but this passive gravity-gradient stabilization severely limits the current in the conductor, and therefore limits the thrust. Two methods have been developed to stabilize electrodynamic tethers and improve their performance. First, the system spins with an average spin rate significantly higher than the orbital rate, increasing tether tension for a more robust and controllable tether system, and providing a better orientation of the tether with respect to the magnetic field for orbital maneuvering. Second, electric current variation is used to control both the tether spin parameters and the tether bending modes. It is shown that a controlled, spinning electrodynamic tether can consistently deliver a much higher thrust compared with the traditional hanging tether configuration. Minimum-time orbit transfers with spinning tethers can be described approximately by a set of relatively simple ordinary differential equations using Pontryagin's Principle. These techniques were developed to control the dynamics of the Spinning Electrodynamic Tether (SET) system. This uses a conductor two to ten kilometers long as an electrodynamic thruster for a low-thrust orbit transfer vehicle.
Artificial satellites and launch vehicles have created an ever growing number and variety of orbiting debris objects ranging in size from a few microns to several meters. The urgency of the situation has been exacerbated by the 2007 Chinese anti-satellite test and the 2009 collision of Iridium and Cosmos satellites. Sometime in the next one or two decades a space debris reduction program may be needed to assure continued access to, and use of, space for applications and exploration. Debris removal techniques and programs have been suggested, but none have been implemented. A recently completed investigation of engineering issues associated with the in situ capture of space debris objects spans the spectrum of options for all categories of these derelicts. This work concludes that not all debris can, or should, be removed. Technologies and systems for capturing very small debris do not exist. Only the largest of the objects can be effectively addressed with current technology. However, there remain several complications even for these derelicts. For example, every large debris piece may possess residual angular momentum with associated angular rates that could exceed 30 rpm. These objects are uncooperative and may have to be approached in such a way that angular momentum can be safely removed. Once stabilized, such objects may have to be grappled in order to control them. Then, a device may have to be attached in order to either apply proper removal forces or to store the object for later disposal. This paper attempts to identify and assess technologies and systems associated with in situ capture and control. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.
