ElectroDynamic Delivery Express (EDDE) In-Space Demonstrator

Pearson, J.; Carroll, Joseph A.; Levin, E.; Oldson, John; Hausgen, Paul E.

doi:10.2514/6.2003-4790

Cited by 16 publications

(3 citation statements)

References 9 publications

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“…Under an Air Force SBIR contract 1 , we designed a spacecraft called the ElectroDynamic Delivery Express (EDDE) that can maneuver throughout low Earth orbit by controlling the current in its conducting tether 2 . By switching the current as a function of orbital position and spin plane and phase, the EDDE spacecraft can adjust its spin state and all 6 elements of its orbit: altitude, inclination, node, eccentricity, line of apsides, and epoch.…”

Section: Electrodynamic Loop and Forcementioning

confidence: 99%

High Voltage Power Switching for a Conducting Tether

Harkare¹,

Dougal²,

Carroll³

et al. 2004

2nd International Energy Conversion Engineering Conference

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The ElectroDynamic Delivery Express (EDDE) is an autonomous space vehicle that can maneuver throughout low earth orbit without using fuel. EDDE uses solar power to drive multi-ampere currents through a kilometers-long aluminum conductor, creating a force normal to both the conductor and the local magnetic field that drives the space vehicle. The tether spins at about 8 times/orbit. This stabilizes its dynamics and also allows a wider range of electrodynamic thrust directions as it spins. The current circuit is closed through the ambient plasma around the conductor. To provide complete control of the orbit, the highvoltage current must be switched repeatedly as a function of the orbital position, to modulate the force on the conductor. This paper describes our solution to this power switching and control problem. Arcing from the conductor to the ambient plasma is a potentially serious problem. To reduce the possibility of arcing, the solar arrays are distributed along the conductor length to reduce the peak potential between the conductor and the local plasma. If arcing does start, it can be quenched by electrically isolating the tether segments upstream of the arcing section, using high-voltage control switches in each power module. This makes it feasible to pull the arcing segment positive to quench the arc. Each power module includes an "H-bridge" so the solar array can drive current through the tether in either direction. Turning the bridge off isolates the conductor segments and array from each other, to help quench arcs from both the array and the conductor. The bridge also includes a shunt switch so tether current can bypass the solar array. This lets EDDE continue operating despite failed power switches or mis-aimed solar arrays. Effective control of current and arcing requires communication between the modules. This can be done optically, or with RF signals transmitted along the conductor, superimposed on the drive current. The entire space vehicle electrical system and switching circuitry are simulated on the "Virtual Test Bed" at the University of South Carolina to demonstrate system performance and design optimization.

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Section: Electrodynamic Loop and Forcementioning

confidence: 99%

High Voltage Power Switching for a Conducting Tether

Harkare¹,

Dougal²,

Carroll³

et al. 2004

2nd International Energy Conversion Engineering Conference

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“…A high altitude and low gravity test were conducted in 2015 [4]. NASA developed a tether-net catching mechanism named GRASP (Grapple, Retrieve, and Secure Load) [5][6], which uses tethers to form a net structure under the support of inflatable bars to catch loads. The EDDE (Electro-dynamic Debris Eliminator) project [7] funded by DAPPA of the United States plans to launch 12 spacecraft into space, each carrying 200 electromagnetic nets, for cleaning up LEO space debris.…”

Section: Introductionmentioning

confidence: 99%

The research of space net control strategy based on the combination of fixed tearing belt and tether brake

Zhan¹,

Chen²,

Zhang³

2023

AETR

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In order to solve the rebound motion of space tether net during deployment, a new control strategy based on adding tear tape in the plane and applying tether force out of the plane is proposed. The tether segment of the space tether net is discretized, and the lumped mass model is established. According to the mechanical characteristics of the tether, the system dynamic equation is derived. Then the simulation analysis is made from the perspective of evaluating the effect of the control strategy. Through simulation and comparison, it is found that the control strategy has obvious effect on restraining the rebound movement of the tether net.

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“…We developed a design for a spinning electrodynamic tether (SET) and developed several key system components. 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.…”

Section: Magnetic Fieldmentioning

confidence: 99%

Orbital Maneuvering with Spinning Electrodynamic Tethers

Pearson¹,

Levin²,

Carroll³

et al. 2004

2nd International Energy Conversion Engineering Conference

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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. The SET was simulated with a PC-based computer program to evaluate its orbit transfer capabilities. This vehicle is capable of repeated large orbit changes in low earth orbit, totaling >50 km/sec each year for several years. Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. Nomenclature and Acronyms

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ElectroDynamic Delivery Express (EDDE) In-Space Demonstrator

Cited by 16 publications

References 9 publications

High Voltage Power Switching for a Conducting Tether

High Voltage Power Switching for a Conducting Tether

The research of space net control strategy based on the combination of fixed tearing belt and tether brake

Orbital Maneuvering with Spinning Electrodynamic Tethers

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