Department of Defense Synchronized Position, Hold, Engage, Reorient, Experimental Satellites-RINGS (DOD SPHERES-RINGS) - 10.14.14
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The Department of Defense SPHERES-Resonant Inductive Near-field Generation System (DOD SPHERES-RINGS) uses two small, self-contained satellites (SPHERES) fitted with donut-like rings (RINGS) to test wireless power transfer and formation flight using electromagnetic fields. The RINGS hardware are equipped with aluminum coils and current control systems and are mounted onto the SPHERES vehicles. The investigation provides insight for the Department of Defense and NASA to develop a new control method for clusters of multiple satellites, and demonstrates the ability to wirelessly transfer power across a medium distance, which could provide greater flexibility of future satellite cluster architectures.
Science Results for Everyone
University of Maryland, College Park, MD, United States
Aurora Flight Sciences Corporation, Cambridge, MA, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
National Laboratory - Department of Defense (NL-DoD)
ISS Expedition Duration
March 2013 - September 2014
Previous ISS Missions
- The DOD SPHERES-RINGS investigation tests hardware and software developed to enable relative station-keeping, maneuvering, and attitude control between two SPHERES facility satellites using steerable electromagnetic dipoles (i.e., magnetic field pointing using orthogonal electromagnetic coils) at a distance on the order of decimeters to a few meters.
- Another goal of this investigation is to demonstrate wireless power transfer through resonant inductive coupling (i.e., the interaction of an oscillating magnetic field between two capacitively loaded inductors (a tuned circuit), using the same hardware developed for EMFF. For this investigation, the SPHERES facility satellites onboard the International Space Station (ISS) are used to demonstrate the use of electromagnetic coils to maneuver individual SPHERES with respect to one another. By controlling the dipoles, attractive, repulsive, and shear forces can be generated. Using the DOD SPHERES-RINGS hardware, software algorithms are created to produce active safety maneuvers to avoid cooperative and uncooperative spacecraft collisions. Using the same coils in the DOD SPHERES-RINGS investigation, the software demonstrates inductive wireless power transfer, where one SPHERES beams power to another SPHERES via resonant inductive coupling.
- The DOD SPHERES-RINGS investigation is the first demonstration of electromagnetic formation flight in microgravity, as well as the first demonstration of wireless power transfer in space. This effort builds on work previously performed for DARPA’s System F6 program, where the Massachusetts Institute of Technology, the University of Maryland, and Aurora Flight Sciences investigated the feasibility of using the same high temperature superconducting coils to perform both electromagnetic formation flight and wireless power transfer.
The SPHERES facility satellites onboard ISS provide the a unique low risk, low cost, long duration microgravity research facility capable of supporting iterative, quick reaction testing of technologies in support of DoD and NASA missions. Under the auspices of the ISS-Hosted SPHERES Integrated Research Experimentation (InSPIRE) program, the DOD SPHERES-RINGS investigation significantly increases the scope of the SPHERES facility by adding hardware and developing new algorithms to execute investigations and tests of new critical technologies.
The DOD SPHERES-RINGS investigation hardware and algorithms were developed to enable autonomous propellant-free, plume-free satellite cluster maintenance. The inductive wireless power transfer experiment aids in establishing the hardware necessary for future wireless powering of space robotic, sensor and enhanced communications systems.
The DOD SPHERES-RINGS investigation uses the SPHERES facility which consists of three self-contained satellites (i.e., SPHERES). Each satellite is an 18-sided polyhedron that is 0.2 meter in diameter and weighs 3.5 kilograms. Individual satellites contain an internal propulsion system, power, avionics, software, communications, and metrology subsystems. The propulsion system uses carbon dioxide (CO2), which is expelled through the cold gas thrusters. SPHERES satellites are powered by AA batteries.
DOD SPHERES-RINGS unique hardware consists of two RINGS Assemblies each consisting of resonant coils, coil housing with fans, power electronics/batteries and RINGS/SPHERES support structure hardware. Each RINGS Assembly has a diameter of 77 cm with a height of 13.5 cm and weighs 8.9 kilograms. Each RINGS Assembly will be powered by two COTS DeWalt DC9180 “pod-style” Lithium Ion 18V 2.0 Ah batteries. 24 DeWalt batteries will be flown to support the operations of DOD SPHERES-RINGS. Two dual battery chargers will also be flown to support recharging of the DeWalt batteries. Each battery charger is 45.5cm X 25.2cm X 17.3cm and weighs 10.5 kilograms.
The DOD-SPHERES-RINGS investigation is the first space-based demonstration of electromagnetic formation flight and wireless power transfer. Hardware and computer control software for the DOD-SPHERES-RINGS investigation demonstrate autonomous plume-free, propellant-free movements of spacecraft. Power transfer by resonant induction (an improvement over cordlessly charging your phone or toothbrush on a charging pad or cradle) and the use of electromagnetic fields for satellite control are approaches that can eliminate the need for consumables (propellant) and provide more flexibility to system architectures. These have the potential to substantially increase the operating lifetime of the cluster, reduce system mass and reduce operating risks, all of which can contribute to greater return on investment. The wireless power transfer experiment also aids in establishing the hardware required to power future robotics systems, sensors and communications equipment.
Wireless inductive power transfer is already being used in electronics and household items such as cell phones and toothbrushes. Broadening this approach to include resonance can increase the efficiency and transfer distance to benefit future urban robotics and sensors, as well as support more efficient underwater communications systems. DOD-SPHERES-RINGS investigates methods and hardware necessary for improving wireless power transfer.
The SPHERES facility is allocated a number of test sessions per ISS Increment. Four test sessions will be utilized by DOD SPHERES-RINGS as the facility user. As the facility lead, NASA Ames will determine specific test session scheduling based on ongoing planning and research results.
A typical DOD SPHERES-RINGS test session will consist of:
- Uplink algorithms one week before the test session.
- Charge 24 batteries prior to each test session.
- Unstow and configure SPHERES facility satellites and work area.
- Attach and configure the DOD SPHERES-RINGS hardware to the SPHERES satellites.
- Load algorithms onto the SPHERES through the communication system.
- Cross-link of real-time data to the ISS ELC laptop.
- Downlink of the data for post-session assessment.
During Expedition 35/36 two SPHERES-RINGS assemblies were tested on board the ISS. The first set of tests involved a configuration where one of the SPHERES-RINGS assemblies was fixed to the module wall in order to check out the wireless power transfer and electromagnetic formation flight capability. Thrusters were not used during these tests. Both coils were activated and power transfer of 30% efficiency was successfully achieved. The test also demonstrated the ability for the two resonant coils to command and maintain a constant 180° phase relationship between the magnetic fields of the respective assemblies. The free floating SPHERES-RINGS assembly was moved to an approximate initial position by a crew member. Both SPHERES-RINGS were allowed to attract and repel using only magnetic dipole interactions. This provides the concept that the SPHERES-RING assemblies were able to actuate vehicles using electromagnetic fields (Porter 2014).
Porter AK, Alinger DJ, Sedwick RJ, Merk J, Opperman RA, Buck A, Eslinger G, Fisher P, Miller DW, Bou E. Dual-purpose resonate actuators for electromagnetic formation flight and wireless power transfer. AIAA Guidance, Navigation and Control Conference, National Harbor, Maryland; 2014 January 13-17 18 pp.
Porter AK, Alinger DJ, Sedwick RJ, Merk J, Opperman RA, Buck A, Eslinger G, Fisher P, Miller DW, Bou E. Demonstration of electromagnetic formation flight and wireless power transfer. Journal of Spacecraft and Rockets. 2014 September 26; epub: 10 pp. DOI: 10.2514/1.A32940.
Ground Based Results Publications
Alinger DJ, Porter AK, Sedwick RJ. Optimization of resonant inductive wireless power transfer using multilayer flat spiral coils. Journal of Spacecraft and Rockets. 2014 August 5; epub: 9 pp. DOI: 10.2514/1.A32901.
MIT Space Systems Laboratory
SPHERES Facility-Single Unit
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RINGS Conceptual Image
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