Large Communication Satellite Research Articles

Integration of energy storage functionalities into fiber reinforced spacecraft structures

One of the common challenges of spaceflight and e-mobility is the energy storage. The operational ranges of spacecraft or electric cars as well as operational usability is strongly dependent on the capacity of the energy storage, which is usually constrained by the mass and volume of the vehicle. For example, the battery mass of large communication satellites ranges from 6% to 9% of the dry mass. This amount increases for smaller satellites like CubeSats up to 13% without accounting wiring harnesses and subsystem volume. Thus, a system can benefit from a reduction in mass and volume by combining multifunctional use of the components and materials. In the presented research, energy storage is integrated into lightweight carbon fiber materials. Carbon fibers have a distinct mass advantage compared to metal structures. In addition, they have very low thermal expansions that can reduce thermal stresses during the operation of a satellite. Fiber composites or laminates consist of two components, the fibers and the matrix material. In laminates, the typically resin based matrix content is 30–40% of the component volume and could be substituted with novel solid state battery materials. Latter have the advantage that they have nearly similar physical properties as usually used resins and are also able to store energy electrochemically. Thus, about 25% of the volume can be used for electrochemical energy storage without compromising structure integrity. To reach such electrochemical functions the host structures have to be infiltrated with anode, cathode, and separator materials. Using the developed recipes and a component thickness of 5 mm, an energy amount per component area of 1130 Wh/m2 can be reached depending on the applied battery active material.This article will give an overview of how fiber composite materials, which are increasingly being used in lightweight construction processes, can be combined with energy storage materials to be used in spacecraft structures. The goal of the research on this topic at the Technische Universtät Braunschweig is a structure battery for a spacecraft. However the article addresses as a first step the characterization and manufacturing of structural battery composite negative half-cells from carbon fiber reinforced PEO/LiTFSI. An estimation of the expected performance is carried out. The initial material evaluation and the manufacturing process as well as mechanical and electrical result will be discussed.

Interactive design and multidisciplinary optimization of geostationary communication satellite

Currently, the design of large geostationary communication satellites is becoming more and more complex systems. On the one hand, customers are demanding high performance communications systems and this for 15–20 years orbital lifetimes. And the other hand, given the large volume and mass of communications satellites, an added constraint that resides in the volume under the launcher fairing which is sometimes represents a great handicap for the technological development of large space systems due to the technological limitation of launchers at the time. Increasing the performance and reliability of communication satellites, tools and methods are needed; the multidisciplinary design optimization methods (MDO) can be useful for this type of complex system. In geostationary communication satellite systems design, there are usually more than one design objectives, which a design team should take into account. These objectives involve system performance measures like mass, size, cost, reliability, power efficiency and system robustness. In a good design procedure, the tradeoffs between competing objectives should be incorporated so that the design team can make an informed decision. In this paper the generic geostationary communication satellite MDO problem is formulated to minimize the total mass of the satellite system under a number of practical constraints including launch vibration and acoustic disciplines. In this paper a gravitational search algorithm based on the law of gravity and mass interactions is introduced. In the proposed algorithm, the searcher agents are a collection of masses which interact with each other based on the Newtonian gravity and the laws of motion. From the results obtained in this paper and after optimization, the total mass of the studied GEO communication satellite is decreased by 185.3 kg (i.e., 7.3% of the total mass). In the case of the presence of two disciplines, acoustics and vibration, we notice that the mass becomes 3470 kg, which means the increase of the total mass of the system in about 124.2 kg and this in order to compensate the effects of these two disciplines.

Distributed driving deployment method and numerical analysis of large hoop truss antenna

As the typical structure of the large satellite antenna, the hoop-truss deployable antenna with large aperture is in urgent need in the new generation of large communication satellite, the relay satellite and the earth observation satellite. At the same time, the requirement of the antenna aperture size tends to become bigger and bigger. However, with the increase of antenna aperture, the driving force required for deployment of antenna is also increasing rapidly, which leads to the reliability problem in the traditional centralized drive mode with the motor and driving cable. The dynamics simulation model of the large Hoop-Truss deployable antenna was established in this paper firstly, and the dynamics simulation of the deployment of the antenna with the motor and driving cable was carried out, respectively. This paper reveals the problem of the asynchronous synchronization of deployment caused by the friction loss of the motor driving force in the load path. The energy consumption during the process of antenna deployment is analyzed, and the growth trend of motor driving force as the antenna aperture increases. The shortcomings of centralized-driving mode with the motor and driving cable are summarized, which mainly caused by the decreasing of driving cable force due to friction. On the basis, a method of distributed drive deployment based on negative stiffness driving device is presented. The design of negative stiffness driving device is given in the paper. The multi-stage non-circular gear device based is used to realize the negative stiffness joints and the design method of key transmission ratio of multi-stage non-circular gear device is also given in the paper. Finally, numerical example of 25 m antenna is demonstrated to verify the effectiveness of the proposed distributed driving method.

Design and Implementation of Robust Symmetric Attitude Controller for ETS-VIII Spacecraft

This paper studies the robust attitude control of the large flexible communication satellite ETS-VIII. As a controller candidate, we propose a two-degrees-of-freedom control based on robust direct velocity and displacement feedback, in order to develop a baseline of future controller design technology for this class of spacecraft. For this purpose, the spacecraft modeling and controller synthesis methods are discussed. Then, the controller implementation for on-orbit control experiment is shown with some simulation results.

ROBUST ATTITUDE CONTROL OF ETS-VIII SPACECRAFT VIA SYMMETRIC CONTROLLER

This paper studies the robust attitude control of large Geo-synchronous communication satellite ETS-VIII. After describing its model features and control issues, a candidate of robust controller design method is proposed. The controller has the form of two-degrees-of freedom control in order to satisfy both specifications of disturbance attenuation and attitude maneuver. The feedback control employs the symmetric controller having the salient robust stability property irrespective of the plant parameters. Its optimization scheme in the H∞ norm sense is discussed. Finally, the on-orbit control experiment plan is shown with some simulation results.

Wireless at high altitudes-environmental effects on space-based assets

Marconi sent the first trans-Atlantic signals nearly 100 years ago, marking the advent of both modern wireless communications and the initial perceptions of the effects of solar-related natural phenomena on these signals. Currently, interest is increasing rapidly in the use of communications systems above the Earth's surface for voice and data transport. From large communications satellites (comsats) in geosynchronous (GEO) orbit to numerous proposed low-Earth-orbit (LEO) spacecraft constellations, several initiatives have been undertaken for the expansion of services ranging from paging, inventory tracking, TV, and telecommunications. This extension of wireless concepts to the third dimension — the high upper atmosphere and space — includes such businesses as service providers, launch vehicle builders, satellite manufacturers, ground station equipment providers, and personal communications device manufacturers. Many of the third-dimension wireless concepts, designs, and implementations require consideration of the Earth's atmosphere and space plasma environments that are mostly inconsequential to conventional wireless operations. This paper provides a brief overview of some current satellite-based concepts, focuses on the atmospheric, ionospheric, space, and solar environments that third-dimension wireless faces, and discusses some gaps in our current knowledge base.

Technologies for spacecraft electric power systems

There is a growing push within the federal government and many private sector space organizations to build and launch spacecraft that are smaller, that can be built and deployed quicker, and that cost less. Even in the classic large communications satellites there is a push to reduce the utility mass so that more transponders can be added or the launch mass reduced, or some combination of both. Furthermore, there is pressure to spin off technologies into the commercial sector as well as to spin in technologies to the space program. The classic electrical power system consists of the power source, energy storage, and power management and distribution (PMAD). This article addresses these electrical power technologies, including high-performance photovoltaic devices, solar dynamic systems, batteries, and PMAD architectures, showing that in each case new technologies are available that can reduce the overall mass of the electrical power system by at least 50%.

Ion propulsion — a technology for improving the cost-effectiveness of large communications satellites

The overall launch mass of a communications satellite has a major influence on its economic performance. If this mass can be reduced substantially, the launch cost will be lower, or more revenue can be generated by carrying a larger payload or extending the operational lifetime. Since an ion propulsion system provides an exhaust velocity at least an order of magnitude higher than that of chemical thrusters, the propellant mass required for north–south station-keeping can be reduced by hundreds of kilogrammes, thereby gaining these benefits. This application of ion propulsion is discussed and quantified in the paper, for the Intelsat VII spacecraft and the UK-10 ion propulsion system.

Status of xenon ion propulsion technology

This paper describes a working-model xenon ion propulsion subsystem (XIPS) designed for north-south stationkeeping (NSSK) of 2500-kg-class geosynchronous communication satellites. The XIPS consists of a 25-cm-diameter laboratory-model thruster, a breadboard-model power supply, and a flight-prototype pressure regulator (the critical component of the pressure-regulated xenon feed system). With a thrust of 63.5 mN, specific impulse of 2800 sec, and thruster efficiency of 65 percent, the XIPS performance is believed to be the highest ever reported for an ion thruster operated at 1.3-kW input power. The XIPS power supply accepts an input power of about 1.4 kW from a 28- to 35-V bus and converts it into the seven outputs required for startup and operation of the thruster. The simplified power supply contains only about 500 parts and has demonstrated an unprecedented efficiency of 90 percent and a specific mass of about 8 kg/kW. The results of a highly successful wear-mechanism test in which the working-model XIPS was operated for 4350 hours and 3850 ON/OFF cycles are presented. These hours and cycles are equivalent to over ten years of NSSK on large communication satellites.

Decentralized/Hierarchical Control for Large Flexible Spacecraft

Abstract Control of large flexible spacecraft requires in general the synthesis of a large set, often diverging requirements. The application of decentralized/hierarchical control schemes allows a fairly independent baseline stabilization of the spacecraft and attached instruments, introduction of active damping for the flexible structure(s) and high accuracy control of space related experiments or instruments. To take into account flexible mode coupling, sensor and actuator dynamics, nonlinearities and mi.xed continuous/digital control loops, the design and stability analysis for the overall system is based on a sequential MIMO-control system design technique. The resulti.ng control a lgorithms prove to be robust against uncertainties in modal parameter determination and spillover effects of the flexible structure(s). The application of the presented control and design concept is demonstrated on the antenna finepointing control system for a large communication satellite, including stability diagrams and simulation results.

Antenna pointing systems for large communications satellites

Most of the geostationary satellites already developed operate antenna pointing through fine orientation measurement and control of the satellite main body to which each antenna is rigidly attached. The main body orientation is measured by means of infrared Earth observation. Increasing antenna size and power and, sometimes, political constraints enhance the benefit of very accurate antenna pointing (0.05 deg, 3 a at antenna electrical axis level). This typically implies direct measurement of antenna orientation through the use of radio-frequency sensors incorporated in each antenna, mechanical decoupling between antennae to allow for compensation of structural deformations, and mechanical decoupling between each antenna and the satellite main body through the use of antenna pointing mechanisms to allow for high antenna control bandwidth. Concepts of antenna pointing mechanism and associated control for such satellites are presented shortly. Pointing performances of attitude control concepts alternatives are shown for a typical payload.

Advanced high capacity domestic satellite communications system

This paper describes a concept of multibeam high capacity transmission possible with a 30/20 GHz and 50/40 GHz domestic satellite communication system. The relationship between satellite antenna pointing accuracy and multi-beam antenna interference, as well as the relationship between satellite antenna pointing accuracy and multi-satellite interference are looked at. The ultra high capacity domestic satellite communication system will have multi-beam antennas with a 76.0 dB at both 20 GHz and 40 GHz. These antennas will provide 4950 beams that approximately correspond to the number of end office of the Japanese telephone network, and have a pointing accuracy of 0.005 degrees. This system will be equipped with 9900 30/20 GHz and 50/40 GHz transponder channels with bit rates of 800 Mbps. Its capacity will be 119 Tbps through use of 15 large communication satellite platforms.

Centaur—The high-energy upper stage for space shuttle

General Dynamics is under contract with NASA to integrate the Centaur high-energy upper stage with the Space Shuttle. This powerful vehicle combination will deliver a Galileo spacecraft to Jupiter, launch the International Solar Polar mission, and have a 14,000-pound capability to geosynchronous orbit for large communication satellites.

The critical satellite technical issues of future pervasive broadband low-cost communication networks

Using a baseline design for a 30/20 GHz system, this paper addresses the critical technical issues of signal waveform design, projected spacecraft technology, satellite launch options and satellite cost. With DPCM (differential pulse-coded modulation) video signal encoding, 32 Mb/s user-to-user data rate per channel, 10% overhead, two orthogonal polarizations, and crosstalk loss limited to 1 dB, TFM (tamed frequency modulation—a type of QPSK) permits about 75 channels/GHz of frequency allocation, i.e. about twice the capacity possible with MSK or SFSK (types of QPSK). The BOM (beginning of mission) weight and power of a baseline 400-channel multi-beam satellite is about 1800 kg and 5000 W. Each 35 Mb/s channel can support 1–10 video channels depending on the signal processing at the ground terminals. These weight and power estimates assume hardened digital logic, composite material for a multibeam antenna structure, high-efficiency solar cells (45 W/kg), NiH 2 batteries and 10W/20 GHz power amplifiers. If more speculative late-1980s solar cell technology is assumed, then the BOM weight decreases about 10–15%. Using the Space Transportation System being developed by NASA, geosynchronous deployment options are shown as a function of communications capacity. Based on a cost model for large communication satellites, the total space segment cost of two active satellites and one spare would be about $485M. This system would have a peak capacity of 14 Gb/s or 400-35 Mb/s simultaneous one-way channels. Demonstration and/or initial system (ground plus space) costs would be significantly less. It is concluded that the above baseline satellite appears to be technically feasible in the late-1980s.

The Future Of Computer/Communications*

AbstractThis is an exciting time to be involved with the subject of computer/communications, since the introduction of new technologies such as Large Scale Integration, fibre optics, and communications satellites is transforming our conception of the art of the possible. As a result, hundreds of systems that were only speculative dreams a few years ago will soon be spreading a web of new services across the globe and, in the process, transforming our lives. In this survey paper, the nature of the technological changes is discussed and an attempt is made to predict both their future development and their impact upon society.