Missel J.,Texas A&M University |
Mortari D.,Aerospace Engineering
Journal of Guidance, Control, and Dynamics | Year: 2013
Low Earth orbit is overcluttered by rogue objects. Traditional satellite missions are not efficient enough to collect an appreciable amount of debris due to the high cost of orbit transfers. Many alternate proposals are politically controversial, costly, or dependent on further technological advances. This paper proposes an efficient mission structure and bespoke hardware to deorbit debris by capturing and ejecting them. These are executed through plastic interactions, and the momentum exchanges during capture and ejection assist the satellite in transferring to subsequent debris with substantial reduction in fuel requirements. The proposed hardware also exploits existing momentum to save fuel. Capturing debris at the ends of a spinning satellite, adjusting angular rate, and then simply letting go at a specified time provides a simple mechanism for redirecting the debris to an Earth-impacting trajectory or lower perigee. This paper provides analyses for orbit and hardware functionality and aspects of the control for debris collection. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source
The research team have developed the first demonstration of 3D printing of composite materials. Ultrasonic waves produce a pattern of microscopic glass fibres which give the component increased strength. A laser cures the epoxy resin and creates the component. Credit: Matt Sutton, Tom Llewellyn-Jones and Bruce Drinkwater 3D printing techniques have quickly become some of the most widely used tools to rapidly design and build new components. A team of engineers at the University of Bristol has developed a new type of 3D printing that can print composite materials, which are used in many high performance products such as tennis rackets, golf clubs and aeroplanes. This technology will soon enable a much greater range of things to be 3D printed at home and at low-cost. The study published in Smart Materials and Structures creates and demonstrates a novel method in which ultrasonic waves are used to carefully position millions of tiny reinforcement fibres as part of the 3D printing process. The fibres are formed into a microscopic reinforcement framework that gives the material strength. This microstructure is then set in place using a focused laser beam, which locally cures the epoxy resin and then prints the object. To achieve this the research team mounted a switchable, focused laser module on the carriage of a standard three-axis 3D printing stage, above the new ultrasonic alignment apparatus. Tom Llewellyn-Jones, a PhD student in advanced composites who developed the system, said: "We have demonstrated that our ultrasonic system can be added cheaply to an off-the-shelf 3D printer, which then turns it into a composite printer." In the study, a print speed of 20mm/s was achieved, which is similar to conventional additive layer techniques. The researchers have now shown the ability to assemble a plane of fibres into a reinforcement framework. The precise orientation of the fibres can be controlled by switching the ultrasonic standing wave pattern mid-print. This approach allows the realisation of complex fibrous architectures within a 3D printed object. The versatile nature of the ultrasonic manipulation technique also enables a wide-range of particle materials, shapes and sizes to be assembled, leading to the creation of a new generation of fibrous reinforced composites that can be 3D printed. Bruce Drinkwater, Professor of Ultrasonics in the Department of Mechanical Engineering, said: "Our work has shown the first example of 3D printing with real-time control over the distribution of an internal microstructure and it demonstrates the potential to produce rapid prototypes with complex microstructural arrangements. This orientation control gives us the ability to produce printed parts with tailored material properties, all without compromising the printing." Dr Richard Trask, Reader in Multifunctional Materials in the Department of Aerospace Engineering, added: "As well as offering reinforcement and improved strength, our method will be useful for a range of smart materials applications, such as printing resin-filled capsules for self-healing materials or piezoelectric particles for energy harvesting." Explore further: Breakthrough in 3-D printing of replacement body parts More information: Thomas M Llewellyn-Jones et al. 3D printed components with ultrasonically arranged microscale structure, Smart Materials and Structures (2016). DOI: 10.1088/0964-1726/25/2/02LT01
Once unpacked, Commander Scott Kelly will attach the satellite to the JEM slide table interfaced with CYCLOPS, a mechanism used to robotically deploy satellites from ISS. The CYCLOPS Experiment Attachment Fixture (EAF) is attached to the large cylindrical CYCLOPS Standoff on the bottom of AGS4. The EAF will be used to lock AGS4 onto the deployment table which will release the satellite from the ISS. The deployment activities scheduled for Friday include capturing CYCLOPS with the JEM Remote Manipulator System, maneuvering CYCLOPS to the deployment location, and final deployment of AGS4 from CYCLOPS. An example of the deployment mechanism can be seen below. There are four switches, embedded on the CYCLOPS EAF, that inhibit AGS4 from turning. The first event that will occur after deployment will be the release of these inhibits. Once these inhibits are removed, the Electronic Power System (EPS) starts and initiates a 10 minute timer. After the timer ends the Command and Data Handling System starts and initiates a checkout of every system on AGS4. When complete, AGS4 will begin sending a signal to Earth with its Low Data Rate (LDR) radio, indicating that it is alive and well. The team expects to start receiving signals from AGS4 on Friday evening. Several days after the release of AGS4, and upon verification that all systems are running correctly, the satellite will power on its torque coils and detumble itself. The torque coils generate a strong magnetic field that will orient AGS4 along the magnetic field of the Earth. There are three torque coils on board giving full 3-Axis motion. The detumble process will negate any rotation imparted on AGS4 by the CYCLOPS deployment mechanism and orient AGS4 for optimal data downlinking. Once this is done data from the satellite can be downloaded faster and all necessary software patches can be uplinked to AGS4. The AggieSat4 team has been busy preparing for the deployment, setting up the AggieSat ground station at Texas A&M University's Riverside campus. Three antennas have been installed that will be used to communicate with AGS4 while it orbits Earth and collects valuable mission data. One of the LDR antennas has been tested and was able to receive a signal from the same type of handheld radio that is on board the satellite. This antenna will be the main receiver of data transmitted from AGS4 while in orbit. The team is working to ensure the other two antennas transmit and receive properly, and then will raise them to the top of the truss structure they are currently mounted on. Dr. Helen Reed, professor in the Department of Aerospace Engineering, and the AggieSat team members will be at NASA Johnson Space Center in Houston for the installation and deployment activities. Team members Dexter Becklund and Andrew Tucker will sit on console in Mission Control to assist the astronauts with unpacking, assembly, procedures and any queries. AggieSat team members include Adelin Destain, David Alfano, Dexter Becklund, Ryan Campbell, Jake Cooper, Daniel Ghan, Michelle Gilbert, Hyder Hasan, Andy Holm, Alex Hutson, Mitchel McDonald, Sig Salinas, Robert Singletary and Andrew Tucker.
Say hello to Nadine, a “receptionist” at Nanyang Technological University (NTU Singapore). She is friendly, and will greet you back. Next time you meet her, she will remember your name and your previous conversation with her. She looks almost like a human being, with soft skin and flowing brunette hair. She smiles when greeting you, looks at you in the eye when talking, and can also shake hands with you. And she is a humanoid. Unlike conventional robots, Nadine has her own personality, mood and emotions. She can be happy or sad, depending on the conversation. She also has a good memory, and can recognize the people she has met, and remembers what the person had said before. Nadine is the latest social robot developed by scientists at NTU. The doppelganger of its creator, Professor Nadia Thalmann, Nadine is powered by intelligent software similar to Apple’s Siri or Microsoft’s Cortana. Nadine can be a personal assistant in offices and homes in future. And she can be used as social companions for the young and the elderly. A humanoid like Nadine is just one of the interfaces where the technology can be applied. It can also be made virtual and appear on a TV or computer screen, and become a low-cost virtual social companion. With further progress in robotics sparked by technological improvements in silicon chips, sensors and computation, physical social robots such as Nadine are poised to become more visible in offices and homes in future. Professor Thalmann, the director of the Institute for Media Innovation who led the development of Nadine, said these social robots are among NTU’s many exciting new media innovations that companies can leverage for commercialization. “Robotics technologies have advanced significantly over the past few decades and are already being used in manufacturing and logistics. As countries worldwide face challenges of an aging population, social robots can be one solution to address the shrinking workforce, become personal companions for children and the elderly at home, and even serve as a platform for healthcare services in future,” explained Professor Thalmann, an expert in virtual humans and a faculty from NTU’s School of Computer Engineering. “Over the past four years, our team at NTU have been fostering cross-disciplinary research in social robotics technologies — involving engineering, computer science, linguistics, psychology and other fields — to transform a virtual human, from within a computer, into a physical being that is able to observe and interact with other humans. “This is somewhat like a real companion that is always with you and conscious of what is happening. So in future, these socially intelligent robots could be like C-3PO, the iconic golden droid from Star Wars, with knowledge of language and etiquette.” Telepresence robot lets people be in two or more places at once Nadine’s robot-in-arms, EDGAR, was also put through its paces at NTU’s new media showcase, complete with a rear-projection screen for its face and two highly articulated arms. EDGAR is a tele-presence robot optimized to project the gestures of its human user. By standing in front of a specialized webcam, a user can control EDGAR remotely from anywhere in the world. The user’s face and expressions will be displayed on the robot’s face in real time, while the robot mimics the person’s upper body movements. EDGAR can also deliver speeches by autonomously acting out a script. With an integrated webcam, he automatically tracks the people he meets to engage them in conversation, giving them informative and witty replies to their questions. Such social robots are ideal for use at public venues, such as tourist attractions and shopping centers, as they can offer practical information to visitors. Led by Associate Professor Gerald Seet from the School of Mechanical & Aerospace Engineering and the Being There Centre at NTU, this made-in-Singapore robot represents three years of research and development. “EDGAR is a real demonstration of how telepresence and social robots can be used for business and education,” added Professor Seet. “Telepresence provides an additional dimension to mobility. The user may project his or her physical presence at one or more locations simultaneously, meaning that geography is no longer an obstacle. “In future, a renowned educator giving lectures or classes to large groups of people in different locations at the same time could become commonplace. Or you could attend classes or business meetings all over the world using robot proxies, saving time and travel costs.” Given that some companies have expressed interest in the robot technologies, the next step for these NTU scientists is to look at how they can partner with industry to bring them to the market.
The Soret Coefficient in Crude Oil experiment will measure how hydrocarbon molecules redistribute when the temperature is not uniform. Learning how complex liquids behave is of interest to the petroleum industry and academia, who can apply the data to model real-life conditions of oil reservoirs deep underground. These measurements can only be performed in weightlessness. Set for launch on China's SJ-10 satellite on 6 April local time, the experiment consists of six sturdy cylinders, each containing just one millilitre of crude oil but compressed up to 500 times normal pressure at sea level on Earth – making it one of the highest-pressure items ever launched into space. Lifting-off from China's Juiquan site in the Gobi desert, the satellite will spend almost two weeks in orbit before it returns to Earth. After landing in Si Chuan province, the team will retrieve the experiment for detailed analysis. The experiment is a partnership between ESA, China's National Space Science Centre, France's Total oil company and China's PetroChina oil company. "The experiment is designed to sharpen our understanding of deep crude oil reservoirs up to 8 km underground," explains Antonio Verga, overseeing the project for ESA. "Imagine a packet of cornflakes – over time the smaller flakes drop to the bottom under gravity. On a molecular scale this experiment is doing something similar but then looking at how temperature causes fluids to rearrange in weightlessness," says ESA's Olivier Minster. "Deep underground, crushing pressure and rising temperature as one goes down is thought to lead to a diffusion effect – petroleum compounds moving due to temperature, basically defying gravity. "Over geological timescales, heavier deposits end up rising, while lighter ones sink. "The aim is to quantify this effect in weightlessness, to make it easier to create computer models of oil reservoirs that will help guide future decisions on their exploitation." The experiment's crude oil sits in six small titanium cylinders. One end of each cylinder is warmed while the other end is cooled. Before returning to Earth, a valve is closed to prevent the liquid from remixing during reentry. Sending such a high-pressure device into space is not to be taken lightly and the cylinders were built to withstand more than double pressure than they will during normal operations – 1000 times atmospheric pressure. A specialist company, Sanchez Technology in France, worked for the prime contractor QinetiQ Space in Belgium. The electronic unit was developed and built by the Shandong Institute of Aerospace Engineering at Yantay. The experiment passed testing with the SJ-10 spacecraft at the China Academy of Space Technology in Beijing, China last year – including thermal cycling to reproduce the extreme changes in temperature the experiment will be subjected to during its orbits of Earth, as well as vibration and shock testing to simulate launch and reentry. Two weeks ago ESA and QinetiQ staff took the 8.5 kg flight unit – about the size of a desktop computer – on a four-day drive to the remote launch site in Gansu province. The experiment with its oil-filled cells is now ready for its journey to space tomorrow. Explore further: From earth to space and back again