Khairnasov S.,Kharkiv Polytechnic Institute |
Andraka C.E.,Sandia National Laboratories |
Baturkin V.,Kharkiv Polytechnic Institute |
Baturkin V.,Institute of Space Systems |
And 2 more authors.
Applied Thermal Engineering | Year: 2017
Sandia National Laboratories and Heat Pipes Laboratory of National Technical University of Ukraine «KPI» have developed several methods of improving robustness of the high-temperature heat pipe wick for their application to concentrating solar power systems with Stirling engine. In this case the wick structures must retain high heat pipe performance with robustness for long-term operation. Recent modeling indicates that wicks based on various fiber combinations could provide the robustness combined with sufficient performance. Results of the development, characterization, modeling, and testing of advanced felt metal wicks that addresses durability issues while maintaining sufficient performance are showed in the paper. The project resulted in an ongoing durability bench-scale heat pipe that simulates wick load conditions required for 80kWth throughput solar receiver, including periodic non-destructive evaluation of the wick durability. Two mock-ups of high-temperature heat pipes were made for long life and performance tests: the first sample with wick based on 12. μm fibers; and the second with hybrid wick based on 30. μm fibers and 6.5. μm fibers. The second heat pipe operation has continued unattended at 775. °C vapor temperature for nearly 13,600. h, with no observable loss of performance or change in startup characteristics. © 2017 Elsevier Ltd.
Montag C.,University of Stuttgart |
Herdrich G.,Institute of Space Systems |
Schonherr T.,European Space Agency
Proceedings of the International Astronautical Congress, IAC | Year: 2016
Next to theoretical design of a Pulsed Plasma Thruster (PPT) experimentally characterization is a major process within the overall development. Due to this a new test facility, a so called Hardware-In-the-Loop (HIL) test facility, for PPTs at the Institute of Space Systems (IRS) at University of Stuttgart is developed. The test stand is based on existing measuring instruments as well as know-how gathered during the long-term development and investigation of PPTs at IRS, i.e. ADD SIMPLEX, PETRA and PET. The HIL facility is distinguished by being compact, modular and extensible for future experiments enabling a characterization of miniature PPTs and Pulsed Electrothermal Thrusters (PET) in the energy range of some Joules. Main basis for the test stand is an already existing and well proven micro Newton thrust pendulum. In order to set up the HIL facility the pendulum is equipped with several measuring instruments to receive thruster specific performance data, i.e. thrust, capacitor's discharge current and voltage as well as magnetic field data of the plasma plume. Additionally, high speed imaging of the plasma plume will be performed. To investigate the thruster's behavior at different capacitances, capacitors can be disabled or engaged during test campaigns enabling, e.g. investigation of a complete or temporally failure of capacitors during a mission. The development of the HIL facility is in close connection to the new development thruster PETRUS (Pulsed Electric Thruster of the University of Stuttgart). PETRUS is a coaxial, PTFE based, low energy thruster designed and optimized for CubeSat applications like "CubeSat Atmospheric Probe for Education" (CAPE). As PPTs are characterized by a simple design and a high reliability, PETRUS shall be used as a primary propulsion system performing a controlled de-orbit maneuver. Furthermore, the modular design of PETRUS allows the investigation of thermal and magnetodynamic effects by using different attachments, e.g. nozzle or cylindrical acceleration path making it possible to: 1) verify or improve present simulation models and 2) investigate scaling laws of PPTs. This paper describes the development of a state-of-the-art HIL test facility characterizing low energy PPTs and PETs. Moreover, a new PPT based thruster (PETRUS) for CubeSat applications is introduced which is tested and characterized by using the HIL facility.
News Article | February 3, 2016
The object, tagged as WT1190F, reentered Earth's atmosphere near the coast of Sri Lanka on Nov. 13, 2015. The researchers' video evidence was revealed in a special session on aerothermodynamics of meteor entries during the recent American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum and Exposition meeting in San Diego. "This object entered much like a small asteroid, creating a 12-second long meteor," said lead author Peter Jenniskens of the SETI Institute in Mountain View, California, and NASA's Ames Research Center in Moffett Field, California. "We observed the sequence in which WT1190F broke apart at 37 miles altitude, and then tracked more than 18 fragments." Jenniskens teamed with Mohammad Odeh, director of the International Astronomical Center (IAC) in Abu Dhabi, to lead a veteran team of NASA- and European Space Agency (ESA)- supported scientists in the mission. The airborne observing campaign was sponsored by IAC and the United Arab Emirates (UAE) Space Agency, who chartered a G450 business jet to bring the team to the view the entry while airborne. "All teams were successful in collecting data," said Odeh. "We managed to dodge the clouds that hampered the observers on the ground and had a prime view of the entry from an altitude of 45,000 feet." The team was supported by astronomers worldwide, who tracked the object in space and reported their observations to the Minor Planet Center, the clearinghouse for asteroid observations. Orbit dynamicists at NASA's Center for near-Earth Object (NEO) Studies hosted at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, then calculated the exact time of the entry to an accuracy of 0.1 seconds. "This space debris object entered the atmosphere at an angle of 20.6 degrees and had a speed of 6.5 miles per second relative to the atmosphere at 62 miles altitude," said Davide Farnocchia of JPL. "The tricky part in predicting the place and time of impact was to account for the weak but important push of the sun's radiation pressure on this artificial, mostly hollow, object of unknown shape." As expected, the best observations were made in the hours before reentry, when the small one-meter sized object became relatively bright, but was also quick and hard to track in telescopes. "An astronomer in the United Kingdom recorded a rapid flicker that showed WT1190F spinning once every 1.5 seconds," said Jenniskens, who recorded a wide-angle view of the entry onboard the aircraft. "When WT1190F entered Earth's atmosphere, it showed a similar flicker from how it broke apart." The research team used a variety of techniques to study the entry, including high resolution imaging, photometry and spectroscopy. The IAC team collected visible photometric observations, while a team from the Institute of Space Systems from the University of Stuttgart, Germany, collected near-infrared broadband photometric data. A team from Dexter Southfield in Brookline, Massachusetts, recorded the breakup in a color video and obtained spectroscopic signatures at the time of peak brightness, despite the bright background of the daytime sky. "One fragment showed the distinct broad-band emissions of the titanium oxide radical and emission from hydrogen," said Ron Dantowitz of Dexter Southfield. Jenniskens suspects that this data points to a disrupting titanium tank with some residual fuel. These and other clues may help identify the nature of this still unidentified object. The UAE Space Agency team tracked the fragments the longest in the daytime sky using a monochrome camera. They tracked two objects down to 22 miles in altitude, where the objects left their field of view. "It is possible that what was left of those fragments fell in the Indian Ocean," said Darrel Robertson, a contractor with the Science and Technology Corporation working at NASA's Ames Asteroid Threat Assessment Project. He had applied tools used for asteroid impact calculations to find that certain artificial objects can survive mostly intact even in these conditions. The success of the mission has given Jenniskens new confidence that a future asteroid impact can be observed if the team is able to respond quickly enough. "It won't be easy. For small asteroids of a few meters in size, we will probably get only a few days of warning," he said. Explore further: Reentry data will help improve prediction models
Detrell G.,Institute of Space Systems |
Detrell G.,Polytechnic University of Catalonia |
Griful i Ponsati E.,Polytechnic University of Catalonia |
Messerschmid E.,Institute of Space Systems
Advances in Space Research | Year: 2016
The aim of this paper is to optimize reliability and mass of three CO2 extraction technologies/components: the 4-Bed Molecular Sieve, the Electrochemical Depolarized Concentrator and the Solid Amine Water Desorption. The first one is currently used in the International Space Station and the last two are being developed, and could be used for future long duration missions. This work is part of a complex study of the Environmental Control and Life Support System (ECLSS) reliability. The result of this paper is a methodology to analyze the reliability and mass at a component level, which is used in this paper for the CO2 extraction technologies, but that can be applied to the ECLSS technologies that perform other tasks, such as oxygen generation or water recycling, which will be a required input for the analysis of an entire ECLSS. The key parameter to evaluate any system to be used in space is mass, as it is directly related to the launch cost. Moreover, for long duration missions, reliability will play an even more important role, as no resupply or rescue mission is taken into consideration. Each technology is studied as a reparable system, where the number of spare parts to be taken for a specific mission will need to be selected, to maximize the reliability and minimize the mass of the system. The problem faced is a Multi-Objective Optimization Problem (MOOP), which does not have a single solution. Thus, optimum solutions of MOOP, the ones that cannot be improved in one of the two objectives, without degrading the other one, are found for each selected technology. The solutions of the MOOP for the three technologies are analyzed and compared, considering other parameters such as the type of mission, the maturity of the technology and potential interactions/synergies with other technologies of the ECLSS. © 2016 COSPAR.
Di Mauro G.,Dinamica Srl |
Schlotterer M.,German Aerospace Center |
Schlotterer M.,Institute of Space Systems |
Theil S.,German Aerospace Center |
And 2 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2015
A new algorithm based on differential algebra is proposed to obtain a high-order Taylor expansion of the statedependent Riccati equation solution. The main advantage of this approach is that the suboptimal solution of a class of nonlinear optimal control problems, characterized by a quadratic cost function and an input-affine plant model, is obtained by a mere evaluation of a polynomial expression, reducing the computational effort due to a well-known algorithm for the state-dependent Riccati equation solution.Arelative position tracking and attitude synchronization problem involving docking maneuvering operations between two Earth satellites is investigated. Particularly, two possible docking scenarios are simulated by using a specific platform designed by DLR, German Aerospace Center, Institute of Space Systems to emulate the satellite motion on ground. The experiments show the effectiveness of the proposed differential-algebra-based algorithm and the potential computational benefit when it runs on real hardware. © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
News Article | March 21, 2016
One thousand kilometres from the Antarctic coast, a 12-strong crew is overwintering at one of the most remote places on Earth. The Concordia Station, a French-Italian research base on the Antarctic Ice Sheet, is truly in the middle of nowhere; the next nearest station is 560km away, and all the crew can see if they look around is flat whiteness. The last plane left for the winter in February, leaving the base completely isolated. It won’t see the Sun for four months and temperatures will drop to below -60 Celsius. Oh, and because it’s 3,200 metres above sea level, inhabitants have to make do with about a third less oxygen than at sea level. It’s not a normal environment for humans, which is exactly why Floris van den Berg is there. A medical doctor sponsored by the European Space Agency, Van den Berg is running a series of research projects at Concordia to explore the physical and psychological effects of living in such surroundings—and the results could give an insight into how we’ll cope with long-distance space travel. “ESA is interested in this place because it’s one of the only places that you have, like, true isolation,” Van den Berg said in an interview over Skype. We spoke after his colleagues were asleep, as he conceded that the 512kbps satellite connection at the base was “quite shitty” if multiple people tried to Skype at the same time. A family doctor from the Netherlands, Van den Berg said it was the remote location that attracted him to the unusual job posting in the first place. Having served as a doctor on expeditions around the world, deepest Antarctica seemed like an impressive location to add to the list. “Working for the European Space Agency is also quite cool in my opinion,” he added. Concordia has several rather unique parallels with space, which makes it ideal for ESA’s research. As we venture further afield—to Mars, for example—astronauts will be spending more time in close quarters and completely isolated from the rest of the world. With current technology, it takes around eight months to send a robotic mission to the Red Planet. Given its total isolation for months at a time, Concordia is sometimes nicknamed “White Mars.” Van den Berg is responsible for collecting a varied slate of samples and data to help give insight into how this environment could affect humans’ physical and psychological wellbeing. One particularly interesting study involves teaching his crewmates to drive a flight simulator of the Soyuz spacecraft, which is currently used to transport astronauts to the International Space Station. It’s a stripped-down simulator with one seat and two joysticks, which users can practice piloting and docking. Van den Berg explained that it’s installed in the Concordia laundry room because it wouldn’t fit in his lab. After initial instruction, he will split his team into two groups; one will receive training on the simulator every month and the other every three months, and he’ll monitor their performance to see how quickly their abilities fade in the environment. “The idea is, if you send people to Mars and they’re going to be in a spaceship for six to nine months they’ll probably get a bit bored, but when they arrive at Mars they have to be quite focused on how to land the Mars lander,” he explained. The 'Simskill' Soyuz simulator. Image: Institute of Space Systems, University of Stuttgart–Andreas Fink Another Antarctic base, British Halley VI, is also conducting the simulator training. As Halley is at a lower altitude, this should help distinguish the impact of the isolation factor from that of the hypoxic conditions. A control is also being run in Stuttgart, Germany. Unsurprisingly, the flight simulator is the most popular of Van den Berg’s experiments, and he admitted he sometimes does it in his free time too. Aside from the simulator, Van den Berg runs regular tests on himself and the rest of the team, which consists of technical staff and researchers working in fields such as climate and astronomy. Using a CT scanner (the first one in Antarctica, installed in the video room) he looks at people’s bone density, which is a major health issue in space travel. He also takes blood samples and analyses them using flow cytometry—which sorts the different cells in the sample—to see how the conditions affect the immune system; NASA astronauts on the ISS are also doing this, which will offer an interesting comparison. “You see a lot of changes, especially in the beginning when people arrive,” Van den Berg said. “Because of the lack of oxygen, you see stress hormones go up quite a bit, which sort of suppresses the immunological response.” Psychological factors are naturally as pressing as physiological ones when it comes to being cooped up for so long, and Van den Berg regularly asks people to fill in questionnaires about their mood and sleep habits. Participants also wear watches that track their activity (especially useful for tracking sleep, which people are often bad at accurately reporting) and interact with beacons on the base to record their movements. “I was quite surprised that everyone was OK with participating with this study, because it’s really like ‘Big Brother is watching,’” said Van den Berg. Participation in all of the research is voluntary. The current Concordia crew on their arrival. Image: ESA/IPEV/PNRA-B. Healey “What’s known from previous years is that in the winter everyone gets a little bit down, so people isolate themselves a bit more [and] spend more time in their bedroom and less in the living room,” he added. “This is something you can measure in detail, to see what the group dynamics are, who is visiting which areas, and how much time people spend alone or with each other.” This is all correlated with people’s questionnaire responses. Of course, Van den Berg is not immune to the psychological effects that he’s collecting data on, and he said that part of his attraction to the job was the “personal experiment” of living at the base. He said the biggest challenges, after adapting to the low oxygen, were coping with the isolation and also having to constantly bug his cohabitants to take part in his studies on top of their own work. There is another doctor at the research base to act as a clinician if people get sick or injured (the base is equipped for surgery as it’s impossible to get people to a hospital for a large chunk of the year, though the team is naturally as careful as possible not to need it). Van den Berg heads up the rescue team if there’s an incident outside the base—“with the cold here it’s really just what we call ‘scoop and run’: get them on a plank and get them inside,” he said. There is the occasional unexpected setback. When his CT machine arrived at the base in a shipping box, it had a hole in the side that looked suspiciously like a forklift had run into it. Without a repair service for thousands of kilometres, Van den Berg had to figure out how to fix it himself, with help over email and Skype. “Luckily there wasn’t too much structural damage and with tape and common sense I could fix it,” he said. With most of a year left to go, Van den Berg sounded enthusiastic about his mission but a little apprehensive. “I’m always ending up with these things where you think, ‘Oh it’s really nice!’ and then you end up in the middle of nowhere and you think, ‘Why did I do this?’ This is, I think, the story of my life,” he said. “But I’m happy because it’s a really interesting place to be.” So far, he hasn’t lost his travel bug, and working for ESA has given him a taste for venturing even further afield. Now 32, he said that if ESA were to put out a call for astronauts soon, he’d apply. With the White Mars experience under his belt, he has more of an idea than most about what he’d be letting himself in for. Correction: This story originally put the base's altitude at 2,300 m above sea level; it's actually 3,200 m. We've corrected the typo.
D'Onofrio V.,University of Naples Federico II |
Sagliano M.,Institute of Space Systems |
Arslantas Y.E.,Institute of Space Systems
2016 AIAA Guidance, Navigation, and Control Conference | Year: 2016
In this paper the effects of the use of the dual-based hybrid Jacobian computation in combination with the Pseudospectral Methods are thoroughly inspected. The dual-step dif- ferentiation method is implemented in SPARTAN (SHEFEX-3 Pseudospectral Algorithm for Re-entry Trajectory ANalysis), a tool based on the use of the global Flipped Radau Pseudospectral method for the transcription of optimal control problems. The dual number theory is exploited to provide an exact computation of the Jacobian matrix associated with the NonLinear Programming (NLP) problem to be solved. The dual-step differentiation method is compared to standard differentiation schemes (the central difference and the complex-step approximations) and applied in the solution of two examples of opti- mal control problem using two different off-the-shelf NLP solvers (SNOPT and IPOPT). Differentiation based on dual number theory is proved to be a valid alternative to the tradi- tional, well-known, differentiation schemes as its use improves, for the problems analysed, the accuracy of the results, especially in combination with SNOPT. © 2016 American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.
Fulge H.,Institute of Space Systems |
Lohle S.,Institute of Space Systems |
Fasoulas S.,Institute of Space Systems
44th AIAA Thermophysics Conference | Year: 2013
Analysis of measurements of water vapour temperature and mole fraction in high temperature environments up to 2000K using tunable diode laser absorption spectroscopy (TDLAS) is presented. The experiments are performed with vertical cavity surface emitting laser diodes (VCSEL) which are wavelength tunable by current and temperature. From a theoretical analysis based on numerical calculations of the combustion process, absorption line profiles have been calculated. Two different wavelength regimes have been found to be suitable, around 950nm and around 1993 nm. Measurements at 950nm have been published previously and a similar setup has been installed and tested with hydrogen- oxygen flames of a McKenna at flame. The result for 950nm shows a good agreement for room temperature, but at high temperatures, the absorption decreases to an unexpected level. The second wavelength region around 1993nm has been tested successfully up to 2000 K. The results show good agreement in temperature and in water vapour mole fraction compared to former measurements at a McKenna burner. At 950 nm, errors in simulation and measurement lead not usable results. At 1993nm the mean error in temperature is less than 9.6%. The water vapour mole fraction measurements have an error of 8.6% in the best case.
Mayer T.,Institute of Space Systems |
Massuti-Basteller B.,Institute of Space Systems |
Herdrich G.,Institute of Space Systems |
Fasoulas S.,Institute of Space Systems
46th AIAA Thermophysics Conference | Year: 2016
The design, operation, and utilization of a tunable diode laser absorption spectroscopy setup for plasma wind tunnels experiments are described. For the setup a tunable infrared diode laser is used to measure the absorption at the oxygen triplet line at 844 nm. The transformation from time into frequency domain is accomplished by means of a Fabry Pérot interferometer. The setup is used to obtain radially resolved data of a plasma’s translational temperature and number density of the exited state. This is achieved by an inverse Abel transformation during the post-test analysis. The system is applied to two different plasma conditions. The first condition features a convergent nozzle, whereas a Laval nozzle with a smaller throat diameter is used in the second condition at a higher injector pressure. © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All right reserved.
Fulge H.,Institute of Space Systems |
Lohle S.,Institute of Space Systems |
Fasoulas S.,Institute of Space Systems
AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference | Year: 2014
In this paper measurements of temperature and mole fraction of water vapour by wavelength modulation spectroscopy (WMS) are presented. This work is focused on hypersonic combustion diagnostics using tunable diode laser absorption spectroscopy (TDLAS) at 1995 nm. The experiments are performed with a vertical cavity surface emitting laser diode (VCSEL) which is tunable by current and temperature. Water vapour temperature and mole fraction are determined by matching the second harmonic (2f) peak height normalized by its first harmonic (1f) value to a database of simulated signals based on the characteristics of the laser. The measurements have been performed on flat flames for proof of concept. Two different flame conditions are investigated and the results are compared with direct absorption measurements using the same equipment and the application of a calibration free WMS method to the acquired data as presented by Rieker et al. The investigated flames have been extensively analysed using coherent anti-stokes Raman scattering (CARS) measurements and equilibrium calculations by Prucker et al. The results using direct absorption agree fairly well with the published CARS data. The applied WMS methods agree well with each other, however, there is a significant discrepancy to the direct absorption measurements at the high temperature condition. Since the resulting values for the two different flame conditions with a nominally large temperature difference are close to each other, independent from the applied WMS method, it is concluded that further research of the WMS technology is required with respect to the applied transitions and its sensitivity to the investigated flows.