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Kraetzig B.,University of Southern Queensland | Kraetzig B.,University of Stuttgart | Buttsworth D.R.,University of Southern Queensland | Zander F.,University of Queensland | And 2 more authors.
Journal of Thermophysics and Heat Transfer | Year: 2015

An electrical preheating technique applied to a carbon-based model in an impulse facility has previously demonstrated surface temperatures around 2500 K, but the measurement of heat flux at such elevated surface temperatures was not previously achieved. A technique for fast-response surface temperature measurement of an electrically preheated carbon-phenolic model using an indium gallium arsenide detector with in situ calibration via a visible/near-infrared spectrometer is assessed through application in a short-duration cold-flow hypersonic wind tunnel. The method is reliable: the scatter in temperatures determined from successive acquisitions of the spectrometer data had a standard deviation of 3 K at a mean temperature of about 1500 K; the standard deviation of the Indium gallium arsenide detector results from the visible/near-infrared spectrometer data was 11 K at a temperature of about 1100 K after the termination of the hypersonic flow. The surface temperature history from the Indium gallium arsenide detector was analyzed using a one-dimensional transient heat conduction model to deduce the surface heat flux. Good agreement with an engineering correlation for stagnation point heat flux is demonstrated; however, uncertainties are large (±33%), as the thermal properties of the particular carbon-phenolic material were not available. The method is suitable for application in impulse facilities, but the effusivity (√ρ ck) for the heat shield material will need to be accurately defined for reliable deduction of surface heat flux. Copyright © 2014 by the American Institute of Aeronautics and Astronautics, Inc. Source

Blott R.,Space Enterprise Partnerships | Koppel C.,KopooS Consulting Ind | Herdrich G.,Institute of Space Systems
Proceedings of the International Astronautical Congress, IAC | Year: 2012

There have been a number of studies of fission nuclear power generation for space applications over the past decade. Mostly they focus on technical development required or perceived achievable. The EC FP7 Disruptive Technologies for Power and Propulsion (DiPOP) Study is investigating the wider issues. Which applications might attract the investment to develop space fission nuclear power generation? What expertise and infrastructure must be developed and what existing capabilities may be relevant? Which organisations might invest in developing the capability and for what reasons? What is required for public acceptance, safety and sustainability of space fission nuclear power? At the request of the EC the DiPOP project has arranged for an international Advisory Board of experts to give guidance and review progress. The European Advisory Board member is from the Commissariat a Tenergie atomique et aux energies alternatives (CEA). The Russian and United States Advisory Board members have first-hand experience of space fission nuclear power projects. A Fission Nuclear Power Generation Draft has been created with the guidance of the Advisory Board. It draws on past and current projects and studies and identifies a programme of work to fully investigate the issues. Results from research during the summer of 2012 will be used to update the Roadmap to a final version for review in September and publication in October. This paper will give a preliminary presentation of the findings.©2012 by the International Astronautical Federation. Source

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

Massuti-Ballester B.,Institute of Space Systems | Pidan S.,Institute of Space Systems | Herdrich G.,Institute of Space Systems | Fertig M.,German Aerospace Center
Advances in Space Research | Year: 2015

At the Institute of Space Systems (IRS), experiments have been performed using the high enthalpy, inductively heated plasma generator (IPG) in plasma wind tunnel 3 (PWK3), in order to assess the catalytic behaviour of different materials. Utilising the Upwind Relaxation Algorithm for Non-equilibrium Flows of the University of Stuttgart (URANUS), a methodology for determining catalytic efficiencies by obtaining atomic recombination probabilities γ for high temperature materials, has been developed. This method eliminates the inherent uncertainties produced when using catalytic properties of previously tested materials to infer those of new materials. In this work, eight different candidates for the Thermal Protection System (TPS) of an entry vehicle have been studied, of which six are ceramic materials and the other two are metallic alloys. Thermochemical properties of these specimens are given for surface temperatures between 1000 and 2000 K in pure oxygen and pure nitrogen plasmas. The high enthalpies and relatively low pressure conditions in which these material samples have been tested in PWK3 are relevant for entry applications from Low Earth Orbit (LEO). © 2015 COSPAR. Source

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. Source

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