This paper summarises the first outcomes of the space demonstration mission of the ARCHES project which could have been performed this year from 13 june until 10 july on Italy's Mt. Etna in Sicily. After the secon...
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This paper was initially intended to report on the outcome of the twice postponed demonstration mission of the ARCHES project. Due to the global COVID pandemic, it has been postponed from 2020, then 2021, to 2022. Nev...
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The German Aerospace Center bundles its railway research in the long-term project “Next Generation Train” (NGT). The NGT is a high speed train concept in light-weight design and double-deck configuration. To reduce ...
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The German Aerospace Center bundles its railway research in the long-term project “Next Generation Train” (NGT). The NGT is a high speed train concept in light-weight design and double-deck configuration. To reduce wheel and rail wear and to enhance the passenger capacity, a mechatronic running gear with independently rotating wheels (IRW) is designed. This configuration requires an advanced control of the lateral dynamics in order to fully exploit the potential in minimizing wear and noise. In terms of a model-based control design, the controller performance highly depends on the estimated lateral position of the running gear relative to the track. In a practical environment it is difficult to directly measure this displacement of the wheel-pair. Therefore this article deals with the question which sensor configuration enables an appropriate estimation of the lateral displacement and is suitable for observer design. Hence, an observability analysis and an observer synthesis to estimate the lateral position for the nonlinear system of the 1:5 scaled hardware running gear is carried out. For validation purposes three estimators are implemented at the real-time environment of the testbed and the estimation errors of the observer configurations are compared.
The paper develops an algorithm for solving the two-dimensional nonlinear degenerate parabolic heat conduction equation with a source depending on required function, with a specified law of heat wave front motion. The...
The paper develops an algorithm for solving the two-dimensional nonlinear degenerate parabolic heat conduction equation with a source depending on required function, with a specified law of heat wave front motion. The algorithm based on the boundary element method is implemented in the form of a program. To verify it, we use exact solutions the construction of which is reducible to solving a Cauchy problem for ordinary differential equations with a singularity before the highest derivative. The solutions to the Cauchy problem are constructed in the form of power series with recurrently computed coefficients (with a proof of the statement providing its convergence) and by the boundary element method.
20 years after the successful ground deployment test of a (20 m)2 solar sail at DLR Cologne, and in the light of the upcoming U.S. NEAscout mission, we provide an overview of the progress made since in our mission and...
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The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the targe...
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The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3–5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5-6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure - as was determined through an extensive, almost two years long campaign - was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign – described in detail in this paper – the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole finally reached a depth of 40 cm, bringing the mole body 1–2 cm below the surface. It reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the hull. The penetration record of the mole and its thermal sensors were used to measure thermal and mechanical soil parameters such as the penetration resistance of the duricrust of 0.5 - 1.2 MPa and a penetration resistance of a deeper layer (> 30 cm depth) of 5.3 MPa. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 4 - 25 kPa depending on the internal friction angle of the duricrust. Pushing the scoop with its blade into the surface and chopping off a piece of duricrust provided another estimate of the cohesion of 5.8 kPa. The hammerings of the mole were recorded by the seismometer SEIS and the signals could be used to derive a P-wave velocity of 114+40−19 m/s and a S-wave velocity of 60+10−7 m/s (Brinkman et al., 2021) representative of
The problem of constructing solutions to the nonlinear heat equation with power nonlinearity is considered. The solutions have the form of a traveling wave and simulate the propagation of disturbances over a cold back...
The problem of constructing solutions to the nonlinear heat equation with power nonlinearity is considered. The solutions have the form of a traveling wave and simulate the propagation of disturbances over a cold background with a finite velocity. It is shown that the construction can be reduced to the Cauchy problem for an ordinary second- order differential equation with a singularity multiplying the highest derivative. Its solutions are constructed using the boundary element method based on the dual reciprocity method. A computational experiment is carried out. The results are compared with the solutions of the same problems by the power series method. The calculations have shown the correctness of the developed boundary element algorithm and its advantage compared to the power series segments and the step-by-step method previously proposed by the authors.
The exploration of small solar system bodies started with fast fly-bys of opportunity on the sidelines of missions to the planets. The tiny new worlds seen turned out to be so intriguing and different from all else (a...
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The exploration of small solar system bodies started with fast fly-bys of opportunity on the sidelines of missions to the planets. The tiny new worlds seen turned out to be so intriguing and different from all else (and each other) that dedicated sample-return and in-situ analysis missions were developed and launched. Through these, highly efficient low-thrust propulsion expanded from commercial use into mainstream and flagship science missions, there in combination with gravity assists propulsion. In parallel, the growth of small spacecraft solutions accelerated in numbers as well as individual spacecraft capabilities. The on-going missions OSIRIS-REX (NASA) or HAYABUSA2 (JAXA) with its landers MINERVA-II and MASCOT, and the upcoming NEASCOUT mission are examples of this synergy of trends. The continuation of these and other related devlopments towards a propellant-less and highly efficient class of spacecraft for solar system exploration emerges in the form of small spacecraft solar sails designed for carefree handling and equipped with carried landers and application modules. These address the needs of all asteroid user communities - planetary science, planetary defence, and in-situ resource utilization - as well as other fields of solar system science and applications such as space weather warning and solar observations. Already the DLR-ESTEC GOSSAMER Roadmap for Solar Sailing initiated studies of missions uniquely feasible with solar sails such as Displaced L1 (DL1) space weather advance warning and monitoring and Solar Polar Orbiter (SPO) delivery, which demonstrate the capabilities of near-term solar sails to reach any kind of orbit in the inner solar system. This enables Multiple Near-Earth Asteroid (NEA) rendezvous missions (MNR), from Earth-coorbital to extremely inclined and even retrograde target orbits. For these mission types using separable payloads, design concepts can be derived from the separable Boom Sail Deployment Units characteristic of DLR GOS
The objective of this paper is to present frequency response function (FRF) based updating as a method for matching the finite element (FE) model of a laser spot welded structure with a physical test structure. The FE...
The objective of this paper is to present frequency response function (FRF) based updating as a method for matching the finite element (FE) model of a laser spot welded structure with a physical test structure. The FE model of the welded structure was developed using CQUAD4 and CWELD element connectors, and NASTRAN was used to calculate the natural frequencies, mode shapes and FRF. Minimization of the discrepancies between the finite element and experimental FRFs was carried out using the exceptional numerical capability of NASTRAN Sol 200. The experimental work was performed under free-free boundary conditions using LMS SCADAS. Avast improvement in the finite element FRF was achieved using the frequency response function (FRF) based updating with two different objective functions proposed.
A nonlinear parabolic heat conduction equation with a source is discussed, for which solutions of the heat wave propagating against a cold background at a finite velocity are studied. A new theorem of the existence an...
A nonlinear parabolic heat conduction equation with a source is discussed, for which solutions of the heat wave propagating against a cold background at a finite velocity are studied. A new theorem of the existence and uniqueness of heat waves is proved. A particular case is studied in detail, when the heat wave is invariant and its construction reduces to solving an ordinary differential equation. For the numerical construction of invariant heat waves, an algorithm based on the boundary element method is proposed. Test examples are solved.
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