Development of a Marslander with crushable shock absorber by virtual and experimental testing

Since the beginning of space exploration, probes have been sent to other planets or moons with the associated challenge of landing on these bodies. For a soft landing several damping methods like landing legs or airbags have been used. A new and potentially less complex and lighter way to reduce the shock loads at touchdown is the use of a crushable shield underneath the lander platform. This crushable shield could be made for example out of an energy absorbing materials like an aluminum honeycomb core with a High Performance Polyethylene cover sheet. The design is particularly advantageous since no moving parts nor other mechanisms are required, thus making the shield very robust and fail safe. The only mission that is currently planned to use this technique is the ESA-mission “ExoMars” which is planned to start in 2016. The development of such a crushable shock absorber implies and requires assessment of materials, manufacturing processes, the setup of a numerical simulation and the experimental validation in a test lab. In an independent research project (Marslander1) a representative engineering mockup of the landing platform has been build and tested at the Landing & Mobility Test Facility (LAMA) to support the numerical simulation model with experimental data. The simulations are based on the explicit Finite Element Method, which discretizes the structure into a defined number of elements, such that each element is assigned a set of equations describing the material properties and applied loads. The goal is to generate a simplified but still accurate model to predict landing scenarios by running Monte Carlo simulations. Results of the above stated development and testing processes will be presented and discussed in this paper

Deployment dynamics analysis of CALLISTO’s approach and landing system

Prior to landing of reusable space transportation systems, the vehicle’s landing legs needs to be fully deployed to enable a safe landing and further re-use of the space vehicle. During that phase the deployment system has to overcome harsh and challenging environmental conditions. In this study, a numerical simulator is developed in order to investigate these influences on the landing leg deployment dynamics. By means of an extensive aerodynamic database and a broad approach flight domain, the influence of aerodynamics, exhaust plume, and vehicle’s attitude on the deployment dynamics is analyzed. This study shows on the example of the first stage demonstrator CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), that thrust level, vehicle attitude, and the deployment system parameters affect the deployment performance

Технико-экономические характеристики работы твердотопливной котельной в условиях посезонного изменения типа и качества сжигаемого топлива

В ВКР проведена численно-аналитическая оценка технико-экономических характеристик работы твердотопливной котельной при использовании разносортного типа топлива. В качестве сырьевой базы рассмотрены уголь, продукция и отходы лесопромышленного комплекса, а также углеродосодержащий шлак. В том числе отражены достоинства и недостатки использования того или иного топлива на надежностные характеристики работы топливосжигающего оборудования.In WRC the numerical and analytical assessment of technical and economic characteristics of work of a solid-fuel boiler house is carried out at use of different-grade type of fuel. As a raw material base, coal, products and wastes of the timber industry, as well as carbon-containing slag are considered. In particular, the advantages and disadvantages of using a particular fuel for the reliability characteristics of the fuel burning equipment are reflected

Locally critical quantum phase transitions in strongly correlated metals

When a metal undergoes a continuous quantum phase transition, non-Fermi liquid behaviour arises near the critical point. It is standard to assume that all low-energy degrees of freedom induced by quantum criticality are spatially extended, corresponding to long-wavelength fluctuations of the order parameter. However, this picture has been contradicted by recent experiments on a prototype system: heavy fermion metals at a zero-temperature magnetic transition. In particular, neutron scattering from CeCu$_{6-x}$Au$_x$ has revealed anomalous dynamics at atomic length scales, leading to much debate as to the fate of the local moments in the quantum-critical regime. Here we report our theoretical finding of a locally critical quantum phase transition in a model of heavy fermions. The dynamics at the critical point are in agreement with experiment. We also argue that local criticality is a phenomenon of general relevance to strongly correlated metals, including doped Mott insulators.Comment: 20 pages, 3 figures; extended version, to appear in Natur

Reusable Structures for CALLISTO

In order to make access to space more affordable for both scientific and commercial activities the German Aerospace Center (DLR), the Japanese Aerospace Exploration Agency (JAXA), and the French National Centre for Space Studies (CNES) joined in a trilateral agreement to develop and demonstrate the technologies that will be needed for future reusable launch vehicles. In the joined project CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations) a demonstrator for a reusable vertical take-off, vertical landing rocket, acting as first stage, is developed and built. As long-term objective this project aims at paving the way to develop a rocket that can be fully reused, and the joint efforts of the three agencies will culminate in a demonstrator that will perform its first flights from the Kourou Space Center, in French Guyana. Having regard to the aspect of reusable structures, the development of design represents a special challenge since the components have to withstand a variety of complex manoeuvres for multiple times. Additionally, this technical complexity leads to limitations in size and mass which must be observed during the design process. The structures have to be studied very individually to meet all the requirements for reaching optimal performance during ascent, return and landing. This paper focuses on the design solutions for CALLISTO’s fairing, the aerodynamic surfaces and the approach & landing system with respect to their specific sizing load case during the mission. The challenging concept of deployable aerodynamic surfaces is especially highlighted as the deployment causes a significant transformation of the vehicles outer shape and consequently has direct impact on the trajectory. This also applies to the stowable landing gear that has been one main design challenge in the frame of CALLISTO

Local fluctuations in quantum critical metals

We show that spatially local, yet low-energy, fluctuations can play an essential role in the physics of strongly correlated electron systems tuned to a quantum critical point. A detailed microscopic analysis of the Kondo lattice model is carried out within an extended dynamical mean-field approach. The correlation functions for the lattice model are calculated through a self-consistent Bose-Fermi Kondo problem, in which a local moment is coupled both to a fermionic bath and to a bosonic bath (a fluctuating magnetic field). A renormalization-group treatment of this impurity problem--perturbative in $\epsilon=1-\gamma$, where $\gamma$ is an exponent characterizing the spectrum of the bosonic bath--shows that competition between the two couplings can drive the local-moment fluctuations critical. As a result, two distinct types of quantum critical point emerge in the Kondo lattice, one being of the usual spin-density-wave type, the other ``locally critical.'' Near the locally critical point, the dynamical spin susceptibility exhibits $\omega/T$ scaling with a fractional exponent. While the spin-density-wave critical point is Gaussian, the locally critical point is an interacting fixed point at which long-wavelength and spatially local critical modes coexist. A Ginzburg-Landau description for the locally critical point is discussed. It is argued that these results are robust, that local criticality provides a natural description of the quantum critical behavior seen in a number of heavy-fermion metals, and that this picture may also be relevant to other strongly correlated metals.Comment: 20 pages, 12 figures; typos in figure 3 and in the main text corrected, version as publishe

Patient with neuromyelitis optica and inflammatory demyelinating lesions comprising whole spinal cord from C2 level till conus: case report

BACKGROUND: Neuromyelitis optica (NMO) is an idiopathic, severe, inflammatory demyelinating disease of the central nervous system, that causes severe optic neuritis and myelitis attacks. Early discrimination between multiple sclerosis (MS) and NMO is important, as optimum treatment for both diseases may differ considerably. ----- CASE PRESENTATION: We report a case of a patient who initially presented as longitudinally extensive transverse myelitis (LETM), having spastic upper extremities diparesis and spastic paraplegia, C2/C3 sensory level and urinary incontinence, as well as extensive inflammatory spinal cord lesions from C2 level to conus. After 5 months the patient had another attack of transverse myelitis, had electrophysiological findings consistent with optic neuritis, was seropositive for NMO-IgG (aquaporin-4 IgG) and thus fulfilled NMO diagnostic criteria. Following treatment of disease attacks with pulse corticosteroid therapy and intravenous immunoglobulins, we included oral azathioprine in a combination with oral prednisone in the therapy. Since there was no significant clinical improvement, we decided to use cyclophosphamide therapy, which resulted in good clinical improvement and gradual decrease of cord swelling. ----- CONCLUSION: In this NMO case report we wanted to emphasize the extensiveness of inflammatory spinal cord changes in our patient, from C2 level to conus. In the conclusion it is important to say that accurate, early diagnosis and distinction from MS is critical to facilitate initiation of immunosuppressive therapy for attack prevention