The evolution of the solar system and the origin of life remain some of the most intriguing questions for humankind. Addressing these questions experimentally is challenging due to the difficulty of mimicking environmental conditions representative for Early Earth and/or space conditions in general in ground-based laboratories. Performing experiments directly in space offers the great chance to overcome some of these obstacles and to possibly find answers to these questions. Exposure platforms in Low Earth Orbit (LEO) with the possibility for long-duration solar exposure are ideal for investigating the effects of solar and cosmic radiation on various biological and non-biological samples. Up to now, the Exobiology and space science research community has successfully made use of the International Space Station (ISS) via the EXPOSE facility to expose samples to the space environment with subsequent analyses after return to Earth. The emerging small and nanosatellite market represents another opportunity for astrobiology research as proven by the robotic O/OREOS mission, where samples were monitored in-situ, i.e. in Earth orbit. In this framework, the European Space Agency is developing a novel Exobiology facility outside the ISS. The new platform, which can host up to four different experiments, will combine the advantages of the ISS (long-term exposure, sample return capability) with near-real-time in-situ monitoring of the chemical/biological evolution in space. In particular, ultraviolet-visible (UV-Vis) and infrared (IR) spectroscopy were considered as key non-invasive methods to analyse the samples in situ. Changes in the absorption spectra of the samples developing over time will reveal the chemical consequences of exposure to solar radiation. Simultaneously, spectroscopy provides information on the growth rate or metabolic activities of biological cultures. The first quartet of experiments to be performed on-board consists of IceCold, OREOcube and Exocube (dual payload consisting of ExocubeChem and ExocubeBio). To prepare for the development of the Exobiology facility, ground units of the UV-Vis and IR spectrometers were studied, manufactured and tested as precursors of the flight units. The activity led to a modular in-situ spectroscopy platform able to perform different measurements (e.g. absorbance, optical density, fluorescence measurements) at the same time on different samples. We describe here the main features of the ground model platform, the verification steps, results and approach followed in the customization of commercial-off-the-shelf (COTS) modules to make them suitable for the space environment. The environmental tests included random and shock vibration, thermal vacuum cycles in the range −20°C to +40°C and irradiation of the components with a total dose of 1800 rad (18 Gy). The results of the test campaign consolidated the selection of the optical devices for the Exobiology Facility. The spectroscopic performance of the optical layout was tested and benchmarked in comparison with state-of-...
This paper describes the activities conducted in the development of the electron beam welding (EBW) process for two cold plates, designed by Thales Alenia Space and made from AA 6061 T651. This special welding technology is made necessary by the need to minimize welding-induced deformations. Cold plates are the main components of the mice drawer system (MDS) payload cooling system. The development and manufacture of this component, funded by Italian Space Agency and Thales Alenia Space, as the industrial supplier, will make it possible to conduct several space research programmes. The MDS is necessary to maintain the temperatures required, both for the electronic control units and for the mouse habitat (cooling of the recirculation air and drinking water for the guinea pigs), during shuttle transportation and during conducting experiments onboard the International Space Station (ISS). The cold plates are made by assembling two aluminium plates of variable thickness with fins, worked by electroerosion, enclosing a coil made from AISI 316 for the water cooling system. The weld geometry may be likened to a butt joint with partial penetration along the 1700 mm perimeter of the plates. The oversize of the assembled component after welding (488 £ 356 mm plates) was only 0.5 mm, considering a planar tolerance for the finished component of 0.05 mm. The objective is thus to minimize distortion and at the same time maximize penetration depth so as to reduce weld stresses. The main problems encountered have been in relation to defining weld parameters in order to eliminate porosity and eliminate problems associated with 'flash' (interruption of the electron beam, and hence welding) as seen in the treated aluminium alloy. Destructive analysis and NDT for qualification of the WPS have been aimed at evaluating weld efficiency and permissible stress. Draw tests, conducted on partial penetration test joints with a penetration depth of 5 0/þ 1 mm, have shown a linear strength of approximately 1 kN/mm, corresponding to approximately 154 MPa for the sections analysed. This strength is markedly superior than the stresses calculated by FEM analysis, also in the case of overloads arising under emergency conditions (85.2 MPa). Using the final parameters, summarized in WPS-EBW (2006)001, two cold plates have been welded, soon to be delivered to the ISS.
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