Martian soils are critically important for understanding the history of Mars, past potentially habitable environments, returned samples, and future human exploration. This paper examines soil crusts on the floor of Jezero crater encountered during initial phases of the Mars 2020 mission. Soil surface crusts have been observed on Mars at other locations, starting with the two Viking Lander missions. Rover observations show that soil crusts are also common across the floor of Jezero crater, revealed in 45 of 101 locations where rover wheels disturbed the soil surface, 2 out of 7 helicopter flights that crossed the wheel tracks, and 4 of 8 abrasion/drilling sites. Most soils measured by the SuperCam laser-induced breakdown spectroscopy (LIBS) instrument show high hydrogen content at the surface, and fine-grained soils also show a visible/near infrared (VISIR) 1.9 µm H2O absorption feature. The Planetary Instrument for X-ray Lithochemistry (PIXL) and SuperCam observations suggest the presence of salts at the surface of rocks and soils. The correlation of S and Cl contents with H contents in SuperCam LIBS measurements suggests that the salts present are likely hydrated. On the “Naltsos” target, magnesium and sulfur are correlated in PIXL measurements, and Mg is tightly correlated with H at the SuperCam points, suggesting hydrated Mg-sulfates. Mars Environmental Dynamics Analyzer (MEDA) observations indicate possible frost events and potential changes in the hydration of Mg-sulfate salts. Jezero crater soil crusts may therefore form by salts that are hydrated by changes in relative humidity and frost events, cementing the soil surface together.
The Perseverance rover landed at Jezero crater, Mars, on 18 February 2021, with a payload of scientific instruments to examine Mars’ past habitability, look for signs of past life, and process samples for future return to Earth. The instrument payload includes the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) deep ultraviolet Raman and fluorescence imaging spectrometer designed to detect, characterize, and map the presence of organics and minerals on the Martian surface. Operation and engineering constraints sometimes result in the acquisition of spectra with features near the detection limit. It is therefore important to separate instrumental (background) spectral components and spectral components inherent to Martian surface materials. For SHERLOC, the instrumental background is assessed by collecting spectra in the stowed-arm configuration where the instrument is pointed at the Martian nighttime sky with no surface sample present in its optical path. These measurements reveal weak Raman and fluorescence background spectral signatures as well as charged-coupled device pixels prone to erroneous intensity spikes separate from cosmic rays. We quantitatively describe these features and provide a subtraction procedure to remove the spectral background from surface spectra. By identifying and accounting for the SHERLOC Raman background features within the median Raman spectra of Martian target scans, we find that the undefined silicate spectral feature interpreted to be either amorphous silicate or plagioclase feldspar is ubiquitously found in every Mars target Raman scan collected through Sol 751.
The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.
Core shear cracking induced by impact on sandwich panels is a detrimental failure mode causing severe loss of structural performance. This paper derives analytical expressions for initiation of skin rupture and core shear cracking during impact on sandwich panels with foam cores. The criteria are successfully validated by comparison with experimental results for a range of thicknesses of skins and cores in panels with carbon/epoxy NCF skins and a Rohacell foam core.
This paper examines analytical models for hail impact on composite laminates and compares the predictions with finite element simulations and experiments. The crushing of the ice results in a distributed load and a much higher delamination threshold load than for impact by hard objects. Furthermore, prediction of the impact load by merely considering the mass flow of ice particles results in too low loads and a response in disagreement with experiments. The pressure acting on the impacted plate is fairly uniform within the contact area, but initial through-thickness waves during the first moments of the impact cause much higher stresses than the quasi-static values assumed in the analytical models. Hence the finite element models predict a different load history, with a much steeper initial increase in the contact load.
Flyg- och lufttransporter genomgår stora förändringar, drivet av bland annat teknikutveckling och en hållbarhetssträvan där negativ påverkan av flyg och luftfart ämnas minska. Med nya typer av farkoster och drivmedel, en större grad automatisering i luften och på marken, samt förändringar i infrastruktur kring flygplatser ritas landskapet för luftfarten om. För aktörer inom luftfartsområdet är det viktigt att få en bild av de förändringar som sker idag, vilka kommer att forma framtidens luftfart, och även skapa en förståelse för hur man bör agera i ljuset av framväxande trender.
Inom omvärldsanalysen ser vi trender som kommer att påverka flyg och luftfartsområdet inom sex temaområden som utgör de övergripande avsnitten i rapporten.
Rapporten avslutas med en sammanställning av forskningsbehov och pågående forskningsprojekt inom luftfartsområdet i Sverige och Europa.
Omvärldsanalysen är framtagen på uppdrag av Trafikverket, för att ge underlag i prioriteringar av forskningsmedel framgent inom luftfartsområdet, och ge bättre förutsättningar för luftfarten att möta omvärldens krav på säkra, effektiva, robusta, tillgängliga och hållbara transporter.