Atomic oxygen effects on boron nitride and silicon nitride: A comparison of ground based and space flight data
The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) were evaluated in a low Earth orbit (LEO) flight experiment and in a ground based simulation facility. In both the inflight and ground based experiments, these materials were coated on thin (approx. 250A) silver films, and the electrical resistance of the silver was measured in situ to detect any penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the inflight and ground based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the inflight or ground based experiments. The ground based results show good qualitative correlation with the LEO flight results, indicating that ground based facilities such as the one at Los Alamos National Lab can reproduce space flight data from LEO.
Results from the Space Technology Research Vehicle 1a Atomic Oxygen Experiment
Anexperimenttomakeinsitumeasurementsofthermosphericatomicoxygene uxesandtheireffectonsomecommonspacecraftmaterialshasbeene owninorbitonboardtheSpaceTechnology ResearchVehicle1amicrosatellite. The results from active sensors were based on resistance measurements of silver e lms and were interpreted relative to space simulations made in a ground-based pulsed laser atomic oxygen source. It was concluded that silver resistance sensors can be used to measure atomic oxygen e uxes but are best suited to low e ux environments, e.g., <10 14 atoms cm i 2 s i 1 . Some silver sensors were overlaid with thin coatings to measure the erosion resistance of the coating materials. It was found that erosion rates wereaffected by the structure of the materials; this structure must therefore be taken into account in experiment and spacecraft design.
"Flying Triangulation" - a new optical 3D sensor enabling the acquisition of surfaces by freehand motion
In order to obtain complete 3D surface information of an object it is often necessary to acquire many partial 3D views. For this purpose, the sensor has to be moved (e.g. for the acquisition of sculptures or rooms). Further, in many cases a motion of the object relative to the sensor is unintended but inevitable (e.g. for medical applications such as intraoral measurements of teeth). Nearly all existing optical 3D sensors either lack an easy handling or require a standstill during the acquisition of a single partial 3D view, since usually multiple camera shots have to be taken for this purpose. This makes such measurements elaborate or even impossible.