Unusual spacecraft materials

For particularly innovative space exploration missions, unusual requirements are levied on the structural components of the spacecraft. In many cases, the preferred solution is the utilization of unusual materials. This trend is forecast to continue. Several hypothetic examples are discussed

Femtosecond synchronously in-well pumped vertical-external-cavity surface-emitting laser

We demonstrate the first synchronously in-well pumped vertical-external-cavity surface-emitting laser (VECSEL). Depending on the cavity mismatch, laser pulses with a duration from 1 ps to 7 ps at a repetition rate of 76 MHz were generated directly from the laser at 860 nm. The application of extra-cavity pulse compression further shortened the pulse to a duration of 210 fs providing a peak power of 226 W

Morphology and Structure of Carbon Films Deposited at Varying Chamber Pressures

Depositing thin and thick films through different types of deposition units is a topic of great interest. In deposition chamber, each synthesis is carried out at some value of chamber pressure. In addition to different gases, photon energy also exists in the deposition chamber. Upon dissociation of methane by hot-filaments, the conversion rate of gaseous carbon atoms into graphite and diamond atoms varies largely at varying chamber pressures. Increase in the chamber pressure from 3.3 kPa to 14 kPa changes the morphology and structure of carbon films comprising tiny grains, grains and particles. The increase in chamber pressure upto 8.6 kPa increases the growth rate of a carbon film along with discernible features of grains and particles. For intermediate set chamber pressures, the conversion rate of gaseous carbon atoms into diamond state is high. At high set chamber pressures, gaseous carbon atoms converted into graphite state at high rate. However, film with low growth rate is deposited. At fixed input power, temperature of the hot-filaments changes due to contamination. So, collision rate of gases is also varied at varying chamber pressures. As a result, a different amount of atomic hydrogen is dissociated. Hence, a different amount of typical energy is etched. Atomic hydrogen etches the photon energy into typical energy shape like parabola, which is involved in the conversion of gaseous carbon atoms to graphite and diamond states. Graphite atoms bind under the same involved energy. Atomic hydrogen etches the photon energy and unused parabola shaped energy into typical energy shape like golf-stick, too, which is involved in the process of binding diamond atoms. So, this study sets new trends in the deposition of carbon films

Ablation debris control by means of closed thick film filtered water immersion

The performance of laser ablation generated debris control by means of open immersion techniques have been shown to be limited by flow surface ripple effects on the beam and the action of ablation plume pressure loss by splashing of the immersion fluid. To eradicate these issues a closed technique has been developed which ensured a controlled geometry for both the optical interfaces of the flowing liquid film. This had the action of preventing splashing, ensuring repeatable machining conditions and allowed for control of liquid flow velocity. To investigate the performance benefits of this closed immersion technique bisphenol A polycarbonate samples have been machined using filtered water at a number of flow velocities. The results demonstrate the efficacy of the closed immersion technique: a 93% decrease in debris is produced when machining under closed filtered water immersion; the average debris particle size becomes larger, with an equal proportion of small and medium sized debris being produced when laser machining under closed flowing filtered water immersion; large debris is shown to be displaced further by a given flow velocity than smaller debris, showing that the action of flow turbulence in the duct has more impact on smaller debris. Low flow velocities were found to be less effective at controlling the positional trend of deposition of laser ablation generated debris than high flow velocities; but, use of excessive flow velocities resulted in turbulence motivated deposition. This work is of interest to the laser micromachining community and may aide in the manufacture of 2.5D laser etched patterns covering large area wafers and could be applied to a range of wavelengths and laser types

Satellite power system: Concept development and evaluation program, reference system report

The Satellite Power System (SPS) Reference System is discussed and the technical and operational information required in support of environmental, socioeconomic, and comparative assessment studies are emphasized. The reference System concept features a gallium-aluminum-arsenide, and silicon solar cell options. Other aspects of an SPS are the construction of bases in space, launch and mission control bases on earth, and fleets of various transportation vehicles to support the construction and maintenance operations of the satellites

An optical tweezer actuated, nanoaperture-grid based optofluidic microscope implementation method

We report a novel grid based Optofluidic Microscope (OFM) method where a closely spaced 2D grid of nanoapertures (diameter = 100 nm, separation = 2.5 μm) provided patterned illumination. We achieved a one-to-one mapping of the light transmissions through the nanoapertures onto a high-speed CCD camera. By optically tweezing a targeted sample across the grid in a controlled fashion and recording the time varying light reception from the nanoapertures, we were able to generate high-resolution images of the sample. The achievable resolution limit of the prototype was ~ 110 nm (Sparrow’s criterion) under optimal conditions. We demonstrated the technique by imaging polystyrene beads and pollen spores