Computational fluid dynamics study of droplet formation in a piezo inkjet printhead, with phase Doppler particle analyzer verification

This study involves the use of the CFD code, FLUENT, to predict the formation of droplets in a piezo inkjet printhead. Specifically, the velocity and diameter of the droplets formed is to be determined. There have been no solutions to such a problem using FLUENT and its capability to handle such a problem is assessed. Measurements of the actual droplet size and velocity are obtained using a Phase Doppler Particle Analyzer, PDPA. This has been established as a non-intrusive method of simultaneously measuring diameter and velocity of droplet distributions on the order of microns in size. These measurements were compared with the CFD solutions to determine the success of the CFD models. Three different CFD models were used, each differing in complexity. The most complex, full three-dimensional model revealed very good results. The diameters predicted by the CFD model average 47 um, which only differed by 15% from the measured values of the PDPA, which averaged 41 um. The velocity that was predicted by the CFD model was approximately 0.87 m/s, which was within 30% of the measured average of 0.68 m/s. These are acceptable results considering the complex nature of the problem and the lack of previous solutions. The deviations in the other CFD models were larger but results were still reasonable. This study has established the use of FLUENT CFD software as a potential tool in the study and design of piezo inkjet printing systems

Commercial Application of In-Space Assembly

In-Space assembly (ISA) expands the opportunities for cost effective emplacement of systems in space. Currently, spacecraft are launched into space and deploy into their operational configuration through a carefully choreographed sequence of operations. The deployment operation dictates the arrangement of the primary systems on the spacecraft, limiting the ability to take full advantage of launch vehicles volume and mass capability. ISA enables vastly different spacecraft architectures and emplacement scenarios to be achieved, including optimal launch configurations ranging from single launch and assembly to on-orbit aggregation of multiple launches at different orbital locations and times. The spacecraft can be visited at different orbital locations and times to effect expansion and maintenance of an operational capability. To date, the primary application of ISA has been in large programs funded by government organizations, such as the International Space Station. Recently, Space Systems Loral (SSL) led a study funded by the Defense Advanced Research Projects Agency (DARPA), called Dragonfly, to investigate the commercial applicability and economic advantages of ISA. In the study, it was shown that ISA enables SSL to double the capability of a commercial satellite system by taking advantage of alternate packaging approaches for the reflectors. The study included an ultra-light-weight robotic system, derived from Mars manipulator designs, to complete assembly of portions of the antenna system using a tool derived from DARPA orbital express and National Aeronautics and Space Administration (NASA) automated structural assembly experience. The mechanical connector that enables robotic ISA takes advantage of decades of development by NASA from the 1970's to 1980's during the Space Station Freedom program, the precursor to the ISS. The mechanical connector was originally designed for rapid astronaut assembly while also providing a high quality structural connection with linear load deflection response. The paper will discuss the business case for ISA, the general approach taken to exploit on-orbit assembly in the GEO communication satellite market, and the concept of operations associated with the ISA approach, thus laying the foundation for ISA to become an accepted operational approach for commercial in-space operations