Modeling a Microgravity System for Ground Testing of Transformable Space Structures

The article develops a mathematical model of a microgravity system that simulates the conditions of weightlessness during ground tests of spacecraft. The microgravity system consists of vertical and horizontal control channels, providing a link opening in a twodimensional coordinate system. The channels are two-mass electromechanical systems with elastic connections. To simulate the microgravity system, mathematical models of these channels are obtained. To check the adequacy of the obtained models in Simulink Matlab, we simulated the opening of a link of a mechanical system. As a result of modeling, the permissible indicators of the accuracy of simulating weightlessness were obtained.

CFD Simulations and Experiments of a Submarine in Turn, Zigzag, and Surfacing Maneuvers

We present simulations and experiments of the generic submarine Joubert BB2 performing standard turn, zigzag, and surfacing maneuvers in calm water at depth. The free sailing experiments, performed at Maritime Research Institute Netherlands (MARIN), are unique in that they present an open dataset for the community to benchmark maneuvering prediction methodologies. Computations were performed with explicitly gridded sailplanes, tail planes, and propellers using a dynamic overset technique. This study analyzes a 20-degree turning maneuver with vertical control commanding the stern planes and a 20/20 zigzag maneuver with vertical control commanding both sail and stern planes, both of them at a nominal speed of 10 knots, and a 20-degree rise maneuver with horizontal control at 12 knots. The results show that computational fluid dynamics can predict well motions and speeds for free-sailing conditions, but controller commands are harder to replicate. Computations of the rise maneuver with surfacing compare well with experiments, including a crashback maneuver to stop the submarine.

Functionality and reliability of horizontal control net (Poland)

Horizontal control networks established with monuments are functional if the conditions related to the number of control points, their density, condition and stability of coordinates are met. For functionality defined in those terms, deterministic accuracy characteristics are of little use. The subject matter discussed herein includes the two key features of geodetic control points, i.e., usability and stability. Due to the varying properties of those variables and the impact of the operating time of the system, there is no alternative to reliability-based approach in developing the functionality model. The measures of functionality and the procedures of data acquisition for developing the model of the control network destruction process have been defined. The solution presented herein is relevant for geodetic practice, providing a standard procedure for defining the time frame and the scope of the control network upgrading. The identified destruction process model optimizes this task assuming critical states expressed by the functionality probability. The applied approach is an example of the reliability theory-based approach typical for engineering. The issue of simulating the destruction process is illustrated with the results of the tests of class 3 control networks conducted in Kielce and Lodz regions in Poland. As a result of the tests, the characteristic properties of the control network destruction process have been identified. It was also shown how the patterns of usability and accuracy of the geodetic control points are relevant on the stage of implementing investment project tasks.