Journal of Space Science and Technology
Year:2019 | Volume:12 | Issue:2 (39)|Papers Count:6

corona discharge which had been considered undesired before, has become popular for different uses in the past decades; including space thrusters. The basic corona discharge has a simple setup including two electrodes with unequal cross-sections; one of which connected to a high voltage and the other connected to ground or opposite voltage. By changing the number of electrodes, the efficiency of corona discharge can be improved. In this paper, number of electrodes have been changed from 2 to 3 in order to study an electrohydrodynamic thruster. Flow characteristics have been studied by solving the electrostatics and Navier-Stokes equations by finite element method (FEM). The results show that with increasing the number of cathodes the thrust, electric current and thrust efficiency will also increase. In similar condition and geometry, maximum produced velocity resulted by applying any electric potential to anode, increases by about 30% in comparison with one-cathode setup.

the effect of the internal geometry of the injector of a low-thrust monopropellant thruster on the characteristics of the outlet liquid sheet, such as the liquid sheet thickness, the spray cone angle, the average output velocity, and its mass flow rate, have been studied. For this purpose, simulation of the internal flow based on the computational fluid dynamics was performed to predict the output flow characteristics, then parametric studies were conducted to investigate the effect of geometry. In order to extract a predictive model for the preliminary design of the injector, a neural fuzzy network model was used. Using this model, the results of parametric analyzes were used to obtain a geometric specification without geometric modeling and computational fluid dynamics analysis or the use of initial design methods. The purpose of the implementation of the neural network model is to obtain an estimate of the internal geometry of the injector by entering the desired macroscopic characteristics of the output flow.

In this research, the 3D grain burnback with quasi-one-dimensional internal ballistic in a solid rocket motor is simulated using the Level set theory and the utilization of Sections method, while achieving high accuracy in the simulation of green's post-back analysis time can also be significantly reduced. By using Section method, 3D grains are divided to many 2D grain, then 2D Level set is utilized to analyse grain burnback. Finally, the burning port of 3D grains are calculated by means of Interpolation. Also, to predict the internal pressure of the motor and the burning rate, a numerical code is written and coupled with grain burnback programme.

In this paper, design and simulation of a deployment and release mechanism of a communication satellite antenna are described. Because of the simplicity and reliability of the system, a torsion spring is used to excite the antenna. Dynamic simulation is performed by Adams Software and the appropriate spring and damper are selected for the mechanism. Also, a thermal cutter mechanism is used for the release mechanism of the antenna that shows a good performance in the tests. Also, a finite element analysis is performed to ensure the structural strength of the mechanism by Nastran-Patran Software. According to the results of the tests and simulations performed on the system, one can say that this mechanism is a simple, functional and reliable mechanism and can be done well the assigned duties in accordance with the requirements of the employer and the ECSS standard.

In this paper, the design and implementation of hardware-in-the-loop (HIL) test-bed for spacecraft attitude control are presented with respect to the practical consideration. This test-bed includes an air bearing 3-DOF table, Helmholtz coil, sun simulator, orbit simulator, reaction wheels and torqrods as actuators, gyro, GPS, AHRS, magnetometer, and processing board. In addition, online monitoring of attitude and orbit position in LabVIEW and Celestia software, data telemetry, battery package and power distribution board are developed in this case. Using this test-bed, different operational modes are evaluated and verified for satellite attitude control. The experimental results of damping mode show that the capability of decreasing the angular velocity to the desired value (0. 3 deg/s). Moreover, a torque simulator to apply the disturbances and test of propulsion scenarios, online telemetry with ground station, near-optimal design of Helmholtz coil are the advantages of this test-bed.

The purpose of this study is to investigate the effect of six weeks of HIIT under simulated microgravity conditions on morphological changes of radial nerve myelin sheath in male rats. In the present study, 24 male wistar rats were randomly selected and divided into four groups including: TS (training during suspension: n=6), CS (suspension: n=6), T (training: n=6), C (control: n=6). The training groups run on treadmill for six weeks (five days a week). 24 hours after the last training session, animals were prepared for tissue samples. At the end of the experiment, changes in myelin sheath were measured by Luxol fast blue. obtaining results showed that the percentage of changes in myelin sheath in HIIT group under simulated microgravity (p≤ 0. 001) was higher than other groups, significantly (30/27+5/27). Based on the results, HIIT under simulated microgravity conditions affected on changes in myelin sheath. Therefore, it can play an effective role in the improvement of clinical status of neurological patients and decrease side effects in Astronauts.