Milli-Newton Thrust Stand for Hall Thruster
|關鍵字:||推力測試平台;毫牛頓;霍爾效應推進器;Thrust Stand;Milli-Newton;Hall Thruster|
Hall thruster, which is a type of the ion thruster, has been developed since 1960s. Since Hall thrusters have higher specific impulse (Isp) than any traditional propulsion systems, it has been used as the propulsion source of spacecraft and satellites for deep space missions and orbit transfers. Due to its high efficiency, a lot of space related researchers such as Europe and America pay much attention and spend a lot of efforts in its development. A typical Hall thruster consists of a chamber, magnetic coils, an anode and a cathode neutralizer. The working gas is introduced into the circular chamber from the anode and is ionized in the chamber. Electrons emitted from the cathode drift to anode by the axial electric field. Electrons are then confined by the E x B drift mechanism. The constraint produces a current called Hall current. Since electrons are confined in the chamber, the residence time of electrons in the chamber increases and ionization efficiency also improves. Since the mass of ions is much greater than electrons, it is hardly affected by the magnetic field. Ions are accelerated by the electrostatic force in the quasi-neutral plasma and exit the chamber to produce the thrust. The thrust level studied in this work is on the order of 20 mN which is about one-thousandth of the Hall thruster’s mass. In the present thesis, to measure the thrust produced by the Hall thruster, a torsional balance stand is designed, fabricated and tested. The balance arm is supported by two flexural pivots which are located at the center. The thruster and a counter weight is mounted at opposite ends respectively. As the thruster produces thrust, torque is produced which causes the arm to rotate. A linear displacement sensor is used to sense the displacement caused by the rotation. Then, a voice coil motor provides a force to compensate the rotation to move the arm back to the balance point. This is generally referred to as null balance operation. The stand is assembled and tested in the vacuum chamber of Plasma and Space Science Center (PSSC), National Cheng Kung University (NCKU). The test results show that the measurement range of the in-house stand is from 0 to 100 mN with a resolution of 0.2 mN.
|Appears in Collections:||Thesis|