Measurement of plasma momentum exerted on target by a small helicon plasma thruster and comparison with direct thrust measurement

Charles

Boswell

et al. 2018

Sci Rep

Self Cite

Space debris removal from Earth orbit by using a satellite is an emergent technological challenge for sustainable human activities in space. In order to de-orbit debris it is necessary to impart a force to decelerate it, resulting in its atmospheric re-entry. A satellite using an energetic plasma beam directed at the debris will need to eject plasma in the opposite direction in a controlled manner in order to maintain a constant distance between it and the debris during the deorbiting mission. By employing a magnetic nozzle plasma thruster having two open source exits, bi-directional plasma ejection can be achieved using a single electric propulsion device. Both the forces exerted on the thruster and the target plate simulating the debris are simultaneously measured in a laboratory space simulation chamber showing that a force decelerating the debris and a zero net force on the thruster can be successfully obtained. These two forces can be individually controlled by external electrical parameters, resulting in the ability to switch the acceleration and deceleration modes of the satellite and the debris removal mode using a single electric propulsion device.

Section: Resultsmentioning

confidence: 99%

Demonstrating a new technology for space debris removal using a bi-directional plasma thruster

Charles

Boswell

et al. 2018

Sci Rep

Self Cite

“…7. By sweeping the calibration coil current and measuring the displacement by the LED sensor and the force by the load cell, the calibration coefficient can be obtained for each direction as demonstrated previously 51 . Figure 8 shows the measured relations between the force and the displacement sensor signal in the (a) radial (V r -F rc ) and (b) axial (V z -F zc ) directions, where the signals include some oscillating components of the pendulum.…”

Section: Methodsmentioning

confidence: 99%

Spatially- and vector-resolved momentum flux lost to a wall in a magnetic nozzle rf plasma thruster

Sugawara

Andõ

2020

Sci Rep

Self Cite

Most of the artificial low-pressure plasmas contact with physical walls in laboratories; the plasma loss at the wall significantly affects the plasma device performance, e.g., an electric propulsion device. Near the surface of the wall, ions are spontaneously accelerated by a sheath and deliver their momentum and energy to the wall, while most of the electrons are reflected there. The momentum flux of the ions is a vector field, i.e., having both the radial and axial components even if the azimuthal components are neglected in a cylindrical system. Here the spatially-and vector-resolved measurement of the momentum flux near the cylindrical source wall of a magnetic nozzle radiofrequency (rf) plasma thruster configuration is successfully demonstrated by using a momentum vector measurement instrument. The results experimentally identify the spatial profile of a non-negligible axial momentum flux to the wall, while the radially accelerated ions seem to be responsible for the energy loss to the wall. The spatial profiles of the radial and axial momentum fluxes and the energy lost to the wall are significantly affected by the magnetic field strength. The results contribute to understand how and where the momentum and energy in the artificial plasma devices are lost, in addition to the presently tested thruster. The plasma momentum is one of the fundamental physical quantities associated with static and dynamic phenomena of plasmas in nature and laboratories. The energy flux being a scalar quantity can be given by the magnitude of the velocity, while the momentum flux is a vector quantity in general. It is crucial to understand and characterize the momentum transport, conversion, gain, and loss mechanisms for clarifying the structural formation of plasmas such as the astrophysical jets 1 , the particle acceleration in auroras at the Earth and Jupiter 2,3 , the coronal mass ejection from the Sun 4 , the interaction between the plasmas and the geomagnetic field 5 , and so on. In these naturally appearing plasmas, the processes involving the momentum and energy transfer occur due to the interaction with electromagnetic fields, collisions, turbulences, and so on, since they cannot see any physical boundaries in space except for the surface of planets. Terrestrial artificial plasmas ubiquitously contact to physical boundaries; forming a sheath maintaining charge balance in plasmas 6. Plasma-wall interactions involving the momentum transfer and loss also significantly affect the plasma behavior in the laboratories, e.g., in ref. 7,8 , in addition to the interactions occurring in the above-mentioned natural plasmas, e.g., interaction with the magnetic fields 9-11. The electric field perpendicular to the physical boundary is spontaneously formed in the sheath and accelerates the ions toward the boundary; resulting in the transfer of the momentum flux perpendicular to the surface. However, if they have velocity components parallel to the boundary surface, they can also deliver their momentum parallel to the boundary. Therefore,...

“…Furthermore, the experiment in Ref. [23] has shown the excellent agreement between the directly measured thrust and the force to the target. Since the energy range of the incident ions is similar to and the target material is same as those in Ref.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 89%

“…Since the energy range of the incident ions is similar to and the target material is same as those in Ref. [23], the measurement reported here is considered to be reliable. Figure 2 (a) shows the schematic diagram of the experimental setup.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 96%

“…The calibration coefficients can be obtained by slowly sweeping the current supplied to the calibration coils, where the displacements and the forces imparted to the pendulums are simultaneously measured by light-emitting-diode (LED) sensors and the load cells to which permanent magnets (PMs) are attached, respectively, being very similar to the procedure of a large-diameter target pendulum in Ref. [23]. This procedure can be done in vacuum in the present configuration by connecting all the electric signals and the coil current Fig.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 99%

See 1 more Smart Citation

Simultaneous Measurements of Local Axial and Radial Momentum Fluxes near a Radial Wall of a Helicon Source

Sugawara

Plasma and Fusion Research

Andõ

2019

Self Cite

Axial and radial momentum fluxes near a lateral wall in a helicon plasma source are preliminarily investigated by installing a momentum vector measurement instrument, which has a detector plate mounted on a double-pendulum structure movable in both the axial and radial directions. The result demonstrates the presence of the axial momentum flux transferred to the radial wall, which seems to be delivered by the ions having the axial velocity and lost to the wall. Furthermore, a significantly greater radial momentum flux is lost to the radial wall, implying that the energy loss occurs at the radial wall. The presently shown technique would be useful for identifying the spatial profile of the momentum vector of the plasma.The momentum flux of plasmas is one of the crucial physical quantities associated with acceleration, transport, and confinement of various plasmas [1][2][3][4], since many of the plasma characteristics are well described by momentum equations, which imply that the external forces applied to fluids are balanced to their momentum flux. Therefore, the momentum balance is very often used to model various plasmas ranging from naturally occurring plasmas to artificially-made terrestrial plasmas in small laboratories.One of the direct applications of the plasma momentum flux is an electric propulsion for spacecrafts [5]. The performance of the propulsion devices can be typically characterized by a thrust-to-power ratio F/P, a specific impulse I sp , and a thruster efficiency η p , where F and P are the thrust and the electric power, respectively [6]. The latter two are defined aswhere m dot and g are the mass flow rate of the propellant and the gravitational acceleration at sea level, respectively. Since all of the assessment parameters are given by the thrust F and the well-controlled parameters such as the electric power P and the mass flow rate m dot , the measurement of the thrust F should be taken on top priority to assess the thruster performance in laboratories. According to a momentum conservation of the spacecraft and the exhausted propellant, the thrust force is equal in magnitude and opposite in direction to the momentum flux exhausted from the spacecraft as well known as a rocket equation [6]. Therefore, the direct measurement of the thrust is indeed equivalent to the identification of the absolute value of the total momentum flux of the plasma; being also useful for understanding other plasmas if the local momentum flux can be identified.The direct and individual measurements of the total thrust and thrust components exerted to the axial wall, the radial wall, and the magnetic nozzle have clarified many aspects of physics in a magnetic nozzle helicon plasma thruster [7][8][9][10][11][12][13][14][15]. In highly ionized conditions, e.g., for propellants of xenon and krypton, or for several kW rf power in argon, the axially negative force on the radial wall, which directs to the downstream side and is integrated over the whole inner surface, has been detected in the individual measurement of the ...