Novel concept of tailorable magnetic field and electron pressure distribution in a magnetic nozzle for effective space propulsion

Magnetic nozzle appears to be a practical solution for prolonged space missions.For efficient handling of the spaceship,an in-flight solution to customize the thrust from the magnetic nozzle is essential.Here a new concept of three-thick coils system is proposed for tailoring the magnetic field in-flight in accordance with electron pressure distribution.The role of peak position of the pressure and its axial gradient is also uncovered for realizing higher thrust.About three-fold increase in thrust is observed when the electron temperature is raised to w2.5 times of its original value at the exit plane.The set-up is optimized for its best performance and efficient use in the electric space propulsion sector with thrust approaching 5 mN.In particular,this can contribute to the attitude control or the precision pointing of the spacecraft,the technology for removal of space debris and manipulating the ion momentum flux lost to a wall or unsteady laser produced plasma flow in a magnetic nozzle.

The azimuthal currents in the ion-driven magnetic nozzle

Ion-driven magnetic nozzles(Ti>Te)are designed as intrinsic parts of cutting-edge propulsive technologies such as variable specific impulse magnetoplasma rockets(VASIMRs)and applied-field magnetoplasmadynamic thrusters.Employing a two-dimensional axisymmetric particle-in-cell(PIC)code,in the ion-driven magnetic nozzle,the compositions and distributions of azimuthal currents in different axial regions are investigated under various inlet ion temperatures Ti0 and found to differ dramatically from that in the electron-driven magnetic nozzles.Previously reported to be all paramagnetic and vanishing under a high magnetic field,the azimuthal currents resulting from the E 3 B drift are shown to turn diamagnetic and sustain a considerable magnitude when Ti0 is considered.The previously reported profile of diamagnetic drift current is altered by the introduction of inlet ion temperature,and the paramagnetic part is significantly suppressed.Moreover,a wide range of paramagnetic currents appear downstream due to the inward detachment of ions,which can also be reduced by increasing inlet ion temperature.Albeit considered in this paper,the azimuthal currents resulting from grad-B and curvature drift are still negligible in all cases of interest.The magnitude of diamagnetic azimuthal currents increases with amplifying Ti0,indicating a clear physical image of energy transformation from ion thermal energy to the directed kinetic energy through electromagnetic processes in the magnetic nozzle.Additionally,the magnetic inductive strength also has noticeable impacts on the azimuthal currents,the current magnitude tends to decrease as the magnetic field increases,and over-increment of it may result in larger divergence angles and lower nozzle efficiency.

Production of a High-Mach-Number Plasma Flow for an Advanced Plasma Space Thruster

A higher specific impulse and a larger thrust are required for a mannedinterplanetary space thruster. Prior to a realization of a fusion-plasma thruster, amagneto-plasma-dynamic arcjet (MPDA) powered by a fission reactor is one of the promising candidatesfor a manned Mars space thruster. The MPDA plasma is accelerated axially by a self-induced j x Bforce. Thrust performance of the MPDA is expected to increase by applying a magnetic nozzle insteadof a solid nozzle. In order to get a much higher thruster performance, two methods have beeninvestigated in the HITOP device, Tohoku University. One is to use a magnetic Laval nozzle in thevicinity of the MPDA muzzle for converting the high ion thermal energy to the axial flow energy. Theother is to heat ions by use of an ICRF antenna in the divergent magnetic nozzle. It is found thatby use of a small-sized Laval-type magnetic nozzle, the subsonic flow near the muzzle is convertedto be supersonic through the magnetic Laval nozzle. A fast-flowing plasma is successfully heated byuse of an ICRF antenna in the magnetic beach configuration.

Tapered coils system for space propulsion with enhanced thrust: a concept of plasma detachment

A concept for plasma detachment in a magnetic nozzle is developed based on the detachment region which is found to decrease with the taper angle of the coils employed in the proposed flexible three coil setup.On tapering the coils while resulting in the same crosssectional area,the plasma plume outside the throat grows radially that leads to an enhancement in the thrust from 2.67 mN to 5 mN at the final detachment plane for a rise in the taper angle from 0 to 13
.The maximum thrust can reach about 9 mN when the middle coil is shifted closer to the right coil along with increasing middle-to-outer-coil diameter(inner)ratio from 1 to 3.Proposed three-tapered-coils arrangement for a magnetic nozzle turns out to be a robust candidate for space propulsion offering the ability to control plasma detachment and tune thrust in-flight simply via mechanical movements without changing the current.