Plasmoid thrusters have had successful proof of principle experiments done in the lab at Princeton University. The systems should be compact and simple and based upon magnetism present in solar flares. There are designs for initial systems with ISPs in the range of ion drives. The systems should scale to higher ISPs of 50,000 and to higher thrust power levels. They hope to make the first systems for space deployment in the 2-5 year time frame. The first applications would be tugs or stages moving from low earth orbit to the moon.
It can deliver high thrust at high and variable exhaust velocity (tens to hundreds of km/s). It should therefore get unsurpassed gas mileage for longer trips (Mars and beyond).
According to computer simulations run by the Princeton Plasma Physics Laboratory and the National Energy Research Scientific Computing Center at the Lawrence Berkeley National Laboratory in Berkeley, California, her thruster concept produced exhaust velocities that are ten times greater than a traditional ion propulsion system with speeds at hundreds of kilometers per second. Exhaust velocities in the range of 20 to 500 km per second, controllable by the coil currents, are observed in the simulations.
Plasmoids with radius 10 cm and reconnecting field of 800 Gauss , the calculated thrust is about 50 Newtons. Taking into account a duty cycle of about 33 % (i.e. the distance between two consecutive plasmoids is twice the plasmoid length). The input power varies from a few to a few hundred kiloamps. In the simulations 100 kiloAamps corresponds to about 10 MW of power. For this unoptimized high-power case (with a thrust of 50–100 N), the ratio of thrust over power is thus about 5 to 10 milli-Newtons per kilowatt. Tentatively the optimal parameter range for this new thruster will be ISP (specific impulse) from 2000 to 50 000 s, power from 0.1 to 10 MW and thrust from 1 to 100 N. It would thus occupy a complementary part of parameter space with little overlap with existing thrusters.
There are various small funded projects working on Plasmoid Thrusters.
There is a US Air Force SBIT phase 1. Eagle Harbor Technology, Inc. (EHT) and the Professor Ben Jorns at the Plasmadynamics & Electric Propulsion Laboratory at the University of Michigan (UM) partnered to advance the state of the art Rotating Magnetic Field-Field Reversed Configuration thruster (RMF-FRC). This technology takes inspiration from fusion energy science. The RMF created plasmoids are accelerated out of the thruster at high speed. Using previously developed EHT Full-Bridge Modules, EHT built a solid-state power system to drive the RMF coils for the UM thruster. EHT has used a similar power systems to drive an Electrode-less Plasma Source and High Power Helicon Experiment for pulse durations up to 1 ms. In this SBIR, EHT developed a new version that can operate continuously at up to 4 kW average power while still driving peak currents of 2 kA at 500 kHz.
Rotating Magnetic Field-Field Reversed Configuration (RMF-FRC) operation. Left: Plasma fluxes into volume with biased magnetic field. Middle: RMF antenna generates azimuthal current in plasma giving rise to field reversal. Right: Lorentz force interaction with background magnetic field.
There is a new multi-turn, multi-lead design for the first generation PT-1 (Plasmoid Thruster) that produces thrust by expelling plasmas with embedded magnetic fields (plasmoids) at high velocities. This thruster is completely electrodeless, capable of using in-situ resources, and offers efficiencies as high as 70 percent at a specific impulse, Isp, of up to 8,000 s. This unit consists of drive and bias coils wound around a ceramic form, and the capacitor bank and switches are an integral part of the assembly. Multiple thrusters may be ganged to inductively recapture unused energy to boost efficiency and to increase the repetition rate, which, in turn increases the average thrust of the system.
The thruster assembly can use storable propellants such as H2O, ammonia, and NO, among others. Any available propellant gases can be used to produce an Isp in the range of 2,000 to 8,000 s with a single-stage thruster. These capabilities will allow the transport of greater payloads to outer planets, especially in the case of an Isp greater than 6,000 s.
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