Pulsed plasma engine

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Pulsed plasma thrusters or pulsed magnetoplasmadynamic thrusters ( English Pulsed Plasma Thruster ; PPT), also known in German-speaking countries as unsteady magnetoplasmadynamic drives (iMPD), belong to the electric space propulsion system and are mostly used on satellites for position and orbit control . Due to the way they work, they belong to the group of electromagnetic drives.

PPT were first successfully used in 1964 on the Soviet space probe Sond 2 and are therefore considered to be the oldest electric space propulsion systems in space. Since then, they have been used several times for satellite missions, mainly in the USA, but also in Japan and China.

construction

An iMPD engine consists of four main components:

  1. Capacitor for energy storage
  2. Metallic electrodes to physical establishment of the capacitor potential
  3. fuel
  4. Ignition device, e.g. B. a commercially available spark plug

Both parallel and coaxial electrode configurations have been explored in the past. In both cases the fuel is supplied between the electrodes. PTFE is used for most developments , but alternative fuels such as B. Water are examined.

Working principle

The capacitor used is charged with an operating voltage (up to several kV). The ignition is then carried out by an ignition device. The resonant circuit consisting of the capacitor, electrodes and fuel is closed and an arc discharge is formed along the surface of the fuel. Due to the high discharge current of several kA, part of the fuel is ablated , dissociated and ionized . This creates charge carriers between the electrodes. The discharge current, which changes over time, generates a strong magnetic field . The interaction of this field with the charge carriers results in an acceleration due to the Lorentz force . The charge carriers are thus accelerated from the space between the electrodes and generate thrust . The speeds achieved by the load carriers are in the range of several 10 km / s. Since the energy of the capacitor is limited, the oscillation in the circuit dies away quickly, so that after about 10-20 μs the arc breaks down and the thrust pulse ends. Typical pulses achieved are a few 100 μNs.

Technical realizations

Research and development of PPT worldwide is mainly focused on Russia, the USA, Europe, Japan and China, but developments have also been observed in South Korea, Argentina, Iran and Turkey. In addition to Sond 2, PPT has been used successfully on several other satellite missions.

See also

further reading