How does a pulsed plasma thruster work?

In summary, the pulsed plasma thruster utilizes an arc formed on the contaminated surface of PTFE to create a high temperature plasma of PTFE breakdown products. The plasma is propelled by the force ##\vec F=q \dot {\vec r}\times \vec B## as well as collisions with outward moving electrons. The ions will also feel E and B field forces, causing them to move away from the PTFE surface.
  • #1
Leo Liu
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I really can't get my head around the concept of pulsed plasma thruster. All I know now is that it utilizes ##\vec F=q \dot {\vec r}\times \vec B##. Could someone explain the mechanism to me, please? Thanks!
 
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  • #3
Leo Liu said:
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I really can't get my head around the concept of pulsed plasma thruster. All I know now is that it utilizes ##\vec F=q \dot {\vec r}\times \vec B##. Could someone explain the mechanism to me, please? Thanks!
A short, hand wavy, description:
When the arc forms, hopefully on the right side near the teflon, it creates the B field (out of the page). Then the moving electrons (up) experience the force you described ##\vec F=q \dot {\vec r}\times \vec B## (to the right). So that arc is propelled to the right and pushes a bunch of teflon bits out with it. The arc extinguishes when it's source discharges, and then the cycle repeats.

I like to think that the force is created to oppose a change in the magnetic flux. For a given current amount, the flux can be reduced by increasing the loop area, i.e. pushing the arc away.

This is also how rail guns work, if you want to look into those too.
 
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  • #4
DaveE said:
A short, hand wavy, description:
When the arc forms, hopefully on the right side near the teflon, it creates the B field (out of the page). Then the moving electrons (up) experience the force you described ##\vec F=q \dot {\vec r}\times \vec B## (to the right). So that arc is propelled to the right and pushes a bunch of teflon bits out with it. The arc extinguishes when it's source discharges, and then the cycle repeats.

I like to think that the force is created to oppose a change in the magnetic flux. For a given current amount, the flux can be reduced by increasing the loop area, i.e. pushing the arc away.

This is also how rail guns work, if you want to look into those too.
Thank you. I understand everything now but what sets the plasma in motion.
 
  • #5
Leo Liu said:
but what sets the plasma in motion.
The arc is initiated across the contaminated surface of the PTFE. There is no atmosphere. The arc forms a high temperature plasma of PTFE breakdown products.
To explain the initial ion velocity, consider that the ions used for propulsion can only travel away from the PTFE, and that is at their thermal velocity in the plasma.
 
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  • #6
Leo Liu said:
Thank you. I understand everything now but what sets the plasma in motion.
Also collisions with the outward moving electrons will push some of the plasma. The charged ions will also feel E and B field forces, like the electrons.
 
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FAQ: How does a pulsed plasma thruster work?

1. How does a pulsed plasma thruster create thrust?

A pulsed plasma thruster works by creating a plasma, which is a gas that has been heated to extremely high temperatures, and then expelling it out of the back of the thruster at high speeds. This creates a reaction force in the opposite direction, propelling the spacecraft forward.

2. What is the fuel source for a pulsed plasma thruster?

The fuel source for a pulsed plasma thruster is typically a noble gas, such as xenon or argon. These gases are ionized and heated to create the plasma used for propulsion.

3. How does a pulsed plasma thruster differ from other types of thrusters?

A pulsed plasma thruster differs from other types of thrusters in that it uses a pulsed discharge to create the plasma, rather than a continuous discharge. This allows for more efficient use of the fuel and a higher specific impulse, or thrust per unit of fuel.

4. What are the advantages of using a pulsed plasma thruster?

Some advantages of using a pulsed plasma thruster include its high specific impulse, which allows for longer missions and more efficient use of fuel. It also has a low mass and can operate for long periods of time without needing to be refueled.

5. What are the limitations of a pulsed plasma thruster?

One limitation of a pulsed plasma thruster is its low thrust compared to other types of thrusters, which limits its use for larger spacecraft. It also requires a significant amount of power to operate, which can be a challenge for smaller spacecraft. Additionally, the plasma can erode the thruster over time, requiring maintenance or replacement.

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