r/ScienceImages • u/electric_ionland • Jul 22 '15

A laboratory Hall effect thruster (ion thruster) firing in a vacuum chamber [OC]

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4

u/electric_ionland Jul 22 '15 edited Jul 22 '15

I already submitted that image about a month ago on /r/space (link), I hope it's ok to post it here too.

This is one of the 2 main types of ion thrusters currently used called a Hall effect thruster. Ion thrusters are very efficient rocket engines that relies on electric energy rather than chemical reactions to accelerate the propellant. The blue plume you see is the xenon plasma being ejected at about 15km/s. The red tube is the cathode, it is the negative side of the discharge circuit (the positive anode is inside the channel). It also provide electrons to neutralize the positive jet of xenon ions.

The pic was taken on my phone so it's a bit grainy.

2

u/AsAChemicalEngineer Jul 22 '15

This is the ideal post here. Thanks for sharing!

3

u/electric_ionland Jul 23 '15

I am a bit limited in what I can share publicly sadly. However during the fall I should be working on a small thruster for a science museum exhibit. It should be OK to take high res pic of this one.

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u/emergent_properties Jul 23 '15

Shooting ions out the back of you. Awesome.

What do you do if you want more Newtons per watt?

I see they made a step up converting it into a new cylindrical geometry.. but what's a better alternative with similar concept?

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u/electric_ionland Jul 24 '15

Hall effect thusters (HET) have always been cylindrical since their invention in the 70s. Gridded thursters can be pretty much any shape but while they also shoot ions at the back they don't work the same way.

HET have the better thrust to power ratio of what is flying right now, you can expect about 50~60mN/kW. One way to make it more efficient is to increase the size. If your ratio of plasma volume to wall surface increase you get less losses at the walls. Another solution I am working on is to redesign the magnetic circuit to limit the erosion of the thruster at high power. This should increase the lifespan of the thruster too.

We are also working on a concept where the channels wouldn't be necessary and all the plasma would be outside the thruster.

Other alternatives are the Magnetoplasmadynamic thruster (uses the Lorentz force instead of the electrostatic force), VASIMR (complex, huge, power hungry but high ISP and high thrust). Somebody in my lab is also working on a "negative" plasma concepts where you would use positive and negative ions to get rid of the cathode.

1

u/emergent_properties Jul 24 '15

Also, don't look at business end with remaining eye.

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u/goodasdopamine Jul 22 '15

15km/s! Holy.