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THREAD: Electric Propulsion 
- a cool way to get around in space https://twitter.com/astronaia/status/1144860584976011265
- a cool way to get around in space https://twitter.com/astronaia/status/1144860584976011265
1/ What is it? Itās a class of propulsion systems that use electrical energy to energize a gas, and accelerate it to produce thrust!
2/ What are some types of Electric Propulsion (EP): Electrostatic, Electromagnetic and Electrothermal! (Notice all that electro-, this just means all of them are driven by some kind of interaction with an electric field)
2 - part 2/ Electric fields are basically just the path that a positively charged particle will go, when placed in a field! They always go from positive to negative. In EP systems, they are typically created with anodes (negatively charged) and cathodes (positively charged)
3/ Remember the types of EP only differ by how they accelerate the propellant - basically how they THROW the energy from direction to the other to produce thrust in the opposite direction. thatās all thrust really is: throwing something in the opposite direction!
4/ you do this to produce an equal and opposite force in the other direction! :) now just imagine throwing a million tomatoes in the vacuum of space! Thereās less of an atmosphere in space so thereās nothing to stop you from going the opposite direction!
5/ this is the biggest benefit of EP! It produces relatively low thrust (by relative I mean compared to the big chemical rockets that took the Tesla Roadster into space) HOWEVER, because thereās less particles in space to stop your spacecraft from moving, you can accumulate speed
6/ So whatās the advantage of Electric Propulsion over Chemical Propulsion? EFFICIENCY! One of the highest amounts of thrust produced by an electric thruster was like 5.4 Newtons whereas a chem rocket can hit up to 1.8 MILLION Newtons! So how on Earth is that better?
7/ well thatās the point! Space propulsion is meant to be used in space. If you strapped an electric thruster on a car today it would take like 4-5 days to get up to 60 mph! But in space, you can reach up to like 948473893 m/s over time for wayyy less propellant/fuel!
8/ you tell me, as a spacecraft designer, would you like to strap this to your spacecraft (left - solid rocket booster from shuttle days) or this (right - little baby xenon propellant tank)?
9/ Thereās no way itās all good in the hood... whatās the drawback? POWER. Oh lawd. POWER.
10/ Like I said before, electrical power is the most important factor for EP. Itās how you energize your propellant! The most popular EP propellant is xenon gas. The gas is energized to move it from its neutral state to a charged state with electrons (-) and (+) Xenon ions.
11/ It is then accelerated by electrostatic/magnetic/thermal means (weāll get into that later) BUT BASICALLY MORE POWER = MORE PARTICLES TO ACCELERATE (thrust out of the back of the thruster). And sometimes it takes ALOT.
12/ Remember when I mentioned that the current record for max thrust of an EP System was about 5.4 Newtonās of thrust? Well it took 102 THOUSANDS OF WATTS to achieve that little itty bitty thrust level :/ https://www.spaceflightinsider.com/space-centers/glenn-research-center/x3-hall-thruster-sets-records-nasa-glenn/
13/ now the reason I havenāt gotten too much into the physics is because there are a plethora of types of EP thrusters that fit VERY different spacecraft mission needs and spacecraft sizes. Here is a nice list :) (courtesy of @esa https://m.esa.int/Our_Activities/Space_Engineering_Technology/What_is_Electric_propulsion)
14/ Iām hoping to specialize in Hall-Effect Thrusters (HETs) and Ion thrusters when I get to grad school! I would be happy to talk/ answer questions about those but I hope this was a good general overview of why EP is cool and great! (PS: it also looks super sci-fi 
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NOW! If that sucked which Iām sure it did to some, here is a great resource that explains this much more thoroughly than I did : http://www.esa.int/esapub/br/br187/br187.pdf! I hope you all enjoyed this!
I TOTALLY forgot to put a disclaimer on this: I HAVE NEVER TAKEN A CLASS IN EP. lol. This is all from independent study/research, and knowledge from my internships! So please, donāt take this (or any info) at face value. Use this as a starting point and do ur own research!
