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### Why will Starlink satellites use krypton instead of xenon for electric propulsion?

The press kit for the first Falcon 9 Starlink launch and deployment of the first 60 satllites scheduled for May 15, 2019 says: With a flat-panel design featuring multiple high-throughput antennas ...
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### Why do ion thrusters frequently use xenon as the reaction mass?

From skimming the Wikipedia article on ion thrusters, I notice that xenon is frequently (though not exclusively) used as the reaction mass in systems that have actually been deployed - Deep Space 1, ...
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### What kind of engine uses water as a propellant?

I often read about future spacecraft gathering water ice to use as a propellant, yet this doesn't line up with any of the propulsion methods I know to exist today. What type of engine could use water ...
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### Have light gases like hydrogen or helium been explored for ion propulsion?

This answer and discussion in comments below this answer mention that for an ion of mass $m$ and charge $q$ accelerated by a voltage $V$ the momentum it receives (impulse) is p = \sqrt{2mqV} = \...
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### Why does the NASA NEXT engine use xenon? [duplicate]

Why does the NASA NEXT engine use xenon? Why not use argon or krypton? Does it have to do with the thrust to power ratio or the specific impulse or something else?
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### What performance specification would be lower for Krypton than for Xenon in Hall effect thrusters?

The Ars Technica article SpaceX scrubs first attempt to launch 60 Internet satellites [Updated] (found here) discusses the use of Krypton rather than Xenon in the Starlink Hall effect ion thrusters: ...
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### What could go wrong if someone overpowered an ion engine?

The X-3 ion engine is the most powerful ion engine ever made, and puts out an astounding 5.4 N of force, using 103 kW. It's fuel is inert xenon gas, ionized and heated to a plasma. Now, what would ...
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### What are the parameters of the new Iodine electrical rocket engine developed by RSC Energia?

Several news outlets are reporting Energia Rocket and Space Corporation is nearing completion of a new electrical rocket engine using iodine stored as a solid and vaporized as needed. The new ...
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### Would more or less gravity make you proportionately stronger?

It is known you can lift more if gravity is weakened, but more weighs less in less gravity. Though what is the ratio compare to normal gravity...like if you can lift 100% of your body weight in a ...
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### MARS-CAT; What is a Cubesat Ambipolar Thruster and how does it work?

Trying to understand ion thrusters a little, I started looking at https://en.wikipedia.org/wiki/Ion_thruster#Propellants where I saw: The CubeSat Ambipolar Thruster (CAT) used on the Mars Array of ...
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### What is a lithium fed GIT? How does it work?

This answer to What is the maximum speed an ion engine can propel a spacecraft at? mentions the following: Lithium fed GIT (gridded ion thrusters) have demonstrated 50,000 - 80,000 seconds of ISP (...
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### What are the advantages of solid iodine propellant and how is it used for ion propulsion?

I was reading about different sources of propellant for ion thrusters, Xenon being the most common. However, in more recent articles I've found more and more mentions of Solid Iodine being used as ion ...