Q: How many modes there are?
A: From 1 to 3, every mode corresponding to equal thrust multiplier. However, increase of thrust results in loss of efficiency, on mode 2 engine will consume 3x more fuel, and on mode 3 the consumption is 9x.

Q: How do I switch through modes?
A: As I already said, you can switch them using slider in Terminal GUI, by Hotbar actions (just like thrust override), and through PB scripts using "EngineMode" property (available only on xenon engine blocks, check for SubtypeID contains "XenonEngine"!).

Q: Is this for Dev or Stable?
A: Currently this is for Dev branch. Stable may have issues.

Q: Does this mod suffer from game's bug with ThrustMultiplier being ignored by WASD and dampeners?
A: Not anymore. I have implemented a workaround, and now thrust modes are correctly behaving on manual and I.D. However, keep in mind that this works by "manually" applying the "leftover" thrust on grid's center of mass: this means, you may experience some weird physical behavior if there are some more game bugs or if you use mods such as Realistic Thrusters.

Q: Does it consume electricity?
A: Not yet. Now it is close to impossible due to game limitations, where any powered block can use only one type of fuel (game-wise electricity is a fuel, too). However, such functionality is expected to come when Cython will finish his Bipropellant modscript.

Q: What? Xenon used as propellant? Is that realistic?
A: It is.[en.wikipedia.org] Yes, the ranges of 640-196 kN or even 640-1960 kN are, perhaps, way overrated, but who knows what would be achieved in plasma thrust to 2077 if we already have 300MW-class self-contained (with all the heat management and stuff: shove uranium-235, get power) nuclear reactors fitting in less than 74 tonnes in game?

Q: Is it more efficient than Hydrogen thrusters?
A: Yes, and by much! In normal mode, it's 16 times more efficient. In Mode 2 it's around 5.3x, and in Mode 3 it's 1.7.

Q: How long do they work?
A: Here's a neat script which allows to calculate the fuel usage and remaining burning time in real time. As a "rule of thumb" you may use these estimated values (for both small and large): for 1 engine per 1 full tank, in Mode 1 the burn time is circa 1600s or 26m 40s, in Mode 2 it's 8m 53s, and for Mode 3 it's 3m 4s. Yes, 3x thrust has it's price.

Q: How do the Ramscoops react on speed mods? How do they react on being spinned on a rotor?
A: The collection rate is proportional to world's speed limit per grid type. So if max speed is 200 m/s, going at 100 m/s will yield 50% rate max. As for rotors, scooping rate is based on the grid's linear velocity, not on the block's own speed.

Q: How much do they weight, and how sturdy they are?
A: The smallgrid Xenon engine has 3 steel plates on top of it, so it's quite protected. But it only weights about 170 kg. For largegrid... hey, who does not use Digi's Build Info since it's back online?

Q: How the xenon is distributed? Do I need piping?
A: Yes, basically it's a yet another gas, so just like hydrogen engines the fuel path is: xenon tanks -> conveyor -> engines.

Q: Why the isotope separators are so power-hungry?
A: This is an attempt to make up the 'implied power requirement' for xenon engines, and an attempt to prevent the absurdous situation with hydrogen when it's better to generate it literally on-the-fly from ice than to produce, store and use. Same goes for their mass.

Q: What is the best way to acquire fuel?
A: Either a station with several separators, or sky-diving and scooping xenon from upper atmosphere of any planet. Tip: for modded "gas giants" with dense atmosphere the scooping rates are much higher.

Q: How efficient they are in atmosphere?
A: At Earth sea level, they have 40% thrust. For comparison, vanilla ion thrusters have 30%.

Q: Is it possible to scoop xenon on atmosphereless moons?
A: Yes, with same efficiency as in open space.

Q: I am going with a ramscoop, and the oxygen is filling, too!
A: The Xenon Ramscoops are indeed able to acquire few Oxygen particles in amounts barely able to keep stocked few standard suits. However, the Ramscoops are tuned to collect Xenon, and in an oxygenated atmosphere a basic air vent will be much more efficient.

Q: Is this mod MP/DS ready?
A: Yes. Everything is synced and saved properly. Or at least it shall. Report, please, of any oddities you find.

Q: I am a modder, and I want to make my thruster switchable too!
A: Write here in comments, or add me on Steam, and we can discuss this. The variable thrust script can be adapted to any thruster, fueled or electrical.

Q: Are these a copy of KSP xenon engine?
A: Jool divers, anyone?