The Use of Ion Propulsion?

[Liudeius]

Has anyone found a useful purpose for ion propulsion?

I've tried using an ion drive on the smallest possible probe, and the burn time for interplanetary travel was hours or days.

I can't imagine more engines would help much either due to their tiny thrust not outweighing the significant increase in mass which the required structural changes would cause.

I know about the solar glider, but there's not much purpose to exploring Kerbin, and normal jet fuel lasts a long time, so I don't really see that as a "useful" purpose.

Answer: Only use them if you are crazy hardcore or value fictional efficiency over your time.

Edited July 26, 2013 by Liudeius

[goldenpeach]

I did find useful purpose for it:using a very hight efficient engine.

It's can also be used for make (very)fine tunig of your orbit.

Anyway,I never use it:I prefer our old friend atomic engine!

[MalfunctionM1Ke]

Well... you could use it as a pocket heater

[agentexeider]

I did find useful purpose for it:using a very hight efficient engine.

It's can also be used for make (very)fine tunig of your orbit.

Anyway,I never use it:I prefer our old friend atomic engine!

Fusion Drives are my drive of choice.

[Liudeius]

I did find useful purpose for it:using a very hight efficient engine.

It's can also be used for make (very)fine tunig of your orbit.

Anyway,I never use it:I prefer our old friend atomic engine!

Only if you're willing to sit at your computer for a day to even break orbit.

But yeah, I use nuclear engines too for long flights (though for me that works out to be a 5 minute burn, not a five hour - five day burn).

[Anton P. Nym]

I'm typing this while running a 1hr 32min ion engine burn designed to get a small probe into an aerobrake with Duna. It takes a long time, yes, but the fuel burned in this maneuver is too light to bother measuring... making the booster I used to get the probe this close a lot lighter.

Of course it's not as good as some of the modded engines out there... I think I'll close out this 0.20-era game-save with another try at getting an Orion nuclear pulse rocket out the same way to see if the new SAS/ASAS treats it more gently than the previous Kraken-bait version did. But I've also made a glider probe with solar-powered four ion engines that I can use to "kick" it up when I need to climb, and (I think) it can fly on Eve for as long as I care to toodle it around.

-- Steve

[capi3101]

I've used ion engines to boost a very small satellite out to geosynchronous orbit around Kerbin; took a few hours to do. I also know of one guy who used them to provide downward thrust on a rover design successfully.

The chief problem with ions is their lousy thrust-to-weight ratio, especially when you consider the mass of the equipment you have to use in order make them work (2 Gigantors, a Xenon Tank and the thruster = 1.07 tonnes). All that and you get a thruster with half the output of an RCS block...a maximum acceleration of 0.5 m/s^2. And that's with no payload.

Edited July 25, 2013 by capi3101

[CosmicX1]

I guess when career mode is fully implemented they will probably be very useful to cut fuel costs... if you're willing to leave your computer alone for a couple of hours while you complete the burn.

[allmappedout]

They're pretty. That blue glow is just too cool.

[WhiteWeasel]

Looks like no appreciates efficiency here. Also unless you're going out to jool orbit you don't need two gigantors for an ion engine to work. A single gigantor produces 18 e/s while an ion engine consumes 14.442 at full thrust. Leaving about 20% extra. Using them to go interplanetary by themselves a bit crazy, but then you are if you don't use physics warp with ions in the first place. The longest burn I had to do was ~12 min, with physics warp cuts that down to a reasonable 3 minutes. Usually I have a boost stage to get them to their destination and deploy them from there.

Mechjeb states that each these have 4.3K ÃŽâ€v for a 12 part 1.4 ton object. I have an entire jool mission documented to prove that these Ion Engines can do it: http://forum.kerbalspaceprogram.com/showthread.php/35878-MLAS-Presents-The-Deep-Space-Splitter

Edited July 25, 2013 by WhiteWeasel

[capi3101]

They're efficient - there's no arguing that. It's just that most folks don't have the patience for that kind of efficiency...hell, I sometimes get frustrated with the burn times of LV-Ns......

[StainX]

They're pretty. That blue glow is just too cool.

Yeah, and you can stare in it like forever in every maneuver you do

[martscht]

I think this is a really good question. I used to use them to power rovers (back when they rode on the spaceplane landing gear) but ever since wheels have power I haven't used a single ion engine. Sometimes I'd simply strap one on a satellite for orbital corrections and such, but since orbits don't deteriorate in this game, there's really no sense in doing this either. Nowadays I just use the Ant-Engine on my satellites because with 2 miniature fuel tanks that still gives you roughly 2000 m/s.

allmappedout basically made the only valid point for using them I can think of...

[maltesh]

Looks like no appreciates efficiency here. Also unless you're going out to jool orbit you don't need two gigantors for an ion engine to work. A single gigantor produces 18 e/s while an ion engine consumes 14.442 at full thrust. Leaving about 20% extra. Using them to go interplanetary by themselves a bit crazy, but then you are if you don't use physics warp with ions in the first place.

Two gigantors do let you use two ion drives, though. And allows them to be arrayed, as in the picture you provided, so that regardless of thrust direction, full-insolation can always be achieved by rotating the spacecraft, without unbalancing.

And like RCS thrusters, ion drive exhaust isn't blocked by other parts (or at least, it wasn't up through 0.20) , so you can stack one (or more) of the ion drives atop the other for more acceleration, assuming you can provide the power.

[ChrisDaBox]

The Ion engine is not designed to be used in an orbit around a planet. Why? Because if you try to make an escape orbit with an Ion engine, you would have orbited a 1/4 of the way around Kerbin making it a highly unreliable way to escape the planet at the exact position you want it to escape.

It takes ages to orbit once around Kerbol. So the area covered during one burn would be minimal if scaled down.

Sorry if you don't understand this. It's kinda hard for me to explain it. Just watch Scott Manley's video about the Ion engines. (Not the solar plane one)

[Pulstar]

Sometimes barely any thrust but high efficiency is good. Like if you have a small robotic tug to attach modules for your station in orbit.

[Anton P. Nym]

The Ion engine is not designed to be used in an orbit around a planet. Why? Because if you try to make an escape orbit with an Ion engine, you would have orbited a 1/4 of the way around Kerbin making it a highly unreliable way to escape the planet at the exact position you want it to escape.

Well, you could... but it's tricky and takes several orbits. You have to "pump the swing" and thrust when you're on the opposite side of the orbit that you want to adjust, then cut engines and coast until you're back to where you thrust before and burn again, and repeat until you get the orbit you want. As I understand it, that's how they work in this mythical "real life" place people talk about.

I'm not patient enough to wait for that, so I use a chemical (or nuclear) rocket to get into an escape orbit and jettison it afterward. I'm using the ion engines for course corrections and circularising orbits once a probe is where I want it... but I'm still exploring how that works. (Particularly I'm wrestling with how inaccurate the "Estimated burn" clock is on low-thrust engines. It's hard to time very long burns with the estimator built-in to the maneuver node system, and ion engines are all about veeeeeeeeery long burns.)

-- Steve

[Liudeius]

I also know of one guy who used them to provide downward thrust on a rover design successfully.

That man is a legend.

Well it seems no, there is no use for them unless you're patient enough for an hour+ burn. (They're pixels, an hour of my time is worth more than fictional efficiency.)

Perhaps you really hardcore people can take that, and yes KSP is a light simulator, but it kind of stands out in how long it takes compared to other thrusters.

[roblamb98]

they are 3 times more expensive than the mainsail, what you save in fuel is lost and then some

[tobjv]

I use the Ion engines to set orbits for my satellites. They last hours. Also for downforce on my rovers on the Mun and Minmus. The link is to another persons rover design using said concept.

http://forum.kerbalspaceprogram.com/showthread.php/25339-0-20-isplore-rover

[WhiteWeasel]

What are you people doing wrong? I never had single burn that long with an ion engine. From a starting orbit and deployed from there in the jool system I can get to any moon (except bop) with about 20-25 min burn time. 5-7 with warp. Are you people building several ton probes expecting a single ion engine to handle it? Or don't use physics warp?

[draeath]

they are 3 times more expensive than the mainsail, what you save in fuel is lost and then some

Money isn't everything.

[Anton P. Nym]

What are you people doing wrong? I never had single burn that long with an ion engine. From a starting orbit and deployed from there in the jool system I can get to any moon (except bop) with about 20-25 min burn time. 5-7 with warp. Are you people building several ton probes expecting a single ion engine to handle it? Or don't use physics warp?

In my case I'm trying to dump 1200m/s of "oops" thrust getting into a suboptimal transfer to Duna; this'll get the probe (in faux-aeroshell) into an aerobraking course that'll end up with a highly-elliptical polar orbit I can circularise (again with ion engine, though less a lot of weight). Then switch on the instruments and "map" the strange red world below.

And all that using a fuel tank about the size of a trashcan.

-- Steve

[WhiteWeasel]

In my case I'm trying to dump 1200m/s of "oops" thrust getting into a suboptimal transfer to Duna; this'll get the probe (in faux-aeroshell) into an aerobraking course that'll end up with a highly-elliptical polar orbit I can circularise (again with ion engine, though less a lot of weight). Then switch on the instruments and "map" the strange red world below.

And all that using a fuel tank about the size of a trashcan.

-- Steve

..umm ok. A little hard to follow. How much does your probe weigh, and how many engines it has? A pic of your orbit would be helpful too.

[Anton P. Nym]

I'm not at my gameplaying computer at the moment; right now the probe (an OKTO in a clamshell made from 1:3 stack converters) is on a 15 000km fly-by because I had to add too much dV on Kerbin's end to get an encounter with Duna. I also botched the solar panels, forgetting that they lose power further from the Sun, so I'm limited to 1/3 thrust on the burn. (All my fault.)

Still, I can burn the ion engine retrograde for an hour at 1/3 thrust to change the flyby into a parabolic going north-south, periapsis at 10km to aerobrake.

That this burn is at all doable I find remarkable, and make me want to try ions on other probes.

-- Steve