What ever happened to Ion Engines?

[TheBlueHydro]

I've recently been trying to build a small probe-like craft with xenon-ion engines and have found it to be quite effective. however, there seem to be almost no popular designs on the forum that use them. why?

[El wonso]

People seem to be too impatient for ion engines. Burns are rather long with only 0.5 kN thrust.

[CalculusWarrior]

For probes and other similarly-sized craft, ion engines are fantastic. Still, burns are quite long. If you try to power anything greater than probe-sized ships, you quickly get into the range of several-hour-long burns, only feasible in the depths of space. I suppose coupling a craft like that with the autopiloting feature of MechJeb would allow you to set up a burn, then leave and go do something else for a couple of hours.

[SlyReaper]

And if I recall correctly, the ion engines in game have about 100 times more thrust than real ion engines.

[Spartwo]

I use them quite a lot SSTOs,Fighters,Probes,Aircraft.

[Tigermisu]

And if I recall correctly, the ion engines in game have about 100 times more thrust than real ion engines.

Holy crap.

[Geschosskopf]

There are mods that add more powerful ion engines, which reduce burntimes to something not much worse than a nuclear engine. Of course, they require beacoup power to run which quickly adds weight so you only see this benefit on small craft. Still, you can do quite a lot with small craft. Note just unmanned science probes but also the whole Kethane operation and manned landers for low-gravity worlds. Plus, they make great personnel transports between stations at different altitudes, between the many moons of Jool, and for hopping around the surface of low-gravity worlds.

[Epthelyn]

And if I recall correctly, the ion engines in game have about 100 times more thrust than real ion engines.

Yes, well, that's real life. There is no warp, so a 200 hour burn where a KSP burn would take 2 hours isn't really a very long time considering that anything going further from Earth gets there in months, not mere minutes.

[Brofessional]

Real ion engines are designed to burn for months or even years at a time.

[dudester28]

I can reach anywhere in the kerbol system without using those ion engines. And with a smaller burn time. Most people just prefer NERVAs.

[Luckless]

If the game would allow for simple programmed auto pilots of ion engine craft to run while I do other things, then I would use them more often. But since I have to be the auto pilot myself, and can only burn engines on one craft at a time...

Ion engines don't get much love from me because I can do more interesting things with my time. I would love to use them more on small probes that I don't have to baby sit, but sadly we don't yet have a control system that works well for them in many of their most practical cases.

[Spatzimaus]

There are mods that add more powerful ion engines, which reduce burntimes to something not much worse than a nuclear engine.

More importantly, just the addition of a 1.25m ion engine makes a huge difference. I love the ion engine mod, which adds higher-thrust ion engines (that are about half as efficient on your xenon supply), as well as "hybrid" engines that burn both xenon and regular fuel for a nuke-level thrust.

For myself, I use ions for a couple key designs:

> My mapping probe

In the stock game there's not much need for these, but once you add mods they're essential. Specifically, that satellite has three ScanSat sensors surrounding a Kethane scanner, so I need to put one in orbit around every planet before sending a manned mission there, just to know where the biomes and Kethane deposits are. I've got a launcher that stacks four of these on top of a nuke-propelled transfer stage; last night I put one on each Laythe moon other than Bop, then crashed the transfer vehicle into Jool itself (release the Kraken!).

The burn times get a bit ridiculous, but I just leave KSP running in a window while I go do other things for the time it takes to burn. The other night I had one of these doing a two-hour burn (I think it was the one entering Moho's orbit), and even with physics acceleration that's a long burn. So I went and watched a movie.

> My SSTO spaceplane

If you look at the ends of the wings, you'll see two ion engines (the 1.5kN ones from the mod) with a bit of xenon. The biggest problem I have with spaceplanes is simply fuel supply; it's hard to make one that can carry enough fuel to get to Laythe, even on an LV-N (which that design has) without several refueling stops along the way. So, I've put those ions on to allow the plane to make a really long burn for interplanetary transfers. They don't add much weight to the design, and can make a huge difference in capabilities. The burns get ridiculously long, of course, but again, I do something else while I wait.

Now, the hybrid ions get used in most of my other designs; they're ISP 900 in space, although they consume more fuel types (which lowers the effective ISP a bit) and use electricity. But they don't really count for the question posed in the OP, which refers to the old high-efficiency, low-thrust ions we all know and love.

[Ralathon]

The thing is, ion engines are awesome, but only if you are a very minimalist engineer. Most people don't seem to enjoy building 5 part probes, so they don't see much use.

[magnemoe]

Then using ion engines you want to use the 1x6 solar panels not the huge ones who give more power but is much heavier for the power you get.

Make an mast of small struts with solar panels, on two sides, rotate ship so they get maximum sunlight, one benefit of the small panels is that they don't cast shadow on each other.

This took me from Eve to Moho and back during my grand tour. Lander on top. the center can be separated and used as an upper stage. TWR is pretty good, has had nuclear ship with worse performance.

[Monger]

A lot of KSP Players tend to think "bigger is better".

Also: "if it doesn't work, add moar boosters".

But I guess the more the game progresses, the more you will see such designs. Small space probes are insanely effective: you can easily launch with a medium sized rocket from Kerbin, and reach and land on any planet with an atmosphere in the system. Once there are biomes for Duna and Eve, this will be by far the easiest and most effective way to gather science from other planets. You just need to hit the atmosphere somehow.

(Then again, the time consuming acceleration phases are really annoying. There needs to be a way to deal with this)

[TechnicalK3rbal]

Everyone else is right, their to weak, (it's better to use a NERVA) and the do have approximately 69 times more thrust than the real one

Please correct the math if it's incorrect.

[Moonfrog]

I suggest Kerbal cartoons of in cabin activities. Or I think what some people do is launch lots of stuff send it out all at once, by the time they done something the other has arrived, or crashed, or started an intergalactic war.

[Spartwo]

Nukes weigh 2.5 tons for just the engine a good Ion probe might weigh less than that.

[thunderstar]

And if I recall correctly, the ion engines in game have about 100 times more thrust than real ion engines.

yes, but you can get easily impatient of watching such long burns, i can't be sitting playing a game for hours just to get the probe into the right trajectory, i think anyone can't do it, its just too long

[_Aramchek_]

I've tried to use them...but....seriously...I do not have the time or pateince to use them. And, well "pooooowwweeeeerrrrr!!!!!!!!!!!!".

If a thing is worth doing, it's worth over doing, especially when the "thing" in question is thrust. *ahem*

[SunJumper]

If high physics warp could reduce all the part masses to a single point mass, and then have the thrust act on this point only, it may be possible to complete ion burns in a few minutes of play time.

[architeuthis]

Everyone else is right, their to weak, (it's better to use a NERVA) and the do have approximately 69 times more thrust than the real one

Please correct the math if it's incorrect.

From the link it says special high power Hall-effect thrusters (only usable in a lab) give 3 N of thrust. In that case the PB-Ion is 167 time more powerful than the real life thruster. But it says further that Hall-effect thursters typically found in actual spacecraft (the 1.35 kW it mentions seems reasonable for a space probe) will only have 83mN of thrust, in which case the PB-Ion is 6024 time more powerful than real thrusters.

In fact the modest little PB-Ion is a bit more powerful than a 20MW VASIMR! Yikes!

Edited November 18, 2013 by architeuthis

[LostElement]

I hated how Ion Engine burnt up so much electricity and only produced .5 thrust. So i just made it not use electricity and gave it a thrust of 1.25.

[annallia]

Nukes weigh 2.5 tons for just the engine a good Ion probe might weigh less than that.

This is true, I have made some tiny ion probes that weighed next to nothing.

That being said I would rather have launched an 8 ton probe (nuke + fuel) and had a 2 minute burn time than wait for that hour.

[arq]

Ion engines have terrible TWR (especially once you count solar panels), so burns take forever. I sent a probe to mess around in the Jool system for awhile. It was fun grav-assisting between moons on tiny bits of fuel, but then I decided to head for Eeloo and then back home and that took forever.

Ions are nice when ships are too small for LV-Ns, but I can usually get plenty of dV for such small probes out of some tiny tanks and an LV-1 or a 48-7s, with abundant thrust. I mean, once you break into interplanetary space, do you really need 14km/s of dV? I prefer the chemical rockets because I don't have any form of autopilot installed and it makes burns much more bearable.