Ion Probes question

[Moonfrog]

After first building an ion probe, then finding out they take forever to do anything. Then in a thread discovered that u can press alt + > while the ion probe's throttle is maxed to get to acceleration X 4. Come to ask this question.

Given the low thrust of ion probes, at what point is it best to start using its ion engine? recently discovered using the ion engine to escape from kerbin orbit was a no no, even with 4x acceleration. Does anyone have any experience with ion probes? when to switch over to the ion engine, cos my ion probe has 8000 DV.

Should I switch over to it in Sun SOI? some special rule with ion probes?

[Orbiter]

In general, Ion engines are only useful for the smallest of probes. However, the amount of DV you get is insanely high. Basically, if you want to do a transfer you are better off with chemical engines, unless you have a lot of time on your hands. Ion engines are good for things like changing the inclination of a probe. If you have a lunar satellite powered by an ion engine, you can set it up at almost any inclination you want, which is quite useful for things like satellite constellations. In short, ion engines are great for DV hungry maneuvers, but terrible for long burns

[Supernovy]

In the past I've used an Ion probe to perform propulsive capture and orbital manoeuvres around Eve, the closer proximity to the sun means fewer solar panels are needed to run the engine.

Edited November 28, 2013 by Supernovy
grammatical error

[Fail-Man 3D]

In general, Ion engines are only useful for the smallest of probes. ... Basically, if you want to do a transfer you are better off with chemical engines, unless you have a lot of time on your hands.

For stock and RLA ion engines, this is true. However, the Near-Future Propulsion Pack has a game-breakingly efficient quad-grid ion engine. 12 of 'em + a KSP Interstellar nuclear reactor and a hitchhiker can gives a TWR of 0.43ish, making them suitable for single-shot transfers to darn near anywhere from LKO.

Really big (1918x994) picture

[SSSPutnik]

IRL though ion drives ARE very low thrust.

I tried moving a 300 ton ship with an array 13 ion drives.

If you are patient, you can do it, but it involves multiple orbital loops to break orbit, physics accel etc.

I think my max acceleration was 25mm/sec.

[The Destroyer]

300 tons?

...I thought using 20 nuclear engines to power a 300 ton ship was bad...

[DrMonte]

I've attached few Ion probes to my Jool mission ship. Few more kg wouldn't mind to those 100t.

Thinking of dropping them somewhere in the path.

[SSSPutnik]

Yeah I gave up, especially when physics acceleration ripped the ship to pieces.

Jebs in the massive crew capsule array awaiting rescue when government politics gets around to it.

[larsmaehlum]

I usually use ion only for long range, multi planet science probes. You can use the nuke for any other mission, really.

[SunJumper]

I normally only use ions when in solar orbit or beyond. They are normally fine for braking into orbit (except for Moho but including Gilly), but only into high orbits or where it will not take more than two passes to escape. I've even had success using them as far out as Jool...

[Hodo]

In general, Ion engines are only useful for the smallest of probes. However, the amount of DV you get is insanely high. Basically, if you want to do a transfer you are better off with chemical engines, unless you have a lot of time on your hands. Ion engines are good for things like changing the inclination of a probe. If you have a lunar satellite powered by an ion engine, you can set it up at almost any inclination you want, which is quite useful for things like satellite constellations. In short, ion engines are great for DV hungry maneuvers, but terrible for long burns

I beg to differ...

XI-3

9140d/V

.21:1 TWR on ion engines.

Javascript is disabled. View full album

XI-2

over 9600m/s d/V

.14:1 TWR on ion engines.

Javascript is disabled. View full album

If you have patience you can use ion engines to do a lot more than just probes. But they do work best on probes because they weigh very little and provide a great deal of d/V. But the biggest problem is the amount of electrical draw that the engines require is quite a lot and it can often overloads the typical recharging system of a the smallest probes.

[Geschosskopf]

Stock ion engines are incredibly weak and thus useful only for tiny things, station-keeping, etc. The Near Future mod's engines are usefully strong BUT also require vast amounts of electricity. As mentioned above, you can get around this with the totally overpowered reactors and such from the Interstellar mod, but that's just ridiculous. So I myself just use the power parts from Near Future itself. These make lots more juice than stock parts but WAY less than Interstellar. They're heavy enough to really limit the number of engines you can run with them, and this in turn still keeps ship size down. However, if you don't need a really huge ship, you can get quite a lot of use from these things.

For instance, Bop and Pol have such low gravity that you can use ion-powered landers for them. And if your main Jool base is at Laythe and you need to move Kerbals out to use the ion landers at Pol and Bop, you can make an ion-powered crew shuttle. You need to keep the total mas down to no more than about 6 tons to have any sort of reasonable burn times (5-10 minutes for transfers between Joolean moons). If you add more engines to increase the thrust, the added weight of the reactors needed to power them more than offsets the extra thrust. Still, within these limitations, such ion-powered ships are quite useful for such applications.

Shuttle for 4 Kerbals in lawn chairs, 6-ton, 4x Near Future ion engines, 2x Near Future mid-size reactors. Also shows transfer stage to get it from Kerbin to Jool. Can go back and forth between Laythe and Pol several times without refueling.

2-man, 4-ton lander with 1x Near Future ion engines and 3x small Near Future reactors.

Edited November 26, 2013 by Geschosskopf

[Anton P. Nym]

In my current "Sandbox" game save I have four ion-propelled probes; the first was a badly-underpowered Duna orbiter that still managed to brake into the desired orbit despite a botched transfer, two Jool fly-bys still en route (one of which swung by Duna on the way), and the most recent is a tiny probe to Moho that I"m hoping I can brake into orbit. (My conventional probe there, alas, just ran out of fuel and turned into a 5000km fly-by.)

On deck I have two more; an RTG-powered probe to Eeloo, and another (bigger) probe to Moho.

The trick to breaking orbit with ions is to do it in multiple passes; boost for 5-10 minutes around either the midnight (for outer planets) or noon (for inner planets) point of the orbit to extend the apoapsis a bit further each time until the window comes up, then make a longer burn. It's slower than a chemical rocket, but broken up that way it's not such a chore and it's more efficient.

-- Steve

[WafflesToo]

To ion or not to ion, that is the question.

A lot of it comes down to why you're playing the game; is it the journey or the destination?

If all you want to do is get somewhere quickly then they are not for you.

If you find some sick, perverse pleasure in the slow, building anticipation of making pass-after-pass, gradually coming closer and closer to escaping the clutching grasp of Kerbin' s SOI until finally being ejected out into the freedome of the solar expanses, free to roam wherever you will...

Excuse me, I need a cigarette.

[Tank Buddy]

I you plan on spending endless hours doing burns go ahead, but I would never use them for conventional purposes. I am actually just sending an Ion powered lander to Gilly for some fun. There it will function more or less like a normal engine.

Also, you can edit the thrust in the file, if you don't consider that cheating. If you do so, I would recommend increasing(!) the Isp because the engines draw more electric power per second with a higher thrust.

Edited November 26, 2013 by Tank Buddy

[e-dog]

They are useful for precision burns because of low thrust, for example putting a satellite in perfect synchronous orbit.

[little square dot]

Also, you can edit the thrust in the file, if you don't consider that cheating.

It's not so much a matter of cheating, 'cause it's mighty difficult to cheat in a single player game, rather it's eliminating the challenge.

As someone said, it all comes down to whether you're a journey or destination person.

Personally, I'm always on the wrong side of the fence.

During the journey I want the destination, and after arriving at the destination I instantly seek the next journey. Ah, the human condition...

[SunJumper]

I you plan on spending endless hours doing burns go ahead, but I would never use them for conventional purposes. I am actually just sending an Ion powered lander to Gilly for some fun. There it will function more or less like a normal engine.

Also, you can edit the thrust in the file, if you don't consider that cheating. If you do so, I would recommend increasing(!) the Isp because the engines draw more electric power per second with a higher thrust.

Decrease the electric-charge proportion and decrease the Isp by 100 to 200s to increase thrust in the most balanced way.

[Javster]

In the past I've used an Ion probe to perform propulsive capture and orbital manoeuvres around Eve, the closer proximity to the sun means less solar panels are needed to run the engine.

*fewer

But good to know.

[little square dot]

*fewer

?

Please tell me that you weren't correcting "less" to "fewer", haha...

The internet must be a very difficult place for you.