The Use of Ion Propulsion?

[farthen]

Ion engines are great! They have this nice blue glow on them. Justifies everything else. Also they make no noise. I hate noise.

Seriously though, they are great for small probes and not so great for big probes. And they weigh basically nothing which makes them easy to just tuck on your probe in case you want to change its orbit later. They may not be the best engines to get into a Moho capture but they work great once you are in orbit.

Did i mention they have this nice blue glow on them? It even flickers when they don't have enough power. Looks so awesome.

[WhiteWeasel]

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

Had a good time at jool with my ion probes. If you want to mess with my design, the craft. is in the thread I made. They're really light so the burn times are (relatively) fast. It was pre.21 so you may have to alter the design some. http://forum.kerbalspaceprogram.com/showthread.php/35878-MLAS-Presents-The-Deep-Space-Splitter

Edited July 25, 2013 by WhiteWeasel

[Anton P. Nym]

I'll have to try your designs out, tweaked of course because I'm a mad tinkerer with this stuff.

Another thing you can do with ion engines:

It's a prototype for a solar-boosed glider probe for exploring Eve by air. The ions aren't there really for power, but to "kick" the glider when I need to turn or gain a little altitude. In that form it had a better than 10:1 glide radio (goes 10km ahead for every 1km altitude lost) on Kerbin thanks to the boost, even with me stalling it a couple times... the v0.21 cut looks to be better, given that there's a quad-adaptor now that's lighter than the 3x dual-adaptor kludge I used before.

-- Steve

[Horn Brain]

In career mode they will let you achieve missions to orbit Moho and other dV-intensive missions for very cheap (even if they do cost three mainsails, you can launch one with one big SRB, some fins, and a small tank with an LV-909 on it and get at/near Kerbin escape velocity). This will probably be a good way to earn a lot of money quickly.

Right now, they are good for the same purpose. If you're sending a mission to Moho, Dres, Eeloo, or even Jool, they are super easy to get the required dV (solar panel effectiveness does not drop off as 1/r^2, so with six of the six-pane solar panels you can still use them out at Jool). You can even do Gilly sample return missions with them since they can land on Gilly.

If your burn times are days-long, then you're doing it wrong. Just use the lightest probe, and use the six-pane solar panels (NOT the gigantors, those are too heavy), along with a few instruments and antennae and one tank of Xenon and one ion engine. That should be able to go anywhere in the game from LKO. Just use 4x time warp and make sure you put your solar panels on in such a way that you can face the Sun with them when doing your burns and the time should be less than five minutes for any burn that isn't ridiculous (like Moho capture). Also, make sure you can do your burns on the day side of wherever you're going.

[Max Grant]

Ion engines would be more realistic, and fun, if you could program their burn to last over a long period of time, like days, and then time-warp them without using the limited physics warp.

It would require a completely different bunch of code to do that which I imagine won't happen at least any time soon, but the real value of the ion engine is that it can burn not for hours, but for YEARS on very little fuel. So you have to program the trajectories over a long period of time. That's more than this game is set up to do, currently, and I can understand why.

Check out the trajectory of the Dawn probe, which is what I think the Kerbal ion engine is modeled after. In particular, look at the "thrusting" vs "coasting" lines. Those burn times are GIGANTIC.

[lammatt]

for changing inclination of your probe?

[Anton P. Nym]

In career mode they will let you achieve missions to orbit Moho and other dV-intensive missions for very cheap (even if they do cost three mainsails, you can launch one with one big SRB, some fins, and a small tank with an LV-909 on it and get at/near Kerbin escape velocity). This will probably be a good way to earn a lot of money quickly.

As I have a Moho launch window approaching in 25 days I've decided to give something like that a try.

I call it... MiniMoho. A plain old OKTO with 8 solar panels, two of the small radial batteries (two for load balancing), all the "science" instrumentation, antennas, and a single ion engine with one canister of xenon. It's on a two-stage booster: first stage an FL800 tank with LV-T30 engine and four tailfins with small control surfaces, second stage an FL-T400 tank with LV-909 engine and two Sepatrons pointing retrograde to deorbit it after separation.

I launched it into a 1000km x 30km orbit, apex at noon, then used 60s of ion engine at full thrust to convert to a 1000km x 100km orbit. That started to eat into batteries because the burn orientation led some of the panels to mask others, but that's what batteries are for, right?

I've got some other missions on the go now, so I won't timewarp to the window, but it'll be interesting to see if it can get there when my more conventional probe boosts in the same window with an LV-N transfer stage... which is a heckuva lot pricier than MiniMoho.

-- Steve

[KerbMav]

Also they make no noise. I hate noise.

Actually I would like to have them make a low humming sound - is there a sound mod out there or a way to make one?

Also a power distribution node would be handy - something that controls the flow of electric energy and makes sure that either all active engines receive power or none - no more midway swings to the left during long battery supported burns!

[Anton P. Nym]

Did a quick tally of the game-currency cost on MiniMoho last night; it's just south of $25 000 (kerbucks). That's about the cost of the first stage of my chemical/NERVA fuelled mission; though the ion engine may cost like 3 Mainsails, the xenon tank costs about 1/6th of a Rockomax big orange tank.

If MiniMoho works, and that is admittedly a big if, it'll be vastly cheaper overall than sending a conventionally-fuelled orbiter to Moho.

-- Steve

[Horn Brain]

Did a quick tally of the game-currency cost on MiniMoho last night; it's just south of $25 000 (kerbucks). That's about the cost of the first stage of my chemical/NERVA fuelled mission; though the ion engine may cost like 3 Mainsails, the xenon tank costs about 1/6th of a Rockomax big orange tank.

If MiniMoho works, and that is admittedly a big if, it'll be vastly cheaper overall than sending a conventionally-fuelled orbiter to Moho.

-- Steve

Good luck, and I hope it works for you. One thing I'll tell you is that you don't need 8 solar panels, just 6 (even at Kerbin, unless the solar panels got nerfed since I did this an admittedly long time ago). Also, if you arrange them around the pitch or yaw axis of your spacecraft instead of the roll axis, they are easier to orient towards the Sun (because you can roll the spacecraft while maintaining a constant heading, so unless you're burning right at the Sun or away from it, you can always have nearly full exposure).

Edited August 2, 2013 by Horn Brain
added caveat in case solar panels were nerfed

[Horn Brain]

Also, when you get to Moho, check the burn time and start early because you will be burning for a while. That's a long burn. I actually think that when I did it, I went around the Sun a few times and brought my aphelion down to Eve's orbit or lower before my encounter with Moho so it would be less dV.

[Amoun]

, and ion engines are all about veeeeeeeeery long burns.)

-- Steve

Yeah............................I experienced that once. Was doing an experiment and had a burn of 1 year and whatever months....

[johnnyhandsome]

They can work for optimizing YOURSELF. Set up an ion burn that lasts 8-10 hours and you can let it do its thing while you're sleeping. WIN WIN. But otherwise, yeah, not very useful.

[cmoody]

I use it for long-term probe missions and efficient/low-part/low fuel missions when I have the time. Takes forever to get anywhere, though.