Pre-second cup of coffee thought (ion engines)...

[Foxster]

Not quite awake here but was just reading about ion engines and had a thought...The pain with them is the huge electricity requirements. This makes scaling up their use pretty impractical.You run out of room for solar panels.

But many other engines generate electricity. Would it make any sense to have a light engine with high vacuum ISP ticking over to generate electricity to power ion engines?

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Only slightly more awake...forgot that we have one throttle control, so couldn't have a liquid fuel engine ticking over and the ions on full blast.

Edited January 24, 2015 by Foxster

[Postron]

You could actually thrust limit the liquid engine. But usually solar panels + girders will be far more weight efficient than liquid engine + liquid fuel at providing electricity and the amount of additional dv you'd get out of the liquid engine would be negligible compared to the ions dv (unless that would have been ruined by all that additional weight from the liquid engine).

[John FX]

Yup, lighter, cheaper and better to use solar panels or NTGs if you are going far out in the system.

[KerikBalm]

The closest I've come is doing burns in relatively small craft with a pair of ions and an LV-N.

I'm pretty sure if you thrust limit them, then the electricity generated is proportionately decresed.

I'v experimented with making the LV-N be able to switch modes (like the rapier), but one of the modes has a ridiculously strong alternator + tiny tiny tiny tiny thrust + very very high ISP -> so that its basically no longer an engine, just a generator.

The small engines don't have alternators... I think the LV-N provides the most electrcity output per unit fuel consumed... and its not even enough to power 2 ion engines.

So.. in stock... its not practical

[Red Iron Crown]

That's interesting KerikBalm. I've wanted a bimodal NTR for a while, a nuclear rocket engine that continues to provide electrical power when throttled off and not consuming propellant.

Foxster, I agree with the other that it's not worthwhile. The additional mass of the LFO engine and fuel tanks will outweigh the savings from not needing a conventional electrical system.

[Foxster]

That's interesting KerikBalm. I've wanted a bimodal NTR for a while, a nuclear rocket engine that continues to provide electrical power when throttled off and not consuming propellant.

Foxster, I agree with the other that it's not worthwhile. The additional mass of the LFO engine and fuel tanks will outweigh the savings from not needing a conventional electrical system.

Ah, you are probably right, but I gotta build it to be sure. Its being an engineer, if you aint spannered it yourself, it aint true

[Red Iron Crown]

By all means, I don't mean to discourage experimentation. For science!

[Tank Buddy]

The added mass would effectively eliminate the advantage of the Ion engine's efficiency. The wiki is down right now, but there is a page that gives the amount of electric charge per second generated from the alternators in various engines. I'm afraid none of them (accept the skipper or mainsail) generate enough power to run an ion engine. You are much, much better off using solar panels or RTGs.

[stibbons]

I kind of want to try this with generators from modpacks now, like the Karbonite generator, just a little box that burns fuel and produces power.

[Streetwind]

That's interesting KerikBalm. I've wanted a bimodal NTR for a while, a nuclear rocket engine that continues to provide electrical power when throttled off and not consuming propellant.

Foxster, I agree with the other that it's not worthwhile. The additional mass of the LFO engine and fuel tanks will outweigh the savings from not needing a conventional electrical system.

Bimodal NTRs (among other things) were in the works for Near Future... either a new NTR pack, or as part of Propulsion. I was also looking forward to them!

Unfortunately, Nertea then got swallowed whole by IRL troubles =/ So this probably won't happen until after KSP 1.0 at the least.

On topic: the problem with stock PB-IONs is not that they consume so much Ec/s (they really don't), but rather that stock doesn't offer you good energy production tools. The gigantor array is actually really really bad. It weighs more than twice as much per unit of Ec produced as the normal 1x6 panels. Unfortunately, using the 1x6 panels isn't a great idea either, because then your part count goes way up... which it is already doing, because you only have tiny xenon tanks, so you need to bring many of those as well.

I recommend Near Future Solar to add sensible large panels to your game so you can keep part count down and still power your ion drives

[Dispatcher]

I agree that bimodal NTRs are the way of the future ... for interplanetary travel (in real life, hopefully). Back to ion engines; another possible engine to pair them with is the aerospike; depending on the mission.

[LordFerret]

I've built a few Ion craft, small scale stuff, worked quite well. The large scale ventures hit similar problems as mentioned, power, and part count. I'd like to venture more into Ion craft, but I'm deterred without access to larger Xenon tanks.

[Streetwind]

Weeeeell...

<Insert more shameless Near Future advertising>

[GoSlash27]

The solar panels, batteries and supporting octagonal struts are effectively free from a mass standpoint since they have no physics significance.

They will up your part count and increase your chances of a Kraken attack, but of course this is why we don't use ions for large jobs.

Best,

-Slashy