Ion Engines, Good or Bad?

[Mr_Kerbal]

After recently sending a probe to the Mun, I have came across some issues regarding the Ion Engine, but rather than list everything bad about it, I've decided to turn this into a conversation. What are your pros and cons of the IX-6315 "Dawn"? Please feel free to post your opinions on this topic below! 

- Mr_Kerbal

[Spaceception]

22 minutes ago, Mr_Kerbal said:

After recently sending a probe to the Mun, I have came across some issues regarding the Ion Engine, but rather than list everything bad about it, I've decided to turn this into a conversation. What are your pros and cons of the IX-6315 "Dawn"? Please feel free to post your opinions on this topic below! 

- Mr_Kerbal

Erm... Is this supposed to be a Science topic?

[Mycroft]

I like them… for small scale satellites/probes only. They have amazing efficiency at extremely low power. This is a pro/con in and of itself. If you want to use them for any thing larger than about (I think) 10 tons, you have to use prodigious quantities of them, mitigating their efficiency. I think tis is about as far as pros/cons go, honestly. Please feel free to correct me if this post is inaccurate or insufficient.

[Temeter]

On 28.4.2016 at 1:33 AM, Mycroft said:

I like them… for small scale satellites/probes only. They have amazing efficiency at extremely low power. This is a pro/con in and of itself. If you want to use them for any thing larger than about (I think) 10 tons, you have to use prodigious quantities of them, mitigating their efficiency. I think tis is about as far as pros/cons go, honestly. Please feel free to correct me if this post is inaccurate or insufficient.

If you want more modern - including theoretical - methodes of electric pulsion, also on larger scale, i'd recommend Near Future Propulsion:

It's a very nice enhancement to KSP's lategame, much more interesting than just spamming huge, nuclear motherships.

Edited April 10, 2017 by Temeter

[PB666]

The ion drive in KSP is 1000 times more pwerful than RL, it delivers 2000 N of thrust, and the electrical generation capacity of KSP is nerfed. I have modeled my own drives based on the most high powered stuuf. 

 

Let me share my conclusions. 

1. for human space travel, unless there are fusion drives that produce 10 to 100 times the power to weight ratio of solar electric power, the ion drive is nothing more than a interstellar ressuplly drone. 

2. ISP is at the direct mercy of power consumption, for any given power absolute, increase of ISP cause an inverse reduction in thrust, increase in thrust causes a proprtionally rapid use of fuel. 

3. If electric power is unlimited, that means if you could use matter, antimatter to power the ion drive, for every gram a mass consumed, it is efficient to propell also 1 gram of matter and 2 grams is not inefficient either. Thus the best you can hope for with a gram sized payload is something around 0.7c and start stop about 0.3 c. But acceleration is at the expense of payload, so ion drive can never be anything more than a genertaional ship propulsion system. And btw the most credible system at present. 

[Renegrade]

It makes for some crazy efficient Minmus landers, which is ridiculous...but also fun.

[LordKael]

2 minutes ago, Renegrade said:

It makes for some crazy efficient Minmus landers, which is ridiculous...but also fun.

I use Ions to cart Kerbals around outposts on Minmus, as well as to my Orbital Station and back

 

[Renegrade]

1 minute ago, LordKael said:

I use Ions to cart Kerbals around outposts on Minmus, as well as to my Orbital Station and back

 

Yeah, it works really well.  After I ravaged Minmus for it's juicy return-to-KSC science in my "Eleventy" save (have yet to ravage it in "Eleventy Hard" - just NOW bought resource transfer), I created this to fuel the MPL around Minmus with science:

(Upper left: taking off from a flat.  Upper right: adjusting the station's orbit a bit (PE was a bit low).  Lower right: I believe that was an orbital maneuver to lower the lander's PE in preparation of a landing.  Center: Just a detail shot)

The screenshot was actually an illustration for someone else, but I might as well use it here again (spent the time on it, might as well share it).  This is crazy overpowered nonsense (especially when paired with the MPL), but it's actually kinda fun to build these things.  This particular unit has enough electric charge stored for about 210 delta-v with no solar power, and something like 1700 delta-v overall.  The TWR is a bit low (4.1 vs Min's grav), but not much lower than a triple-ant lander (about 6.5:1).  The downside is that it's almost twice the price (50.6k vs 27.85) and actually somewhat heavier (2.0t vs 1.8t).

Again, these are ridiculous to the point of #lolfake, but it's still a fun exercise to design.  Plus the new(ish) ion glow is neat.

Next time I might build one that's basically an EAS seat on a Science Jr, but I suspect that might miss out on the internal "crew report" science (which is the least valuable one... hmm).  I'd also be building less fake chemical versions of that too

[N_Molson]

Those engines are excellent, provided you have the patience (and the tools at some point) to plan efficient trajectories with them (like spiraling to escape Kerbin SOI). The limit is that you can't use time warp which engines on, which ruins a bit the purpose of those. JAXA probe Hayabusa was powered by 4 of them running almost all the time. In a few years, it managed to make a soft touchdown on an asteroid, then drop a (alas empty) sample reentry capsule into Earth's atmosphere. Though there were reliability problems, (the probe finished the mission crawling with 1 damaged engine and 3 out), it showed how capable are those little technological wonders.

Edited April 28, 2016 by N_Molson

[Renegrade]

7 minutes ago, N_Molson said:

TThe limit is that you can't use time warp which engines on, which ruins a bit the purpose of those.

Well, you can hold down ALT (or specifically "Meta" -> varies per type of KSP installation.  I believe it's shift under Linux) and press the warp keys to force a physwarp, which DOES let you run the engines..but only upto 4x speed.

(also good for chemical or NTR craft with bad TWRs)

It's not the same as a real drive, but it can cut down on the waiting.

Edited April 28, 2016 by Renegrade

[Temeter]

1 minute ago, Renegrade said:

Well, you can hold down ALT (or specifically "Meta" -> varies per type of KSP installation.  I believe it's shift under Linux) and press the warp keys to force a physwarp, which DOES let you run the engines..but only upto 4x speed.

(also good for chemical or NTR craft with bad TWRs)

It's not the same as a real drive, but it can cut down on the waiting.

20+ physics timewarp? Maybe also lossless, assuming your PC can handle it? Here you go:

 

 

[Hysterrics]

It's an amazing engine, but needs to be toned down a little. Actual Ion engines aren't nearly this good.

[Temeter]

13 minutes ago, Hysterrics said:

It's an amazing engine, but needs to be toned down a little. Actual Ion engines aren't nearly this good.

Lots of things in KSP aren't nearly as good in reality. So if you don't want to accelerate for 5 years to go interplanetary, i'd recommend keeping things that way.

[mrclucks]

1 hour ago, Hysterrics said:

It's an amazing engine, but needs to be toned down a little. Actual Ion engines aren't nearly this good.

But real life also has computers to plan out and moniter every single manuver that are specific to each engine.  KSP's manuver nodes assume an instantaneous burn instead of a burn that takes hours.  If Ion engines were to be nerfed then burns would take days and would be drastically different then what was planned

[Archgeek]

Ions are hecka great if if you've got a life support mod or otherwise have need of using a non-Hohmann trajectory to get somewhere fast.  I've saved hours on end on a Minmus transfer back to Kerbin from a minutes-long burn.

[Foxster]

Ions are my favorite way to get about in KSP. They force you to think small and efficient but can result in some great craft. I just did a manned Kerbin to Eeloo surface and return challenge mission with a craft that was 78t at launch.  

[RocketBlam]

They're fun for interplanetary, small orbiters, but not much use beyond that.

When the physics of light were changed a few updates back, they really lost usefulness past about Dres. There's just not enough light out there to power them without a lot of panels. But that's the way it is in real life too.

[Foxster]

9 minutes ago, RocketBlam said:

They're fun for interplanetary, small orbiters, but not much use beyond that.

When the physics of light were changed a few updates back, they really lost usefulness past about Dres. There's just not enough light out there to power them without a lot of panels. But that's the way it is in real life too.

That's why fuel cells are so useful. 

[Streetwind]

I love myself some electric engines.

...Why, what gave it away?

[Fluburtur]

I like them, one gigantor solar array is enough to power one ion drive up to Duna, after that not so much.

Trust me, I tried an orbital insertion around Jool with two drives running at 0.2kn each.

[DunaRocketeer]

I currently fly a 10 ton Mun lander using 4 Dawn's and 2 terriers. It can transport rovers and cargo in its service bay. It'll go from LKO > Munar Surface > LKO without refueling.

 

Ions are awesome.

[Boganaut]

I've found them excellent as main drives for small probes.

I also designed an Eve space station with 4 of them attached for orbital adjustments and as a backup in the event the attached ship ran into any trouble. And boy there was trouble! Most of the structure blew up during a bad aerobraking manouvre... But most Kerbals survived and 2 gigantors were nicely protected also. Only one ion engine survived well off the craft's centre of mass, but being such low thrust, the inline stabilsers were more than capable of countering the torque. That single ion engine enabled the ricketty remains of the spacecraft to achieve a stable orbit.

[RizzoTheRat]

Take a look at some of Cupcake's ion powered designs, they're beautiful

 

 

[Red Iron Crown]

Pros:
- Most efficient engine in the game
- Relatively easy to pack large amounts of ΔV into a single stage
- Doesn't suffer from exhaust blocking, which you can exploit by putting them in stacks or inside cargo bays for use (totally cheating )
- Cool blue glow when running

Cons:
- Low thrust means more careful planning of maneuvers is needed
- Supporting electrical system can add significantly to dry mass, especially if operating in the outer system where solar panels don't work well
- Totally useless in any significant atmosphere
- Only available in a tiny size, on large ion-powered ships the part count goes nuts

[Servo]

Another relevant con (if you're playing career) is cost. That is, unless you have several trillion funds. Otherwise, Ion engines are amazing for anything less than 5 tons and good for anything less than 10.