PB-ION engine thrust observation

[dudester28]

I don't really use the ion engine that often but there is something highly unrealistic about the thrust that I noticed.

It is WAY too high compared to its real life counterpart.

Its thrust is 0.5 kN which translates to approximately 50kg. In real life, an ion engine would have less push than a piece of paper held in one's hand. I'm not saying that KSP should modify the engine, I just realized how much more thrust it produces comparatively.

[Mokmo]

it can also burn for weeks at a time without problems...

[Levelord]

it can also burn for weeks at a time without problems...

Maybe the OP wants to run his PC for weeks on end simulating a real ion engine.

Everything in KSP has been scaled down in the interest of time. Kerbin is a fraction of the size of the Earth and the relative distance of the orbits of the Mun compared to our real moon, is scaled down. The ion engines have been scaled up for this purpose of not giving the player an unreasonable burn time for a game.

[rodion]

Yeah, it's amusingly over-thrusty compared to any real-world ion engine, which also makes it all the funnier when impatient players complain about their burn times.

[Levelord]

Yeah, it's amusingly over-thrusty compared to any real-world ion engine, which also makes it all the funnier when impatient players complain about their burn times.

To be fair, there's nothing to do during a 45 minute burn. So I can understand why players get bored when there's nothing significant happening the better part of an hour.

[NoMrBond]

[alt] + [>] for physical time acceleration, reduce your 45 minute burn to just over 11 minutes at 4x PTA, slightly more tolerable

[dudester28]

Maybe the OP wants to run his PC for weeks on end simulating a real ion engine.

Maybe you misunderstood what I said. I never said I wanted to do week-long burn times. I just observed that the Ion engines produce much more thrust than in real life.

If anything, perhaps there should be faster physical time warps for situations like 45 minute burn times.

[WafflesToo]

[alt] + [>] for physical time acceleration, reduce your 45 minute burn to just over 11 minutes at 4x PTA, slightly more tolerable

Took the words right out of my mouth.

[PwnedDuck]

Now try passing a week like that. 1.75 days. I think my laptop would crash before that time passed, and at the very least the SAS would begin to drift of course, so you'd need regular course correction over that time too...

[SeventhArchitect]

Why do you even care? So far, the PB-Ion engine seems overly under-powered to me, even if it's supposed to be a very, very weak engine in reality. Given that when in a vacuum, unaffected by air-friction, it's a valued piece of technology, but there is also the bigger question of WTF would one want an engine to be that weak?

Now, I will get to the point about this engine specifically. It's electric, and requires Xenongas. Of the two, Electricity is needed a lot more.

I basically got tired of being unable to use an engine so weak, so I modified the Pb-Ion engine myself, and now it's become one of my most useful thrust producing parts yet.

All I can see, is you people bickering over the stupid fact that it's stronger than it really should be in real life, and I already questioned WHY you would want that corrected. I guess I could ask what exactly could it be put on if so weak, and actually even work at all? Cause last I checked, this ghost engine barely moved a 9 part tiny satellite, and in real life, "can barely move a piece of paper."

why even bring it up?

[stupid_chris]

Guys, you do know that OP never meant to say he wants it to be changed in the game?

I don't really use the ion engine that often but there is something highly unrealistic about the thrust that I noticed.

[...]

I'm not saying that KSP should modify the engine, I just realized how much more thrust it produces comparatively.

So can we stop getting angry about how having an engine as powerful (or powerless) as real ion engines would make the game terrible and discuss what OP meant to talk about? Thanks.

[Scotius]

Well, in RL we are getting closer. NEXT thruster can reach 0.2 N of thrust. Early VASIMR prototype could give 0.5 N of thrust.

[leax256]

I made a few modified versions that had like 100x thrust but required 1000x power, I also modified a thermo generator into a fusion generator to get decent power.

[Levelord]

Maybe you misunderstood what I said. I never said I wanted to do week-long burn times.

I know, I'm just poking fun

[WafflesToo]

The trolls come marching one-by-one

Hurrah, Hurrah

The trolls come marching one-by-one

Hurrah! Hurrah!

[lazarus1024]

I don't really use the ion engine that often but there is something highly unrealistic about the thrust that I noticed.

It is WAY too high compared to its real life counterpart.

Its thrust is 0.5 kN which translates to approximately 50kg. In real life, an ion engine would have less push than a piece of paper held in one's hand. I'm not saying that KSP should modify the engine, I just realized how much more thrust it produces comparatively.

Only if we are talking about a really heavy piece of paper. We are still talking about a hundred milinewtons or so of thrust for your typical and the VASMIR prototype that is going up on the ISS I think is more like 1-2N.

That is still very, very little, but that is more than a piece of paper. The VASMIR is more like a thick notebook. A typical ion engine is more like an empty folder.

However, thrust that tiny would be worthless in KSP, at least or unless they add in higher levels of physics warp.

.1N of thrust even at 4x would take hours of game play time to meaningfuly increase the velocity of a probe. So it is fudged. A lot more fun fudged.

[sporkafife]

There was plenty of discussion about the time of the release of the ion engines discussing the fact that they had to be souped up for gameplay purposes. I personally think the only problem with the ion engines at release was the fact that there used to be only one type of Xenon container... and I still think the game could do with a couple more

[CreepyD]

I think a better fix would be for the team to find some way of allowing the ion drive to be thrusting and still allow normal time acceleration.

Ion drives would need to be a different system to normal drives the way I see it, and the acceleration be worked out in a more 'bulk' fashion in order to work game-wise with time acceleration pushed up in the x1000's.

[CoolBeer]

About the DAWN space vehicle:

According to [1]: "Each of our three ion engines weighs in at 20 pounds and is about the size of a basketball".

According to [2]: "Dawn's engines have a specific impulse of 3100 s and a thrust of 90mN."

So we do 20 pounds to kg = 9.07185

And thrust/weight = 0.090 / 90.7185 = 0.00099207989 TWR (Under the assumption that 10N is 1kg, which is close enough).

So about 9grams of force pushing on a 9kg engine.

(This is of course on earth/kerbin, you'll get movement in space... eventually).

[1] http://www.jpl.nasa.gov/news/news.php?feature=1468

[2] http://dawn.jpl.nasa.gov/mission/ion_prop.asp

-

Kolbjørn

(If I goofed up in my math, I'm happy to be corrected).

[SeventhArchitect]

Pb-Ion engines just looks so damned useless when you haven't modified them. But like you had said, leax, it's good to modify the engine. Heck, I modified mine twice, once from 0.5, to 60, then to 120, when I realized it was still a very useless engine with 60 thrust. I mean, just the rig made to carry the engine itself (I've made a canon part collection of it), requires one of those M-Beam 650 I-Beam parts on a small hardpoint, then I attach a standard NC to the top of the structural piece, a xenongas tank to the bottom, and a ghost engine behind that. I could then either use a lot of singular panels to supply the power, or with the mods I use, a nuclear reactor and thermal generator, or microwave dish receiver.

[WafflesToo]

What's the problem with it as it is? I've flown dozens of flights with it just fine without hacks and cheats.

If you don't like it then just stick with the LV-N.

[Captain Sierra]

PB-ION is a great engine for interplanetary travel. It's high ISP and low thrust mean very accurate burns and insane efficiency provided power. Now, when it comes to inserting them into a low orbit, where it takes notably more delta V to make the same change in altitude, then it struggles.

SOLUTION:

Use a standard chemical engine to break Kerbin SoI and set up the intercept.

Use ion engine as interplanetary stage for fine tuning.

Have another stage with smaller chemical engine or a nuke to circularize if low orbit is planned.

With that, you can take advantage of an ion engines strengths and avoid it's weaknesses. The real best way to use it though is avoid low orbits entirely to avoid having the extra stage for efficient circularization.

[dudester28]

Interestingly, people are interpreting my thread as one that is criticizing the engine. I think it's a good engine. I just made an observation.

[WafflesToo]

Believe me... yours wasn't the opinion I was criticizing