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Mass-optimal engine type vs delta-V, payload, and min TWR


tavert

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I could post up the best engine for a particular Dv in Eve atmosphere also as you can set the atmo multiplier when you generate (0-1 vac-kerbin sea level), is Eve sea level 2x Kerbin?

As I understand it, in the simulation the Isp for engines never gets worse than it is at Kerbin sea level, even if the atmosphere gets thicker as on Eve. Whatever is best at Kerbin sea level will also be best in thicker atmospheres.

Thanks for doing the work of updating these, John FX, they are a very useful reference. Rep++

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Ah, OK (now you mention it I remember that KIDS fixes that) so I`ll post up the 5 engine vacuum ones in the next day or three (have work tomorrow, long day). Is TWR=3 enough for Eve? It could be extended upwards if it is needed.

Asking that question made me realise that the charts should be measuring TMR (thrust to Mass ratio, not thrust to weight) as the weight depends on the body you are orbiting...

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I’m moving this thread to Add-on Releases: Tools and Applications since it’s a tool to help with planning for KSP.

tavert’s tool is subject to the Add-on Posting Rules, meaning that without a posted license, it’s assumed to be All Rights Reserved. The exception given in this post is very narrow – tavert allowed anyone to port the code to an open source language, but s/he already did that. That update brings us back to All Rights Reserved.

I’ll reach out to tavert to ask about a license. It hasn’t been all that long since s/he was last on the forums.

Short version: no posted updates until tavert says otherwise.

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This is a bit of an odd case. It's not the software itself that most people are interested in, but the charts it generates. It is a bit analogous to Kronal Vessel Viewer, the software is covered by a license but the images people generate with it are not. Should this be the same way? Should John FX be able to share the images he generates with the tool even if he can't redistribute the changes he made to the program?

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I’m moving this thread to Add-on Releases: Tools and Applications since it’s a tool to help with planning for KSP.

tavert’s tool is subject to the Add-on Posting Rules, meaning that without a posted license, it’s assumed to be All Rights Reserved. The exception given in this post is very narrow – tavert allowed anyone to port the code to an open source language, but s/he already did that. That update brings us back to All Rights Reserved.

I’ll reach out to tavert to ask about a license. It hasn’t been all that long since s/he was last on the forums.

Short version: no posted updates until tavert says otherwise.

Cool. I`ll carry on posting huge amounts of images until we get a say so from Tavert. I`m not sure many people are wanting the code anyway. I`ve not had a request on the forum or a PM about it.

As I said earlier, if anyone wants a particular set of charts, I can change the maximum number of engines, the TWR range and then depth into the atmosphere you are, from 0 to kerbin sea level.

I could even change the ranges that the chart shows meaning I could just show a detailed graph of 10-15T and 2000-3000Dv if there was a need.

I may figure out how to add extra variables to the input requester at some point but it`s easy enough to change the code directly, Tavert commented it quite well.

I have to go to a meeting now and work after that so I`ll not be posting anything until much later today at the earliest.

Are there any charts of interest to you Red Iron Crown?

One thing I plan is to make a set of charts for launches meaning a set for a TWR of 2 at sea level, about 1.6 at 20km, 1 at 40km (or thereabouts, not totally decided yet) to see whether it makes enough difference to bother with staging or just drop tanks.

I`m glad people will find the charts useful.

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John FX, could I get a link to the code you’re using, and if convenient a brief description of the differences from tavert’s April code? I’d like to add some mod parts and generate some charts of my own.

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John FX, could I get a link to the code you’re using, and if convenient a brief description of the differences from tavert’s April code? I’d like to add some mod parts and generate some charts of my own.
I’m moving this thread to Add-on Releases: Tools and Applications since it’s a tool to help with planning for KSP.

tavert’s tool is subject to the Add-on Posting Rules, meaning that without a posted license, it’s assumed to be All Rights Reserved. The exception given in this post is very narrow – tavert allowed anyone to port the code to an open source language, but s/he already did that. That update brings us back to All Rights Reserved.

I’ll reach out to tavert to ask about a license. It hasn’t been all that long since s/he was last on the forums.

Short version: no posted updates until tavert says otherwise.

Sorry it would seem not, you could try to get in touch with Tavert, if he says yes then it will be fine. All I did was to download the code already available on this site and change the values to match the current engine stats. No other changes except to uncomment a few engines. It would be very easy to duplicate it.

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  • 3 weeks later...
  • 3 weeks later...
  • 3 weeks later...

Here are the charts for a single engine in vacuum

Javascript is disabled. View full album

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Fantastic, John FX. You should consider starting your own thread when 1.0 drops with all its revised part specs, just to have the charts in an easily-found OP.

I've considered it but I don't want people to think anyone but Tavert did all the hard work. Might be cleaner though, especially if the engines have a balancing pass and all the stats change...

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Here are the charts for atmosphere and a single engine

Javascript is disabled. View full album

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Just make sure you credit tavert and link to this thread, you're the one carrying on the work s/he started (this happens all the time with mods).

I wonder how much the code will have to change to accommodate varying atmospheric thrust.

Probably more than I would be able to do, luckily Taverts code is well documented so just changing values for the engines is easy. I'm not familiar with Julia so anything much deeper than that would probably not happen through me. If the code is fairly easy I may have a go though saying that.

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@taio in case it's helpful, here's a dumb cfg file parser in 30 lines of Julia code that I wrote a while ago: http://www.reddit.com/r/KerbalSpaceProgram/comments/23nxde/mass_optimal_engine_charts_updated_for_0235/ch0teog

Consider that released under the same BSD license. Someone on reddit did some work to put in RCS engines and automatically put the thumbnail engine pictures into the legend, they contacted me via PM on reddit a while back and their modifications to the code are on github, but I don't think they finished them. There were also some bugs in the way they did fuel-tank combinations, they tried to dynamically compute the list of combinations based on stats but were doing it incorrectly.

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Also to taio and John FX, it would be nice if you could keep track of and collaborate on your updates/modifications to the code via a github repository. Easier to review and spot anything that might be incorrect that way.

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I wonder how much the code will have to change to accommodate varying atmospheric thrust.

That should be pretty easy. Just scale the right hand side of any line that says "thrustk = ..." by whatever function of "atmpressure" ends up being used in-game.

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Myself all I have done is to hardcode the new engine values into the code. I was unable to add new engines or remove any without breaking the code. If taio is making a new version that scans the .cfg files that would be great.

I`m OK with logic and maths but I am not familiar with julia coding/syntax.

I`ll post the code I have changed here for anyone that wants to use it.

http://www./download/oeo3ejfnn8zezit/KSP_engine_charts.jl

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@taio in case it's helpful, here's a dumb cfg file parser in 30 lines of Julia code that I wrote a while ago: http://www.reddit.com/r/KerbalSpaceProgram/comments/23nxde/mass_optimal_engine_charts_updated_for_0235/ch0teog

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Also to taio and John FX, it would be nice if you could keep track of and collaborate on your updates/modifications to the code via a github repository. Easier to review and spot anything that might be incorrect that way.

Initially I was just modifying your code by adding a CFG parser behind it, but that turns out to be non‑trivial (wacky syntax like @PART[engineLargeSkipper_125m]:FOR[RealismOverhaul]:NEEDS[!RftS,!RealFuels_StockEngines], and also because the CFG format is tolerant of lots of strange inconsistent formatting that people use and I therefore need to tolerate). I decided Julia lacked enough language features that I would have an easier time rewriting from scratch in Python. The CFG parsing is ~70% done and the actual engine optimization is ~15% done. I’ll probably put it on github at some point. (I did the majority of the work for this a month or two ago, but it’ll eventually get done.)

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