[1.12.2+] Eve Optimized Engines v3.0.2

[MaxL_1023]

How will these perform under 7-10 atmospheres of pressure? (Thinking Tellumo Coastlines, etc).

[JAFO]

4 hours ago, OhioBob said:

the 48-8S "Asp" and the Mk-56 "Boa".

Hmm.. I smell a teensy bit of influence from the Elite universe.. kudos.

[OhioBob]

4 hours ago, MaxL_1023 said:

How will these perform under 7-10 atmospheres of pressure? (Thinking Tellumo Coastlines, etc).

Thrust and specific impulse follow linear functions (or at least very close to linear taking into account a small amount of rounding).  So you should be able to easily extrapolate the performance out to any pressure.  For instance, the Viper has an Isp of 279s in a vacuum and 236s at 5 atm, so that works out to Isp = -8.6*P+279.  So at 10 atm pressure we have, Isp = -8.6*10+279 = 193s.

Although linearity is true in real life, this is not the case in the stock game.  It is true, however, in this mod.
 

Edited December 11, 2016 by OhioBob

[MaxL_1023]

Thanks. I was confused due to the game's non-linear thrust curve.

[OhioBob]

27 minutes ago, JAFO said:

Hmm.. I smell a teensy bit of influence from the Elite universe.. kudos.

I'm afraid I'm not familiar with the Elite universe.  If there is any connection between it and the names I used, it is completely coincidental.  I used snake names as a reference to the biblical Eve and the story if her being deceived by a serpent in the Garden of Eden.  The Adam and Abel names also come from the story of Eve, Adam being her husband and Abel her second son.

[OhioBob]

9 minutes ago, MaxL_1023 said:

Thanks. I was confused due to the game's non-linear thrust curve.

You can also go into the cfgs and check out the atmosphereCurve.  It gives the ISPs at pressures of 0, 1, 5 and 10 atm, as well as the pressure at which the ISP goes to zero.  Although it is not exactly a straight line, you should be able to interpolate and get real close.

[JAFO]

39 minutes ago, OhioBob said:

I'm afraid I'm not familiar with the Elite universe.  If there is any connection between it and the names I used, it is completely coincidental.  I used snake names as a reference to the biblical Eve and the story if her being deceived by a serpent in the Garden of Eden.

Ah.. that explains it.. all the roughly two dozen or so types of space ships in the Elite universe are named after snakes. It's quite a good game for its time (1984). Should you be curious to learn more, you can check it out here.

[Marsh]

This is really cool. Any way you would consider adding the Rhino/Mammoth in a future update for those of us who go ~really~ big?

[OhioBob]

On ‎1‎/‎16‎/‎2017 at 9:51 PM, Marsh said:

Any way you would consider adding the Rhino/Mammoth in a future update for those of us who go ~really~ big?

I currently have no plans to do that.  First off, the Rhino is really no improvement over the Mainsail.  A modded version of the Rhino would have nearly the same Isp curve as the Mainsail, would produce only about 20% more thrust, but weigh 50% more.  I think you're better off using the Mainsail.  Although a modded version of the Mammoth could provide very good performance on Eve, it's already one of the best of the stock engines.  I'm also trying to stay within the narrative of the game and limit the manufacturers that have gotten into the Eve engine business.  I've already got Jeb's Junkyard & Spacecraft Parts and Rockomax in the business.  I think it's too small of a niche market for a third manufacture, Kerbodyne, to jump in - they could probably never recoup their investment.  You'll just have to use clusters of Mainsails.

[OhioBob]

Eve Optimized Engines, version 1.2.0 works with KSP 1.3.

[linuxgurugamer]

I understand that you aren't a modeler.  So, the one thing that bothers me about this is that the size of the nozzles are wrong (which you've acknowledged).  I have a proposed suggestion which will make it appear a bit more realistic:

Use the scaling factor to make them longer, that way they will appear to have a narrower nozzle.  So, using the LV-T45 as an example:

Current code:

	mesh = model.mu
	scale = 0.1

Identical results using new MODEL node code:

	MODEL
	{
		model = Squad/Parts/Engine/liquidEngineLV-T45/model
		scale = 1,1,1
	}
	node_stack_top = 0.0, 7.21461, 0.0, 0.0, 1.0, 0.0
	node_stack_bottom = 0.0, -5.74338, 0.0, 0.0, -1.0, 0.0

All you would need to do is change one of the entries for scale from 1 to 2  to change that dimension and adjust the nodes, as follows:

	MODEL
	{
		model = Squad/Parts/Engine/liquidEngineLV-T45/model
		scale = 1,2,1
	}
	node_stack_top = 0.0, 1.430608,0.0, 0.0, 1.0, 0.0
	node_stack_bottom = 0.0, -1.167384,0.0, 0.0, -1.0, 0.0

 

It's not perfect, but at least it looks different.  

[OhioBob]

@linuxgurugamer, thanks for the suggestion.  I will certainly consider it.  At the moment I'm deeply involved in another project, so it my be a while before I can spend any time on it.  If I like the way it looks, and if it doesn't cause any other issues, I'll implement it.

[OhioBob]

@linuxgurugamer, I just took a look at the particular example that you provided.  I'm very concerned about the added length of the engines.  I think doubling the length of the engines would cause serious design and construction problems.  First, the added length will raise the vehicle's center of gravity, and stability can already be a problem for a lander of the size needed for Eve.  It might also make it more difficult to figure out how to provide mounting points for landing gear and ladders that must reach the surface.  I just don't think that doing something strictly for aesthetics is worth introducing these other problems.  For now I'm going to decline your suggestion, but trying to do something to change the looks of the nozzles is something that I would eventually like to find a solution to.

[linuxgurugamer]

4 hours ago, OhioBob said:

@linuxgurugamer, I just took a look at the particular example that you provided.  I'm very concerned about the added length of the engines.  I think doubling the length of the engines would cause serious design and construction problems.  First, the added length will raise the vehicle's center of gravity, and stability can already be a problem for a lander of the size needed for Eve.  It might also make it more difficult to figure out how to provide mounting points for landing gear and ladders that must reach the surface.  I just don't think that doing something strictly for aesthetics is worth introducing these other problems.  For now I'm going to decline your suggestion, but trying to do something to change the looks of the nozzles is something that I would eventually like to find a solution to.

Ok. 

Keep in mind that the doubling was just a suggestion.  It can be increased (or decreased) in any incremental amount.

[OhioBob]

FYI, drawing the nozzles to the correct scale, they'd look something like this:

[Murdabenne]

Any chance to get a courtesy rebuild against 1.3?  It works fine, but my OCD-ness wants to get rid of the incompatibility warning

[OhioBob]

10 hours ago, Murdabenne said:

Any chance to get a courtesy rebuild against 1.3?  It works fine, but my OCD-ness wants to get rid of the incompatibility warning

That's odd, I'm not getting an incompatibility warning.  Works fine for me in KSP 1.3.  There's really nothing in EOE to rebuild, it's just a copy of the stock engines with a few numbers changed.  Maybe it's a conflict with another mod that you're using.

[Murdabenne]

I did a binary search pare back of mods - and you are right, its another mod.  It was yours that came after the warning, so its a matter of loading order that caused it to look wrong - I should have checked the logs.  Sorry for the trouble.

 

[danielboro]

hello

will you be willing to add this mod to https://spacedock.info/kerbal-space-program
it has an option to auto add mods to ckan

[OhioBob]

Eve Optimized Engines 2.0.0

This latest release makes no changes to the engines, they should look and perform exactly the same as the previous version.  What version 2.0.0 does is change the way the engines are created.  They are now copies of stock parts rather than entirely new parts.  This eliminates the need to repackage the part textures, greatly reducing the size of the download and disk space required.  Eve Optimized Engines has been reduced to simple configuration files.

[fourfa]

Curious for your opinion about something @OhioBob.  I got interested in what actually happens IRL with over-expanded rocket exhaust, and it's interesting.  While in KSP we get crap ISP and thrust, IRL you also get flow separation inside the nozzle, leading to unpredictable asymmetric thrust and instability problems.

Which immediately seemed like an awesome thing to implement somehow... not only would the stock engines have poor performance out of range, but real physical stability consequences.  Perhaps the same thing could apply to the Rhino as a surface-level engine on Kerbin for instance (something I've often been guilty of).

Pretty far out of scope for this mod I'm sure, but wondering what you think

[OhioBob]

2 minutes ago, fourfa said:

Curious for your opinion about something @OhioBob.  I got interested in what actually happens IRL with over-expanded rocket exhaust, and it's interesting.  While in KSP we get crap ISP and thrust, IRL you also get flow separation inside the nozzle, leading to unpredictable asymmetric thrust and instability problems.

Which immediately seemed like an awesome thing to implement somehow... not only would the stock engines have poor performance out of range, but real physical stability consequences.  Perhaps the same thing could apply to the Rhino as a surface-level engine on Kerbin for instance (something I've often been guilty of).

Pretty far out of scope for this mod I'm sure, but wondering what you think

You're right that flow separation and instability can be problems with overextended nozzles.  It's an interesting thing to think about, but I'm not sure how it would be implemented in the game.  The Rhino is a good example of an "tweener."  It's more of an upper stage engine but still performs OK at sea level.  It's real life equivalent would probably be the Space Shuttle Main Engine.  Normally the SSME would produce flow separation, but engineers found a solution.  From Wikipedia...

Quote

At sea level, a nozzle of this ratio would normally undergo flow separation of the jet from the nozzle, which would cause control difficulties and could even mechanically damage the vehicle. However, to aid the engine's operation Rocketdyne engineers varied the angle of the nozzle walls from the theoretical optimum for thrust, reducing it near the exit. This raises the pressure just around the rim to an absolute pressure between 4.6 and 5.7 psi (32 and 39 kPa), and prevents flow separation. The inner part of the flow is at much lower pressure, around 2 psi (14 kPa) or less.

Flow separation would really be a problem when using the stock engines on Eve.  If there were some penalty for that, then a mod like Eve Optimized Engines becomes even more important.  I'm just not sure what the penalty could or should be.  I think one possibility is to have the engine produce a vibration.  The further out of spec an engine is, the more vibration it produces.  If serious enough, it could cause the vehicle to start wobbling out of control, or possibly causing joint breakage.  Of course doing something like that involves more than just tinkering with config files.  I have no idea how to make something like that.  How good are you at modding code?

It's not something I would want to add to EOE, but it could be an interesting mod by itself.  It would certainly be a fine addition to use in combination with EOE.
 

[Guest]

On 09/07/2017 at 1:04 AM, OhioBob said:

FYI, drawing the nozzles to the correct scale, they'd look something like this:

Do you know how an aerospike should be rescaled? I imagine simply changing the length of the spike but I guess there might be more to it.

[OhioBob]

2 hours ago, Rocket Witch said:

Do you know how an aerospike should be rescaled? I imagine simply changing the length of the spike but I guess there might be more to it.

With an aerospike there shouldn't really be a need to change anything.  The advantage of an aerospike is that the exhaust gas flows over the outside surface of the spike, therefore the exhaust stream can change its shape without having to alter the geometry of the engine.  With a bell nozzle, the bell's shape must be contoured to the exhaust stream.

Operating the aerospike at higher pressures just means that the exhaust gas won't expand as much and will be confined to a narrower stream.  If the engine is going to operate only in the high pressure environment, then it could probably be made with a smaller, narrower spike.  But that doesn't make sense because why would we use an aerospike in that scenario?  Aerospikes are intended specifically for applications where there will be a wide range of ambient pressures.  In that case we probably want to keep the geometry as is to accommodate both high and low pressures.
 

[OhioBob]

The current version of Eve Optimized Engines works with KSP 1.4.0.