OhioBob

[1.8.x - 1.3] Eve Optimized Engines

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Eve Optimized Engines
version 2.0.3


Ever get frustrated by the poor performance of stock engines on Eve?  This is because the stock engines are design to provide optimum performance on Kerbin, not Eve.  But why would you use on Eve an engine designed for Kerbin?  The simple answer, you wouldn’t.

Improving engine performance in the thick lower atmosphere of Eve is no mystery – simply adapt the nozzle’s expansion ratio to the high ambient pressure environment.  We don’t have to settle for stock engines when legitimate engineering practices can produce engines designed specifically for Eve.

Eve Optimized Engines provides low expansion ratio variants of six of the game’s most popular engines – Swivel, Reliant, Spark, Thud, Skipper and Mainsail.  The six new engines – Abel, Adam, Asp, Boa, Viper and Cobra – have greatly improved high ambient pressure performance, which comes by sacrificing low-pressure performance.  When operating on Kerbin or in space, stick with the stock engines.  But when launching from the surface of Eve, the modified engines provide good first stage power and performance.

Note that these engines also perform well on the planet Tellumo and the moon Catullus from Galileo's Planet Pack.


Download from GitHub
Download from CurseForge

 

LV-T55 “Abel” Liquid Fuel Engine

The LV-T55 engine is a low expansion ratio version of the popular LV-T45 engine. It is designed to provide optimum performance in high ambient pressure environments, while also providing thrust vectoring.

Maximum thrust:  178.72 kN (Vac.), 172 kN (ASL), 145.13 kN (Eve SL)
Specific impulse:  266 s (Vac.), 256 s (ASL), 216 s (Eve SL)

Manufacturer:  Jebediah Kerman's Junkyard and Spacecraft Parts Co.

Technology required:  advanced rocketry

LV-T40 “Adam” Liquid Fuel Engine

The LV-T40 engine is a variant of the reliable LV-T30 engine. It is furnished with a low expansion ratio nozzle to optimize its performance in high ambient pressure environments. The engineers claim it will work even on Eve.

Maximum thrust:  205.16 kN (Vac.), 196.65 kN (ASL), 165.68 kN (Eve SL)
Specific impulse:  265 s (Vac.), 254 s (ASL), 214 s (Eve SL)

Manufacturer:  Jebediah Kerman's Junkyard and Spacecraft Parts Co.

Technology required:  heavy rocketry

48-8S “Asp” Liquid Fuel Engine

The 48-8S is a variant of the Rockomax 48-7S engine with a low expansion ratio nozzle.  It is designed for use in high ambient pressure environments when a small amount of thrust is all you need.

Maximum thrust:  17.125 kN (Vac.), 16.56 kN (ASL), 14.25 kN (Eve SL)
Specific impulse:  274 s (Vac.), 265 s (ASL), 228 s (Eve SL)

Manufacturer:  Rockomax Conglomerate

Technology required:  precision propulsion

Mk-56 “Boa” Liquid Fuel Engine

The Mk-56 is a variant of the Rockomax Mk-55 engine with a shortened nozzle for use in high ambient pressure environments. It provides low power in a radially mounted configuration, for when in-line mounting just won't work.

Maximum thrust:  105.84 kN (Vac.), 102.3 kN (ASL), 87.34 kN (Eve SL)
Specific impulse:  269 s (Vac.), 260 s (ASL), 222 s (Eve SL)

Manufacturer:  Rockomax Conglomerate

Technology required:  heavy rocketry

RE-I6 “Viper” Liquid Fuel Engine

The Viper is a low expansion ratio version of the popular Skipper engine.  While outperformed by the Skipper in most environments, the Viper is really at home in Eve’s thick lower atmosphere, where it provides good mid-power performance.

Maximum thrust:  566.72 kN (Vac.), 550.47 kN (ASL), 479.38 kN (Eve SL)
Specific impulse:  279 s (Vac.), 271 s (ASL), 236 s (Eve SL)

Manufacturer:  Rockomax Conglomerate

Technology required:  heavier rocketry

RE-M4 “Cobra” Liquid Fuel Engine

The Cobra is a low expansion ratio version of the powerful Mainsail engine.  It is designed specifically for use on Eve, where it has both the high power and performance to be used as a heavy lifter.

Maximum thrust:  1350 kN (Vac.), 1311.29 kN (ASL), 1146.94 kN (Eve SL)
Specific impulse:  279 s (Vac.), 271 s (ASL), 236 s (Eve SL)

Manufacturer:  Rockomax Conglomerate

Technology required:  very heavy rocketry


Below is the Viper in action on Eve.  (Appearance is from an old version.)

EveViper.jpg

 

Edited by OhioBob

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Fully agree, great idea!

Seems like I can rescue some Kerbals (Maybe they call themselves now "Evals"...) in my career ;) 

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How realistic is such a thing (even within the Kerbal universe)?

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On ‎4‎/‎8‎/‎2016 at 4:38 AM, hab136 said:

How realistic is such a thing (even within the Kerbal universe)?

Absolutely realistic.  I used real life formulas to compute what the ISPs would be if we decreased the expansion ratio of the nozzles.  I didn't want this mod to be a means to cheat fate by using fake science.  The science is real and the numbers are realistic.  It's not cheating to do what any competent engineer and space agency would do.

Normally a nozzle is designed so that the pressure of the exhaust gas at the nozzle exit is equal to the ambient air pressure.  Of course when an engine must operate over a ranges of pressures, such as a first stage booster, compromises must be made.  A first stage engine might be expanded until its exit pressure is somewhere around 0.5 to 1 atmosphere.  The nozzles of middle stage engines, or sustainer engines, are expanded further to lower the exit pressure to the ambient air pressure expected in the middle to upper atmosphere.  For engines that are to operate in space, very large expansion ratios are used to lower the exit pressure as close to zero as is practical.

Increasing the expansion ratio improves an engine's performance in a vacuum, but decreases its performance at high ambient pressures.  This is why we generally have two classes of engines - those with small expansion ratios that have good sea level ISP but relatively poor vacuum ISP, and those with large expansion ratios that have good vacuum ISP but poor sea level ISP.

On Eve we want to go in the direction of lowering the expansion ratio.  Taking an engine designed for sea level on Kerbin and using it on Eve is just like taking an engine designed for use in a vacuum and putting it on the first stage of one of our launch vehicles.  We've learned from experience that we don't do that.  Each engine has its proper application, and for Eve we need engines designed for the high atmospheric pressures.

For our Eve engines, we want to decrease the expansion ratio until the nozzle exit pressure approaches the atmospheric pressure near the surface of Eve.  This will give us the best ISP we can get in that environment.  Of course, the downside is that we lower the ISP we'll obtain when we get to the upper atmosphere; however, by then we'll have jettisoned our first stages engines and switched to something that will perform better in the thinner air.  To launch from the surface of Eve, we want engines that will give their best performance at liftoff when the rocket is heavily burdened with a full fuel load.

For this mod, I computed what the ISP of the stock engines would be if we redesigned the nozzles to give us an exit pressure of 4.2 atmospheres.  This is the atmospheric pressure on Eve at an altitude of 1000 meters.  These engines are designed specifically for launches from low altitudes.  If you plan to land on a mountain top, then you are likely better off just using the stock engines. 

 

Edited by OhioBob

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Something else I meant to mention...  Since the modified engines are intended to be variants of the stock engines, it is assumed that the pumps, turbines, etc. are exactly the same.  That is, except for the nozzle, the Viper is the exact same engine as the Skipper.  For this reason, the propellant flow rates of the mod versions are the same as the stock versions.  Therefore, when the ISP changed, the thrust changed proportionately.

Clearly the nozzles on the modified engines should be considerable smaller than those on the stock versions.  Unfortunately, my ability to edit graphics is limited to superficial changes, such as color.  Re-illustrating the nozzle is more than I can do.  If there are any graphic artists out there who are willing to volunteer their time and talents to edit the graphics, I would very much appreciate your help.  I can provide some guidelines on how the modified nozzles should compare dimensionally to the stock illustrations.  If we can re-draw the nozzles, I should also be able to edit the lengths so the engines take up less space (which would be a big help if they are used on a lander). 
 

Edited by OhioBob

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This looks really interesting. What i like most is that these are parts that can be used with the rest of stock. What I don't like about some mods is that the parts sometimes only work with others in it's mod, completely separate from stock. But this is able to fit in well, along with being realistic. 10/10 well done.

P.S. any plans on RealPlume support and alike?

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I don't see a mass specification in the OP - are these lighter than stock engines due to less bell?  Just curious.  When I looked at stock engines on Eve, TWR of the bare engine was a really useful measure for comparing them and optimizing a ship design.

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On ‎4‎/‎9‎/‎2016 at 2:34 PM, fourfa said:

I don't see a mass specification in the OP - are these lighter than stock engines due to less bell?  Just curious.  When I looked at stock engines on Eve, TWR of the bare engine was a really useful measure for comparing them and optimizing a ship design.

No, I didn't change the mass.  I thought of that, but figured most of the mass is in the machinery, and that changing the nozzle would result in only a modest reduction in mass.  I chose just to ignore it, but that's something I can consider for a future release.  I also didn't change the cost.

Interestingly, figuring out the engine TWR is something I've already done.  Below is what I came up with.  I include the Vector and Dart (Aerospike) for comparison:

  Abel Adam Viper Cobra Vector Dart
             
TWR at Eve sea level 56.9 78.0 94.0 112.4 90.2 71.6
TWR at Eve 1-atm level 69.5 95.4 111.2 132.5 141.9 93.1

(The 1-atm level on Eve is an altitude of 10,577 meters.)

Something else I looked at is cost per kilonewton of thrust.  That's were my mod engines offer a big savings over the Vector and Dart.

  Abel Adam Viper Cobra Vector Dart
             
Cost-to-thrust (Eve SL), funds/kN 8.27 6.64 11.06 11.34 29.34 31.62

 

Edited by OhioBob
Updated stats for version 1.1.0

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I've dug deeper into the issue of mass reduction as a result of reducing the nozzle size.  My conclusion is that it is insignificant.  Even in the case of the Cobra, I doubt the mass savings compared to the Mainsail is even 100 kg.  Since we're talking about <100 kg out of 6 tons, I don't think it is worth making a change.

However, while working on the problem I revisited my specific impulse calculations and started massaging the figures.  I decided that my numbers for the Adam were a little too high, so I adjusted them down a smidgen (I also tweaked one of the Isp values for the Viper).  Therefore, there's a new release - version 1.0.2.

 

Edited by OhioBob

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Well, shoot.  I included a wrong file in that last package.  Repackaged as version 1.0.3.

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On ‎4‎/‎8‎/‎2016 at 5:29 PM, AlexTheNotSoGreat said:

P.S. any plans on RealPlume support and alike?


Real Plume version 0.10.6 now supports Eve Optimized Engines.
 

Edited by OhioBob

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Could you create an optional config which swaps the tech tree locations of the Eve and Kerbin versions of the rockets? This would be a perfect companion mod for Eve Space Program.

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Eve Optimized Engines, version 1.0.4

I just recently noticed that between KSP version 1.0.5 and 1.1.0, Squad swapped the positions of the Swivel and Reliant engines in the tech tree.  To match this change, I've swapped the positions of the Abel and Adam engines in the tech tree.

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Found this on the RealPlume support list. Actually a really good idea; thanks for keeping it up to date!

It doesn't really matter, but it would be nice if the Isps were round numbers like the stock engines.

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23 hours ago, String Witch said:

It doesn't really matter, but it would be nice if the Isps were round numbers like the stock engines.

I thought about that but decided to go with the numbers that my calculations produced.  You can always edit the configuration files yourself if you don't like the default values.  For instance, in the file liquidEngineAbel.cfg, you will find the following code,

		atmosphereCurve
		{
			key = 0 274
			key = 1 265
			key = 5 228
			key = 25 0.001
		}

That's the specific impulse at 0, 1, 5 and 25 atmospheres of ambient pressure.  Just round off the numbers if that's what you want to do.  Of course if you change the 0 value, you should also change the maximum thrust accordingly.  In liquidEngineAbel.cfg you should find the following parameter,

		maxThrust = 171.25

Just factor this by the ratio, New_Isp/Old_Isp.  For example, if you change the vacuum Isp from 274 to 275, then

maxThrust = 171.25 * 275 / 274 = 171.875

This step is necessary to keep the propellant flow rate the same.

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Eve Optimized Engines, version 1.1.0

The newest release of Eve Optimized Engines is compatible with KSP version 1.2.  Because of changes made to the Swivel and Reliant stock engines, the stats of the Abel and Adam engines have been revised accordingly.

 

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Nice idea (found this through the Galileo's Planet Pack thread). I would like too see a modified Spark though - or would that be too weak to be of any use?

Oh and shouldn't the engines be slightly lighter due to the smaller engine bell?

CKAN support would be great, too.

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12 hours ago, Nobody6 said:

Nice idea (found this through the Galileo's Planet Pack thread). I would like too see a modified Spark though - or would that be too weak to be of any use?

Oh and shouldn't the engines be slightly lighter due to the smaller engine bell?

CKAN support would be great, too.

I hadn't considered the Spark just because I thought it too small to be much use on Eve, but I'll take a look at it.  It might be worth adding.

Yes, theoretically the engines should be a little lighter, but I studied it and decided the difference is so small that it isn't worth altering the engines masses.  The bells are pretty lightweight in comparison to the machinery.

At looked at CKAN at one time and quite honestly it confused me.  I didn't understand what was needed from me to get a mod added to it, so I didn't bother.

 

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7 hours ago, OhioBob said:

I hadn't considered the Spark just because I thought it too small to be much use on Eve, but I'll take a look at it.  It might be worth adding.

It may very well be (considering the minimal weight of a lander, higher gravity and lower ISP). While at it, given its small size, don't you think that the Terrier would make a much better atmospheric engine instead of being vacuum optimized? ;-)  Would probably be useful for launching smaller/cheaper rockets from Kerbin, too.

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6 hours ago, Nobody6 said:

It may very well be (considering the minimal weight of a lander, higher gravity and lower ISP). While at it, given its small size, don't you think that the Terrier would make a much better atmospheric engine instead of being vacuum optimized? ;-)  Would probably be useful for launching smaller/cheaper rockets from Kerbin, too.

I'm not sure if any of the smaller engines would really have much use on Eve.  The delta-v requirements are so high that by the time we build a launch vehicle big enough the provide it, we're going to need the larger engines to lift it.  We'll need the lower thrust engines for later in the ascent, but by then we're high enough that we don't need them adapted for 5-atm (just use one of the stock engines).  I'm just having trouble visualizing a scenario were one would need a low thrust engine adapted for 5-atm pressure.  The only time we need a 5-atm engine is when we're lifting off the surface, and that's when we need high thrust.

I agree that stock should include a smaller 1-atm engine, something about half the size of the Swivel and Reliant.  In fact, I created for my own personal use a sea level adapted engine having a thrust of 120 kN.  I know that the parts overhaul released with KSP 1.2 includes the 100-kN LV-T15 Valiant engine, so somebody else realized the need as well.  I'm hoping the parts overhaul become stock in the future.

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1 minute ago, OhioBob said:

I'm not sure if any of the smaller engines would really have much use on Eve.  The delta-v requirements are so high that by the time we build a launch vehicle big enough the provide it, we're going to need the larger engines to lift it.  We'll need the lower thrust engines for later in the ascent, but by then we're high enough that we don't need them adapted for 5-atm (just use one of the stock engines).  I'm just having trouble visualizing a scenario were one would need a low thrust engine adapted for 5-atm pressure.  The only time we need a 5-atm engine is when we're lifting off the surface, and that's when we need high thrust.

For launching they will probably be to small. However, they could be useful for a controlled final descent (like Curiosity's descent stage). Or to give a rover the ability to jump over obstacles.

Anyway, given the same method you used before - how much thrust would the small engines produce?

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2 hours ago, Nobody6 said:

Anyway, given the same method you used before - how much thrust would the small engines produce?

If we assume a 5-atm specific impulse of 215 s (about what I got for the Abel and Adam engines), then the Spark would produce about 13.5 kN and the Terrier would produce about 37 kN.  I would have to do some more detailed calculations to determine what the exact numbers would be.
 

Edited by OhioBob

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I modified the sparks config myself to let me use it as a landing engine on Tellumo. 

Engines this size would also be viable for sample return missions if the parts were available. A 10 KG sample capsule could be put into orbit by a spark-sized first stage. Clustering is also a possibility. 

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Eve Optimized Engines, version 1.2.0

Rockomax Conglomerate announces the addition of two more engines to its Eve-optimized product line  the 48-8S "Asp" and the Mk-56 "Boa".  These engines are low expansion ratio variants of the 48-7S "Spark" and Mk-55 "Thud".  The additions should round out the product line nicely by providing a low thrust engine and a radially mounted engine for specialized applications.

Further EOE 1.2.0 changes include upgrading to the most current KSP 1.2.2 configs and textures.  This means that the old blue paint that distinguished previous EOE products from the stock versions is gone.  Modified engines now have the exact same appearance as their stock counterparts.

 

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