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Realism Overhaul Discussion Thread


NathanKell
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From what I've been reading NASA is quite fond od using hydrazine with a combination of NTO or MON for their probe's engines. I've been wodering if a combination of N2H4/NTO could be used on RCS as a different combination of propellants to choose. Are there any more combinations od propellants do RCS or the ones we have are here to stay?

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hey guys! quick one for all of you connoisseurs - is anyone using SpaceX's engines under RO? What part pack would you recommend?

I'd like to test Merlin & Raptor and maybe replicate BFR?

Let me know! very much appreciated :D

Edited by hypervelocity
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Hey guys I made a quick and dirty PartModule based off (Acutally derived from) CoMShifter for a kOS idea I had, but then thought I'd share it here too . It adds the "CoM Offset Limit" slider to control the descent mode offset so it can be utilized by kOS scripts for reentry maneuvering(Or manually for finer control) . Should I submit a pull request?

Looks like this (Notice the reduced AoA):

4rM1ak9.png

 

 

Edited by Alpha_Mike_741
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1 hour ago, Alpha_Mike_741 said:

Hey guys I made a quick and dirty PartModule based off (Acutally derived from) CoMShifter for a kOS idea I had, but then thought I'd share it here too . It adds the "CoM Offset Limit" slider to control the descent mode offset so it can be utilized by kOS scripts for reentry maneuvering(Or manually for finer control) . Should I submit a pull request?

Looks like this (Notice the reduced AoA):

*snip*

 

 

Wow, you're just a few days ahead of me. I was thinking of making the same for a few weeks now haha. Could you share the patch, please? :):) 

Edited by DrLicor
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On 30.9.2017 at 5:41 PM, hypervelocity said:

hey guys! quick one for all of you connoisseurs - is anyone using SpaceX's engines under RO? What part pack would you recommend?

I'd like to test Merlin & Raptor and maybe replicate BFR?

Let me know! very much appreciated :D

I have come quite fond of using SSTU stuff, it has basically the full complement of SpaceX engines, and even an Orion capsule, if that's the droids you're looking for.

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  • 1 month later...

Any news on progress towards upgrading to 1.3.1?

EDIT :

On 10/08/2017 at 3:34 AM, raidernick said:

no

 

On 10/08/2017 at 3:18 PM, Bornholio said:

It is a slow process, It depends on each required mod first being 1.3.  For some mods the change is as simple as recompiling once. Others require fundamental fixes. Then RO needs to accommodate any changes they make.

https://docs.google.com/spreadsheets/d/1A7gQkIiQKi0VtRecE6p86KCKuoawZPdzk7NlaxssRJ4/edit#gid=523836116

So the answer is no :P  That said lots of work is happening in development RO & RP-0

Version release on Reddit  https://docs.google.com/spreadsheets/d/1it8cZ_t8J67m4oPOvjzgBxHZvSXsvhNTPhlDVqEGTFY/edit#gid=0

 

Edited by John FX
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12 hours ago, StellarumSectatio said:

Does anyone have any part recommendations for high efficiency engines, like Ion engines, VASIMR, bimodal NTR, etc?

Any electric drive will tax your patience considering that they generally need many hours of burn to be useful https://github.com/KSP-RO/RealismOverhaul/wiki/Ion-Engines.  The BNTR (peewee class 500MW) and NERVA II (Phoebus class 5000MW)are useful at the 6-12km/s fuel load range, any less likely use a 455-465ISP Hydrolox. 

I put set of engines based on real NTR's in RO  that are ground tested that have Methane configs in addition to Hydrogen https://github.com/KSP-RO/RealismOverhaul/commit/3d726589e207285825c36cd022716f71dc86960a.  If Methane config nukes are an option ( only the soviet RD-0410 was ever tested) they will out perform Hydrolox in the 3-5km/s range and then Hydrogen Nukes will outperform Methane in the 7-10km/s range.  https://github.com/KSP-RO/RealismOverhaul/wiki/Engine-Usage-and-Stage-Sizing

If you are using Nertea's Future Prop one option if you have patience is using the Plasma RCS single thrusters as a cluster main drive, the ISP is above Nukes but relatively low allowing them to have reasonable TWR thus giving burn times that might only be an hour long for capture burns and other big dV changes.

A nuke powered VASIMR is doable but generally outperformed by NTR unless you need 20km/s dV or more and then you will be doing overnight or worse burns at x4 physical timewarp.

If you are looking for an advanced realistic option the highest performance up to the 20km/s range is the SNTP (a 1000MW reactor) they have a design TWR in the mid teens and an ISP of 940.  With only 5 ignitions they are very optimal for a planetary injection/correction/capture.  For any high ISP option Hydrogen/Cryo boiloff is the main problem so you need a solution to that for keeping any cryo fuels.  

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5 hours ago, Bornholio said:

Any electric drive will tax your patience considering that they generally need many hours of burn to be useful https://github.com/KSP-RO/RealismOverhaul/wiki/Ion-Engines.  The BNTR (peewee class 500MW) and NERVA II (Phoebus class 5000MW)are useful at the 6-12km/s fuel load range, any less likely use a 455-465ISP Hydrolox. 

I put set of engines based on real NTR's in RO  that are ground tested that have Methane configs in addition to Hydrogen https://github.com/KSP-RO/RealismOverhaul/commit/3d726589e207285825c36cd022716f71dc86960a.  If Methane config nukes are an option ( only the soviet RD-0410 was ever tested) they will out perform Hydrolox in the 3-5km/s range and then Hydrogen Nukes will outperform Methane in the 7-10km/s range.  https://github.com/KSP-RO/RealismOverhaul/wiki/Engine-Usage-and-Stage-Sizing

If you are using Nertea's Future Prop one option if you have patience is using the Plasma RCS single thrusters as a cluster main drive, the ISP is above Nukes but relatively low allowing them to have reasonable TWR thus giving burn times that might only be an hour long for capture burns and other big dV changes.

A nuke powered VASIMR is doable but generally outperformed by NTR unless you need 20km/s dV or more and then you will be doing overnight or worse burns at x4 physical timewarp.

If you are looking for an advanced realistic option the highest performance up to the 20km/s range is the SNTP (a 1000MW reactor) they have a design TWR in the mid teens and an ISP of 940.  With only 5 ignitions they are very optimal for a planetary injection/correction/capture.  For any high ISP option Hydrogen/Cryo boiloff is the main problem so you need a solution to that for keeping any cryo fuels.  

Thanks for this, evidently I have much to learn! 

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Looking at the RO source, i see that upper stage engines seem to have a sea level Isp in the 200-250 range - isn't this far too much though? Flow separation would cause thrust instabilities and might even damage the engine. But even disregarding flow separation, i found this handy rocket thrust simulator from NASA. Using it to try to determine sea level Isp, i get much lower values (and also a shock warning at too low altitudes). The idea for more realistic behavior of those vacuum engines is thus to reduce Isp below a certain nozzle exit pressure to ambient pressure ratio to zero or some small value (or don't allow the engine to be ignited at all). Also, below that ambient pressure, where we assume no flow separation occurs, Isp could be approximated with that thrust simulator. I plotted such Isp curves for a few vacuum engines of another mod, setting the Isp to zero when the nozzle exit pressure is below 10 % of the ambient pressure. The curves are plotted against the altitude of Kerbin's atmosphere:

32295564-ef672000-bf49-11e7-859f-a3aa985

Note how the RL10B-2 has to pay for that huge nozzle/expansion ratio at low altitudes. The J-2X works better at low altitudes than the RL10s because of a higher chamber pressure.

Any thoughts about this?

Edited by Mike`
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2 hours ago, Mike` said:

Looking at the RO source, i see that upper stage engines seem to have a sea level Isp in the 200-250 range - isn't this far too much though? Flow separation would cause thrust instabilities and might even damage the engine. But even disregarding flow separation, i found this handy rocket thrust simulator from NASA. Using it to try to determine sea level Isp, i get much lower values (and also a shock warning at too low altitudes). The idea for more realistic behavior of those vacuum engines is thus to reduce Isp below a certain nozzle exit pressure to ambient pressure ratio to zero or some small value (or don't allow the engine to be ignited at all). Also, below that ambient pressure, where we assume no flow separation occurs, Isp could be approximated with that thrust simulator. I plotted such Isp curves for a few vacuum engines of another mod, setting the Isp to zero when the nozzle exit pressure is below 10 % of the ambient pressure. The curves are plotted against the altitude of Kerbin's atmosphere:

 

Note how the RL10B-2 has to pay for that huge nozzle/expansion ratio at low altitudes. The J-2X works better at low altitudes than the RL10s because of a higher chamber pressure.

Any thoughts about this?

Generally they are not guesses, they are available estimates from some reliable source.  Commonly this is NTRS data such as https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100034922.pdf

Worrying about sea level thrust on these engines is not too much of an issue. They don't have the thrust to be useful as first stages and most of the time a modern first stage is putting them in a safe and well known altitude. Nothing in KSP handles thrust instability and flow separation so its up to the designer not to pick wrong engines.  NASA and others have investigated widened range solutions via aerospikes (Annular and Linear).  Even the J-2 has seen both forms for test stand runs (J-2T and XRS-2200) but commonly the solution is upping the chamber pressure. 

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9 hours ago, Bornholio said:

I briefly skimmed through this document, couldn't find any sea level performance though. In https://blogs.nasa.gov/J2X/2013/08/06/inside-the-leo-doghouse-rs-25-vs-j-2x/ they mention that the J-2X cannot (safely) run at sea level pressure with the vacuum nozzle extension.

I agree it's probably not a huge issue. The thing i'm a little worried about is that engines like the J-2X  in clusters can be used as sustainers together with first stage boosters like the space shuttle did with the RS-25. According to my understanding, this won't work IRL without modifications though as the J-2X cannot operate at sea level.

Edited by Mike`
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On 11/11/2017 at 6:07 AM, Theysen said:

Community Resource Pack and the correct ratios inside of the engine configuration 

It seems like the Community Resource Pack contains the definitions of "resources" which can be mined from planets, but not propellants. I'm looking to see where a propellant like Liquid Hydrogen is defined, and am expecting it to have values for things like "density".

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13 minutes ago, delta wee said:

It seems like the Community Resource Pack contains the definitions of "resources" which can be mined from planets, but not propellants. I'm looking to see where a propellant like Liquid Hydrogen is defined, and am expecting it to have values for things like "density".

https://github.com/BobPalmer/CommunityResourcePack/blob/master/FOR_RELEASE/GameData/CommunityResourcePack/CommonResources.cfg#L616

Why would I lie to you :P

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1 hour ago, delta wee said:

Are the names for resources in the CommonResources.cfg file allowed to have spaces in them?

Yes and No, the module space name must not (name=), but description names may (displayName=).

If you want much more detail on CRP Roverdude and crew over in CRP land have better detail and look like they have done a huge amount of work localizing lately.

Edited by Bornholio
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Rats! I have this idea of a floating base on Laythe. I thought I could use the K&K inline water driller to take the water on Laythe and make oxygen and hydrogen. But it did not work.  The driller wants to be on solid ground. Is there a cfg setting I can edit to tell the driller it can suck up the water on Laythe without being on solid ground?

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23 hours ago, delta wee said:

Is there something else that needs to be done besides adding an entry to the CommonResources.cfg file in order to add a new propellant which can use to fill tanks?

You would also need an engine set up to burn that propellant. 

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On 11/12/2017 at 7:11 PM, delta wee said:

Is there something else that needs to be done besides adding an entry to the CommonResources.cfg file in order to add a new propellant which can use to fill tanks?

Using CRP as an example make a small .cfg file adding the resource and then either modify or make new a consumer for the resource. You can make it all in one file if you want. Suggest that you separate it a custom mod folder so you can easily extricate it it you don't want to use it or it breaks things. Alternately squad/resources/ResourcesGeneric.cfg  can be added to.

Example  see https://wiki.kerbalspaceprogram.com/wiki/CFG_File_Documentation#RESOURCE

EvilAI.cfg

RESOURCE_DEFINITION
{
	name = SelfReplicatingBooleanCode
	displayName = SRBC Units
	density = 0.1
	flowMode = ALL_VESSEL
	transfer = PUMP
	isTweakable = true
   	isVisible = true
	unitCost = 0.5000000
	color = .25,.25,1
	volume = 1
}

Then pick a useful module to consume or modify it in another part https://wiki.kerbalspaceprogram.com/wiki/Module.

Edited by Bornholio
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So, does anybody have additional information about the source of sea level performances of the vacuum engines? For example, in RO, the RL10-B2 has a sea level Isp of 235 s, while the J-2X has 200 s, even though the latter has a much smaller expansion ratio and over twice the chamber pressure (in a vacuum)... looks weird to me.

Edited by Mike`
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