[1.7-1.9] SMURFF: Simple Module adjUstments for Real-ish Fuel-mass Fractions 1.9.1 (02019 Nov 12)

[MatterBeam]

Thank you enormously for this mod. I used to make manual patches before.

Question: Have you done something about procedural tank masses?

[Kerbas_ad_astra]

Thank you enormously for this mod. I used to make manual patches before.

Question: Have you done something about procedural tank masses?

If you get the "live" SMURFF.cfg from the GitHub repo (as opposed to the one from the release zip), it has a patch for procedural tanks.

[Kerbas_ad_astra]

Sorry, must have misread. 3% structural / 9&% fuel fraction does sound right.

For LH2 RF goes with 0.0206t per cubic meter for a non-balloon (Delta IV-like) tank, or 0.0066t for balloon cryo. That equates to 22.5% and 8.5% structural fractions Clearly I was getting confused between the LH2 tank's structural fraction alone (which is very high) and the sum of 5.5:1 or 6:1 LOX/LH2's structural fraction...(which is on the order of 1.5x compared to LOX/kero)

sorry...

You might want to check the Volumes page here: https://www.dropbox.com/s/lz2ntsqhwe192xv/Calcs.xls?dl=0

It has all the data RF uses to mass tanks.

Thanks for the spreadsheet! Are its values sourced/developed for "generic" tanks? I ask because, plugging in the numbers for the External Tank (6:1 ratio, 100% utilization, 735 tons of propellant), I get a tank mass that's heavier than even the initial Standard Weight Tank (43 tons = 5.5% vs. 35 tons for the SWT, 30 tons for the LWT, 26.5 tons for the SLWT).

[NathanKell]

The numbers are designed to end up with reasonable stage structural fractions; the ET it best simulated as a BalloonCryo tank with a bit of leadballast, since the regular Cryo tank is modeled more on Delta IV CCB, DCSS, and the like, rather heavier than the ET. The ET is quite close to the Ariane V EPC in terms of dry mass, and EPC is a balloon tank.

[Kerbas_ad_astra]

The numbers are designed to end up with reasonable stage structural fractions; the ET it best simulated as a BalloonCryo tank with a bit of leadballast, since the regular Cryo tank is modeled more on Delta IV CCB, DCSS, and the like, rather heavier than the ET. The ET is quite close to the Ariane V EPC in terms of dry mass, and EPC is a balloon tank.

I see. In that case, it looks like my comparison of the ET to Near Future Propulsion's tanks wasn't very fair, since the ET only needed to hold fuel for a few minutes while NFP's tanks are more intended for long-term storage for ion and nuclear thermal rockets. (FreeThinker, this means that your tanks would have a -log(0.16) vs. -log(.22) = 21% advantage over Near Future Prop's LH2 tanks.) I don't think the next version of SMURFF (KSP-RishA) will patch LH2 tanks at all. I'll still provide an alternate Cryogenic Engines patch, since the one that Nertea ships inherits the stock tank mass fraction penalties.

The next version won't patch argon tanks, either, because it turns out that argon just doesn't store efficiently. For the interested, according to this paper, tank mass needs to be at least 31% of fuel mass, or 62% with a 2x factor of safety, and NFP's tanks weigh 50% as the fuel they hold, which is fine by me. It's a gas properties issue -- argon is much lighter than xenon, which means its pressure vessel is going to be heavier relative to its contents, and there's also the matter that supercritical gas effects mean that the optimal storage pressure for argon is almost twice that of xenon. (The reason that we're still thinking about argon is that it's more common and thus cheaper at large quantities than xenon, which may be overcome the storage difficulties for large-scale ion and plasma thrusters.)

Edited September 17, 2015 by Kerbas_ad_astra

[NathanKell]

Makes sense to me!

For your applications you might be able to get away with lower tank masses, because as mentioned RF tries to arrive at reasonable stage structural fractions, rather than tank masses alone, so some of the thrust structure and some of the interstage may be baked into the tank mass. With heavy stock KSP interstages/decouplers, and with control over engine TWRs (i.e. you can bake the thrust structure entirely into the engine--and note it may be up to 50% of engine mass!), you can get away with lighter tanks.

[Kerbas_ad_astra]

NathanKell said:

Makes sense to me!

For your applications you might be able to get away with lower tank masses, because as mentioned RF tries to arrive at reasonable stage structural fractions, rather than tank masses alone, so some of the thrust structure and some of the interstage may be baked into the tank mass. With heavy stock KSP interstages/decouplers, and with control over engine TWRs (i.e. you can bake the thrust structure entirely into the engine--and note it may be up to 50% of engine mass!), you can get away with lighter tanks.

I did think about that, but I also don't want to be overly generous (in the engineering business, we're all about keeping margins in our simulations), and I don't want to cut masses too low, as I understand that connection strength is linked to the masses of the parts involved. I'll mull LH2 some more, but unless I have an epiphany (or I hear some suitably convincing argument), I probably still won't buff pure LH2 tanks at all, since the ones in NFP are doing about as well as a real tank could. That said, I'll probably keep the LH2 tank mass improvement in the modified Cryogenic Engines fuel-switcher patch, since that uses a worse tank mass fraction. I am also definitely making a pull-request to get the FTT LH2 tanks to be as efficient as Nertea's, since those tanks are heavier than the fuel right now. It's been raised as an issue in the FTT thread before, but a PR will hopefully stay on RoverDude's radar better.

Speaking of engines, I wasn't being entirely fair to them, either -- RP-1 engines get about twice the TWR of LH2 engines, so I shouldn't have used the SSME as a baseline for comparison. The next version will make engines even lighter (by 62.5% instead of 50%) and give them a 50% boost (heh!) to thrust.

The ultimate test of all of this figuring will be my "Sarnus VII" mission to the Mun Moon. It weighs almost 2500 tons and stands over 78 meters tall, which is about right for a moon rocket, and after I'm done adding control hardware, if the flight goes well, I'll consider it ready for release.

 

Spoiler

 

WE BRAKE FOR NOBODY

 

 

One more question, for the whole group this time. In the current patch, I don't give switchable fuel tanks as much of a buff as their regular counterparts (50% dry mass reduction vs. 75% = 94% fuel mass fraction instead of 97%). I had justified this by supposing that the parts have extra hardware to accommodate the exchanging -- rails and brackets and such. However, in-flight fuel switching is disabled by default, and I'm not aware of any parts that use it (Cryogenic Engines doesn't, nor does any USI stuff). Do you all think of parts with Interstellar or FS Fuel Switcher as being one part with multiple contents, or multiple parts in the same "inventory pile"?

Edited December 18, 2015 by Kerbas_ad_astra
Spoiler was so effective I forgot to include the picture!

[NathanKell]

I see it as multiple parts.

Regarding engine TWR, if you look on the Isps page of Calcs.xls, it shows what I've calculated (based on a disturbing amount of analysis) should be the goal TWR of an engine at any given tech level, where 0 is Redstone, 1 is Atlas, 2 is Titan II, 3 is Saturn V, 4 is AAP, 5 is Shuttle, 6 is 90s, and 7 is present. O is PF OMS, U+ is pump-fed upper, U is upper/sustainer (J-2), L is lower, and L+ is sustainer (SSME). In my experience I found hydrolox usually had a TWR of 75% normal, rather than half; you may not be comparing apples to apples since most LH2 engines will be uppers and most kerolox lowers).

[Kerbas_ad_astra]

I see it as multiple parts.

Regarding engine TWR, if you look on the Isps page of Calcs.xls, it shows what I've calculated (based on a disturbing amount of analysis) should be the goal TWR of an engine at any given tech level, where 0 is Redstone, 1 is Atlas, 2 is Titan II, 3 is Saturn V, 4 is AAP, 5 is Shuttle, 6 is 90s, and 7 is present. O is PF OMS, U+ is pump-fed upper, U is upper/sustainer (J-2), L is lower, and L+ is sustainer (SSME). In my experience I found hydrolox usually had a TWR of 75% normal, rather than half; you may not be comparing apples to apples since most LH2 engines will be uppers and most kerolox lowers).

To get my revised TWR improvement numbers, I looked at the stock lower-stage engines, saw TWRs from 15-25 (except for the Swivel, which clocks in at 11, but whatever), and on this chart, lower-stage kerolox engines have TWRs in the 60-150 range (which largely agrees with your chart). Since SpaceY and Behemoth engines have TWRs in the 30s, a 4x improvement feels about right (vs. my initial comparison to the SSME at 54 which lead to a 2x improvement). I allocated some of that improvement to increasing thrust to let engines support taller stacks and reduce the need for boosters. SpaceY Expanded's big lifter engine has a thrust value that is close to (7.5/10)^2 times the total Saturn V first-stage thrust, and the 2.5m engines have Merlin-like thrusts, so I don't want to increase thrust too much; the 50% improvement lets me get that Sarnus VII to have a sufficient TWR without needing SRBs. (According to Kerbal Engineer, anyway -- pending revision if the test goes poorly.)

EDIT: And I see that I can look for the variable that sets whether a switchable tank can be switched in flight and use that to decide which buff to apply.

Edited September 18, 2015 by Kerbas_ad_astra

[NathanKell]

4x does indeed sound right, although you may need to try to discern which are upper and lower stage engines....the high-tech NASA/ARM engines in stock are in the 22-30 range themselves.

[Kerbas_ad_astra]

NathanKell said:

4x does indeed sound right, although you may need to try to discern which are upper and lower stage engines....the high-tech NASA/ARM engines in stock are in the 22-30 range themselves.

The only stock upper-stage motor that gets a crazy TWR is the Rhino, and even then, Wikipedia says that the upper-stage RD-118 gets similar TWRs (Rhino = 68-92, RD-118 = 76-86 -- their other parameters are also in the ballpark with each other), so I'm not too worried.

Also, here's one small step for some Kerbals, and one giant leap for SMURFF:

It's definitely a challenge to launch moon missions with (mostly) stock parts, but I really wouldn't want to try it with stock mass fractions and TWRs!

I've still got some corner-cases to chase out, but I'm satisfied with the balancing. The full release will probably wait until after sarbian comes back from vacation and makes a public release announcement of Module Manager 2.6.11, since it includes a fix that will let SMURFF handle atmosphere curves with tangents.

Speaking of which, unless I get enormous outcry from Viewers Like You, I won't call the next version KSP-RishA, since I'd rather not have to go to the trouble of juggling multiple repos and such to keep the .version files pointing in the right direction (not to mention avoiding the potential user confusion of having a different folder name in GameData). The meaning of the acronym will just be changed.

That said, there will be a new logo to celebrate the inclusion of engines in the patches!

Edited January 8, 2016 by Kerbas_ad_astra
Fixed the album for the forum update.

[monstah]

The meaning of the acronym will just be changed.

I find S.M.U.R.F.F a very friendly acronym ^^

Looking forward to this.

[Kerbas_ad_astra]

SMURFF 1.1 has been released! Check out the new release on GitHub, and the new logo as well! We're not just tinkering with masses anymore (though it's still mostly mass adjustments).



Changelog:

• 2015 11 19 (1.1): Renamed to Simple Module adjUstments for Real-ish Fuel-mass Fractions (since we're not just touching mass anymore).
  • +50% to non-SRB engine thrusts and -62.5% to mass, to bring TWRs in line with RP-1/LOX engines and reduce need for ridiculous engine clusters.
  • +40 seconds to SRB Isp, to bring Kickbacks in line with Space Shuttle SRBs.
  • Mass reduction of resource containers is now proportional to their contents, so parts which have resources and do other things (e.g. command pods, wings with fuel) only get mass reduction corresponding to the part of them which holds resources (e.g. command pods are now slightly lighter because of their monopropellant storage, but not by a factor of 4).
  • New patch to act on Procedural Parts.
  • Based on RealFuels data and further research, LH2 and argon mass fractions no longer improved.
  • Adjusted patch to properly grab all engine modules.
  • Compatible with Stock Fuel Switch and Cryogenic Engines.
    • If you replaced or modified Cryogenic Engines's fuel switcher patch, make sure you restore it to the original -- otherwise, tanks might get double-buffed.

Edited January 8, 2016 by Kerbas_ad_astra
Fixed formatting.

[speedwaystar]

great work. i really like the keep-it-simple-stupid principle behind SMU (simple modulemanager adjUstments)--i hope it catches on!

here's a stock 3m procedural LFO tank:

[IMG]http://i.imgur.com/wYd7HU3.jpg[/IMG]

and the same tank with SMURFF:

[IMG]http://i.imgur.com/GUS7iV6.jpg[/IMG]


fix:

[CODE]@PART
[*]:HAS[@MODULE[TankContentSwitcher]]:FOR[SMURFF]{
@MODULE[TankContentSwitcher]
{
@TANK_TYPE_OPTION[Mixed,LiquidFuel,Oxidizer,RCS]
{
@dryDensity /= 4
@RESOURCE[LiquidFuel]
{
@unitsPerT *= 4
}
@RESOURCE[Oxidizer]
{
@unitsPerT *= 4
}
@RESOURCE[Monopropellant]
{
@unitsPerT *= 4
}
}
@TANK_TYPE_OPTION[XenonGas]
{
@dryDensity /= 7
@RESOURCE[XenonGas]
{
@unitsPerT *= 7
}
}
@TANK_TYPE_OPTION[SolidFuel]
{
@dryDensity *= 0.6
@RESOURCE[solidFuel]
{
@unitsPerT /= 0.6
}
}
}

%MODULE[ModuleSMURFF]{ }
}[/CODE]

[IMG]http://i.imgur.com/7gY6kO8.jpg[/IMG]

enjoy! :D

EDIT: pull request created Edited November 20, 2015 by speedwaystar

[komodo]

Ooh. This looks fun. I've been meaning to roll my sleeves up and dive back into 6.4x for a bit now... This will certainly help. Looks good, from what i've seen! Thanks for all the [S]fish[/S] work!

Perhaps a madness inducing question: Is there a way to MM a MM patch? I wonder if it might be worth it (probably = not) to tweak the tweaked values for 6.4x... Hrm... (Worth it for me, I mean. Not asking for further custom work!)

[AndreZero]

I love the idea of this mod because I want to play in the real solar system with KSP's simplified systems. I do have one question about this though.
Since mass is a part of the equation for Delta-V, does this mod invalidate the delta-v charts for the solar system? If so, is there an updated reference?

[billkerbinsky]

[quote name='AndreZero']Since mass is a part of the equation for Delta-V, does this mod invalidate the delta-v charts for the solar system? If so, is there an updated reference?[/QUOTE]
No. The rocket equation [1] determines the amount of delta-V that a rocket will get, not the amount of delta-V required to go somewhere.

The changes in this mod mean you'll get higher performance (more delta-V) from the same collection of parts because the dry mass of the parts (the mass measured with empty tanks) is smaller.


[1] deltaV = Ve * log(m0 / m1)
Ve is exhaust velocity
m0 is initial mass
m1 is final mass

this mod decreases both m0 and m1; since m0 is typically much larger than m1, this increases m0/m1 and as a result also increases deltaV.

[AndreZero]

[quote name='billkerbinsky']No. The rocket equation [1] determines the amount of delta-V that a rocket will get, not the amount of delta-V required to go somewhere.
[/QUOTE]

Makes perfect sense. Thanks!

[Kerbas_ad_astra]

To expand on billkerbinsky's point, this mod will let a given rocket have more delta-V. It's the solar system itself which determines how much you need to go somewhere.

On 11/19/2015, 6:50:03, speedwaystar said:

EDIT: pull request created

And accepted. Thanks! I'll have 1.1.1 out shortly, with this and another fix. (The TWR patch will only be applied to LFO and LH2/Ox engines.)

On 11/20/2015, 9:48:06, komodo said:

Ooh. This looks fun. I've been meaning to roll my sleeves up and dive back into 6.4x for a bit now... This will certainly help. Looks good, from what i've seen! Thanks for all the fish work!

Perhaps a madness inducing question: Is there a way to MM a MM patch? I wonder if it might be worth it (probably = not) to tweak the tweaked values for 6.4x... Hrm... (Worth it for me, I mean. Not asking for further custom work!)

Patches cannot be patched (thankfully for our sanity). You could adjust some of the values yourself to get lesser improvements to fuel mass fraction, but I'm not sure it would be worth your time to do. Delta-V to get into LK64O is about 7.5 km/s, which the "Kerbal X Heavy" (i.e. one pair of boosters) can achieve with stock parts. That would put almost 7 tons in space with a 207-ton rocket (i.e. 30x as much rocket as payload), which is about what real rockets achieve. In other words, building rockets with stock parts in 6.4x KSP is about as hard as building real rockets (with realistic performance) in the real solar system is. Using SMURFF would make it possible to get that payload into orbit without boosters (possibly requiring a further extension to the upper stage), which would only be about 15-20x as much rocket as payload (which is still harder than the stock game, ~5-7x as much rocket as payload), which doesn't leave a whole lot of room for an intermediate buff.

Edited December 18, 2015 by Kerbas_ad_astra
Fixed formatting.

[Kerbas_ad_astra]

Version 1.1.1 is here!

• 2015 11 20 (1.1.1): Minor bug fixes.
  • Fixed Procedural Parts patch (thanks to speedwaystar).
  • Excluded air-breathing jets, nuclear thermal rockets, monopropellant engines, and ion engines from TWR buffs. (They're close enough to reality already.)

Edited December 18, 2015 by Kerbas_ad_astra
Fixed formatting.

[Kerbas_ad_astra]

One more quick update (<Uncle>One mooooore thing!</Uncle>), which should be the last one for a while (until another bee flies into my intake):

2015 11 22 (1.1.2): More compatibility (inspired by Atomic Age).

• Improved selectivity of engine mass buff by excluding multi-mode engines and IntakeAtm-breathing engines. (All Oxidizer-burning engine modes will still get a thrust increase.)

Thanks!

Edited January 8, 2016 by Kerbas_ad_astra

[komodo]

Everything seems legit with this version to me. (Finally got time to try it out!)

How have your reentries gone, if I might ask? My first suborbital hop reminded me that heatshields = a good idea, but following that, it was still a little rocky. Ablator was fine still, but the pod was a little red... + overtemp bars appearing, heh.

I'm going to play around with my options to find the best fit, I just wanted to say thanks for putting this together though. It's a fine piece of MM, although some of it makes me at the same time!

[Kerbas_ad_astra]

I'm glad you like it!  Speaking of mind-scrambling, I've recently found another adjustment that needs making -- some of SpaceY's engines are not getting their masses improved because they're using the multi-mode module to simulate center-out or center-only modes (rather than having a jet plus a rocket engine, which is what I meant to exclude).  Adjusting the logic isn't hard, but the testing and packaging needs time I don't have right now.

I've been alright with reentries.  Steeply-vertical descents can run into trouble where there isn't enough room to decelerate to a safe speed -- not that my tourists have ever experienced such a mishap -- but that's the case for stock Kerbin as well.  (SMURFF doesn't tinker with physics parameters; RSS does that.)

[NathanKell]

Yep, if you try a reentry with only 40% of the drag you should have...you're gonna have a bad time.

+1 rescaling mafia

[Kerbas_ad_astra]

I don't see anything about the MODEL/rescaleFactor bug being fixed in the 1.0.5 changelog... 

+1 little blue people