[1.5 - 1.12.5] BetterSRBs [v1.2.6] [30 June 2021]

[OhioBob]

BetterSRBs

Description

BetterSRBs modifies solid rocket boosters in Kerbal Space Program.  Although some new parts are added, this is really not a parts mod.  The purpose is to fix deficiencies in existing SRBs so that their performance and physical properties are internally consistent and closer to real life.

SRBs continue to have mass ratios comparable to the stock game, but specific impulse has been increased to lifelike values.  Dry masses, fuel loads, and thrusts are computed in a realistic manner based on the physical dimensions of the part.

These changes result in improved SRB performance, both in terms of efficiency and total impulse.  This improved performance must come at a price, so SRBs are now significantly more expensive.  On a cost vs. performance basis, the price of SRBs remains comparable to the stock game.

Also implemented is the use of thrust curves to vary thrust during a burn in a realistic way.  And with the addition of B9 Part Switch, the player can select from different fuel grain geometries to obtain the thrust curve best suited to one's needs.

New Parts

BetterSRBs adds parts to fill the need for a more diverse range of SRBs in the stock game. The parts added are just rescaled duplicates of existing parts, though with new textures to give them a distinctive appearance. There are now 1.875-meter versions of the Thumper and Kickback solid fuel boosters. Also added is a 1.875m nose cone and a 1.875 x 1.25m adapter.

Requirements

ModuleManager

Recommended Mods

B9 Part Switch - While not expressly required, B9 Part Switch allows part variants not otherwise available.

SmartParts - SRB Monitor auto-stages SRBs when the thrust-to-weight ratio falls below a specified value.

Supported Mods

In addition to modifying the stock parts, configs are also included to modify the SRBs of the following part packs:

• SpaceY Heavy Lifters
• KW Rocketry Rebalanced
• NovaPunch Rebalanced
• RLA Reborn
• ReStockPlus
• Mk3 Stockalike Expansion

Also included is RealPlume support for the added SRBs.

Installation Instructions

1. Download BetterSRBs v1.2.7
2. Copy from [Download]\GameData\ to [KSP]\GameData\ the folder BetterSRBs and all its contents.

Credits

@Sigma88 for writing the plugin.

@JadeOfMaar for retexturing the new parts.

License

This mod is licensed by Creative Commons Attribution-NonCommercial-NoDerivs
CC BY-NC-ND
 

Download (GitHub)
 

FAQ

How much have SRBs changed from the stock versions?

In some cases, significantly. Other than physical dimensions, pretty much everything about the original SRBs has been thrown out and recomputed from scratch. Only the Kickback has retained its original mass properties, which provides the standard for other SRBs. Thrusts are also redone, computed on the basis of fuel grain size and geometry.

What's the difference between using B9 Part Switch and not using it?

BetterSRBs works fine without B9 Part Switch, but all SRBs use only one default thrust curve with no option to change.  With B9 Part Switch installed, you can right-click on a SRB in the editor and select from a list of different grain geometries, each with a different thrust curve.

What are grain geometries and thrust curves?

In real life SRBs do not burn at constant thrust as they do in stock KSP.  As the solid fuel burns, more or less surface area is exposed to the flames, changing the rate of gas production, and hence the thrust.  By changing the initial shape of the fuel, i.e. the grain geometry, it's possible to control the speed and pattern at which the fuel burns.  Plotting thrust versus time gives the thrust curve.

B9 Part Switch is installed but some SRBs are not showing the variants?

The grain geometry variants are added only to those parts changed by BetterSRBs.  If an SRB is not showing the variants, then it is an unmodified part, either by choice or because it is from an unsupported mod.

What is "Max. Thrust" as shown in the part data?

What is shown as "max. thrust" is actually "average thrust".  And in this specific case, it is the average thrust using the default grain geometry.

Do the thrust and fuel limiters work?

Yes, the thrust and fuel limiters work the same as they always have. Note that while the limiters can change the thrust and burn time, the shape of the thrust curve is unchanged. Thrust will always progress along the entire curve from beginning to end.

Does the stock delta-v readout work?

Special care has been taken to assure that the delta-v readout provides the greatest accuracy and usefulness as possible, but there are limitations.  Since Δv is independent of thrust and TWR, all Δv calculations should be correct.  The stock readout also correctly computes SRB burn time.  The thrust and TWR values shown for "sea level" and "altitude" are those at initial SRB startup (i.e. at liftoff).  The "vacuum" values are based on the average thrust.

UPDATE - Starting with KSP 1.10, the stock delta-v readout no longer correctly computes burn times for the 10-slot and special grain geometries.

Does this mod work with Kerbal Engineer Redux?

In flight mode, KER works fine, but in editor mode, the data provided is only partly reliable.  All thrust and TWR values (atmospheric, altitude, and vacuum) are those at initial SRB startup.  Therefore starting TWR is correct, but ending TWR is not.  Burn times are incorrectly computed for all but the default grain geometry.  Δv calculations should be, for the most part, correct; though errors could occur if there are staging issues resulting from the incorrect burn times.

Does this mod work with MechJeb?

I don't know.  I don't use MechJeb so it hasn't been tested.

Why is my favorite part pack excluded?

Some mods are excluded intentionally as to not disturb the internal balance of those particular mods (BDB), or because the mod is doing its own thing with SRBs (SSTU). If there are other parts packs you’d like to see included, please let me know and I’ll see what I can do about adding them.

 

Edited September 2 by OhioBob

[leatherneck6017]

On 5/25/2018 at 3:20 PM, OhioBob said:

BetterSRBs also implements the use of thrust curves. No longer do SRBs burn at a constant thrust. Thrust now rises and falls during a burn in a realistic way.

Thank you! I've been missing SRB curves in my 1.4 games. SSTU SRB's have this feature, but not for 1.4 yet.

[OhioBob]

UPDATE

Version 1.0.1

Changelog

• Revised thrust curve to work with current versions of Kerbal Engineer Redux.

See opening post for download link and instructions.

Because of a change in the way that KER computes startup thrust-to-weight ratio, it was necessary to eliminate the brief period of thrust buildup at SRB ignition.  SRBs now produce 100% thrust instantly at startup.  KER should now correctly display the startup TWR when in VAB/SPH mode.
 

Edited October 17, 2018 by OhioBob

[Warhorse]

Just a quick note - in the zip file for v1.01, the GameData folder is instead named GamaData. This did not cause me any problems, but FYI.

[OhioBob]

1 hour ago, Warhorse said:

Just a quick note - in the zip file for v1.01, the GameData folder is instead named GamaData. This did not cause me any problems, but FYI.

Yep, it sure is.  Fortunately that's not an installed folder, so it really shouldn't cause anybody problems.  Nonetheless, I've fixed it and updated the file on GitHub.  No version update is necessary.  Thanks.

[Errol]

What about adding gimbals to some of the larger SRBs like the STS had?

[OhioBob]

20 minutes ago, Errol said:

What about adding gimbals to some of the larger SRBs like the STS had?

Already been done.  I've given both the Thumper and Kickback, as well as the added SRBs, a small amount of thrust vectoring.

[JH4C]

Well here's an interesting brainteaser... Cross-posting in both threads, apologies for duplication. FAO @OhioBob

Today I installed BetterSRBs because, well because bigger rockets. However, on loading ModuleManager throws up some errors - not in BetterSRBs, but in Jet Sounds Continued!

"Hm. That's weird," I think to myself, and I quit the load, save the log, remove BetterSRBs and retry - success, no errors:

Obviously this isn't the end of the testing cycle; there could be a third party at work here, so I need to eliminate that possibility. I empty my GameData folder except for Squad, SquadExpansion, BetterSRBs, Jet Sounds Continued, and ModuleManager, and try again - and the errors are still there, albeit on fewer parts as it's not trying to patch the SXT engines. The log of this attempt can be found here, it progressed all the way to the title screen but it's still smaller and easier to decipher than the previous one.

 

As far as I can tell, the mods don't interact with each other or any common parts, so how/why this happens? All I can say is "good luck!"

Edited September 19, 2018 by JH4C

[Mecripp]

3 hours ago, JH4C said:

Well here's an interesting brainteaser... Cross-posting in both threads, apologies for duplication. FAO @OhioBob

Today I installed BetterSRBs because, well because bigger rockets. However, on loading ModuleManager throws up some errors - not in BetterSRBs, but in Jet Sounds Continued!

"Hm. That's weird," I think to myself, and I quit the load, save the log, remove BetterSRBs and retry - success, no errors:

Obviously this isn't the end of the testing cycle; there could be a third party at work here, so I need to eliminate that possibility. I empty my GameData folder except for Squad, SquadExpansion, BetterSRBs, Jet Sounds Continued, and ModuleManager, and try again - and the errors are still there, albeit on fewer parts as it's not trying to patch the SXT engines. The log of this attempt can be found here, it progressed all the way to the title screen but it's still smaller and easier to decipher than the previous one.

 

As far as I can tell, the mods don't interact with each other or any common parts, so how/why this happens? All I can say is "good luck!"

Unless it got fix 1 mod used :NEED and 1 used :For this is bad 

@PART[BetterSRB_1p875x*]:FOR[RealPlume]:NEEDS[SmokeScreen]

@PART[turboFanSize2]:NEEDS[!RealPlume]

try changing the BetterSBRs patches to 

@PART[BetterSRB_1p875x*]:NEED[RealPlume]

 

[Tyko]

Would you consider adding support for the smaller SRBs in Vens Stock Revamp? There are a couple of 0.625m SRBs that are really useful early game and a small surface attach separation motor (may not be worth doing that one since it only burns for a couple of seconds)

Thanks!

[OhioBob]

3 hours ago, Tyko said:

Would you consider adding support for the smaller SRBs in Vens Stock Revamp? There are a couple of 0.625m SRBs that are really useful early game and a small surface attach separation motor (may not be worth doing that one since it only burns for a couple of seconds)

Is the latest version of Vens still 1.9.6?  If not, can you link me to the latest.

(edit)  I just discovered that Vens doesn't play nicely with BetterSRBs.  It retextures my retextured SRBs.
 

Edited September 19, 2018 by OhioBob

[Tyko]

30 minutes ago, OhioBob said:

Is the latest version of Vens still 1.9.6?  If not, can you link me to the latest.

(edit)  I just discovered the Vens doesn't play nicely with BetterSRBs.  It retextures my retextured SRBs.

Here's the link for his current 1.4.x conversion project. It's not complete yet: https://github.com/Kerbas-ad-astra/Stock-Revamp/tree/KSP_1.4

@Kerbas_ad_astra was going to research a way to disable VSR's retexture of a certain part. There's syntax for it in the VSR config file, but it's not working as expected at the moment.

 

[OhioBob]

46 minutes ago, Tyko said:

It's not complete yet

I'm not going to add a config for something that's not complete.  When an official 1.4.x version is released, then I'll take a look at it.

Edited September 19, 2018 by OhioBob

[Tyko]

28 minutes ago, OhioBob said:

I'm not going to add a config for something that's not complete.  When an official 1.4.x version is release, then I'll take a look at it.

Understood   If I hear anything about the code to disable texture switching I'll pass it on. Thanks for all your work on ALL your KSP projects   

[OhioBob]

UPDATE

Version 1.0.2

Changelog

• Revised RealPlume.cfg to fix conflict with JetSounds.

See opening post for download link and instructions.

[Aeroboi]

So this reduces the need for MOAR boosters and is more realistic? Terrific

[MaverickSawyer]

Oooh, you have my attention now. Instant must-have pack.

[JH4C]

21 hours ago, OhioBob said:

UPDATE

Version 1.0.2

Changelog

• Revised RealPlume.cfg to fix conflict with JetSounds.

See opening post for download link and instructions.

Woohoo! Thanks @OhioBob

[OhioBob]

On ‎9‎/‎22‎/‎2018 at 1:49 AM, Oneiros said:

I love the look of those realistic thrust curves. What do you think about the smaller boosters like the stock Sepratron and the USI Sounding Rockets?

Sorry for the late reply, I just now saw your question.  I don't know too much about the USI sounding rockets, but I can take a look at them.  I wasn't planning on making changes to the sepratrons.  Any changes I'd make would probably be insignificant, and besides, people have gotten use to them as they are.  I'm also not changing the launch escape system.  The LES is balanced to perform a specific task, so I don't want to mess with it.  The sounding rockets might be similar scenario.  If they're balanced to lift a specific payload, they probably shouldn't be changed.  The only thing I want to change are the large general purpose SRBs.

[OhioBob]

21 minutes ago, Oneiros said:

Well the 0.625m sounding rocket has roughly twice the thrust and half the weight of the stock RT "Flea" booster.

That could be possible.  The Flea is short and fat compared to a 0.625m sounding rocket.  The sounding rocket is going to have a long channel down the middle with a lot of surface area.  So it's going to produce a lot of thrust and burn through its fuel quickly.  The Flea probably has less burn surface, so it's going to produce less thrust.  But it will burn longer because there is more thickness to burn through.

[theonegalen]

1 hour ago, Oneiros said:

Well the 0.625m sounding rocket has roughly twice the thrust and half the weight of the stock RT "Flea" booster. So it doesn't seem very balanced. It would be cool if they were more realistic.

One thing to keep in mind is that in real life, solid rocket boosters burn from the inside out, not from top to bottom or bottom to top. This means that you get more thrust by increasing the length of the rocket, and more burn time by increasing the width. So that actually make sense.

[Jacke]

49 minutes ago, theonegalen said:

One thing to keep in mind is that in real life, solid rocket boosters burn from the inside out, not from top to bottom or bottom to top. This means that you get more thrust by increasing the length of the rocket, and more burn time by increasing the width. So that actually make sense.

The cross section of solid fuel boosters is actually more complex than that, commonly with star-shaped bores or others to give them steady thrust over time or even decreasing thrust to reduce acceleration increase with the lower mass near the end of burn.  The cross section and formulation of the fuel grain is adjusted to give whatever thrust versus elapsed burn time is desired.

https://en.wikipedia.org/wiki/Solid-propellant_rocket#Grain_geometry

Edited October 4, 2018 by Jacke

[OhioBob]

2 hours ago, Oneiros said:

In terms of "throttling" or thrust limiting SRBs, is the stock implementation realistic?

To a point, yes.  But not to the extreme that you can thrust limit them in the game.  There are things that can be done with the geometry of the fuel to increase or decrease thrust.  Also the fuel formulation can change.  A catalyst can be added to increase burn rate, or a suppressant to decrease burn rate, which will increase or decrease thrust respectively.  I'm fine with having a thrust limiter, but it would make more sense to me if it were restricted to a narrower range, not the current 0-100%.  I may have to investigate to see if that's possible; it would be worth adding to BetterSRBs.  I see that there's a minThrust setting in the cfgs, perhaps that places a limit on how far the thrust slider can go.  I'll experiment when I get a chance.

[OhioBob]

9 hours ago, Oneiros said:

Yeah I think that will work on solid fuel rockets - I remember trying it ages ago. It works that way on LF engines, and I've implemented reduced throttle range for many of them in Unmanned Tech by increasing minThrust.

I just tested it.  The thrust limiter slider always goes from 0 to 100, but the thrust varies from minThrust at 0 to maxThrust at 100.

[OhioBob]

UPDATE

Version 1.0.3

Changelog

• Changed RT-5 and RT-10 internal names to match KSP version 1.5.

See opening post for download link and instructions.

Please note that BetterSRBs 1.0.3 is not compatible with KSP versions older than 1.5.  For older KSP versions, use BetterSRBs 1.0.2.