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[1.5 - 1.10.1] BetterSRBs [v1.2.4] [10 Oct 2020]


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4 minutes ago, zxzx said:

Can this work on RO/RSS

I don't know, but I wouldn't recommend it.  As I understand it, RO does it's own part modifications and is balanced specifically for RSS.  I have no idea how BetterSRBs would interact with that.

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  • 1 month later...

UPDATE

Version 1.2.2

Changelog

  • Deleted SRB upgrades.

See opening post for download link and instructions.

It was discovered that part upgrades and B9 Part Switch were not playing well together, so I took the easiest solution and deleted the part upgrades.  Instead of getting a performance upgrade when discovering General Rocketry, early game SRBs now have constant performance that is a compromise between their previous low and high values (new specific impulse is 215 s SL / 235 s vac.).  Be advised that this could impact previously built rockets using these parts.  The SRBs affected by this change are:

Stock:  RT-5 Flea, RT-10 Hammer
KW Rocketry:  Globe I SRB
ReStockPlus:  RT-1 Mallet, RT-2 Striker


 

Edited by OhioBob
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Love the mod! Been waiting for something similar to this to pop up.

I do have a question regarding the mod, though. Is it possible to at some point create custom thrust curves for those motors in-game, or would that be beyond the scope of this mod?

Would it also be compatible with creating our own custom thrust curves if we wrote up our own configuration files for certain grain configurations? (I guess it would also prompt me to figure out how to actually make custom thrust curves for the motors)

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2 minutes ago, Astrofox said:

I do have a question regarding the mod, though. Is it possible to at some point create custom thrust curves for those motors in-game, or would that be beyond the scope of this mod?

Would it also be compatible with creating our own custom thrust curves if we wrote up our own configuration files for certain grain configurations?

BetterSRBs already comes with four different thrust curves.  If you have B9PartSwitch installed, just right click on the SRB and there are four "fuel grain" variants from which you can choose, each with its own thrust curve.  If you don't have B9PartSwitch installed you'll get a single default curve for everything.

You can also certainly write you own config to add more grain options and thrust curves.  But if you want to be able to create custom thrust curves on the fly from within the game, that's not possible nor will it be.  That's a level of complexity that's beyond the scope of what I want to do with this mod.
 

 

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  • 3 weeks later...
39 minutes ago, rcollier said:

Anyone having issues with SRBs immediately flaming out at launch with this latest update? The only SRB that fires when testing all at once is the seperatron.

I haven't had any problem.

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  • 1 month later...

UPDATE

Version 1.2.3

Changelog

  • Updated for KSP 1.10.1.

See opening post for download link and instructions.

Be advised that starting with KSP 1.10, the stock delta-v readout no longer correctly computes burn times for the 10-slot and special grain geometries.  The 6- and 8-slot geometries appear to be unaffected.  I can't make enough sense of the new numbers to figure what has changed or how to fix it.  For you information, the burn time of the special geometry should be the same as the 6-slot, and the burn time of the 10-slot should be 2/3rd that of the 6-slot.

 

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  • 2 weeks later...

@OhioBob, I noticed that this soft-deprecates the 1.875m SRB from Missing History.  I was thinking that keeping it in may complement your 1.875m boosters by providing a smaller alternative.  Given that the MH variant then takes your version of the Thumper and increases the mass and maxThrust 2.5x, do you have a sense if that would keep the SRB in balance with your altered SRBs or would it require further alterations?

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6 hours ago, hemeac said:

@OhioBob, I noticed that this soft-deprecates the 1.875m SRB from Missing History.  I was thinking that keeping it in may complement your 1.875m boosters by providing a smaller alternative.  Given that the MH variant then takes your version of the Thumper and increases the mass and maxThrust 2.5x, do you have a sense if that would keep the SRB in balance with your altered SRBs or would it require further alterations?

The "Ram" from BetterSRBs and the "Stomper" from Missing History are both just copies of the "Thumper", though the Stomper is shorter (only 1.11x in length rather than a full 1.5x).  Even though the Stomper is shorter, at the time I created BetterSRBs, I thought they were just too similar to keep two copies of the same thing.  But you make a good point that has me reconsidering.  We also now have the "Pollux" (for those who own Making History), which falls between my SRBs in size.  So if I brought the Stomper back, we'd have four 1.875-m SRBs that would cover a good range of sizes:  Stomper > Ram > Pollux > Lance.

If I were to bring the Stomper back, I'd redo its stats using the same calculations that I've applied to all SRBs.  So the Stomper would not have the same performance that it does in Missing History.  It would end up being slighter larger than the Kickback in fuel load and total impulse, but slightly lower in thrust.

Edited by OhioBob
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Also thanks to you and Sigma and Jade for developing this amongst your other work.  Your set of mods really help with the immersion in the game without breaking the fun.  Hoping to eventually make it to Grannus without hyperedit so can test out Heatshifter, but I had also grabbed your venus-like atmosphere config for Eve in Better Atmospheres, so am excited to see how that goes.

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  • 1 month later...

If you are looking to add mod support in an update, the Mk2 and Mk3 Stockalike Expansions have a couple of SRBs in each pack.  The Mk2 are unique in that they are air-augmented solid rocket boosters.  The Mk3 has a fairly close equivalent to the Pollux, so not sure if adding BetterSRBs would provide a lot of value, but I threw together a quick config that made it a bit lower thrust, but higher ISP to try and differentiate it slightly. 

Edited by hemeac
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  • 3 weeks later...

Has anyone created a thrust curve config that's completely flat (i.e. starts at 100% and stays there the whole time as for stock)? It's going against the purpose of the mod a bit, but might help with compatibility with stock or downloaded crafts that use SRBs.

If not, can someone explain what the numbers mean?

thrustCurve
                    {
                        key = 0 0.1 0 35
                        key = 0.03 0.801 0.76 0.76
                        key = 0.61 1.2418 0.76 -0.62
                        key = 1 1 -0.62 0
                    }

I'm guessing the first number is how much fuel is remaining, and the second is the relative thrust being produced, but the other two I have no idea.

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38 minutes ago, jimmymcgoochie said:

Has anyone created a thrust curve config that's completely flat (i.e. starts at 100% and stays there the whole time as for stock)? It's going against the purpose of the mod a bit, but might help with compatibility with stock or downloaded crafts that use SRBs.

I've never considered that.  Of course just having a flat thrust curve doesn't do anything to provide compatibility with stock because other stuff changes too, like thrust and specific impulse.  It would probably be feasible to make one of the fuel grain options "stock compatible" that would change everything back to the stock values, but that's not something I'm interested in doing.

 

38 minutes ago, jimmymcgoochie said:

If not, can someone explain what the numbers mean?

thrustCurve
                    {
                        key = 0 0.1 0 35
                        key = 0.03 0.801 0.76 0.76
                        key = 0.61 1.2418 0.76 -0.62
                        key = 1 1 -0.62 0
                    }

I'm guessing the first number is how much fuel is remaining, and the second is the relative thrust being produced, but the other two I have no idea.

You are correct, the first number is the fraction of fuel remaining and the second is a thrust multiplier.  The third number is the slope in and the forth number is the slope out.  For instance, we can see that the slope between the third and fourth keys is, (1-1.2418)/(1-0.61) =  -0.62.  Here it happens to be a straight line but it need not be.  By changing the slopes we can produce curved segments between keys.
 

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  • 2 months later...

Out of curiosity, what propellant parameters (burn rate coeff, pressure exponent, combustion chamber temp, specific gas constant, molar mass, and propellant density... basically parameters I can stick into OpenMotor) were determined for the solid rocket motors? I have to ask because I am looking into potentially making some motors for KSP (a mod for sounding rockets and in general smaller parts) and it would be a great help to have those numbers to design some motors around.

 

Sorry if this question has been asked before and I missed the response to it.

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16 hours ago, Astrofox said:

Out of curiosity, what propellant parameters (burn rate coeff, pressure exponent, combustion chamber temp, specific gas constant, molar mass, and propellant density... basically parameters I can stick into OpenMotor) were determined for the solid rocket motors? I have to ask because I am looking into potentially making some motors for KSP (a mod for sounding rockets and in general smaller parts) and it would be a great help to have those numbers to design some motors around.

When I did the calculations for the SRBs I simplified things somewhat and didn't really get into that level of detail.  But I do have all those parameters from when I computed the thrust curves.

Burn rate coefficient = 5.6059          // pressure in MPa, burn rate in mm/s
Pressure exponent = 0.35
Combustion chamber temperature, average = 3330 K
Combustion chamber pressure, average = 4.5 MPa
Propellant density = 1500 kg/m³

Specific heat ratio and molar mass become messy because there are solids in the exhaust.  It's not a clean cut as when the products are all gaseous.  I'm not familiar with OpenMotor, so I'm not sure what information you require.  The method I used in my calculations are those presented by Richard Nakka in his Experimental Rocketry web site, which I've reproduced in part on my web site:

http://www.braeunig.us/space/thermo.htm#condensed

Here are the average values used:

Specific heat ratio, gas = 1.270
Specific heat ratio, mix = 1.176
Specific heat ratio, 2-phase = 1.070
Molecular mass, gas = 18.97 kg/kmol
Molecular mass, effective = 27.67 kg/kmol
 

Edited by OhioBob
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11 hours ago, OhioBob said:

[snip]

 

I take the burn rate coeff is in in s^-1 psi^-n ? Would seem rather high for m s^-1 Pa^-n, but I guess this is Kerbal we're talking about. 4.5 atm also seems incredibly small when compared to the chamber pressures some motors can get to (~50 atm or even higher), though again I guess this is also just Kerbal.

I just wanted a bit of clarification on units, and I also just find them to be really interesting.

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2 hours ago, Astrofox said:

I take the burn rate coeff is in in s^-1 psi^-n ? Would seem rather high for m s^-1 Pa^-n, but I guess this is Kerbal we're talking about. 4.5 atm also seems incredibly small when compared to the chamber pressures some motors can get to (~50 atm or even higher), though again I guess this is also just Kerbal.

I just wanted a bit of clarification on units, and I also just find them to be really interesting.

I made a mistake there on the pressure; it's 4.5 MPa (or about 44.4 atm).  Of course that's the average; the maximum can be considerably greater.

I don't know off the top of my head what the units are for the coefficient, but I do know it's calibrated to take pressure in MPa and give burn rate in mm/s.

By the way, the coefficient and exponent are the values for the Space Shuttle SRBs.  NASA publications give the coefficient as 0.0386625, but that's for pressure in PSI and burn rate in inch/s.  I converted it to metric.

Edited by OhioBob
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  • 2 weeks later...

Wow - I love This Mod so Much, definitely a Keeper!

However I Would love to see support For Redirect as their SRBs are Correctly Sized for The STS and the Look Hella Cool

Keep  up the Good work!

 

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5 hours ago, Ollz said:

However I Would love to see support For Redirect as their SRBs are Correctly Sized for The STS and the Look Hella Cool

reDIRECT is the type of parts mod that I want to avoid making changes to.  Its parts are designed to work together in a very specific way.  Changing the stats of some of those parts would upset the balance.

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On 1/8/2021 at 2:51 PM, OhioBob said:

reDIRECT is the type of parts mod that I want to avoid making changes to.  Its parts are designed to work together in a very specific way.  Changing the stats of some of those parts would upset the balance.

No Problem Then! 
I understand that they work with each other in a specific way so that’s fine by me

thanks again 

PS - sorry for responding so Late

 

Edited by Ollz
needed to add extra info
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