SRBs vs KSP SRB

[farmerben]

I've heard that the primary reason for solid rocket boosters on the shuttle was to ensure continual solid rocket production needed for nuclear ICBM's.  As we've seen modern was depends on production, stockpiles that seem excessive in peace time, can quickly be used up.  

For me, the space shuttle design is among the most difficult challenges in KSP.  It's ridiculous to make work compared to many symmetric alternatives.

[magnemoe]

3 hours ago, sevenperforce said:

There is more hydrogen in a gallon of liquid gasoline than in a gallon of liquid hydrogen.

In real life, there are plenty of vacuum SRBs. The Star 48 is one of the most popular:

Vacuum-optimized nozzle which gives it 286 seconds of specific impulse -- better than the sea level impulse of a Merlin 1D. Because they are so dense, they work well as terminal kick stages to fit inside a fairing with a payload. The Star 48 was the final stage of the Delta II launch vehicle and it was also used on top of the Centaur on the Atlas V 551 that launched New Horizons to Pluto.

These kick stages can either be spin-stabilized or they can have TVC.

I've always thought it would have been cool to have segmented SRBs in KSP. Choose a segment size, a number of segments, and a nozzle size/design. That way you could have a dense, low-thrust, high-efficiency kick stage, if so desired. 

Knew about them but did not know they was pretty common for deep space missions. 

[mikegarrison]

1 hour ago, farmerben said:

I've heard that the primary reason for solid rocket boosters on the shuttle was to ensure continual solid rocket production needed for nuclear ICBM's.

I am fairly confident that this is not true.

4 hours ago, sevenperforce said:

I've always thought it would have been cool to have segmented SRBs in KSP. Choose a segment size, a number of segments, and a nozzle size/design. That way you could have a dense, low-thrust, high-efficiency kick stage, if so desired. 

And as a bonus, you could sometimes burn through the segments and blow up your rocket!

The segments on the Shuttle were only there to make the SRBs easy to transport. Having them segmented added cost, weight, and as we all know now, risk.

[sevenperforce]

24 minutes ago, mikegarrison said:

The segments on the Shuttle were only there to make the SRBs easy to transport. Having them segmented added cost, weight, and as we all know now, risk.

Was it ease of transport, or possibility of transport?

As I understand it, there literally would not have been any way to transport the SRBs to the pad if they were constructed and filled with propellant without segments.

[mikegarrison]

Just now, sevenperforce said:

Was it ease of transport, or possibility of transport?

As I understand it, there literally would not have been any way to transport the SRBs to the pad if they were constructed and filled with propellant without segments.

I believe "ease" is the correct word. They could have been made somewhere that could be accessed by barge, but IIRC they were made inland and were shipped by rail.

[sevenperforce]

Just now, mikegarrison said:

I believe "ease" is the correct word. They could have been made somewhere that could be accessed by barge, but IIRC they were made inland and were shipped by rail.

I wonder if transporting them by barge would even have been viable. Unlike the external tank, which could be transported by barge quite readily because it weighed less than 27 tonnes empty, the SRBs had a mass of over 700 tonnes each. The Pegasus Barge just barely had enough draft to maneuver up the canal by the Saturn Causeway and into the Turning Basin to drop off the tank.  A barge holding a booster that was narrower than the external tank but 25 times heavier would have a much greater draft.

[magnemoe]

1 hour ago, farmerben said:

I've heard that the primary reason for solid rocket boosters on the shuttle was to ensure continual solid rocket production needed for nuclear ICBM's.  As we've seen modern was depends on production, stockpiles that seem excessive in peace time, can quickly be used up.  

For me, the space shuttle design is among the most difficult challenges in KSP.  It's ridiculous to make work compared to many symmetric alternatives.

SRB makes lots of sense for rockets as its easy to get high trust at launch with them cheaper than liquid fueled stages as long as you don't recover stages. 
I uses them a lot in KSP, one tricks you can use in KSP is to have 4 or more and have them at variable trust levels, first is at max trust with second has lower and burns longer. 
Now I agree the TWR is a bit low in KSP, and you can always reduce trust. 

[magnemoe]

40 minutes ago, mikegarrison said:

I am fairly confident that this is not true.

I say its in part true, you need the solid rocket fuel factory for the solid fuel ICBM as they have an expiration date. But I'm pretty sure the shuttle SRB is very different from an ICBM who has many stages. 
This might be an added reason for the segmenting. Facility was not set up to make an very long SRB. Solid rocket motors are also used in rocket artillery but this might be as different from gunpowder in pistols and artillery. 
 

[JadeOfMaar]

3 hours ago, Hannu2 said:

I would like realistic thrust curve, like real SRBs.  For example Shuttle's SRB begins at full thrust, decreases during max Q, increases again and then decreases smoothly to keep acceleration in limits.

OhioBob and I created a mod way back which uses B9PS to provide thrust curve selections to the SRBs from Squad and some part mods. It should be quite satisfactory.

 

3 hours ago, sevenperforce said:

It would also be cool to be able to construct thrust curves using multiple segments in your booster with different burn rates.

I believe this mod allows for scaling thrust with tank length so it's very worth a try. I can't speak for thrust curves, though.

 

5 hours ago, sevenperforce said:

Shockingly deep.

As deep as where the Kraken or the kaijuu come out of, holy fish sticks!

 

19 hours ago, Richmountain112 said:

I'm wondering why there are no Vacuum SRBs, ones that are optimized for Vacuum operations, and (maybe) can be shut down. It would be kinda useful for Tylo landers.

Outside of Bluedog Design Bureau, it would appear no one is interested in SRMs for cases other than launch vehicles. Ones that can be shutdown and restarted are hybrid solid where the fuel might be sculpted pure alkali metal and the oxidizer is a pumped liquid (namely, LOx). To stop the SRM, simply stop pumping the oxidizer.

Edited May 8, 2023 by JadeOfMaar

[Richmountain112]

Yeah. A vacuum SRB probably would be OP for Tylo, even if it can be shut down but can't restart.

Edited May 8, 2023 by Richmountain112

[Nori]

3 hours ago, JadeOfMaar said:

OhioBob and I created a mod way back which uses B9PS to provide thrust curve selections to the SRBs from Squad and some part mods. It should be quite satisfactory.

 

I believe this mod allows for scaling thrust with tank length so it's very worth a try. I can't speak for thrust curves, though.

 

As deep as where the Kraken or the kaijuu come out of, holy fish sticks!

 

Outside of Bluedog Design Bureau, it would appear no one is interested in SRMs for cases other than launch vehicles. Ones that can be shutdown and restarted are hybrid solid where the fuel might be sculpted pure alkali metal and the oxidizer is a pumped liquid (namely, LOx). To stop the SRM, simply stop pumping the oxidizer.

BetterSRBs is a great mod. At the time I made this post I don't believe it was around but I do recall I used SpaceY pack which had some nice large SRBs and I used Tweakscale back then.
I have a KSP folder on my computer.. All of the versions I played from 0.16 up. It's a fun trip down memory lane to look through it, though I don't have many of my saves from those times...

[Nori]

Oh I should add, procedural parts adds a variable size SRB and it's extremely nice.

[OhioBob]

22 hours ago, JadeOfMaar said:

Outside of Bluedog Design Bureau, it would appear no one is interested in SRMs for cases other than launch vehicles. 

They are rare, but I have found a couple mods that include vacuum SRMs.  NovaPunch has two (Advanced Solid Booster-Derived PAM - Mini, and Advanced Solid Booster-Derived PAM), and RLA ReBorn has one (SMAC Payload Assist Motor).  All are small low-thrust motors.