Solid rocket fuel

[How to: KSP]

Listen. Can you feed solid fuel into boosters?

[solarbearman]

Nope, you can't transfer solid fuel

[How to: KSP]

Yeah, but can you use fuel lines to asparagus stage the booster.

[Hary R]

8 minutes ago, How to: KSP said:

Yeah, but can you use fuel lines to asparagus stage the booster.

The principle is that solid fuel is "solid" (I know), in real life it's close to gun power and it can not be pumped around. It's the same in KSP, solid fuel can't be pump around, All you can do is ignite it and watch the firework:

https://en.wikipedia.org/wiki/Solid-fuel_rocket

http://inventors.about.com/od/rstartinventions/a/SolidPropellant.htm

To be clear No, no solide fuel fuel line.

Edited June 7, 2016 by Hary R

[How to: KSP]

Well then, the dreams of creating solid asparagus boosters are over

[Overland]

you can mod it, switch its fuel to air intake  it'l flame out when it runs out of air though but be.. well.. not very useful in the atmosphere since you couldnt shut it off.. but!.. thats just kerbal

 

[Snark]

Moving to Gameplay Questions.

[FullMetalMachinist]

2 hours ago, How to: KSP said:

Well then, the dreams of creating solid asparagus boosters are over

Well, not entirely. While you can't have solid boosters share fuel like asparagus, there is a way to make them act and stage away like asparagus. It's pretty involved to get it working right, but it's lots of fun (I think). Warning, wall of text incoming. 

It takes a lot of trial and error if you don't have a mod that gives you TWR in the VAB (like Mechjeb or KER). 

Here's what you do (for all this I'm assuming that you'll use the solids stage just as a first lifter stage, and have a second LF-O stage, plus payload). 

1) Put a center booster (either solid or liquid fuel, whichever you prefer) 

2) Put a pair of radial decouplers in symmetry on that center booster. Attach a solid booster of your preference. This will be set "C". 

3) Hold the <mod> key (alt for Windows) and click on the radial decoupler. This will copy the decoupler and the booster attached to it. Place another pair so that it will be evenly spaced as if there were 6x symmetry on. This will be set "B". 

4) Copy the decoupler/booster combo again and place on the core in the empty spot. Make sure that all 3 pairs are evenly spaced, as if you had set them all at once using 6x radial symmetry. This will be set "A". 

5) Now comes the tricky part. Set the staging so that the core and all 3 sets of radial boosters fire together. Then put the decouplers for set A in the next stage, then set B in the next stage, and then set C in the next. 

6) Now right click on a set A booster and make sure the thrust limiter is set to full. Then right click on set B and put it somewhere lower, maybe around 80%. Then set C at around 60, and the center something like 40. The thrust limits will vary depending on the rest of the ship, so you'll just have to play with it. This is why it's helpful to have a TWR readout in the VAB. if you set the staging properly, it will tell you the TWR at the start, and take into account all the fuel that burns when you stage away each booster set. Set the thrust limiters so that at the start of each stage you have a TWR of around 1.4. 

7) When you launch, it should go something like this. First stage starts all the radial boosters and the center. Set A had it's limiter set to full, so it's fuel runs out first. When it does, stage to drop set A, and everything else keeps burning. Then set B runs out, so you stage those away. Then set C,  until all that's left is the center, burning at a low thrust limited setting, so it's fuel lasted the longest. When it's done stage it away and continue as normal. 

(Credit given where credit is due. I had played with this idea a little, but it was @Snark (who calls this "poor man's asparagus") who posted this method in another thread and finally filled in what I was missing to make this work.) 

[Snark]

55 minutes ago, FullMetalMachinist said:

It takes a lot of trial and error if you don't have a mod that gives you TWR

Or a pocket calculator.    TWR is:  take the total thrust of the engines, divide by 9.81 (i.e. Kerbin surface gravity), divide by the total mass of the ship.

Yes, it involves some button-punching, so it won't be everyone's cup of tea.  But it's not prohibitive and doesn't require a spreadsheet (unlike some of the more fancy calculations that KER provides for you). Maybe I'm biased, since I happen to really like button-punching.

I use this approach with SRBs all the time, but I'm not as fancy as Machinist about it. 

I generally only have an A and a B group.  If I have, say, 8 radial SRBs, then  I'll put a set-of-4 as my A group, and another set-of-4 as my B group, rotated 45 degrees from A.  Launch on A+B, then stage away A, then stage away B and ignite my liquid-fueled center stack when B runs out.