How many boosters do you use (if any)?

[StrandedonEarth]

As many as I need, which tends to be in the 4-8 range. Although I do launch small comsats on a stick.

[airtrafficcontroller]

"How many moar boosters will you place?"

 

"Yes"

[Brynderion]

I mostly use a singular powerful rocket to get payloads into orbit, but I will occasionally use LF boosters or SRBs for a particularly heavy payload or to save the main stage fuel for interplanetary missions.

It's a real shame that there's a limit on what parts continue to persist in atmosphere, although I understand why it exists. It really hurts the idea of designing reusable first stages that don't quite leave the atmosphere.

Here's hoping that this will be something that KSP2 addresses in one form or another.

[RoninFrog]

72 Vectors and 9 mammoths.  Although, all those engines caused a lot of lag, so I revised it down to 29 mammoths.  I think this should fit well in the "+" part of 3+ boosters.

On 3/9/2020 at 2:38 PM, Vanamonde said:

Zero, two, or four. More than that and they start to bang into things as they're ejected. 

Solution:  Don't eject them.

[Starman4308]

With RP-1, this becomes a much more substantial question due to tooling costs. Due to that, I tend to go for a low-thrust sustainer core that can just barely get off the pad, then slap on boosters as needed for heavier payloads. This results in OLV families with 0-8 boosters, occasionally including 1-booster designs, and sometimes with alternate booster selections. For example, if I need just a little extra thrust, I may slap on 2-4 Castor 1 SRBs, whereas more demanding payloads may call for a pair of LRBs.

[VoidSquid]

On 3/9/2020 at 10:38 PM, Vanamonde said:

Zero, two, or four. More than that and they start to bang into things as they're ejected. 

Separatrons  

[noname_hero]

As some others mentioned here, it depends, but I'm mostly in the moar boosters camp. On one hand, some of my designs even use a single SRB as the lone first stage, e.g. small comsats for Mun or Minmus. On the other hand, many of my designs use boosters strapped onto boosters. I'm no great pilot, so lots of extra dV saved my kerbonaut's behinds more times than I'd like to.

Another factor others have already mentioned is the payload. A smallish early-to midgame design for LKO rescue missions gets a pair of Thumpers, but a 300-ton Eve mission ship launches on something that should melt the launch pad.

My guilty pleasure? Fleas. I know it is stupid, but often I'll go and strap clusters of three or five Fleas onto every "regular" booster. I don't bother with nose cones, given the Fleas' burn time, and I do know those Fleas will give me say 10 or 25 m/s of dV, but they add fun and noise and action to the liftoff. There's something perversely satisfying and amusing about watching those ugly flaming barrels help push the state-of-the-art nuclear-powered spaceship into heavens...

[DancesWithSquirrels]

I tend to start with a single core, then add 2-8 SRBs as needed to actually get it into orbit.

Lots of SRBs do tend to collide with the core: I greatly reduce that by:

• Moving the SRBs down so that the couplers are on the top portion of the booster, using that force to push the top of the booster away.
• Adding a 'Basic fin' to each one so that there is some outboard drag to pull the top of the SRB away from the accelerating core.

Those two tweaks work with up to 12 SRBs, although with that number you might want to add 2 Basic fins or AV-T1's to provide more separation drag.

Sepratrons also work, but they aren't available at lower tech levels, and I sometimes find them fiddly. And I've also seen parachutes staged with the coupler to pull the boosters away (haven't tried that in quite a while, not sure how well it works now).

[cubinator]

On 3/9/2020 at 10:52 AM, RealKerbal3x said:

I tend to add 2-4 boosters, test the rocket, and then realise that I have a wasteful amount of excess delta-V and remove them.

That's when you just put a docking port on it somewhere, and leave it in orbit after renaming the vessel to "FREE FUEL"

For my largest payloads, my best 'still halfway sane' solution is a powerful center core, with 2 nearly identical cores on the side* **, and on top of the center core is a vacuum optimized delivery stage with lower TWR, to be deployed when that's less important. 
I like to use one layer of asparagus, routing the boosters' fuel to the center stage radially. More than that is overkill.

I put fins on the bottom of the main stage, but here's the kicker: I also put one fin on the outer edge of each booster. The drag it produces pulls it away from your center stage in a perfect flower!

*4 if it's really big.

**6 if I literally can't stuff enough Vectors under the rocket to get enough thrust to lift off the pad, but at that point I may as well just add boosters to the boosters.

Edited March 23, 2020 by cubinator

[GummiRevolution]

Usually I use either a single core stage or a core stage with 2 or more identical boosters, but if I have just a core and need a bit more delta-V I add some SRBs. And yes, I sometimes use fleas as well. I once strapped 16 of them to an advanced reusable kiloton nuclear-gas-core lifter. Unfortunately the lag caused me to stage the boosters when they were still burning, causing the largest nuclear accident since I crashed a nuclear salt water rocket into the KSC 2 (don't ask). My new nuclear lifters use a pair of hammers with parachutes, because it's just hilarious watching 21 mighty lox-augmented gas core NTRs loft interstellar ships to orbit, aided by a pair of tiny Hammers.

[RealKerbal3x]

4 minutes ago, cubinator said:

That's when you just put a docking port on it somewhere, and leave it in orbit after renaming the vessel to "FREE FUEL"

For my largest payloads, my best 'still halfway sane' solution is a powerful center core, with nearly identical cores on the side, and on top of the center core is a vacuum optimized delivery stage with lower TWR, to be deployed when that's less important. 
 

Actually, what I've been doing recently is building standardised upper stages with docking ports and probe cores. That ensures that even if you have an excess of delta-V you can reuse the stage as a space tug, and refuel it if you need.

[KingKerb]

I usually use a powerful core with 2-6 moderately powerful Liquid Fuel boosters, mainly because they provide some extra ΔV. Otherwise, i'd probably just use a core stage.

[HansonKerman]

I’m assuming you mean SRBs. In my opinion, the core should always as strong as the core. Going to Duna? Three Thumpers, a Mainsail, a Jumbo tank 

—

get into orbit using a Skipper,  one normal gray tank and a half

—

you shpild have fuel to reach escape velocity, do that

—

NERV engine with one or two tanks

done. Who uses boosters that are moar powerful than the corr

[Whackjob]

I love boosters.   One of my favorite things is making my own boosters.

[RoninFrog]

2 hours ago, Whackjob said:

I love boosters.   One of my favorite things is making my own boosters.

Man.  7 seconds in and look at the fuel levels on the Saturn V tank.  Wouldn't want to be standing under that thing.

[Whackjob]

Right now the Arkingthaad NEXT Mk2 has 288 Mammoth motors for a combined in-atmosphere thrust of 1,078,857.216 kilonewtons and in space she'll have 1,152,000 kilonewtons.   I hope to launch tonight.  She's half built.  Delta-v at the moment is five thousand-ish.

[Dan Kerman]

I find I build my rocket, then add two boosters and away I go! Easy to add and stage and gets me into orbit with some dv to spare.

[Fraktal]

I have a lot of pre-made designs, but all too often I find mission requirements falling squarely between two designs in such a way that one is too weak but the next is too powerful.

My designs usually use 2-4 SRB or non-gimbaled boosters around a gimballed core. Sometimes I use a non-gimballed core with a gimballed upper stage, in addition to the boosters.

[TheFibonacciEffect]

Since many people voted for a pair of boosters, rather than 3+ boosters, what are the benefits from using less boosters?

[Vanamonde]

1 hour ago, TheFibonacciEffect said:

Since many people voted for a pair of boosters, rather than 3+ boosters, what are the benefits from using less boosters?

Well, for one thing, 3x symmetry tends to get squirrely when pitching and yawing. 

[adsii1970]

1 hour ago, Vanamonde said:

Well, for one thing, 3x symmetry tends to get squirrely when pitching and yawing. 

Unless you use 3x symmetry for fins, too. I often do that without any significant problems.

[Randazzo]

Depends on the rocket and payload. Sometimes it's better and cheaper to strap some boosters on versus moving up to a larger diameter stack and bigger engine.

[N_Danger]

2 Solids and a liquid core, with the burn time on the solids such that the core has a T/W of 1.5 or better at separation. 

[Curveball Anders]

I usually go with two, and then upgrade to 4 (sometimes down to three for mission adaption).

But my favorite  trick is "hybrid aspargus', 

Stacking some LF tanks on top of the boosters, adjusting so they drain first and enable cross feed.

The trick is to balance the thrust limiter on the boosters and the size of the 'drop tanks' so both run out at the same time (-ish).

Saves a bit of cash on my standard launchers that I use over and over again.

[Wizard Kerbal]

For most payloads, satellites, relays, probes, I go with a 2.5m or 3.75m core and use a skipper or rhino, then attach 2 solid boosters. If that doesn’t work, I use Large liquid boosters. If that doesn’t work, i’ll attach 4-6 overkill boosters, and if that doesn’t work, 5m time. Or 5m with as many boosters as possible, which I do for ring space stations and asteroid catchers.

Problem is, if the boosters fail to separate, your payload becomes a cloud of debris.