Booster strategy, liquid fuel in addition to srb?

[Buster Charlie]

34 minutes ago, Brainlord Mesomorph said:

jeez. touchy.

and sure, year 16 and 35 mill in the bank, none of it matters.

(heck you get to use the ion thrusters!)

EDIT: hi slash, the OP was asking if recoverable boosters were a waste of time, IMHO: no

EDIT 2: maybe I (and perhaps other KSP players) identify to personally with NASA's budget problems!

NOOO.

 

 

OP uses stage recovery, and goes to stupid lengths to make even my 2nd stage booster a mini drone that can limp home for recovery after deploying the payload in minmus or mun orbit.

 

It's super easy to strap a parachute on my SRB and away we go. I normally do this if i don't get satisfactory TWR on my core stage but don't want to complicate a standard booster design, or if I just want a bit of extra kick to get the whole crazy train started straight and fast.  However I just noticed usually SRB kick the TWR way overboard, and throttling them normally ends in them getting into issues with rocket collisions if they follow the orbit too high, and lower stage recovery results.

So because of that I try to ditch the SRB before the rocket starts to turn so much the boosters can't cleanly separate without a septron.

So then the issue is, if I'm using a smaller SRB, it's not giving the core as much of a boost. But on the flip side, if the smaller SRB has enough thrust to boost the core stage AND carry extra fuel without decreasing performance then my core stage will separate from the boosters will a full fuel load. 

 

But then like others have said, is this just complicating the design? Why not use more powerful core stages? Who knows.

 

It's all just me trying to optimize the rocket for the sake of the art of it, not any gameplay mechanic reason. I like elegant designs that look like real rockets, not pancakes, but I don't mind going a little extravagant now and then...

 

[mattinoz]

3 hours ago, Skalou said:

Also, with a fuel line trick it initiates the gravity-turn without using the gimbal! (probably not the most efficient but really fun to make it works)

Wait so your rocket literally falls over so that it misses Kerbin? Seems so much like a Douglas Adams quote.

[Buster Charlie]

29 minutes ago, FancyMouse said:

I love hybrid launch stage because (1) stock SRB has no gimbal and (2) pure SRB often gives me too-big acceleration at the end of the stage.

And of course I put a dip of LFO on top of my SRB to feed central liquid engine. Oh someone's going to offer hybrid SRB with LFO? I'll buy it.

So whats the best way to handle this? There are tons of mods and stock SRB, I could maybe do some custom textures for existing models and try to make a custom config version of existing SRB (Lisence allowing) to replace some of their SRB Propellant with LFO mix. I think the most elegant method would be to maybe piggyback with one of those fuel switcher mods and allow one of the fuel load-outs to be a hybrid, with appropriate texture swapping. ANyone who's handy with writing this sort of mod, i'd be happy to do some custom textures to make them distinctive. 

[HebaruSan]

I found it a very fun design style to work with. I came to think of it as a lower-guilt cousin of asparagus; rather than a complex fuel pump that has to feed its own engine and send fuel to another tank at a possibly unrealistic rate, we've got separate tanks that just feed each other, mostly according to "gravity", while the SRB is at work independently below. If it wasn't KSP you could set up separate LFO tanks without crossfeed on the same nacelle to do the same thing, but I'll take this as a convenient next-best.

For the tuning of the timing, I rely on KER. Once I have the staging set up how I want, I look at the time per stage, and add LFO till the duration of the first stage starts increasing; that's when the LFO starts to dominate the SRB. Then decrease LFO again slightly till the time just stops decreasing; that's when the SRB dominates again. And that's where I leave it.

[Buster Charlie]

1 minute ago, HebaruSan said:

I found it a very fun design style to work with. I came to think of it as a lower-guilt cousin of asparagus; rather than a complex fuel pump that has to feed its own engine and send fuel to another tank at a possibly unrealistic rate, we've got separate tanks that just feed each other, mostly according to "gravity", while the SRB is at work independently below. If it wasn't KSP you could set up separate LFO tanks without crossfeed on the same nacelle to do the same thing, but I'll take this as a convenient next-best.

For the tuning of the timing, I rely on KER. Once I have the staging set up how I want, I look at the time per stage, and add LFO till the duration of the first stage starts increasing; that's when the LFO starts to dominate the SRB. Then decrease LFO again slightly till the time just stops decreasing; that's when the SRB dominates again. And that's where I leave it.

I actually really like that, it's a nice use of the MK2 adapter to provide a nice clean engine cluster, and it's thinning lines work with the added bulk of the boosters. Very... fish like?

[HebaruSan]

11 minutes ago, Buster Charlie said:

I actually really like that, it's a nice use of the MK2 adapter to provide a nice clean engine cluster, and it's thinning lines work with the added bulk of the boosters. Very... fish like?

Thanks! In that case, some exclusive launch-porn, just for you:

Spoiler

 

[Nich]

So if you really want to go cheap you have to design SSTO plane payloads which is a challenge in its self.  My 50% payload fraction SSTO spends 65.4 funds/t.  A larger version that supports larger less dense payloads 35% payload fraction still only cost 95 funds/t.  I would love to see what the payload fraction winners are paying.

[wumpus]

14 hours ago, Buster Charlie said:

But then like others have said, is this just complicating the design? Why not use more powerful core stages? Who knows.

How complicated is it?  Assuming you have kerbal engineer (and since you are playing with at least one other mod, you should have it), you will see the "burn time" of the SRB (about 1 minute for a kicker).  Create a "fake stage" with just your main (stage 1) engine and 1.25m (same size as the SRB) tanks.  Keeping adding fuel to the fake stage (basically one tank per SRB) until you have a burn time equal (or just under, you might want to remove some fuel) to the SRB.  Now remove the "fake stage" and distribute the fuel tanks to the SRBs.  Simple.

Total cost: the time it took to do the above (trivial)

* 300 funds per pair of fuel tanks for the fuel line.

* Possibly an extra strut (you probably need the same number with or without fuel).

The only drawbacks would be compared to alternate strategies:

Build a first stage entirely out of SRBs.  Save the cost of fuel lines and only use one decoupler.  Good for smaller builds where that decoupler matters and for those not using your recovery mod.

Build a first stage that burns out with the SRBs.  Saves all the costs of above (including decoupler costs) and lets you switch engines to a lighter more vacuum friendly one.  Basically the same level of complexity that you are asking about, but which is better entirely depends on what your primary engine is, and what you do with it (do you recover it?  If not, recovering a mainsail and switching to a Poodle can be huge.)

Basically I think it is a no-brainer to add drop tanks to SRBs in stage recovery if you are taking your main engine well into space (or recovering some other way).  If you are getting "nearly all the recovery" from the SRBs but not the main engine, you might want to dump the engine as well.

[Buster Charlie]

Well my core stage, I usually eject it sub orbital. And get a penalty for its distance from ksc. It keeps things simple,  I like to keep my payload stage short to allow it to rotate quickly without using rcs.

Another strategy I've done a couple of times using smart parts was to eject the core stage when at 60 or 70k, tell it to face retrograde and burn the rest of the fuel, the result was an almost space x style recovery,  but I found the timing unreliable. So now if I want max recovery,  I boost the into onto circular orbit, separate the payload stage, and use a probe core and reaction wheel to deorbit the core stage when it will reenter near ksc for better recovery