Biggest SRB's ALWAYS destroy main tank.

[Talavar]

No matter WHAT I do, when the SRB's detach they ALWAYS destroy my main fuel tank. If they barely even touch my main fuel tank, it explodes. I've tried repeatedly OVER AND OVER to build a ship that will detach the biggest srb's and survive. it always fails. Ive even tried using tons of sepratrons and it STILL blows my tank. a slight glance from a spent srb shouldnt destroy my ship!

[astroboy820]

Try using Sepratrons pointed away from the main tank near the center of the mass of the SRB and set it to stage the same time as the decouplers.

[Talavar]

I added mechjeb and tried it.. still having the problem.. check it out.,. I guess this vid deosn't belong in "unmodded" anymore, but still it was doing it BEFORE I added Mechjeb.. check it out...

[Claw]

Pull up the F3 menu and see what's actually destroying the tank. It's unclear to me if it's the SRBs making contact, if the sepratrons are causing a problem, or if the tank is getting crushed by the acceleration of the main engine. Pulling up the F3 menu will (hopefully) tell you the what's causing damage to the tank.

~Claw

[astropapi1]

Looks like the sepratrons are overheating the fuel tanks and making them explode. Try angling (is that a word?) them outwards and see if the problem persists.

[Talavar]

Doing all of this now.. i'll fill you in shortly.

[Talavar]

Looks like the sepratrons are overheating the fuel tanks and making them explode. Try angling (is that a word?) them outwards and see if the problem persists.

Checked the F3 Menu.. Tank exploded due to overheating from the sepratrons. Wouldnt think they would do that so easily... almost makes seperatrons useless..

Edited August 31, 2014 by Talavar

[Claw]

I think there's a couple parts that don't move heat very well. So when something like that gets pointed at them, they simply overheat instead.

~Claw

[Wanderfound]

Checked the F3 Menu.. Tank exploded due to overheating from the sepratrons. Wouldnt think they would do that so easily... almost makes seperatrons useless..

Not really; they work fine when set up properly.

As others have mentioned, you need to angle them so that the exhaust doesn't hit the core. They are SRBs themselves, after all; they're fast burning, but they aren't weak. Don't try to kick outwards only; set them so that they push down as well as out, and bias the balance so that the top of the booster gets slightly more kick than the bottom. Using the alt key in the VAB to fiddle the angles in 5° increments is important.

Once you get the hang of it, you can make your spent boosters do coordinated aerial ballet on the way down. If I get the time, I'll make a demonstration rocket today and post screenshots of how to set it up.

[Motokid600]

Isnt there a bug with the decouplers causing ejected stages to fall inward? Or was that fixed?

[raidernick]

Isnt there a bug with the decouplers causing ejected stages to fall inward? Or was that fixed?

Yes there is and no it's not fixed.

[technicalfool]

Isnt there a bug with the decouplers causing ejected stages to fall inward? Or was that fixed?

Not sure if it's a bug or a feature, but it can certainly be overcome with a single sepratron at the top of each booster. Angle them upward at 45 degrees or so if you think they might go near the central engines, but what with being at the top of the booster, they should totally miss anything heat-sensitive.

For getting rid of larger radial stages where the sepratrons will almost certainly overheat the core, I've found that just hitting X to cut throttle before getting rid of the stage works wonders. By then, you should really be going high enough, fast enough and sideways enough that a momentary loss of power shouldn't matter all that much.

Also helps to roll around so that stages get blown off sideways rather than above/below the central stack:

Do it right, and as above, sometimes you won't even need the sepratrons.

[raidernick]

It's not a "feature", it is a serious issue that has already been discussed ad nauseam in this thread: http://forum.kerbalspaceprogram.com/threads/88026

People are constantly joking off serious bugs with this game as "features" and that is perhaps the reason these things aren't being fixed. It's like the whole wobbly rocket debate and how struts are a crutch for a more serious problem.

Edited August 31, 2014 by raidernick

[Supernovy]

Lowering the amount of fuel in each sepratron to a minimum may also help prevent overheating, you'll still get thrust but for a shorter time.

[DavidHunter]

Sepratrons need to be angled so their exhaust isn't pointing toward your inner core engines.

Other tip for when you get to building bigger rockets with massive boosters: use launch escape systems mounted onto the side of the boosters instead of sepratrons.

Something like this:

Like Wanderfound said:

you can make your spent boosters do coordinated aerial ballet on the way down.

By the way... note that launch escape tower in the dead centre? That's pointed retrograde because the inner core gets me into a stable orbit, but I need to de-orbit that section, and by the time it's in orbit, it has no fuel left of its own. So that lets me de-orbit that section (parachutes also tied in on the same stage so it's all recovered and refunded using the DebRefund mod).

Edited August 31, 2014 by DavidHunter

[Wanderfound]

Okay: Sepratron demo as promised.

Note alignment of Sepratrons. One pair per booster.

Launch:

Decouple:

Spinny:

Same rocket decoupling while pitched over:

You’ll want a few more Sepratrons if you're shifting huge things like LFBs, or if you’re planning on decoupling while pitched horizontally, but in either case: they work just fine if you set them up right.

The decoupler thing is a bug that can be neutralised as simply as moving your Sepratrons a smidgeon higher. Yes, it's a bug, but it's as close to a zero-priority issue as you can get.

[Thanny]

This is absolutely the radial separator bug, and Sepratrons don't work against it (save that sometimes using a multitude of them blunts the impact enough to prevent destruction). There's a workaround that involves editing the part.cfg for each separator, and makes them actually work.

Note also that the bug disappears without modification after 750m/s, apparently because there's a different code path after that speed.

[M3tal_Warrior]

As for sepratrons: They work excellent. Let them point about 60° downwards is way enough for the biggest boosters to separate nicely from the main stage. It also helps to use TT-70 decouplers instead of the TT-38K, since the additional space adds some failure tolerance to the vessel.

With bigger stages I use sepratrons too - to prevent them overheating the main stage just patch them at the sides of your booster stages, with slightly triangular orientation instead of parallel. This way the exhaust misses the main stage and only a little thrust is neutralized. But since they have more than enough fuel it doesn't matter anyway. Launch escape systems proved too heavy (and powerful) for the task, IMHO. What DavidHunter does with two LES for each booster I do with 4-6 sepratrons.

[DavidHunter]

As for sepratrons: They work excellent. Let them point about 60° downwards is way enough for the biggest boosters to separate nicely from the main stage.

Your idea of "biggest" must be pretty small.

[M3tal_Warrior]

Your idea of "biggest" must be pretty small.

SRBs, to be precise. For the booster stages you use (and me too, for big rockets) there is always the triangular way of separation.

[Wanderfound]

Other creative Sepratron uses:

* Emergency landing brakes on large spaceplanes.

* Rapid cockpit/fuselage separation as part of an abort system.

* Cheap and light deorbiting thrusters.

* Downforce generators for ground racers.

* Short-burn Kerbal jetpacks.

* Surplus crew disposal system.

* Last moment suicide burn correctors.

* Spinny-thing makers (Kurtjmac is fond of this one).

* Fireworks.

Anything else?

[Wanderfound]

For the booster stages you use (and me too, for big rockets) there is always the triangular way of separation.

Huh?

Not familiar with that one.

[M3tal_Warrior]

Not familiar with that one.

Just using sepratrons in a slightly V-shaped pattern to avoid the exhaust burning down the main stage.

[Jikahn]

Yes, there is a bug with radial decouplers, and no, it isn't fixed. Take a rocket, strap decouplers with SRBs to it and accelerate near 750 m/s orbital velocity but do not exceed that speed, now decouple and watch them rotate inward. The closer you are to 750 m/s the more pronounced the rotation becomes. There is a work around involving editing the part configs for radial decouplers you will have to search for it, it will cause them to act like stack separators.

http://bugs.kerbalspaceprogram.com/issues/2842