Asparagus Lifter Explosion

[Duxwing]

EDIT: This question has been answered, and I want to change the thread title.

Dear Forum,

The last two boosters of my asparagus lifter when decoupled hit and thereby destroy my Munar Orbital Station; they are without Sepratrons decoupled in a 70x68km orbit while the boosters are deactivated, and my only relevant mod is Kerbal Joint Reinforcement. Below are a picture of my mission log after my latest spontaneous disassembly and a picture of my whole craft in the VAB.

How can I safely jettison the boosters?

-Duxwing

Edited December 23, 2013 by Duxwing

[DeMatt]

...Add Sepratrons. Try to get the booster -> decoupler link to be as close to the CoM of the jettisoned booster as you can, so it fires straight off instead of getting any rotation.

[Murph]

How can I safely jettison the boosters?

Assuming that the boosters are out of fuel and their engines stopped at the point of jettison, they are simply not clearing the stack. There's a bug/feature with decouplers and struts, where the decoupler force is basically removed by the presence of struts.

I've found that sometimes moving the position of the radial decoupler up to the top of the booster column can help, so that the "kick" (there does still seem to be some kick, it's just extremely weak if there's struts around) from it pushes the top of the stack out. Try with the decouplers at top, middle, and bottom of the booster columns, see if one of those positions works.

Otherwise, you're going to need Sepratrons, I think.

[Duxwing]

After sleeping I will test your advice by adding Sepratrons to the last pair of boosters.

-Duxwing

[Murph]

Oh, one other thing. While struts do cause a problem with radial decouplers, make sure that you're using the big hydraulic decoupler (the wide one, not the stand-off one), as it has more force to start with.

[SRV Ron]

Closely watch what is happening when you drop the boosters. I have found that some setups cause the spent tanks to rotate inward to hit the center column. If that is the case, a pair of sepratrons properly placed will resolve the issue. In addition, if you are doing an orbital turn during the staging, you will end up turning the ship into a staging tank. You should be going straight during staging.

[maltesh]

When radial decouplers are attatched to parts which are strutted to the craft, the struts tend to cut most of the force of the ejection.

The TT-70 radial decouplers (the ones that /aren't/ flat) tend to provide just enough standoff distance on disconnection that, although I don't use separatrons, I don't have issues with boosterscrape even when automated. I also tend to make sure that the center booster is "higher" than the radial ones to give things a little room to rotate around behind the central booster.

[Duxwing]

I tried adding Sepratrons, and my rocket exploded when its fairings decoupled (long ere booster separation). Of note: booster separation occurs when all engines are deactivated.

-Duxwing

[Duxwing]

I've figured it out! Two Gigantor XL Solar Panel arrays were intersecting the last pair of boosters, and when the boosters decoupled, the collided thousands of times per second and thereby acquired tremendous amounts of kinetic energy that hurled them from their payload, instantly destroying it. I hope that moving the panels will help.

EDIT: Or not. For some unknown reason or reasons decoupled objects want to zoom retrograde.

-Duxwing

Edited December 23, 2013 by Duxwing

[Zephram Kerman]

I was going to suggest to put your vessel into a roll maneuver during jettison, so the decoupled parts get some free momentum.

But this

EDIT: Or not. For some unknown reason or reasons decoupled objects want to zoom retrograde.

sounds more like a part clipping issue. Back in VAB, disconnect and reconnect the possible clipping parts, which should "reset" the connections and hopefully solve the problem.

[Duxwing]

But this sounds more like a part clipping issue. Back in VAB, disconnect and reconnect the possible clipping parts, which should "reset" the connections and hopefully solve the problem.

I've already tried with a fresh, simple ship and all stock parts (except the parachute).

Stage 1

Real Chutes Parachute

Mk. 1 Command Pod

1.25 meter Stack Decoupler

Stage 2

200L Fuel Tank

LV-909

1.25 meter Stack Decoupler

Stage 3

400L Fuel Tank

LV-T45

1.25 meter Stack Decoupler

Stage 4

BACC Solid Rocket Booster

Launch Clamp

I ascended to a 70x70km LKO with only Stage 2 remaining, lowered my periapsis to ~20km, pointed prograde, and decoupled Stage 2, which backward hurtled at hundreds of meters per second. Something is rotten in the state of Denmark.

-Duxwing

[Zephram Kerman]

Self-deleted, due to a much better reply from Professor Ferram!

Edited December 23, 2013 by Zephram Kerman

[ferram4]

You're using FAR. But you haven't updated to the most recent versions of FAR. This was a notable issue in v0.12, where decoupled parts would feel one physics frame of sea-level density, causing nasty things to happen in space.

Update your mods regularly, and when asking for help on a modded install, list all mods, including version numbers. It helps tracking down the possible issues.

[Duxwing]

You're using FAR. But you haven't updated to the most recent versions of FAR. This was a notable issue in v0.12, where decoupled parts would feel one physics frame of sea-level density, causing nasty things to happen in space.

Update your mods regularly, and when asking for help on a modded install, list all mods, including version numbers. It helps tracking down the possible issues.

I've downloaded the latest version of FAR, and my ship now flies beautifully! Thanks, ferram. I didn't suspect that my version of FAR was obsolete, and even though it was, I've only encountered this problem since 0.23.

-Duxwing