Stop discarded tanks hitting rocket?

[SSSPutnik]

50% of time my asparagus stages are hitting the tanks next to them when dumped. I am using the wider radial decouplers.

Do I need to put sepratrons on these? Any tips?

Edited November 18, 2013 by SSSPutnik

[KvickFlygarn87]

Well, use Sepratrons. And angle them, so they point downwards and away from the center.

[celem]

Yeah this can be an issue, especially if you are dropping the asparagus tanks during a gravity turn.

Try the whatsit manifold decoupler. Whilst it doesnt hold things as far from the main body as the wide radials, they do tend to push away harder. Its my decoupler of choice for any of the jumbo rockomax tanks

Failing that seperatrons will indeed fix the issue. You dont need a matched pair per drop-tank, just one on one side of it will suffice to push it away from the main rocket (it will spiral with a lopsided seperatron, but wont spiral fast enough to cause a tangle.)

This is especially an issue if you put tail-fins / other controls low down on the main tank, spent drop-tanks like to clip the fins on their way off, and losing one of a matched set of fins causes horrid instability

Edited November 18, 2013 by celem

[bsalis]

Well placed sepratrons can fix this. Make sure they are near the CoM of the spent stages... so basically more near the engine end, since the tank(s) will be empty.

However... it's always good to try and fix it without adding to part count and mass. Note that Struts pretty much cancel the ejection force of decouplers. Sadly they are typically not optional. Other than that it's just...

* better placement of where the radial decouplers are

* more spacing, and/or shifting the stacks down

* more careful piloting when staging

[Kasuha]

Sepatrons are useful first-aid kit if you don't want to go changing the design of the ship. Apart of that:

- use TT-70 radial decoupler for better spacing

- do not turn the rocket while staging. In general, you should turn the rocket as little as possible. Except for the pitchover maneuver, gravity turn should be driven by gravity, not by the ship

- you may consider unrolling the rocket to get stages away from the body of the rocket. My most trusty lifter looks like this after seven generations of development. No sepatrons needed because each stage naturally leans off center after it runs out of fuel:

[FlamedSteak]

Make sure your not turning during the staging and also that you're not pointing more than 15 degrees off your trajectory.

if that still doesn't work, separatrons will do the trick.

[SSSPutnik]

Yeah the earlier tanks dump during vertical ascent, however the later tanks dump during the gravity turn and again whilst out of atmosphere.

The unrolled solution above is neat, but not so realistic, I hate to think of the forces involved.

I will try the sepratrons, manifold decoupler may work but would make part placement really tricky.

I take it you would place pointy end of sepratrons facing down and away from the central tank on the inner part of the tank being dropped.

[celem]

exactly right on the seperatron placement. Dont worry about the seperatron flaming the main tank, it wont be for long enough to damage it. I position mine usually right on the 90* so that it's exhaust is pointing along the same vector as your decoupler/tank, then angle it slightly downward. This should push it directly away from the main tank, if your seperatron is low enough it shouldnt tip relative to your rocket but fly straight out (and down)

[Kasuha]

The unrolled solution above is neat, but not so realistic, I hate to think of the forces involved.

Of course that's the question: what's a realistic rocket? One that resembles real world rockets but which you'll have hard time to keep together in KSP, or one that works in KSP?

Note that sepatrons are not "real-world" realistic, too. There's no way anything could be burning against the body of the rocket, the risk of damage would be simply too high.

[SSSPutnik]

Thanks people.

No IRL you wouldn't play exhaust on a fuel tank but I believe similar rockets are used in certain circumstances.

When I build I try to pretend aerodynamics are modeled more realistically.

(Who knows when better modeling will be introduced).

Some good discussion here, ta.

[SRV Ron]

A picture of the problem rocket would help. Properly braced and not turning during staging, the boosters should just slide off cleanly on even the most complex of designs.

[KerbMav]

When separating asparagus boosters during my gravity turn I try to roll the rocket in a position the tanks can mostly fall free downwards.

Actually you could spin your rocket real fast to add force to the separation and sling the tanks away from you ...

[DrMonte]

Usually destruction is done when separation is done before fuel runs out. Even empty fuel tanks "touching" your rocket shouldn't damage it (most of the time ). Make it stronger, make it unbreakable and listen to good posted suggestions:

- keep rocket nose to your movement vector "o" when separating;

- keep outer stages lower;

- keep outer stages far from inner;

I'm not an additional boosters fan. For super heavy mounting like multiple orange tanks I use "Hydraulic Detachment Manifold" on "Modular Girder Segment" and it works fine.

[HeadHunter67]

Note that sepatrons are not "real-world" realistic, too. There's no way anything could be burning against the body of the rocket, the risk of damage would be simply too high.

In what way do they differ from real world ullage motors? They're burning against the body of a spent stage, near an area that's designed to handle the exhaust from a much larger rocket motor.

[SSSPutnik]

OK sepratrons officially rock. Fixed!

[Psycix]

AFAIK there is a bug that causes struts to nullify the decoupler force.

No decoupler force -> stage does not get pushed away -> fall straight down -> tiny rotation causes collision

Correct me if this bug is already fixed, I'm not sure.

[SSSPutnik]

Actually, bringing up the mission logs says the tanks are getting damaged by the sepratron exhaust...

[allmappedout]

Actually, bringing up the mission logs says the tanks are getting damaged by the sepratron exhaust...

Whilst they may be damaged, it might not be damaged to the point where they're broken. As long as your tanks don't explode, they will still function fine, and as long as the engines don't overheat from any exhaust being pointed at them, there should be no issue.

[celem]

Yeah, the mission log making mention of that let's you know that the exhaust is indeed playing across the tank. It doesnt imply any problems in the current edition of the game where parts have basically 2 states of damage: 'fine' and 'bang'

glad the seperatrons helped you, a lot of good hints for smooth staging in this thread

Edited November 18, 2013 by celem

[KSK]

In what way do they differ from real world ullage motors? They're burning against the body of a spent stage, near an area that's designed to handle the exhaust from a much larger rocket motor.

I don't imagine they're a great idea for detaching lateral boosters but they work just fine for inline staging. The Saturn V used retrorockets to assist with first stage separation.

[Hodo]

Thanks people.

No IRL you wouldn't play exhaust on a fuel tank but I believe similar rockets are used in certain circumstances.

When I build I try to pretend aerodynamics are modeled more realistically.

(Who knows when better modeling will be introduced).

Some good discussion here, ta.

Or you could just download the FAR mod and use that and stop pretending..lol.