Centrifugal Stage Separation - anyone else do it?

[The Ideal Gas Lawyer]

After having lots of trouble with spent radial stages colliding with the central stack (even when using seperatrons) I've changed my SOP to include spinning up my ship just prior to burn out so that the stages are ejected much faster than they would normally be. This only works because MechJeb's ascent autopilot can hold a heading (and steer) in a rotating reference frame and does not restrict manual axial rotation like ASAS does.

This has been particularly effective when dumping asparagus stages and SRBs that are still burning after I start my gravity turn, which historically has been a serious (and very explody) problem for me. It's actually to the point where I find seperatrons more useful as aids in spinning up the ship prior to staging than as separation motors.

This is the ship that forced me to start doing this. 12 Jool V SRBs firing in two tiers with 4 asparagus'd orange tanks all surrounding a central stack.

[lobsterbark]

Wait, why are you so high up, and still have so much rocket left?

[Panichio]

It's been something I've tried before, but with no success. For me, the sepratrons were enough, but good to see this does actually work.

[Brotoro]

Some of my rockets sometimes take it upon themselves to spin around when asparagus staging approaches (but only sometimes). How helpful...but it's a 'helpfulness' I'd rather do without, since sepatrons do the job of getting the boosters away well enough for me.

[The Ideal Gas Lawyer]

Wait, why are you so high up, and still have so much rocket left?

"so much rocket left" is a very relative term. It was significantly larger at launch.

The 8 SRBs that fire at lift-off provide 90% of the thrust for the first 60 seconds and 8-ish km of flight. When I dump those 8, I light 4 more and throttle up the liquid engines (which are still nearly fully fueled). The second group of SRBs is flung out early in the gravity turn and the 4 outer orange tanks are ejected just before my apoapsis reaches 100km. I use the still full center tank to circularize and start my interplanetary injection burn

Edited May 7, 2013 by The Ideal Gas Lawyer
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[SuperFastJellyfish]

Maybe it's your placement of your SRBs in a normal seperatron usage. The way I see it you are trying to get the booster clear from the ship as fast as possible. I usually place two seperatrons on the approximate CoM of the empty booster pointed away from the central core and tilted down 45 degrees. The logic being that downward and outward thrust will get them clear ASAP instead of just pushing them out radially.

[The Ideal Gas Lawyer]

Maybe it's your placement of your SRBs in a normal seperatron usage. The way I see it you are trying to get the booster clear from the ship as fast as possible. I usually place two seperatrons on the approximate CoM of the empty booster pointed away from the central core and tilted down 45 degrees. The logic being that downward and outward thrust will get them clear ASAP instead of just pushing them out radially.

I've tried that with mixed success. It really becomes a problem after you've started your gravity turn, since anything ejected "up" will tend to fall back onto your ship without a significant radial kick. Even more so when the stage to be ejected is very tall as there is a longer period between staging and clearing the aft most engine

Edited May 7, 2013 by The Ideal Gas Lawyer

[paleorob]

I have in the past but don't use it often. I'm more likely to "kick" lose the spent transfer stage engine/tank of my Munar shuttlecraft after arriving at MOSS (Munar Orbital Science Station). Unload fuel into MOSS fuel tank from transfer stage, decouple, shake station to kick the used part free. Next bus down the surface will usually nudge it along into a terminal trajectory before moving clear and descending to my (as-yet unnamed) Mun base.

[Vanamonde]

How hard is it to stop the rotation once you've started it?

[magnemoe]

Has used rotation in deep space never during launch as it make the rocket to hard to control.

[NeoMorph]

You don't need to spin much to give a decent push to the tanks. But even a slight unbalance can cause your ship to wobble off axis and cause more problems than help so I just use sepatrons now. The other alternative is to use SAS but that kills your spin too.

A well thought out sepatron plan will help a lot more than using centripetal spin assist.

[The Destroyer]

That's a monster of a rocket for sutch a small payload.

[Clouds]

Yes, I've done this before, although mostly in earlier versions that lacked so many good part-options for building a rocket that has enough clearance between detached sections.

Furthermore, especially in space, if you use stack decouplers instead of radial ones, the ejected sections won't start rotating at all and you can just thrust away with leisure while they stay harmlessly in place.

A well thought out sepatron plan will help a lot more than using centripetal spin assist.

Those add part-count and mass; leveraging "magic torque" does not.

Granted, I'd given up on trying sepratrons back before they got buffed...

[doggie015]

That's a monster of a rocket for sutch a small payload.

Who said they were going to just LKO?

[Richy teh space man]

I use this technique to throw away spent stages too, after previously losing some stages in orbit and experimenting unsucessfully with the mini rocket seperators. Less weight, less parts, and it works

[FluffyBob]

One of the great things about this game is seeing all the different ways people accomplish things.

It is a kind of cool solution, and Ive had it happen by accident, but haven't really used it on purpose. I find it strange that you have had no luck with sepratrons, they do require a little arrangement to place properly but are simple and effective. Two are enough to clear jumbo + radial stages.

It does seem like a complicated way to do something that there is an existing solution to, but hey its pretty cool too.

[Echostatic]

My most recent experiment uses a few of the tiny SRBs to push the spent stages away. Glad to finally find a use for 'em.

[Moon Goddess]

Who said they were going to just LKO?

That just brings the question of where are they going? Eeloo? Moho? Low Kerbol orbit? Interstellar escape?

[Malachai]

Well, from the name of the rocket, I'd assume the destination is Jool...

[iRommel]

Ive experienced that with one of my heavy payload rockets.

I used I beams attached to the center tank that point out radially, placed in between the outer tanks. no explosions at all, even a few times while mechjeb was mid turn and staging at the same time.

[Dweller_Benthos]

Yeah, I do it now and then, mostly for the "coolness" factor, as it looks good with the spent rockets flying off in all directions. For staging early in the flight I use the sepatrons, but if the rocket still has stages after I'm out of atmo, and the flight is going well enough (read: I have it under control) then I'll give it a little spin and get rid of the empties. It's easy enough to stop the spin afterward as the ship is usually much lighter and has no asparagus stages left, just the central core, and that's easy enough to correct the spin.

[MBobrik]

I've used it on the upper stage of one of my crazier designs where I had no room to place separatrons w/o them frying my central core or cargo. Worked perfectly because it was a ship designed to be extremely maneuverable so I had no problem to spin it up and then kill the rotation one second later.

[The Ideal Gas Lawyer]

That just brings the question of where are they going? Eeloo? Moho? Low Kerbol orbit? Interstellar escape?

Well, from the name of the rocket, I'd assume the destination is Jool...

Jool V is the name of mod were the SRBs came from, the rocket was bound for Moho to investigate the terrain anomalies at the poles. I needed every scrap of dV I could get, especially since that HOME module perched on top is a goram nuclear reactor and therefor quite heavy

More to the point, I started using this technique relatively recently and only after extensive use of sepratrons which, for heavy loads like these XL SRBs, I found to be woefully inadiquate. Even when using 2-4 pairs per booster (and angling them down as has been suggested) I still often had collisions when ejecting stages after the start of my gravity turn. This works much better and as has been previously stated, it does so with lower mass and part count.

[Anglave]

I used rotation to discard the final 'ascent stage' legs after achieving LKO, on the way to my recent Laythe mission.

It was Pebblegarden's 'Take Me to the Moon' video series that gave me the idea.

[UNSA]

I've gotten in such a habit of doing this that all my launch systems now are on detachable 4x pylons. Hardly anything is launched 'on top' of a rocket anymore. Makes for getting some exceptionally large ships in orbit as well. Simply start rotating about 45,000m and release the primary rockets, then onward on internal engines!

UNSA Enterprise Utility Tender