PSA: Booster Separation

[MalfunctionM1Ke]

Are you tired of spent Boosters crashing into your rocket after Separation?

This might* help you out:

*Success not guaranteed

You could either put sepatrons on your Booster facing inward and damage/heat up your Center stack or you could place them on the Center Stack facing outward

You might say: But hey, this way I am carrying those Sepatrons with me and waste dV.

Yup, thats true. But a burned out Sepatron weighs only 0.0125t and you only need one of them per Booster.

Other designs need two or four of them placed left and right on the Booster.

Some People manage to do it with one the top of the Booster or just above the radial decoupler which would either give spin the Boosters bottom inside or the burn the center Stack.

Er, the dry mass of the sepratron is only half the story - you aren't launching with 'em empty. Plus, they are most likely adding some drag too.

Renegade definetly has a Point about the drag but launching with empty Sepatrons makes no sense in any case.

If you can avoid to use sepatrons, dont use them. Only use them if your Booster are too heavy or misplaced (because reasons) to clear you rocket without damaging it.

--edit--

I found some more Pictures and made them into a GIF

By the way you dont need to cut the thrust during the separation, thats only for visualizing the outward movement a little better.

--end--

Feel free to give it a try.

Make sure you dont have them stick inside the Booster but have them arranged in a way that they blast on the surface of it.

Edited September 19, 2015 by MalfunctionM1Ke

[p1t1o]

Thats a new idea, for me anyways, might test it out later...

Another approach I sometimes use is to forgo sepatrons entirely and add fins: one set of fins, 3-4 around the base of the booster for stability - these are not always necessary and are optional, depending - and a pair of fins just forward of the midpoint, positioned as if they were "wings", so parallel to the core stage surface. This pair of fins is angled in a way to produce lift away from the core. On seperation, the boosters "fly" nicely away.

Obviously won't work if you are seperating at too great a height.

[Stoney3K]

Well, the easiest way is just to stick the Sepatrons on the boosters facing inward (that is actually towards your center stack), and thrust limit them to under 10%. If they're far away from the booster's empty CoG, you can limit them even more.

You only need a small nudge to separate your boosters from the main stack anyway, so youŕe better off with a long-burning sepatron at low thrust.

Also, the Energia way is a good one: Have a few sepatrons on your slanted 2,5m-1,25m adapter or the nose cone, facing retrograde. This will push the boosters in the 'retrograde and out' direction.

[Geher]

Very cool idea.

I had another idea. I was thinking: "Isn't a SRB nothing else than a big sepratron itself?" Now I have some crafts where I seperate the booster just a second before they burn out. That way they leave the rocket in the other direction. Worked fine everytime for me now.

[Renegrade]

Yup, thats true. But a burned out Sepatron weighs only 0.0125t and you only need one of them per Booster.

Other designs need two or four of them placed left and right on the Booster.

Some People manage to do it with one the top of the Booster or just above the radial decoupler which would either give spin the Boosters bottom inside or the burn the center Stack.

Er, the dry mass of the sepratron is only half the story - you aren't launching with 'em empty. Plus, they are most likely adding some drag too.

Anyhow, I try to avoid using them if at all possible. You can get away with not using 'em pretty easily in a vacuum obviously, but you can also often get away without 'em by mounting the booster low on the decoupler (or sliding it down with the linear tool). That way, the impulse from the decoupler pushes the nose of the booster out more than the tail, and the new-aero lifting-body effect catches the side of the booster and flings it away essentially for free. This is of course easiest with user-built liquid fuel boosters, as they tend to be bottom heavy anyhow.

That's also one of the (many) design flaws of the Kerbal X rocket - the decouplers are mounted very low.

Also, the Energia way is a good one: Have a few sepatrons on your slanted 2,5m-1,25m adapter or the nose cone, facing retrograde. This will push the boosters in the 'retrograde and out' direction.

If I do use seps, that's usually what I do..

[moogoob]

I don't often use them any more, but if I do, I'll consider your method. Wouldn't work for the boosters on my Nastybird shuttle though, as I don't want to keep separatrons attached after booster separation for aesthetic reasons.

I also use the "Energia" method, with the separatron attached on the outer edge of the booster's nosecone and pointing up and in.

My most common use for separatrons? Solid-rocket deorbit systems. The Hermit-US upper stage for satellite launches has two pointed retrograde to deorbit the circularization engine and fuel tanks once the satellite gets in position.

[cantab]

Lately I've just been letting the boosters scrape the paintwork if they have to. I tend to have quite a low TWR after booster separation so relative speeds are low, and if I need to I can reduce throttle until they're safely behind me.

[Skorpychan]

The issue with sepratrons is mostly drag, I've found.

My best solution so far is to throttle up hard just before releasing the boosters, so the central stack accelerates away from the boosters before they can move. And to balance the decouplers so the boosters leave evenly, instead of pivoting into the central stack.

[Warzouz]

Strangely, since 1.0 I don't have that problem anymore. I notice that putting the radial decoupler a little above the middle of he booster helps a lot. I used to pur them very low and the booster were blasted the wrong way.

Since 1.0, I never use any separatrons (I used a lot of thelm in 0.9)

[magnemoe]

Strangely, since 1.0 I don't have that problem anymore. I notice that putting the radial decoupler a little above the middle of he booster helps a lot. I used to pur them very low and the booster were blasted the wrong way.

Since 1.0, I never use any separatrons (I used a lot of thelm in 0.9)

The new drag system helps a lot, putting an fin on the boosters tips them out,

[Hotaru]

I tend to put a pair (or several pairs) on each booster, near the top on either side, angled outward (and sometimes forward) so as not to strike the core--like this:

I used to put them on the nose cone facing up, but they did tend to damage the core that way; saw this alternate arrangement on the forums somewhere. Works very smoothly and no chance of heating/damage to the core.

[Foxster]

I'm not using them so much these days either but when I do I find this does the job for me...

[xtoro]

Thats a new idea, for me anyways, might test it out later...

Another approach I sometimes use is to forgo sepatrons entirely and add fins: one set of fins, 3-4 around the base of the booster for stability - these are not always necessary and are optional, depending - and a pair of fins just forward of the midpoint, positioned as if they were "wings", so parallel to the core stage surface. This pair of fins is angled in a way to produce lift away from the core. On seperation, the boosters "fly" nicely away.

Obviously won't work if you are seperating at too great a height.

This. I've been using fins for a while now and it's all I use to separate stages in atmo. Cheap and easy, and no damage. I only use 2 at the top, angled away. Sometimes you can even get away with using only one small fin per booster/tank because it will pull away from the center stack before it goes into a crazy spin.

[Pax Kerbana]

Don't need no separatrons messin up my part count! Keep that finger on the X key, let SRBs flame out and stabilize, kill thrust and stage at same time, hit Ctr and hold until full throttle, coast away.

What hurts isn't a little bump, it's the delta velocity between your stages that cause damage, no different the surface impact speed. Equalize the velocity of craft and last stage, then accelerate away! Haven't used separatrons since 0.90... but I have used fleas...

[Superfluous J]

Interesting idea. If I ever had problems with separating radial stacks, I'd probably give this a try.

But I seem to be one of the lucky ones who doesn't even try that hard and never gets interstack collisions. I thought it was because I used the Stock Bugfix modules but IIRC that particular bug was fixed in 1.0 so we're all playing with the same decouplers now.

[Darth Badie]

This might help a lot! MalfunctionM1Ke thanks for sharing and continue sharing amazing things with us !

[mikegarrison]

Ever put just one separatron on, in the usual position? The boosters go spinning off in a very entertaining manner.

[flintlockmusket]

If I'm using SRB's, then I use a drogue chute placed on the empty CG of the SRB, if liquid boosters, seps firing upward and slightly in, and drogues slightly below the empty CG. My boosters get dropped at around 10km.

[MalfunctionM1Ke]

This might help a lot! MalfunctionM1Ke thanks for sharing and continue sharing amazing things with us !

Thank you, Badie.

I like it when a thread develope's into a discussion about the pro's and con's of different methods. Everyone can learn from it and try out new things, especially me

[Goddess Bhavani]

I don't use sepatrons, I just offset the boosters so the decoupler is above the empty booster CoM. This way the separation force will peel them outwards like a banana skin and aerodynamic forces do the rest.

Banana peel staging?

[TMS]

Sep motor on the booster's dry CoM is my standard practice. Stops the booster tail end from spinning into your centre stack engine.

[MalfunctionM1Ke]

Nevermind - see GIF on the first post.

Edited September 18, 2015 by MalfunctionM1Ke

[mielgato]

I don't use sepatrons, I just offset the boosters so the decoupler is above the empty booster CoM. This way the separation force will peel them outwards like a banana skin and aerodynamic forces do the rest.

Banana peel staging?

i'm doing the "banana peel staging" as well, most cost/fuel/mass efficient technique you'll find.

[sgt_flyer]

Well, i like to put my separatrons (or the small 1.25m SRB for ultra heavy boosters) downwards facing on the boosters - but offcentered from the boosters COM, nearest to the core stage. Upon separation, the offcentered thrust will both 'turn' the booster outward and push it away from the core stage.

[Red Iron Crown]

I don't use sepatrons, I just offset the boosters so the decoupler is above the empty booster CoM. This way the separation force will peel them outwards like a banana skin and aerodynamic forces do the rest.

Banana peel staging?

This is the technique I use most often. Usually doesn't even need offsetting for liquid boosters as the heavy engine at the bottom ensures the CoM is below the decoupler anyway.