How do i get more space between boosters and main stage without it falling apart?

[Turvok]

So i tried to do the thing using tail fins to add more rockets to my launcher and boosters with a higher ISP then mainsail. I ran into a bit of a snag though as i needed extra spacing for everything to have enough room. I used a TT-70 radial decoupler with a modular girder segment on the outside then tried to strut the crap out of everything. Most of the time the launch seems to be going good but i've yet to make it into orbit. One time i'll be going straight up then all of a sudden one of the boosters will break off and start passing me with no warning. Or i'll get to the last stage and start the gravity turn and the torque seems to tear one of the last 2 boosters off. Any advice on how to accomplish this better without everything just falling apart? Also seem to be having issues with the whole craft going in and out of time warp. Just trying to get the timing right to get to jool. Everything goes fine and then i take it out of time warp and everything goes boom. If you need more pics or whatever just let me know.

Edited November 29, 2013 by Turvok

[Smidge204]

So how much mass are you trying to lift into orbit, as a final payload?

'cause when it comes to rockets, less is more. There are diminishing returns with boosters/engines - the more you add the less benefit you get. It's a lot of fun to make stupidly huge rockets with dozens of SRBs but it'll be pure luck if you actually get into space with that.

So my advice is to think a little deeper about what you're trying to accomplish.

=Smidge=

[Turvok]

it's 67 parts and only 51.46 tonnes. not a WHOLE bunch.

I did something similar to this last jool trip. This worked so well with a better ISP then mainsail. (actually a little more thrust too) But not sure why i'm having issues this time.

Edited November 28, 2013 by Turvok

[Smidge204]

Pictures might help, then.

Was the last time you did this before the last update or anything?

=Smidge=

[Sirrobert]

Sounds like you need to put some struts on the boosters. Distance between the rocket and the booster isn't going to save you

On that note: PICTURES. We can't help you improve your rocket if we don't know what it looks like

[Turvok]

no it was yesterday, i just added a couple fuel tanks but reduced my pod from the 3 man down to a 1 man. The other thing i changed was the center gimbling rocket was an LVT-45 and this main one is a poodle. (on each booster and center) Also instead of stack decouplers i'm using stack seperators. one of the tanks on the upper part was getting caught on my LV-N's and not getting left behind, so i figured that would help a bit getting it off the main stage. the stack seperators seem REALLY wobbly, i had to strut a couple of them to keep them from floating around on the launchpad. What more do you want pictures of?

I did manage to get it into orbit finally, but i saved the asparagus area as a sub assembly so want it to work in the future either way. Want some design issues ironed out before i make it my bread and butter so to speak

Edited November 28, 2013 by Turvok

[Turvok]

Can you see the two pictures in my OP? not sure if they are working or broken links or not, they show up for me.

[Sirrobert]

Can you see the two pictures in my OP? not sure if they are working or broken links or not, they show up for me.

Nope, I get a 403 error from it. Try right click the picture and get the actual url of the picture itself. It should end with .jpg or a similar extention

[Turvok]

Try this. ?

[Turvok]

i'm using drop box, and just trying to "share dropbox link" (which copies the link to my clipboard and i can just paste it) maybe i need to find another site to share the pictures.

[Sirrobert]

For some reason the image isn't actually showing, but quoting did reveal the links and they work.

What is your Thrust to Weight ratio? Looks like it has to be MASSIVE. To much thrust is actually a bad thing

[Turvok]

once more.

[Turvok]

There it is the whole ship with engineer redux open. I got around 2.08 TWR for the first stage. On the top voyageur part. the bottom fuel tank i had issues trying to get a fuel crosslink in between. Planned on just transferring the fuel out as i used the other tank and a bit.

[numerobis]

There's not many struts transferring force up the stack -- looks like just one at the top. When the boosters empty their fuel, there's a lot of force leftover to send to the central stack and payload. MOAR STRUTS.

By the way, the first stage would probably be more efficient as a mainsail than as a cluster. Not that this is your issue here.

[Turvok]

There's not many struts transferring force up the stack -- looks like just one at the top. When the boosters empty their fuel, there's a lot of force leftover to send to the central stack and payload. MOAR STRUTS.

By the way, the first stage would probably be more efficient as a mainsail than as a cluster. Not that this is your issue here.

Hmm, 3 at the top, and 4 at the bottom, on each booster. Plus 1 on either side linking the boosters to the other boosters. Plus 4 on each girder segment to the main stack. I thought i was getting excessive. Does the angle that you connect them play a factor in how they transfer the force? ie if it's 90 degress just to the center at the top does that " transfer the force up the stack"? or do i need to stretch them upwards like the top ones do up above the seperator?

on a side note it seems that between the orange tank and the bottom tank where the clusters all sit, that joint seems week. I've had a couple failures there.

I didn't think the craft design was that terrible. But if it takes me 15 launches to get it into orbit once, i must have something drastically wrong.

[mhoram]

Time warp in atmosphere is always a danger, especially for big crafts.

While designing my 180 ton lifter Tangent 18 I had similar problems with the rocket falling apart.

I overcame them by:

- distributing the force of the engines as evenly as possible to the payload

- making the struts as symmetrical and short as possible

- trying to keep the number of struts to a minimum

- testing the positions of the struts

- lots of testing and refinement

- lots of testing and refinement

In addition to the TT-70 radial decouplers I used structural panels for adding space between boosters and core.

The flight log (F3) can tell you which parts get destroyed first which can help you locating the problem zones.

Looking at your pictures, I would

- reduce the number of horizontal struts

- remove the struts between the boosters and the tail connectors

- add struts from the boosters to the LV-N's or their tanks

I like the position of the LV-N's seems to remind me of something

[Turvok]

Time warp in atmosphere is always a danger, especially for big crafts.

In addition to the TT-70 radial decouplers I used structural panels for adding space between boosters and core.

The flight log (F3) can tell you which parts get destroyed first which can help you locating the problem zones.

- add struts from the boosters to the LV-N's or their tanks

I like the position of the LV-N's seems to remind me of something

I'm not sure how u attached the structural panels. Not to mention im not sure i have them yet in career mode.

I've never used the flight log, thanks i'll check it out

Never thought it was necessary to go up to the LV-N's with struts, but i'll try that out too, thanks.

as for the position of the LV-N's I got the idea from a video i watched on youtube, it was either hocgaming or scott manley. I originally tried it with only 2 instead of 4. But i didn't want to burn for over 10 minutes to get the whole thing to Jool system, hence why i went to 4.

[mhoram]

I'm not sure how u attached the structural panels. Not to mention im not sure i have them yet in career mode.

They can be attached to the sides of tanks.

Sorry, but I have no detail-pictures of my rockets - you would have to check out the .craft files.

And the rockets are primarily made for Sandbox mode.

[allmhuran]

It looks like youa re using asparagus staging, yes?

With asparagus staging, the thrust to weight ratio of your radial booster columns becomes extremely high relative to the rest of the craft, particularly the centre stack. Consider: When one set of boosters is almost out of fuel, the column mass is extremely low. But it still has all those engines at the bottom pushing it up, meaning it wants to accelerate really really fast.

Meanwhile, your central column is still very heavy and still only has the same thrust to weight ratio it did at liftoff, meaning it wants to accelerate much more slowly.

You therefore get very large shear forces acting on your radial decouplers, and the outer columns tear off.

One way you can improve your integrity on this rocket is to attach the modular girder to the central column and then the decoupler to the girder, rather than the other way around as you have it now. The decouplers are very flexible, so right now the girder is acting as a lever, magnifying the "wobbliness" of the columns. If you put the girder on first this will be reduced. Yes, this does mean you will have slightly ugly girders left on your central column after ejecting your radial stacks.

Another useful technique is to cross-stitch your radial columns to your central stack with struts. IE, instead of having the strut run horizontally, run a strut from the bottom edge of the radial column up at an angle so that it connects to the centre stack at the same height as the top edge of the radial column. Then put another strut that crosses this one. Then do the same on the other side of the column. This seems to cope with shear stresses much better (which is good, because it would in real life too!)

Finally, if you still have issues, a completely effective solution is to use a thrust plate. See my sig for a video making use of one, or browse my youtube channel to find a tutorial on the technique.

[ddenis]

I'd suggest you to use only 2 LV-N for upper stage and get rid of the second big reaction wheel. It will cut 5t or 10% of your payload.

Oh. You've already tried 2 LV-N.

As a possibility.... You can turn on physical Time Warp when engines are burning, use "Mod + ."

With it you can time warp up to x4, so, even with 2 LV-N you can burn twice as fast as with 4 LV-N without time warping.

Mod + . Physical time warp increase (compulsory)

Mod + , Physical time warp decrease (compulsory)

It's the same warp which you have when landing in atmosphere.

Edited November 29, 2013 by ddenis

[John FX]

You could always throttle down during your gravity turn to reduce the forces as your TWR is higher so you could be at 75% throttle and still get all the push you need.

Just sayin.

EDIT : With engineer does it show your final TWR or your start TWR for each stage? If it is at the start then your TWR could get as high as 4 when your fuel is nearly used leading to unplanned disassembly...

Also examine which struts will vanish when you stage as it could leave your craft strutless, leading to unplanned disassembly. I had a craft, worked lovely until I staged for the gravity burn at which point it just became individual parts and exploded. I figured out I had put a vital strut onto a part that got staged.

Edited November 29, 2013 by John FX

[SRV Ron]

With SRBs, the G force can reach 15+ on some designs at burnout. That will cause parts to disassemble as well as compression failure. It takes creative bracing to prevent such failures.

Asparagus staging has its own challenge in bracing especially when adding a SRB ring. Note, radical decouplers are strong enough for the boosters, but will fail if subjected to twisting forces. This design eliminates those forces, yet has no struts going from the SRB to the liquid fuel cans.

For bracing of the asparagus, You have to be aware of the forces to brace against twisting which will cause handling issues during flight. This bracing design works well for this four pair design of above. The less efficient, but more powerful, liquid fuel engines were staged just prior to orbit.

[numerobis]

Does the angle that you connect them play a factor in how they transfer the force? ie if it's 90 degress just to the center at the top does that " transfer the force up the stack"? or do i need to stretch them upwards like the top ones do up above the seperator?

The angle matters a lot. The two ends of the strut can rotate as if it were a ball socket; a strut is good against tension and compression, but on its own is useless against torsion. So your struts going straight in are providing no resistance against the column flying up; you only have one good strut and two mediocre ones. Make triangles using cross-braces, like on a trestle bridge or a girder.

You have struts to neighboring columns, but you are using asparagus staging; remember that when you drop column A, column B next to it is no longer bracing against column A. So when column B empties out, it only has half the struts that column A did.

[John FX]

The angle matters a lot. The two ends of the strut can rotate as if it were a ball socket; a strut is good against tension and compression, but on its own is useless against torsion. So your struts going straight in are providing no resistance against the column flying up; you only have one good strut and two mediocre ones. Make triangles using cross-braces, like on a trestle bridge or a girder.

You have struts to neighboring columns, but you are using asparagus staging; remember that when you drop column A, column B next to it is no longer bracing against column A. So when column B empties out, it only has half the struts that column A did.

Well you learn something new every day. I didn`t know the ends could rotate. I fix struts so that would not matter but it explains a lot about why some designs twist and others do not.

[DasWarEinBefehl]

There it is the whole ship with engineer redux open. I got around 2.08 TWR for the first stage. On the top voyageur part. the bottom fuel tank i had issues trying to get a fuel crosslink in between. Planned on just transferring the fuel out as i used the other tank and a bit.

Off-topic, but since it's answered: where does one find the Engineer Redux?