New to Kerbal. Structural integrity question

[TheAlmightyOS]

Hail fellow Kerbals!

I got hooked on this game at the SXSW LANFest. Since then I have been messing around with it, mostly coming up with absurd and ridiculous rocket designs in sandbox mode just to learn the ins and outs of the editor. Most of my creations ether blow up on the pad or cartwheel out of control after launch which I really don't mind too much. I have never played a game before where failure is so spectacular that it is sometimes more fun than success . I figure once I am confident I can successfully build a rocket to preform like I envision in my head I will start looking into design more seriously. But untill then...CRAZY ROCKETS! My current design challenge that I have set for myself is to build what I have appropriately called The BMFR (Big Mother-#$%ing Rocket). This rocket consists of Rockomax Jumbo-64 Fuel Tank surrounded by 6 more Rockomax Jumbo-64 Fuel Tanks. The 6 outer fuel tanks have two Rockomax BACC Solid Fuel Boosters each on their outward facing sides. Each Fuel Tank has a Rockomax "Mainsail" Liquid Engine under it. On top of the center fuel tank I will be building the rest of the spacecraft, but it is not there yet. When I go to launch it, the BMFR falls apart under it's own weight. I am trying to figure out a way to increase the structural integrity of my flying explosion waiting to happen. Any Hints?

[vidboi]

The part you are looking for is the EAS-4 Strut Connector. It is found under the structural parts tab. Use this knowledge well young Kerbonaut

[Concentric]

By the power of Struts, all things become possible.

But seriously, be sure to use the wide-separating radial decouplers to minimise the chance of part-clipping in the tanks, use struts to give multiple points of connection from each tank to three others, strut your boosters to each other and the tanks, and don't balance it on the engines - support it with launch clamps. The Structural Part tab is nigh-vitally important for structures of reasonable (and unreasonable) size. Struts should also strengthen the link from the bottom launch stage to the upper parts of the spacecraft.

[Xacktar]

By the power of Struts, all things become possible.

AMEN!

Use the struts plus symmetry mode to make 'X' looking reinforcement between parts. Think about where the FORCE is coming in from (mainsails) and how you can spread out that force (struts) over the entire craft as evenly as possible.

Balance is also very important so make sure that your center of weight is as close to center as possible. (There is a button in the VAB which will show this to you.)

Good luck and have fun!

Edited March 12, 2014 by Xacktar

[Scotius]

You mean something like this?

This is Septarch. My standard heavy launcher i'm using since version 0.20 (i think). It can easily wrestle 70+ tons to LKO, but full-sized payload does require extensive strutting to stay in one piece and attached

[TheAlmightyOS]

I thought I was using enough struts but I guess not. Going to use the suggestions here and to go crazy with the struts when I get a chance to mess with my rocket again. Also, I never thought of using decouplers as I didn't intend to separate any of the tanks in flight. But it sounds like a good idea. Maybe I can experiment with this asparagus staging I have been hearing about.

Xacktar, I hope one day I too can make such a spectacular launch explosion as seen in your sig. That is pure awesome sauce.

[TheAlmightyOS]

You mean something like this?

http://i.imgur.com/T3RrIRW.png

This is Septarch. My standard heavy launcher i'm using since version 0.20 (i think). It can easily wrestle 70+ tons to LKO, but full-sized payload does require extensive strutting to stay in one piece and attached

WOW. Yes. Almost exactly (add one more rocket booster per outward facing liquid fuel tank). I guess my design wasn't as insane as I thought it was lol

[Pecan]

..Most of my creations ether blow up on the pad or cartwheel out of control after launch which I really don't mind too much. I have never played a game before where failure is so spectacular that it is sometimes more fun than success ... Any Hints?

Well it sounds like you've got the hang of it all ;-0

Hints:

1) Don't forget the joys of improbable aircraft too; SPH as well as VAB

2) Once you've messed around as much as you like it is worth reading the tutorials on how to make things that work (although an awful lot of stuff seems to be in video form, assuming you can't read and don't have meterd broadband fees)

3) Ships that work or don't are always welcome in these forums so ask whenever you have specific questions

4) It's really fun the first time you a) get to orbit, visit a moon, c) land on one, d) rendezvous and dock (and others)

And more seriously and specifically:

The KER (Kerbal Engineer Redux) or MJ (MechJeb - also an autopilot) mods both show you information you need to know in the VAB in order to make a 'good' rocket (not to say that 'good' doesn't = spectacular explosion). Mainsails and boosters are powerful - often too powerful. Struts will help but too much thrust can tear your ships apart - with hilarious consequences - and wastes fuel when you're, sort of, trying to do it 'right'.

Read about TWR and deltaV ((very) basically how fast and how far a thing can go) enough to understand the figures KER/MJ tell you.

Practice. Have fun. Practice having fun. Have fun practicing.

All of the above.

[cantab]

You definitely want to stage, even "regular" staging will let your rockets go further.

[NecroBones]

WOW. Yes. Almost exactly (add one more rocket booster per outward facing liquid fuel tank). I guess my design wasn't as insane as I thought it was lol

It's become a fairly common design, I think, since nothing really beats orange tanks and mainsails for pure lifting power.

Some main points of advice when building this way, to keep it from blowing up:

1. As others have said, struts. I would put a pair of struts at each of the top and bottom of the tanks, to hold it to the center tank. Wherever you use a fuel-line, remember that it also acts as a strut. To keep the design balanced (and not introduce rotation), treat the fuel-line as a strut, and put a matching strut on the other side. Struts automatically disconnect if they bridge over a decoupler, so don't worry, and just add struts anywhere you need to.

2. As others have said, you can use the more stand-offish radial decouplers to have some breathing room between tanks. You want to use these, and fuel-lines, to do what we call "asparagus staging". The tanks will feed fuel through each other, so that you can drop them in pairs, until you're down to just the final, center tank. The fuel crossfeed lets you drop empty tanks, and have all of the other tanks still full when it happens, but make use of all engines simultaneously. This buys you maybe 5-10% more total acceleration when compared to dumping all 6 of the outer engines at once, while letting them use just their own fuel.

3. Use "Sepratrons". Those tiny little solid-rocket engines are designed for aiding in separating stages. Use those to push your discarded tanks away from your ship, to reduce the chance of it scraping other parts of your ship off.

4. Stitching. This is a method of using struts to strengthen the connection between engines and fuel tanks, or tanks to other tanks, in a vertical stack. Make a strut that starts near the bottom of a fuel tank, and extends straight down into the engine underneath it, and it makes a little "stitch" that helps hold it together.

[Max Grant]

You definitely want to stage, even "regular" staging will let your rockets go further.

Second that. It is fundamental to the success of your rocket to be able to throw away weight.

[NecroBones]

WOW. Yes. Almost exactly (add one more rocket booster per outward facing liquid fuel tank). I guess my design wasn't as insane as I thought it was lol

Oh and also--- just wait until you start putting 19 mainsails in a lifter... lol (OK, actually it was 18, with a skipper in the center.)

[Pecan]

We should also probably mention that it's rarely necessary to lift more than about 40t (orange tube, docking ports, etc) in one launch - once you can dock you can assemble monster ships in orbit. In any case, most missions/destinations don't need nearly as much stuff as you'd expect. Again 'necessary' doesn't mean you won't want to.

[TheAlmightyOS]

Oh and also--- just wait until you start putting 19 mainsails in a lifter... lol (OK, actually it was 18, with a skipper in the center.)

http://ed.toton.org/photos/screenshots/KSP/KSP%202014-02-28%2023-44-06-80.jpg

That sound you heard was my brain exploding.

[NecroBones]

That sound you heard was my brain exploding.

It's not for the feint of heart.

As Pecan mentioned, it's not usually necessary. I'll also add that it's not usually safe either. That ship actually worked, but it had its issues. I built it specifically to avoid having to do a docking maneuver.

[StrandedonEarth]

Welcome to KSP and the forums! Here you will find the greatest collection of cool and helpful dudes and dudettes, and the Kerbals are awesome too! As the others said, launch clamps and struts are your friends, along with those little green guys (they can repair stuff too)

Fuel lines act as struts? I just learned something new!

19 mainsails: check!

30 jumbo tanks: check!

6 LV-N's (nuclear engines): check!

1 land-anywhere lander (getting back to orbit is another matter): Check!

1 green guy in a can: check!

Random RUDs (Rapid Unplanned Disassembly): check!

Being scattered across the landscape: priceless!

[Vanamonde]

Welcome to the game and to the forum, TheAlmightyOS! Pictures of your ship always are helpful when asking others for construction help, and here in the gameplay questions sub-forum (to which I have moved your thread), you will find people happy to look it over and give you advice.

[SRV Ron]

Placing a full orange fuel can in orbit;

Of five at once;

Just requires efficient design and effective bracing for stable controllable flight.