Need help with a craft problem

[aderingflerger]

Meet the Interplanetary Funk:

This is my go-to craft design that I've been using since the science update. I can take it to pretty much any planet I want to. But it has a problem...

This is the stage that puts it into Kerbin orbit. But around 80% of the time at least one of those side tanks will fall off when launching and ruin everything. They can even fall off before I lift off!

I've tried various solutions but nothing works, so I would like some help.

Craft File

My Current Tech tree:

[Skorpychan]

That's a LOT of fuel on that second stage. So much that you need the upper stage to lift it.

For starters, I'd suggest simply eliminating the middle stage and seeing how that works. Do you have fuel lines yet? If so, use onion or even asparagus-style staging.

[Jimbimbibble]

The first thing that I notice about this is that it's way bigger than it needs to be. You can get away with less than half the mass if you are more efficient with how you build, especially on the upper stages. You can reduce your TWR on any stage that is only going to be used in orbit and that will shrink the total launch mass a lot. Go with 1 nuke only for your interplanetary transfer. It will take a while but it's worth it. Also consider using a separate lander so you don't have to put the whole ship down. That will also have a huge effect on your launch mass. If you get the ship small enough a dozen struts will be enough to hold the whole thing together. Consider using Kerbal Engineer to see how much delta V you're getting from each stage. I hope that helps.

[Kasuha]

Too many struts in wrong places. The main culprit are Mainsails and orange tanks at the bottom, the four X200-32 are just displaced by their push. I'll try to upload something better after I get it working.

Edit: here you are, this seems to work better.

You may try to further improve it by disabling gimbal on the eight outer mainsails, the central one might suffice for steering. But it might not be necessary.

Edited February 12, 2014 by Kasuha

[sjwt]

Out side of size issues, your strutting is all wrong.. Triangles is the shape you want for all struts..

I've removed a bucket load of your struts, and replaced them for you.

You where also running struts that elevated vertical stress and horizontal stress in the same set, its good to separate the two (the ones from the orange tanks to the next stage), they are now in two different sets.

I've lined up your 1st and 2nd stages, they were slightly out, and that wasn't helping, a good mod for that is Editor extensions as it allows you to turn on and off vertical snap to get things placed right in the middle, and it also lets you alter the angular snap to off, 1,5,15,30 degrees etc, quite useful for getting things centered.

A slight drooping of your wings to make keep the ship a touch straighter and I've uploaded it for you to give it a try.

https://www.dropbox.com/s/m0kk5shbb94k002/IFM3b.craft

[Nemrav]

I could get away with a way smaller rocket and smaller tech and farm out another planet.

use what I call a "double asparagus" probly pretty easy to guess what I mean

[SRV Ron]

Note the bracing in this somewhat similar design. The payload stage has 1/2 the nukes and eight probes.

Use X bracing on your design. Ditch the fins. One SAS before the payload stage should be sufficient for control. Go with two nukes instead of four. Make the lander a separate unit, preferring a one Kerbal lander. Asparagus the launcher as quad sets. If that doesn't place the core into orbit, you are pushing too much weight.

[aderingflerger]

Wow. I never knew that struts were the problem. I asked this question in another forum and they said I needed a lot more struts.

I was able to get both Kasuha's and sjwt's design into orbit, and I landed the second one on Eeloo! Thank you so much guys.

I'll try to shrink down the size later on.