Question

Greetings!

I'm building a rocket with radially attached solid fuel boosters that have extra liquid fuel tanks on top. I desire that the solid fuel boosters decouple and leave the liquid fuel tanks attached for later decoupling.

I cannot get both the stack coupler and both radial decouplers to attach all at the same time.

I've tried several methods of constructing it. One method joins the liquid fuel tanks first and tries to attach the boosters to it, and that doesn't seem to work at all - the top join point on the boosters doesn't connect to the bottom join point of the coupler. I can attach both parts separately with radial couplers but if I don't use 2 on the solid booster it wobbles both on the launch pad spawn and in flight. If I do use 2 radials on the solid boosters, they decouple weird and take out my liquid fuel engine at separation. 

If I construct the whole side stack first and then attempt to attach it to the main rocket via the bottom radial coupler, the top coupler doesn't attach and the whole booster/tank assembly wobbles on the one attach point. 

thoughts? ideas?
 

pic:

https://steamcommunity.com/sharedfiles/filedetails/?id=1845395872

 

Share this post


Link to post
Share on other sites

6 answers to this question

Recommended Posts

  • 1
1 minute ago, Rogue Phoenix said:

re: loop of parts - that kinda makes sense - it's a limit of how the game is programmed.

Yes. The parts act like a big tree (as mentioned earlier). If there's a loop, the physics calculations break.

 

2 minutes ago, Rogue Phoenix said:

re: strut near bottom of stack - how does that work with decoupling? won't the strut just hang on to its part?

Nope. They automatically disconnect with no action needed on your part (which is why I prefer it over the auto-strut, which can sometimes have unintended consequences).

 

3 minutes ago, Rogue Phoenix said:

I'm running a mod. Stage Recovery I think.

Cool. Just wanted to make sure (it's a common thing for people to try and get tripped up on). Glad you're already on top of it!

 

Also, welcome to the forums! :D

 

Share this post


Link to post
Share on other sites
  • 1

KSP doesn't work with multiple decouplers on parts.  Only the (in your case) bottom one will attach to the core rocket.  The only way to do something like what you are wanting would be to attach the top liquid tank to a radial decoupler, then the SRB's underneath with an inline decoupler to the LF tanks, then maybe add struts from the SRB to the core for stability.   Alternately, you could figure out how long the SRB's burn for & match the amount of fuel in the liquid tanks to match the SRB burn time & decouple everything together

Share this post


Link to post
Share on other sites
  • 1
Posted (edited)

As mentioned, you can't make a "loop" of directly connected parts.

 

Your particular setup is (in my opinion) best fixed by simply using a strut near the bottom of your engine stack. I personally avoid auto-struts for these situations.

Just ensure that the decoupler's connection point for the liquid engines is in a good spot for the liquid engines to run (so they aren't wobbly by themselves). Then strut near the bottom of the solid booster. (Pics below)

Spoiler

cXwFo0o.png

 

O2PFKQ5.png

 

 

One other thing I see that might be a problem for you. I see some parachutes on your solid boosters which leads me to believe you are planning on separating and recovering them. If you're running without add-ons, you will have a hard time recovering those boosters. The stock game automatically deletes airborne objects below a certain altitude if they are not near your active vessel (the one you are controlling). This is to help reduce the physics burden, but has the side effect of not being able to recover things like boosters with parachutes. If you really want to do this, you either have to stay near the boosters, switch to them and follow them to the ground (which is a problem for your main ship), or use an add-on (there are a couple to chose from).

Edited by Claw

Share this post


Link to post
Share on other sites
  • 0
3 hours ago, Rogue Phoenix said:

ck first and then attempt to attach it to the main rocket via the bottom radial coupler, the top coupler doesn't attach and the whole booster/tank assembly wobbles on the one attach point. 

Are you using Autostruts?They usually help in the wobble part.

Just careful when you use them, there are posts about how its best.(grandparent not heavy).

Share this post


Link to post
Share on other sites
  • 0
Posted (edited)
10 hours ago, Cavscout74 said:

KSP doesn't work with multiple decouplers on parts.

Well, that as such is unclear. (Of course you can e.g. have multiple radial decouplers on your central stage that decouple side boosters.)

What is the case is that a new part is connected to exactly one existing part. And that is so for all kinds of parts. (If you know about programming: each vessel is a tree with the root part being the root of the tree.) So if you already have the liquid fuel tanks connected (via radial decouplers), then you can attach the SRBs either via radial decouplers of their own to the central stage, or you can attach them to the bottom of the liquid fuel tanks, not both.
The not-really-an-exception to this rule are the struts and the fuel lines. They have a parent part (to which they are attached, and where they stay after separation), but they also point to another (usually...) part to do their special thing.

Edited by AHHans
fixed typo

Share this post


Link to post
Share on other sites
  • 0
1 hour ago, Claw said:

As mentioned, you can't make a "loop" of directly connected parts.

Your particular setup is (in my opinion) best fixed by simply using a strut near the bottom of your engine stack... 

One other thing... parachutes...


re: loop of parts - that kinda makes sense - it's a limit of how the game is programmed.

re: strut near bottom of stack - how does that work with decoupling? won't the strut just hang on to its part?

re: parachutes - I'm running a mod. Stage Recovery I think. It calculates a probability of recovering the part based on the projected landing speed with equipped parachutes. If touchdown < 6m/s, recovery is 100%. 
 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.