Ships fuel up after they are loaded, to prevent breakup on launchpad

[Origim]

Hello all,

I've been having issues with a spacecraft that, for aesthetic purposes, had to thin out at the bottom. When it loaded, the "give" in the decouplers/docking ports would cause a shock load on the fully fueled ship, and it fell apart like candy.

However, I realized.. I could remove all fuel from the upper stage, attach ground tanks that get decoupled before launch, and fuel AFTER the ship loads... this dramatically reduces shock load, see image below. It does not break apart at all with this set up.

What I propose, is that ships "receive" fuel gradually, over 3 seconds, after they are loaded. This should reduce the springy shock load action immediately after load (root cause is that the ships load with "nominal" spring height, and after physics activate, they seek a new equilibrium, which puts a large shock load on the ship).

http://steamcommunity.com/sharedfiles/filedetails/?id=238708512

Edited March 15, 2014 by sjwt

[sjwt]

You seem to have build a real beast of a ship, belive it or not, KSP does have issues with overly non-realitic ships like that..

You could upload your craft file somewhere and advise what mods if any you have used and someone might be able to restrut/alter your ship so that it works.

[dazhat]

You seem to have build a real beast of a ship, belive it or not, KSP does have issues with overly non-realitic ships like that..

You could upload your craft file somewhere and advise what mods if any you have used and someone might be able to restrut/alter your ship so that it works.

This issue exists with realistic large ships too. I think it is a good idea.

[Sirrobert]

It would be a nice option for the overly huge ships yes.

Probably nice to add some special part (a variation of the launch clamp), a fuel tower, as a requirement for this. This would add a nice extra cost to these ships once money is implented

[Kasuha]

I think it would suffice if gravity was turned on gradually for the ship similarly how air pressure is turned on during about the first second. No refuelling needed and it would work for parts which are heavy without containing anything refillable.

[Red Iron Crown]

I like Kasuha's idea, it's the sudden kick of gravity that is the root cause of the problem.

[Kermunist]

A potentially easier to implement option, which would achieve the same end result, would be to set unbreakable joints and parts on for the first few seconds. Turn it off again just before the player takes control.

[Superfluous J]

I like both of these ideas. Kashua's is more of a generic fix though so it's preferable. What if you have lots of monoprop? Or just something really heavy and non-fuel?

One thing you can do is make your own "launch towers" that aren't attached to the ship itself (attach them to the red support thingys) and just run a ton of struts from your tower to all your dangly bits. If you start the struts on your tower, when you launch you won't have any extra parts on the ship and will leave them behind on the pad. I think, depending on your setup, that you can even just run struts from the red supports to your ship. Helps a ton and only increases part count at liftoff.

But yeah, real rockets don't have to deal with going from 0g to 1g in 0.00 seconds, our "unrealistic" ones shouldn't have to either.

[Fel]

I think it would suffice if gravity was turned on gradually for the ship similarly how air pressure is turned on during about the first second. No refuelling needed and it would work for parts which are heavy without containing anything refillable.

Conventional design (My conventional design) would have most of the weight at the bottom of the rocket and more "Fixed Weight" at the top (science, lifesupport, batteries, idk). By removing the fuel the rocket becomes top heavy and hence could crash down. Other designs have fuel moving around like crazy, I guess that filling via % rather than a flatrate would fix that, however.

The issue is that the rocket begins with "Everything Weighs 0g" and has to survive the impulse of "GRAVITY WAS DISCOVERED! KERBALS FALL DOWN IN JOY"

A potentially easier to implement option, which would achieve the same end result, would be to set unbreakable joints and parts on for the first few seconds. Turn it off again just before the player takes control.

I'm hesitant to say that there is a large amount of energy being stored in those "unbreakable joints" which can rebound back... but once at steady state you do reach the same results (technically) as slowly turning on gravity. (I don't know, I seem to recall breaking an unbreakable joint before). Really though, it shouldn't be too difficult to add that in.