Something weird about DeltaV info, staging and re-rootin assigned control points in the VAB

[JoeSchmuckatelli]

I've got this figured out - so it's not a good post for gameplay questions/tutorials - but I noticed something weird yesterday when I was building a ship.  My 'zero' stage, which had an Octo, a fuel tank and an engine, displayed no Delta V info at all (everything in the stage info, once displayed, was zeroes). 

I'm used to seeing zeroes there because the last stage is usually a parachute - but for this build it was a refueling probe.  And the zeroes freaked me out, because I've spent two days trying to revert to previous saves and eliminate a Kraken-bait ship I built that destroyed (and destroyed and destroyed) my nascent Mun base.  IOW - I feared I had broken the game and was going to have to delete it entirely and start all over again. 

But it turned out that the problem was that I had re-rooted the ship to a lower stage lander* - and the game would not recognize any of the abilities of the stuff above the control point. 

So, the question is - is this by design? 

 

* The end rover, being upside down was messing with the Navball so I re rooted to the lower, upright lander. 

[AHHans]

1 hour ago, JoeSchmuckatelli said:

So, the question is - is this by design? 

Kind of. After a staging event that splits the craft (e.g. firing any kind of decoupler) the calculation computes the dV on the part that contains the root part. How else should the game know for which of the two parts you want the dV calculated? (Or do you want to have the dV of the spent stage that you just dropped shown?)

Edited May 21, 2020 by AHHans

[HvP]

Yes, the game assumes you will be controlling the lander in the lower stage after you have separated from the topmost stage.

And since that lander won't have access to any of the fuel or engines in the top stage after separation it won't add those resources to its calculations.

[JoeSchmuckatelli]

3 hours ago, AHHans said:

Kind of. After a staging event that splits the craft (e.g. firing any kind of decoupler) the calculation computes the dV on the part that contains the root part. How else should the game know for which of the two parts you want the dV calculated? (Or do you want to have the dV of the spent stage that you just dropped shown?)

Just trying to understand the why's = knowledge is powah.  

 

I was reaaaaallly consternated at having to go back to a save more than half-way back from where I had gotten...

Edited May 21, 2020 by JoeSchmuckatelli