[patch] MechJeb doesn't see in-flight docked fuel.
taniwha opened this issue · 5 comments
This is with dev build 69 of 2.0.8.
This may be related to #119 as it does involve fuel lines between radially attached docking ports and the core stack (ie, the stack with the engine). The oddest thing is MechJeb does see the fuel when the same tanks are attached in the VAB.
The orbital delta-v/burn time is the same as the ship core delta-v/burn time rather than that expected for the added tanks.
Note that the ship core has 4x90/110 capacity tanks. Also, in flight, the fuel is drained from the spherical tanks first (as expected).
I am working on an all-stock-parts ship that reproduces the problem, but the fuel lines are being stubborn in that they won't stay attached such that the destination end actually feeds fuel (possible KSP bug?)
Do stock engines pull fuel from across docking ports when crossfeed is enabled? If not, that may be what's tripping up mechjeb. Also, does the ΔV change when you attach an inert weight? It should, and if not that's something that needs fixing.
I'm 99% certain stock engines do indeed draw across docking ports, but you gave me an idea for how to test this with all-stock parts.
Aquilux: thank you for the inspiration. I was able to demonstrate the bug nicely with pure stock+MJ 2.0.9. This verifies that stock engines do see the fuel, but MechJeb does not.
Note that there is a fuel-line hidden inside the decoupler (connecting the pod to the RCS tank).
I got tired of waiting and fixed it myself. It turns out that MechJeb doesn't know anything about docking ports, and the attachment nodes work in only the one direction (which happens to be the opposite of what is needed). The linked patch fixes this without breaking docking ports put together in the VAB/SPH.